Thread: fuel consumption - where did I read this!?!?

I was running a jwt ecu tuned for a t25, 370's bored maf and 4 bar fp. I did go on the dyno and do some leaning out/tuning with an afc on top of the jwt ecu. I also was running a 2.5 in catless mandrel bent exhaust.

I am not sure on that but for 90-$100 i would just buy a walbro to be on the safe side.

The car was set to a little over 4bar with a nismo fuel pressure regulator. Yes then I ran 7psi of boost all on 259cc injectors and stock fuel pump in my p11. I got 28mpg all day long in the summer and hit a high of 34mpg on a trip from NJ back to CT.

Before anyone says the car won't last long like that let me say I bought the car at 60k, turbo by 64k, daily driven until 218k and sold it working perfect. I did swap to a walbro toward the end because of an engine cut out problem I was having. It was a waste though because it turned out to be the MAF.

Stock fuel pumps work better than most believe. If you're going with a simple small frame turbo setup, the stock pump is absolutely fine. The stock pump has been known to support 370's at 4bar of fuel pressure. Proven by quite a few in the field.

I know of a couple people that would take them even higher than 4bar base fuel pressure and have had no complaints.

Build a pressure tester and find vacuum leaks.

Send injectors to RC engineering for ultrasonic cleaning. They will perform BETTER than new when you get them back.

Replace your stock fuel pressure regulator. Sometimes the diaphrams wear and vacuum will not function properly.

Check your ignition timing. Should be 15~17* advance, 86~88 octane rating. (I know you're in OK.)

If stock ECU, Nissan runs their maps a bit lean IIRC. A bit too lean means a bit worse gas mileage, just like running too rich means worse gas mileage. I've seen stock ECU's run around 16~16.5:1 AFR's, which is too damn lean no matter how you look at it. 15.5 or thereabouts when cruising is the optimal AFR IMO. You're mileage will jump greatly.

Interesting Cliff, can you explain why a lean running car 1:16-16.5:1 will be more efficient on a richer mixture but no too rich?

There's a "happy medium" in which fuel burns most efficiently (around 15.3~15.6 AFR), while cruising. Too lean a mixture will have the car struggling to make the same power, which means more fuel/air is required in order to burn to make the power. Too rich of an AFR in cruising (like constant highway speeds) would obviously mean lower MPG.

I think it may vary per car, I personally got pretty good gas mileage at 16-17 when my O2 died.

i set my cruise to around 15.3 to 15.5 air fuel in cruise to about .93kpa and inot only my gas was better but my car spooled ALOTquicker the hotter exhaust gases move with a faster velocity which results in faster spool it was like night and day