When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So I have some questions that hopefully someone can answer.
The car is an 01Fbody M6 with stock rear end.
Engine is a LS6 block with built bottom end.
Heads are patriot performance ported LS6 heads with dual 660 springs, ported Fast92 intake and pacesetter LT headers.
Until recently it had a 228 cam but recently changed to a TSP torquer V2 112 LSA cam.
Previously the car was tuned but never dynoed.
Just got back from getting the new setup tuned and dynoed. Car put down 394hp at 6100 and 382TQ at 3600
Was rather disappointed with the numbers and it honestly feels like it had more power before.
To me, how low rpm the TQ peaks at as well as it running out of power at 6100 and of course the low numbers all indicate something is wrong but no real idea what.
Any help anyone can provide would be greatly appreciated.
Thanks
The shop didn’t.
Honestly it was kind of a messed up deal. I made the appointment a couple months back and then had the brother in law take it in as I had to be out of town.
He is not a big car guy and didn’t get much feedback.
That dyno sheet is all kinds of messed up. Why do HP and Torque cross at 4500? They cant cross until 5252rpm. Its because there is no RPM on this curve, its TIME on the X-Axis, not RPM.
Chassis dynos with tires are notoriously unreliable, especially tire roller dynos, but if you are down on power look for the usual suspects, check cranking compression to see if the cam is right, fuel pressure, spark, the norm.
That dyno sheet is all kinds of messed up. Why do HP and Torque cross at 4500? They cant cross until 5252rpm. Its because there is no RPM on this curve, its TIME on the X-Axis, not RPM.
Chassis dynos with tires are notoriously unreliable, especially tire roller dynos, but if you are down on power look for the usual suspects, check cranking compression to see if the cam is right, fuel pressure, spark, the norm.
I guess I am confused on that. What does time on the X-axis indicate. I just thought it was RPM. What is the purpose of it.
Hopefully going to have time to check cranking compression tomorrow. What psi do you think it should be around. Or I guess more importantly how low can it be before it indicates a problem with cam timing
Fuel pressure is good.
Last edited by Rustyoldbird; 07-24-2023 at 12:25 PM.
I guess I am confused on that. What does time on the X-axis indicate. I just thought it was RPM. What is the purpose of it.
Hopefully going to have time to check cranking compression tomorrow. What psi do you think it should be around. Or I guess more importantly how low can it be before it indicates a problem with cam timing
Fuel pressure is good.
If your cam is installed straight the math says you should get a cranking compression gauge reading of close to 200psi at 10.5:1 static compression. Maybe a hair less.
To be honest 400hp through the tires to a dyno rollers isn't bad for 348 cubic inches, especially if it was a hot day and if you still have the stock torque converter or if its manual the stock rear gears that bigger cam will kill some of your low-end torque and throttle response. Maybe not optimal, but I doubt you have another 40hp to find somewhere.
If your cam is installed straight the math says you should get a cranking compression gauge reading of close to 200psi at 10.5:1 static compression. Maybe a hair less.
Sounds good.
Will check it tomorrow and let you know what I find.
Thank you for the help.
Last edited by Rustyoldbird; 07-24-2023 at 01:09 PM.
Sounds good.
Will check it tomorrow and let you know what I find.
Thank you for the help.
Sorry, added some info. Basically if this is still a 5.7, 400hp through the tires isn't bad. The difference between a hub dyno and a tire roller dyno can be as much as 20%.
Sorry, added some info. Basically if this is still a 5.7, 400hp through the tires isn't bad. The difference between a hub dyno and a tire roller dyno can be as much as 20%.
The biggest issue I have is not so much the dyno numbers but that it simply doesn’t feel like it has as much top end power as it did before I swapped cams. For example
Before at WOT the car would break the tires in 1st gear once it got up to about 4500-5000 rpm. Doesn’t do that anymore.
The guys that dyno tuned it thought it should have been higher to.
Just would hate to just leave some power on the table for no reason.
A once over on simple things is a good idea too like to make sure all the plug wires are snapped on firmly. I've definitely done some work before just to find I didn't quite get a plug wire clipped all the way on.
Definitely shouldn't have lost power with that cam.
Up to torque peak it looks like performance is as expected. Just above the hp/tq cross is very suspicious.
For some reason the operator logged time in seconds instead of RPM. That's why they don't appear to cross @ "5252" as they would if it were RPM on x-axis. Not sure why they'd do it that way.
A once over on simple things is a good idea too like to make sure all the plug wires are snapped on firmly. I've definitely done some work before just to find I didn't quite get a plug wire clipped all the way on.
Definitely shouldn't have lost power with that cam.
Up to torque peak it looks like performance is as expected. Just above the hp/tq cross is very suspicious.
You are right it’s definitely a good idea. I will go over everything I can think of again.
Car seems to run really well though and isn’t setting any trouble codes.
Anything in particular you think it could be. Other than something like a plug wire or poor connection somewhere.
Running out of ideas on this thing.
Definetly though compared to the curve in the graph you posted something seems wrong.
It definitely seems to flat line.
Last edited by Rustyoldbird; 07-25-2023 at 02:36 PM.
Sorry, added some info. Basically if this is still a 5.7, 400hp through the tires isn't bad. The difference between a hub dyno and a tire roller dyno can be as much as 20%.
So checked cranking compression on all cylinders. About 180-185 on them all.
For some reason the operator logged time in seconds instead of RPM. That's why they don't appear to cross @ "5252" as they would if it were RPM on x-axis. Not sure why they'd do it that way.
Yeah I really can’t see how that is a useful metric.
That dyno sheets looks rough...its also in STD correction which will give you higher number than SAE correction which everyone uses. I am assuming they have it based on time because if they change it to RPM the graph will look even worse. They can change it to RPM by just clicking on it and changing it, same with SAE correction,
That dyno sheets looks rough...its also in STD correction which will give you higher number than SAE correction which everyone uses. I am assuming they have it based on time because if they change it to RPM the graph will look even worse. They can change it to RPM by just clicking on it and changing it, same with SAE correction,
Yeah the more I dig into this the less happy I am.
07-22-2023, 01:16 PM
Low numbers and low peak torque RPM 
