gmanggg

All these recent 5sp vs auto threads have make me wonder how much power these autos really put to the ground.

Has anyone dyno'd their auto 3rd gen? Post mods and graphs if possible.

Cheers!

gmanggg

Maybe this will help settle the 5p vs manual debate or at least reduce the amount of bs that is constantly flung back and forth!

areXseven

iTrader: (1)

Stock to stock comparison should yield :
Manual: 255hp at 6500rpm
Auto: 255hp at 6200rpm

Sorry, don't have any RWHP figures.

gmanggg

So there's no driveline loss due to the automatic tranny?

areXseven

iTrader: (1)

No driveline hp loss,..just driveline hp lag because of the 3.90 final gear drive. ALTHOUGH, manufacture data does support the Auto FD will reach max HP 300 rpms before it's Manual Tranny'd brother.

jimlab

Absolutely drivetrain horsepower loss. On average, 5% more than a manual car.

areXseven

iTrader: (1)

So about 12-13 HP loss in the Auto FD,(or less), depending on final HP loss to the wheels of the 5-speed FD. Is your figure based on any and all Manual/Auto tranny (same model) vehicles or specific to the FD?

jimlab

The rule of thumb for any vehicle is 15% drivetrain losses for a manual transmission car and 20% for an automatic. Some are more, some are less, but those percentages are fairly accurate. A percentage is used because frictional losses increase as power increases.

speeddemon7

quick question regarding this.I went to rx7 store and they say that running a catback,intake and downpipe is good for roughly 300 rear wheel horsepower.
Which translates to somewhere in the 350 horsepower at the flywheel.
If this is correct for a manual transmission setup and if it is true as far as horsepower levels being accurate with these modifications then a auto rx7 with the same mods should be pushing 280 horsepower at the wheels.Somehow I dont think this is quite accurate.

jimlab

Really? Why do you think the rest of the world would use those percentages if they were inaccurate?

Can you think of another reason why the auto FDs are slower than the manuals? If it were only the weight difference, they should only be 0.1-0.2 seconds behind the manuals, yet they're significantly slower. Compare the performance figures from the Motortrend May '94 test of an auto Touring and the August '93 test of an R1...

0-60: 6.0 seconds
1/4: 14.5 sec. @ 96.3 mph



0-60: 5.3 seconds
1/4: 13.9 sec. @ 99.7 mph

speeddemon7

no jim.I wasnt contesting the whole driveline loss percentage thing.I was asking about the 3 mods in reference to what rx7store says the rear wheel horsepower output is.
Do these three mods really make the 5 speed a 300 rear wheel horsepower vehicle.Because if it does then that means a auto car with the same mods is putting down 280 rear wheel horses.Correct?

areXseven

iTrader: (1)

Thanks. Good info as always. So by those (% of drivetrain loss) figures, a 255hp Manual FD converts about 217rwhp, while the 255hp Auto Fd converts 204rwhp. A difference of 13 hp.

An Auto FD (healthy, of course) would only have to add a DP and/or a good aftermarket open intake to equal or exceed a stock (un-modded engine) Manual FD's rwhp.

Whats really strange is that there's data/stats (from Mazda) that has both manual and auto FD's running equally timed 0-60mph.

Putting everything into perspective, an Auto FD is quite a "dead stop dash to the finish" underdog when compared to it's 5-speed brother;
- 5% additional drop in rwhp (5% more than the 5-speed FD)
- restricted low rpm launch
- 3.90 final rear gear drive

And yet, their a hoot to drive!!

speeddemon7

I wonder which car would beat the other if say you had a 5 speed with the 4.1 gear and an auto with the 4.3 gears.Provided both cars were stock and running the same.

areXseven

iTrader: (1)

Didn't know Mazda made a 5 speed auto. (j/k)

Good question. The Auto would still possess less HP, so the 4.30s would only compress the HP in it's power range, not necessarily making it faster than the 4.1 manual FD.(?)

speeddemon7

You know what I meant about the 5 speed vs the auto
maybe not faster but equal as far as rate of accelaration perhaps? thats what the rear gears change correct? it would make the horsepower available sooner in the powerband right? just a thought.maybe jim can help us on this one.

weaklink

i doubt i still have it, but my car dynoed 250ish to the wheels at rotary performance with a PFC, DP, catback, greddy SMIC, and apex intake. the tranny grenaded about 1 hour after I picked it up.

speeddemon7

now that sucks.sorry to hear about that.

jimlab

Sorry, I thought you were questioning the auto making less power.

I don't believe so. Add a high-flow cat and 12-13 psi and then you've got 300 RWHP, but not with just an intake, cat-back and downpipe at stock boost.

jimlab

Don't forget the weight and gearing disadvantages.

That's news to me. Where did you see this?

That's really what it's all about, isn't it?

jimlab

The gearing change would get the engine into its power range more quickly, and while the gears would be "compressed" (time- and top speed-wise, not power-wise), the gearing would increase torque at the axles in every gear, increasing acceleration.

Basically, you'd have a lower top speed in each gear, but you'd get there more quickly. Whether or not that would be enough to fight off a lighter manual car is another story.

weaklink

no problem! I had it rebuilt. It cost an arm and a leg, so an auto is now my only option! It still didn't hurt as bad as my bruised ego...OUCH!

speeddemon7

whats the weight difference between the 5 speed and the auto? Didnt know there was one.

jimlab

Automatic cars are almost always heavier than the manual version.

Base, M5 - 2,789 lbs.
Base, A4 - 2,857 lbs. (+68 lbs.)
R1/R2, M5 - 2,800 lbs.
Touring/PEP, M5 - 2,862 lbs.
Touring/PEP, A4 - 2,923 lbs. (+61 lbs.)

M5 = 5 speed manual
A4 = 4 speed automatic

speeddemon7

is it the tranny thats heavier or what? seems like a big amount of weight difference between the two.Here I was thinking I had a car that weighed 2780 only to find out it really weight 2925.Bummer
If I swap to a 5 speed do you think ill shed those extra 61 pounds?
also what makes the base models lighter than the touring.which is what I have.
Sunroof? I dont have the bose system anymore.hmm what else? the cruise controll maybe? I never use it so maybe I can get rid of it.it doesnt work anyways.

jimlab

Yep.

Actually, it's not that bad. Not great, but not horrible either.

MKIV Supra
NA, hard top, A4 - 3,265 lbs.
NA, Sport Roof, A4 - 3,325 lbs.*
Turbo, hard top, M6 - 3,445 lbs.
Turbo, Sport Roof, M6 - 3,505 lbs.*
Turbo, Sport Roof, A4 - 3,515 lbs. (+10 lbs.)

*Note that the additional bracing and reinforcing required for the sport "targa" roof added about 60 lbs. to the car over the hard top version.

C5 Corvette
Z06, M6 - 3,117 lbs.
Hardtop, M6 - 3,173 lbs.
Coupe, M6 - 3,210 lbs.
Coupe, A4 - 3,246 lbs. (+36 lbs.)
Convertible, M6 - 3,214 lbs.
Convertible, A4 - 3,248 lbs. (+34 lbs.)

NSX
M6 - 3,153 lbs.
A4 - 3,197 lbs. (+44 lbs.)

More or less.

No leather, fog lights, cruise control, spoilers, sunroof, etc.