Would you see a difference in performance in an automatic?

[Marcus-SanDiego]

The number I always hear is 15% loss for manual and 20% for auto. Of course, those are just general numbers.

[Jon D]

But in answer to the basic question can you feel the difference with mods. Simply put yes. From a guy with an auto and debTing about a few more performance mods. Headers next on planning list.

[az3579]

Kristen, I believe that automatics experience more parasitic loss than manuals -- whether it's a BMW or a Honda.

Can one of the physics gurus jump in and explain why autos do experience more loss, though? I'm interested.

This. I can't explain why, either, just confirming.

I would think that the auto trans has more HP loss because they generally have more mass than a MT. More mass requires more energy to move.

Some auto techie needs to give us the 411 on this.

I don't think it's due to mass. Perhaps more to the way it operates with a torque converter and all that. I could have sworn that the TC had something to do with some of the loss.

The only way I see an auto being slower than a manual is at launch, because you can't get a proper launch with an auto. But, once it's revved up, it doesn't really matter that much, and depending on how good the auto is and how bad the manual driver is, it could potentially even shift faster. This is more dependant on driver skill though. The manual in the hands of a skilled driver, would allow for a more effective launch, and that alone may make the difference on whether a drag race is won or lost.

In the end, it doesn't matter which you have, because as everyone else said, you will see performance gains regardless of what transmission you have, so don't be discouraged by which tranny you currently have as every mod that applies to the manual applies to the auto as well, with the exception of the CDV delete!

[Crickett]

Automatic transmission systems use a torque converter to control gear ratios as the car increases or decreases in speed. The automatic gearbox uses a system of hydraulic controls that take the energy put out by the engine and monitor it, shifting gears accordingly. While most of the engine's energy is still used to do the same work as a manual system, it goes through an additional step which consumes some energy, albeit only a small amount. The torque converter will always use some power to do its job, no matter its efficiency.

Read more: Why Do Automatic Transmission Cars Get Less Gas Mileage Than Standard Transmissions? | eHow.com http://www.ehow.com/how-does_5801553...#ixzz1L1NgjxRj

Just a better way than I would phrase it

I would think that the auto trans has more HP loss because they generally have more mass than a MT. More mass requires more energy to move.

Some auto techie needs to give us the 411 on this.

These guys have the two major factors in an auto's loss: more mass & the torque converter. The additional mass isn't a huge factor, but probably the second largest factor behind the TC.

As I understand it, an auto's TC can never transmit 100% of the engine's input power like a manual's mechanical clutch can: the fluid coupling will always have some small amount of "slip". That should be where you get a ~5% loss compared to an equivalent manual.

[95m3ltw]

As I understand it, an auto's TC can never transmit 100% of the engine's input power like a manual's mechanical clutch can: the fluid coupling will always have some small amount of "slip". That should be where you get a ~5% loss compared to an equivalent manual.

Actually that is the case with older automatics. The E46 automatic has a lockup torque converter which will lock 100% in 3-5th gears, not sure at what rpm though. The issue of where a automatic loses compared to manual is the amount of slipping at start vs a good drive in a manual, slippage when shifting gears as not to be abrupt and gear ratios.

[nike001]

With all this auto/manual talk..how many of you MT guys can actually catch 2nd? I never really try to, but I noticed i barely can. I'll do a little peep and thats about it. It seems to pop ahead when I engage 2nd, peeps, then slows down..then starts accelerating again.. hmm (yes DSC is off momentarily)

[ZSP-Mafia]

With all this auto/manual talk..how many of you MT guys can actually catch 2nd? I never really try to, but I noticed i barely can. I'll do a little peep and thats about it. It seems to pop ahead when I engage 2nd, peeps, then slows down..then starts accelerating again.. hmm (yes DSC is off momentarily)

With the 3.38 diff, I can get the whole ass-end to kick out when I shift into second.

[nike001]

With the 3.38 diff, I can get the whole ass-end to kick out when I shift into second.

new addition to mod list
>>3.38 diff

[ZSP-Mafia]

The only downside is not having a 6th gear, but that's a moot point for you.

Took this about a year ago. Car actually pulls much harder now.

http://www.youtube.com/watch?v=3DqdMBulurs&feature=youtube_gdata_player

[az3579]

With all this auto/manual talk..how many of you MT guys can actually catch 2nd? I never really try to, but I noticed i barely can. I'll do a little peep and thats about it. It seems to pop ahead when I engage 2nd, peeps, then slows down..then starts accelerating again.. hmm (yes DSC is off momentarily)

You can catch 2nd perfectly if you rev match. Accelerate to the desired shifting point, then let off the throttle, in goes the clutch pedal, wait for the revs to drop to where they should be (probably will be a good second before it falls enough), into second and dump the clutch. If done correctly, you will experience absolutely zero judder, very easy 2nd gear engagement, and it will be a seamless shift.

You can either rev match and have a perfect, judder-free 2nd gear shift (even under full throttle acceleration), or you can quickly but not violently shift into 2nd. It may seem to bog a little bit, but it's still faster than rev-matching it. I only use this method if I have to accelerate VERY rapidly onto the Parkway (some of the onramps have a stop sign at the top!) or if I feel like embarrassing the guy who pulled into the wrong lane next to me at a stop light with the intention of cutting me off (I rarely do this though).