78/75 on Lq9, or?????
Big tradeoff most people seem to not understand. Bigger cubes are better off boost, but smaller cubes do a lot more from a smaller turbo because of backpressure ratio. A 2jz will always make more than an LS1 with the same size turbo right up until it pukes its guts all over the track. That same ls1 will always make a better street ride. They both put out the same amount of exhaust at any given horsepower, but the bigger inch motor does so with less intake psi. This means less boost for power, but also means a horrible backpressure ratio when you turn it up.
I have ran and dyno tested quite a few 78/75 cars and there is no denying they are a cheap effective turbo that will go 700 wheel when cranked up. but there biggest issue is the .96 housing and the 75 turbine is a bit small for a 6.0 . they work and will make power but if you build a devided 2 1/4 hotside to a t6 96 mm turbine borg you will make a solid 100 hp more at the same boost. I don't know much about the 2nd gen turbos but if they are .96 and the same 75 mm turbine that is the limiting factor . the smaller the engine the better they work .
How bad do you all think a basic On3 (or whomever's) starter kit 70/65 T4 turbo with a .96 exhaust housing on a 4000# car with a 6.0?
On3 claims theirs can/will make 650rwhp...
With a non functioning wastegate, that turbo, on that car, wouldn't make more than 15# of boost, FWIW.
On3 claims theirs can/will make 650rwhp...
With a non functioning wastegate, that turbo, on that car, wouldn't make more than 15# of boost, FWIW.
On The Tree
Joined: Jan 2009
Posts: 104
Likes: 9
From: central fl
I have ran and dyno tested quite a few 78/75 cars and there is no denying they are a cheap effective turbo that will go 700 wheel when cranked up. but there biggest issue is the .96 housing and the 75 turbine is a bit small for a 6.0 . they work and will make power but if you build a devided 2 1/4 hotside to a t6 96 mm turbine borg you will make a solid 100 hp more at the same boost. I don't know much about the 2nd gen turbos but if they are .96 and the same 75 mm turbine that is the limiting factor . the smaller the engine the better they work .
Picked up MPH, RWHP, or quicker ET?
or...all of the above? lol.
Weighing my options, so definitely appreciate the feedback.
I have 3" v-band exhaust, 4" inlet, and small 2.5" outlet, so am limited (right now) without some fab work.
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Verdad Gallardo On The Tree
Joined: Jan 2009
Posts: 104
Likes: 9
From: central fl
I cant really give examples other than one. I am carb blow thru and above 6k rpm car would go pig rich with on3 78/75. Nothing would cure this issue. Suspected it was back pressure. Upgraded to next gen and boom issue was gone. From that point i was able to tune my afr above 6k.
I cant really give examples other than one. I am carb blow thru and above 6k rpm car would go pig rich with on3 78/75. Nothing would cure this issue. Suspected it was back pressure. Upgraded to next gen and boom issue was gone. From that point i was able to tune my afr above 6k.
Now, I can't help but wonder if that's my issue.
Mine's EFI, but I have the baby On3 70mm, and at anything above 6# boost, I have been subtracting a good bit of fuel out. Something for me to definitely dig deeper into.
My biggest hurdle is running quicker than my car is NHRA legal to. Even with the little turbo, I'm going to be too close, or already past that point, so the better suited turbo (like yours) would definitely make me too quick... I guess I could always run it out for 800 feet and drift, lol.
Thanks again. Love the way your car launches and sounds BTW!
Well I went ahead and ordered the t4 billet 80mm with the 87x82 exh wheel. Hopefully it will be here by next weekend, so we'll see how that works out when it gets here. Now to figure out what to do with the old one........ anybody need a 78/75 with less than 500 miles on it?
How bad do you all think a basic On3 (or whomever's) starter kit 70/65 T4 turbo with a .96 exhaust housing on a 4000# car with a 6.0?
On3 claims theirs can/will make 650rwhp...
With a non functioning wastegate, that turbo, on that car, wouldn't make more than 15# of boost, FWIW.
On3 claims theirs can/will make 650rwhp...
With a non functioning wastegate, that turbo, on that car, wouldn't make more than 15# of boost, FWIW.
Car is a once a month bracket car, once in a while weekend toy...I chose the smaller turbo to try and stay slower than 11.50 on wastegate boost (5.5-6#) due to no rollbar. But I'd like to be able to turn it up to 14 or 15 for the much more lenient test and tunes, and street fun.
I was mainly just curious since everyone was saying the 78/75 that the OP has would be too small for his new 6.0.
My normal, pre-turbo, shift points were 6350 1>2, and 6200 on 2>3. It has seen 7200, but not on purpose, lol. It does feel like it levels off about 5500 or so, but I'm not sure if that is me trying to be conservative on timing (since I've not done much tuning to it yet), or if it's getting corked by the small turbo.
Yes, on my 6.0, the the instant boost torque is ridiculous, but I'd rather have a happy medium of power AND torque.
Like said, was just curious what you guys thought of a small 70 turbo, since everyone was steering OP away from his already bigger than mine, turbo.
I was mainly just curious since everyone was saying the 78/75 that the OP has would be too small for his new 6.0.
My normal, pre-turbo, shift points were 6350 1>2, and 6200 on 2>3. It has seen 7200, but not on purpose, lol. It does feel like it levels off about 5500 or so, but I'm not sure if that is me trying to be conservative on timing (since I've not done much tuning to it yet), or if it's getting corked by the small turbo.
Yes, on my 6.0, the the instant boost torque is ridiculous, but I'd rather have a happy medium of power AND torque.
Like said, was just curious what you guys thought of a small 70 turbo, since everyone was steering OP away from his already bigger than mine, turbo.
Teching In
Joined: Jun 2013
Posts: 2
Likes: 0
Well I went ahead and ordered the t4 billet 80mm with the 87x82 exh wheel. Hopefully it will be here by next weekend, so we'll see how that works out when it gets here. Now to figure out what to do with the old one........ anybody need a 78/75 with less than 500 miles on it?
I have ran and dyno tested quite a few 78/75 cars and there is no denying they are a cheap effective turbo that will go 700 wheel when cranked up. but there biggest issue is the .96 housing and the 75 turbine is a bit small for a 6.0 . they work and will make power but if you build a devided 2 1/4 hotside to a t6 96 mm turbine borg you will make a solid 100 hp more at the same boost. I don't know much about the 2nd gen turbos but if they are .96 and the same 75 mm turbine that is the limiting factor . the smaller the engine the better they work .
Well I went ahead and ordered the t4 billet 80mm with the 87x82 exh wheel. Hopefully it will be here by next weekend, so we'll see how that works out when it gets here. Now to figure out what to do with the old one........ anybody need a 78/75 with less than 500 miles on it?
I actually bought his old cast VSR 78/75 to replace my 70mm On3 turbo that I had on my 6.0/4L80 Trans Am.
Everyone said it would be too small and not be the right choice for a 6.0, but on my 3rd pass, my 4060# race weight car went 9.94@138 (conservative 3000rpm, transbraked, 4psi launch), and was logged at 142 mph before I let off at the end of the run. This was at the end of MAY, so not really what most would consider "boost weather"...lol.
On wastegate, footbraked, with zero boost at launch, it's 1st ever pass was 11.55@127.
All the online calculators say that at my race weight, and my MPH or ET, the car made 700 or more, to the tires, on the 9.94 pass. This was at 70+% ethanol, dual 340lph AEM pumps, stock feed/rails.
I say "made" because I've since upgraded to the Next Gen Billet 78/75, and there's no question it'll go faster/quicker.
Now, on wastegate, footbraked, with zero boost launch (when bracket raced), the car will go 11.20's at 129-130, in worse weather conditions. Waiting for November to make the Next Gen work a little harder. I also now have CHRS1313 dual 450lph pump setup, -8 PTFE feed, dual fed Holley rails, and -6 PTFE return, so hoping for (as in expecting) a new best coming soon.
FWIW, I purposely chose to stay with a .96 housing/open since the cast wheel, in the same configuration showed no sign of being restricted with just a 3" exhaust housing, with open cutout down by the starter...Very fun to drive on the street as well.
Has anyone seen the 7875 cast wheel, 1.25 ar "special build? 4" exhaust outlet, 3" compressor outlet, $369
wonder if this would be an upgrade from a billet wheel 7875 with a .96 ar, 3" exhaust outlet?
https://turbo4less.com/product/cast-...special-build/
wonder if this would be an upgrade from a billet wheel 7875 with a .96 ar, 3" exhaust outlet?
https://turbo4less.com/product/cast-...special-build/
Staging Lane
Joined: Aug 2017
Posts: 94
Likes: 6
From: Laurinburg NC
Has anyone seen the 7875 cast wheel, 1.25 ar "special build? 4" exhaust outlet, 3" compressor outlet, $369
wonder if this would be an upgrade from a billet wheel 7875 with a .96 ar, 3" exhaust outlet?
https://turbo4less.com/product/cast-...special-build/
wonder if this would be an upgrade from a billet wheel 7875 with a .96 ar, 3" exhaust outlet?
https://turbo4less.com/product/cast-...special-build/
I ordered one last week should be here on Wednesday, upgrading from a GT45 so I am happy.