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The TC78 is a 78 with 68 exhaust housing and the 7875 is a 78 with 75 exhaust housing..
So I just bought a new Turnbonetics 7875 for a decent price from a forum member to upgrade from my TC78... Has anybody done a back to back swap and seen what the increase is at the same boost level? From all my reading the 7875's advantage is from 5000rpm up the power climbs where the TC78 drops off. Did a lot of research and didn't get much info other then that.
So I'll list my questions and concerns below
1. Have you done a TC78 to T-7875 swap? If so tell me about it and what gains did you see? Does the 7875 make more power at the same boost level?
2. I LOVE the sound of my TC78! Is the 7875 as loud when spooling?
3. What are some of your guys trap's and ET's with the 7875?
I just made the swap from a TC78 to the T7575, billet wheel. So far I've been keeping it to 10lbs or less but it does seem to be consuming more fuel (haven't taken any data logs to verify). I'll be hitting the dyno here in a month or two and turn it up then.
There was a very noticeable difference in the way the two sound just crusing around town. TC78 had a much louder whistle to it.
I just made the swap from a TC78 to the T7575, billet wheel. So far I've been keeping it to 10lbs or less but it does seem to be consuming more fuel (haven't taken any data logs to verify). I'll be hitting the dyno here in a month or two and turn it up then.
There was a very noticeable difference in the way the two sound just crusing around town. TC78 had a much louder whistle to it.
Damn I didn't want to hear that . The sound might be my favorite part... I wonder if that's because the larger exhaust housing doesn't alow turbo to spool at lower rpm like the TC78?
That's kind of what I was thinking and it was sort of a let down lol.
Just a heads up but if your downpipe and wastegate dump are really crammed in then this won't be a simple bolt in swap. I had to extend both my downpipe and wg dump slightly to get it to fit right.
That's kind of what I was thinking and it was sort of a let down lol.
Just a heads up but if your downpipe and wastegate dump are really crammed in then this won't be a simple bolt in swap. I had to extend both my downpipe and wg dump slightly to get it to fit right.
Looking forward to the dyno numbers. I want to run one of turbonetics 7875 on my 5.3 vs the on3. I was going to use borg but messed up building my hot side no way in he'll I can fit the borg downpipe
I've never ran the TC-78. I owned one for a brief moment in time, and traded it for the 7875.
Here is a photo of the 7875 showing off her 75 mm turbine side. That's how I had to fit mine, put the turbine housing in the car, then slide the rest of the turbo into it.
I'm running mine on an LS1 with ported 317 heads, and it was still making more power at 6600 when I let out of it on the dyno, because I have the rev limiter set at 6700. I'm betting it would pull strong till close to 7K, on a 5.7. Here is the dyno chart.
I'm thinking you'll be a happy camper. I know I'm very pleased with the performance of this turbo.
Scotty how loud is it in the car? I'm looking to make 700rwhp as well, but hope it's still make some good turbo noises lol.
I am running a Borla XS Pro, which tames it down a little. You hear it more with the open down pipe. I can take the muffler off with the 1 bolt on the V Band clamp. I will likely do that before taking it to the track. There is no doubt it is a turbo car on the high way. The turbo whine does draw attention.
As far as the strange dip, no explanation there, but I've seen anomalies like that in dyno graphs many times before. Could be some strange dynamic, I doubt it is the converter though, but who knows? Maybe a little tire spin on the roller?
It is remarkable how close the graphs are, I think the main difference is the cam. My cam is not ideal for a turbo setup, so it costs me some midrange. Our midranges are really close, you have just a touch more, looks like 10-20 ft lbs torque difference in 4-5000 range. On the top end, I think my set up will pull harder, bigger cam, more displacement, if both are at 15 psi. What was the tranny you used? Mine makes more like 780 if the converter is locked, (made 1 locked pull before and gained over 60 hp locking it, and based upon that difference 780 would be my best guess if locked) I don't see the point of burning up the TCC just to get a dyno number, I only have a single disk convertor. Not sure a single disk can handle that much power for long.
As good as your numbers were, I may have just left that combo alone. I need to build more motor to go higher. I'm very confident that there is considerably more in the 7875. IAT's were only about 10 degrees above ambient at 15 PSI.
How about the turbonetics 7875? Is it pretty loud under slight throttle and full throttle?
Well at full throttle I can hardly hear the turbo, you can, but the engine sound really kind of over powers it. If your cruising along like in 2nd gear at like 3500, shifting it yourself it sounds like a jet, you cant hardly hear the motor for the turbo. I betting in a stick car this will happen all the time. I also get that big whoosh from the BOV when letting out of it after a short romp on the throttle. There is no doubt it is a turbo car, the vehicles in the lane beside you also know its a turbo car, unless they are deaf and retarded. Both my wife's and my daily are turbo charged vehicles 3.5 ecoboost V6s with the twins, you can't really tell they are turbo charged, they just feel like NA V8s. I actually own 6 cars, and they have 8 turbo chargers total on the 6 of them, kinda funny. This is undoubtedly a turbo car both in terms of noise, and the rush when it comes on. It really defines the car. Gotta love that whine.
Well at full throttle I can hardly hear the turbo, you can, but the engine sound really kind of over powers it. If your cruising along like in 2nd gear at like 3500, shifting it yourself it sounds like a jet, you cant hardly hear the motor for the turbo. I betting in a stick car this will happen all the time. I also get that big whoosh from the BOV when letting out of it after a short romp on the throttle. There is no doubt it is a turbo car, the vehicles in the lane beside you also know its a turbo car, unless they are deaf and retarded. Both my wife's and my daily are turbo charged vehicles 3.5 ecoboost V6s with the twins, you can't really tell they are turbo charged, they just feel like NA V8s. I actually own 6 cars, and they have 8 turbo chargers total on the 6 of them, kinda funny. This is undoubtedly a turbo car both in terms of noise, and the rush when it comes on. It really defines the car. Gotta love that whine.
Do you have any rough idea what compression ratio you are running with your current setup? I have to order a turbo and heads and am on the fence currently.
Do you have any rough idea what compression ratio you are running with your current setup? I have to order a turbo and heads and am on the fence currently.
My compression ratio is 11.4:1. My heads were milled to 60.5cc. There are a lot of people that will say this is too high. If your not going to run E85 or race fuel, that is probably true. I haven't tried 93 pump gas, but I would not expect it to work very well, I wouldn't be able to get much boost or timing to it before detonation. It would be a ragged edge motor. This was not planned, the motor was built to be a strong NA motor, and boost was put to it later.
I have run into a small group of people however that told me that's what I want. These guys are far more extreme than the normal crowd here on LS1Tech. They are racers running X275 and such. They all have over $100K in their setup, and a couple of them are approaching $300K. They have settled on wanting about 12-12.5 compression for their turbo cars. They run C16 and the like for fuel. The reason for this though is mainly class rules. They are governed by weight, and displacement also in many of the race series there is a limit to compressor wheel size. If you are limited by those things, adding compression is one of the only other things you can do to add efficiency and power. To quote "compression is power", while this is not exactly correct, it makes the point. As long as you have high enough octane fuel to support it, higher compression will always be more efficient and make more power.
If I were building a new engine tomorrow, which I'm considering. I'm shooting for 10.5-11:1. My 11.4:1 is working well now, but that is only at 15psi. I would probably go up to 22-24 psi on a new engine at this 10.5-11 range, and still run Ethanol. This will drive me up on the compressor map on my turbo, and make the turbo more efficient, currently I'm running off the right side of my compressor map over about 5500 rpm.
I've been judged, and been told I'm and idiot for boosting this engine at this 11.4:1. So conventional wisdom would say don't go here. however, 714 rwhp on 15 psi with a 346, through and unlocked automatic, and a muffler on it is a decent number. Also with this compression the engine is perky even when out of boost.
Was that through an auto or M6? Was 15psi the max for that turbo, or do you think it could still do more then that?
M6, it could definitely push more pressure but I imagine it would fall off at a much lower rpm as well. I saw some 25+psi boost spikes when I was running a stiff spring, not sure at what rpm though.
It is remarkable how close the graphs are, I think the main difference is the cam. My cam is not ideal for a turbo setup, so it costs me some midrange. Our midranges are really close, you have just a touch more, looks like 10-20 ft lbs torque difference in 4-5000 range. On the top end, I think my set up will pull harder, bigger cam, more displacement, if both are at 15 psi. What was the tranny you used? Mine makes more like 780 if the converter is locked, (made 1 locked pull before and gained over 60 hp locking it, and based upon that difference 780 would be my best guess if locked) I don't see the point of burning up the TCC just to get a dyno number, I only have a single disk convertor. Not sure a single disk can handle that much power for long.
As good as your numbers were, I may have just left that combo alone. I need to build more motor to go higher. I'm very confident that there is considerably more in the 7875. IAT's were only about 10 degrees above ambient at 15 PSI.
The only thing I didn't like about it was not being able to rev very high. Kind of annoyed me knowing the motor wanted more than the turbo could give.
02-02-2017, 09:31 AM
TC78 vs T-7875 turbo 
. The sound might be my favorite part... I wonder if that's because the larger exhaust housing doesn't alow turbo to spool at lower rpm like the TC78? 
