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Been awhile since I posted in the FI section. Thought I'd share my dyno results after my last tune. I had to compile data into excel since the two runs were done at different shops, so numbers aren't exact.
Run 1 Modifications:
Results:
Max Power = 303.65; Max Torque = 368.47
Thoughts:
I'm curious if the car might have had a bad pull this day, but it's the only sheet I have to compare too. Low numbers might have been due to low boost, or transmission inefficiencies.
Run 2 Modifications:
Results:
Max Power = 384 @ 4037 RPM; Max Torque = 609 @ 2056 RPM
Thoughts:
I'm almost certain my stock transmission and TC are hurting me at this point. Additionally I know the T76 with the T4 frame is a choke point for this large motor. Boy does it spool fast though!
Next Plans:
I'm kind of curious how far this motor can go on the stock 98 heads, LS6 intake, and the little T76.
I would go back to the dyno and verify those numbers. If they are legit and the turbo is choking it putting the converter in it would have the stall above the power band. I would fix the no power above 3500 and then worry about the converter.
I have been curious as to way the car is so low on HP. I know autos are horrible on the dynos for pulling high HP numbers, so was thinking it could be because my stock transmission and/or TC can't hold/transfer the power.
I can even feel it in the old butt-o-meter. Low RPMs the car pulls hard, but as soon as I get in the upper RPM range I can feel it struggling or fall flat.
Keep in mind both dyno runs are over 7 years apart (2009 versus 2016) at different shops. I just wanted to consolidate them into one graph to try and visualize the curve.
600 ft/lbs of torque at 2K RPMS; not HP. I was surprised it pulled that much torque, but I guess it is possible for such a large motor and a small framed turbo that spools very quickly. Was reading over 5 lbs of boost at 2K RPMS.
Torque is falling off a cliff. You have to fix that before changing anything. It feels good down low because that's the only spot its making power. By 4000 rpms you are down to n/a power and then it falls off even more. If you change converters or cam and the turbo is the problem you will lose the ability to even use the power you have down low now. (not that it is usable right now but you don't want to throw money at it and make it worse)
My thoughts exactly. When I was told the torque numbers versus the HP it was making, I was thinking "turbo diesel car hauler?" Part of the reason I wanted to post my graph is I have been scratching my head trying to figure it out.
I know I won't get high HP numbers through an auto (not looking at building a dyno queen), and I know this combo will produce a high torque, low HP setup due to motor displacement and quick spooling turbo. The whole curve looks strange to me.
Do you all think I am blowing the power through the stock trans (reason for torque curve looking the way it does)? I got the car with a blown, stock 4L60e so I just threw in another stock one from an 02 Trans Am to get it running again. I'm curious if I need to go ahead and get a built transmission (should support current and future goals), and re-run on the dyno to see what happens.
Also, reason for going with a 3400 stall or so is my peak HP is around 4K. I've heard stalls with FI you can typically add a few 100 RPMS to the stall speed.
Keep in mind I want to go with an 88 or 91mm turbo on a T6 frame in the future, but would really like to see what this kit will do on it first.
Sorry but that graph is all messed up. How are you only making 303HP on 5psi. Is there another dyno you can go to? You should be making that and more on motor alone.
Hell I was making 386 on a 100k mile 5.7 with cheap head, cam and bolt ons. Made over 675 on a bone stock 6.0 and 78mm turbo @12-13psi.
Your not going to want the stall higher than your peak hp. I would think that if the trans was slipping it wouldn't be holding enough to put up 600ft lbs. Are you handy with fabricating at all? If so you could cut the crossover and just run the turbo off of one bank to see if that stops it from choking. Obviously the side of the crossover that the turbo is on would need to be capped off and the other could just stay open from the other bank.
Sorry but that graph is all messed up. How are you only making 303HP on 5psi. Is there another dyno you can go to? You should be making that and more on motor alone.
Hell I was making 386 on a 100k mile 5.7 with cheap head, cam and bolt ons. Made over 675 on a bone stock 6.0 and 78mm turbo @12-13psi.
Can you post up AFR and some pics of your setup?
I probably should have left off Run 1 from my consolidated graph. That pull was done back in 2009, and I have a feeling I did not get a good run, or person running the dyno on that dyno day didn't make the pull right. Just put it in there for comparison reasons.
Here is my current dyno graph with the old pull from 2009 removed:
The car has a TTi Street kit installed (was built to retain A/C, emissions, etc.) with nothing more than a alternator relocation.
Driver side hot side - log manifold that is fed from passenger cast manifold via crossover pipe. Then out through 3 inch downpipe which goes to a cutout. I had to pull everything out of the car awhile back to fix a crack that had developed in the manifold. Painted everything while it was off the car.
Maybe he dyno'd it in 1st gear or something. You did say it felt weak up top on the butt dyno though. The tq is already falling at 2000 rpm.
Could that be due to inefficiencies with the stock transmission or TC (slippage, etc.), or just a product of the turbo choking the motor off? I'm not sure how that would look on a dyno graph.
Based on the dyno results, the overall feeling of the car in the top end, and that I noticed some slippage in over-drive this past weekend I started suspecting that the transmission and a new torque convertor might be the next mod.
So let me be the first one to say that if it dynos low.... and it feels slow on the steet.... then you are in fact dynoing that low and there is something wrong with your setup. To give you an example, I once was asked to tune a car for a buddy, and it was a **** put together setup of SBE LS1 with an STS rear mount. The car literally dynoed 224rwhp at a whopping 1.5#'s of boost. The oddest thing about it, is the guy was actually happy with the numbers. Blew my mind. But he had more boost leaks than I could count without taking my shoes off.
So let me be the first one to say that if it dynos low.... and it feels slow on the steet.... then you are in fact dynoing that low and there is something wrong with your setup. To give you an example, I once was asked to tune a car for a buddy, and it was a **** put together setup of SBE LS1 with an STS rear mount. The car literally dynoed 224rwhp at a whopping 1.5#'s of boost. The oddest thing about it, is the guy was actually happy with the numbers. Blew my mind. But he had more boost leaks than I could count without taking my shoes off.
I agree. I know the turbo is too small for the 408, and the stock 98 heads aren't known to flow well. My gut tells me it's the transmission and/or torque convertor just based on how the car feels when it pulls on the street.
Problem with getting an inherited build is it's hard to know for sure what went into it (other than what you are told by previous owner).
9lb spring only getting 7psi is an indicator for boost leaks.
The interesting thing is my PLX boost gauge picks up 8 - 9 pounds pretty consistently, but the dyno results only show 7. At any rate I do need to check the hotside for leaks this weekend. I know the Deltagate II I have in the car is leaking. When I had it off the car to install the 9 pound spring I could see light all around the mating surface for the valve. Would love to change it out, but not sure if I can find a good gate that will fit where this one is (very tight spot).
Last edited by Pat-Man; 03-02-2016 at 05:40 PM.
Reason: Reworded and added more details
What's the A/R on the turbine side of the turbo?
What size is the compressor wheel?
Did I read it right that your injectors are at 80%DC with your current dyno setup?
What are the "custom cam" specs? Looks like someone advanced the crap out of the cam.
A/F curve would be useful as someone mentioned.
03-02-2016, 11:24 AM
Dyno Results - 1998 Z28 w/ 408 (LQ9) w/ T76 @ ~7lbs 
