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post #1 of 23 Old 02-05-2007, 01:23 PM Thread Starter
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Fuel Pressure issue

Ok guys I need some suggestions. I have searched and found one member that had a very similar issue but the thread was never followed up on and he is not returning my PMs. I have a mild 302 with a B&G single setup. I have a 255lph in tank pump, stock fuel rails, 42# injectors (new), BBK regulator, and a blow thru promass 3inch pro tube mass air meter that is supposedly calibrated for the 42's (bought new through JD's performance). My problem is that I have to run very close to 70psi fuel pressure at idle just to get the afr down to low 15s high 14s. Car idles fine and runs great but I dont want to continue to run this elevated fuel pressure. Is this a sign that the meter is calibrated incorrectly? or could it be the intank pump dying (it maintains about a 10:5 afr in boost), or could it be the BBK regulator (I know its not boost referenced but as mentioned before its holding a good afr in boost.) Currently the car is running on the stock a9l with no tuning of any kind. I need some suggestions before I just start throwing parts at it.

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post #2 of 23 Old 02-05-2007, 03:17 PM
 
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Originally Posted by chevyrcr View Post
Ok guys I need some suggestions. I have searched and found one member that had a very similar issue but the thread was never followed up on and he is not returning my PMs. I have a mild 302 with a B&G single setup. I have a 255lph in tank pump, stock fuel rails, 42# injectors (new), BBK regulator, and a blow thru promass 3inch pro tube mass air meter that is supposedly calibrated for the 42's (bought new through JD's performance). My problem is that I have to run very close to 70psi fuel pressure at idle just to get the afr down to low 15s high 14s. Car idles fine and runs great but I dont want to continue to run this elevated fuel pressure. Is this a sign that the meter is calibrated incorrectly? or could it be the intank pump dying (it maintains about a 10:5 afr in boost), or could it be the BBK regulator (I know its not boost referenced but as mentioned before its holding a good afr in boost.) Currently the car is running on the stock a9l with no tuning of any kind. I need some suggestions before I just start throwing parts at it.

I would advice to at least buy an inline pump. BBK inline or a T-Rex external pump to help out that 255 lph pump. With this pump you should be able to bring the fuel pressure down to 50 psi at idle. Your A/F is rich when in boost. I would run it at 11.5 at wot.

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post #3 of 23 Old 02-05-2007, 04:40 PM
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how much straight pipe before/after the MAF and what size is the pipe??


A tune would settle all your problems.
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post #4 of 23 Old 02-05-2007, 08:44 PM Thread Starter
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I would advice to at least buy an inline pump. BBK inline or a T-Rex external pump to help out that 255 lph pump. With this pump you should be able to bring the fuel pressure down to 50 psi at idle. Your A/F is rich when in boost. I would run it at 11.5 at wot.
I know I will need to add another inline pump when I turn it up but do you really think adding a pump now would help at idle? I wouldnt think that the 255 could keep the car rich in boost and not supply enough fuel at idle?

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how much straight pipe before/after the MAF and what size is the pipe?? A tune would settle all your problems.
My meter is in the charge pipe that goes from the intercooler inside the fenderwell I would say there is about 12 to 15" straight pipe on either side of the meter. Brian @ b&g supplies this as a solid pipe and you have to cut it to add the meter. I tried to center it the best I could between the bend from the intercooler and the bend where the pipe goes through the apron and was aware that I needed some straight pipe before the meter.

I know I could prob tune around this issue, and I'm going to buy a tweecer in the next few days mainly to tweak the maf transfer, however my concern is that if the meter is actually calibrated incorrectly will that have any negative side affects in the top or bottom of the flow range? I am going to have a big enough learning curve with the tweecer so I would like to figure this issue out before I start as I believe it is hardware related.
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post #5 of 23 Old 02-06-2007, 03:33 PM
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how did you find out the bbk was not boost sensitive? i'm getting conflicting info even from bbk.

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post #6 of 23 Old 02-06-2007, 08:19 PM Thread Starter
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how did you find out the bbk was not boost sensitive? i'm getting conflicting info even from bbk.
I not so sure myself like you I keep seeing conflicting information, and unfortunately I dont have a gauge to monitor fuel pressure while in boost but I took this straight from BBK's website

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Q. I put a supercharger on my Mustang, but when I hooked it up to the fuel regulator, the pressure stayed the same. Did I do something wrong?
(part numbers affected include: 1706, 1707, 1617)

A. The BBK Fuel pressure regulator is not a Boost Referencing model, meaning that forced induction systems will require the use of an FMU (Fuel Management Unit), usually supplied with the supercharger kit.
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post #7 of 23 Old 02-07-2007, 04:59 AM
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i don't know if the stock one is boost sensitive, is the bbk boost sensitive?
tks,
rob


Quote:
Originally Posted by BRYAN ROGERS
Quote:
Originally Posted by rob
i have a 87-93 forced induction car with a bbk adj fuel pressure regulator.

i've always been under the impression that these were boost sensitive (1:1).

read a post and somebody mentioned the bbk reg is not boost sensitive.

is this reg boost sensitive?

tks,
rob

The BBK reg. works exactly like a stocker, but with an adjustment screw for those who need more than stock pressure.

Bryan


The boss man says it's 1:1 and not designed to be boost sensitive.

Bryan

yeah i saw that on their sight too. so i pm'd bryan from bbk and the final answer is on the bottom of my cut and paste.
he says its 1:1 then says its not boost sensitive. i guess i'll just get a kirban, i hate the aeromotive.

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post #8 of 23 Old 02-07-2007, 06:31 AM
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stock is boost sensitive.. I have had a aeromotive on my car for 2years with no issues so far but I would buy a kirban IF I was buying another. I NEVER had good luck with ANY BBK part.
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post #9 of 23 Old 02-07-2007, 06:56 AM
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255 lph intank pump is more than adequate. I would not go with an additional pump. There is a problem. You should be running 40 psi vacuum off then connected at idle with no problem. I would at least temporarily put in a mechanical fuel gauge. I have mine on the hood in front of the windsheild. They cost like 35 bucks. If you have stock injectors in there with the stock MAF, do you also need to have the fp high like that? Are you sure what you are measureing the a/f with is correct? Sounds like you have your maf set in there nicely. When I had my car tuned, my pmas 75 mm was on the lean side. I had my fp at 45 vacuum off. Bottom line is you should not need that much fp to idle. If you back off on the fp, does the car idle poorly? My car was reading about 12.5-13 at idle. They go somewhat lean NOT under load as the rpms go up. But as soon as you hit wot, you should be down around 12-11.
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post #10 of 23 Old 02-07-2007, 07:38 AM
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stock is boost sensitive.. I have had a aeromotive on my car for 2years with no issues so far but I would buy a kirban IF I was buying another. I NEVER had good luck with ANY BBK part.
is it a known fact that the stock regulator is boost sensitive? can anybody verify this? if so i'll just throw my stock one back on.

what did your idle air fuel ratio read before you jacked the fuel pressure up? it is not uncommon to be in the 15-16:1 range at idle.

what was your air fuel ration at wot with stock fuel pressure?


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post #11 of 23 Old 02-07-2007, 10:03 AM
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First thing I would do is unplug the 02 sensors, reset the ecu and fire the car and see what afr it idles at. Remember you could always have more than one problem. When you force the car into open loop and it idles close to 14.7 you can eliminate the maf as a cause. If this corrects it and you then re install the 02's and the car starts adapting lean again your 02's are probably too far downstream and cold.

The fact that it runs 10.5 at W.O.T. also is from the 70psi fuel pressure. the stock ecu with a correctly calibrated maf will target around 12, unless you have a tune tell it otherwise.

I don't think the regulator is a problem because a 1to1 regulator has nothing to do with afr when the car isn't in boost. It would act just like a stock regulator. The purpose of a 1to1 regulator isn't to raise pressure for more fuel. it's because for every pound of boost you put in the intake you have lost a pound of fuel pressure. (think of it like back pressure) the only thing the 1to1 does is keep the pressure actually at 40psi (IN) the manifold.

Last edited by awdgsx; 02-07-2007 at 10:08 AM.
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post #12 of 23 Old 02-07-2007, 04:33 PM Thread Starter
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fuel pressure issue

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If you back off on the fp, does the car idle poorly? My car was reading about 12.5-13 at idle. They go somewhat lean NOT under load as the rpms go up. But as soon as you hit wot, you should be down around 12-11.
If I back off the fuel pressure the car will hardly idle when cold. Surges and dies frequently until it warms up.


Quote:
what did your idle air fuel ratio read before you jacked the fuel pressure up? it is not uncommon to be in the 15-16:1 range at idle.

what was your air fuel ration at wot with stock fuel pressure?
The AFR at idle was in the mid 20's @ 40psi fuel pressure (hence the idle problem). It was running around 14.1 in boost (didnt try this but about twice just to verify what I saw, I had previously popped a head gasket before getting the wideband and had no questions why after I saw what the afr was.)


Quote:
First thing I would do is unplug the 02 sensors, reset the ecu and fire the car and see what afr it idles at. Remember you could always have more than one problem. When you force the car into open loop and it idles close to 14.7 you can eliminate the maf as a cause. If this corrects it and you then re install the 02's and the car starts adapting lean again your 02's are probably too far downstream and cold.
I think you could be on to something here. The first time I had the car running with the turbo I had to unplug the O2s to even run the car, it would seemingly go extremely rich and hardly run with the O2s plugged in (I didnt have the wideband yet) I of course blew a headgasket pulled the motor out, installed new front, main seals, oil pan gasket, arp studs, and head gaskets and put it all back together. This time it runs with the O2s without any of the issues it had the first time dont know why? I'm not clear how forcing the car into open loop and it idling with a good afr will tell me that the meter is not the problem though? Are you saying leave the fuel pressure @ 70 and do this and since the computer shouldnt be reading the Maf if the afr stays the same that the meter is not the problem?

Thanks for your suggestions keep them coming and I will try the ones already listed and let you know if I figure anything out. The track opens here Feb. 17th and I would love to have this figured out by then.
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post #13 of 23 Old 02-07-2007, 05:37 PM
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no, put the FP to stock and unplug the 02's. This will force the computer make fuel calculations directly from the maf and not use any adaptive correction from the 02's. This is what I think might be happening... the 02's are incorrectly leaning the car by say 20%, 17to1ish, the 02's can only move the fuel about 25% so they are almost leaning it as far as it will go, so when you raise the FP to 70 the 02's cannot move it anymore and the extra fuel brings the car to about 15to 1 the only problem is when the car goes W.O.T. when the car normally would hit 12.8 ish afr it will now hit low 10's. because of the extra FP.

How most people get around the 12.8 target afr in the ecu is to use correct 02's and fuel trim to their advantage.
Everything correct you put on a maf and pull the car, it runs 12.8 afr so you raise the FP untill it is running about 11.7, now you would think it would idle too rich too but if it's right the 02's will do their job and bring idle afr back to 14.7.
Does this all make sense?

btw. don't forget to unplug the battery for the non 02 sensor tests, if you don't the -20% fuel trims will still be there.
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post #14 of 23 Old 02-07-2007, 05:42 PM
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Also, you can use a chip to change the target AFR from 12.8 to 11.5. This is the Best way to do it. Just remember no chip tune will fix a broken part.
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post #15 of 23 Old 02-07-2007, 06:36 PM Thread Starter
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Ok I went out and tried a few things.
I tried reclocking the meter and it had no effect.
I tried unplugging the O2 sensors, @70psi before I read your reply, and had no effect that I could tell.
I tried unplugging the MAF and the car idled rich, in the mid 12's.
I plugged the maf back up and brought the fuel pressure back down to about 50 psi, the car was idling all over the place it would try to hold 14-15 afr then would jump to 17-18 and bounce back and forth. I took it out and made a pull like this and the afr didnt get below 14.1 in boost. Brought it home and put the fuel pressure back up to 70 and made another pull and its holding about 11:1 in boost? This is a b&g kit with the o2 sensors in the downpipe maybe a little over a foot downstream of the o2s I would think that they are seing enough heat, and they are both new. I need to try the O2 test that you described but im through with it for tonight. I'll try to do it tommorow or Fri. night, its hard to find motivation when nothing seems to work
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post #16 of 23 Old 02-07-2007, 06:39 PM
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yes, I think it might be beer 30 for you sir ....
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post #17 of 23 Old 02-07-2007, 06:50 PM Thread Starter
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I wish! Got to go get some lab results the 15th of this month, been having some liver issues, cant get my body tuned and running right either
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post #18 of 23 Old 02-07-2007, 06:57 PM
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I wish you the best of luck getting them both running right.
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post #19 of 23 Old 02-07-2007, 07:03 PM Thread Starter
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thanks. I'll get it just have to keep picking at it. I'm trying to resist the urge to just take it to the local dyno shop and tell them to call me when its fixed and tuned
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post #20 of 23 Old 02-08-2007, 07:27 AM
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if you don't have a serious leak somewhere in your system i would guess miscal'd maf.

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post #21 of 23 Old 02-20-2007, 10:14 PM Thread Starter
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Ok I want to update everyone, maybe this will help someone searching in the future.

I thought I had touched literally everything on this car by now but there was one thing I had never removed from the car: The computer! Pulled it out this weekend and to my amazement there was a superchips chip on it! Pulled the chip, dropped the fuel pressure and the afrs looked much better. Installed the tweecer added my tune and the car is so much more pleasant to drive now I think my first try at the tune is even pretty close

Assuming most of the aftermarket "canned" chips just bump the timing and fuel, I cant believe I didnt hurt the car on nitrous as much advance as I was running at the distributor.

Moral of the story: Check to make sure your car is not chipped if you have weird tuning issues, you never now what the previous owners have done.
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post #22 of 23 Old 02-20-2007, 10:49 PM
 
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Ok I want to update everyone, maybe this will help someone searching in the future.

I thought I had touched literally everything on this car by now but there was one thing I had never removed from the car: The computer! Pulled it out this weekend and to my amazement there was a superchips chip on it! Pulled the chip, dropped the fuel pressure and the afrs looked much better. Installed the tweecer added my tune and the car is so much more pleasant to drive now I think my first try at the tune is even pretty close

Assuming most of the aftermarket "canned" chips just bump the timing and fuel, I cant believe I didnt hurt the car on nitrous as much advance as I was running at the distributor.

Moral of the story: Check to make sure your car is not chipped if you have weird tuning issues, you never now what the previous owners have done.
Werd......Glad to hear that you got it figured out.....You had me worried a bit cause I have a B&G kit going on my H/C/I 347......
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post #23 of 23 Old 02-20-2007, 11:05 PM Thread Starter
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b&g

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Werd......Glad to hear that you got it figured out.....You had me worried a bit cause I have a B&G kit going on my H/C/I 347......
The only complaints I really have about the b&g kit is that I had to cut a little more from the airbox hole than I would have liked to, and the down pipe is an mf'er to get in an out.

Overall the kit is very nice quality and fit wise and I wouldn't hesitate to recommend it to anyone.

If I was you I would be more worried about the your block if its stock
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