better numbers with smaller turbo! 404ci + 76mm
12-28-2010, 12:14 PM
#41
yes. 900-950rwhp
13psi through my current motor and turbo make more power than my old pt88mm 370cu on 22psi of boost.
with good heads(360cfm l92/ls3/afr) on your motor and a 88mm t6 turbo through a 6 speed you should hit 1000rwhp with a 6 speed at 17psi.
also i dont the title of the thread is misleading, a junk ebay 78mm of course will not out perform a nice 76mm gts. really the 76mm flows more lbs/min of air than the ebay 78mm
just to clearify, im not knocking your setup. i like the car, its very clean and looks sharp.
13psi through my current motor and turbo make more power than my old pt88mm 370cu on 22psi of boost.
with good heads(360cfm l92/ls3/afr) on your motor and a 88mm t6 turbo through a 6 speed you should hit 1000rwhp with a 6 speed at 17psi.
also i dont the title of the thread is misleading, a junk ebay 78mm of course will not out perform a nice 76mm gts. really the 76mm flows more lbs/min of air than the ebay 78mm
just to clearify, im not knocking your setup. i like the car, its very clean and looks sharp.
So you're making that kind of power with a 91mm turbo probably up in the 7k rpm area. So what? Of course I would make more power with a 91mm.
And I actually love the title. And that is EXACTLY what happened! This is the type of thread where people actually can learn something. This is a "bigger isn't always better" thread. The title at least draws people in, and gives them a little different perspective than every member on here saying, "just slap a pt88 on it and be done"
12-28-2010, 01:20 PM
#42
So you're making that kind of power with a 91mm turbo probably up in the 7k rpm area. So what? Of course I would make more power with a 91mm.
And I actually love the title. And that is EXACTLY what happened! This is the type of thread where people actually can learn something. This is a "bigger isn't always better" thread. The title at least draws people in, and gives them a little different perspective than every member on here saying, "just slap a pt88 on it and be done"
And I actually love the title. And that is EXACTLY what happened! This is the type of thread where people actually can learn something. This is a "bigger isn't always better" thread. The title at least draws people in, and gives them a little different perspective than every member on here saying, "just slap a pt88 on it and be done"
at 6k and 20psi of boost, its well over 1000rwhp
hey i was trying to be nice. im not tootin my horn on my setup here, but if i built a 404cu turbo motor that made the power yours did...id be pissed. 0.02
bigger cubes, bigger heads, bigger turbo= is better
properly sized turbo and tune= little lag
Last edited by cjg454ss; 12-28-2010 at 01:25 PM.
12-28-2010, 01:38 PM
#43
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Just wanted to say great numbers and great job getting the car dialed in to make this power on pump gas.
In response to this quote, what makes this PTE 76GTS a smaller turbo? The smaller compressor wheel or would it be a larger turbo because of the larger turbine wheel? Also got the Dang Bo, that turbo is bigger, look at the housing on that SOB? GTS is larger there also.
That said, I just installed a PTE 76GTS on my 4.8L and love it! Enjoy the new setup man, you did your research putting it together and you now you got some much due play time!
12-28-2010, 05:52 PM
#44
I'm sure you still have a ton of back pressure, but now you have less. Your extra power is a result of going from a 68mm turbine wheel to an 82mm wheel, it's really a no brainer. If you want even more power out of a 76mm turbo step up to a T6 flange with 92-96mm turbine wheel. This is really not an A and B comparison though, you switched dynos. I'm not hating or anything, just stating the obvious.
12-28-2010, 06:30 PM
#45
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I'm sure you still have a ton of back pressure, but now you have less. Your extra power is a result of going from a 68mm turbine wheel to an 82mm wheel, it's really a no brainer. If you want even more power out of a 76mm turbo step up to a T6 flange with 92-96mm turbine wheel. This is really not an A and B comparison though, you switched dynos. I'm not hating or anything, just stating the obvious.
12-28-2010, 06:30 PM
#46
Basically all the above is incorrect.
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
yes, if the backpressure is too high then one is diluting the intake charge with exhaust and there is less air for the engine to consume.
also, taking a quick look at the old turbo specs, it looks like it is maxed on on both the compressor and turbine sides, which would also explain why the "bigger turbo"(on the turbine side) also spooled faster and created max torque at a lower rpm
12-28-2010, 07:11 PM
#47
to the OP,
even the new turbo is too small for your engine. put an 88 on it and be done with it.
seriously though, you are OUT OF COMPRESSOR. have you tried upping the boost? does it make more power or just more heat? how about rpm? will it rpm further than 6000? what kind of IAT numbers are you seeing?
I put your numbers in a calculator, and your numbers are way to the right of the efficiency island of the 76mm turbo I tried. I would love to see the map of that 76gts. it even maxes out the t6 1.32 ar s400
http://www.squirrelpf.com/turbocalc/...=1&map_sel0=72
hell, my 325 ci build uses 2 t70s and trust me it is on the wastegate setting at 4500rpms so there is no way a single 76 or 78 would be enough for a 404ci . backpressure is excessive and compressor is insufficient.
even the new turbo is too small for your engine. put an 88 on it and be done with it.
seriously though, you are OUT OF COMPRESSOR. have you tried upping the boost? does it make more power or just more heat? how about rpm? will it rpm further than 6000? what kind of IAT numbers are you seeing?
I put your numbers in a calculator, and your numbers are way to the right of the efficiency island of the 76mm turbo I tried. I would love to see the map of that 76gts. it even maxes out the t6 1.32 ar s400
http://www.squirrelpf.com/turbocalc/...=1&map_sel0=72
hell, my 325 ci build uses 2 t70s and trust me it is on the wastegate setting at 4500rpms so there is no way a single 76 or 78 would be enough for a 404ci . backpressure is excessive and compressor is insufficient.
12-28-2010, 08:42 PM
#49
FormerVendor
Not trying to pick on you but again, incorrect. 76GTS will make over 900rwhp on a 346ci motor.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
12-30-2010, 03:25 AM
#52
Not trying to pick on you but again, incorrect. 76GTS will make over 900rwhp on a 346ci motor.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
12-30-2010, 04:17 AM
#53
Basically all the above is incorrect.
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
12-30-2010, 08:38 AM
#56
Not trying to pick on you but again, incorrect. 76GTS will make over 900rwhp on a 346ci motor.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
This combination, while improved, is still restricted on the exhaust side due to the displacement of the engine. A good indicator of that is the much higher tq than hp and hp tapering off early.
12-30-2010, 10:39 AM
#57
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This is what confuses me about turbo sizing, 78mm compressor, 68mm turbine vs 74mm compressor and 96mm turbine. How would you figure out which one meets your needs?
12-30-2010, 10:45 AM
#58
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Depends on how fast you want it to spool and how high you are spinning it. If you are only spinning to 6k on a 346, getting an 88mm turbine is overkill because it wont even spin until 5k or so.
12-30-2010, 10:52 AM
#59
12-30-2010, 10:56 AM
#60
yeah, the title is completely backwards. you could probably put a 70mm GTS on there and make almost the same power, the compressor really has nothing to do with anything in this test. All it shows is a LARGER turbo on the turbine side will always make more power, and the turbonetics F1-68 wheel is WAY too small for anything bigger than a 5.3 IMHO. Even the GTS will produce higher backpressure than I would like to see, as I dont like anything over 2:1