Is my trans done? (log included)

[TriPinTaZ]

You’re welcome! I had to learn most of this the hard way LOL!

So, to be clear, the *LPE HPFP* moves more volume at a lower pressure, BUT NOT the lines and injectors! Thats a big point so please don’t misunderstand me. Less pressure is less flow through the injectors, that’s why it’s important to have the right injectors. That’s why you need to balance the system out! In other words, if you run 2175 and the rail pressure is rock solid but your IPW is 7.0…not good as you know lol. So for that example, I’d try say 2400 PSI rail (LPE is fine there as well as all injectors) and see if that helps, but watch the rail! I tried going from 2175 to 2500 with my setup and it was a disaster, I’m lucky I didn’t smoke anything. The rail pressure will tank like a rock if you ask for too much. If the rail holds fine and your IPW improves, then good and try a little more if need be. Some of my buddies on Camaro6 have run 2900 psi on the LPE HPFP, but they were band aiding too small of an injector.

Oh, and all this assumes you have great low side pressure (I run 80 psi) and no tiny ass OEM check valve that comes in the LT1 hard line. And if you’re smarter than me, you run a +42 or +43 cam lobe (they exist) on the LPE pump, which you cannot run on the LT4 HPFP. That’s another 5% you gain over the LT4.

EDIT: pull up the pump flow chart on any fuel pump. The more pressure you ask for, the less volume it can move. So in that case, if everything else downstream is plenty big, you’ll move more flow through that particular pump at lower pressure. The big question is, is everything else big enough to operate in lower pressure.

Got it, that makes more sense! I am going with XDI 30% injectors with the car in question and it is an LT4 car. I'll start lower and work up to a higher pressure if needed.

[TriPinTaZ]

I made some fueling changes to commanded rail pressure and leaned it out a bit. I'm seeing mid-6ms injector times which I understand aren't great, but at least not way over the top. I have two logs. One where I did a short run with the converter locked (normal state) and one where I ran it unlocked.

What is very interesting is that you can actually see the shuddering in the RPM in the log when you set the scaling to zoom way in (green trace line on the bottom strip). The cyclical/sine wave look to the trans/TCC slip recorded also coincides with the cyclical/sine wave in the RPM. It's much more pronounced with the converter locked (normal state) both visually in the log and actual feel in the car.


Locked log:
Attachment 124391
Attachment 124392


Unlocked log:
Attachment 124394
Attachment 124393

The low side pressure is lower than the recommended PSI to support the LPE Big Bore. I bet if you get your low side to 70+ PSI you would have better results.

[kjlindgr]

I think my low side fuel pressure sensor is dying. It often flat lines at 57PSI, but you can see in the logs it will periodically spike or read something different. When it's reading, it's around 80PSI under load.

Does anyone happen to know what the part number for that sensor is?

[sevinn]

That log also looks like it started breaking up on the passenger side.

Also, manifold temp doesn't follow that sensor 3 IAT reading. It does in LSA,LS9 but for some reason it doesn't on the LT4's I've watched.

That also looks like it's making quite a lot of power.. and the converter is locked.. Have you considered not locking the converter at wide open?

It won't follow iat2, but will follow iatb1s3

[Joshinator99]

Got it, that makes more sense! I am going with XDI 30% injectors with the car in question and it is an LT4 car. I'll start lower and work up to a higher pressure if needed.

Since those injectors are smaller than what LPE uses, I’d probably start at 2400 PSI and see how it looks.

The low side pressure is lower than the recommended PSI to support the LPE Big Bore. I bet if you get your low side to 70+ PSI you would have better results.

This. So many people screw this up (as I did LOL). To get the most out of LPE BB HPFP:
1. Get rid of tiny check valve on inlet of HPFP
2. Best low side fuel pressure you can. I use 80 PSI but LPE told me I should consider 100 PSI as I approach the limits of their system.
3. Biggest cam lobe you can run. +42% (LPE cam) or +43% (now available with CamMotion).
4. Biggest injectors you can get. They designed around +52% but +65% is even better IMO.

Just my two cents on this issue.

[Ghostnotes]

Damn .......+65%

Shows how long I've been out of the loop. I'm still considering +35% injectors and a HPFP.....my lobe is only 10%.......I feel so inferior now.....

Any how just to ask, you are scaling your fuel flow axis to match the differences right???