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Fuel Pressure Falling On Boost..?


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  • Menace
  • Donating Members
  • Member For: 13y 7m 27d
  • Gender: Male
  • Location: Sydney

Hey guys,

I took my car in to get some ID1000's fitted and a retune. After fitting up the ID's we ran the car up on the dyno to find that the afrs were climbing rapidly when the car was coming onto boost and starting to make some descent power.

1st of all the 044 was replaced, ran it up again to find the same result, checked the walbro out which was fine.

Replaced the fuel filter then the fuel reg. and even the battery as my battery is abit shagged.. + just to rule out any BS.

Even checked the voltage on the fuel pump terminals thru the run which maintained over a steady 13V.

On the last run yesterday I bridged out the relay and pulled the fuse on the 044 for about 2min to ensure the surge tank was full again (like I said the feed to the surge tank is fine but I just wanted to rule it out anyway), ran it up straight away and was watching the fuel pres. gauge I T'd in between the 044 and the fuel rail only to find again the fuel pressure falling under full boost. It goes up to about 75psi then heads down to 50ish where we have to pull out.

The car is running e85 and making over 400rwkw with 17psi just under 4000rpm where the afrs were about to go to 13 and we had to pull out.

It has been pointing at not enough pump virtually from the start and am now in the process of fitting a 2nd 044 I've just been unsure of the whole thing given the cars I have seen getting around with a single 044, hence the swapping everything out part and troubleshooting yet finding the same result every time.

Has anyone had this problem whereas the 700hp pump isn't cutting the mustard near peak torque running on E85?

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  • Forged Member
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  • Member For: 17y 10m 11d
  • Gender: Male
  • Location: SW Sydney

The 700hp rating is more in line with a N/A motor on regular fuel, so it is possible that the pump isn't coping...

I'm sure someone else with more knowledge about fueling will come along

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  • Member
  • Member For: 19y 1m 26d
  • Gender: Male
  • Location: 2 Dunorlan Road Edwardstown S.A. 08 82999998

Hey guys,

I took my car in to get some ID1000's fitted and a retune. After fitting up the ID's we ran the car up on the dyno to find that the afrs were climbing rapidly when the car was coming onto boost and starting to make some descent power.

1st of all the 044 was replaced, ran it up again to find the same result, checked the walbro out which was fine.

Replaced the fuel filter then the fuel reg. and even the battery as my battery is abit shagged.. + just to rule out any BS.

Even checked the voltage on the fuel pump terminals thru the run which maintained over a steady 13V.

On the last run yesterday I bridged out the relay and pulled the fuse on the 044 for about 2min to ensure the surge tank was full again (like I said the feed to the surge tank is fine but I just wanted to rule it out anyway), ran it up straight away and was watching the fuel pres. gauge I T'd in between the 044 and the fuel rail only to find again the fuel pressure falling under full boost. It goes up to about 75psi then heads down to 50ish where we have to pull out.

The car is running e85 and making over 400rwkw with 17psi just under 4000rpm where the afrs were about to go to 13 and we had to pull out.

It has been pointing at not enough pump virtually from the start and am now in the process of fitting a 2nd 044 I've just been unsure of the whole thing given the cars I have seen getting around with a single 044, hence the swapping everything out part and troubleshooting yet finding the same result every time.

Has anyone had this problem whereas the 700hp pump isn't cutting the mustard near peak torque running on E85?

The 044 pump is rated at maximum of 420-450 fwkw @ 75psi on 98 octane at best. On E85 this converts to approx 360 fwkw @ 75psi.

On 400rwkw running E85 this equates to not having enough fuel flow when coming onto this power level. As soon as you see the presurre dropping it means that you have insufficant pump flow.

You will either need a second 044 or our new Streetfighter 1000hp twin intank fuel pump module.

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  • Menace
  • Donating Members
  • Member For: 13y 7m 27d
  • Gender: Male
  • Location: Sydney

PM sent.

I totally comprehend what you are saying I just don't get how some ppl can "stretch" them so to speak as the way I see it, it is a straight up "mechanical issue" that needs to be addressed with more pump.

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  • Member
  • Member For: 21y 8m 18d
  • Gender: Male

Why dont you run a voltage booster to the pump. I have done this on a couple of cars and it works great. Normal voltage at idle and 18V at boost via a relay. Just to see you could rig it up very easy. The B&M one has a boost port so voltage rises according to boost and you can adjust the gain. I notice a few high end workshops in the US are doing it this way now.

Running a second pump is just a pain in the backside.

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