Drivetrain Power Loss -- Too much!

[seattle67]

Hi All,

I finally finished my 67 Camaro pro touring project and recently went through a few tuning sessions on a Mustang chasis dyno. I had the motor dynoed after assembly (modified zz502 w/ Edelbrock ProFlo RPM EFI) and came out with 598 HP @ 5500 and 604 ft/lbs @ 5000 at the crank. My best Mustang chasis dyno HP numbers were in the mid 430's at the wheels .. that's 27-29% powertrain loss (ugh!!)

FYI, I'm running a Tremec TKO600 (5 spd OD) and a DSE narrowed Ford 9" (Moser 31 spline axles with a Detroit True Trac posi), headers with 2 1/8" primaries flowing into dual 3" Spintech exhaust. With this combination, I do NOT believe that I should be losing this much power, but I do understand that things like ambient air temp can account for approx. 30 wheel hp or so, but that doesn't explain the delta.

Has anyone run into simlar hp/tq loss with any of these powertrain components?

[Steve Chryssos]

Agreed. That sounds like a big drop. Dyno'd a 400 small block recently.
575HP on W2W's engine dyno, then 460 rear wheel on a Dynojet. That's 20% with a 4L80E and a very restrictive (had to be super quiet) 2.5" exhaust. And 4L80E's have a reputation for high parasitic loss. That reputation is unfounded, obviously. It's all in the converter. But I'd like to see 15% for your stick application. So 500 to 510 rear wheel. That is if your engine dyno runs were made with all accessories in place and your headers--not dyno headers. Otherwise, there might easily be 30HP hiding in your accessories and another 40 in your exhaust and tune. Your 598 ain't 598.

If the engine dyno numbers are net, then the easiest test is to make another run uncorked. If you find the lost power hiding in your exhaust, then re-connect and start playing with your fuel injection map. Hopefully, the Edelbrock system can be fine tuned to regain some of the lost power.

Good luck

[seattle67]

Now that you mention it, the engine dyno did not have accessories on the motor. An electric water pump was used and cooler air from outside was piped in through the ceiling. The dyno headers and exhaust were very comperable to what I'm running in the car today, so I shouldn't be losing much more on the street due to exhaust. If the difference in ambient intake air temp combined with accessory drag (running a vintage air frontrunner serpentine setup complete w/ ac, power steering and hydraboost) accounts for the perceived 60-70 hp difference, I think we have the "smoking gun" vs. the rest of my powertrain.... but I'm still a lil' uneasy about the numbers..

[Steve Chryssos]

Yeah, it's a bummer. Any unusual dips or baubles in the chassis dyno curve? Does the peak to drop off prematurely. It's a lot harder for an engine to pick up momentum when there's a car and earth attached. Water brakes are more forgiving. Compare engine to chassis dyno graphs. You can learn a lot. From there, I guess it all depends on just how uneasy you are. If the answer is VERY--then you need to spend time with the software and money on the chassis dyno. Could find another 30-40 horsepower. We just spent both (time and money) with Jobe at Turbo People. It's amazing what the right person and a laptop can do.

[Jr]

Keep in mind that a mustang dyno will give you lower HP & TQ numbers when compared to other chassis dynamometers. I spend lots of time reading the forced induction section on ls1tech, and well known tuners confirm that the mustang dyno gives lower HP and TQ numbers. For example:Bob at EPP tunes everything on the in-house mustang dyno.
Hope this helps...You have a nice camaro.

[seattle67]

The chassis dyno torque curve was quite a bit different from the engine dyno. My best run after a little more tuning was 441 hp @ 5000 rpm and 499 ft/lbs at 3500 rpm with torque coming on much later at ~3000 rpm vs. 2200 rpm on the engine dyno.

Regardless, I have heard that Mustang chassis dynos tend to understate HP/TQ (ie: vs. Dynojet), but have only heard anecdotal accounts of this vs. actual average HP differences. Big numbers are cool to throw out there when someone asks, but my biggest concern is that I'm not optimizing what I have in the car. It seems that the numbers add up enough for me to be comfortable with the tune/powertrain efficiency, so I'll focus on getting the car out on the road and enjoying it!

Here's a link to video of one of the dyno runs for your entertainment:

https://www.youtube.com/watch?v=7GPdxKZFw0w

Thanks guys!

-Todd