Although the title states SL55 Fuel Pump, this thread should be all encompassing for our fuel system. Lets discuss.....

Brief History:
After having a wideband a/f gauge installed about 1 ½- 2 years ago, I noticed a slight leaning out issue in the top of 3rd @ 5200 through redline. This issue would get significantly worse as the ambient temps dropped, winter months a/f went into the 17-18 range. Believing it was a tuning issue, I received several updated tunes and none corrected the issue. Then I thought since it isn’t a tuning issue, it has to be something mechanical with our fuel system…….Fast forward

Present Day:
I purchased and had an SL55 Fuel Pump installed in preparation for the Dallas Tune Day. The-6 was tuned and all leaning signs in the top of 3rd @ 5200 through redline disappeared. I was then asked to make a 4th gear run to redline too validate no lean issue would be present. The results in 4th gear @ 5300 were LEAN, LEAN, LEAN, LEAN, LEAN and did I say LEAN! I never made it to redline because once I saw the a/f, the foot was removed from the accelerator. However, I did make several 4th gear runs on different days and they all ended with a 16-17 a/f.

Theory:
The SL55 Fuel Pump was able to correct the 3rd gear leaning issue because it flow’s more fuel than the stocker with less pressure. To assume that it doesn’t because none of the fuel flowing orifices have changed is faulty logic. That would mean the stock fuel pump flow was maxing out the current fuel path, which is not the case.

The SL55 Fuel Pump is able to flow more with less pressure on the OEM regulator, preventing the bleeding off of fuel in 3rd. However, in 4th gear I assume the pressure being produced by the SL55 is equivalent or greater than the stocker in 3rd gear. This is why the same leaning condition in 4th presents itself with the SL55 Fuel Pump, the regulator is being taxed and bleeding necessary fuel back into the fuel tank. Moral of the story, I think we need a better fuel pressure regulator.....

 

I asume you didn't read XRAY's and needswings fuel fix for lean afr... well here it is jim
https://www.crossfireforum.org/forum...od-update.html

 

I sent my ecu to Tony yesterday to be retuned because it is running so rich. He asked me to do a 4th gear run as part of the logs. In 4th gear the leanest it got was 12.6 and at 5800 rpm's when I got out of the gas it was at 12.3. If you would like me to send you a copy of the log PM me and I will email it to you.

 

Very nice xray, 12.6-12.8 sounds just about perfect...

 

Works for some but not for all. And this was supposed to be THE DEFINITIVE FIX. Glad i didnt spend the $325+ now.

Maybe is something about TX.

 

Glad to see NW/Waldig has the answer for us guys with the bigger pullies. Maybe there will be an actual advantage to having a bigger pulley now.

 

Just remember size matters

 

Man, WTF have you been?!?

 

240,

Did you go with a similar FPR setup? or just the Walbro in place fo the OEM Fuel Pump?

 

I've been lurking from time to time, just hasn't been anything significant till this possible lean fuel fix.

 

I replaced the stock fp w/ a single Walbro 255 over a year ago and am still running it that way(it still goes lean w/ the 181). I did the return style setup and FPR and it helped the top end lean condition but it was too rich down low. The NW/Waldig method looks interesting so im waiting on a price and a few more reviews. Personally to this day i still think my car (and GangMembers) needs bigger injectors.

There was a guy at the Dallas Eurocharged tuning session running stacked pullies, sl55 pump and bigger injectors. He claims he never ran lean but ive noticed over the years some people say their afrs are fine then later run lean under heavy loads.

 

yeah I heard about the SL55 and Bigger Injectors. however, if he didn't change the FPR seems like that still may be a choke point in fuel delivery even if he does have bigger injectors with higher capabilities.

i'd def be interested in some similar setup that didn't require a zeitronix to accomplish... unless it would just need to be programmed by the z and not monitored 100% of the time.

 

You need to data log your injector duty cycle to rule out the possibility that the ECM is not asking for enough fuel. If the duty cycle is at/near 100%, then the ECM is doing all that it can in requesting more fuel and no tune in the world is going to improve that situation.

Next up is to monitor fuel rail pressure while the afr is going lean. If rail pressures drop, then you do not have enough pump. If pressure stays constant, then pump capacity is not the issue.

 

If you look at the chart in the following post, it clearly shows that the SL55 pump has plenty of capacity (with stock injectors). In fact you can run as much as 90-100 psi (if you could adjust the FPR this high) and the pump will still keep up:

https://www.crossfireforum.org/forum...el-system.html

That being said, I think the lean issue (edit: if you have an upgraded pump) lies with the ECM not commanding enough injector duty cycle, until I see some logs which prove me wrong.

 

I am logging fuel pressure and it does drop off which is why we are using the sc boost to increase fp as afr's go lean.

 

My AFR ratio's from wayne's tune 4 gear pull on dyno[/IMG]
it should be readable this is with the SL-55 pump

 

Out of curiosity how many miles on the car. I'm thinking maybe the fuel filter is getting dirty, I have 3000 miles on the SRT and posted the AFR' from the tune

 

I’m approaching 40k, however the filter/regulator was changed 1yr ago, same problem before the OEM replacement. You’re not going to see the lean condition on a dyno no matter what. I never ran lean on the dyno and I have done 12 pulls. The reason is you’re getting significantly less air flow on a dyno.

The NW solution is interesting but requires too much “additional” hardware and a half/ half tune to correct the bottom end a/f. Does anyone know what size injectors we have? Anyone every had them flow tested? How do you measure duty cycle on a datalogger?

The gentlemen at the Dallas Tune Date had 48lb injectors and an SL55 Fuel Pump, WAY TO MUCH injector for what we need. That’s why he runs rich on the dyno and on the street.

 

Was it Eurocharged that did the tuning? When the snow disappears I'll do some data logging again, my question is what did the dyno show your afr to be on the 4th gear pull, mine is about 12:1 at the exhaust which is closer to 11.5 at the engine. What was your AFR on the Dyno in 4th gear.

 

If the FPR can't maintain regulated pressure, then the pump capacity is insufficient to keep up with the demand. That is why pressure is dropping. You need more pump.