GT35+AEM+264's = Good pump gas Dyno

[IJ.]

What pump?

 

[Supraholics]

Thanks for your reply! :sarcasm:

I was just wondering if it was GTEpowered worthy since you have the HP. I guess I won't be seeing you application anytime soon...

Can you post some pictures as well? I don't think I've ever seen your car or your engine bay.

 

[suprahero]

:biglaugh:

 

[X-man]

I love this tech talk.
My base fuel pressure is at 41psi. That is with the vacuum connected to the fuel pressure regulator.
Also, I'm reving out to about 6900rpm's on the dyno. AFR's were mid 11's and higher with some lean spots we could not get rid of. We then realized I was running low on fuel, so I put about 5 gallons in and got the AFR;s better, although I left with 10.8 AFR's. The injector duty cycle was still over 90%.

Check your fuel psi with the vacuum line off and the engine idling, but if it is at 41 psi with the line on and idling it should be around 44 psi or more with it off which is fairly high base fuel psi. Most stock foreign systems seem to be around 36 to 40 base which would put them in the low 30's running with the line on. A 10.8 air fuel ratio is pretty rich. That along with conservative timing will effect the duty cycle. I usually put customer cars at 11.5 to 11.7 to be safe and I run mine at 12.0 with timing that is 7 to 8 degrees more advanced than where yours is at.

How are you checking duty cycle and how is driveability?

Sean

 

[MRSUPRA]

"Thanks for your reply!"

Easy buddy. It seems like I go through a new computer every 3 months and lose everything. Let me wash my car and I will get some new pics.


AS for the pump, it's just a single Walbro.
I jacked up the fuel pressure when I first got my 264 cams trying to get them to idle. I never got around to turning it back down. Yeah I would guess that it would be even higher (measuring the proper way) with the vacuum line not connected.

I never had a chance to see, but Sal was telling me that the AEM was showing over 90% duty cycle.


As for drivability, two main problems are that it does not want to idle on a cold start. And the other problem is that it goes lean for an instant when you accelerate form a low RPM which makes it feel just a tiny bt slugish when driving very slow. Other than that, its fine.

 

[IJ.]

Wonder if you're just running the pump out of fuel and the injector duty cycle is maxed trying to compensate?

Whatever it is it's NOT safe I'd be turning the boost down some and WOULDN'T run it that hard in the real world,90% is nuts.

 

[MRSUPRA]

Well, I made around 490rwhp on the dyno on my old setup with 550cc injectors (with the stock ECU) and the same pump before I started going lean.(Not sure if the airflow meter was maxing out).
If the fuel pump is the problem, will the fuel pressure drop off under boost? Is that something to look for?

 

[IJ.]

I'd expect to see a pressure drop as the pump runs out of puff.

Rule of the thumb I use is roughly double the pump volume for the hp expected (lost a motor to a leanout way back and don't want to risk it again)

 

[tissimo]

Fuel pump is running out of steam. They usually start to max out ~ 500, more if you remove the banjo fittings through the fuel system, but not much more then 550whp can be run on a single walbro safely imo.

 

[X-man]

Fuel pump is running out of steam. They usually start to max out ~ 500, more if you remove the banjo fittings through the fuel system, but not much more then 550whp can be run on a single walbro safely imo.

We just made 622 rwhp on a single Walbro 255 with 680 cc injectors on an RB26DETT and 528 rwhp on a KA24DE with a single Walbro and 680's. I have a 91 Supra in my shop that I have made 510 rwhp with 680 cc injectors on a single 255 Walbro also, so I wouldn't think the pump would do it. These results were done with stock fuel lines and the Supra just had the J bracket and the fuel pump resistor removed. The RB had the stock fuel pressure regulator still on it.

Sean