[G2K]

Would love some input from you guys. So here's the current situation that I'm trying to wrap my head around... With my LT4 swapped blower/fuel on my 1LE the logs show I decrease of Low side from 70 all the way to low 50's even high 40's by redline. However, my Inj MS is still at around 4.8-4.9 and mi rail press never drops under 2800psi... This is with E65%!! by the way... everything looks like we can maybe reach E70.... but never seen that before on any stock LT4 fuel system...

1) explanation of such a low low fuel pump psi but still being able to have the high side more than sufficient.
My common sense says less low side = less high side. But maybe I'm seeing it wrong.
2) Would a BAP put the low side up there in the 70psi and keep it there or Is this an "about to go bad" pump? Keep In mind I have a 1LE which comes with the LT4 intank and I have about 40K miles running full E85 from my N/A Days
The majority of ZL1 intank pump cars that I've seen keep there pressure in the high 60s and 70s no matter what rpm they are at...

Thoughts?

MODS:
Ported TB/Intake/Headers/Exhaust & the LT4 Blower/fueling @ 8PSI

[TJay74]

After working with Ted @ Jannetty Racing on my Procharged D1SC SS 1LE I can tell you this, dont let the fuel in the tank get below a half of a tank.

I went to the strip last week, one of the runs I noticed the car falling on its face on the big end. Logs showed the low side dipped to 25psi and the high side to 880psi. Messaged Ted and he asked about the fuel in the tank. Filled up and tested again and everything went back to normal.

Depending on how hard the acceleration is and how much gas is in the tank you can uncover the low side and the pressure will dip off on you.

I have the JMS box on mine, so the low side stays in the 60-70 psi range. I am running E40, so mine doesnt really dip off unless I push it to 6500-6750 rpm, then it starts to dip off some.

[G2K]

Originally Posted by TJay74

After working with Ted @ Jannetty Racing on my Procharged D1SC SS 1LE I can tell you this, dont let the fuel in the tank get below a half of a tank.

I went to the strip last week, one of the runs I noticed the car falling on its face on the big end. Logs showed the low side dipped to 25psi and the high side to 880psi. Messaged Ted and he asked about the fuel in the tank. Filled up and tested again and everything went back to normal.

Depending on how hard the acceleration is and how much gas is in the tank you can uncover the low side and the pressure will dip off on you.

I have the JMS box on mine, so the low side stays in the 60-70 psi range. I am running E40, so mine doesn't really dip off unless I push it to 6500-6750 rpm, then it starts to dip off some.

Ahh good to know, I was actually under 1/4 since im playing with E%'s... in my case my rails never drop, just my low side.

I filled up today and will do some pulls later on and see if that was the case.

[KingLT1]

You want the JMS BAP, it will keep pressure on the low side 60-70psi.

I am surprised your fueling is that good. Your injector MS is in the range that most NA cars on E85 see. My injectors go above 6 once I get above E75 and I have a LPE DI pump. By E80 they are pushing 6.4. Never heard of anybody with a LT4 system being able to run more then E60 with a stock fuel lobe and no meth.

I also have not had a issue with fuel pressure drop running less then a half tank. Matter of fact I seldom run more then a half tank and I log all the time. I have several logs that were with a 1/4 tank no issues, low side 68-72psi.

[G2K]

Originally Posted by KingLT1

You want the JMS BAP, it will keep pressure on the low side 60-70psi.

I am surprised your fueling is that good. Your injector MS is in the range that most NA cars on E85 see. My injectors go above 6 once I get above E75 and I have a LPE DI pump. By E80 they are pushing 6.4. Never heard of anybody with a LT4 system being able to run more then E60 with a stock fuel lobe and no meth.

I also have not had a issue with fuel pressure drop running less then a half tank. Matter of fact I seldom run more then a half tank and I log all the time.

I have your exact same thoughts and thats why I posted this. Never seen this situation AND while having the lower side show so low. My buddy without the BAP never dropped under 60psi thats why im thinking scared my low side might be bad instead of actually just needing a BAP... dont want to spend $500 on a BAP and then turns out I have a "tired" pump.

[oldman]

I ended up going with both a ZL1 pump in-tank and a DSX second fuel pump. I don't like to see the low go below 65 (as I've been told). Turns out and it seems to be true some original SS had really weak pumps and even with the DSX pump working I would see say 55 PSI on the low side with factory SS pump. I also noted that on a 3/4 or more tank PSI does stay at 70 PSI. That said since I want to run E85 (all above is on gas. Long story short Zl1 in tank and DSX second pump is what I ended up with.

[G2K]

So today I did some more logs.... this time with the tank basically full and still saw the low side drop to high 40s, low 50s... Inj MS highest point was 5.2 and rails were still in the 2800.. while the low side being at what I just stated. This is on E66.7%

[oldman]

My injector window is small and my rail pressure is good, that said, with a low low side, I was worried and wend to a ZL1 pump intake.

Once the HP fuel pump cavitates, rail pressure goes to ZERO like a rock.

[JANNETTYRACING]

Originally Posted by G2K

Would love some input from you guys. So here's the current situation that I'm trying to wrap my head around... With my LT4 swapped blower/fuel on my 1LE the logs show I decrease of Low side from 70 all the way to low 50's even high 40's by redline. However, my Inj MS is still at around 4.8-4.9 and mi rail press never drops under 2800psi... This is with E65%!! by the way... everything looks like we can maybe reach E70.... but never seen that before on any stock LT4 fuel system...

1) explanation of such a low low fuel pump psi but still being able to have the high side more than sufficient.
My common sense says less low side = less high side. But maybe I'm seeing it wrong.
2) Would a BAP put the low side up there in the 70psi and keep it there or Is this an "about to go bad" pump? Keep In mind I have a 1LE which comes with the LT4 intank and I have about 40K miles running full E85 from my N/A Days
The majority of ZL1 intank pump cars that I've seen keep there pressure in the high 60s and 70s no matter what rpm they are at...

Thoughts?

MODS:
Ported TB/Intake/Headers/Exhaust & the LT4 Blower/fueling @ 8PSI

Adam sent me a log from your car asking about this, you need a new tune your car is super lean and in danger of engine failure namely ring lands.

Ted.

[Umbriel]

Originally Posted by oldman

I ended up going with both a ZL1 pump in-tank and a DSX second fuel pump. I don't like to see the low go below 65 (as I've been told). Turns out and it seems to be true some original SS had really weak pumps and even with the DSX pump working I would see say 55 PSI on the low side with factory SS pump. I also noted that on a 3/4 or more tank PSI does stay at 70 PSI. That said since I want to run E85 (all above is on gas. Long story short Zl1 in tank and DSX second pump is what I ended up with.

I was under the impression that once you go to the DSX auxiliary pump it bypassed the stock pump but I guess that is wrong and both are still used? I am about to buy the DSX auxiliary, LT4 HPFP and injectors and DSX said that would get me to around 750ish on E85 but I could benefit even more by doing the intank pump as well?

[KingLT1]

Originally Posted by Umbriel

I was under the impression that once you go to the DSX auxiliary pump it bypassed the stock pump but I guess that is wrong and both are still used? I am about to buy the DSX auxiliary, LT4 HPFP and injectors and DSX said that would get me to around 750ish on E85 but I could benefit even more by doing the intank pump as well?

The in-tank is always active, the aux pump kicks on as a assist pump.

[KingLT1]

Originally Posted by JANNETTYRACING

Adam sent me a log from your car asking about this, you need a new tune your car is super lean and in danger of engine failure namely ring lands.

Ted.

I figured that was the case. No way his fuel system is holding e65 like that and maintaining .82 lambda.

[Umbriel]

Originally Posted by KingLT1

The in-tank is always active, the aux pump kicks on as a assist pump.

Ok makes sense, I guess I would benefit from the LT4 low side pump then. Trying to get to 700-750 with the LT4 injectors and HPFP with the DSX auxiliary pump on E85. DSX said it was doable with the 32% cam lobe.

[JANNETTYRACING]

Originally Posted by KingLT1

I figured that was the case. No way his fuel system is holding e65 like that and maintaining .82 lambda.

commanding .79 getting .89