Hey y'all,

I have been recently contemplating getting different mods (intake, hfc, exhaust) to increase power on my 08 g35s sedan (AT). While sitting here perusing the forums (normally g35driver but y'all seem more up to date haha) it just came to me why not instead of trying to add 8hp for $400, try to decrease initial drivetrain loss? What would be the first things I would have to change and/or modify in order to loose less power through the torque converter and auto tranny?

I am an amateur when it comes to stuff this technical, and would love some help from the community to figure out how to actually get all 306hp from the engine back to the rear wheels.
And just so you know who you're helping [:


thanks in advance dudes

 

Change out the AT for an MT.

 

I don't think that is possible.
bring it to a professinal tunner & let them handle that part.
you are gonna need a ton of mods, even then g/l cracking 300whp(it took me a while to make 325whp.)
you are gonna have to spend alot more than $400.
on the bright side, at least you can do a full tune.
try tunning a 37.
.

 

I don't think there's any way to significantly reduce drivetrain losses on your car. The biggest losses are in your transmission. Unlike a manual transmission, there's really no direct connection between the engine's crankshaft and an automatic transmission. And you "lose" a bit of power as it goes through the transmission itself.

The rest of the losses are through the driveshaft, u-joints, differential, axle shafts, constant velocity joints and hubs. If there were any way to minimize those losses, I'm sure automobile manufacturers would have done so. If you discover a way to reduce your drivetrain losses, definitely consider getting a patent because you'll probably end up a millionaire!

 

One way to reduce drive-train losses is lighter brake rotor, lighter tire and wheel assembly. Even same tire size from different mfr can vary as much as 3 or 4 lb each.

 

That's not reducing drivetrain losses....that's reducing unsprung weight. Still a good idea though.

 

Less friction in drivetrain components. Less rotational mass of drivetrain components. A lightweight driveshaft and a more efficient transmission. Those aren't very practical suggestions I'm afraid, but they're an example of things that will accomplish your goal.

 

ive actually been wondering about a custom made ligthweight driveshaft. theres a couple of shops in miami that make aftermarket shafts i just havent called anyone and inquired. im assuming our stock driveshafts are steel? what are the disadvantages of going to something else, i.e. aluminum, carbon, alloy, etc (something else i didnt list)

less rotational mass will make a stock car seem so much quicker than if you put intake exhaust. lighter rotors + lighter wheels and tires are a def. improvement.

 

True, but is it really worth it?

The reason they're made from steel is they need to handle all the torque put down by our engines, especially from aggressive launches etc..

 

put in a dct

 

Rotors, wheels and tires are all part of drivetrain loss.

The stock torque converter robs a lot of power from the engine. I think the TC alone is responsible for 6% of the 20-25% drivetrain loss in the 5AT. I don't know if aftermarket TC's will reduce the losses, but if they do, then you'll free up a few whp's.

Tires have quite an effect on rotational mass and drivetrain loss, particularly since the further the mass from the center of it's rotation, the larger the effect is. Therefore, lighter tires can also help free up some whp. Same goes for the center driveshaft, axles, ring and pinion, diff, etc. Ofcourse it's not worth the trouble of swapping drivetrain parts since it can be costly and you can only free up so much whp anyway.

Next time you go shopping for tires, go on tirerack.com and look at the weight of each tire. Pick something lighter than the stock potenza's and you may feel a slight improvement in acceleration. Theoretically it should also help reduce unsprung weight, but it may not be as noticeable.

My 275/35/19 tires in the rear are Hankook K110's and they weight 29lb each according to tirerack. The Continental ExtremeContact DW's weigh 27lb each for the same size. That's 4lb's off simply by switching out the rear tires to another brand with the same size and performance.

 

I think you're confusing drivetrain losses with removing weight (especially unsprung weight) from the drivetrain. Drivetrain losses happen as power is transferred from the crankshaft to the rear wheels. Lowering the weight of a component itself doesn't really reduce the drivetrain loss, although it does net faster acceleration because less energy is wasted rotating a lighter component. Take a lightweight driveshaft for example...it requires less power to rotate a lightweight driveshaft than a regular driveshaft, so the benefit is in the lighter weight itself. But the drivetrain losses that occur in a driveshaft are mostly in the power transfer through the u-joints and/or yoke. I guess you can make the argument that lighter weight lowers drivetrain loss, but I see that more as a weight reduction of rotational mass and not really minimizing the actual losses. Same goes for wheels/tires and brakes, simply because a reduction in unsprung weight is always more effective than the removal of an equal amount of static weight.

Hmmm....I think I confused myself. Anyway, when it comes to drivetrain losses, I don't think there's much we can do to improve the car. But when it comes to weight reduction, I'd say wheels & tires are probably the most cost effective areas to focus on

 

One can also improve acceleration by a shorter tire which is: lighter weight, less un-sprung weight, better gear ratio. But watch out for tire load rating..
MSCA, wheels and tires, brake rotors are part of the drive train. Reducing weight on these component reduces drivetrain losses as it takes more energy of the engine to rotate heavier components. Un-sprung weight is the weight that impacts the suspension movements. So lighter wheels, tires and rotors have double benefits.

 

Wheels are tires are arguably part of the drivetrain....they are at the very end of it. Brake rotors are not part of the drivetrain at all. The drivetrain is what propels the car...the brake rotors help stop it.

Unsprung weight does impact suspension movements, but rotational mass (crankshaft, driveshaft, axle shafts, etc...) should be differentiated from unsprung weight, although a reduction helps in each.

 

A shorter tire may help acceleration, but it will hurt absolute top speed and the top speed in each gear. So there's a cost/benefit by decided to run shorter tires.