03 Cobra Pumps maxing out on my 2v GT -any ideas?

TonyG · Mar 28, 2007

I have a vortech S-trim with a 3.00" pulley and front mount intercooler. Fuel-wise, I have 42 lb injectors and an 03 Cobra dual pump. I'm making ~440 rwhp. I was making ~10-12 psi before, but now (after longtubes), boost is down to ~9 psi.

Anyway, we got the car on the dyno and the A/F appears to be leaning out above 5000 rpms. The fuel pump is at 100% duty cycle.

Is this possible with the 03 Cobra pumps? The tank was dropped and everything appears to be OK. Also, I'm not sure if it matters, but some girl did smack me in the rear a couple years ago. At the time, it appeared to be only cosmetic damage, but she did hit hard enough to trip the fuel switch.

Any ideas of what to check?

DBMSTNG · Mar 28, 2007

how lean is it getting? if you are hitting 100% duty cycle at 440rwhp, there's a restriction somewhere. replace the fuel filter and make sure all the fuel lines and injectors are clean and working properly.

TonyG · Mar 28, 2007

100% duty cycle, and the A/F climbs to 12.8:1. Fuel filter is a good idea -that'll be the next thing I'll check.

Matt's 03 GT · Mar 28, 2007

TonyG said:
I'm not sure if it matters, but some girl did smack me in the rear a couple years ago.

I'm sorry but that struck me as very funny!

White Stang · Mar 28, 2007

Don't think it is your pumps. I am suppling enough fuel for 550 hp with just the cobra pumps. I noticed you are using 42 pound injectors where I am using 60 pound injectors and aeromotive fuel rail system. Your engine is probally starving at the injectors. Also get a Maf.i.a to make sure your maf isn't pegging to allow you the best tune.

TonyG · Mar 28, 2007

Regarding the MAF sensor, I have a Pro-M univer, in a blow-thru set-up.

Rickey_Bobby · Mar 28, 2007

I think your problem is with your MAF, even the 90mm maf will peg around 450rwhp... MAFia will help you out a lot.
Fuel filter is a no brainer...
also look into a Kenne Bell Boost-a-Pump for added peace of mind.

as for the injectors, I have run the 42's up to 600rwhp with no issues, but it's your call.

Start with the MAF, its most likely the cause... and cheapest to fix.

the98stang · Mar 28, 2007

I'm thinking you should upgrade the injectors and MAF. The cobra pumps should easily support 500WHP. The fuel filter might be clogged too.

01Steeda · Mar 29, 2007

9 psi doesnt sound right on a 3.0 pulley either. with ported heads cams and headers I was seeing over 11psi on my old 2v.

Am I just off base?

TonyG · Mar 29, 2007

Steeda. I dunno, maybe my gauge is off.

Anyway, this morning, the fuel filter was changed, and the cobra pump is still maxing out. So we've decided to do a wire mod (thicker gauge wire) to the fuel pump, and switch to dual Focus pumps. I'll keep you posted.

lvmustanggt · Mar 29, 2007

White Stang said:
Don't think it is your pumps. I am suppling enough fuel for 550 hp with just the cobra pumps. I noticed you are using 42 pound injectors where I am using 60 pound injectors and aeromotive fuel rail system. Your engine is probally starving at the injectors. Also get a Maf.i.a to make sure your maf isn't pegging to allow you the best tune.

Damn brother you got a killer looking stang. I am loving the way your car looks, feels like humping your car

spederman · Mar 29, 2007

Do you have the cobra pumps in a cobra tank or the GT tank? If its in a GT tank, maybe your sucking the bucket dry too quickly with dual cobra pumps and going lean because of that. Maybe try a baffled cobra tank if you dont have one already.

Dusstbuster · Mar 29, 2007

Couldn't he just drill some more holes in the GT bucket?

GToddyT5 · Mar 29, 2007

How do you peg a 90 mm MAF at only 450 RWHP? I would think his injectors and MAF are sufficient for now. He's not making an insane level of power.

TonyG · Mar 29, 2007

spederman said:
Do you have the cobra pumps in a cobra tank or the GT tank? If its in a GT tank, maybe your sucking the bucket dry too quickly with dual cobra pumps and going lean because of that. Maybe try a baffled cobra tank if you dont have one already.

I have the Cobra Pumps in the GT tank. We already thought about that, so we tried filling up the tank...it didn't help.

spederman · Mar 29, 2007

TonyG said:
I have the Cobra Pumps in the GT tank. We already thought about that, so we tried filling up the tank...it didn't help.

Filling the tank helps, but did you drill any holes in the stock basket? Even though your tank is full, having two pumps is going to suck that basket dry faster than gravity can keep it full of gas.

Don 95Vert · Mar 29, 2007

Bingo! That's your problem - you also need the '03 Cobra tank. Seen it happen to GTs numerous times on the dyno. Tuned many a '03 Cobras at >600 RWHP with stock tank/pumps with a BAP, so after you get the tank, your problems should go away.

The 90mm LMAF MAY be near it's limit, but I've seen some go to close to 480 or so before pegging - but the datalog gives the answer plain and simple, the fuel pump is maxxing out - and it's because it's sucking the fuel can dry - or low. The log would also tell you if the MAF is pegging - and apparently it does not - and the A/F goes so lean so fast when a MAF pegs, you almost cannot get out of it fast enough.

Don

TonyG · Mar 29, 2007

Cobra tanks are expensive ($550), will spederman's idea work?

Any drawbacks to drilling out the fuel cannister? What about turning it to swiss cheese to ensure it gets enough fuel?

White Stang · Mar 29, 2007

Dusstbuster said:
Couldn't he just drill some more holes in the GT bucket?

Just break the GT bucket out. I run it like that no issues. I have run it pretty low but I fill it up at a quarter tank by habit. BTW I would do this regardless of what tank I am using.

White Stang · Mar 29, 2007

lvmustanggt said:
Damn brother you got a killer looking stang. I am loving the way your car looks, feels like humping your car

thanks

03 Cobra Pumps maxing out on my 2v GT -any ideas?

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