if someone believes that a car needn't be designed to run strictly on premium fuel they are entitled to make that argument.
And so are others to provide a logical argument that the belief might be false. Why do you take offense to it? Even if you do, try not to moderate these threads, we've got moderators for it. I'm sure they have been reading all the discussions.
To keep things civil, you will have to let go of your arrogance, and avoid taking peoples' arguments (mine and others as is apparent above) to heart.
And as I advised you earlier, if you see something isn't civil and is offensive (no need to get fancy with words, especially using cover ups like "respectfully" "non-malicious" because we know better)... seek moderator help. I might, if you continue your ways.
This seems to be getting a little petty. We should be trying to help each other. There is nothing wrong with the comments that doctorw made and I totally agree with them. If somebody wants to explain to me why using regular gas is not a good idea in a vehicle that requires premium fuel, I have no problem with that. But I totally object to the value judgments that some people are placing on others with comments such as 'If you can't afford premium, you shouldn't be buying an Acura'. That is just plain wrong. There is nothing wrong with somebody wishing that Acura made a premium car that requires regular fuel.
Also, not everyone is wanting to buy an RDX because of the sporty performance of it. I could care less about the HP and torque but I plan to purchase one because of the luxury interior that I cannot find in any other vehicle. I am also looking for a car that gets great gas mileage since I have a long commute. The requirement of premium fuel somehow defeats that goal. All we are saying is that value judgements on how people spend their money should be avoided.
I guess kyfdx was right in assuming that the choice between premium and regular is more emotional than fiscal.
Tell me exactly why you dislike premium gas as opposed to regular? Or perhaps, why do you want Acura to recommend regular gasoline as opposed to premium on RDX?
Answer to these questions will be a good starting point to any meaningful discussion. I know you touched on it a bit and sounds like a “value” argument there, but I want to see stated properly so we don’t “misjudge”. Until then it is purely personal attack and I will take offense to it just as much as the other guy.
Realistically, I see no other way around RDX, but to see it recommended with premium.
BTW, “'If you can't afford premium, you shouldn't be buying an Acura” was not my comment. Why would you bring it up in my response?
I didn't say it was your response. Sorry if you thought that. I just have seen several comments like that - definitely in other RDX forums. I have been reading all the RDX forums since this vehicle was announced and definitely plan to purchase one. This will be the first time I am buying a vehicle that requires premium fuel. Based on some comments I've read, it is probably best to use the premium fuel and I plan to. I simply would prefer that it did not. This is based mainly on the number of miles I drive each year and the huge difference in price between regular and premium fuel in my area. It has nothing to do with whether or not I can afford the vehicle or the gas - just that I don't see the benefit of using premium vs regular. It's that simple. I cannot perceive any increased value in one over the other. Unlike when you buy an Acura vs a Honda, you can see the differences in quality and you're willing to pay more. I am not speaking for anybody else, those are just my thoughts.
Please, at least try to read my posts before responding. What I said was that your first post did not address anything other than your belief that a person should not be bothered by having to pay more for premium gas. Lets not lose sight of the fact that your first post was an attack on people's values, not a white paper on the merits of premium fuel for high compression engines. Your argument had nothing to do with why the car needed to run on premium. Additionally, your argument was not logical at all, just because you use numbers does not make it logical. In the end it was about your values versus others.
In fact, until the last sentence of your first post I had no problem with what you were saying. If you had merely concluded your post by saying "For me that is not a large enough deterrent to buying this car," we could have avoided this entire discussion.
Secondly, I am not attempting to moderate this forum, I am merely stating my opinion on your post. I suggest if you are bothered by my post your should either: a.) recognize that I was only criticizing your post and its contents/style not you as a person, or b.) realize that your words have an impact on others and act accordingly.
Furthermore, I was trying to be respectful in the first post and tell you that others might find it offensive, both in tone and content. If you do not wish to take that in the constructive manner in which it was meant that is your business, but please do not attempt to read more into my comments. I am perfectly capable of saying what I mean in a clear and unambiguous manner (sorry to use another fancy word).
You may go to the moderator if you like, but nothing I have said has been mean spirited or uncivil in any way. I found nothing in your first post to that effect either, which is why I chose to address you directly in a civil manner.
If I offended you then I sincerely apologize, I should not have gotten into personal statements such as the school child analogy. That was inappropriate and I am sorry. I only wished to point out that your last sentence was unnecessary and potentially bothersome to others. I was then, and am now, merely suggesting that we stick to fact based arguments in this forum. Please consider what I have said and lets stop this discussion and get back to discussing the merits of the RDX.
This will be the first time I am buying a vehicle that requires premium fuel. Based on some comments I've read, it is probably best to use the premium fuel and I plan to. I simply would prefer that it did not
And I'm with you on that. Given a choice, I would prefer to use regular myself. Last time I did use premium was when I had my Prelude. I tried using premium in my Accord to see if there was any difference, instead I saw the mileage drop a little... so have stuck with regular since (Accord is of course recommended with regular).
But, if I buy an RDX, the first concern I would have is its performance and features that attract me to it, and with good mileage. If Acura recommends premium, I wouldn't think twice about questioning their authority, and certainly not on the ground that premium costs too much.
Now too many years ago when the gas pedal was directly connected to the throttle butterfly valve and good, inexpensive and highly sensitive, knock/ping sensors were not commonplace this octane discussion would have had validity.
Most modern day vehicles have DBW, e-throttle systems and knock/ping sensors have been installed on new engines for at least the past ten years.
Yes, the dealers, and possibly the marketing types at the factory, will "recommend" the use of premium fuel. But I can assure you that absolutely no damage will result from the use of regular fuel in any vehicle so equipped.
I significantly doubt we'd see any damage from using a non-premium grade used in the RDX (always a possibility, but highly doubtful).
My take is... if you don't use premium, you aren't going to get the same performance. In my mind (not speaking for anyone else), that defeats the purpose of buying a performance SUV.
If you're doing it to save money, that's fine. But the savings will be pretty insignificant. And you may not save anything at all. I know several MDX owners who started using regular grade instead of premium. The gas cost less, but their mileage decreased. Net result: the gas was cheaper, but they used more of it.
Now, I'm actually interested in testing this myself. I'm pretty anal about tracking mileage. (I've got 7 years of data for my old CR-V.) It'll take me more than a year due to seasonal variations here in the NE, but I plan to switch and see what happens with my MDX.
First, the primary difference between premium fuel and regular is the burn rate, the rate of propagation of the flame front once the air/fuel mixture is ignited.
Two of the primary objects of modern day engine control systems is to prevent engine damage due to knock/ping while at the same time optimising fuel economy. Both without exceeding the allowable emissions levels.
TDC, or near TDC, knock can be prevented by retarding the ignition timing or at high performance levels, WOT, reducing the total air/fuel "charge" going into the cylinder on the intake stroke.
Since premium fuels have a slower moving, expanding flamefront (they explode more slowly), the ignition timing can be advanced over where it might be for a lower octane fuel. Lower octane fuels require retarded timing, so what?
Obviously premium fuels will also be less subject to pre-ignition, dieseling. But in either case, premium or regular, dieseling may occur for other reasons, a hot day, hot incoming airflow....
In the past this was often overcome by simply enriching the mixture, providing cooling to the cyclinder charge via more "cool" fuel.
Nowadays with the advent of DBW the engine ECU controls the throttle opening and therefore can restrict the cyclinder charge VOLUME and eliminate pre-ignition due to the dieseling effect.
So what about knock/ping due to engine lugging. Again, for modern day systems it the job of the engine/transmission ECU to monitor the knock/ping sensors and thereby prevent the transmission from operating in a gear that would result in lugging, engine knock/ping resulting from fuel octane, regardless of premium vs regular.
Not much different than a driver of a stick-shift would do.
Obviously performance is only an issue when operating with a WOT, Wide Open Throttle.
So what are the benefits of Premium vs regular?
A higher level of HP/torque at WOT and high engine RPM.
A wider lower range of engine RPM without knock/ping due to lugging.
Fuel economy...
Goes to regular fuel.
Have you noticed that diesel fuel on a unit measure basis now costs more than gasoline? Less refining cost/effort/level and less waste, castoff "material" and yet more costly?
It's called VALUE pricing.
A gallon of diesel fuel contains substantially more latent energy than a gallon of gasoline.
As does a gallon of 87 octane of gasoline over a gallon of 92 octane.
Absent trying to attain maximum HP/torque a gallon of 87 octane will get you farther down the road than would a gallon of 92 octane.
It's a turbo, the ECU would probably dial back the boost and retard the timing, but then it will perform like a CR-V, so just get a CR-V in the first place and save yourself $10 grand.
Juice, you're not supposed to tell people what they should do.
Yup... CR-V would be it for those who want a vehicle with regular, even though it will be less of a performer than RDX, and with fewer std features. And cheaper too.
Does any currently offered turbo charged engine work "alright" with regular grade gasoline?
The SE model is probably close to the equipment level on a base Acura, and still a lot cheaper.
I bet some of the light pressure turbos would run on Regular, but I still would not recommend it.
I have a '93 Miata, the timing is set manually on those. I advanced the timing slightly, stock is 10 degrees before TDC, I went to 14. With premium fuel you can go to 18.
Any how, if I lug the engine, use too low a gear on an uphill, the engine will ping. You gotta be careful, basically.
I'm sure modern ECUs will just retard the timing automatically, probably even dial back the boost, but then why get a turbo engine? You probably upgraded for the performance in the first place, I'd imagine.
Add to that the recent history of Mazda's 2.3l turbo mill's issues with heat soak (and significant power loss), and some EVO owners complaining that they cannot find 93 octane in some places, and you can pretty much conclude a turbo is best off with the highest octane you can get.
Both of these can be a lot more efficient at compressing the air volume than the engine itself during the compression stroke. So if the intercooler brings the now compressed (and thereby heated) air charge temperature back down to a somewhat reasonable level a small engine with SC or turbo can be more efficient at producing a given level of HP than it BIGGER brother.
And again, with DBW throttling 87 vs 92 octane make no difference except at PEAK Performance.
And unless you're a really avid "boy-racer" how often would you WOT an SUV all the way to redline?
Well, in an SUV you have a new definition for "performance"...
Like hauling that extra weight around even when you commute alone. Or packing it up with kids and gear and making it up those 3000 ft elevation climbs. Carrying your lifestyle gear (bikes/kayaks) around on weeekends.
I suspect there will be plenty of times where you use full throttle, at least once per tankfull.
And it's not just at ultra-high rpms, in fact my Miata pings at LOW rpms, not high.
Edit: my point is it's all about engine load, not rpm or even just throttle position. SUVs always carry more load.
First, I'm guessing your Miata pings at low RPM for one of the two following reasons.
1. It's a manual transmission and the driver hasn't yet learned how to "operate", stir, the gearbox so as not to operate the engine below the power curve. Assuming this one is valid than stop lugging the engine, that can cause real damage in the long term.
2. Assuming its an automatic the engine/transmission control ECU has no indication of engine knock/ping. Therefore hasn't a clue that it's in too high a gear ratio for the current circumstances.
With e-throttle and regular octane, SUV, whatever, you are free to go WOT anytime you wish, all you want too.
Well, not really.
You can depress the footfeed as hard as you wish, but as the engine approaches redline if the ECU senses any level of knock/ping, detonation, resulting from moving the throttle valve wide open in response to your input then it will start closing the throttle valve to reduce the "charge" going into the cyclinders assuming it has already reached the maximum fuel/air enrichment level.
As I mentioned above, that happens when I'm in the wrong gear. I have a steep driveway and have to climb in first, if I forget and leave it in 2nd it'll ping.
My fault, absolutely, but it was an example meant to show that under load the engine is stressed more, even at low rpm and not at WOT.
The engine is subject to damage from "detonation" anytime the piston cannot move downward fast enough to "accomodate" the rapidly expanding flame front of the mixture once ignited.
That can occur due to "pre-ignition" caused by ignition mistiming, hot spots due to things like carbon debris, or dieseling, wherein the mixture self ignites due to the heat of compression. All of these have the ability to begin the flame front "spread" even before the piston reaches TDC.
But none of the above pre-ignition conditions need occur to have knock/ping occur due to engine lugging.
What is the big deal for fuel? Who cares whether somebody thinks the RDX should run on regular or not. It doesn't matter. What matters is what Acura recommends you run it on. I have a CL-S and have only ever used premium fuel in it since I've had it. Not once have I used regular. I don't complain about the price difference. I get great power, great performance (for a front-wheet drive car), and absolutely excellent fuel economy for a 260hp engine (regularly get 25/26 mpg on a full tank and 32/33 mpg on the highway). If Acura says to use 91 octane or higher, just use it. If you are that strapped for cash (i.e. the extra $0.20/gallon @ about 50 gallons / month = $10/month) than you shouldn't be worried about gas... you should be worried about making your monthly payment, your monthly insurance payment, and any maintenance on the vehicle. If that $10/month is going to kill you, then by all means get the cheaper gas, but don't expect to get the kind of numbers quoted for the RDX as those are based on the recommended fuel.
Would anyone comment a bit on the RDX and RAV4 4WD system? :confuse:
Test drove the new 6 cylinders RAV4 recently and was somewhat disappointed as with its 269 hp engine I found it was too powerful to modulate for smooth ride within the city, power just surged in when slightly touched on the gas pedal. When I tried to merge into the highway traffic the car was abruptly jerked to the left when I put on a little bit more gas and the road condition was nice and dry; guess it may due to basically a front-wheel drive vehicle and the Power-weight ratio may not be too balanced.
RDX's 4WD system appears to be impressive on paper and it may be even good for high speed performance. But what about it's outward rear wheels torque-shift feature? Will that cause any safety issues when driving on slipery road surface even with the ABS brakes and Stability control?
Does RDX have the All-time 4WD system? How does that compare to Subaru's 4WD system? ( I heard Sub has the best All-time drive system for non-off-road driving).
RDX is going to use SH-AWD from RL. If it is an “as-is” adoption, it will be a full time (permanent) 4WD system with 70-30 split during straight line cruising. Anytime throttle input is detected, more power is transferred to rear wheels (it does not wait for slippage to occur). This applies to standing starts too. The SH-AWD can send up to 70% of the total power to the rear wheels (and 100% of it to just one wheel during cornering). The split is also seamless (or, “continuously variable” as opposed to “steps”).
Getting 70% of total power available to just one wheel and with the “acceleration device” (which speeds up the inside wheel by up to 5%) is designed to rotate the vehicle under throttle and during cornering. This will ensure better traction and stability. And of course, like all Honda/Acura light trucks (except base Element, IIRC), stability assist with traction control (“VSA”) is still going to be standard.
The RAV4 uses a system that is sorta like Honda's VTM-4 which is found in the Pilot and Ridgeline. It doesn't have all the featues, but the basic operation is similar. Electronic sensors detect slippage and an electromagnetic coupling hooks up the rear wheels. I believe the RAV4s even have a lock button for low speed use. That is where the similarities end, though. VTM-4 has a few other features not found in the RAV4.
Subaru's various AWD designs are also very good. Unlike the RAV4, they are not reactive. With the most common variant, some torque (approx. 10%) is always being sent to the rear wheels. Like SH-AWD, it can progressively distribute torque from front to rear. It has a wider range of distribution going fore and aft, but there is no side to side movement. So handling is not improved as significantly.
Sounds like you observed an abrupt throttle pedal and perhaps even some torque steer.
I can't comment on how Acura will tune its throttle pedal (more linear perhaps?) but I do expect a more advanced AWD system to effectively reduce that feeing of torque steer you noticed.
You must have pretty keen senses, as a lot of people would not even notice the subtle differences. Good for you.
Methinks torque stear will be non-existent in the SH-AWD systems. The whole idea of SH-AWD is to remove engine torque, stop "driving", the front wheels while turning when it might be that you want the ENTIRE front roadbed adhesion coefficient to be dedicated to lateral, directional control.
In that way Acura, and some other marques, are now over-coming the unsafe, or even hazardous charactoristics, that typically arise from FWD, driving only the front wheels, or the numerous AWD systems that are always front torque biased.
FWD torque stear is most noticeable with lots of throttle or turning tightly and cannot be missed or avoided during tight turns w/WOT.
In those circumstances the SH-AWD system will dynamically allocate engine torque primarily to the rear wheels and therefore that will be very little halfshaft "wind-up" difference between the short halfshaft and the long one.
I expect what the RAV4 needs is a sensor to detect throttle input. SH-AWD and VTM-4 both have one. When the throttle is depressed, the system will route torque to the rear wheels in proportion to the amount of throttle input.
The idea behind this is to prevent slippage before it happens. But it also prevents torque steer.
If I'm not mistaken, Subaru's system (for the automatics) starts the car out in a 50/50 power split. Whenever it's in 1st or 2nd gear, it proportions torque equally fore and aft. That essentially eliminates torque steer and the risk of slippage, as well. Of course, they use a longitudinal engine layout. Without unequal half-shafts torque steer isn't a problem to begin with.
Car & Driver, in their full test of the RAV4 V6, also commented that the throttle was jumpy off idle. I would think Toyota should be able to re-program it to be more docile.
Seriously Toyota, how hard would it have been, with a major redesign already, to switch the rear door hinge side? Oh, you must sell more of these in RHD countries... NOT! :confuse:
Someone has just commented 100% torque can be transferred to outside read wheel during cornering, would there be any concerns when riding on snow-covered /icy roads?
No. The maximum torque that would be transferred to the rear wheels would be 70% of the total (30% of the total would still be sent to the front wheels). And if you're cornering under full throttle, the inside rear wheel gets nothing (becomes a "dummy" wheel) and all power from the rear axle is sent to the outer wheel that has more traction.
This scenario is unlikely to happen since people won't push it that way under poor weather/road conditions. And even if they do, the system would have maximized traction anyway (the inside wheels don't do much to put the power down properly during cornering).
And if there is a side slip detection... RDX will have stability control standard.
VTM-4 is Honda's electro-mechanical AWD system, currently used in MDX, Pilot and Ridgeline. VTM stands for Variable Torque Management.
SH-AWD (used in RL and to be used in RDX) is an advanced version of VTM-4 with a few additional features.
WOT implies wide open throttle.
Front or Rear Torque bias is about how much torque (or power) is being sent to front or rear axle compared to the rear or front axle respectively. For example, under normal cruising, SH-AWD would send 70% of the power to the front wheels and remaining 30% to the rear wheels. So, at this point, it will be a front bias system.
When you attempt to accelerate in a straight line so that now the system send 60% of the maximum torque to the rear wheels (remaining 40% to the front), it would become a rear-bias system.
Without any previous experience with Super-charged 4 bangers, I tend to feel more comfortable with a V-6 motor for all around driving (please correct me if I am wrong)and there was a rumour Honda may come up with a V-6 CRV also as a 2007 model with the SH-AWD system, does anyone know that's quite likely the case?
I would recommend that you take a test drive in some other turbo-charged vehicles if the performance aspect is a concern. A good idea would be to test drive a turbo-powered Subaru Outback, then do a back to back test drive in an H6 Outback.
As for the rumors about a V6 CR-V, those are just rumors. Nobody knows anything reliable at this point. I can say that I doubt very much it will get the SH-AWD system. That system will likely stay an Acura-only feature for a few years. Instead, the CR-V may receive a version of the VTM-4 system.
The SH-AWD system now only allocates the majority of the engine torque to the rear during hard acceleration, is also does that while turning.
While turning, especially tightly and/or under moderate or heavy power, it can be really important that the front tires roadbed adhesion coefficient be dedicated to lateral, direction control, not engine leading or lagging torque.
That's one of major shortcomings of FWD or front biased AWD.
I would really prefer a sport wagon from Acura but the RDX might do. However, I'm hoping it won't have as much ground clearance as most of the smaller SUVs. For example, I would favor a Legacy GT wagon over an Outback for this reason. Does anyone know how high off the ground the RDX will be? Thanks.
Honda has aimed for about 8" with most of their crossovers and the truck. The only exception is the Element, which has about 7". Somewhere in between those figures is as good a guess as any.
Why wouldn't you want more ground clearance? IMO, any SUV/SAV or that ilk is better served with increased ground clearance. I wouldn't want the thing to turn into an expensive snowplow when the white stuff piles up! :sick:
Comments
And so are others to provide a logical argument that the belief might be false. Why do you take offense to it? Even if you do, try not to moderate these threads, we've got moderators for it. I'm sure they have been reading all the discussions.
To keep things civil, you will have to let go of your arrogance, and avoid taking peoples' arguments (mine and others as is apparent above) to heart.
And as I advised you earlier, if you see something isn't civil and is offensive (no need to get fancy with words, especially using cover ups like "respectfully" "non-malicious" because we know better)... seek moderator help. I might, if you continue your ways.
If somebody wants to explain to me why using regular gas is not a good idea in a vehicle that requires premium fuel, I have no problem with that. But I totally object to the value judgments that some people are placing on others with comments such as 'If you can't afford premium, you shouldn't be buying an Acura'. That is just plain wrong. There is nothing wrong with somebody wishing that Acura made a premium car that requires regular fuel.
Also, not everyone is wanting to buy an RDX because of the sporty performance of it. I could care less about the HP and torque but I plan to purchase one because of the luxury interior that I cannot find in any other vehicle. I am also looking for a car that gets great gas mileage since I have a long commute. The requirement of premium fuel somehow defeats that goal.
All we are saying is that value judgements on how people spend their money should be avoided.
Tell me exactly why you dislike premium gas as opposed to regular? Or perhaps, why do you want Acura to recommend regular gasoline as opposed to premium on RDX?
Answer to these questions will be a good starting point to any meaningful discussion. I know you touched on it a bit and sounds like a “value” argument there, but I want to see stated properly so we don’t “misjudge”. Until then it is purely personal attack and I will take offense to it just as much as the other guy.
Realistically, I see no other way around RDX, but to see it recommended with premium.
BTW, “'If you can't afford premium, you shouldn't be buying an Acura” was not my comment. Why would you bring it up in my response?
I have been reading all the RDX forums since this vehicle was announced and definitely plan to purchase one. This will be the first time I am buying a vehicle that requires premium fuel. Based on some comments I've read, it is probably best to use the premium fuel and I plan to. I simply would prefer that it did not. This is based mainly on the number of miles I drive each year and the huge difference in price between regular and premium fuel in my area. It has nothing to do with whether or not I can afford the vehicle or the gas - just that I don't see the benefit of using premium vs regular. It's that simple. I cannot perceive any increased value in one over the other. Unlike when you buy an Acura vs a Honda, you can see the differences in quality and you're willing to pay more. I am not speaking for anybody else, those are just my thoughts.
In fact, until the last sentence of your first post I had no problem with what you were saying. If you had merely concluded your post by saying "For me that is not a large enough deterrent to buying this car," we could have avoided this entire discussion.
Secondly, I am not attempting to moderate this forum, I am merely stating my opinion on your post. I suggest if you are bothered by my post your should either: a.) recognize that I was only criticizing your post and its contents/style not you as a person, or b.) realize that your words have an impact on others and act accordingly.
Furthermore, I was trying to be respectful in the first post and tell you that others might find it offensive, both in tone and content. If you do not wish to take that in the constructive manner in which it was meant that is your business, but please do not attempt to read more into my comments. I am perfectly capable of saying what I mean in a clear and unambiguous manner (sorry to use another fancy word).
You may go to the moderator if you like, but nothing I have said has been mean spirited or uncivil in any way. I found nothing in your first post to that effect either, which is why I chose to address you directly in a civil manner.
If I offended you then I sincerely apologize, I should not have gotten into personal statements such as the school child analogy. That was inappropriate and I am sorry. I only wished to point out that your last sentence was unnecessary and potentially bothersome to others. I was then, and am now, merely suggesting that we stick to fact based arguments in this forum. Please consider what I have said and lets stop this discussion and get back to discussing the merits of the RDX.
And I'm with you on that. Given a choice, I would prefer to use regular myself. Last time I did use premium was when I had my Prelude. I tried using premium in my Accord to see if there was any difference, instead I saw the mileage drop a little... so have stuck with regular since (Accord is of course recommended with regular).
But, if I buy an RDX, the first concern I would have is its performance and features that attract me to it, and with good mileage. If Acura recommends premium, I wouldn't think twice about questioning their authority, and certainly not on the ground that premium costs too much.
Most modern day vehicles have DBW, e-throttle systems and knock/ping sensors have been installed on new engines for at least the past ten years.
Yes, the dealers, and possibly the marketing types at the factory, will "recommend" the use of premium fuel. But I can assure you that absolutely no damage will result from the use of regular fuel in any vehicle so equipped.
My take is... if you don't use premium, you aren't going to get the same performance. In my mind (not speaking for anyone else), that defeats the purpose of buying a performance SUV.
If you're doing it to save money, that's fine. But the savings will be pretty insignificant. And you may not save anything at all. I know several MDX owners who started using regular grade instead of premium. The gas cost less, but their mileage decreased. Net result: the gas was cheaper, but they used more of it.
Now, I'm actually interested in testing this myself. I'm pretty anal about tracking mileage. (I've got 7 years of data for my old CR-V.) It'll take me more than a year due to seasonal variations here in the NE, but I plan to switch and see what happens with my MDX.
First, the primary difference between premium fuel and regular is the burn rate, the rate of propagation of the flame front once the air/fuel mixture is ignited.
Two of the primary objects of modern day engine control systems is to prevent engine damage due to knock/ping while at the same time optimising fuel economy. Both without exceeding the allowable emissions levels.
TDC, or near TDC, knock can be prevented by retarding the ignition timing or at high performance levels, WOT, reducing the total air/fuel "charge" going into the cylinder on the intake stroke.
Since premium fuels have a slower moving, expanding flamefront (they explode more slowly), the ignition timing can be advanced over where it might be for a lower octane fuel. Lower octane fuels require retarded timing, so what?
Obviously premium fuels will also be less subject to pre-ignition, dieseling. But in either case, premium or regular, dieseling may occur for other reasons, a hot day, hot incoming airflow....
In the past this was often overcome by simply enriching the mixture, providing cooling to the cyclinder charge via more "cool" fuel.
Nowadays with the advent of DBW the engine ECU controls the throttle opening and therefore can restrict the cyclinder charge VOLUME and eliminate pre-ignition due to the dieseling effect.
So what about knock/ping due to engine lugging. Again, for modern day systems it the job of the engine/transmission ECU to monitor the knock/ping sensors and thereby prevent the transmission from operating in a gear that would result in lugging, engine knock/ping resulting from fuel octane, regardless of premium vs regular.
Not much different than a driver of a stick-shift would do.
Obviously performance is only an issue when operating with a WOT, Wide Open Throttle.
So what are the benefits of Premium vs regular?
A higher level of HP/torque at WOT and high engine RPM.
A wider lower range of engine RPM without knock/ping due to lugging.
Fuel economy...
Goes to regular fuel.
Have you noticed that diesel fuel on a unit measure basis now costs more than gasoline? Less refining cost/effort/level and less waste, castoff "material" and yet more costly?
It's called VALUE pricing.
A gallon of diesel fuel contains substantially more latent energy than a gallon of gasoline.
As does a gallon of 87 octane of gasoline over a gallon of 92 octane.
Absent trying to attain maximum HP/torque a gallon of 87 octane will get you farther down the road than would a gallon of 92 octane.
It's a turbo, the ECU would probably dial back the boost and retard the timing, but then it will perform like a CR-V, so just get a CR-V in the first place and save yourself $10 grand.
-juice
Yup... CR-V would be it for those who want a vehicle with regular, even though it will be less of a performer than RDX, and with fewer std features. And cheaper too.
Does any currently offered turbo charged engine work "alright" with regular grade gasoline?
I bet some of the light pressure turbos would run on Regular, but I still would not recommend it.
I have a '93 Miata, the timing is set manually on those. I advanced the timing slightly, stock is 10 degrees before TDC, I went to 14. With premium fuel you can go to 18.
Any how, if I lug the engine, use too low a gear on an uphill, the engine will ping. You gotta be careful, basically.
I'm sure modern ECUs will just retard the timing automatically, probably even dial back the boost, but then why get a turbo engine? You probably upgraded for the performance in the first place, I'd imagine.
-juice
-juice
And again, with DBW throttling 87 vs 92 octane make no difference except at PEAK Performance.
And unless you're a really avid "boy-racer" how often would you WOT an SUV all the way to redline?
Like hauling that extra weight around even when you commute alone. Or packing it up with kids and gear and making it up those 3000 ft elevation climbs. Carrying your lifestyle gear (bikes/kayaks) around on weeekends.
I suspect there will be plenty of times where you use full throttle, at least once per tankfull.
And it's not just at ultra-high rpms, in fact my Miata pings at LOW rpms, not high.
Edit: my point is it's all about engine load, not rpm or even just throttle position. SUVs always carry more load.
-juice
Good one! Although, I didn't mean to come off as the thought police. I'm glad we can move forward now.
For the record, until recently I owned a Saab 9-5 aero, 250hp from a 2.3 liter 4, great car, and I always put premium in without batting an eye.
1. It's a manual transmission and the driver hasn't yet learned how to "operate", stir, the gearbox so as not to operate the engine below the power curve. Assuming this one is valid than stop lugging the engine, that can cause real damage in the long term.
2. Assuming its an automatic the engine/transmission control ECU has no indication of engine knock/ping. Therefore hasn't a clue that it's in too high a gear ratio for the current circumstances.
With e-throttle and regular octane, SUV, whatever, you are free to go WOT anytime you wish, all you want too.
Well, not really.
You can depress the footfeed as hard as you wish, but as the engine approaches redline if the ECU senses any level of knock/ping, detonation, resulting from moving the throttle valve wide open in response to your input then it will start closing the throttle valve to reduce the "charge" going into the cyclinders assuming it has already reached the maximum fuel/air enrichment level.
My fault, absolutely, but it was an example meant to show that under load the engine is stressed more, even at low rpm and not at WOT.
-juice
And your example, as I said before, is with the engine "loaded" beyond its design torque development capability.
-juice
That can occur due to "pre-ignition" caused by ignition mistiming, hot spots due to things like carbon debris, or dieseling, wherein the mixture self ignites due to the heat of compression. All of these have the ability to begin the flame front "spread" even before the piston reaches TDC.
But none of the above pre-ignition conditions need occur to have knock/ping occur due to engine lugging.
If Acura says to use 91 octane or higher, just use it. If you are that strapped for cash (i.e. the extra $0.20/gallon @ about 50 gallons / month = $10/month) than you shouldn't be worried about gas... you should be worried about making your monthly payment, your monthly insurance payment, and any maintenance on the vehicle. If that $10/month is going to kill you, then by all means get the cheaper gas, but don't expect to get the kind of numbers quoted for the RDX as those are based on the recommended fuel.
Test drove the new 6 cylinders RAV4 recently and was somewhat disappointed as with its 269 hp engine I found it was too powerful to modulate for smooth ride within the city, power just surged in when slightly touched on the gas pedal. When I tried to merge into the highway traffic the car was abruptly jerked to the left when I put on a little bit more gas and the road condition was nice and dry; guess it may due to basically a front-wheel drive vehicle and the Power-weight ratio may not be too balanced.
RDX's 4WD system appears to be impressive on paper and it may be even good for high speed performance. But what about it's outward rear wheels torque-shift feature? Will that cause any safety issues when driving on slipery road surface even with the ABS brakes and Stability control?
Does RDX have the All-time 4WD system? How does that compare to Subaru's 4WD system? ( I heard Sub has the best All-time drive system for non-off-road driving).
Getting 70% of total power available to just one wheel and with the “acceleration device” (which speeds up the inside wheel by up to 5%) is designed to rotate the vehicle under throttle and during cornering. This will ensure better traction and stability. And of course, like all Honda/Acura light trucks (except base Element, IIRC), stability assist with traction control (“VSA”) is still going to be standard.
http://hondanews.com/CatID3007?mid=2005081756995&mime=asc
The RAV4 uses a system that is sorta like Honda's VTM-4 which is found in the Pilot and Ridgeline. It doesn't have all the featues, but the basic operation is similar. Electronic sensors detect slippage and an electromagnetic coupling hooks up the rear wheels. I believe the RAV4s even have a lock button for low speed use. That is where the similarities end, though. VTM-4 has a few other features not found in the RAV4.
Subaru's various AWD designs are also very good. Unlike the RAV4, they are not reactive. With the most common variant, some torque (approx. 10%) is always being sent to the rear wheels. Like SH-AWD, it can progressively distribute torque from front to rear. It has a wider range of distribution going fore and aft, but there is no side to side movement. So handling is not improved as significantly.
I can't comment on how Acura will tune its throttle pedal (more linear perhaps?) but I do expect a more advanced AWD system to effectively reduce that feeing of torque steer you noticed.
You must have pretty keen senses, as a lot of people would not even notice the subtle differences. Good for you.
-juice
In that way Acura, and some other marques, are now over-coming the unsafe, or even hazardous charactoristics, that typically arise from FWD, driving only the front wheels, or the numerous AWD systems that are always front torque biased.
FWD torque stear is most noticeable with lots of throttle or turning tightly and cannot be missed or avoided during tight turns w/WOT.
In those circumstances the SH-AWD system will dynamically allocate engine torque primarily to the rear wheels and therefore that will be very little halfshaft "wind-up" difference between the short halfshaft and the long one.
"RWD", no torque stear.
The idea behind this is to prevent slippage before it happens. But it also prevents torque steer.
If I'm not mistaken, Subaru's system (for the automatics) starts the car out in a 50/50 power split. Whenever it's in 1st or 2nd gear, it proportions torque equally fore and aft. That essentially eliminates torque steer and the risk of slippage, as well. Of course, they use a longitudinal engine layout. Without unequal half-shafts torque steer isn't a problem to begin with.
The manual trannies with the viscous couplings are 50/50 and then adjust when there is slip.
VDC is more proactive, but that only comes on the Tribeca and high-end Outbacks and Legacys. Default is 45/55, rear biased.
So basically all Subaru AWD systems will be sending at least 50% of torque to the rear wheels when you are starting out in first gear.
RAV4 starts out at 100/0, i.e. FWD, then adjusts. Hence the torque steer. I bet it's less of a problem with the 4 banger.
-juice
The wife veto'd it because of the rear door that blocks the curb, however.
-juice
Seriously Toyota, how hard would it have been, with a major redesign already, to switch the rear door hinge side? Oh, you must sell more of these in RHD countries... NOT! :confuse:
Now back to our regularly scheduled topic.
Thanks
This scenario is unlikely to happen since people won't push it that way under poor weather/road conditions. And even if they do, the system would have maximized traction anyway (the inside wheels don't do much to put the power down properly during cornering).
And if there is a side slip detection... RDX will have stability control standard.
SH-AWD (used in RL and to be used in RDX) is an advanced version of VTM-4 with a few additional features.
WOT implies wide open throttle.
Front or Rear Torque bias is about how much torque (or power) is being sent to front or rear axle compared to the rear or front axle respectively. For example, under normal cruising, SH-AWD would send 70% of the power to the front wheels and remaining 30% to the rear wheels. So, at this point, it will be a front bias system.
When you attempt to accelerate in a straight line so that now the system send 60% of the maximum torque to the rear wheels (remaining 40% to the front), it would become a rear-bias system.
-juice
As for the rumors about a V6 CR-V, those are just rumors. Nobody knows anything reliable at this point. I can say that I doubt very much it will get the SH-AWD system. That system will likely stay an Acura-only feature for a few years. Instead, the CR-V may receive a version of the VTM-4 system.
While turning, especially tightly and/or under moderate or heavy power, it can be really important that the front tires roadbed adhesion coefficient be dedicated to lateral, direction control, not engine leading or lagging torque.
That's one of major shortcomings of FWD or front biased AWD.
Honda has aimed for about 8" with most of their crossovers and the truck. The only exception is the Element, which has about 7". Somewhere in between those figures is as good a guess as any.