[Megahurtz]

I'm swapping the stock LT4 HPFP out for an LPE big bore v2 and XDI 30% injectors. I'll be on the stock cam for now.

Is there anything I need to be aware of when swapping out? From my understanding since I'm keeping the stock cam, there is no need for a lash cap and its a simple remove and replace the pump.

Do I need to measure preload and shim accordingly or would matching the stock LT4 pump shims be ok?

Looking for info from those who have done this swap.

Thanks

[JSH]

Originally Posted by Megahurtz

I'm swapping the stock LT4 HPFP out for an LPE big bore v2 and XDI 30% injectors. I'll be on the stock cam for now.

Is there anything I need to be aware of when swapping out? From my understanding since I'm keeping the stock cam, there is no need for a lash cap and its a simple remove and replace the pump.

Do I need to measure preload and shim accordingly or would matching the stock LT4 pump shims be ok?

Looking for info from those who have done this swap.

Thanks

What are your mods?

[KingLT1]

You should be fine to install as is...I would also replace the high-pressure fuel lines.

[Megahurtz]

Originally Posted by JSH

What are your mods?

Originally Posted by KingLT1

You should be fine to install as is...I would also replace the high-pressure fuel lines.

Mods are 2.31 upper which I will likely be swapping out for a 2.45 upper with the ported blower that's on the way, ARH LT's, Intake, TB, JMS BAP and Flex Fuel.

I'll be installing XDI 30% injectors with the Big Bore. I do have all of the replacement high pressure fuel lines.

Right now I can run E55 in the summer and E45 in the winter. But I want to be able to run E60+ year round and I don't want to go with Meth.


Thanks guys

[KingLT1]

Originally Posted by Megahurtz

Mods are 2.31 upper which I will likely be swapping out for a 2.45 upper with the ported blower that's on the way, ARH LT's, Intake, TB, JMS BAP and Flex Fuel.

I'll be installing XDI 30% injectors with the Big Bore. I do have all of the replacement high pressure fuel lines.

Right now I can run E55 in the summer and E45 in the winter. But I want to be able to run E60+ year round and I don't want to go with Meth.


Thanks guys

I have tuned 4 cars with that fuel system. Helped with install on 3 of them. E60 shouldn't be a problem.

My brother is running E60 @ .84 lambda in his ZL1.

Mods: Ported blower, 2.17 pulley, headers, CAI, 103tb, same fuel system.

It made 660whp SAE 6th gear on a Mustang dyno which reads 6% low vs a Dynojet. Not to mention that was also with Toyo R888 tires.

[Megahurtz]

Originally Posted by KingLT1

I have tuned 4 cars with that fuel system. Helped with install on 3 of them. E60 shouldn't be a problem.

My brother is running E60 @ .84 lambda in his ZL1 and he has Ported blower, 2.17 pulley, headers, CAI, same fuel system.

Awesome, Maybe I'll stick with the 2.31 or swap to my 2.38 pulley. Traction will be an issue if I go too far.

I usually tune cammed cars with the stock LT4 hpfp and fuel lobe for more fuel. This isn't the normal setup I tune for but this is my daily and I want to keep it driving like stock, no meth, no sloppy feeling big tires in the back.

[CW3SF]

I’m running that same set up.

https://www.camaro6.com/forums/showthread.php?t=604568

The HPFP is a straight swap. I didn’t have to shim anything. Just make sure the lobe under the pump is down (by rotating the engine) before you bolt down the new pump. Lots of instruction videos online. As mentioned, change out the HP fuel lines. Injectors were also an easy straight swap. I made 714whp SAE on e84 in Denver on stock pulleys.

[KingLT1]

Originally Posted by Megahurtz

Awesome, Maybe I'll stick with the 2.31 or swap to my 2.38 pulley. Traction will be an issue if I go too far.

I usually tune cammed cars with the stock LT4 hpfp and fuel lobe for more fuel. This isn't the normal setup I tune for but this is my daily and I want to keep it driving like stock, no meth, no sloppy feeling big tires in the back.

2.38 should be fine. Far as tuning, You will likely need to drop the rail pressure down from 2900 psi down in the 2200-2500 range.

[Megahurtz]

Originally Posted by CW3SF

I’m running that same set up.

https://www.camaro6.com/forums/showthread.php?t=604568

The HPFP is a straight swap. I didn’t have to shim anything. Just make sure the lobe under the pump is down (by rotating the engine) before you bolt down the new pump. Lots of instruction videos online. As mentioned, change out the HP fuel lines. Injectors were also an easy straight swap. I made 714whp SAE on e84 in Denver on stock pulleys.

Yup I have the tool in hand to make sure the lobe is down.

I'll be at sea level down here in FL so not sure I can handle E84. Pump E here is about E76-E80 depending on the station. It would be great to be able to not mix.

Thanks!

[CW3SF]

Originally Posted by Megahurtz

Yup I have the tool in hand to make sure the lobe is down.

I'll be at sea level down here in FL so not sure I can handle E84. Pump E here is about E76-E80 depending on the station. It would be great to be able to not mix.

Thanks!

Yeah I just brought my car to the east coast. Still moving now but soon I’ll have mine logged for new E content limits. The bonus for being at sea level is more boost though.

[Megahurtz]

Originally Posted by KingLT1

2.38 should be fine. Far as tuning, You will likely need to drop the rail pressure down from 2900 psi down in the 2200-2500 range.

Both LPE Big Bore v2 and the XDI 30% injectors claim they support 2900 PSI. I directly asked LPE this question and it was confirmed. I did not ask XDI, but the paperwork that arrived said 2900 PSI is guaranteed to be consistent and 3200 is supported for racing/WOT application. Essentially I interpreted that XDI was saying you can run a higher(3200) PSI but they don't recommend it for consistency on for a street car. I'm assuming due to stuttering perhaps. I know FIC has this issue above 2600psi.

Did your experience find something different?

[Joshinator99]

Originally Posted by Megahurtz

Both LPE Big Bore v2 and the XDI 30% injectors claim they support 2900 PSI. I directly asked LPE this question and it was confirmed. I did not ask XDI, but the paperwork that arrived said 2900 PSI is guaranteed to be consistent and 3200 is supported for racing/WOT application. Essentially I interpreted that XDI was saying you can run a higher(3200) PSI but they don't recommend it for consistency on for a street car. I'm assuming due to stuttering perhaps. I know FIC has this issue above 2600psi.

Did your experience find something different?

Higher pressure equals less flow through the HPFP (or any pump for that matter). So, it depends on your fueling needs. You’ll have to datalog and adjust as needed. If your IPW is getting much over 6.0ms, then try tweaking up the HPFP pressure but you’ll have to keep a close eye on it…when rail drops off it can be fast. LPE recommends 2175 because that is max flow, but you can run higher pressure if needed.

[KingLT1]

Originally Posted by Megahurtz

Both LPE Big Bore v2 and the XDI 30% injectors claim they support 2900 PSI. I directly asked LPE this question and it was confirmed. I did not ask XDI, but the paperwork that arrived said 2900 PSI is guaranteed to be consistent and 3200 is supported for racing/WOT application. Essentially I interpreted that XDI was saying you can run a higher(3200) PSI but they don't recommend it for consistency on for a street car. I'm assuming due to stuttering perhaps. I know FIC has this issue above 2600psi.

Did your experience find something different?

I have run them both at 2900psi, but it's right on the edge of misfire and a stock low side pump with JMS won't keep up. LPE has never said their pump will support 2900psi to me and I have spoken with a couple guys there (I live 30 minutes away). Perhaps they been reading these forums and have read my posts stating it will Lol. They told me it would pop the O ring but it never has. I have had FIC +30 hold 2900psi and some misfire. The XDI +30 will hold 2900 psi but the +65 are 2600 max.


On a SS LT1 P1x pushing 10 psi peak I found 2500 psi worked best and provided the most fuel headroom with this fuel system. It was stable to E70 @ .82 lambda. This setup hits much softer so it doesn't tax the system on the hit.

On a FBO ZL1 with Kong port and 2.17, I needed the high side set low as possible because it wants to bleed the rails on the hit. I actually have to start with a leaner AFR(.87) and blend down .84. It holds E62 fine @ 14psi.

On my SS LT1 Whipple 2.9 setup I started at 2900psi and the high or low side wouldn't keep up. Dropped to 2500 psi, low side was fine high side was still dropping some. Went down to 2175 and both hold steady on E60 @ 10 psi .82 lambda.

Injectors are in the 5.5-5.7ms range on all the above. Commanding more pressure attempts to lower Injector ms down to 5.0-5.2 but soon as the high side starts dropping, they open up to 5.8-5.9

So, it all comes down to finding what works best on a particular combo. A stronger low side would likely help hold higher pressure.

[MartinLe]

Originally Posted by Joshinator99

Higher pressure equals less flow through the HPFP (or any pump for that matter). So, it depends on your fueling needs. You’ll have to datalog and adjust as needed. If your IPW is getting much over 6.0ms, then try tweaking up the HPFP pressure but you’ll have to keep a close eye on it…when rail drops off it can be fast. LPE recommends 2175 because that is max flow, but you can run higher pressure if needed.

Originally Posted by KingLT1

I have run them both at 2900psi, but it's right on the edge of misfire and a stock low side pump with JMS won't keep up. LPE has never said their pump will support 2900psi to me and I have spoken with a couple guys there (I live 30 minutes away). Perhaps they been reading these forums and have read my posts stating it will Lol. They told me it would pop the O ring but it never has. I have had FIC +30 hold 2900psi and some misfire. The XDI +30 will hold 2900 psi but the +65 are 2600 max.


On a SS LT1 P1x pushing 10 psi peak I found 2500 psi worked best and provided the most fuel headroom with this fuel system. It was stable to E70 @ .82 lambda. This setup hits much softer so it doesn't tax the system on the hit.

On a FBO ZL1 with Kong port and 2.17, I needed the high side set low as possible because it wants to bleed the rails on the hit. I actually have to start with a leaner AFR(.87) and blend down .84. It holds E62 fine @ 14psi.

On my SS LT1 Whipple 2.9 setup I started at 2900psi and the high or low side wouldn't keep up. Dropped to 2500 psi, low side was fine high side was still dropping some. Went down to 2175 and both hold steady on E60 @ 10 psi .82 lambda.

Injectors are in the 5.5-5.7ms range on all the above. Commanding more pressure attempts to lower Injector ms down to 5.0-5.2 but soon as the high side starts dropping, they open up to 5.8-5.9

So, it all comes down to finding what works best on a particular combo. A stronger low side would likely help hold higher pressure.

OK, in a perfect world, we have 75# low side and 2900# at the rail and IPW's in the mid 5's. Of the three numbers, the IPW's are the most important in keeping the motor in one piece. Now we have some fluctuation in the fuel pressure, but the IPW's stay in the happy zone. During a run, the low side hangs in there at 70#+ and IPW's are in the low 5's. At the shift into second at 7K, in that little window of rpm drop at the disengagement of the clutch, the rail pressure drops to 2000# (low side 70#) and the IPW's raise to 5.8 - 5.9 for a split second, and then rail goes up to 2800# and IPW's back to mid 5's. The motor is happy. This is my understanding.

When I installed the blower/cam package, I was discouraged from the LPE BB pump because it ran at 2175#. "We want to have the 2900# at the rail at all times." You are running a steady 2175# at the rail and the IPW's are in the 5's. How can that be argued as anything less than safe and acceptable? Some tuners will argue the 2175#. But the IPW's are in the happy zone.

As Josh stated, the higher the pressure the lower the volume. The LPE pump will run under some conditions at 2900#, but it is designed for 2175#. Why wouldn't the OEM pump push more fuel at a lower PSI?

I apologize if this is a little derail of the OP's intent, but it is about pressures.