Thread: Tuning for Gas Mileage

Vadim...ok I haven't even read one word of this entire thread...but you have it all wrong. You should be tuning for POWER! Forget mileage! Tear up the streets!!

(I'll read this later)

Dudeman

ever think about dyno tuning for the specifics you are looking for?

i do think gas mileage is important, but i do also agree with dude, tuning for maximum power is in the long run going to benifit all your supporting modifications that you do to the car, larger turbo,manifold,exhuast,more boost,ect tuned for power will benifit all aspects of the mods you will do to the car.

Of course, there's no reason you can't do both and no reason not to do both.

To get around the closed loop part, Innovate products, even there cheap LC-1, have 2 programmable outputs.

You can leave one the 0-5v WB02 curve, and then modify the other one so that 0.5v (what the nissan ecu looks for) be slightly over to the lean portion. That way you can watch the WBO2 output (with a gauge, or datalogger, or whatever) and have the nissan ECU be shooting for 0.5v on the narrowband channel, with 0.5v being closer to 16:1 AFR then 14.7:1.

Vadim I might be incorrect but it looks like you have lightened flywheel as a gas mileage improver, this is incorrect. Lower rotational mass technically allows the engine to use less energy to gain rpm. However when applied to a rolling body, of considerable weight, the added mass of a heavy flywheel helps to maintain the rpm due to its store of kinetic energy, working as a ballast if you will. If I read your post wrong my apologies.

Also, Ben is correct, you can and should tune the car to scream under wot, and have very good MPG (best possible regardless of wot) under your cruising and light boost/throttle positions.

Best of luck mate!

Dudeman

I did dyno and tune last time I hit the dyno. I plan on going for a good retune after everything is complete.




Exactly



Everywhere I've looked and read a lighter flywheel should increase MPG in the city, while should/could decrease on the highway. It did the opposite for me haha. Reason it should increase in the city because of all the starts and stops.



That's been my intentions since day one .

Right now she's pretty quick, but I will work on making more power. But while I'm at I want good gas mileage

Messed around with the timing, and I got 20.3 MPG. Looks like we got a winner.

I will post some more details with Nissan Data Scan logs

I'm comparing my logs, I had to first get rid of the uneeded data which led to the highway driving data, that's a pain of it's own hehe.

I'm taking one stretch of the log, which has the same speed limit, no acceleration or deceleration, basically a straight road run with cruise control doing it's job.

Base Throttle (TPS) voltage (as set on the car by me per FSM spec): 0.36v while max is 4.0V.
Gas: 93 Premium from Same Shell Gas station.

Base Fuel/Timing Map
Speed: 73.4
RPM: 3,250 +/- 50 rpm range
Throttle: 0.70 - 0.80
Timing: 30-33
Air Temp: 86

Fuel Map
Speed: 73.4
RPM: 3,250 +/- 50 rpm range
Throttle: 0.85 - 1.00
Timing: 20-28
Air Temp: 89.6

Timing Map
Speed: 73.4
RPM: 3,250 +/- 50 rpm range
Throttle: 0.50 - 0.70
Timing: 33-39
Air Temp: 80.6

Timing Map Run 2 (updated Map)
Speed: 73.4
RPM: 3,250 +/- 50 rpm range
Throttle: 0.84 - 0.96
Timing: 23-28
Air Temp: 96.8

What does this mean? Well multiple things...

• Air Temp has an affect of how wide open the throttle will be. Which makes sense because air is less dense, thus more is needed
• Leaner Mixture required a wider open throttle, thus less timing
• Barely Open throttle = More Timing = Better burn, which should technically show the mixture as bean leaner on the Wideband.
• Car seems to respond better to more timing over leaner mixture. Too much timing may cause the infamous knock.
  

id say this is why you see better gains with higher octane gas, when they lean out the mixture some then add in timing over a broad range of rpm, or at certain rpm....but to me the race gas isnt worth the price per whp and the added in timing with a leaner mixure over regular unleaded or premium isnt worth it to me.

also air temp is going to be a factor too with a few things, 1 placement of intercooler piping, obviously piping that is going to be closer to the turbo is going to heat up causing heat soak in your piping causing hotter air tempatures.

also intercooler is going to effect the air temp also, larger intercoolers that may not get heat soak as easily will have better changes of dispursing the heat soak air across a larger diameter core thus having lower the air tempatures and giving the charged air more cooling.

Yup hotter air, means less dense thus less air itself. I think this is why our friends on Gas Saving forums that run Hot air intakes don't see such good numbers. I personally gained about 3 MPG on my wife's car with a Flow Stack WAI over stock, and side gaped plugs.

Her Auto P11 hit 32 MPG on my vacation, usually it would hit 28-29. Now I haven't driven her car in the city to see if it's any better though...

Anyway, my IAT (Air Temp Sensor), is hanging right outside of the engine bay. It's not hooked up to anything yet, I wouldn't mind hooking it up but I don't care enough to drill a hole in my piping.

I have an FMIC, it's not too big, and seems to cool pretty well. I was touching the intercooler on the hot side and it felt warmish, while by the cold side it was pretty cold, I personally was impressed! I do have thermoblok spacers to help me fight heat soaking on the manifold level too .

Basically on my current setup I should be doing well over 30mpg, or at least I was on my sludge monster. I wonder if lower compression has much to do with the significantly lower numbers.