xstreetfiendx

diesel engines run high compression, because they pump air, that's not why they produce higher fuel mileage, diesel has a higer btu rating than gasoline, also because of that diesel engines have a lower BSFC than gasoline engines, that translates to better fuel mileage. It's only a matter of time before gasoline engines start to change dramatically, I mean ----, we've been using the same principles for decades, something has to change, because the car makers aren't doing ---- to help us out, I still see new cars on lots with posted city mileage of less than 35, that's gross as ----, gasoline prices here in canada are ridiculous these days, today's price being 105.9 a litre, which is what 4 bucks a gallon? who the ---- can afford to fuel up a car, pay for insurance, and afford to pay for a NEW car, like come on here, give me a break, the car makers are always trying to promote this and that about fuel mileage and how ---- has changed, sure it's changed a bit, but cars from the Big 3 still guzzle gas, that's nothing new, ---- I had to go and pick up my mom this weekend at the airport in her 2003 Grand AM, comes witht he 2.2L Ecotec 4 banger, that **** maybe gets 35 on the highway, maybe 30 in town? good lord.

Hitchhikkr

Jeez sounds like alot of apposing ideas and statements in here.
(awaits JD's response to this thread..................)

kamilk69

still less than my focus. :P

bigbossh22

E85 = 83,263 btu/gal
Reg. Unleaded = 114,132 btu/gal

Stoich E85 = 9.7:1
Stoich Reg. Unleaded = 14.7:1

I've run E85 through several small engines w/o a hitch, even a picky hi-po Goped motor. I actually wrote a paper quite similar to that MIT one, but focusing on my observations of E85 runtime vs. that of gasoline and got a superior rating at the state science fair...whoop dee doo.

The motor of the future is definately a direct injected, high c/r, lean idle, turbocharged, E85-powered unit. At least here in the midwest where even small towns have E85 pumps and in places where they're ethanol crazy, like Sweeden (Saab Biopower concepts, anyone?) and Brazil.

bigbossh22

seymore butts "Squirters 2", I'm pretty sure

Tom-Guy

I was actually going to suggest they ask you to comment on direct injection, since you love it so ------- much and can't shut up about it.

norwegian cRxXx

Becouse they pump air? what do you mean by that? Does not all engines pump air?

Diesel engines have high C/R becouse if they did not they would not work. You would not get high enough temprature for the diesel to vapor, or to ignite if it was not for the high CR, or high boost pressure.

The formula for the efficency of an engine during a ideal burning prosses (adiabatic) is E = 1(-1/CR^(kappa - 1)).
E=epsylon=efficency
Kappa in a adiabatic burning prosses is 1,4, in reality it fluctuates (polytrop), if we took that in to the summary it would also be in the diesel engines favour.

So: 1(-1/22^0,4) = 0,71 for a diesel engine with 22:1 C/R
1(-1/10^0,4) = 0,6 for a gasoline engine with 10:1 C/R

High CR gives less heat losses and a better type of energy (energy is not always just energy).

The only advantage with gasoline is that it burns faster, wich is a problem for diesel, that is why they only manage about 5000rpm. This is for the same reson as above, only in the other engines favor. Slow burning rate means more warm energy is lost out in the exhaust.

Another loss of having a throttle valve is that we have underpressure (vacum) in the intake, and when the inntake and exhaust valves overlapp, some exhaust gasses are pulled back in to the combution chamber. This gives lower combution temrature, and that gives lower efficency, and also lower NOX gasses (this is what the EGR system does normally, so offcorse in one way it is a bit positive).

But the biggest addvatage for the diesel is that when you don't need much engine power the lambda is really high, it can run up to lambda = 5 (city crusing), and the gassoline engine has to run labda = 1 all the time (can be up to 2,5 on FSI engines). So a 1,6 diesel engines uses a lott less fuel on crusing than a 1,6 gasoline engine.

I agree that E85 engines have a lot of potensial, but i still don't think a Otto engine will ever have better fuel efficency than a diesel engine. But i will continue to buy Gasoline engines, just couse they are so much more fun to drive, and if the maufacturers continue to develop the E85 engines, i really look forward to driving them, couse they have potensial of good MPG, and HIGH hp ratings. The VW 1,4 turbo and compressor engine have allready won lots of awards, but with higher CR and a bigger turbo it would be an awsome engine with really high HP and good MGP.

jinxy

Huh? Wouldn't any poppet valve engine have that problem as the action of the piston going downward in the cylinder is what's causing that vacuum in the first place? There's always going to be a pressure difference when the piston is moving downward in the cylinder it's self, regardless if there's a throttle body or not. Nothing really 'cools' combustion, to cool you have to displace energy, all I think exhaust gas would be doing is limiting the combustion of the fuel. Especially since it's going to be fairly close to the temperature of the combustion occurring within the cylinder, a lot closer than the ambient air coming in when it's that close to the head.

norwegian cRxXx

The overlap is a few degrees BTDC until a few degrees ATDC. So the piston is not moving much, down or up. But the second both valves are open (piston on its way up!) the huge vacum in the intake manifold on a Otto engine is making exhaust gas go back in to the combustion chamber. On a diesel engine you never have any vacum that is worth talking of.

The exhaust gasses take the place of air, so you don't get as much air in to the cylinder as normaly. The exhaust gasses does not burn, so you get a weaker combustion since there is less air. That means you don't get as high pressure, and that means you don't get as high temprature. Lower combustion temprature means lower NOX. This is excatly what is done with an EGR system, only you manualy put exhaust in to the inntake.

And btw, to temprature in the sylinder when the exhaust stroke is close to done, is like 5 times cooler then the temprature during the combustion.

Hitchhikkr

Lol direct injection pwns you. But the aftermarket is many years away from actually using it effectively for performance purposes. Ive messed around with it abit in the 08' cayenne turbo's, but from what ive seen the issue is going to be flow and tuning, as porsche uses multiple injections per cycle, to heat the cat mainly.

Actually I was talking about the e85 issue, since propane is my alternative fuel of choice.....I know nothing of the subject.