V8HUNTER

i have a t-78 turbo rx7 , and little confuse about the shift point , just wondering what's the best shift point for everyone with t-78 turbo. currently i shift at 7500rpm. here is my dyno sheet at 20psi.

V8HUNTER

here is my dyno sheet at 20psiIMG SRC="https://www.rx7club.com/ubb/image_uploads/450.jpg">

MikeL

V8HUNTER, that's a great looking dyno sheet! Do you have numbers for something like 15-16 psi?

As far as shift point, I don't have the T-78, I have the T-66 but, it looks to me on your dyno sheet that 7500 will be too low. The hp is still rising or at least isn't dropping near 7000. Do you have a sheet that shows a higher rpm? Why did they shut it down before 7000?

What is your turbine a/r and trim?

My T-66 setup with .96 p-trim turbine wants me to rev a little past 8000. Last night I went to 8400 on one 3rd gear run. I went that high because I wanted to see where the power would actually fall off. I see now that I want to shift at 8000, just before the power takes a dive.

Mike

MAZMAN

i think this will do it.

MAZMAN

NOTE:this is not my car but V8HUNTERS

V8HUNTER

on 15psi i dyno 403 RWHP, and the reason why they shut it off before 7000rpm it's because only had 280miles on new the motor, so they didn't want to push too hard.when do you start to biuld boost on your T-66 turbo? i don't know what's the turbine a/r, but it's a stock GREDDY T-78 turbo.

MikeL

WOW! 400+ rwhp at 15 psi! That is great! I haven't dynoed with my T-66 yet. I should get very close to that. I know that pluto with his 3rd gen did right at 400 at about 15 psi with the same turbo setup as I have. He also did 435 at 17 psi. I hope to do the same.

I understand letting off before 7k rpm with that fresh engine. You might get a little more power later.

When do I get boost? That's kinda hard for me to say because it's different dependant upon being stopped or not and which gear and speed if not stopped. I haven't dynoed it yet and, I haven't really done any drag starts with it.

I can give these examples though from driving and racing on the street, not from a stop:

I raced a ZO6 Corvette from about 45 mph in 3rd gear. We hit it at the same time and he was also in 3rd, both confirmed by the 'Vette driver. We stayed side by side for about two seconds so, I had enough boost instantly to keep him from pulling away. After the two seconds when my boost got up to about 14-15 psi, I ran, not walked away from him.

If I'm in fifth gear at about 50 mph, as soon as I push the gas I get a couple pounds of boost. It stays at that couple pounds for a while as rpm increases.

I'll get a datalog as soon as I have my notebook computer repaired.

Mike

V8HUNTER

wow! i didn't know that Z06 is that fast! so how bad did you beat the Z06? your car sounds like it's have turbo lag. when i shift from 3rd to 4th gear my boost kick in right the way.

MikeL

The ZO6 is a bad ****. Those guys are dynoing 330-340 rwhp stock and running 12.4-12.6, usually no higher if they can drive. They also have all of that power ready to go as soon as the pedal hits the floor. The 2002 model will be 405 bhp instead of 385.

Of course I have lag. When I raced the guy I was in 3rd gear at 3500 rpm. I made enough boost instantly to keep up with a 385 hp 3050 pound car! That ain't too bad. It took maybe the two seconds that I wrote about above to be at full boost. I put about two car lengths on him before 4th gear. He shut it down. I never shifted to 4th.

Drive your car in 3rd gear at 3500 rpm, about 45 mph. Smash the gas and see how long it takes to really get going. Do you have the 4.1 or 4.3 rear gear?

Mike

j9fd3s

iTrader: (3)

my t2 does that too, if i hit the gas it will get boost but i have to wait until it hits about 5k before it really comes on

mike