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!!) :mad:

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.. :_paranoid

[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. :thumbsup:

[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:

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

Thanks guys!

-Todd

[JamesJ]

Was this a crate motor? If so sometimes they (builders) just have a dyno sheet for that type of motor, not the actual one that was built for you. Just a question...

We keep looking at what it is now, maybe the motor dyno was wrong...

[ProdigyCustoms]

No big deal. Two examples.

My street racer makes right at 620HP, on a chassis dyno it makes 414HP. And it runs 10.70s! It runbs 101MPH in the 1/8th and 126 in the 1/4. That is a TH350 and loose converter, so it could be said it is lost there.

On a 300 shot of nitrous, we picked up almost 300HP, made just over 700HP at the tires. It runs low 9s on the nitrous!

Project Prodigy was engine dynoed on a Tuesday at 3PM at 93 degrees and made 684HP. At 3PM on the next Thursday (48 hours later) it was on a chassis dyno, a few degrees cooler temp, it made 446HP. It is a TKO600 car. Two days later it was at Run Thru the Hills and drag racing. It has not run the quarter, and the 1/8th mile times were slower then our street racer due to lack of traction on street tires. Street racer runs 6.80, Prodigy was running 7.40s, all lost in the first half of the track. But Prodigy's MPH was 100MPH in the 1/8, basically the same as my street racer which dead hooks.

Another. We did a 572CI motor that made 758HP, Put it in the car, a 67 Chevelle with a TKO, it made 556HP at the tires. I will have it on the dragstrip at Run Thru the Hills next month. I expect 105MPH trap speeds.

So don't worry about the numbers. We don't race dynos. They are great tuning devices, but I do not put much stock in the big number.

[seattle67]

Was this a crate motor? If so sometimes they (builders) just have a dyno sheet for that type of motor, not the actual one that was built for you. Just a question...

We keep looking at what it is now, maybe the motor dyno was wrong...

Apologies, my last post was inaccurate.... my best chassis dyno numbers were 441 hp @ 5000 rpm and 499 ft/lbs at 3500 rpm. Regarding the motor, we started out with a zz502 crate, but shaved the heads to get 10:1 compression, ported/polished the heads, added Edelbrock ProFlo RPM EFI, polished the intake runners and replaced the valvetrain with upgraded Crane roller valvetrain (more duration/lift, roller rockers, etc.). Dyno session was complete along with engine dyno video/commentary.

[seattle67]

No big deal. Two examples.

My street racer makes right at 620HP, on a chassis dyno it makes 414HP. And it runs 10.70s! It runbs 101MPH in the 1/8th and 126 in the 1/4. That is a TH350 and loose converter, so it could be said it is lost there.

On a 300 shot of nitrous, we picked up almost 300HP, made just over 700HP at the tires. It runs low 9s on the nitrous!

Project Prodigy was engine dynoed on a Tuesday at 3PM at 93 degrees and made 684HP. At 3PM on the next Thursday (48 hours later) it was on a chassis dyno, a few degrees cooler temp, it made 446HP. It is a TKO600 car. Two days later it was at Run Thru the Hills and drag racing. It has not run the quarter, and the 1/8th mile times were slower then our street racer due to lack of traction on street tires. Street racer runs 6.80, Prodigy was running 7.40s, all lost in the first half of the track. But Prodigy's MPH was 100MPH in the 1/8, basically the same as my street racer which dead hooks.

Another. We did a 572CI motor that made 758HP, Put it in the car, a 67 Chevelle with a TKO, it made 556HP at the tires. I will have it on the dragstrip at Run Thru the Hills next month. I expect 105MPH trap speeds.

So don't worry about the numbers. We don't race dynos. They are great tuning devices, but I do not put much stock in the big number.



Thanks for the examples Frank. I was starting to get a little pissed that I spent the extra money to build the motor beyond its stock form. So, how much does your street racer weigh? Your numbers are great, considering the wheel horsepower numbers you made :thumbsup:

Regarding Project Prodigy ... any concerns about TKO600 efficiency?

Thanks!

Todd

[ProdigyCustoms]

The street racer weighs 3450LBS with me in it. As for TKO efficiency, I dont know