Well I just got back home after driving to and from InlinePROs shop in Virginia (about 4 hours from my house). I filled up 4 times throughout the trip and reset my mileage every time. The drive consisted of probably 95% highway, which a bunch of the highway drive was 35-0-35-0mph traffic on the way back and also in the rain with the AC turned on

Either way, the average mpg of all 4 fill ups was 30.2mpg!

Now, I'll be the last to bring up how much mileage my car gets. With more then double the stock horsepower along with injectors that are also more the double the size of stock injectors, mileage is about the last thing I care about.

However, I will say thats its a pretty good feeling knowing my car is still at the same fuel efficiency as I was stock (if not even better!). The best mpg I ever got completely stock was 29mpg!

I believe this is a testament to the efficiency of a turbo set up, a great tuner, and I will give credit to AEM's O2 sensor feedback. It was tuned in to run at 13.7 a/f under normal conditions and thats EXACTLY what it runs at. It truly is amazing.

Either way, I figured I would share this little tid-bit of information. I guess now we have to stop saying gas mileage is a "con" in a well tuned turbo setup huh?

 

Awesome! I averaged 19-24 supercharged.

 

Agreed -- it's not the turbo or S/C or the size of the injector... it's the pulse width of injector times injector size that determines air/fuel ratio (at a given throttle opening/load.)

Before I did ANYTHING on my S2000, the first thing I installed was an Innovate Wideband 02 sensor. I mapped the stock Honda ECU's settings. It was 14.7:1 solid all the way across the powerband, until you got to ~ 60% throttle wherein it moved to 12.5:1 solid. Hats off to the factory tuners IMHO.

So when I've tuned mine on the AEM (with turbo), I've run 15.3:1 for a little extra MPG at cruise (but religiously 11.5:1 anytime I'm in boost). The orig 11:1 CR motor handled this fine, but on my 9:1 sleeved motor it likes (runs more smoothly) 14.7 - 15.0:1 better (likely b/c 11:1 has more volumetric efficiency than 9:1). By the way, I knock down 29 - 30 MPG highway with 1000cc injectors on the 9:1 build, the old 11:1 build was good for 30 - 31.

Thanks,
Stanford

 

yeah, i finally setup o2 feedback and am doing a bunch of tests with different a/f numbers! The o2 feedback is very impressive! Since my turbo spools quicker since i got the 3inch DP and exhaust, i set boost compensation at 5psi, so when i give it partial throttle it doesnt kill my MPG!

Stanford, what percentage change did you setup for the feedback? and did you set it up for for boost as well as vacuum?

 

10% feedback and I only have mine controlled during vacuum although a high quality UEGO could control during WOT as well.

 

So what you are telling me is this....when I get tuned, I want a constant 13.7 cruise AFR, and an 11.5 at WOT for optimal gas consumption/performance?

 

This is good info John. When I get my next s2k I think I might be dealing with inlinePRO since they are only a few hours aways from me. My gas mileage when cruising use to be HORRIBLE... my tuner didn't know his ass from his elbow when it came to cold starts/idling/cruising... it just ran pig rich on the hwy.

 

Not bad, considering all turbos normally max out at 4mpg, pistons are the only way to lower compression, lowest under-hood temps is 800 degrees, lowest intake air temp is 700 degrees, and the power curve will quickly destroy the entire drive train.

 

Basically yeah

Although each engine / kit is slightly different but those A/F numbers are a good approximation.