thanks nick i know its got more in it especially if i get better than a mail order tune i have seen a guy at the local track pick up 17rwhp going and getting a dyno tune.anyways are u adding any mods to hit 11s or hoping just for some good weather cause i know ur car has 11s all over it.our cars both trapped 87 through the 1/8 wonder how come u trapped 3mph more i swear its in the tune or is that to much for a tune.

 

But 3.73's to 4.10's isn't a huge difference. I still think the engine head design may have played a small role. Not much mind you but coupled with the slight gear advantage might account for this result.

We'll just have to agree to disagree

 

Torque convertor slip is a main thing, especially with an A4 from a roll. That and the key "power under the curve" makes a big difference. If the M6 could hook better off the line, he might run a 12.0 @ 113. The old more hook less mph isn't always true. My car ran 12.5 @ 112 on motor and 12.2 @ 117 on a 150 shot. Does that mean that it is only making enough power to run 117? No, its only getting the enough power to the ground to run 117. I was spinning through second and most of third. The 12.5 was a 1.9 short time while the 12.2 was a 2.2.

 

the +3mph is prolly from the tune since I am also trapping +2mph in the 1/8th.
I am replacing my posi and am going to run some ET Streets and skinnies up front. Hopefully that puts me around 11.8-11.9

 

id say one of 2 things, probably the ls1 has traction problems, and probably the a4 has a stall

and possibly rection time...

when i race w/ my buddy in his camaro, whoever hits the gas first wins... from a roll or from stop,

Tracks figure this in so it makes times look decent

 

Get a manual lock up for that converter. I just emailed Edge and they sayd you can lock that converter up at any rpm in any gear (though i think 1st it wont let you) in applications from 550-600hp. They have an upgraded clutch for it. That will give you atleast 20rwhp and help with your top end. It will also make your shifts insanely hard. Locking up the converter will make your car like an M6. With the stock wiring your converter will only lock up at certain speeds and under like 40% throttle. I know you dont race under 40% throttle so the lock up feature is only for gas mileage on your car. With an Edge converter you can lock that up and transfer all of the power to the ground once you launch and are in your power band.

 

You both trap the same, so I would imagine that in a race from a roll you would be within a car length or so of each other every time. Maybe one day you'll win and the next day conditions will be different and he'll win. There's nothing wrong with either of your cars. For the record my car ran a 13.1@115 MPH, which means it would be nasty from a roll but due to lack of traction a standing start is a joke. You're definately putting the power down better than the LS1, but as stated previously in this thread, going from a roll takes away your advantage. There are so many variable that affect a street race it's not even funny. I think it's pretty silly to debate every "what-if", but that's just me.

 

Where were your and his peak HP & TQ rpm wise?? I bet his was alot higher in RPMs which gives him a much longer powerband which equals more top end. LT1s are known for the low end torque and the LS1s were known for virtually any higher RPM performance. If he is slower in the 1/4 mile but faster or equal in the MPH at the traps he has more top end than you. The difference in 1/4 mile times is due to him being a T56 and either: 1. Having traction problems, or 2. Not knowing how to launch or easy launching. I fully agree with the old statement "you run what you run" BUT that can vary between drivers. Bottom line is that he will always get you if you run from a roll or for more than a 1/4 mile.

 

The difference is due to the gearing.

 

The m6 has less parasitic loss then your A4, so on 2 cars making the exact same power, one with an a4 one with an m6, the M6 is gunna win from a roll.

An a4 will usually win from a stop, because they launch much better.

BUT there are drivers out there who are great at driving manuals and could beat an auto from a stop due to less drivetrain loss again...

 

Parasitic loss in the drivetrain doesn't matter, he said that the cars made similar horsepower at the rear wheels.

You dyno a manual in 4th because in the trans that's a 1:1 ratio.

You dyno an auto in 3rd because in the trans that's a 1:1 ratio.

The manual has closer spaced gears to keep the car in it's powerband better. Hence why gearing is the reason for these cars with similar rwhp figures accelerating differently from a roll on.

I had a similar experience- I had homeported heads, HOTcam, bolt ons, 2800 stall and a tune on my LT1, and raced a guy with an LS1 Trans Am with all the bolt ons and his cutout open. We raced from about 60 on up. He jumped a carlength on me immediately, but past 120 I was pulling up on him noticeably. Up top where I was winding the gears out I had the power to accelerate faster.