LLT Twin Turbo

[TJ91]

Update?

[Maniature]

update?

[Fabberge]

[TJ91]

Tuning still an issue?

[Fabberge]

talking to trifecta now. looking for 2nd opinion i guess.
my tuner, which is really good, is saying there is too much back pressure. that stock manifolds are no good. we already looked at aftermarket options but we want to get a 2nd opinion before we include yet another item in the LLT kit.

[alice]

I run stock manifolds and have had for the past 3 years. I have never had an issue or problem. My 2010 LLT has rear mounted Borg Warner EFR twin turbos and as I told you, I have a 4" MAF charge tube as well. Fueling has never been an issue. Vince at Trifecta suggested the larger 4" MAF charge tube 3 years ago, then he did the tune and the car is a beast. Never had an issue or problem in 30,000 miles of daily driving. Do not understand what all the fuss is about. Vince nailed my tune years ago.

[GO BIG ORANGE]

Alice, this build fabberge is working on is my Camaro. IS there a way to private message you about your build?

[alice]

I don't know what problems the tuner is having. Looking at your engine compartment, things look pretty good. The only thing that sort of bothers me is how short the 4" portion of the charge tube is at the MAF. Mine is much longer. Air acts funny when you have short transitioning between diameters, especially when a MAF sensor is trying to take readings. Turbulence could be occurring in this short 4" run and really playing havoc on the MAF's ability to read in a stable environment. I may be wrong but I would add or preferably remake the 4" run to be as long as you can. Look at the picture of my charge tube. Also, you could try installing a Treadstone air flow straightener about an inch or two in front of the MAF. They really work well in getting the air to behave better for the MAF sensor. I have one in mine. Maybe this is what condition the tuner is fighting. Also, if the tuner is sure that back pressure is a problem, well, it's not the manifolds, it could be the turbine housing A/R ratios being too small. Check with the turbo manufacturer and verify this is not an issue. Other than that, I am at a loss. Don't know exactly what the tuning difficulties are, what areas.

[alice]

Take a look at the pictures of my engine. This might be of help.

[Fabberge]

Originally Posted by alice

I don't know what problems the tuner is having. Looking at your engine compartment, things look pretty good. The only thing that sort of bothers me is how short the 4" portion of the charge tube is at the MAF. Mine is much longer. Air acts funny when you have short transitioning between diameters, especially when a MAF sensor is trying to take readings. Turbulence could be occurring in this short 4" run and really playing havoc on the MAF's ability to read in a stable environment. I may be wrong but I would add or preferably remake the 4" run to be as long as you can. Look at the picture of my charge tube. Also, you could try installing a Treadstone air flow straightener about an inch or two in front of the MAF. They really work well in getting the air to behave better for the MAF sensor. I have one in mine. Maybe this is what condition the tuner is fighting. Also, if the tuner is sure that back pressure is a problem, well, it's not the manifolds, it could be the turbine housing A/R ratios being too small. Check with the turbo manufacturer and verify this is not an issue. Other than that, I am at a loss. Don't know exactly what the tuning difficulties are, what areas.

It's the same A/R as the LFX kit but with new V-banded downpipes that are 3" so there is definitely no problem on the exhaust side of the turbo. As far as MAF pipe, we don't think that is the issue because a lot of GM MAF translator applications on other cars is even smaller of a bubble. We are waiting on trifecta right now to get back to us and give their feedback on the issue. But we'll look into the straightener for sure. We appreciate the feedback for sure.

[alice]

With what you have said, seems exhaust side is OK and back pressure can be ruled out. That being said, I would like to explain what I see with the charge pipe design. Please note that I am only trying to help and not trying to create any argument. I'm sure you will agree that sometimes, small things can really create major tuning issues on some projects. I appreciate your vast knowledge and only want to give you any possibilities I may observe, for you to consider as a resolve.

What bothers me is not only the short 4" MAF tube length, which I agree, have seen on many other FI setups and may or may not contribute to tuning issues but more importantly, the slight angle upwards from the drivers side, smaller portion of the tube. Here is my explanation as to what may be happening. Consider the high velocity air mass coming up that slight angle. Looking from the front of the car, If you imagine a straight line from the center line of the smaller charge pipe diameter to the transition up to the 4" diameter MAF tube, you can see that the air mass is aimed at an angle to the MAF sensor. In my opinion, certainly, air turbulence and simply the mass of the high velocity air entering the large 4" portion of the tube wants to go in that angled straight line due to inertia but is being bent down in order to straighten it out so it flows perpendicular to the MAF sensor. I think a lot of "hell" is going on as the air stream is changing direction so quickly and the MAF is going nuts in it's readings. If this were my project and you agree that this is a plausible explanation of turbulence at this critical point, I would re-make the charge pipe with the following modifications: Fabricate the entry to the 4" portion of the MAF pipe with additional length of 4" pipe that is straight, ( removing that slight upward angle ) and install a 4" honeycomb air straightener (Treadstone part #ACH40, $26.20) a couple inches in front of the MAF sensor. The portion of the charge tube after the MAF is fine, as is. So really, there is not much work or expense to modify what you have. Just cut on the transitional weld at the front of the MAF tube and add a 4" straight section without that slight angle, add the straightener and you will eliminate a whole lot of turbulence. Yes, I could be wrong about my theory but at minimum, I think you must agree that you will most certainly improve clean airflow traveling around that MAF sensor and improve your tuning situation. I hope this helps and resolves or at least improves the stability of the MAF sensors readings.

[GO BIG ORANGE]

Brian, I found several threads this morning that deal directly with the pressure issues you have described. The threads all directly deal with a setup with the zl1 pump installed and they had to upgrade the factory fuel pump control module along with the pump in which they used an adm fuel pump control module to off set the fuel pressure issues and apparently the tune worked fine afterwards. Apparently the cars were shutting down just as you described with the same fuel pressure issues. I also read the fuel pump control module in the trunk has to be changed to the adm/zl1 module when doing the swap on an ls v6 or you will never get it tuned due to the pressure/flow issues. Hope this info helps.
http://www.camaro5.com/forums/showthread.php?t=268524
http://www.admperformance.org/index....control-module
http://www.camaro5.com/forums/showthread.php?t=65274
http://www.hptuners.com/forum/showth...-system-limits
http://www.camaro5.com/forums/showthread.php?t=344469
http://www.hptuners.com/forum/showth...2307-fuel-pump
http://www.hptuners.com/forum/showth...tage-min-table

[alice]

GO BIG ORANGE, you bring up another possibility. Something like this can never be ruled out but based on my experience installing the ZL1 fuel pump in my 2010 LLT twin turbo, I never had any issue. Don't know what to say. No modifications of any kind. Rock solid 45/48 PSI in non-boosted mode. In boost, the pump pressure goes up to 75 or 80 psi, which has always been normal on the Trifecta tune. I have boosted to 10 PSI and I have no fuel issues whatsoever, before or after the pump change. I did notice a difference when using the 50 HP NOS shot. The stock pump pressure would drop to 37/38 PSI momentarily but with the ZL1 pump, it stays at 45/48 PSI. I installed the ZL1 pump about 4 or 5 months ago. I never had any re-tune or change/modified fuel control module. The new pump did not upset anything. I have never had an engine shut down after installing the new pump. The forums have numerous installs of the ZL1 pump in LLT's and LFX's and none that I read had any issues as well, although maybe some I have not read, have.

Though you need to consider everything and there are lots of knowledgeable people on this forum with excellent suggestions, I would not rule this out but if others, including myself have changed out the pumps and had no issues, I would question this but still leave it on the list of possibilities. I still believe the more logical change to make first is the MAF charge tube modification, per my explanation. Then, if that doesn't work, what I would do in re-install the stock pump to rule out the ZL1 pump question. Wait until you know the pump change was the issue before adding modules, etc. You don't want to end up chasing your tail. I know this is a bit of work but I think you are very close to resolution. There are a number of LLT's that are turbocharged, tuned quite acceptable and running/performing fine. I agree, this is a head scratcher on your particular project but I just can't believe that something, probably fundamentally simple, is upsetting the apple cart. When troubleshooting problems, you must make a realistic list of possible solutions that makes sense, prioritize them and then correct each one, in order to rule it out and then go on to the next one. It's takes time, $ and a whole lot of patience. That is what I have learned in my career as an Engineer. I hope this helps.

[GO BIG ORANGE]

What kind of has me wondering about my post is a few of the links I attached talk specifically about the fuel pressure issues and not having changed out the fuel pump control module. I agree that its something minor at this point.