Results w/ video of swapping from TC78 to Comp Billet 7479

[1999Black_Z28]

Earlier this year I ended up selling my TC78 locally and after talking to Huron Speed, Comp Turbo, and PM’ing several people I decided to purchase a Comp billet 7479. I like how the TC78 spooled but it was starting to drop boost above 6,000 rpms and at 15+psi. Being a 6 speed that spends 99.9% of the time on the street I wanted a turbo that would keep spool the same while eliminating a little backpressure. So far the Comp turbo has exceeded my expectations in both areas.


My setup is a stock bottom end LS1 with 317 heads, 17gph of 50/50 meth, LS6 cam, stockish T56 with RXT and Moser 9” with 3.70s. Race weight is just over 3,700lbs.


My best ET with the TC78 at 14psi and 15deg of timing was 11.2x and best trap was 132.7mph.


Last Friday with the Comp billet 7479 at 14psi and 13deg of timing, my best ET was 10.54 and best trap was 135.9mph. I plan to add a little more timing back in but I’m still in the tuning phase with the new turbo. Timeslips and video below:

Overall I am very happy with the swap!


I’d like to give a big thanks to Jon at Huron Speed. Not only did he give me a great deal on the Comp Turbo, but he also went out of his way to send me a spare set of collector gaskets (to replace the copper ones I blew out early last week) so I could make it to the track on Friday.

And another thanks to Jeremy (nocooler) for taking the video.


Here’s a few pictures of the new turbo during install. The specs are billet 74mm compressor, 79mm (100 trim) turbine, 0.96 AR, 3” v-band discharge, 360 journal bearing.

[Superman09]

Awesome results Dave, it picked up quite a bit and I'm sure will keep on going with more boost as well! Enjoy!

[Nocooler]

Now we need to get you to powershift that ***** and see what it'll really do

Oh and if you put a momentary switch inline with the 2 step it'll only activate with the clutch and button pushed so if you let off either it deactivates. Stops the backfiring when it trips on the shift, if that bothers you.

After watching Dave's car and that mustang - it makes me want to strip my car down to the shortblock and turbo it - someone want a proven H/C/I and nitrous setup? haha

[1999Black_Z28]

Now we need to get you to powershift that ***** and see what it'll really do

Oh and if you put a momentary switch inline with the 2 step it'll only activate with the clutch and button pushed so if you let off either it deactivates. Stops the backfiring when it trips on the shift, if that bothers you.

After watching Dave's car and that mustang - it makes me want to strip my car down to the shortblock and turbo it - someone want a proven H/C/I and nitrous setup? haha

The backfire doesn’t bother me at all at the track and on the street I just set the launch rpm to match the limiter setting so it doesn’t activate.
I have been experimenting with powershifting again but it almost always trips my knock sensors due to the driveline slop in the locker (same crap for years….I just didn’t know it until I bought HPtuners). My options are to either replace the locker with a wavetrack or turn off the knock sensors at the track. I don’t have the budget for a wavetrack so that’s why I was lifting at the track. I did make one run where I didn’t lift and it was nice to carry boost through the shift but it was offset by a knock event resulting in no gains Maybe I will figure something out by the next time I go.

[birdie2000]

Awesome results! What rpm does it start to make boost and what rpm is max boost reached at? What exhaust are you running?

[Nocooler]

I forgot you had a locker

Maybe try power shifting off the 2 step limiter and see if it still knocks. Then work something up with the 2nd output on the LNC or drop timing at your shift rpm.

[Tang]

Very nice!

[1999Black_Z28]

Awesome results! What rpm does it start to make boost and what rpm is max boost reached at? What exhaust are you running?

Thanks! It makes boost at anything over 2800 and 50% throttle...full boost is almost instant depending on gear(load) and rpm. I have a hooker maxflow muffler for the street and a dump tube for the track

I forgot you had a locker

Maybe try power shifting off the 2 step limiter and see if it still knocks. Then work something up with the 2nd output on the LNC or drop timing at your shift rpm.

unfortunately it's a false knock event from the driveshaft rattling around. Knock happens no matter what my timing is and it also happens when the lnc cuts spark between shifts

[OIF1VET]

Very nice!!!!