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Discussion Starter · #1 ·
Last night we took a friends new KB to the track to see what it can do. Needless to say it didn't perform. He had it dyno'd last week and it was something like 565/510, with A/F around 11.4 on top at 17lbs of boost.

At the track, I data logged some of his runs. The car would fall on its face the second half of the track. The first thing I noticed was that after 5000rpm's the MAF was pegged. (thats the first issue)

(For the second) He had the chip programmed to run without the BAP, again after about 5500rpms, the FPDM was maxed and the fuel pressure would drop off substantially.

Obviously, the 2 questions I have are: 1. How many of you have pegged the stock MAF with 17lbs? And what have you done to correct it? 2. Have any of you had success running the KB with 55lbs inj., at 17lbs. of boost, without using the BAP? If so, who did your tune?

Needless to say, he was frustrated last night. And is contemplating driving the car far distances just to get a chip burned and tuned on the dyno. I advised him, that when playing with KB's and that kind of power, that would be his best choice.
 

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lguerra1 said:
Last night we took a friends new KB to the track to see what it can do. Needless to say it didn't perform. He had it dyno'd last week and it was something like 565/510, with A/F around 11.4 on top at 17lbs of boost.

At the track, I data logged some of his runs. The car would fall on its face the second half of the track. The first thing I noticed was that after 5000rpm's the MAF was pegged. (thats the first issue)

(For the second) He had the chip programmed to run without the BAP, again after about 5500rpms, the FPDM was maxed and the fuel pressure would drop off substantially.

Obviously, the 2 questions I have are: 1. How many of you have pegged the stock MAF with 17lbs? And what have you done to correct it? 2. Have any of you had success running the KB with 55lbs inj., at 17lbs. of boost, without using the BAP? If so, who did your tune?

Needless to say, he was frustrated last night. And is contemplating driving the car far distances just to get a chip burned and tuned on the dyno. I advised him, that when playing with KB's and that kind of power, that would be his best choice.
ANyone who breaks ~500rwhp will peg a stock MAF, thats nothing new, when a MAF is pegged a proper tune can work with this and the car shouldnt be falling on his face.

As for the FPDM, we also know via datalogs it will also be at max duty cycle and this us where the BAP comes in. Even if the car is tuned to not use a BAP it has been shown that using the BAP will lower the duty cycle to safer levels. While not ideal it is a temp fix and will allow for a little more margin of error.

What kind of times did he get and at what ET? I have 540/502 and car ran a low of 11.97 and a best trap speed of 123 of stock non-aired down F1's in full road trim (spare tire and everything in tact) with a half tank of gas. My car pulled hard right to redline in every gear. A short while later I even found 2 fouled plugs, one in each bank.
 

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Discussion Starter · #3 ·
He times definitely indicate a car falling on its face. 11.7 @ 112. Not the norm, by any means.
 

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He has solid HP/TQ numbers and you said he has a good A/F. I just dont see how the car could be falling down, where was peak HP at? Can you post a dyno graph?

11.7 looks good to me for street tires but trap speed sure is low. What kind of Dyno were these numbers obtained from? What plugs/gap does he have in the car?
 

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Discussion Starter · #5 ·
Shadowgray03 said:
He has solid HP/TQ numbers and you said he has a good A/F. I just dont see how the car could be falling down, where was peak HP at? Can you post a dyno graph?

11.7 looks good to me for street tires but trap speed sure is low. What kind of Dyno were these numbers obtained from? What plugs/gap does he have in the car?
That was on Nitto's. And the trap is low, because it was falling on its face after half track. It's not my car, so I don't have the specifics with Dyno graphs etc. It was done on a Dynojet.

It just goes to show that Dyno numbers are only numbers and track testing is real world. I just asked in the initial post, to really see where the guys putting up strong numbers are having their cars tuned.
 

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lguerra1 said:
That was on Nitto's. And the trap is low, because it was falling on its face after half track. It's not my car, so I don't have the specifics with Dyno graphs etc. It was done on a Dynojet.

It just goes to show that Dyno numbers are only numbers and track testing is real world. I just asked in the initial post, to really see where the guys putting up strong numbers are having their cars tuned.
Yes, thats why I asked what type of dyno. The dynojet is notorius for not representing a real load on the car. While I definatly like the idea of a tune done by someone with full control on the dyno, I just drove 6 hours one way to get it done myself and when it was all said and done I had a great A/F, OK power but a car that was so herky jerky I put my old chip back in. If I were in his shoes I would do some road/track blasts and log some data and see if you can pinpoint the problem. Maybe he is having spark blowout under full load that he didnt ecnounter on the dyno?
 

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lguerra1 said:
Last night we took a friends new KB to the track to see what it can do. Needless to say it didn't perform. He had it dyno'd last week and it was something like 565/510, with A/F around 11.4 on top at 17lbs of boost.

At the track, I data logged some of his runs. The car would fall on its face the second half of the track. The first thing I noticed was that after 5000rpm's the MAF was pegged. (thats the first issue)
Mine peggs at 4700rpm. Its all default tables after it pegs (Chip and Tuner Specific) or some other form of extending the Range or lower the voltage the PCM sees, ie Different MAF or Sample tube in Stock MAF. Still Chip tuning is needed.

(For the second) He had the chip programmed to run without the BAP, again after about 5500rpms, the FPDM was maxed and the fuel pressure would drop off substantially. [/QUOTE]

IMHO 17lbs boost with stock injectors and no BAP it will fall on its face regardless of Chip tuning, Upping Fuel Pressure, etc. You need more Fuel Volume thru BAP or larger pumps. My KB setup @ 19lb boost with 55# injectors and KB chip tuned for injectors with BAP off Maxed the Stock Pumps 100% as low as 3720rpm in 3rd gear pulls. With Fuel Pressure falling off soon after around 4200rpm.

Obviously, the 2 questions I have are: 1. How many of you have pegged the stock MAF with 17lbs? And what have you done to correct it? 2. Have any of you had success running the KB with 55lbs inj., at 17lbs. of boost, without using the BAP? If so, who did your tune?

1. Lots of Folks 2. Some have, but I still believe none BAP or aftermarket pump Folks are maxing there Pump Duty Cycle. I have had Diablo tune, KB chip currently very happy with it and soon trying Autologic.

Needless to say, he was frustrated last night. And is contemplating driving the car far distances just to get a chip burned and tuned on the dyno. I advised him, that when playing with KB's and that kind of power, that would be his best choice.
 

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lguerra1 said:
Last night we took a friends new KB to the track to see what it can do. Needless to say it didn't perform. He had it dyno'd last week and it was something like 565/510, with A/F around 11.4 on top at 17lbs of boost.

At the track, I data logged some of his runs. The car would fall on its face the second half of the track. The first thing I noticed was that after 5000rpm's the MAF was pegged. (thats the first issue)


Although it is not the most ideal way to setup the system, the MAF saturation can be tuned around. However, the big drawback to doing this is as follows: the MAF is used to measure calculated engine load. Once the MAF saturates, the PCM can not effectively measure any further increases in load. So, if you tune a car on a dynojet (reduced load compared to street) and the air/fuel looks good, when you take it out on the street the car will run leaner. The reason for this is that the PCM can not see in further increase in load and therefore will add no more fuel. Now, a tuner can guess at what the difference in load is going to be and they might even be right on UNDER GIVEN CONDITIONS (i.e. atmospheric...) but if the conditions change (e.g. cooler, denser air results in more boost and therefore more load) the car will run leaner. The most ideal way to deal with this is a modified MAF that has greater full-scale range.


(For the second) He had the chip programmed to run without the BAP, again after about 5500rpms, the FPDM was maxed and the fuel pressure would drop off substantially.


Once again, this problem may not have reared it's ugly head on a dynojet due to the difference in load. He either needs bigger pumps or a BAP and a retune.


Obviously, the 2 questions I have are: 1. How many of you have pegged the stock MAF with 17lbs? And what have you done to correct it?


Everyone making approximatley over 500rwhp.


2. Have any of you had success running the KB with 55lbs inj., at 17lbs. of boost, without using the BAP? If so, who did your tune?


HAMMER's car was running a similar configuration at Epping FFW and mustered a [email protected] IIRC. Datalog of the car showed that his FPDM output was also maxed before his HP level peaked. So, it is possible to get a good tune with 55lb/hr injectors and no BAP but at these power levels (600rwhp+) the fuel pumps will be running full-out and there will be little to no margin for changing conditions. IMO, not an ideal situation if you want to keep your expensive engine together.


Needless to say, he was frustrated last night. And is contemplating driving the car far distances just to get a chip burned and tuned on the dyno. I advised him, that when playing with KB's and that kind of power, that would be his best choice.
Agreed.

MJ
 

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Discussion Starter · #9 ·
Dustoff,

Thanks for the info. I figured most everyone trying this same setup has run into the issues. That is why I asked. I personally think he will need to get it retuned and then use the BAP as well. As you mentioned, larger pumps are an alternative.

Living in the middle of the country and not having any tuner around here makes it a bit difficult. If he was on the east coast, I don't think he would have an issue. He has been contemplating taking it for a long haul to have it dyno tuned. Especially now that he know what is going on with the car.
 

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Discussion Starter · #10 ·
MJ
Thanks for the info as well. I think his start would be a retune with the BAP. If he can't get that right, then take it for the long journey with a dyno-tuned chip.
 

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lguerra1

You need to have a fuel pressure gage installed, if not already installed, to know what your fuel pressure is at WOT. The chip/tune has nothing to due with the BAP. The chip/tune only sets the fuel pressure required for the correct A/F ratio at WOT etc. The BAP only increases the the volume of fuel required for the correct fuel pressure at WOT. If the fuel pressure is dropping at WOT you need to increase the BAP setting CW. Also, your fuel pressure may be too low at WOT. What chip is he using?

AMB
 

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Discussion Starter · #13 ·
AMB said:
lguerra1

You need to have a fuel pressure gage installed, if not already installed, to know what your fuel pressure is at WOT. The chip/tune has nothing to due with the BAP. The chip/tune only sets the fuel pressure required for the correct A/F ratio at WOT etc. The BAP only increases the the volume of fuel required for the correct fuel pressure at WOT. If the fuel pressure is dropping at WOT you need to increase the BAP setting CW. Also, your fuel pressure may be too low at WOT. What chip is he using?

AMB
While he doesn't have an actual fuel pressure gauge, I was monitoring it through the FRP sensor on my NGS. And yes once the FPDM was maxed the fuel pressure would drop all the way to about 26psi. (way to low) His fuel pressure never would go above 40 or so.

His chip is a Diablo and is in dire need for a retune. He wants it tuned without the BAP, but I think the BAP is a good backup.

Predator, thanks for that thread. I forgot it was out there. There is a ton of good info in it.
 

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lguerra1 said:
His chip is a Diablo and is in dire need for a retune. He wants it tuned without the BAP, but I think the BAP is a good backup.
He can have it tuned for no BAP and still use the BAP, it will simply lower duty cycle.
 

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Long Shot

I saw the car last nite and fuel pressure was down to as low as 7lbs one time. If vaccum hoses to fuel pressure regulator were not installed correctly, loose or blocked then fuel pressure would drop. MAF would then try to richen mixture and go to 5v to try and add fuel. Just a long shot and my 2 cents. Good luck.
 

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Discussion Starter · #17 ·
Re: Long Shot

Stickshift said:
I saw the car last nite and fuel pressure was down to as low as 7lbs one time. If vaccum hoses to fuel pressure regulator were not installed correctly, loose or blocked then fuel pressure would drop. MAF would then try to richen mixture and go to 5v to try and add fuel. Just a long shot and my 2 cents. Good luck.
The vacuum line going to the FRP sensor, not pressure regulator, is fine. And the fuel pressure at 7 lbs was during a run with the stock calibration. He wanted to do one to compare between chip and no chip. The 2 obvious things were lower timing, and less fuel pressure. He was just frustrated at that point. The car is getting a new tune and hopefully everything will come out ok.
 
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