LLY: my custom big twins build

Subman

Subman

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Jun 27, 2008
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duratothemax said:
are there any aftermarket vvt's that are opened up on the exhaust side? I wish I could find more specs about the AVNT4094....

I would really like to keep the VVT...there has to be some way to go big(ER) twins with a VVT.

I do have a wastegate leftover from my MPI twins...hmm. But should I gate around the big turbo too? Im too cheap to buy a second wastegate; with the one I have sitting here what would you guys do...gate around the VVT or gate around the big(ER) turbo?

ben
Click to expand...

I talked to Nathan a little about the VVT 4094 and he wasn't too sold on it for twin applications. I'm running the non VVT 4094 on White Out as my small turbo and I probably am going to have to go bigger on the housing for what I'm doing. It spools quick, (until you fry the TC then it doesn't spool at all). You really need to get a drive pressure gauge hooked up Ben, you could be making close to twice as much drive pressure as boost at WOT. What are you egt's at WOT?
 
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duratothemax

duratothemax

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final pics everything installed...

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ben
 
duratothemax

duratothemax

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TrentNell said:
No need to gate around the 480 , but a gate around the VVT is a decent idea , if your going to run it hard ? if your not i wouldn't worry about it . And on the wistle , it seems the bigger the turbo gets it is more like a Woosh then a wistle then bigger you go . Once agan it looks great Ben , you should be proud :hug:
Click to expand...

thanks Trent. :)


ok thats interesting about the "woosh"...so maybe I dont have boost leaks, and the whooshing is just the big turbo being/sounding "bigger" than the original garrett (????) on my small MPI setup?

sucks, now I wont get as many double-takes from ricers cause it doesnt howl like a mad banshee as the MPI's do...

ben
 
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duratothemax

duratothemax

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Subman said:
Thought you guys were supposed to be up to your asses in snow??
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Thanks Ken. As for the snow, not now, it melted all of a sudden (im on the coast of CT)...I think we are done with snow for this winter. Its about 50* OAT right now..
 
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duratothemax

duratothemax

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ok now Im starting to wonder if the big turbo is even spooling at all/doing anything...?

When I really got into it with my "big" tune on my dsp2 switch (2000us or so??) It all of a sudden started to kind of make a loud whistle after a couple seconds of WOT acceleration.

When I logged my vane position, it appears that even at WOT the vvt wasnt opening beyond 31% or so for some reason. So basically theres "hardly any" exhaust pressure in the hot pipe to spool the big turbo...

I will have to go over and change some stuff in my tune because the VVT is obviously choking out the big turbo by a very large margin.

ben
 
sweetdiesel

sweetdiesel

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Aug 6, 2006
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Ben you could just get some cheap liquid filled gauges and get some data before changing your tune. How big r your injectors? How's the smoke? Sounds like you where just starting to get on the large turbo

the kit looks nice ! I like the way the turbo is posistioned
 
duratothemax

duratothemax

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no smoke with the stock tune or "bigger than stock" tune. The injectors are big dipper's 40%.

the odd thing is that shifting is all goofy on my "bigger than stock" tune??? With the MPI twins it shifted fine, but now its kinda violent at mid-throttle positions. I think that might be because I run a stock LLY TCM OS in the winter (so my auto high idle works), and not my "nice shifting" 01 TCM like I do in the summer.

ben
 
duratothemax

duratothemax

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well duh I just looked at the tune and for some reason the minimum vane position tables were set at 25???? I have no idea how or why, because I distinctly remember setting it at 12% when IdahoRob gave me some twins tuning help wayyy back when. Maybe at some point along the line I accidentally flashed an earlier tune into my truck that had the stock minimum vane position tables? Anyway "we fixed 'THUH-GLITCH'" (office space) and Im going out to try it in a minute...

ben
 
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duratothemax

duratothemax

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wow what a difference that made. All I did was change the vane position tables to 10%...

turbo is louder (still nowhere near the old MPI twins tho, darn), and all the lag that was there initially is gone. Pulls just as nicely as the MPI's with the stock tune now. Im definitely going to have to play more with the tune though to get it "dialed in" (sorry I like saying that because it sounds nerdy/funny) perfectly.

With the big tune it was a lot different... I was getting on the highway in tow/haul, 3rd gear, and I rolled into it hard/floored it at 40mph or so and the rear tires lit up and spun into 4th gear and kept spinning until I let out of it at 70mph or so and then it shifted into 5th. Yes they are stock sized tires (well, stock GMT-900, so ~32", not stock 245's) and pretty worn down, but I was still surprised

Before, with the old setup, it would maybe break the tires loose initially but it wouldnt have the balls to keep them spinning through 4th gear; it would hook up at the top of 3rd.

NOW Im sorry if your duramax has 800hp and the above scenario isnt impressive at all and makes you snicker, but just humor me for a minute here. I was amused because Id never felt my truck (or any fast dmax ive ridden in) pull like that before.

That was with a 2050us tune and 21* of timing. I dont think I will be turning it up because I dont need it anywhere near this fast for the street, and I have a stock LBZ short block (with LBZ pistons).

oh, and yes, it still has that f'ing ~3100rpm LLY unexplainable defuel that no one can figure out...whatever. :rolleyes:

ben
 
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S

Smokin LB7

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Jul 25, 2008
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duratothemax said:
wow what a difference that made. All I did was change the vane position tables to 10%...

turbo is louder (still nowhere near the old MPI twins tho, darn), and all the lag that was there initially is gone. Pulls just as nicely as the MPI's with the stock tune now. Im definitely going to have to play more with the tune though to get it "dialed in" (sorry I like saying that because it sounds nerdy/funny) perfectly.

With the big tune it was a lot different... I was getting on the highway in tow/haul, 3rd gear, and I rolled into it hard/floored it at 40mph or so and the rear tires lit up and spun into 4th gear and kept spinning until I let out of it at 70mph or so and then it shifted into 5th. Yes they are stock sized tires (well, stock GMT-900, so ~32", not stock 245's) and pretty worn down, but I was still surprised

Before, with the old setup, it would maybe break the tires loose initially but it wouldnt have the balls to keep them spinning through 4th gear; it would hook up at the top of 3rd.

NOW Im sorry if your duramax has 800hp and the above scenario isnt impressive at all and makes you snicker, but just humor me for a minute here. I was amused because Id never felt my truck (or any fast dmax ive ridden in) pull like that before.

That was with a 2050us tune and 21* of timing. I dont think I will be turning it up because I dont need it anywhere near this fast for the street, and I have a stock LBZ short block (with LBZ pistons).

oh, and yes, it still has that f'ing ~3100rpm LLY unexplainable defuel that no one can figure out...whatever. :rolleyes:

ben
Click to expand...

What were your EGTs?
 
JoshH

JoshH

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duratothemax said:
wow what a difference that made. All I did was change the vane position tables to 10%...

turbo is louder (still nowhere near the old MPI twins tho, darn), and all the lag that was there initially is gone. Pulls just as nicely as the MPI's with the stock tune now. Im definitely going to have to play more with the tune though to get it "dialed in" (sorry I like saying that because it sounds nerdy/funny) perfectly.

With the big tune it was a lot different... I was getting on the highway in tow/haul, 3rd gear, and I rolled into it hard/floored it at 40mph or so and the rear tires lit up and spun into 4th gear and kept spinning until I let out of it at 70mph or so and then it shifted into 5th. Yes they are stock sized tires (well, stock GMT-900, so ~32", not stock 245's) and pretty worn down, but I was still surprised

Before, with the old setup, it would maybe break the tires loose initially but it wouldnt have the balls to keep them spinning through 4th gear; it would hook up at the top of 3rd.

NOW Im sorry if your duramax has 800hp and the above scenario isnt impressive at all and makes you snicker, but just humor me for a minute here. I was amused because Id never felt my truck (or any fast dmax ive ridden in) pull like that before.

That was with a 2050us tune and 21* of timing. I dont think I will be turning it up because I dont need it anywhere near this fast for the street, and I have a stock LBZ short block (with LBZ pistons).

oh, and yes, it still has that f'ing ~3100rpm LLY unexplainable defuel that no one can figure out...whatever. :rolleyes:

ben
Click to expand...

That's awesome, Ben. Glad you're getting the kinks worked out.

What is the 3100 RPM LLY defuel?
 
TheBac

TheBac

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Apr 19, 2008
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Oh god...guys, dont get him started on that defuel issue again...it drove him nuts before and nobody was able to figure it out.
 
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