Fuel Tuning

[DKneble]

Hey All,
Just finished upgrading the fuel system and trying to tune it all out on DSM Link. The car is a 2g GSX with a built 6 bolt swap. Im running a Gt35r and the supporting mods for it. Fuel system is walbro 255 intank with bosch 044 inline. -8 Line up to the AEM rail and Aeromotive Blacktop regulator. Currently im flowing 850 cc injectors.

Once I installed the new pump I found that the regulator is no longer able to hold the pressure down in the 42-45 psi range. Pressure with the vac line on can be reliably held at 50-51 psi however which with the vac line off puts the pressure at about 53-54 (only pulls about 8 in hg at idle because of cams). Since I'm running the higher FP, that should change (by my calculations) the flow on the injectors from 850cc to about 930cc.

Now, my question is, should I adjust the dead time in addition to the fuel trims or simply the fuel trims?

I tried just adjusting the global down to -53 instead of -47 which would treat the injectors as if they were 950's and keeping the dead time at 330 but the car stutters under throttle, seems like its way too rich. Then I tried turning the dead time down and at about 205-225 it seems to run great. Is this pretty much a trial and error situation or is there a calculation I can go threw for the dead time and global when flowing a higher fp. Thanks in advance

 

[Talesin]

Fuel pressure shouldn't affect the global deadtimes. I'd be concerned about the FPR install though, if it can't hold pressure at any given level. Most likely a sign of another problem... either how the FPR was installed, a leaking o-ring on the in-tank pump... don't think you'd need the Bosch pump for 850s. In fact, that could be why you may be overrunning the AFPR. I'd consider getting a larger-flow FPR, or ditching the Bosch outright.

 

[DKneble]

Planning on bumping up to 1000's sometime this summer and I got the bosch due to the numerous recommendations by individuals on this forum as well as SBR and jayracing. It works well in conjunction with the 255 and does not have the tendency to overheat on long trips like the A1000 which I had originally purchased but then returned. I am looking to run 30-33 psi on the GT35r and thus putting down around 600awhp, which the walbro 255 cannot handle alone. Anything above 23-24 psi on the turbo and the fuel leans out. The walbro and Aero FPR were both installed professionally (prior to me starting to do all the work on my car) and I have double checked the install of both and everything is in order. I am almost 100% positive that the overrunning of the fpr is because I am still running the stock return line...eventually I plan to replace it with -6 back to the tank but for now I want to get this running decent. There is no reason, theoretically, why the car shouldn't be able to run just as hard on 50psi as it does on 43.5psi as long as the right adjustments are made to injector pulse width and fuel map.

From just doing some playing around on DSM Link it seems like maintaining the global setting of -47 works well with the higher FP. However, the deatime of 330 bogs the car out horribly. Dropping the deadtime down to around 195-210 seems to work wonderfully for both idle and WOT. The only other changes it looks like I will have to make is to lean the rest of the map out about 5% for WOT. Is this ok or is there something seriously wrong here? Thanks

 

[DKneble]

Doesnt't seem like anyone was jumping at offering advice on this one but figured I'd give an update anyway.

Car was running horribly in between shifts due to the increased FP and overall just not the same so I bit the bullet and bought some -6 line and ran an all -6 stainless line back to the tank. Problem is solved and so for anyone who looks to run the 044 in conjunction with an intank 255, be prepared to upgrade the return line.