Is my trans done? (log included)

[kjlindgr]

Hey guys,

I have a heavily modified C7Z with A8 trans. Trans and converter are completely stock. I have a log attached with TCC and trans slip logged. The car physically feels like it's shuddering once the power ramps in around 4000RPM. I suspect it's trans slip, but want confirmation from the experts here before I throw parts at it. I'm not sure what the limits are of the stock trans and converter, but I can only suspect I would be getting close to the limits. Car previously made about 800rwhp and has more boost now.

Thanks everyone

run5-5thgear.hpl

[TriPinTaZ]

I would suspect the IAT timing advance could be causing what you're experiencing. It has the timing jumping up and down abnormally. Additionally, you're out of fuel. Also it looks like you have 76% ethanol in the car. The timing you are running is WAY too low for that E content. You're likely having misfires and spark knock due to late timing. I suspect you disabled the knock sensors? You're not adding flex fuel timing either? Based on the log, the tune seems like it needs a little work. Maybe it isn't the Transmission?

[Alvin]

I agree. The timing during that period is very low.

It looks like IAT post blower is extremely high. There is a pid IAT sensor 3 that you should log on a LT4.

It also looks like there is a miss on the passenger side.

[kjlindgr]

I've attached another log from an earlier run. Here the manifold temps are definitely not as hot. The blower was put back on just a few hours ahead of these pulls so there was likely some air causing the higher intake air temps which then caused the ECU to pull timing leading into the runs.

On this run, it was much cleaner; however, right around 17 seconds into the log there was the same shuddering that occurred but then cleaned up. This run was also done in 4th gear vs 5th in the previous run.

This car was tuned by a very well known shop. I'm not going to name names, but it's not their first rodeo and in my mind are very reputable in the LS and LT world.

Regarding fueling - the fuel system on the car has FIC 30% over injectors, LPE HPFP upgrade, 38% over cam, and Weapon-X LSFP upgrade.

Thanks again for the suggestions guys:

run2-4thgear.hpl

[Alvin]

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?

[kjlindgr]

Thanks Alvin. Just a couple questions -

1. What are you seeing that gives you the indicator it's breaking up on the passenger side? Long term trims or something else?
2. I haven't tried running it with the converter unlocked. To be honest, I haven't paid much attention to the trans tune side of it because it was done by another shop. I can try that if you think I'm fighting converter lockup/slip. What gear do you recommend locking the converter at on these?

Thanks again everyone

[TriPinTaZ]

I've attached another log from an earlier run. Here the manifold temps are definitely not as hot. The blower was put back on just a few hours ahead of these pulls so there was likely some air causing the higher intake air temps which then caused the ECU to pull timing leading into the runs.

On this run, it was much cleaner; however, right around 17 seconds into the log there was the same shuddering that occurred but then cleaned up. This run was also done in 4th gear vs 5th in the previous run.

This car was tuned by a very well known shop. I'm not going to name names, but it's not their first rodeo and in my mind are very reputable in the LS and LT world.

Regarding fueling - the fuel system on the car has FIC 30% over injectors, LPE HPFP upgrade, 38% over cam, and Weapon-X LSFP upgrade.

Thanks again for the suggestions guys:

run2-4thgear.hpl

8ms+ injector time is spraying way into the compression stroke....

[kjlindgr]

I see it's running pretty rich during the run. Let me lean it out and see how far I can pull the injector pulsewidth down. Looking at some prior runs with stock injectors, stock HPFP, same cam, and upgraded LSFP, I was seeing about 750whp on the same ethanol content and similar boost. Very odd that these new injectors and pump are delivering fuel at a similar rate.

[TriPinTaZ]

I see it's running pretty rich during the run. Let me lean it out and see how far I can pull the injector pulsewidth down. Looking at some prior runs with stock injectors, stock HPFP, same cam, and upgraded LSFP, I was seeing about 750whp on the same ethanol content and similar boost. Very odd that these new injectors and pump are delivering fuel at a similar rate.

Your high side pressure is around 2000 PSI in those logs. It should be closer to 2900 as long as the FIC's can handle it. I've heard they often do not like much more than 2600psi or they stumble. You put 30% bigger injectors in, but turned the fuel pressure down by 30% which negates most of the improvement.

[kjlindgr]

Lingenfelter says their HPFP is LT1 based and recommends no higher than 2175psi, and states that their pressure relief valve bursts at 2755psi. That's why the rail pressure is significantly lower than stock. I'm wondering if the larger injectors are expecting the rail pressure of a stock pump? The injectors are 30% over, and the pump is 30% over but I'm wondering if you are right and I'm counteracting things with the lower rail pressure?

pump.png

[Joshinator99]

Lingenfelter says their HPFP is LT1 based and recommends no higher than 2175psi, and states that their pressure relief valve bursts at 2755psi. That's why the rail pressure is significantly lower than stock. I'm wondering if the larger injectors are expecting the rail pressure of a stock pump? The injectors are 30% over, and the pump is 30% over but I'm wondering if you are right and I'm counteracting things with the lower rail pressure?

pump.png

You can run higher pressure in the LPE BB HPFP than 2175 if you have a fuel lobe on your cam, but it?s not always helpful. At some point, as you ask for more pressure, your flow will reduce (all pumps work that way). So you have to balance IPW vs rail pressure. I would command 2175 IMO and see how your fueling situation looks (especially IPW). If IPW is well over 6.0ms then you can try to eek up the rail pressure to compensate but you?ll have to watch carefully?if it cannot do it, it?ll drop off like a rock.

I didn?t review your log but am assuming you?re running E? If so, I?d scale that back to reduce fuel system strain. Even E50 gives you most of the timing advance you want and significantly reduces load on the HPFP and injectors.

[TriPinTaZ]

Lingenfelter says their HPFP is LT1 based and recommends no higher than 2175psi, and states that their pressure relief valve bursts at 2755psi. That's why the rail pressure is significantly lower than stock. I'm wondering if the larger injectors are expecting the rail pressure of a stock pump? The injectors are 30% over, and the pump is 30% over but I'm wondering if you are right and I'm counteracting things with the lower rail pressure?

pump.png

That must be the version 1 pump. The version 2 pump supports 2900psi. The pump flows 10% more than the LT4 pump and 30% more than the LT1 pump. I only wonder if the pump is rated to flow 10% more than the LT4 pump with the LPE using LT1 pressures? If so I would assume it flows more than 10% than the LT4 at LT4 pressures. But this isn't clear at all and no one has ever been able to answer that detail that I have seen. Either way, turning down your fuel pressure to 1900-2000 psi has cut your potential fuel delivery by almost 30%.

[kjlindgr]

Think I'd be better off going back to the stock LT4 pump? This pump is about a year old so I'm not sure when they went from V1 to V2 of the pumps, but a lot of these issues started once I swapped it in.

I have no idea the power limits of the stock LT4 pump given enough low side flow.

[TriPinTaZ]

The V2 has been out for a while now. I guess it depends where you bought it from and if it was new old stock v1's or v2's but they still put that warning label on it. I have a new V2 pump that I bought directly from LPE on the way, I'll look and see if it has a warning label for pressure. But for sure I spoke to LPE and the v2 supports 2900 PSI.

[kjlindgr]

I bought this one from Texas Speed, and I thought it was drop shipped from LPE, but I could be mistaken.

I took a second look at the commanded pressures and it doesn't command the full 2175psi until higher RPM's. Looks to me that this is a pretty standard LT1 map. I think I should be commanding the full pressure earlier, but I'm not sure how early is too early. I have the tune attached if you would be willing to provide any suggestions.

Thanks again for the assistance

TUNE_0001.hpt

[TriPinTaZ]

Yeah makes no sense to put LT1 pressures in an LT4. You would be better off with the stock LT4 hpfp running 2900 psi with the 38% fuel lobe. If the lpe is indeed a v1 and you're afraid to run it at 2900, you should take it off and sell it and put an LT4 hpfp back in it. You will get more fuel that what you have setup now.

[kjlindgr]

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:
shudder_locked.png
run9_timing_ok_611hp.hpl


Unlocked log:
shudder_unlocked.png
run9_timing_ok_unlocked_601hp.hpl

[Joshinator99]

That must be the version 1 pump. The version 2 pump supports 2900psi. The pump flows 10% more than the LT4 pump and 30% more than the LT1 pump. I only wonder if the pump is rated to flow 10% more than the LT4 pump with the LPE using LT1 pressures? If so I would assume it flows more than 10% than the LT4 at LT4 pressures. But this isn't clear at all and no one has ever been able to answer that detail that I have seen. Either way, turning down your fuel pressure to 1900-2000 psi has cut your potential fuel delivery by almost 30%.

I have the V2 pump and it had the same tag, FYI.

The LPE HPFP flows much more fuel at 2175 psi than at 2900 psi. The name of the game is volume, not pressure. The bigger injectors will let you work with the lower pressure. I’m just under 1K WHP, running E50 and IPW of just over 5.0 ms, running 2175 psi through my LPE BB HPFP on a crappy +32% cam no less. You have to balance your desired HPFP pressure against your IPW and balance it out. If your injectors are smaller than ideal (+52 or +65 injectors are best obviously) then you can up the pressure a little to compensate as long as you watch HPFP pressure…it will drop out quickly if you try to ask for too much (along with corresponding jump in IPW). Hope that makes sense.

[TriPinTaZ]

I have the V2 pump and it had the same tag, FYI.

The LPE HPFP flows much more fuel at 2175 psi than at 2900 psi. The name of the game is volume, not pressure. The bigger injectors will let you work with the lower pressure. I’m just under 1K WHP, running E50 and IPW of just over 5.0 ms, running 2175 psi through my LPE BB HPFP on a crappy +32% cam no less. You have to balance your desired HPFP pressure against your IPW and balance it out. If your injectors are smaller than ideal (+52 or +65 injectors are best obviously) then you can up the pressure a little to compensate as long as you watch HPFP pressure…it will drop out quickly if you try to ask for too much (along with corresponding jump in IPW). Hope that makes sense.

I tune a bunch of LT4 hpfp cam'd stuff but I am just now getting into the LPE big bore so this info along with your posts over on Camaro6 have been very helpful.(off topic)


I am now curious why lower pressure equals more volume. You would think its the other way around. Is the HPFP less efficient at higher pressures?

[Joshinator99]

I tune a bunch of LT4 hpfp cam'd stuff but I am just now getting into the LPE big bore so this info along with your posts over on Camaro6 have been very helpful.(off topic)


I am now curious why lower pressure equals more volume. You would think its the other way around. Is the HPFP less efficient at higher pressures?

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.