[Tim M]

Greetings!

I've got a 2018 SS 1LE with LT4 blower/416/cam that makes 740 CHP. I don't plan to go any further.

Most recent dyno log shows the low side fuel pressure below the requested - 76 psi requested and ~60 actual. Looking at the AFR, .825 requested with the result of .84 actual.

This is at 6600+ RPM...an area that I do use.

How critical is this? Will I gain sufficient pressure if I install a 2019+ LT4 lowside pump - according to forums, appears 2019's and up have a better low side pump compared to my year. I'd much prefer an OEM solution vice an add on boost a pump (my wiring skills are poor at best).

Appears this is OEM part number: 85170844 (~$140).

I suppose it is worth a shot (possible the original pump has lost some capacity?...)

Welcome comments.*Thanks.

[Joshinator99]

Originally Posted by Tim M

Greetings!

I've got a 2018 SS 1LE with LT4 blower/416/cam that makes 740 CHP. I don't plan to go any further.

Most recent dyno log shows the low side fuel pressure below the requested - 76 psi requested and ~60 actual. Looking at the AFR, .825 requested with the result of .84 actual.

This is at 6600+ RPM...an area that I do use.

How critical is this? Will I gain sufficient pressure if I install a 2019+ LT4 lowside pump - according to forums, appears 2019's and up have a better low side pump compared to my year. I'd much prefer an OEM solution vice an add on boost a pump (my wiring skills are poor at best).

Appears this is OEM part number: 85170844 (~$140).

I suppose it is worth a shot (possible the original pump has lost some capacity?...)

Welcome comments.*Thanks.

If you have a 1LE you already have an upgraded low side pump. The boost a pump would be the next logical step normally. I suppose the pump you have could be on the way out.

FWIW you’re not going to damage a forged engine on .84 lambda. That’s typically what I target under power enrichment anyway.

[KingLT1]

Target lambda is based on compression. If you are stock LT1 compression then .84 is a little lean. If you are lowered then it's fine. You can put a JMS on it or lower commanded to 60psi and see if it maintains commanded. With your setup there isn't going to be a big difference between 10psi on the low side. Requesting more low side psi normally can squeak more headroom out of the high side but if your high side has room then you can lower the low side psi so it's not struggling to keep up.

[ZL14ever]

Keep in mind that you'll again an additional 1-2 psi during winter, and that could drop low side well into the 50s if the ECM started adding more fuel

Do a JMS like King said and be done with it

[Saberscar223]

Is this on Pump Gas or Ethanol?

[RobZL1]

Tim, if you do decide to go with a JMS, I'll be pulling mine off my car in the next several weeks when I install my DSX in-tank pumps (in the event you are looking for a used one). It's got all the wires extended already, interior wiring covered in tessa tape, exterior in a loom, etc.

[Tim M]

Folks - many thanks for the responses.

"FWIW you’re not going to damage a forged engine on .84 lambda. That’s typically what I target under power enrichment anyway."

This is very helpful and provides reassurance!

"If you are stock LT1 compression then .84 is a little lean."

I'm close to 10.5 on this Texas Speed kit with a thinner cometic gasket so a good bit far from LT1 CR (11.5).

I will try a new low side pump just because. I'd really prefer not to add an electrical mod to the car (despise wiring!), but Rob, you may get an IM from me...

This pressure issue is one reason I've not run it on the autobahn...it sure pulls getting to 150!