Drivetrain Loss: Understanding it, and Improving it?

MyEarsHurt · Oct 2, 2004

I understand the basic concept of drivetrain loss, power transferred over a certain distance means you have less power at the wheels, fine. Now I have a few questions that I have never really seen clear answers to.

1. I have heard that the "average" drivetrain loss is something like 18-20%, any truth to that with my stang, or any other stang for that reason?

2. What can you do to decrease that percentage? Will buying a lightweight flyywheel, gearset, driveshaft, etc decrease that percentage at all? If so, how much?

Last question that I can think of right now on this topic, assume an 18% drivetrain loss on my car. Lets say that I dyno at 200 rwhp (just to keep the numbers simple). If I go out and buy a lightweight gear set, aluminum driveshaft all that stuff, and then go back to the dyno, are my numbers going to change? Or am I still gonna see 200 rwhp? Do these lightweight parts reflect performance on the street only, not the dyno, or both?

Thanks in advance for the input, I just wanted to clear this up cause I have been scratching my head over it recently...

MyEarsHurt · Oct 2, 2004

come on now, someone has to know this....

jstreet0204 · Oct 2, 2004

Yes, you should see a slight increase. Other components would help also like lighter wheels and brakes. Also reducing friction with sythetic oils in the tranny and rear end.

MyEarsHurt · Oct 2, 2004

jstreet0204 said:
Yes, you should see a slight increase. Other components would help also like lighter wheels and brakes. Also reducing friction with sythetic oils in the tranny and rear end.

So If I go get dynoed prior to those mods, and then go do those mods, then my rwhp will actually improve? If so, im placing the order for my aluminum driveshaft tonight...

jstreet0204 · Oct 2, 2004

MyEarsHurt said:
So If I go get dynoed prior to those mods, and then go do those mods, then my rwhp will actually improve? If so, im placing the order for my aluminum driveshaft tonight...

I wouldn't expect too much from just the ds, but little things add up.

NiteRydaGT · Oct 2, 2004

Average drivetrain loss for a auto is 18%ish, for a stick its 15%ish. I am going to disagree with seeing a increase of HP on a dyno. The items listed...aluminum driveshaft, gears, and lightweight flywheel aren't really HP gaining parts. They will help you transfer the power to the wheels quicker and more efficiently. A torque converter will also help eliminate some parasitic HP loss.

JonJon · Oct 2, 2004

SR 97 GT said:
Average drivetrain loss for a auto is 18%ish, for a stick its 15%ish. I am going to disagree with seeing a increase of HP on a dyno. The items listed...aluminum driveshaft, gears, and lightweight flywheel aren't really HP gaining parts. They will help you transfer the power to the wheels quicker and more efficiently. A torque converter will also help eliminate some parasitic HP loss.

Isn't 'more efficiently' = less drivetrain loss = more HP?

Though like you said, a d/s and flywheel probably won't show up on a dyno really. Dyno's also have a -%/+% varaiation from run to run

Going from 16" rims to 17" rims (66lbs more overall) was DEFINATELY noticable when I floored it. Rotating mass sucks.

NiteRydaGT · Oct 2, 2004

JonJon said:
Isn't 'more efficiently' = less drivetrain loss = more HP?

Yeah but I have never seen a driveshaft or gears add HP on a dyno. I've always understood it to be a SOTP increase.

hotmustang331 · Oct 2, 2004

You should see about 2HP from the driveshaft, and I believe a little more than that from the flywheel....the best thing to do is to go buy some 15s for the rear...takes away the high speed rating but man does it make a difference.I am thinking of waiting until the S/C goes on before I buy the 10.5 bullitts for the rear, probably would hurt you...oh yea and dont get bigger round breaks, robs power.Really I dont think those mods are really worth the money, JUST for the RWHP...however the aluminum flywheel should be a good buy, the engine will rev much easier, but your take off MAY suffer a tad, while once you get going it will pull through the RPMs faster.

MyEarsHurt · Oct 2, 2004

SR 97 GT said:
Yeah but I have never seen a driveshaft or gears add HP on a dyno. I've always understood it to be a SOTP increase.

See thats what I thought, but at the same time that doesnt make sense...cause if you decrease your drivetrain loss from 18% to 16% then you "should" see at least a few hp....i dont know though, this whole thing is a little confusing to me...

Follow up question, if I ditch my 18's for 16's would I dyno any higher than before, or would I just see a difference on the street.

jstreet0204 · Oct 2, 2004

MyEarsHurt said:
See thats what I thought, but at the same time that doesnt make sense...cause if you decrease your drivetrain loss from 18% to 16% then you "should" see at least a few hp....i dont know though, this whole thing is a little confusing to me...

Follow up question, if I ditch my 18's for 16's would I dyno any higher than before, or would I just see a difference on the street.

you should, but also remember dynos, are not 100% acurate. Throw on some 15 inch welds and I'll bet you'll see a difference

MyEarsHurt · Oct 2, 2004

yeah I dont know, my 18's are HEAVY! I am thinking about going back to the stock 16's and maybe put on a set of nitto drags, cheap mod, and it would probably help me a lot.

HIGDON · Oct 3, 2004

You won't gain HP, you will just be able to see what you had been losing to parasitic loss. Say the car is a 250 FWHP car and it puts 225 to the wheels. Adding the lighter stuff may allow you to see 230 to the wheels but it's still a 250 FWHP car.

MyEarsHurt · Oct 3, 2004

bump, any other opinions?

CaliLifeStyle · Oct 3, 2004

Reducing your cars overall weight will help too. Rear seat delete. Carbon Fiber hood and decklid(yeah I know). Removing spare tire. This won't increase HP but it should help anyway. You can try a underdrive pullies too.

MyEarsHurt · Oct 3, 2004

CaliLifeStyle said:
Reducing your cars overall weight will help too. Rear seat delete. Carbon Fiber hood and decklid(yeah I know). Removing spare tire. This won't increase HP but it should help anyway. You can try a underdrive pullies too.

Rear seat delete = done
spare tire removal =done
CF hood =ordering next month
UD Pullies = done

Granted the 50+ pounds in stereo equipment doesnt help, but come on ya gotta have some nice beats to roll to

crew_dawg16 · Oct 3, 2004

MyEarsHurt said:
Granted the 50+ pounds in stereo equipment doesnt help, but come on ya gotta have some nice beats to roll to

Well, if you lose all that stereo equipment, you could change your name to MyAssHurts

MyEarsHurt · Oct 3, 2004

crew_dawg16 said:
Well, if you lose all that stereo equipment, you could change your name to MyAssHurts

Yeah I could, but where is the fun in that?

Redfire03GT · Oct 4, 2004

MyEarsHurt said:
Yeah I could, but where is the fun in that?

Priorities I suppose.

Although, the weight reduction is nice but, less drivetrain powerloss won't -add- power but it will help to -free- up power. There's a slight but significant difference between the 2.

You should, in theory, see more rwhp by simply having less rotating mass and light weight drivetrain parts. That doesn't mean you all of a sudden added power that wasn't there to begin with, you're just better utilizing your exsisting power.

Also, weight reduction is sometimes in itself hurtful if not done properly. What I mean is, if you do a rear seat delete, remove spare tire, jack, etc. All of that weight is being removed from where? The back end. Is that going to help traction at all? No, it should actually be making traction worse. Sometimes weight redistribution/weight transfer is more effective than simple weight reduction.

Hope that helps.

CdnNavybob · Oct 4, 2004

I don't remeber which Mustang Magazine did it but they made a superlight 5.0 LX and actually added time at the strip due to the loss in traction. They found one guy could actually lift the rear wheels off the ground! They eventually had to add about 100 lbs of dead weight to the rear end to get the thing to hook properly.

Relocate your battery to the trunk, and consider some lightweight front suspension parts i.e. Tubular K-Member, tubular A-arms. I think a coil over front suspension will save a bit of weight too, in addition to improving you handling.

Drivetrain Loss: Understanding it, and Improving it?

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