Patman

This is something I've always been curious of. How come in 2001 the M6 Corvettes have been rated at 375ft lbs of torque while the A4s are at only 360ft lbs? What mechanical differences account for this? I know it's not driveline losses, as they are both rated at 350hp, plus the torque rating they are giving is at the engine anyways.

Jayzvette

I believe it's the torque converter that eats up some of the torque. Don't quote me on this though <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

66ImpalaLT1

Could it be torque reduction in the pcm programming? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Eric

Patman

I don't think it's the torque converter though, because like I said, that rating in the GM books is all at the engine, not at the wheels. Perhaps it is torque management like Eric suggests. If so, then it could be programmed out quite easily I would imagine!

Norm

This is an interesting topic. If someone does know the answer, please, do tell. I have an A4, and if it can be reprogrammed to give us the extra torque loss, that would be awesome! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ August 16, 2002, 09:25 PM: Message edited by: Norm ]</small>

MDL-01C5

I believe it's nothing more mysterious than parasitic loss through the automatic tranny vs. the comparatively less-complex manual...I do recall hearing that the computer programming does have some effect, though.
Post this in the LS1edit area to see if they've gotten gains there by modifying Tq Management--that might answer your question on that front... <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Patman

I hate to sound like a broken record but I don't believe it's the loss of the drivetrain. If so, the HP number would be lower and also, GM doesn't change the rating of power on other cars between auto and M6. For instance, the LS1 F-body shows the same HP and TQ numbers listed in the book whether it's auto or M6. So it has to be something else.

Old SStroker

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Patman:
<strong>This is something I've always been curious of. How come in 2001 the M6 Corvettes have been rated at 375ft lbs of torque while the A4s are at only 360ft lbs? What mechanical differences account for this? I know it's not driveline losses, as they are both rated at 350hp, plus the torque rating they are giving is at the engine anyways.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You are most correct that it's NOT driveline losses, although A4 has more than M6. OEM rated hp & torque are at the flywheel, not the wheels.

M6 LS1 is a "ZCD" code engine and has 375 lb-ft @ 4400, while A4 LS1 is a "ZCB" code engine and has 360 lb-ft @ a lower 4000 rpm.

The different engine codes indicate different hard parts in the engine. Although I'm still searching for the numbers, I suspect slightly different cams. The ZCB has more low-mid torque while the ZCD has more peak torque. A cam difference easily accomplishes this. With the larger drop in rpm at full throttle shifts, the A4 needs torque at a lower rpm than the M6.

Remember most A4's have the 2.73 gear, so that's what the ZCB is probably tuned for. Would a change to the ZCD cam be a good idea with the 3.15's? Without good torque curve info it would be hard to predict, but it would be a lot of trouble for a slight change. Remember that torque accelerates, and the engine spends more of its time below 5500 than it does above during max acceleration....especially an A4.

Patman

Very excellent info thanks! So then an A4 car would probably pick up more ET with a cam swap than an M6 would?

LS1LT1

iTrader: (16)

I too remember when the '01s came out and reading about the lower torque rating and being quite bummed about it (I'm an A4 guy <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> ) and I also figured it was just PCM/torque management related.
What puzzles me is why the earlier A4s ('97-'00) weren't rated less than the M6s. Maybe because Team Corvette felt that 360lb/ft was the max for the 4L60E when mounted backwards (or otherwise) but at the old rating (350lb/ft) it was ok to have them both the same or something? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
<img border="0" alt="[Corvette]" title="" src="graemlins/corvette.gif" />

LS1LT1

iTrader: (16)

And I was also wondering if those '01 changes also applied to the F-body LS1s (other than the LS6 intake/!EGR of course) as well but just not publicized because how many different alloy LS1/cam combinations can GM really be making?:

C5 6 speed LS1
C5 auto LS1
Z06
Base F-body LS1 (A4 & M6 supposed to be the same, maybe not?)
SS, WS6 & Firehawk (I know that's really just a rating)

And then of course all the iron block LS1 truck motors. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

xtream1

This past week while in Monterey, I spoke with Dave Hill and during a conversation he mentioned that they gave the MN6 more torque than the A4 due to info from surveys on who was mostly buying A4's and what their average use was as opposed to the MN6 crowd. Don't know how they did it though-wether it was cam swap or computer tweaking.

sited12

I always thought it was the bigger gears that made the extra torque.

Old SStroker

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by sited12:
<strong>I always thought it was the bigger gears that made the extra torque.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Gears multiply engine torque (and divide rpm in the process---or vice versa). Engine torque and hp numbers from the manufacturer are at the flywheel before any gearing.

Bad02WS6

1st. Not any of the ls1's I have witnessed. makes the same power as the other.

2nd. A4 and M6 cannot be compared on the dyno.

If you took a Vette with a A4 and put it on the dyno. Then take that same motor and put it into a M6. The LS1 M6 settup would maker higher peak numbers.

Utsu

From what I understand, the A4 wasn't meant to handle the extra torque like th M6. Of course, it can handle it, but GM wants to be "safe" from extra stress since they have to warranty their cars....at least that's what I remember reading about.