L-46 Dyno Runs Part 3

[Mike F.]

Here's the previous thread. https://www.forums.ncrs.org/showthre...highlight=dyno

Ran the car on the dynojet today. The numbers were a bit disappointing.

The engine dyno lab results were accomplished with a velocity stack and open headers. The dynojet runs were accomplished with air cleaner installed (except where noted), stock exhaust manifolds and 2 1/2" exhaust pipes through mufflers. (Same as I drive it on the street.) Timing was set at 12' initial and is 35' at 2500rpm.

Engine Lab dyno results .................................................. .......Dynojet results
Before - 285hp @ 4900rpm / 336tq @ 3400 / Comp 8.7:1...........Before - 212hp / 275tq This equates to a 25% total loss for HP.
After - 341hp @ 5600rpm / 387tq @ 3400 / Comp 10.4:1............After - 231hp / 297tq This equates to a 32% total loss for HP.

This graph shows the old engine's best run with air cleaner installed.



This graph shows todays runs 5 - 10. The dyno had a glitch on run 5, so it was aborted. Run 10 was accomplished with the air cleaner removed and shows a burble in the 2300rpm range. (I did not try to duplicate, the engine was making as much as it was going to make.) Runs 6 -9 are the clean runs with air cleaner installed. Run 8 producing the most power.


This graph shows old vs. new with the air cleaner removed.

[Larry B.]

Re: L-46 Dyno Runs Part 3

You raised the compression but what cam is in the motor and is it degreeed to where it is suppose to be most of the time the markes don't make it right.Horsepower is in the camshaft.

[Mike F.]

Re: L-46 Dyno Runs Part 3

You raised the compression but what cam is in the motor and is it degreeed to where it is suppose to be most of the time the markes don't make it right.Horsepower is in the camshaft.

My first sentence with the hyperlink discusses the cam.

I guess I could have been more clear as to why the disappointment. The engine lab dyno runs were fine and as expected. I was a bit disappointed with the dynojet runs. My math supplied an expected RWHP of mid 250's. (341HP x .75 (25% loss) = 255.75 or 341hp x .89 (sae net) x .85 (drive train loss) = 257.96)

The 32% loss that I saw only leaves me guessing. One theory (or grasping at straws) is that my stock OE exhaust manifolds and 2 1/2 exhaust pipes volumetric efficiency was perfect for the old 285hp engine. The air goes in, the air goes out, perfectly balanced.
With the new 341hp engine able to flow more air in, perhaps the OE type exhaust can't flow more air out giving me the higher percentage of loss (32%). Again, just a guess.

This graph shows the best old vs. new engine with air cleaner installed.

[Ken A.]

Re: L-46 Dyno Runs Part 3

Timing needs to be 38 degrees & all in by 3000RPM. That should pickup a few ponies.