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Acura RL

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Comments

  • jeff88jeff88 Posts: 94
    Has been difficult to keep up...

    was reading about 300 posts ago about the octane discussion and maybe missed this but this is one thing I've noticed.

    When running premium gas, the shifts were smoother than running 87. It appeared to me that the retarding of the spark prior to shifting wasn't as well timed with 87 as it was with 93. Upon occasion, my wife would accidentally fill the rl with 87 when driving it since that is the grade for her ride. It was noticeable to me afterward.
    -----------------
    other comments were about the looks of the pre-'05 rl; I have always thought it to be a very pleasing look inside and out but then again, I'm biased.
    -----------------
    someone wrote that their I-4 in their accord felt to a passenger like a 6; my impala company car has a v6 that feels like a 4...

    ...or as a friend once said, it ain't the size of the boat, it's the motion of the ocean.

    Think he may have been describing something else.
  • saugataksaugatak Posts: 488
    J35A is also the perfect example to illustrate that output isn’t necessarily dependent only on compression. There are more ways to getting it done. Odyssey & Pilot have the 3.5/V6 rated at 240 HP, and while using same compression (10.0:1), the version in MDX is rated at 265 HP. That’s using simple tweaks to the intake and the valve heads.

    Are you sure this is the case? I've run my MDX on regular fuel and I can feel the loss of HP, might even be 20HP or so which would bring it down to the level of the Ody or Pilot.

    Is it possible that Honda used the EXACT same engine for the Ody, Pilot and MDX and just tweaked the software in the Ody and Pilot so that it could not take advantage of premium fuel? That would seem to be easier and cheaper than tweaking intake and valve heads.

    Aah, the benefits of variable valve timing & lift, and multi-stage intake! I’ve observed Honda engines enough to bet that it will deliver more than 90% of its peak torque from about 2000 rpm.

    Honda's engines are impressive, but not in regards to developing low end torque.

    IMO, Nissan's engines alwasy felt way more torquey than Honda's engines.

    GM's LS1 develops abut 295 ft.lb. of torque (or about 80% of max torque) at about 800 rpm and hits 90% of peak torque below 2,000 rpm.

    http://www.gm.com/automotive/gmpowertrain/engines/gmpow/images/ls- - 1curve.jpg

    The Hemi produces 80% of peak output at around 1,200rpm and 90% of peak output at 2,000rpm. Here's a small and barely readable torque curve chart of the Hemi.

    http://www.popularhotrodding.com/tech/0403phr_hemi/

    GM's upcoming 3.9L OHV v6 (which also has VVT) produces peak 245 ft.lb. of torque at 2,800 rpm, so it's a safe bet that it'll produce more than 90% more torque at 2,000 rpm.
  • lexusguylexusguy Posts: 6,419
    Nobody is going to argue that OHVs dont make serious torque down low. They do. The problem with OHV (aside from its general low techness) is the sheer size it has to get to make competitive power to a SOHC or DOHC engine. The LS6 is pushing 6.0L. A 3.9L six that only makes 245ft.lb of torque is hardly what Id call efficient. I bet its hp figures cant match modern DOHC either. I seriously think the OHV 6 is on its death bed. How large would an OHV 6 have to be to match the horsepower of Acura or Nissan's 300hp 3.5L engines? 4.5L? 5.0L?
  • saugataksaugatak Posts: 488
    The point is that OHV engines are actually SMALLER than comparable OHC engines. Whereas OHC engines have cams sitting on top, the OHV engines have a "cam in block" architecture and so have one cam sitting within the valley of the V, which would otherwise be wasted space.

    DOHC V engines in particular are very large. Compare the size of 4 cams on top vs. 1 cam nestled in the V.

    While a 3.9L v6 sounds like a HUGE v6 engine, it's not. It fits in comfortably in the upcoming Pontiac G6 which is a FWD car.

    You're focused on specific output (HP/L of displacement) as a measure of efficiency. Another way to determine efficiency is HP/volume of engine size, and by that measure, OHV engines are just as, often more efficient than, comparable OHC engines.

    Another example is the 5.7L Hemi, which is a pushrod. It fits not only in trucks, but also in cars, because it's not a big engine for the amount of displacement it gets.
  • saugataksaugatak Posts: 488
    BMW gets even more horsepower than the RL from a smaller displacement inline in their M3.

    I've love to see a torque curve chart of BMW's inline 6's b/c when driving them, I always felt they had more low end power than any OHC v6's I've driven.

    Theoretically, a good inline 6 should have more HP and torque than a v6 b/c the I6 doesn't have a balancer shaft robbing it of power, whereas a v6 does.

    There are also reliability issues. While the M3 straight 6 produces gobs of torque and power, it's had some reliability issues.
  • lexusguylexusguy Posts: 6,419
    Well, to a certain extent that has to be expected, considering how hard BMW has pushed that engine in order to not have to resort to forced induction. Hat es einen Turbo? NEIN! sind wir BMW!
  • saugataksaugatak Posts: 488
    Aah, the benefits of variable valve timing & lift, and multi-stage intake! I’ve observed Honda engines enough to bet that it will deliver more than 90% of its peak torque from about 2000 rpm.

    You mention VVT and multi-stage intake as 2 factors enhancing low end torque.

    I'm wondering how much VVT actually helps low-end torque? I always thought the extra valve lift was beneficial at higher rpms so that the engine could suck more air. I'm not sure how extra valve lift will help at lower rpms.

    For example, the Hemi and LS engines don't have VVT, but they do have multi-stage intake manifolds (pretty high tech for those low tech pushrods), and they're getting 90% peak torque at 2,000 rpm.

    GM's upcoming 3.9L OHV v6 adds VVT to a dual stage intake manifold and gets 90% of peak torque at 1,800 rpm. GM's engineers indicate that it's the dual stage manifold that is responsible for a broader torque curve.

    http://www.auto-report.net/index.html?gmpt05.html

    The variable intake manifold is a significant low-speed torque 'enhancer' for the 3900. It gives the 3900 a broader torque curve that retains higher specific torque output across the engine speed range.

    As far as I can see, multi-stage manifolds are mainly responsible for enabling engines, whether OHC or OHV, to hit 90% of peak torque at around 2,000 rpms.
  • saugataksaugatak Posts: 488
    Excellent post, as always.

    I read through your post carefully again and 3 things struck me right off the bat:

    1. How creative Honda engineers are in tweaking their I4 engines to achieve the desired HP and torque/powerband.

    2. No matter what the Honda engineers did to boost power, they're still limited to a max. torque of around 160 ft.lb.

    The 2.4L I4 Accord with a compression ratio of 9.7:1 gets 160HP and 161 ft.lb.@4,500 rpm, the 2.4L I4 TSX with a compression ratio of 10.5:1 gets 200HP and 166 ft.lb.@4,500rpm.

    So a 0.8 increase in compression ratio yielded a whopping 5 ft.lb. of extra torque. Wow.

    I guess if the RL takes the MDX engine and boosts compression ratio to 11.0:1 (which is the same compression ratio as the TL), it may get to 260 ft.lb. We'll have to see.

    3. We're making a big deal out of getting the torque curve as flat as possible and as low down the powerband as possible, saying things like "90% of peak torque available at 2,000 rpms." But still, 90% of 160 ft.lb. is only a measly 144 ft.lb. of torque.

    At some point, you have to bump up displacement to boost max torque. It looks like multi-stage manifolds help flatten out the torque curve and broaden the powerband, but there is still no replacement for displacement (except supercharging perhaps) when it comes to increasing torque and low end power.
  • ksomanksoman Posts: 590
    >>>
    3. We're making a big deal out of getting the torque curve as flat as possible and as low down the powerband as possible, saying things like "90% of peak torque available at 2,000 rpms." But still, 90% of 160 ft.lb. is only a measly 144 ft.lb. of torque
    <<<

    GEEZ mang! If 144 is measly, then basically 160 is measly too. On a comparitive basis, 90% is a lot and very close to 100%.

    The fundamental reason to try to bring the torque curve flat (oxymoron) is try to bring torque as lower in the rpm range as possible. For big bad engines, they have a huge torque advantage in the lower RPM range purely because of size, not because of brains.... whereas for the small engines, they have to be smarter. I think the whole purpose of raw torque against raw HP is because torque really is what helps you break the coefficient of resistance of the myriad things that are at rest when a vehicle is at rest. Once you start spinning, the use of torque starts to lessen (not eliminate, diminish). That is where high RPM & screaming engines come into play, basically the reason why the s2000 is not the fastest from the readlight, but when its spinning, it can whoop anybody's "ahem", rear! Also, on that logic, just getting more and more torque is not necessary.

    Lets say Engine A is pumping 400 lb-ft of torque max, at 4500 rpm, and 120 lb-ft at 2000 rpm
    Enginge B is pumping 250 lb-ft of torque max at 4200 rpm, and 180 lb-ft at 2000 rpm
    Obviously engine 2 is better in my dishonest opinion. It is more capable of breaking resistance and getting the fat pig rolling. As the car speeds up and the gearing controls where the car can keep in the powerband, you are good to go. If you still can't get your car moving fast, one of two is likely, you either are incapable of shifting your gears if its a manual or if it's an auto, the computer controlling the shift points was just designed by morons and that car company needs to shutter down yesterday!

    couple of comparitive notes:
    the starter motor on your car, its a DC motor, cuz it pumps loads of torque up front, right of the bat... that's to break the resistance of non-moving parts quickly.
    the huge electric locomotive engines, they use DC motors, not AC motors. DC motors have a huge torque advantage in the lower RPM, where as AC motors have better torque later in the RPM range. Considering how much mass the locomotive is pushing or pulling, and that too on smooth steel wheels on a smooth steel rail, you want the torque up front to overcome the coefficient of resistance as quickly as you can. Have you seen a electric locomotive spin its wheels? Yes it actually does do that at times.

    ksso
  • varmintvarmint Posts: 6,326
    Without a VVT system, the engine must accept a compromise. There are three choices.

    1. Allow the engine to breathe freely at higher RPMS (producing good horsepower) and sacrifice the low end torque.

    2. Allow it to breathe efficiently at the low end (producing good torque) and sacrifice the high end horsepower.

    3. Pick a middle ground that does both well enough, but neither of them particularly well. Most engines would fall into this category.

    With a VVT system in operation, the engine can change breathing apparatus to match the situation (high or low rpm). In other words, the engine can have its cake and eat it too.

    In the past, Honda has used VTEC so that it produced the greatest amount of horsepower. Horsepower was the priority for cars like the NSX and Integra. The lower rpm intake cams were designed to function more like a number 3 engine. They serviced both the low end and the middle ground. Meanwhile the upper rpm intake was designed to get the most from the high end. So the second set allowed the top end to function like a number 1 engine. Honda still takes this approach with cars like the S2000.

    This approach spawned the myth that VTEC is only good for the top end. Truth is, those engines made decent torque down low for an engine of their size. It's just that most other cars were using bigger engines or forced induction.

    Anyway, it doesn't have to be that way. VTEC can also be used to make an engine work both as a number 1 and a number 3. It could produce good torque down low and hold it through the middle range. The original MDX engine was a decent example of this.

    What about an engine that works like a number 1 and a number 2? Why not build an engine that focuses on both the high and low ends? Well, the technology is good, but it's not the answer to everything. Such an engine would have a weak mid-range. That hurts driveability and smoothness. Remember, there is more to a good engine than just power output. There's also NVH, fuel economy, emissions, reliability, cooling, and a host of other considerations to juggle.

    With the addition of VTC, Honda is working out how to correct for problems with a smooth power curve. The addition of VTC is yet another way to manage air flow which can compliment VTEC. The combination is called i-VTEC in Honda speak. All three of the 2.4L engines I mentioned earlier use i-VTEC to produce what is essentially a very broad torque curve for an I4 engine. I mean, the torque curve for the TSX's I4 doesn't look as good as BMW's I6, but it's pretty darn impressive for a 4 banger.

    Okay, now imagine all this being applied to a 3.5L V6... Right now, none of the J series engines makes full use of the technology Honda has developed in recent years. Probably because of the expense. With cars in the price range of the RL, cost becomes less of a priority. So it's possible we'll see a fully blown V6 in the RL.
  • robertsmxrobertsmx Posts: 5,525
    Honda's engines are impressive, but not in regards to developing low end torque.

    Well, I don&#146;t expect a 2.0-liter engine to match the torque output from a 6.0-liter engine. Do you? In RL, the rated peak can be expected to be about 260-265 lb.-ft. Is that lack of torque compared to other engines with similar displacement?

    And it is not just the peak torque either, we have been talking &#147;range&#148;. If RL&#146;s engine gets 260 lb.-ft and provides 90% of it (about 235 lb.-ft) or more between 2000 rpm and 6500 rpm, I would say that it is not only high for the displacement, it is also a very broad torque curve!

    As for the OHV versus SOHC/DOHC debate, let us use the thread that exists for the purpose.

    BMW gets even more horsepower than the RL from a smaller displacement inline in their M3.

    RL isn&#146;t supposed to get its peak power at 8000 rpm. Its 300 HP will likely arrive around 6000-6200 rpm range (pretty much where everybody else is rating the peak power these days), and red line at 6800 rpm or so.

    That said, it is unfortunate to not see Honda use its engine expertise in high performance sport coupe/sedans. The last time I heard about something along the lines was the NSX GT-R that participated in Honda&#146;s 50th anniversary parade, powered by a 380 HP version of its 3.2-liter V6. This engine was used in Real Time Racing NSX for World Challenge GT Class, before they switched to a supercharged version.

    So much for Honda not being able to get &#147;enough&#148; HP/liter out of its engines. :-)

    I'm wondering how much VVT actually helps low-end torque?

    I&#146;ve a perfect illustration for you. Japanese Accord 24TL (AKA Acura TSX in North America) and American Accord use variations of K24A engine. The dynographs (below) would be helpful.

    Honda Accord 2.4
    Acura TSX 2.4

    Accord&#146;s engine produce 90% of its 161 lb.-ft (about 145 lb.-ft) or more between 2500 rpm and 5800 rpm, while the TSX version produces 90% of its 171 lb-ft (abut 154 lb.-ft) or more between 2000 rpm and 6800 rpm. Obviously, TSX not only has a higher torque curve, but it is broader as well.

    The TSX version does have additional tweaks, besides VTEC being applied to intake as well as exhaust side whereas in Accord it is at the intake side only.

    That said, the basic idea behind variable valve timing systems is to enhance low-end torque without compromising the same at the top end, and vice versa. It would be possible to get 200 HP out of a 2354 cc I-4 without I-VTEC, but try to imagine the shape of the torque curve.

    A basic engine can be tuned to develop most of its torque at low end, and the output will taper off quickly past the mid-range. If you had a secondary cam profile that got activated in the mid-range, the output will stay up in mid range and above (broadening of the torque curve) instead of tapering off.

    To understand the impact, superimpose the two versions of Northstar that existed. Northstar used single cam profile, one tuned to produce a little more torque at a lower rpm (300 lb.-ft @ 4000 rpm/DTS) and compromised a little at the top end (rated 275 HP@ 5600 rpm). The other compromised a little at the lower range (295 lb.-ft @ 4400 rpm/STS) to gain a little on the top end (300 HP @ 6000 rpm).

    If it were possible to keep the better low end output from the DTS version while retaining the better top end output from STS version, we wouldn&#146;t be talking about compromising one for the other. And that&#146;s where variable timing would come into play.
  • ksomanksoman Posts: 590
    good points.

    ksso
  • varmintvarmint Posts: 6,326
    "No matter what the Honda engineers did to boost power, they're still limited to a max. torque of around 160 ft.lb." - Saugatak

    Yeah, that's true. But I think that has more to do with the fact that they are working with an I4 engine displacing only 2.4 liters. I know of no other petrol 2.4L that produces significantly more torque without resorting to forced induction.

    "I guess if the RL takes the MDX engine and boosts compression ratio to 11.0:1 (which is the same compression ratio as the TL), it may get to 260 ft.lb. We'll have to see."

    Everything is speculation at this point. But, unlike the 2.4L I've mentioned, we are now dealing with 3.5 liters in a V configuration. I don't think it is unreasonable to expect a larger boost of more like 10-12 lb-ft with that engine. And there's always the chance that Honda will add something like VTC to the RL's block, which is not found in the MDX, TL, or Pilot.

    So, I think 260 or 265 are both reasonable estimates. But my original point was while these peak numbers may come at 4,000 rpms, that does not mean there is no torque in the bottom end.

    "At some point, you have to bump up displacement to boost max torque. It looks like multi-stage manifolds help flatten out the torque curve and broaden the powerband, but there is still no replacement for displacement (except supercharging perhaps) when it comes to increasing torque and low end power."

    Ultimately, yes, I think you are correct. There is a limit to how much torque can be produced by a given displacement. But what I'm expecting from Acura is a V6 that provides as much torque as the other V6s in this class and horsepower that is closer to the V8s. Assuming the car is priced like the other V6s, how is that a problem?
  • robertsmxrobertsmx Posts: 5,525
    How creative Honda engineers are in tweaking their I4 engines to achieve the desired HP and torque/powerband.

    Not just Honda, just about any engineer is expected to be creative. And why just I-4, you see it in the V6 as well. Don&#146;t you?

    No matter what the Honda engineers did to boost power, they're still limited to a max. torque of around 160 ft.lb.

    Putting this in perspective, 161 lb.-ft to 171 lb.-ft from a 2354 cc engine is quite good. And especially considering that at least 90% of the peak torque is available for a range of (almost) 5000 rpm!

    Do you not agree?

    We're making a big deal out of getting the torque curve as flat as possible and as low down the powerband as possible, saying things like "90% of peak torque available at 2,000 rpms." But still, 90% of 160 ft.lb. is only a measly 144 ft.lb. of torque.

    So, are you suggesting that it is better to not have a flat torque curve from an engine producing 160 lb.-ft? For that matter, any engine regardless of the output?

    At some point, you have to bump up displacement to boost max torque.

    Undeniable fact. But, how is it better to increase displacement every time torque has to go up? To put this in perspective, for couple of years, a version of Honda 3.5/V6 produced 229lb.-ft. In case of RL, we&#146;re now &#147;talking&#148; 260 lb.-ft. Should Honda have bumped up the displacement to almost 4.0-liters to achieve 260 lb.-ft? To me, it appears, engineers managed to get more from the same and I can never associate that with being a bad idea. Technological advancement is the obvious answer!

    Now, if we were talking 300 lb.-ft or more, I don&#146;t see how a normally aspirated 3.5-liter engine could achieve that, in which case, the displacement will have to be bumped to 4.0-liter or so (a &#147;really good and efficient design&#148; typically gets about 75 lb.-ft per liter displacement), unless the efficiencies of the engines suddenly changes. Even in racing forms, the engines are barely hitting 90 lb.-ft per liter at max.
  • markcincinnatimarkcincinnati Posts: 5,069
    At some point, you have to bump up displacement to boost max torque. -- back to the old no replacment for displacement axiom?

    Generally the replacement for displacement is better breathing and better breathing via some form of forced induction seems to be very effective and very efficient. Further gains can be achieved via ultra high compression ratios (12:1, e.g.) and direct (or fuel stratified) injection. The technical tricks that are coming soon to an engine near you are quite impressive.

    And, we've also talked about the max torque available @ 0 RPM's of an electric DC motor -- the main reason for the low down torque, as noted herein by severl of us, is off the line acceleration (perhaps [improving] the 0 - 62 sprint is enough [of a range] that the assist could be kept, mainly, to achieve that goal).

    In any case the "new" Acura/Honda 3.5L with twin turbos and enough "beefing up" to make reliability not an issue, would get them where they "want" to be with little fuss or muss. Torque would jump impressively and HP should surpass 400HP, which in the RL ought to be plenty for both bragging rights and absolute performance and efficiency.

    I know, "not gonna do it," "wouldn't be prudent."

    I can dream, can't I?
  • varmintvarmint Posts: 6,326
    Uh-oh, the engine boys are in town... =)

    Yes, I don't think their is an ultimate limit to how much torque can be provoked from a given displacement. In the year 2025 someone may find a way to get 110 lb-ft per liter. The envelope is always being pushed. The goal posts are always moving farther away.

    I think the trick in speculating about the RL is trying to "keep it real". We do that by guessing within the parameters of what Honda is already capable of doing today. Hence all this discussion about other Honda engines.

    All this makes me wonder how the others will respond. It's all fun and games to compare numbers like this, but it's the market that will determine how much power is needed. Maybe people won't care about the RL's horsepower advantage. Or maybe the others will be forced to adjust their 6 cyl offerings in either price or output.
  • markcincinnatimarkcincinnati Posts: 5,069
    IMO, people will indeed care about the HP number from Acrua -- @ nearly $50K? You bet!
  • robertsmxrobertsmx Posts: 5,525
    Another technical trick that Honda has developed and is offering in a model in Japan is its own version of DI, dubbed &#147;I-VTEC-I&#148;. But, will it happen with the V6? We shall see. But it is probably more about improving fuel economy than anything else.
  • saugataksaugatak Posts: 488
    GEEZ mang! If 144 is measly, then basically 160 is measly too. On a comparitive basis, 90% is a lot and very close to 100%.

    Yes, that's exactly my point. I'm not denying that Honda is great at doing a lot with a little, but this is America, the land of no displacement taxes.

    Why can't Honda just bump up displacement and use its VCM technology so that we can get both power and decent gas mileage?

    Lets say Engine A is pumping 400 lb-ft of torque max, at 4500 rpm, and 120 lb-ft at 2000 rpm

    Enginge B is pumping 250 lb-ft of torque max at 4200 rpm, and 180 lb-ft at 2000 rpm
    Obviously engine 2 is better in my dishonest opinion.


    Not disagreeing with you, but who says the best technology needs to be used on smaller, less powerfu engines? Why not use the same technology on the bigger engine and get the same flat torque curve?

    The RL is supposed to be Honda's flagship. I can't see Honda skimping on the technology front for the RL's engine.

    As the car speeds up and the gearing controls where the car can keep in the powerband, you are good to go. If you still can't get your car moving fast, one of two is likely, you either are incapable of shifting your gears if its a manual or if it's an auto, the computer controlling the shift points was just designed by morons and that car company needs to shutter down yesterday!

    But in city driving, you're going fro 0 to 40 mph A LOT. The fact is, unless you're racing, low end grunt is usually a lot more useful than high revving HP. Also, isn't the RL supposed to be a luxury car, not a sports car? This class of car is supposed to have low end grunt so that you can accelerate smoothly without making the engine scream, which is bad for NVH, an important consideration in luxury cars.
  • robertsmxrobertsmx Posts: 5,525
    Have you figured out yet, how much low end grunt is &#147;needed&#148;?
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