d0 Luck

Am I the only one who finds it very weird that the only thing missing from the LS7 motor technology is direct fuel injection??? Does the prototype supercharged powered C6 Stingray Z06 incorporate direct fuel injection? With it, I think it's very realistic to see a 13.0:1 or even 14.0:1 compression ratio, along with better torque and hp, and heck, better MPG too on an LS7.

It's actually not new technology as Nissan had been using is since '97 (sp?) in some of their motors in Japan (and Europe only) like in the Stagea wagon (sp?). Audi, BMW/Mini, and Mazda are currently the only ones with offerings in direct fuel injection in some brand models here stateside if I'm not mistaken.

To those who are unfamiliar with direct fuel injection, here's a quick read:
http://www.hitachi.com/ICSFiles/afie...4_04_103_1.pdf

Cliffnotes and benefits to direct fuel injection:
- availability to run higher c/r i.e.: Mazdaspeed 3 is running 9.5:1, Mini Cooper S and Audi 2.0T motors are running 10.5:1, iirc. All are turbocharged. This is the only way these car companies can offer warranties with the help of DFI.
- stoichiometric a/f ratios much higher, around 63:1 (at least with Europe based DFI) in comparison with 14:1 from conventional port fuel injection
- better MPG
- increases in hp and tq
- higher knock threshold
- great modification platform to play with

So, anyone got info on when the Corvettes/Camaros going to incorporate direct fuel injection? This is the second reason holding me back from doing a V8 powered RX-7 ever since.

Thanks,
-Ray

slo

iTrader: (1)

No technology can change the stoichiometric ratio of a fuel, 63:1 would be way higher than stoic for gas and just about any fuel that I'm aware of.

You might as well be asking for Vtech,and double overhead cams.

Its noy likley that GM will make an LSX with dirrect injection any time soon, the only gm engine with dirrect injection is the new ecotec.

d0 Luck

63:1 stoichoimetric is ideal for direct fuel injection. At least in some of Europe's DFI equipped cars since their gasoline has low-sulfur content. US gasoline has higher-sulfur content, so the stoichiometric with DFI would be lower of course.

Please, do a search before you personally debunk what's already been proven.

slo

iTrader: (1)

Did you get that from a bazooka joe comic?

I realize what your trying to say but either your confused or your confusing terms.

First awnser a question, what is stoichiometric, I will help you with this ( http://en.wikipedia.org/wiki/Air-fuel_ratio ):

"When all the fuel is combined with all the free oxygen, typically within a vehicle's a combustion chamber, the mixture is chemically balanced and this AFR is called the stoichiometric mixture (often abbreviated to stoich)."

For regular gas that mixture is about 14.7:1. There is no technology which can change this without changing the gas itself.

63:1 would be a mixture very lean of stoich. Now that in fact may be the most efficent mixture for a particular engine under specific conditions, but that is not stoich mixture for that engine, which as I have previously said is approx, 14.7:1. The stoic mixture doesn't change between engines only between fuels.

That said dirrect injection is a promising technology, especially for the rotary engine, it could possibly make a rotary engine as thermally efficent as a piston engine. (according to research by mazda, commented on in a few books I had read) Not to mention the fact that you could make a periperal port where port overlap wouldn't effect gas fuel economy. But none of the example you sited in your original post are that extreme.

Especially hi compression ratios on turbocharged vehicles, go look up dynamic compression.

d0 Luck

And like I said for the second time; this is under Direct Fuel Injection conditions. Can you not read???

14.7:1 stoichoimetry is under Multi-port fuel injection, which is your conventional fuel injection of what we have now. AGAIN, port fuel injection is different from direct fuel injection.

It's also common-sense here. Let's take the new 2007 Mini Cooper S and Audi 2.0T motors which are both direct fuel injected; they are both running 10:1 something compression ratio and it's turbocharged, runs on crappy 91 pump gas, and the car manufacturers offer warranties on them. Do you see where this is going?

Are you blind not to see that the stoichiometry in direct fuel injection is entirely different from conventional fuel injection given those conditions above???

Put it together man...

slo

iTrader: (1)

The static compression may be 10-1, the dynamic compression may be far far less, especiially with any type of variable valve timing.


your just wrong.... The stoic ratio of fuel does not change between engines.

suckerfree

I think what do luck is referring to is HPDI (high pressure direct injection). Higher pressures mean greater fuel atomization, which results in a higher obtainable afr. Im drunk right now, but as i recall this was in hot rod, so it must be true. Otherwise...

slo

iTrader: (1)

Yes I know what direct injection is. Theres actually a little more to it than than. with port fuel injection the leanest possible afr is limited to an afr which the spark plug can light off reliably. Direct injection allows a small pocket of rich mixture to be created near the spark plug leaning out twords the edge of the cyl, to be reliable lit. This results in a clean complete burn of all the fuel with plenty of leftover air.

I have not made a statment which is contradicts that. A higher obtainable afr doesn't change the stoich ratio of gas.

And while better fuel control, with injection late in the compression stroke can help to prevent detonation, thats not the only factor. 10-1 is really nothing for a dohc turbo engine with agressive cams.

rarson

slo is right, I can't believe there is even a debate about this going on. I think d0 luck is misunderstanding the term "stoich."

That'd be like saying the specific gravity of gas in a direct injection engine is different than the SG of gas in a regular engine. It doesn't matter how you inject the fuel, that's not going to change it's physical and chemical properties.

He's also right that 10:1 isn't all that high a CR for turbocharged engines. Hell, Blitz turbocharged the Prius and that has a 13:1 CR.