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While doing a little tuning on my truck after turbo install(I'm only a novice at best), I'm noticing the boost doesn't start untill up in the 3k rpm range.
To give an idea of what the tune looks like, and i'm not implying there isn't room for improvement, spark advance currently is around 18-21*
Fueling resulting in a 14.7 afr
my dilemma is, i have a dyno tune set up for August 14th i don't want to spend $750 to find out that power below 3,300 with this turbo will be disappointing, as it seems to be now. When i could use that money for a turbo in the rpm range i would be happier with. Another concern i have, i do not want to over spin (if possible) a smaller turbo or have it be a choking point when i am in the highr rpm. I also have a AEM boost controller that doesn't seem to make a difference when changing duty cycle, again, I'm new using those.
Currently have a Vsr 80/88 with a 1.30ar
motor is 398ci (6.52 Liter)
Turbosmart WG60 w/10lbs spring
A2A
525 lph pump
1000cc FIC (clinic)
-8 fuel lines, feed.
91 octane.
94 RCSB chevy truck
awd
Automatic
I know the current tune is not perfect, i just don't know what to expect with my setup. but a fun street car (truck) with some occasional track time.
I tried looking at turbo compressor map to see where my current turbo will be, but no luck.
For max hp = 74.1 lbs/min @ 14psi
for max mid = 35.8 lbs/min @ 14psi
according to some calculator I used online.
"that power below 3,300 with this turbo will be disappointing,"
No mention of what you have for a torque converter.
What does the exhaust system look like?
"that power below 3,300 with this turbo will be disappointing,"
No mention of what you have for a torque converter.
What does the exhaust system look like?
2800 stall, 4" that Exits out the fender, <24" in length. Cam is a sloppy stage 2.
Turbos don't spool instantly, especially larger ones like yours and to be honest, you don't want full boost at 3,300 rpm, it tends to break things.
My LS1 / S484 combo doesn't start making positive pressure until after 3,500rpm so if you're seeing pressure at 3,300rpm, I'd be happy.
That converter may be a little too tight as well, I run a Circle D Pro LS unit in mine that's probably in the 3,500-4,000 range since I can put it on the 2-step at 4,000rpm and make 13-14 lbs.
Also try driving it differently than you would an NA car, if you're cruising and want to get on it, try riding the brake a little while giving it more gas, it'll bring the turbo online faster when you let go of the brake.
You could also wire a 2-step into the brake pedal like I did so you lightly apply the brake to engage the 2-step, mat the gas, build boost on the 2-step then dump the brake and hold on lol.
Your 2-step engagement rpm will be 2/3 of the target rpm or it won't work so if its set for 3,000rpm, your engine rpm will need to be 2,000rpm or less to work for example when going down the road.
Turbos don't spool instantly, especially larger ones like yours and to be honest, you don't want full boost at 3,300 rpm, it tends to break things.
My LS1 / S484 combo doesn't start making positive pressure until after 3,500rpm so if you're seeing pressure at 3,300rpm, I'd be happy.
That converter may be a little too tight as well, I run a Circle D Pro LS unit in mine that's probably in the 3,500-4,000 range since I can put it on the 2-step at 4,000rpm and make 13-14 lbs.
Also try driving it differently than you would an NA car, if you're cruising and want to get on it, try riding the brake a little while giving it more gas, it'll bring the turbo online faster when you let go of the brake.
You could also wire a 2-step into the brake pedal like I did so you lightly apply the brake to engage the 2-step, mat the gas, build boost on the 2-step then dump the brake and hold on lol.
Your 2-step engagement rpm will be 2/3 of the target rpm or it won't work so if its set for 3,000rpm, your engine rpm will need to be 2,000rpm or less to work for example when going down the road.
thank you for taking the time to educate me!! Much appreciated!
I will look into adding a 2-step, with a a turbo it's kind of a must have?
What's the primary use of this truck ? Fun street toy with occasional track passes ? Guessing at least 4000 lbs ? What gear ratio and tire size ? When you are testing what trans gear are you in ? May not build boost quickly in first gear due to lack of load . What rpm range are you planning on ? I have opposite problem 6L 7875 .96 housing- boost is instant and traction a real problem in 1st and 2nd on street tires , but it noses over above 6000 rpm ( small cam too) Bigger exhaust housing I'm sure would help a bit . Have you run any logs ? With the g/cyl you need to log to determine where a certain rpm / map reading puts you. I'm on 91 octane plus W/M about 24° at 0 map over 4000 rpm . I would go ahead with the tune - or do it myself, if it doesn't spool fast enough after put a smaller AR exhaust housing on it . That would be an easy bolt on , isn't there a 1.10 or 1.15 available for those? Keep it simple , that would speed up spool and not throw the tune off , there would be no procedure to build boost , just mat it and hang on .
What's the primary use of this truck ? Fun street toy with occasional track passes ? Guessing at least 4000 lbs ? What gear ratio and tire size ? When you are testing what trans gear are you in ? May not build boost quickly in first gear due to lack of load . What rpm range are you planning on ? I have opposite problem 6L 7875 .96 housing- boost is instant and traction a real problem in 1st and 2nd on street tires , but it noses over above 6000 rpm ( small cam too) Bigger exhaust housing I'm sure would help a bit . Have you run any logs ? With the g/cyl you need to log to determine where a certain rpm / map reading puts you. I'm on 91 octane plus W/M about 24° at 0 map over 4000 rpm . I would go ahead with the tune - or do it myself, if it doesn't spool fast enough after put a smaller AR exhaust housing on it . That would be an easy bolt on , isn't there a 1.10 or 1.15 available for those? Keep it simple , that would speed up spool and not throw the tune off , there would be no procedure to build boost , just mat it and hang on .
Correct on questions 2,3.
3.73 gearing,
tire size is 275/60-20 (32-33").
i was not able to find a housing that is smaller then the current 1.30 that i can simply swap with, I would have to invest in a different turbo.
i will look at what log i saved and post it. When i am testing, i have kept it in 3rd, currently i have a 4l65e with a NP149 T-case.
do you use a 2-step?
Your AFR is 14.7 at WOT? Not good. Not good at all. Best to get that in line before worrying about anything else.
ya..i was a bit nervous about that, should be little richer, correct?
i only made one pull and noticed it, i have not drove the truck since. I will be adding more fuel
Correct on questions 2,3.
3.73 gearing,
tire size is 275/60-20 (32-33").
i was not able to find a housing that is smaller then the current 1.30 that i can simply swap with, I would have to invest in a different turbo.
i will look at what log i saved and post it. When i am testing, i have kept it in 3rd, currently i have a 4l65e with a NP149 T-case.
do you use a 2-step?
no 2 step for me , gearing and tire size should be good to load it. Just saw the 14.7 afr , I target 11.5 at anything over 5 lbs of boost , tapered down from 12.5 under 5 inches of vacuum to 0 vac .
You have the dual v-band housing I'm guessing, have you tried calling Viren to see what's available? I think if it were T-6 there are options but you may be stuck with the 1.3 . You have some extra cubes that will help , with a 4L65 you don't want boost to come too early - pretty likely you will kill it .
Correct on questions 2,3.
3.73 gearing,
tire size is 275/60-20 (32-33").
i was not able to find a housing that is smaller then the current 1.30 that i can simply swap with, I would have to invest in a different turbo.
i will look at what log i saved and post it. When i am testing, i have kept it in 3rd, currently i have a 4l65e with a NP149 T-case.
do you use a 2-step?
likely in that transfer case you have a 4 (might be 3) pinion planet. My son busted the ring gear in his so I put another ring gear in and a 6 pinion planet out of a heavy duty unit
likely in that transfer case you have a 4 (might be 3) pinion planet. My son busted the ring gear in his so I put another ring gear in and a 6 pinion planet out of a heavy duty unit
interesting, I'm not aware of there being a heavy duty NP149, NP149 are found in the 03-06 SS silverado, 00-02 Escalade/Denali. Maybe your thinking of the NP249?
You have the dual v-band housing I'm guessing, have you tried calling Viren to see what's available? I think if it were T-6 there are options but you may be stuck with the 1.3 . You have some extra cubes that will help , with a 4L65 you don't want boost to come too early - pretty likely you will kill it .
correct, i have the dual v-band, the turbo did have the T-6 with a 1.32ar. I have only been able to find the 1.30 from Vsracing.
Based on what you guy'shave shared, i think it is beneficial to continue improving the tune, and then maybe decide after that on what to do. I have a 4l80e and a extra T-case that will be swapped in once the 4l65e goes... or by next spring. Since the 80 has a 32 spline, i still need to swap out the input shaft of the NP149. Maybe the taller 1st gear in the 80e will help spool the turbo some? I was also going to use srock TC
correct, i have the dual v-band, the turbo did have the T-6 with a 1.32ar. I have only been able to find the 1.30 from Vsracing.
Based on what you guy'shave shared, i think it is beneficial to continue improving the tune, and then maybe decide after that on what to do. I have a 4l80e and a extra T-case that will be swapped in once the 4l65e goes... or by next spring. Since the 80 has a 32 spline, i still need to swap out the input shaft of the NP149. Maybe the taller 1st gear in the 80e will help spool the turbo some? I was also going to use srock TC
The stock torque converter in a 4l80 will be a miserable combination in your truck. Coming from some turbo Escalade with a 4l80 experience, there is no way I would go less than a 3000 stall in that combo, and that is being conservative. This will, however, necessitate a good quality converter and a decent trans cooler.
No one has asked if you have an et or hp goal , that could effect decisions. Agree that a stock converter will hurt performance and drivability especially if boost response is on the slow side . My combo actually drove well with the stock 4l80e converter but cam and turbo are both small . Guessing that with the stock converter and current tune/power it would be about .5 slower in the 1/4
ya..i was a bit nervous about that, should be little richer, correct?
i only made one pull and noticed it, i have not drove the truck since. I will be adding more fuel
At wot, out of boost (with pump gas) it should be in the 12's (I like 12.5:1 personally) but in boost, it better be in the 11's. 11.9 is good on 1-2psi but I start fattening it up as boost goes up. I run a touch over 20psi and its around 10.6-10.8:1 (this is what I do, its worked for me for years without having to replace a head gasket). 14psi will be around 11.2:1. So as you can see as I go up in boost, I go up in fueling. You see 14.xx afr in boost....you better let off quick.
14.7:1 is good for idle and cruise (very light load). I I increase load, I add a little fuel.
At wot, out of boost (with pump gas) it should be in the 12's (I like 12.5:1 personally) but in boost, it better be in the 11's. 11.9 is good on 1-2psi but I start fattening it up as boost goes up. I run a touch over 20psi and its around 10.6-10.8:1 (this is what I do, its worked for me for years without having to replace a head gasket). 14psi will be around 11.2:1. So as you can see as I go up in boost, I go up in fueling. You see 14.xx afr in boost....you better let off quick.
14.7:1 is good for idle and cruise (very light load). I I increase load, I add a little fuel.
No one has asked if you have an et or hp goal , that could effect decisions. Agree that a stock converter will hurt performance and drivability especially if boost response is on the slow side . My combo actually drove well with the stock 4l80e converter but cam and turbo are both small . Guessing that with the stock converter and current tune/power it would be about .5 slower in the 1/4
good to know about the converter! I would like to see 600-700hp at the wheels. But I'm really after good use able power..
The stock torque converter in a 4l80 will be a miserable combination in your truck. Coming from some turbo Escalade with a 4l80 experience, there is no way I would go less than a 3000 stall in that combo, and that is being conservative. This will, however, necessitate a good quality converter and a decent trans cooler.
i didn't relize a loose converter is what is needed with use of a turbo.
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Turbo dilemma 
