most power NA e85 6AT
 

hey everyone just traded my 2001 corvette z06 for a fr-s and chose and the wifey talked me into an AUTO, any who my question is whats the max hp ppl have been seeing with a tune and e85 on an AUTO with and without boltons

170-200 give or take (unless your definition of bolt ons includes a bolt on FI kit. In that case as much as you're willing to push it)

Auto\man does not rearly matter same engine maybe couple more hp loss through auto trans.

see Basic Bolt on mods link below.

Hi, I have a 4.875 FD in my A/T and I would recommend that as your first mod. I disagree with @steve99 about the difference in power. The engines produce the same power, but not to the ground. The M/T has a greater mechanical advantage, in every gear, over the A/T. Even with a 4.875:1 FD I only have the advantage over a M/T in 1st and 2nd gears, see below;

4.88 a/t vs 4.10 m/t

1st@25mph = 5891/5072 a/t
2nd@30mph = 4116/3673 a/t
3rd@60mph = 4412/5174 m/t
4th@60mph = 3996/4072 m/t
5th@60mph = 2849/3357 m/t
6th@60mph = 2326/2575 m/t

Leaving in the 4.10:1 FD is even worse, see below;

4.10 a/t vs 4.10 m/t

1st@25mph = 4949/5072 m/t
2nd@30mph = 3458/3673 m/t
3rd@60mph = 3706/5174 m/t
4th@60mph = 3357/4072 m/t
5th@60mph = 2394/3357 m/t
6th@60mph = 1954/2575 m/t

5th gear in the A/T is still higher than 6th gear in the M/T! The A/T with a 4.88 FD is able to use 6th gear quite easily in the city, as low as 35MPH, offering a bit better city mileage and much more power to the ground. The bottom line is, don't try to race a M/T. A good driver can put down more power to the ground than you can. Which more than makes up for time lost shifting. Also, if you're not going to track the car, replace the stock front sway bar with Cusco's 16mm hollow front sway bar. It's 21% softer than stock, and helps eliminate cross-talk in the front end over large slow-speed bumps, giving a much better ride in the city, especially if the roads suck where you live.

:burnrubber:

@KoolBRZ
Hmmm think you are confusing horsepower and torque

HP = Torque x RPM ÷ 5252

derivation

http://www.epi-eng.com/piston_engine...and_torque.htm


A gearbox or final drive will change the torque and rpm but wont change the power (other than the loss through the driveline)

No, I'm talking about increased Ground Torque. Look it up, it's really a thing. I have better acceleration with my 4.88 FD than I had with my 4.10 FD, and it feels like my car has more power. This is because my engine is turning more RPM's per revolution of the wheels. The engines horsepower hasn't changed, but the Ground Torque has changed because the engine turns more revolutions per wheel revolution giving it the mechanical advantage I'm talking about.

Your talking in circles dude

I give up

You are both right. Changing the gears in the rear differential will not give you more power or torque at the crank. It will increase torque to the wheels. By going to the 4.88 gears from the 4.10 gears, you are essentially changing the lever arm length that the engine torque is applied to. The bigger the lever arm, the more force applied. The cost of that is distance, your engine now has to turn more to cover the same ground, hence the higher rpm at a given speed.

We all gave up, valiant try though.

+1

Auto is fine, it makes the same power at wheels as MT, so just read steve's sticky.

Torque to the ground.

1st Gear - 3.626 M/T, 3.538 A/T
Final Drive - 4.10

3.626 x 4.10 = 14.8666 absolute ratio.
3.538 x 4.10 = 14.5058 absolute ratio.
3.538 x 4.875 = 17.2478 absolute ratio.
What this means is that, for every turn of your wheel, your crank will have turned 14.5058 times in the A/T, 14.8666 times in the M/T. From this, we can calculate the total torque produced to the ground:

Absolute Ratio x Engine Torque = Torque to the Ground

14.8666 x 151ft lbs = 2244.8566ft lbs of torque per revolution of the wheel in the M/T W/4.10 FD.
14.5058 x 151ft lbs = 2190.3758ft lbs of torque per revolution of the wheel in the A/T W/4.10 FD.
17.2478 x 151ft lbs = 2604.4103ft lbs of torque per revolution of the wheel in the A/T W/4.875 FD
Based on formulas presented by user, "mfactory" at the following website.
http://www.ek9.org/index.php?threads...-friend.10883/

Where the rubber meets the road.
 

At 25MPH the stock tire turns 352.0458RPM's. (25MPH/60 * 844.91 Rev's per mile)
Per @steve99's quote, HP = Torque x RPM ÷ 5252, so to figure Horsepower to the ground.....

The A/T has 2190.3758ft lbs of Torque to the Ground in 1st gear w/4.10 FD.
2190.3758ft lbs x 352.0458RPM's divided by 5252 equals 146.8227 Horsepower

The M/T has 2244.8566ft lbs of Torque to the Ground in 1st gear w/4.10 FD.
2244.8566ft lbs x 352.0458RPM's divided by 5252 equals 150.4746 Horsepower

That's 146.8227 Horsepower for the A/T, versus 150.4746 Horsepower for the M/T.
Now let's change the FD of the A/T to 4.875 and leave the M/T at 4.10. That changes it to 174.5757 Horsepower for the A/T, versus 150.4746 Horsepower for the M/T.

This makes changing the FD to 4.875 the most affordable horsepower gain of all! This change is also cumulative with other changes, so if you add 20HP with a header, it would be a true 20HP gain.

:burnrubber:

Only if the peak torque figure you are using from the engine was available at the new rpm required to spin the wheels at that speed. I think some of your assumptions are flawed in thes calculations.

The lower F/D will increase in gear acceleration and will be an overall improvement to acceleration for the auto relative to the manual box as it has wider gear spacing.

The RPM's in 1st gear at 25MPH are 4949 for the 4.10, and 5891 for the 4.875. the torque doesn't really start dropping off till after 6000 RPM. It might be off by as much as 5ft lbs plus or minus. With 4.10's in both A/T and M/T, the M/T has more Ground Torque, or Power-to-the-ground than the A/T in EVERY gear. The A/T is made for mileage and sacrifices power, while the M/T is made for power and sacrifices mileage.