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Discussion Starter · #1 ·
I had my car retuned yesterday at a different facility and was told under boost the fuel pressure is not increasing and causing a dip in my tq graph. It doesn't increase on the dyno, but on the streets, it goes from 30 psi to 55 psi under boost. WTF?

KB said to hook up the BAP. I have the Diablosport chip. I hear adding the BAP will not increase fuel pressure with a Diablo chip, but will with the KB chip. Diablo's chip correct pressure in a different way to get correct A/F ratio, I guess. The car was tuned by Willie at Diablosport's facility, so I realy doubt it's the tune. (They feel it's something else going on and not the tune) If the chip can't increase pressure, what could be the issue? Or the fix?

We can't get the dip out of the tq graph with tuning. It's fine up to 3000 then dips at 3500 then back up again and down. WTF?
 

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How did the second dyno place know what the FP was doing? Did they datalog? You say the torque dipped, did the a/f go way off at the same time? Where thay actually tuning the car, or just doing some verification pulls? If they were tuning it, where they guessing the fp was f'ed becuase they couldn't get the a/f where they wanted it?

If it is true that it is going up ont the street and not on the dyno that is a weird problem.

I think a "real" chip guy will have to answer. I think there are different load tables, I guess it is possible to be on one load table on the street and a different load table on the dyno, but it seems like a long shot that the FP is changed in one load table and not the others.

I guess it is possible since the actual volume of fuel needed is higher on the street ( at least in the higher gears) that you may be running out of pump there, but not on the dyno. It seems like a long shot that you are using just enough extra fuel to make the fuel pressure stay the same.

What injectors, and how much boost?
 

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Snake Charmer
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Dv8tor said:
I had my car retuned yesterday at a different facility and was told under boost the fuel pressure is not increasing and causing a dip in my tq graph. It doesn't increase on the dyno, but on the streets, it goes from 30 psi to 55 psi under boost. WTF?

KB said to hook up the BAP. I have the Diablosport chip. I hear adding the BAP will not increase fuel pressure with a Diablo chip, but will with the KB chip. Diablo's chip correct pressure in a different way to get correct A/F ratio, I guess. The car was tuned by Willie at Diablosport's facility, so I realy doubt it's the tune. (They feel it's something else going on and not the tune) If the chip can't increase pressure, what could be the issue? Or the fix?

We can't get the dip out of the tq graph with tuning. It's fine up to 3000 then dips at 3500 then back up again and down. WTF?
Post the graph if you can and also give us more specifics on your setup. What inj you running? Is the BAP even installed?
 

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Discussion Starter · #5 ·
JT said:
How did the second dyno place know what the FP was doing? Did they datalog? You say the torque dipped, did the a/f go way off at the same time? Where thay actually tuning the car, or just doing some verification pulls? If they were tuning it, where they guessing the fp was f'ed becuase they couldn't get the a/f where they wanted it?

If it is true that it is going up ont the street and not on the dyno that is a weird problem.

I think a "real" chip guy will have to answer. I think there are different load tables, I guess it is possible to be on one load table on the street and a different load table on the dyno, but it seems like a long shot that the FP is changed in one load table and not the others.

I guess it is possible since the actual volume of fuel needed is higher on the street ( at least in the higher gears) that you may be running out of pump there, but not on the dyno. It seems like a long shot that you are using just enough extra fuel to make the fuel pressure stay the same.

What injectors, and how much boost?
They see the fuel pressure by looking at my fuel pressure gauge.

They are not looking at A/F ratio. I was told reading A/F data from the tail pipes is not an accurate reading of what's going on in the combustion chamber.

They downloaded a few different files from diablo's site and tried them, but they are primarily verification pulls at this point. They are only taking the rpms up to 4500 until we get it looking good on the graph, which I feel is very smart.

They can't figure out why the torque dips a few times to 4500 rmp, so they're looking at FP.

Stock injectors. The car made more power with the 15 psi pulley then it does on this 17 psi pulley. That's why I'm looking into what's going on with the car.
 

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Discussion Starter · #6 · (Edited)
Well... The shop worked on the car for a few more hours today and this is what's going on.

After hooking up the boost a pump, the fuel gauge is seeing more pressure, but it still gets dips in the dyno graph. We took OUT the Diablo chip and the car makes more power, at this point. We made 501 rwhp 580 [email protected] 4500 RPM with just the BAP. (Was told it's not lean due to the BAP) At this RPM, the rwhp is up 40 and the torque is up 100. They are trying to get the graph to look good at 2000-4500 rpm before taking her up to 6200 RPM, which I think is very smart.

The boost bypass valve is loose too and will be tightened down Thursday. The bypass might be leaking hot air in under boost and causing my power loss. We'll figure out what to do with the chip tomorrow.

The car does not like to be hot either. 1 pull on the dyno is good, but the temperature in the motor gets to 201 on the second pull and the dips in the dyno show bad. ...And the pull was only to 4500 rpm! Why am I in Florida??? I'll put a 160 thermostat in tomorrow too.

In summary: The car makes more power and a smoother graph with a BAP and no chip, at this point. We'll play with the chip on Thursday and see if the Boost bypass valve fix will help.

Shadowgray03, thanks for the info and you're correct. So far with the BAP, the graph looks a tad better, but very similar with or without the BAP with the Diablo chip.

Thanks for the help guys.
 

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Discussion Starter · #7 ·
Re: Re: Fuel Pressure with KB Issue

Shadowgray03 said:
Post the graph if you can and also give us more specifics on your setup. What inj you running? Is the BAP even installed?
I have the graphs, but don't have a scanner a home, I'll post them tonight if I get to the office on Thursday.
 

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Why didn't you use/get the KB chip. You need to get the fuel pressure up to about 70psi at WOT. Diablo doesn't seem to be able to do that yet. The BAP will not increace the fuel pressure itselve. It only supplies more volume of fuel. The chip/program only can increase the fuel pressure.

AMB
 

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I would be very skeptical if your tuner is NOT looking a/f ratios and your engine temperature spikes that quickly. Be very careful....
 

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AMB said:
Why didn't you use/get the KB chip. You need to get the fuel pressure up to about 70psi at WOT. Diablo doesn't seem to be able to do that yet. The BAP will not increace the fuel pressure itselve. It only supplies more volume of fuel. The chip/program only can increase the fuel pressure.

AMB
I dont think its a matter of not being able to do, as a matter of fact I know they can do, I think they just tried to come at it differently. Relying on a pressure increase as KB does causes drivability issues at least on cars with stock inj. As MJ has commented in the past, the feedback loop on fuel pressure is a bit slow to respond.
 

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Discussion Starter · #11 ·
Day 3 of tuning:
After trying many different tunes, the car sees 70 psi of fuel pressure now, but is running out of injector. They took the car up to 5000 rpm, before seeing it run lean. The car made 526 rwhp and 617 torque at under 5000 rpm. This is on a Mustang Dynometer, which usually dyno's a little lower then say a dynojet. I have 55# injectors on the way and hopefully, that should do it. Hopefully, the car will see 570ish rwhp and 610ish torque, which is right around where it should be.

My graph is still not smooth, so I'm not sure what to make of that , but the car runs stronger now. Definately. I'm not taking it over 5000 rpm though until the 55's go in next week.
 

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Dv8tor

I run my KB at 20psi with stock injuctors and the BAP set st 20% with a WOT fuel pressure of 70psi and a A/F ratio of 11.5.

AMB
 

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Dane,

I'm sure once you get those injectors in you'll see full potential...it made some really nice numbers for being on a mustang dyno and not being able to take it all the way up.

Where did you find the injectors?

Cant wait to see you're final results.

I want that much power;)
 

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AMB said:
Dv8tor

I run my KB at 20psi with stock injuctors and the BAP set st 20% with a WOT fuel pressure of 70psi and a A/F ratio of 11.5.

AMB
20lb boost, stock injectors and the BAP set to 20%....

With 20lbs boost and the BAP only set to 20% what is the duty cycle on the pumps above 4500 rpm ?

Have you data logged this beast on the Road pulling WOT and holding fuel pressure to 70psi or just on the dyno.

Not meaning to flame or start nothing. I guess with the stock injectors and not 55lb injectors. You are able to hold higher fuel pressure for higher RPMs and the pumps do not have to work as hard as it would feeding 55# injectors.

It just seems there is no margin for error with 20lb boost and stock injectors.

JL
 

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I have a Wideband A/F ratio meter, a fuel pressure gage and a boost gage. I hold 70psi fuel pressure at WOT on the road.

AMB
 

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Discussion Starter · #16 ·
AMB said:
Dv8tor

I run my KB at 20psi with stock injuctors and the BAP set st 20% with a WOT fuel pressure of 70psi and a A/F ratio of 11.5.

AMB
That's great! Unfortunately, my car wouldn't do that. Diablo tried tweaking the chip, but couldn't get it to richen up over 5000 rpm. Most people I see running 19+ psi have 55 injectors anyways, so I'd rather be at like 60-80% on 55 injectors than running them at 95-100% on the stock injectors.

What numbers are you making?
 

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I have a very safe tune, because of the 91 octane gas here in CA. I have 525 SAE RWHP with 16psi boost. I am going to dyno at 20psi this Saterday.

AMB
 

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I am running 60 psi fuel pressure at WOT with a Diablo tune by Patrick. With 3" 17# pulley and the injectors at stock duty cycle my car was running very rich at this fuel pressure and Patrick "lowered" the duty cycle to lean it out to 11.5 a/f.
 

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Discussion Starter · #19 ·
toofast4u said:
I am running 60 psi fuel pressure at WOT with a Diablo tune by Patrick. With 3" 17# pulley and the injectors at stock duty cycle my car was running very rich at this fuel pressure and Patrick "lowered" the duty cycle to lean it out to 11.5 a/f.
Nice, Brian. I guess Patrick was able to get your car tuned correctly that way. If it's running good, don't mess with it. That's awesome.

Derick's car is apparently not making the fuel pressure either, so he needs the BAP too. He already has the 55 injectors though. Patrick tried to richen mine up, but with no luck. They played with the tuning for 3 days too.

A Mustang Dynometer simulates car load. Maybe that's why they see it leaning out a little with my car. All I care about is that I want the car to make the numbers it should and it wasn't, but the car definately runs stronger now for sure! The$e guy$ really want the car to make good power and are taking the time to figure thi$ i$$ue out. <-- notice the "$" in that last sentence?

Although the dyno is showing a gain of 133 torque so far, I'll wait until I dyno where I did before to really compare numbers to numbers.
 

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KB FUEL PRESSURE

Dv8tor

I went to the Dyno Saterday. I had the same problum as you did. My fuel pressure went from 70psi to 30psi with the BAP set at 20%. I upped the BAP to MAX and it still went to 50psi at WOT, witch leaned the A/F ratio down to 13.5. That was with a tune for my 16psi boost by FORDCHIP. I put my KB chip back in and the Car feels mutch better know on the street. I did not have the same trouble on the street as I had on the Dyno. I beleive the problem on the Dyno was that the fuel pumps could not keep up with the rapped RPM increase of the Dyno. I will Dyno it again the next time they have a Dyno Day. I got 585tq; but only 550hp. I shoud be getting over 600SAE RWHP with that torque.

AMB
 
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