I put my car on a dynapack hub dyno last night, made 7 pulls. The first three were with the muffler off and a turndown on the rear, which melted the asphalt. The last runs were with the stock muffler back on.

Numbers peaked around 224hp and 195ft/lbs

The numbers without the muffler we actually lower all the way around, but not by much.

They had me pulling in 5th, is that the correct gear to make pulls in a 350?

Sorry for the noobness but I am not too familiar with Dynos, and only made 3 pulls before in my Z-28, which they had me pull in 4th.

I was a little disappointed with the results. I may go to the same place I did pulls in the Z-28 and see how the car compares to the results I had there before.

Anyone have any thoughts on why the numbers appear low???? My best 1/4 has been a 14.1, I've only made 5 passes, all improved as i went, I am more into autocross than drags, so I don't know if I'll bother making anymore 1/4 runs or not.

 

Something has to be wrong with that dyno.. the car has 274lbs tq, and you got 195?! Thats over 29% loss.

Something had to be wrong with that dyno!!

 

maybe his 5th gear pull has something to do with it?

 

Should I have pulled in 4th? I honestly don't know

 

dynapack hub dynos usually have way different numbers than dynojet, but I thought they were higher., you should do a search for other dynapack dynos, I know I've seen them before here.

5th gear is the correct gear, that gives a 1:1 drive ratio.

 

Dyno'ing is usually done in the 1:1 gear, lots of A4's this is 3'rd gear, lots of 5 spds it is 4th gear, and in the F-body T56 trans, it is 4th gear since 5th and 6th gear are both over drives.

You can dyno in first gear if you wanted, but the engine would rap out very quickly and you would not get many data points and the dyno would be innacurate.

Remember that the dyno wheel measures the amount of work being done, if you were in 6th gear, the engine RPM would go up slowly, but the dyno wheel would move more quickly. Vice versa with first gear, the RPM's would move up very quickly but the actual work being done is not that high. The dynos measure the amount of work being done over the amount of time it takes to do it and just does some computations for your hp.

I think it's more of a rule of thumb to do the dyno's in it's 1:1 gear because it is a good compromise of engine RPM and time to perform a dyno test. Just think of a auto civic with less than 95 whp doing a pull in over drive, the dyno operator would be asleep before it got to 7k RPM

And yeah, 195 tq seems a little low, although it's not surprising that it was lower with the stock muffler off than with it on.

I'm curious how close to the ground the exhaust dump was? Was it angled or going straight down?

 

The pipe was angled down from the flange where the stock muffler mounts to the pipe. It was 8-12 inches away from the ground.