Well I put in my injectors a few months ago and have had my JWT in since then. It seemed ok milage but not totally good. I took out my JWT ECU and put in my stock ECU with 34 psi base fuel pressure like a week ago..Well not to sure what Tune I have, I did NOT boost once. Well 125 miles later and 7.2 gallons that equals 17.6 miles per gallon !?!?!?!....I did start the car a bunch of times just to drive up to work a mile away, and warmed up first but that really shouldnt really effect milage all that much...

Im really confused. My 02 sensors are brand New and my knock sensor is a year old..

Do I need a lower base fuel pressure ?? There are no gas leaks anywhere, Z32 MAF is still in the car, along with an AEM FPR, and 370's...I know guys running like 610's and 555's and are seeing pretty good milage. I have a feeling it has to do with my base FP. ??

Im gettin my 3" installed on Monday with my WB as well so ill know what my A/F is..
any help I would appreciate it..thanks

-matt

 

i always thought if you had the stock ECU and 370 injectors you needed to lower your base fuel pressure. not sure how low to go though.

 

you prolly need a wide band to see if your running super rich.
I'm running z32 maf, 500cc injectors and afpr/walbro. My milege isn't all that bad 20-21 mpg

 

That doesn't seem that bad for letting it warm up. How long do you warm it up? In all my cars my fuel econ drops 8-10MPG in the winter because of warming up and the extended cold start time. Maybe it needs a little tune but I don't think its too drastic.

 

hey just wait the wide band will tell it all.

 

Thats really bad considering everyone on here with boosted cars with 370's are all reporting 23-27mpg....and Im getting 17. Do I have to mess with the base fp when I took out the ECU

-matt

 

I averaged 21.5mph with my NA car probably 70% city 30% highway.... who the heck is getting 23-27 with a boosted car lol. The only time I got anything like 27mpg in my NA car is when I drive ONLY on the highway.

 

Seriously. I got just about the same. I guess I am usually driving hard so that explains some of it but 27 is what the Maxes got stock.

 

I will get a minimum of 20 mpg if i drive hard on one tank, with a fp of 49 psi (55psi when cold then it levels out)and the jwt ecu for the 370's and z32. And when i drive like a normal person or on the hwy i will get around 25mpg.

 

I run a stock ecu with 370cc injectors, I run 24-25 psi for base fuel pressure but I also have a FMU. Last time I drove all highway miles I got 26mpg and that was even with boosting coming from the exit lane to the interstate

 

Are you running a Z32 MAF ?? what disc FMU are you running ??

-matt

 

With my 550's and z32 MAF I get bad gas mileage, never actually calculated it but it is bad enough I can notice it between using my JWT ECU.

When not having an ECU programed for the larger injectors you can tune to get your WOT AFR's to be decent and maintain a stoich AFR at idle and cruise, but part thottle accelertion and low rpm (non-boost) AFR is very rich. That is a down side of using a hack set up like this.

This was very evident when I was on the dyno last comparing my JWT ECU and stock ECU.

A normal dyno will show the AFR's staring high, at like 14:1 and dropping down to the desired 11:1 - 12:1 area as boost comes on. That is how my JWT ECU AFR's looked. With the stock ECU as soon as the car was WOT the AFR's went to 10:1.

Here is a comparion pic to show you what I mean





Alsom, when I had a WB hooked and monitored my AFR's while just cruising around, my partial throttle AFR's went off the charts rich. This is a side effect of not having a real proper fuel management set up. Sure, you can get larger injectors and a Z32 MAF to work and be safe, but things like partial throttle AFR's will suffer.

 

A32 MAF, and a 4:1 disc

 

hell i get 27 on the Interstate and driving a little rough with boosting some in fifth with 370cc