New Turbo "In"... Tuning Tonight!
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
New Turbo "In"... Tuning Tonight! Well my PT7875 arrived yesterday 
Got the TC76 out and snapped some pics of the two next to each other. The 7875 is definitely larger, but it fit!
I need to trim some sheet metal around the compressor outlet since it's a little "longer". Going to do that tonight and start tuning.
I'll update here as I progress. Thanks to everyone for all of the info that everyone has helped with with in choosing my new turbo!
Got the TC76 out and snapped some pics of the two next to each other. The 7875 is definitely larger, but it fit!
I need to trim some sheet metal around the compressor outlet since it's a little "longer". Going to do that tonight and start tuning.
I'll update here as I progress. Thanks to everyone for all of the info that everyone has helped with with in choosing my new turbo!
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
How much did the Comp 8079 billet set you back?
Engine is a forged 370, Diamond dished pistons, Scat rods, stock crank, LS6 cam. ~9.2:1 compression. Stock 317 heads with studs and 3 layer MLS gaskets.
Trans is a home built 4L80e with TCI computer.
Rear is stock with 3.46 gears and upgraded shafts.
I'm done at 3 today so I should be able to get it running in a few hours. Will be interesting to see how much AFR changes with JUST the turbo swap.
Engine is a forged 370, Diamond dished pistons, Scat rods, stock crank, LS6 cam. ~9.2:1 compression. Stock 317 heads with studs and 3 layer MLS gaskets.
Trans is a home built 4L80e with TCI computer.
Rear is stock with 3.46 gears and upgraded shafts.
I'm done at 3 today so I should be able to get it running in a few hours. Will be interesting to see how much AFR changes with JUST the turbo swap.
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Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
Got her up and running. So far so good. Definitely less back pressure. I had to run an 18lb spring in the gate with the TC to get 15lbs boost. I unscrewed the boost controller all the way and the first time I romped on it, it went right up to 18lbs. Forgot I had that heavy of a spring in there. So back pressure is down for sure. Swapped to a 12lb spring and did some pulls on 12lbs and then cranked the boost controller up to 14lbs when all looked good. Feels pretty good so far. Going to keep upping the boost slowly as I tune. I'll keep the updates coming!
Thread Starter
Joined: Nov 2004
Posts: 1,273
Likes: 3
From: Rochester, NY
I am surprised that it's not taking much more fuel. It was tuned pretty rich on the TC, high tens across the board at 15psi. On the new turbo, at 14psi, without changing the fueling, it's like 11.5and dips down to about 11.1. So it kinda tuned itself haha. I'm just surprised it's not leaner. Going for more boost tonight after work. Hope the heads stay where they are!
9 Second Truck Club
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From: Colorado Springs, Co/ Central, Ca
I am surprised that it's not taking much more fuel. It was tuned pretty rich on the TC, high tens across the board at 15psi. On the new turbo, at 14psi, without changing the fueling, it's like 11.5and dips down to about 11.1. So it kinda tuned itself haha. I'm just surprised it's not leaner. Going for more boost tonight after work. Hope the heads stay where they are!
If not I'd say it's time for some LS9 gaskets. If you have any logs / scans to compare spool up rpm of the two turbo's I'd appreciate it. People say this turbo should spool similar to the TC76 but I don't believe them without seeing data Maybe in your case of being on a 370 it will spool quicker with less back pressure.
Maybe in your case of being on a 370 it will spool quicker with less back pressure. 