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Mazda CX-7: Bring the diesel version to the USA!
I absolutely love this car, but with gas prices rising anything that gets 20 miles per gallon or less is too costly.
With clean diesel coming to the USA at the end of 2006, I don't understand why they won't bring the diesel to the US in addition to Europe in 2008. Doesn't make sense to me.
Please Mazda! You would have an easy sale if you did.
With clean diesel coming to the USA at the end of 2006, I don't understand why they won't bring the diesel to the US in addition to Europe in 2008. Doesn't make sense to me.
Please Mazda! You would have an easy sale if you did.
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I decide not to get one.
Any gasoline engine can be converted as all the engines in the past 10 years have engine computers that will advance the engine timing to take advantage of higher octane fuels. Propane has an ultrahigh octane of 105 ( R + M ) and the knock sensor on the engine will not detect any detonation until the engine computer advances the timing to the max. This allows better fuel mileage and performance compared to 87, 89 or 91 octane gasoline which costs WAY more.
The other advantage of doing a propane conversion is you can buy a used car or truck and have it converted. The best port LPG fuel injection systems allow you to leave all the gasoline system in place and add on the total LPG system. The car starts on gasoline and if the engine is cold, after 3 or 4 minutes, it switches to propane automatically. When you run out of LPG, it will automatically switch back to expensive low octane gasoline.
Of course, the minimum tax break for conversions to propane is a Fed tax deduction of $3,000. For trucks over 10,000 GVW, the Fed tax deduction is $5,000. There is also lower state and Federal tax on the fuel and some states also rebate part of the sales tax you paid to buy the vehicle even if you bought it 2 years ago.
Running on LPG is so clean that the engine could last at least 2 or 3 times longer than operating on gasoline or diesel. The exhaust systems and cat converters can last an easy 300,00 to 500,000 miles as propane burns hotter than all other fuels so it burns off any moisture buildup in the exhaust which causes rusting. Heat is energy and pound for pound, LPG burns hotter and cleaner than the other fuels including CNG. CNG also gives very poor mileage which is why the Nat Gas companies try so hard to bribe you with rebates. CNG sucks bigtime. I have driven all the alternate fuels in COMMERCIAL vehicles for almost 2 million miles over 26 years. Propane works the best because it's very high hydrogen content ( 18% ) burns so well.
After all, propane is found as is, in the ground with butane and natural gas (methane) and it is not refined, just separated out from the other fuels. Expect to loose about 10% in MPG with propane over the same engine running on gasoline if you have any engine built in the past 8 years. Trust me, it's worth the cost of conversion.
Instead of buying a 4 cylinder engine to save on fuel, buy a V6 and convert it to propane for longer engine life. In a full size pickup truck, or Cubevan, go for a V8 over the V6 as you will have a longer engine life and enough power to do the job without straining the engine. You may even get better MPG with the bigger engine as the rear axle ratio will be lower as well operating at lower RPM on the highway. This also adds to engine life as well. Many of the people in the limo business that use LPG have an engine life of over 700,000 miles on propane without even doing a valve job and almost no oil consumption. You were saying.....?
From what I found you have to convert to only run on an alternate fuel to get any tax break. Where would you put the tank in a small SUV like the CX-7? I think the diesel option in a small SUV would be far superior to any other fuel source. With a 4 cylinder diesel engine it should be easy to get 35 MPG on the highway. You would be hard pressed to get better than 20 MPG with LPG. And it is comparably priced to diesel in CA.
You can also hang a couple 5 gallon cans of diesel on the back of the rig for those long jaunts into the wilderness camping.
Somewhat true, but misleading. A stock engine computer and valvetrain components have a finite upper limit of their timing strategies. The engine is usually at maximum advance and is making maximum power on the fuel it is designed for (either 87 or 91 octane). The engine has the ability to retard the timing and reduce power when the knock sensors sense detonation (because of lower octane, etc.), but not to advance timing beyond this upper limit. In other words, under normal atmospheric conditions, you cannot get additional HP by running 150 octane fuel. The engine has no idea what the fuel octane is, only whether there is detonation or not. And it will advance the ignition only to its physical limits, which is set at its design octane rating.
Regardless, I think putting compressed flammable gas into mainstream private vehicles is an asinine proposition. Compared to liquid fuels, the hardware and space required to store compressed gas is inferior. You add weight, get less range per fill-up (if you look strictly at gasoline vs. propane), you lose the ability to drive through most tunnels and some bridges, and you add a system that most shadetree mechanics should not be touching. OTOH, The infrastructure for diesel is already in place and expanding, the experience of the manufacturers is there, and the technology is largely the same as a gasoline engine when it comes time to work on the fuel system - especially now that we are moving to direct-injection gas engines.
Diesel's not the end-all, be-all (we could never refine enough of it), and biodiesel won't solve everything, either (we could never grow enough crops). But if you want a clever solution (not the only one, but an easier one than compressed gas), look at running used vegetable oil in your diesel engine. Here's a restaurant product we can divert from the waste stream, and one that produces less emissions than any hydrocarbon. Plus, you leave a trail of french-fry odor wherever you drive. How cool is that?
That said, the US refining infrastructure is so outdated (ULS fuels only 10 years after Europe adopted them as standard), and according to the editor of Car & Driver (April issue) produces 10% less diesel than European refineries. US gas companies still serves up to 5 octane ratings, while Europe has just 2 (95 Ron and 98 RON!!), so there is no incentive for automanufacturers to develop better engines that people won't buy because they have to pay 10-15% premium over 'regular' gas.
No wonder our mpg rating is so woeful!
VW has just introduced a FWD vehicle with a stick shift using a technique that automatically up-revs the engine to prevent loss of control should the driver inadvertently downshift the transmission to a level that results in loss of traction due to poor roadbed adhesion.
Modern day engine computers use EFI/SFI PWM timing to simply ENRICH the mixture if detonation, not due to lugging, occurs. The computer uses the crank position sensor and the new non-resonant wide-band knock sensors to determine if the fuel combustion initiated upon ignition or prior. If timing is already fully retarded it simply enriches the mixture.
The turbocharger is the primary reason the CX-7's I4 engine gets such HORRID FE.
In order to provide for the "rise" in effective compression ratio as the boost comes up the engine MUST be derated in normal off-boost mode. Otherwise the DISI (DFI, Direct Fuel Injection) engine could have a native compression ratio of 12:1 and give you more decent FE when cruising along at relatively constant speeds.
The real answer would be to extend the range of the current VVT system such that the native compression ratio could be raised to 12:1 as in other DFI applications and then use delayed intake valve closing to gradually reduce the compression ratio as/when the turbo spools up and provides more and more boost.
Even better yet, make the native cylinder compression ratio 15-16:1 and then use the valve timing to bring in down to 12:1 under normal driving conditions. Then gradually transition to <10:1 as boost rises.
High FE Atkinson cycle mode off-boost and then transition to Miller cycle mode as boost rises. Even eliminate the wastegate this way, the delayed intake valve closing could be used to limit the turbine speed.
What I would like to do is mill the head of a CX-7 engine to get a compression ratio of 12:1. 12:1 has become typical for a DFI, Direct Fuel Injection, engine, but since the CX-7 is turbo charged the factory's "native" compression ratio is, as it must be, quite a bit lower in order to provide for the additional "compression" from the turbocharger as it spools up.
During the experiment the wastegate would have to be "wired" open so the effective compression ratio could not rise (much) beyond 12:1.
If anyone owning a CX-7 is interested I would be will to pay the costs purchase and install a new factory head once the experiment is complete.
I suspect the off-boost FE improvement might be in the range of 50%
What would be the basis for your suspicion? Is it just a hunch or are there real world numbers behind it?
tidester, host
SUVs and Smart Shopper
So "off-boost" this engine is quite heavily derated/detuned and runs in that mode 95-98% of the time.
Cadillac just happens to have two V6s in the market at the moment, one with DFI and one without. Compare the two and you get my theory.
tidester, host
SUVs and Smart Shopper
The turbo wastegate could be held open for low to moderate levels of acceleration.