[Megahurtz]

Originally Posted by Joshinator99

What are you commanding…?

2300 psi

The leading edge table might need to be adjusted hmmmm

[SOCAL.M6.ZLE]

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

My only 2 cent contribution to your project would be to make sure you replace the TTY supercharger bolts. Be sure to post some photos and results when finished!

[Joshinator99]

Originally Posted by Megahurtz

2300 psi

The leading edge table might need to be adjusted hmmmm

Yeah there’s an adjustment for the cam lobe difference and I think that’s it IIRC.

[Megahurtz]

Originally Posted by Joshinator99

Yeah there’s an adjustment for the cam lobe difference and I think that’s it IIRC.

I'm still on the stock Cam so I wouldn't need to change the angle axis. My thought is to increase the values in the 4000-7000 range so that it knows its flowing more fuel. I'm going to test it out today and see what happens. I checked some logs with the stock LT4 fuel system and there area couple of instances where fuel spikes just a little bit on shift when the injectors shut for a moment. I'm starting to think this may just be fuel pulse feedback in the rails from the injectors shutting and it isn't avoidable. The only place that makes sense to solve it is to adjust the leading edge table and see if it recognizes it should bleed off more pressure when the injectors close. It's so brief that it doesn't happen every time even with the LPE big bore and the XDI 30's. Either that or the scanner does catch it in the log. I've set the refresh rate to the fastest possible to make sure.

[KingLT1]

I see the same thing on another manual car with the same fuel system. Doesn't appear to be an issue. I don't think it will pop the relief valve under those conditions.

[Megahurtz]

Originally Posted by KingLT1

I see the same thing on another manual car with the same fuel system. Doesn't appear to be an issue. I don't think it will pop the relief valve under those conditions.

Just came here to say I saw no change to the pressure spike on shift with making adjustments to the leading edge table. Going to put it back to stock.

[KingLT1]

Originally Posted by Megahurtz

Just came here to say I saw no change with making adjustments to the leading edge table. Going to put it back to stock.

I have run the leading-edge table set to stock LT4 values and LT1 values. I believe I get a smidge better high side output using the LT1 tables with the LPE pump. I am able to run 2500psi rail instead of 2175psi and the high side will hold pressure which nets lower pulsewidths. Maybe you can try it and confirm?

[Megahurtz]

Originally Posted by KingLT1

I have run the leading-edge table set to stock LT4 values and LT1 values. I believe I get a smidge better high side output using the LT1 tables with the LPE pump. I am able to run 2500psi rail instead of 2175psi and the high side will hold pressure which nets lower pulsewidths. Maybe you can try it and confirm?

You know what, I didn't say anything about this before as I thought maybe it was just in my head. But I can confirm that changing the leading edge values above 4000 rpm indeed allowed the high side to hold a higher commanded pressure. I'm not using the LT1 axis or values. I made my own table for the LT4 and I am having good results. I discovered this when I put the table back to stock and lost a little bit of pressure in the higher rpms

PM me if you want more details.

[ZL1...SON]

Originally Posted by MartinLe

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.

I know this is an older thread, but wanting to bring this back up as I am currently getting my car dialed in after the addition of the Jokerz race port, XDI +30s and LPE BB HPFP. I ran into the rail getting drained and injector PWs going through the roof as described in this thread. I am currently doing a lot of research on this and working with my tuner to see where we can safely get the ethanol content up to. I brought up the possibility for dropping the rail pressure down from 2,900, as discussed in this thread.

Soooo... megahertz, I would definitely be interested in more conversation on this topic and anything that you and KingLT1 have learned since the last conversations here.

Another question I have is about the Scaler Offset, and Gain for these pumps. I have read where in the past these needed to be changed to 12.5 and 8.75... but is that still accurate for the pumps today? What happens if those don't get changed? Mine have not been changed and other than running out of fuel at 60% E, the car has run great after the parts were added and tuned on 93.

[KingLT1]

I don't think there is much you can do to get more fuel headroom out of that setup. Being that it will handle E60 tells me things have to be optimized pretty well.

The only reason you should drop rail pressure is if the HPFP will not hold commanded pressure. Then you lower it until it stabilizes, but that will cause IPW to increase. So you need to have enough IPW headroom in order to do that. For example, if your IPW is already at 5.8ms, then there is no room to lower rail pressure. If they are around 5.2-5.3ms but rail is dropping, then you would lower rail to keep that stable and IPW should still have some room to inject fuel on time.

That being said imo the LPE doesn't like 2900psi, it seems to work best no higher than 2500psi. That is where I normally run them with +30 XDI injectors. That doesn't mean it won't run 2900psi, it just tends to drop off a cliff fast when you close on its limits commanding that high of pressure.

Hoping to see if the new Katech Goliath pump is an improvement over the LPE. Because if it is happy @ 3200psi, then there should be some gains to be had as that will lower IPW and allow these bigger injectors to go further.

[Megahurtz]

Originally Posted by ZL1...SON

I know this is an older thread, but wanting to bring this back up as I am currently getting my car dialed in after the addition of the Jokerz race port, XDI +30s and LPE BB HPFP. I ran into the rail getting drained and injector PWs going through the roof as described in this thread. I am currently doing a lot of research on this and working with my tuner to see where we can safely get the ethanol content up to. I brought up the possibility for dropping the rail pressure down from 2,900, as discussed in this thread.

Soooo... megahertz, I would definitely be interested in more conversation on this topic and anything that you and KingLT1 have learned since the last conversations here.

Another question I have is about the Scaler Offset, and Gain for these pumps. I have read where in the past these needed to be changed to 12.5 and 8.75... but is that still accurate for the pumps today? What happens if those don't get changed? Mine have not been changed and other than running out of fuel at 60% E, the car has run great after the parts were added and tuned on 93.

100% agree with King

E60 in the summer and E50 in the winter is going to be about the max that setup can handle. If you're hitting this then you're already getting the maximum out of the pump.

Adding on to what King already said, the LPE with the stock cam fuel lobe will drop off real hard when it reaches the max. You can push it to 2900 on the stock cam on lower Ethanol blends or with less airflow mods, but it isn't very stable. I actually set mine up to hit 2700 PSI on the hit and then taper off to 2500 or so by redline. On E60 the pulse width in the summer was 5.5ms at redline. I tried stretching it to E70 and letting the injectors spray up to 6.2 by redline but the car didn't go any faster. You really are just trying to spray the most amount of fuel you can fit in the injection window.

As for the scaler offset, leave it to whatever your OEM value was. It doesn't do anything that I could tell.

[ZL1...SON]

Thanks for the input, guys. I realize that getting to E50 or E60 is already getting most of the benefits of running Ethanol. My goal of getting to the highest E content was more out of laziness and the desire to not need to mix. Oh well.