For 76mm make sure to run a larger T4 hot side. A T3/T4 is too small. I don't think I've ever seen a stock cam fall off like that. A stock intake system may have something to do with that as well.
It looks like the kit still needs some tweeking....but it's a good 1st effort. Congrats, you will have 1500rwhp monsters soon. Keep up the hard work.
Why does the torque fall off SO hard? Those turbos are far too big to fall off like that? Are you running rediculously small hotsides or a really small cam? What ignition timing are you running up top?
I dont have many dyno graphs to compare to but at 140 mph it has less of a split in hp and torque as the cpe 909 rwhp dyno graph. The turbos have a f1 exhaust wheel, .96 a/r's, and 3'' exhaust with no restrictions. The car has 15* at peak torque and 17* up top. Boost stays dead high 8's and low 9's.
Quote:
Originally Posted by Disturbed 01
For 76mm make sure to run a larger T4 hot side. A T3/T4 is too small. I don't think I've ever seen a stock cam fall off like that. A stock intake system may have something to do with that as well.
It looks like the kit still needs some tweeking....but it's a good 1st effort. Congrats, you will have 1500rwhp monsters soon. Keep up the hard work.
I would love to see some graphs of turbo kits on bone stock motor's for comparison. Maybe the fact that it is making torque and alot of it early in the pull makes it look like it drops more then it really does.
At 140 mph the cpe car is making about 90 ft. lbs less torque then hp, mine is maybe 75? I am not in anyway trying to compare his kit vs. mine its just that is the only graph I could find on a bone stock motor.
The CPE car is making MORE HP than torque (desirable) and you are making less HP than torque. Not only that, the CPE kit is using much smaller turbos to do so. I'd imagine you have a problem somewhere. I think you could run more timing up top. 15 to 17 is pretty mild. I haven't seen a turbo Viper graph like that anywhere outside the GT35 cars. I am not trying to be a dick, I am just saying I think you are leaving power on the table somewhere and it would be sweet if you could find it. If you held even 85% of that torque to redline, you'd be laying down 825. If you look at some of the other videos of Alan's car, you'll see on 11 psi, it put down 819 torque and 790 RWHP and that was with really mild timing (91 octane tune). Its really incredible how much difference a couple degrees of timing makes.
On the street, those turbos spool quite a bit more early. I might try to find a mustang dyno graph to show.
Uhhhh...you realize the CPE car is making MORE HP than torque (desirable) and you are making less HP than torque? Not only that, the CPE kit is using much smaller turbos to do so. I'd imagine you have a problem somewhere.
We are clear that his dynograph is on atleast 5 psi more then mine?
You do realize my twin 76mm car is making:
50ish ft. lbs. and 50ish rwhp more at 70 mph
100ish ft. lbs. and 75ish rwhp more at 80 mph
125ish ft. lbs. and 100ish rwhp more at 90 mph
180ish ft. lbs. and 150ish rwhp more at 100 mph
50ish ft. lbs. and 60ish rwhp more at 110 mph
From there up he obviously has the advantage....as his car is on more boost.
I am assuming our speed's match just as good rpm's would, unless his car had some sort of gear changing.
You also realize that a big factor the the hp and torque graphs are when the car makes boost? If my car didn't make 8-9 psi at 4k then I am sure the torque would not be so high. Why is it desirable to make more hp then torque again? I think that depends on the user's end goals not some blanket statement.
Again I am not trying to directly compare kits, I just dont have anything else to compare to.
It's funny that in the beginning of the thread people were telling me about blowing up the stock motor and how stupid it was to use such large turbo's. I show up with a dyno graph of a car making great low end power, on low boost, low timing and now people are telling me I am leaving power on the table. I understand and after the customer enjoys the car for awhile, we will have our own dynograph with more boost.
Last edited by fasttrack : July 1st, 2009 at 03:11 AM.
We are clear that his dynograph is on atleast 5 psi more then mine?
You do realize my twin 76mm car is making:
50ish ft. lbs. and 50ish rwhp more at 70
100ish ft. lbs. and 75ish rwhp more at 80
125ish ft. lbs. and 100ish rwhp more at 90
180ish ft. lbs. and 150ish rwhp more at 100
50ish ft. lbs. and 60ish rwhp more at 110
From there up he obviously has the advantage....as his car is on more boost.
You also realize that a big factor the the hp and torque graphs are when the car makes boost? If my car didn't make 8-9 psi at 4k then I am sure the torque would not be so high. Why is it desirable to make more hp then torque again? I think that depends on the user's end goals not some blanket statement.
Again I am not trying to directly compare kits, I just dont have anything else to compare to.
Well, on 11 psi on 91 with virtually no timing, his car made 819 torque and 790 RWHP. Other CPE kits have been dyno'd on mustangs and never once have they had a torque anything like your's except when they ran virtually no timing at all (like this creampuff on 10 psi...and yes I know this is a dynojet example)
I just think you need some more timing. The reason it is desirable to have more HP than torque is because otherwise the acceleration just spikes and dies. I see it as wasted potential.
As far as comparing to his dyno graphs, PBJs dyno doesn't load the cars hard at all. As I said, on the street, those turbos are spooled up by around 3000 RPM vs. over 4000 on this dyno.
Last edited by The Former PFR : July 1st, 2009 at 03:17 AM.
What do you think would happen to torque if I could feed it 10 psi at 2000 rpms? The high torque is just a function of the car spooling quickly. Increasing timing doesnt make torque go away. If I put a much larger exhaust a/r on the car and it spooled 1000 rpms slower, it would not make anywhere near the same torque.
What do you think would happen to torque if I could feed it 10 psi at 2000 rpms? The high torque is just a function of the car spooling quickly. Increasing timing doesnt make torque go away. If I put a much larger exhaust a/r on the car and it spooled 1000 rpms slower, it would not make anywhere near the same torque.
No, increasing timing makes torque stay up. I have been at mustang dyno sessions with meaningful boost under 3000 RPM. There wasn't any massive increase in torque there over up top at any part of the power curve. Yes it was higher in the mid-range, as is a stock Viper V10 at that point, but it didn't look like a nitrous powerband and it certainly wasn't higher way down low. If the turbo system and tuning is done well and the car is not octane limited, I would expect to see the line be a smooth arc. As can be seen on Jody Gleason's car (where he was limited to something insane, like 13 degrees of timing), the torque falls off fairly hard up top. Have you measured EBR?
This is John D'Amico's car on ~9-10 psi using a bone stock engine. However, this was done on a Mustang Dyno.
The only time an engine should have some massive peak (compared to the NA engine) in the low-mid band seen when you achieve peak boost early is if the backpressure of the system is way too high. Otherwise, the curve should look similar to the NA engine with the same cam, just higher and maybe with a little nicer torque curve up top.
Last edited by The Former PFR : July 1st, 2009 at 03:38 AM.
That's not true, look at the modular motors...those cars dont make shit for torque. Throw a whipple or a KB on them and they make tons of torque arcoss the board. Those motor's aren't high in backpressure are they?
I've got a 410 cu in LS1 z06 at my shop that makes 1100 rwtq and 1000 rwhp, just a tad over 2:1 backpressure ratio.
I have not measured backpressure on this system, but could you even imagine it would be high? This thread started with people telling me these turbo's are TOO LARGE not too small. I have used these same turbos on this viper in single applicactions with 346-370 cubic inch motors making 700 rwhp+ at a 2:1 ratio.
We are only tring to help. It's nice to see someone come along and make a new Turbo system. From what we know now, your turbo is sized right for this car. Twin 76's are about perfect for street/strip work.
With the TQ falling off up top, I'm sure we have a restriction some place. While you can add more timming it will make more power up top and will help. If the restriction is not in the exhaust side, I would still look at the intake.
Something to remember as well is that the intake mani on these cars is setup for low end TQ. While on a turbo car it does not matter as much....it still matters. Swap that stock Gen II intake mani for a ported Gen III with larger TB, and I bet you will see that tq drop off less on the top.
That's not true, look at the modular motors...those cars dont make shit for torque. Throw a whipple or a KB on them and they make tons of torque arcoss the board. Those motor's aren't high in backpressure are they?
I've got a 410 cu in LS1 z06 at my shop that makes 1100 rwtq and 1000 rwhp, just a tad over 2:1 backpressure ratio.
I have not measured backpressure on this system, but could you even imagine it would be high? This thread started with people telling me these turbo's are TOO LARGE not too small. I have used these same turbos on this viper in single applicactions with 346-370 cubic inch motors making 700 rwhp+ at a 2:1 ratio.
Making tons of torque across the board is exactly what you should expect with a whipple supercharger. Looking at whipple's products, the entire torque curve is lifted a very similar amount. As far as concerning the Vette engine, a 2:1 backpressure ratio isn't exactly something to write home about, so having more torque than HP doesn't surprise me. It seems that your turbos are of appropriate size, which is why I suggest timing. However, without seeing the system, I can't say for sure it isn't a restriction problem.
We are only tring to help. It's nice to see someone come along and make a new Turbo system. From what we know now, your turbo is sized right for this car. Twin 76's are about perfect for street/strip work.
With the TQ falling off up top, I'm sure we have a restriction some place. While you can add more timming it will make more power up top and will help. If the restriction is not in the exhaust side, I would still look at the intake.
Something to remember as well is that the intake mani on these cars is setup for low end TQ. While on a turbo car it does not matter as much....it still matters. Swap that stock Gen II intake mani for a ported Gen III with larger TB, and I bet you will see that tq drop off less on the top.
Help that helps
PS: Are you going to start selling kits?
Disturbed.
The customer is perfectly fine with the results, but I am sure the car will get turned up in the future. I would much rather turn the car up a few pounds of boost, then to spend the money on intake manifold swaps. We will save that for when the car gets a built motor.
I would love to sell some of the kit's but I dont expect to sell many off of just one car, it seem's thing's only come EARNED around here, lol.
Quote:
Originally Posted by The Former PFR
Making tons of torque across the board is exactly what you should expect with a whipple supercharger. Looking at whipple's products, the entire torque curve is lifted a very similar amount. As far as concerning the Vette engine, a 2:1 backpressure ratio isn't exactly something to write home about, so having more torque than HP doesn't surprise me. It seems that your turbos are of appropriate size, which is why I suggest timing. However, without seeing the system, I can't say for sure it isn't a restriction problem.
The torque drop is less then but similar to cpe's, it just looks worse because this thing spool's quickly, and make's alot of torque.
On street car's 2:1 is very common because I am always shooting to make the desired horsepower AND spool quickly. It is the car's that have large/oversized turbo's that can achieve the lower pressure ratio's. The corvette was also through full exhaust.
Fast, can you post some pics of the set up, and pics from under the car?
Thanks!
I thought that was illegal around here? When I first started working on this car I looked and pic's of anything other then the intercooler piping was few and far inbetween. I am working on getting some nice pics taken.
I thought that was illegal around here? When I first started working on this car I looked and pic's of anything other then the intercooler piping was few and far inbetween. I am working on getting some nice pics taken.
Please keep the information coming. What better way to understand turbocharging then listening to two turbo guys challenging each other.
Nope, I'm out. If he wants to believe that's an appropriate dyno graph for a twin 76 mm car, I am not gonna convince him otherwise. I think it shows a lot of potential with the spool time ect and I would congratulate anyone that builds their own system. My guess is that there is probably some little detail somewhere holding it back and given their plans to build the car higher and higher, I expect to see problems resolved.
Finally got a chance to get the car to the track, conditons were not best by any means(about 35 degrees). The car is on the wastegate springs only with no boost controller, and drag radials. Preety happy with the results I know it will go much faster with some seat time and a warmer track.
hahhaa, got a kick out of your last video with the revo. i have one too. fun as hell. take it to the dunes with little paddles on it and race built banshees. prob is i win the first 50-60 ft, haha. need to adjust your second gear shift down, lol.
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