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reclaiming parasitic loss


AZGhost623

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how much parasitic loss can be expected from engine dyno to car dyno? Is there a norm?

 

20% 25%? 27% 30% ?

 

I read somewhere TonyD stated just changing out the rear axles to the Porsche CV's you gain quite a bit back (I dont remember what he claimed but it was a solid x% every time). What else can be done to reclaim some of that parasitic loss from the drive train? 

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how much parasitic loss can be expected from engine dyno to car dyno? Is there a norm?

 

20% 25%? 27% 30% ?

 

5-40%, give or take a few. ;)

 

We've had an FC RX7 dyno at our shop to be classified in a NASA class. He originally put down 175whp on a roller. Then he went to another dyno shop (Dynapack) to get tuned and put down ~155whp. Finally, he went to our shop (Dynapack) for NASA classification and put down 127whp. That's a 25% difference in power between chassis dynos!

 

Good luck getting a "crank" number from a chassis dyno, it's futile.

 

As to limiting parasitic losses, that's the name of the game in racing. We've had race teams on our dyno, testing power gains based on what oil they use...

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Everything you can do will almost always reduce component lifetime.

 

Narrower gears, narrower bearings, lighter fluids, lighter components for reduction of transient response issues (moi)...

 

Keep in mind Group 4 Daysuns racing at LeMans and elsewhere in FIA races almost always had the homologated CV Jointed Axles. Far more durable, and less losses to boot!

Edited by Tony D
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Supposedly the tripod style 280ZXT CVs take less effort to articulate than the Porsche or Z31T style with 6 big ball bearings. But anything you can do to reduce or remove the knuckling of a U-joint, especially one that is run at an extreme angle is a good thing. Wolfcreekracing.com says 2-3% more power with their Porsche CV upgrade, but I think that was measured on 510s and they have much worse u-joint angles than Z's  as a result of the semi-trailing arm setup, especially on really lowered cars.

 

Another thing that you can do that doesn't hurt longevity is REM the gears in the trans or diff. I honestly don't know what kind of gains you'd get from it, but gears are supposed to run cooler afterwards as well: http://www.remchem.com/services/. I've seen a ring and pinion set after this treatment was done, and they really do have a mirror finish as it says in the video with the horrible electronic beat music on the site.

 

Just looking at your signature, it doesn't seem like your car is built for a particular class, so the best way to get more power to the wheels might be to just get a more powerful motor. You could up compression, go turbo, V8, etc.

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Well I had my car dyno'd to have it properly set up the other day since getting the Rebello engine back from Dave. His dyno showed 297 with his intake, carbs, and ignition system. All day dyno yesterday on dynapacks ended the day with 214. A bit lower than I expected, about 27% loss. I get what Leon is saying, that no two dynos are the same, but I figured they should be somewhat close in regards to what they do... I just didnt expect that high of loss.

 

As far as racing goes, I do plan to do the HPDE class next month with NASA when they start back up. But that will be as far as I go. Dont plan on changing engines, very happy with the L28 in this car otherwise.

Edited by AZGhost623
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Rebello engine dyno numbers tend to be on the high side.  Other are on the low side.  My Sunbelt race engine from 2001 made 325hp on Sunbelt's engine dyno and anywhere from 265 to 294 hp on various chassis dynos - with no changes to the EMS, ignition or fuel maps, fuel quality, etc.

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Sure, but you still have drive train loss... I just didnt expect 27%ish... which leads me to believe that it wasnt 297 to begin with, but more like 260 or something at the flywheel. Ive been told 20% is a good number to go by which would put it in the neighborhood of 256ish at the flywheel from my dyno. 

 

Like I said, overall Im very happy with this engine, love the sound it makes, I get lots of smiles per mile in this thing. Reclaiming some of that parasitic loss would be where I start next. Ill start off with the CV axles and see where I end up.

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Again, YOU CANNOT EXTRAPOLATE ENGINE HORSEPOWER FROM CHASSIS DYNO NUMBERS!  Period.  End of sentence.  My example above was done to show you that.  The same engine that consistently and repeatedly made 325 hp on a SAE and SCCA Pro Racing tested and certified engine dyno was all over the frickin' map on chassis dynos.

 

Anyone who tells you 20% drivetrain loss "is a good number to go with" is ignorant.

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Got it.... apologies...

 

this kinda got off topic with all the HP talk... I guess the road and track will be the best course of determination on where I lay with HP. As far as reclaiming parasitic loss, the CV axle replacement seems to be the best bet so far. 

Edited by AZGhost623
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Your numbers roughly track with mine. Heck if I was selling engines I'd want my dyno on my side too.

 

Dynos measure Torque and RPM and then multiply those numbers and divide by 5250 to obtain HP figure. (Surprised how many people don't believe this. Try the math on your chart .. :). But then a weather and other correction factors attempt to standardize output to some constant reference temperature and pressure so that in theory your engine in a Colorado summer reads the same as a Seattle winter. There is way too much variable at the weather station for consistency.

 

Daves new dyno is in a nice room and looks great. More importantly he can test engines back to back on his own baseline and measure his product.

 

Did you have filters on? Those were about 7hp for me.

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You said it was dynoed with 'his intake, exhaust, ignition'-so how does that compare to yours?

I'm quite sure his tuning skills are very good compared to the majority. Are you assuming your tuning skills are as good as his. Too many variables to just point the finger at driveline loss.

I will admit that I would be kind of disappointed with your numbers since I was handed a 300hp motor. I'm not buying 27% driveline loss though.

What kind of torque numbers? 

Edited by madkaw
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Did you have filters on? Those were about 7hp for me.

 

Yeah, I took the filters off. I plan on getting those mesh ones you have to not restrict airflow. Between my new tires, flares, and dyno time, Im capped out for the year, so Ill get those next year to make sure they are protected.

 

 

You said it was dynoed with 'his intake, exhaust, ignition'-so how does that compare to yours?

I'm quite sure his tuning skills are very good compared to the majority. Are you assuming your tuning skills are as good as his. Too many variables to just point the finger at driveline loss.

I will admit that I would be kind of disappointed with your numbers since I was handed a 300hp motor. I'm not buying 27% driveline loss though.

What kind of torque numbers? 

 

Here is the chassis dyno sheet from the other day. They use dynapack which bolts to the rear hubs, its not a roller setup.

http://i.imgur.com/vqmYpfw.jpg

 

According to the sheet from Rebello, it was standard ignition with DCOE 45's, 1 5/8's Pace Setter headers. Not sure on his intake manifold, but I run a Kameari intake manifold. My ignition is a CAS setup with Electromotive and the DCOE 45's and the MSA 6-2-1 headers 2.5". I also have a 10lb flywheel.

 

Rebello had peak torque at 5200 rpm with 264.5. My peak torque is 195 @ 5398 rpm. My build is documented elsewhere here with him, but it was 2500$ worth of headwork, his 63DI cam, and about 3000$ of block work with cast pistons and the 240z rods. Maybe the tunning shop left a brake on I dunno LOL... but like Duragg said, its on par with 'loss' on his setup...

Edited by AZGhost623
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I don't know about you...but a 70ft-lb loss is something to be concerned about. If I had paid 3000$ for a cast-piston bottom end, and then 2500$ for a cylinder head that dynoed 70ft-lbs more at the builder than at my local tuner, I'd definitely be looking at the tuner and asking where the other 70ft-lbs went.

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I don't know about you...but a 70ft-lb loss is something to be concerned about. If I had paid 3000$ for a cast-piston bottom end, and then 2500$ for a cylinder head that dynoed 70ft-lbs more at the builder than at my local tuner, I'd definitely be looking at the tuner and asking where the other 70ft-lbs went.

 

I agree... I just figured it was parasitic loss in the drive train.... hence the question...

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I don't know about you...but a 70ft-lb loss is something to be concerned about. If I had paid 3000$ for a cast-piston bottom end, and then 2500$ for a cylinder head that dynoed 70ft-lbs more at the builder than at my local tuner, I'd definitely be looking at the tuner and asking where the other 70ft-lbs went.

 

Is it STILL not understood that the engine was tested first on some sort of engine dyno and then tested again on some sort of chassis dyno? How do you know that the actual loss is 70ft-lb? Neither of the two dynos are calibrated to any sort of standard as far as I'm aware. 

 

We're also throwing in different setups between the car being on Rebello's dyno and now? This entire thread is a complete non sequitur as far as making any sort of worthwhile comparison between dyno results. 

 

:beatdeadh

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Ghost, your set up - engine, tranny, diff, axles etc etc - are unique to your own Hp/Torque pulls on your specific dyno. From my experience using tuning shops, you need to at least minimize the variances, that is, always use the SAME shop during similar weather conditions. Set your baseline then work from there. I've seen incremental changes on the same dyno from upgrades (do one upgrade at a time, i.e. air filter, so you can log the improvements/degradations) and that is the best measurement you can get. See how that translates on the track. For example, I've seen 1 sec improvement on my 2.7 mile Auto Club Speedway from 25 hp tune bump at the dyno, which is a good result, leaving all susp settings, tire pressures, etc. the same. 

 

Note at what calibrations your shop's dyno is set to - flywheel or wheel torque, hub or roller?

 

Parasitic losses, what about all fluids, wheel bearing tightness, axles like those mentioned above, alignment, even tire pressures?

 

Good luck man, I have just started my baselines on my Z for tracking, looking forward to 2015.

Edited by aongch
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