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I just replaced a TC78 (7868 .96ar) with a T7875 (1.15ar). I had to remove the AC condenser and slide the radiator back to get it to fit. It's still the stock radiator and two pusher fans and so far it's staying cool. I only have about 1/2" of clearance between the turbo and the radiator (PTS/PTK/ebay kit). The spring that used to make between 7 and 9 psi on the TC78 only makes between 3 and 5 on the T7875.
Well and now that you say that Rawr I'm not sure the engine would live much longer with a bigger turbo. It's probably pretty close to 500 rwhp and it keeps me shifting at 5,500 rpm so this might be the best compromise between performance and longevity. I think I'll reach out to my tuner again and plan on installing a cutout, if your got nasty with it open I'd be hard pressed to believe it wouldn't be beneficial with my setup.
FWIW I'm sitting around 600rwhp with the 9 pounds or so and nearly 180k miles on a sbe ls1. Buddy made 715ish on 17 pounds with next to no timing on accident, don't remember how the story went but think he ran out of meth and somehow lost his wastegate source the night before at the track so he got lucky his IAT's shot up and dropped down to 8 or 7 degrees of timing.
Bottom line, it's all in the tune how long the motor will live, plenty of guys making over 600 and going strong. I would turn up the boost and experiment before taking things apart honestly.
FWIW I'm sitting around 600rwhp with the 9 pounds or so and nearly 180k miles on a sbe ls1. Buddy made 715ish on 17 pounds with next to no timing on accident, don't remember how the story went but think he ran out of meth and somehow lost his wastegate source the night before at the track so he got lucky his IAT's shot up and dropped down to 8 or 7 degrees of timing.
Bottom line, it's all in the tune how long the motor will live, plenty of guys making over 600 and going strong. I would turn up the boost and experiment before taking things apart honestly.
That's sound advice Rawr, I'd have to agree. I think I'll finish out the combo, finish tuning, and all the other add-on I want to do like the cutout and maybe some meth and see where it stands. Get the oil under control as well pressure with a thicker weight oil perhaps. At least I have some good ideas for a replacement turbo when I out grow this one which who knows, maybe I won't because I'm not really looking for a 1K rwhp street car, I think 500-600 rwhp is right where I need to be.
I'm necro posting I know lol. I finally got a cutout installed which really helped the top end pull but I'm still hitting a wall at about 5800 rpm. The car definitely likes to party with the cutout open but I came across a deal on a almost new T7875 that I just couldn't pass up lol. So the TC7868 is gone and now I'm making room for the bigger T7875 which I think will work better with my stage 3 cnc ported 317's and big turbo cam. Here's a couple photos of the units so you can get an idea of the size difference which isn't huge but will require some modification.
I'd hazard a guess that you'll love the 7875 once you get all the bugs worked out. I run mine at 8-12, depending on how froggy I'm feeling, and its spool speed is ridiculous with a .96 A/R. I've heard that the 68mm turbine has a tendency to choke the exhaust flow, but I haven't seen this firsthand.
I'd hazard a guess that you'll love the 7875 once you get all the bugs worked out. I run mine at 8-12, depending on how froggy I'm feeling, and its spool speed is ridiculous with a .96 A/R. I've heard that the 68mm turbine has a tendency to choke the exhaust flow, but I haven't seen this firsthand.
That's great news Jack, I was hoping my spool speed wouldn't be too badly affected. I'm thinking I'll run this one with my 7 lbs. spring and see where I end up, had a couple guys tell me it will make less boost with the same spring than the TC78. The 68mm turbine sure felt like it was choking at 5800 rpm, the spool was lightning fast and with a manual and 4.10's it was hard to reel in so I'm hoping I'll lose a little torque down low and make more up top. I'll get some picture this weekend when I'm out in the garage shoehorning this bitch in lol.
Yikes. 4.10s?! Man... I have a bitch of a time maintaining traction in first and second gear with 3.42s. Can't begin to imagine running that kind of ratio with a turbo car.
What kind of allowance do you have for downpipe sizing?
Yikes. 4.10s?! Man... I have a bitch of a time maintaining traction in first and second gear with 3.42s. Can't begin to imagine running that kind of ratio with a turbo car.
What kind of allowance do you have for downpipe sizing?
I don't do anything in first because why, second requires a lot of throttle modulation and third is okay if I don't hit it too hard. It's not too bad and the gearing is perfect for cruising at 70 mph in 6th so I leave it.
The T7875 turbine outlet is still 3" and is bolting up to my existing exhaust without issue so that's nice. Then it's 3" mandrel bent all the way to the back of the trans then the cutout is under my feet so its loud AF when its open, it great lol.
Good to hear you got a new one going on, excited to see what you think.
Can you get a side by side picture of the two? I figured the only size difference would be the larger exhaust housing.
Sorry Stover, one unit was going and the other showed up so I couldn't photograph them together. The turbine housings are the same size and in fact the .96 is slightly smaller than the 1.15 in circumference other than that no change there.
The compressor housing is noticeably bigger though. from the turbine shaft to the outside edge that would next to the radiator its about 3/4" bigger so I'm gonna have to move some stuff around. I have a few ideas so I'll keep you posted on those and overall driving feel.
I'm very excited for this guy, I feel like I own a legit turbo now lol.
So the T7875 is in! It was a little bit of a pita to be honest lol. One of the T4 flange bolts is right under the bolt for clocking the housing and getting a bolt in there when using the Huron Speed hot side requires some creative engineering but it works. I was able to keep the AC but had to lose the washer bottle since I moved the bottom of the radiator forward about 1" to clear the T78 compressor housing but it worked great. I had to notch the top core support pretty heavily to make room for moving the radiator but all in all it looks good. A quick test drive revealed that the spool is almost as fast as the TC78 but the power up top is far better. Couple that with a turbine whine that's loud AF and its a win win for sure. I now have traction issues at the top of third which is awesome. Hopefully I will have the tune dialed in within the next few weeks in which I will report back. Cheers!
My experience of that turbo is that it doesn't start to run out of steam until right around 6300. Granted, this is based on its previous exhaust setup which was less than ideal and sounds similar to what you were running (compression bent tubing... ew).
Those traction issues sound familiar! Enjoy, but don't pull a Mustang =P
My experience of that turbo is that it doesn't start to run out of steam until right around 6300. Granted, this is based on its previous exhaust setup which was less than ideal and sounds similar to what you were running (compression bent tubing... ew).
Those traction issues sound familiar! Enjoy, but don't pull a Mustang =P
Bahaha, there will be no mustang antics here lmao. I think this guy will pull past that with the cutout open since its all mandrel bent just past the cutout. I'm also thinking about ditching my small spectre air filter and running a screen for local street blasts. I can't seem to locate how much the filter or the turbo flows but I'd bet its not enough.
Man... There's no way I'd run a screen on the street. There's way too much trash on the streets which I don't want to see get sucked up and spat into the intercooler or beyond. Have you thought about fabbing up some sort of pipe to relocate the filter location? Could mean that you'd be able to run something adequate for filtration, as I'm guessing that we're talking about the little turtlehead of a spectre filter here... Just my $.02
BTW- I'm currently just running a section of pipe pointed down-ish from the turbo, so don't have that mangled mess of an exhaust shop fail to contend with anymore. The plan is to run full exhaust at some point in the nearish future, but I'm just glad that the car's back up again after a three month hiatus due to snapping a k-member. The exhaust can wait a bit, as I'm just happy to be back on the road.
Yeah its tough because there is almost no room for a filter. I had a bigger K&N but it crashed into the radiator hose pretty hard so I ditched it plus i didn't have any provision for the breather inlet since I'm running a closed PCV system. I know lots of guys running nothing at all on the street and haven't had a problem but you can easily chalk that up to luck. I don't really race the car so whats the point if I'm choking this betty with a tiny filter for street use?
I'm running a Spectre filter on the same turbo. Dyno day ended up pulling it just to see if there was any power diff after my friend removed his crazy restricted intake off his Camaro. On my setup with hit hitting 15lbs or so there was no noticeable gain in power. I would honestly just keep the spectre on it rather then a screen or something.
I made a pretty big jump in the name of not having to jump again in 6 months. We put down 618/628 through our tc78/68 t4 1.15 but the car pinched off at 5800. For the sake of not doing things twice, i went ahead and cammed the short block and went with a billet s480/t4 1.25 theres 50rpm difference in spool time between the stock cam tc7868 and the cammed s480. Havent been to dyno yet, but it pulls past 6500.
Nice, see that was my issue is with my heads and cam it really choked up about 5,500. I'm looking to get more rpm out of it now hopefully in the 6,500 range. I took it around the block and with the old tune it feels like it did when I had the 10 lb. spring in the TC78 so I know its gonna rock. Hopefully I get my tune back this week and get a better drive. I scored some used 3.73 gears which should be here next week so that outta help load the turbo a bit more. Here's a pic of it in the car, you can see I had to move the entire radio forward about two inches but not a bad operation all in all.
I'm running a Spectre filter on the same turbo. Dyno day ended up pulling it just to see if there was any power diff after my friend removed his crazy restricted intake off his Camaro. On my setup with hit hitting 15lbs or so there was no noticeable gain in power. I would honestly just keep the spectre on it rather then a screen or something.
Wow that's really surprising but also great news since I'd rather not run a screen.
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