_MMR_

http://ecomodder.com/forum/showthrea...rbo-11881.html

So I saw this some time back and came across it again lately and I have no experience with this engine at all except for what I've read. It seems like this could be a very interesting engine to play around with, however this guy claims 68mpg avg and 228hp with 12psi (doesn't say to crank or wheel). I'm curious as to how possible/impossible this actually is, what might be more realistic numbers, and if anyone has had first hand experience with this thing or tuning one.

JoeBlue

He drives it daily, so I'm not sure what you mean by it being impossible.

NotARaCist

iTrader: (1)

He didn't claim 68 MPG average, he claims 55 MPG average. I can tell you from personal experience, that's completely possible - I regularly made 58 MPG on a Y7 with a 15G on the highway. 220 is pushing the capabilities of that motor if it's a stock bottom end. He doesn't mention what kind of turbo the car has, which is kinda sketchy.

_MMR_

I'm talking about the power and mpg combination joe, I'll be more specific next time. If you read the whole thing he claims to have averaged 68mpg for the summer but 54 for an all time running average. Either way his numbers and your numbers are crazy, I would love to get a similar set up. Have you ever had hands on experience with the d15z7 nar (can I call you nar?) Or have an opinion of it?

NotARaCist

iTrader: (1)

There's a lot of complicated science'y stuff behind it, and that guy goes over it fairly well in his FS ad. Basically, more compression means more volumetric efficiency, which in turn means more power and better gas mileage. We can't just look at the math in a vacuum, though. More power means more heat, which means detonation. You have to spray more fuel to cool the combustion chambers down, which in turn means worse gas mileage. There's a fine balance between the three raw numbers that has to be found.

Once you get past the straight engine aspects of it, you can look at the turbo part. A naturally aspirated motor has a static compression ratio. No matter how high you're revving, or how slow you're driving, the CR will always be the same. Toss a turbo on there, and your CR becomes dynamic. The faster it spins, the more air it compresses, and the more air it shoves into your cylinder. Higher CR means better VE, once again at the expense of engine heat.

Another aspect that the seller hits pretty well is parasitic loss. When your car is sucking vacuum, it's robbing itself of efficiency - it's essentially working against itself during highway coasting. With a smaller turbo (something in the T25 or T28 range), or a more efficient turbo (ball bearing, or oil-less), the turbo creates boost at lower RPM, which helps negate the vacuum.

Like I said, there's a lot of science'y stuff behind it - this is just an over-simplification of it. I don't do D15's, so I can't help you there, but a T25 or T28 and proper tune could get stupid gas mileage, and still make good power at WOT.

92cxyd

A guy on D-series did similar
http://www.d-series.org/forums/force...g-64-8mpg.html

wantboost

iTrader: (2)

I can't even get 30mpg out of a stock f22a1. fml lol

NotARaCist

iTrader: (1)

Really? I was getting 28 MPG average out of my old '91 Accord, and if memory serves correctly, that had an F22A6 (I think, it's been a while). That was also back in my young, stupid days of "I'm louder, so I'm faster! I'm gonna neutral bomb my autotragic all over the place!"

Schister66

Interesting discussion

It could be worse...I barely get 20mpg out of my turbo 2.5L (using 92 octane)

Dark_Teg

I thought my fuel gage was broke after the turbo install. I seem to be getting high 30's if I stay out of boost.

wantboost

iTrader: (2)

I finally broke the 30s haha... made 34mpg this week driving in 20* weather in ice and snow... driving no different than normal. 85 on the highway and I make 34mpg. lawlz, cold weather FTW

although I did find out the gas gauge is a wee bit off, at least it died in my driveway (and runs great on 50:1 premix lol)

NotARaCist

iTrader: (1)

You know letting your fuel get that low is dangerous, right?