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


KingOfCold
04-25-2012, 12:03 AM
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.

LS1NOVA
04-25-2012, 05:50 AM
Yes, at least check the tune.

SPRAYED 01
04-25-2012, 06:53 AM
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.

Sweet_SS
04-25-2012, 07:17 AM
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.

icicleboy
04-25-2012, 07:42 AM
very curious to see graph overlays from the old to the new turbo. Please comment on difference in spool as well!

milkplus
04-25-2012, 08:07 AM
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.

HydroStream6
04-25-2012, 08:10 AM
About 150rwhp - 200rwhp.

Yes, you will most definitely need to retune. I've done this swap myself.

spoolin turbo
04-25-2012, 09:24 AM
Are you swapping to a cast 7675 or a new cea 7675?
If its a cast I would not expect that much gain.

123quattro
04-25-2012, 09:38 AM
Definitely retune it.

stevieturbo
04-25-2012, 10:41 AM
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.

HydroStream6
04-25-2012, 10:48 AM
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.

SPRAYED 01
04-25-2012, 11:10 AM
Its funny to still see those 2 turbos because of the way differant companies label their turbos. 2 totally different turbos

willizm
04-25-2012, 11:48 AM
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.

spoolin turbo
04-25-2012, 04:17 PM
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?

Nitroused383
04-25-2012, 04:41 PM
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.

KingOfCold
04-26-2012, 03:30 AM
About 150rwhp - 200rwhp.

That much? I was hoping for 50-60.

KingOfCold
04-26-2012, 03:32 AM
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