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Speed density: re-tune necessary after turbo swap? Tc78 to PT7675

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Old 04-25-2012, 12:03 AM   #1
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Default Speed density: re-tune necessary after turbo swap? Tc78 to PT7675

Will i have to get re-tuned if I switch from a TC78 to a PT7675? The car currently has a 3" downpipe thats about 3ft long and dumps after the K-member but I'd like to run a 3.5" or 4" out the front bumper if I switch to a PT7675.
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Old 04-25-2012, 05:50 AM   #2
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Yes, at least check the tune.
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Old 04-25-2012, 06:53 AM   #3
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Check the tune. I wouldn't go crazy on that dp out the front bumper. Why spend extra money and cut up a front bumper for very minimal gains. That turbo was designed for a 3 inch dp.
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Old 04-25-2012, 07:17 AM   #4
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That PT76 should flow more air than the TC unit. I would keep an eye on a/f @ WOT on the same boost level. Its possible you'll have to add some fuel.
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Old 04-25-2012, 07:42 AM   #5
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very curious to see graph overlays from the old to the new turbo. Please comment on difference in spool as well!
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Old 04-25-2012, 08:07 AM   #6
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Quote:
Originally Posted by icicleboy View Post
very curious to see graph overlays from the old to the new turbo. Please comment on difference in spool as well!
Same here. Those were the two turbos I shopped and in the end, price won because I'm poor. I'd love to know what I gave up for the money.
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Old 04-25-2012, 08:10 AM   #7
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About 150rwhp - 200rwhp.

Yes, you will most definitely need to retune. I've done this swap myself.
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Old 04-25-2012, 09:24 AM   #8
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Are you swapping to a cast 7675 or a new cea 7675?
If its a cast I would not expect that much gain.
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Old 04-25-2012, 09:38 AM   #9
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Definitely retune it.
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Old 04-25-2012, 10:41 AM   #10
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Quote:
Originally Posted by KingOfCold View Post
Will i have to get re-tuned if I switch from a TC78 to a PT7675? The car currently has a 3" downpipe thats about 3ft long and dumps after the K-member but I'd like to run a 3.5" or 4" out the front bumper if I switch to a PT7675.
Of course it needs re-tuned. Any modifications that affect the amount of air the engine consumes will require re-tuning. And a turbo swap is a pretty substantial change.
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Old 04-25-2012, 10:48 AM   #11
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Quote:
Originally Posted by spoolin turbo View Post
Are you swapping to a cast 7675 or a new cea 7675?
If its a cast I would not expect that much gain.
He will most definitely see a big difference especially as boost goes up. The turbine on the 7675 is giant compared to a TC76.
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Old 04-25-2012, 11:10 AM   #12
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Its funny to still see those 2 turbos because of the way differant companies label their turbos. 2 totally different turbos
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Old 04-25-2012, 11:48 AM   #13
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I spoke to my tuner about doing the same exact swap and whether or not I'd need a retune and if it would be safe to drive after the swap. His response was that I could do the swap and street drive the car without issue. he recommends that I get the tune touched up before romping on it though. Makes sense to me. It flows more up top so depending on how your car is tuned you would be fine to drive it, but get it tuned before you start pushing boost.

Let us know how you like the new turbo. I'm really curious to see dyno's and driving impressions between both units as I have a tc78.
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Old 04-25-2012, 04:17 PM   #14
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Quote:
Originally Posted by HydroStream6 View Post
He will most definitely see a big difference especially as boost goes up. The turbine on the 7675 is giant compared to a TC76.
So is the TC76 a 7668? Was/is it only available in that configuration?
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Old 04-25-2012, 04:41 PM   #15
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I made the exact same swap, they are both about the same physical size with the comp cover of the 76gts being 3/8" bigger in diameter. You will need a retune for sure from running a more efficient setup. Less back pressure and a higher flowing comp cover.
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Old 04-26-2012, 03:30 AM   #16
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Quote:
Originally Posted by HydroStream6 View Post
About 150rwhp - 200rwhp.
That much? I was hoping for 50-60.
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Old 04-26-2012, 03:32 AM   #17
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Quote:
Originally Posted by spoolin turbo View Post
Are you swapping to a cast 7675 or a new cea 7675?
If its a cast I would not expect that much gain.
I'm definitely going with the CEA wheel
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Old 04-26-2012, 03:32 AM
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