blown 87

Take a stock 87 with a x pipe and tuning, with a 2.20 auto, which will have the fastest top speed, the same car with the 2.20 auto or with a G28/10 2.73?

Lizard928

Given they both have unlimited distance to achieve, and its the same car just with a swapped transmission, with the same humidity, density, etc. they should be able to achieve the exact same speed.

andy-gts

now if you take the 2.73 auto from the factory and swap into the 2.20 then top speed would be different. but if the gearing were the same of the tranny seperate from the ring and pinion then the 2.2 would have the fastest top speed.

blown 87

I would think that the 2.20 geared car would run out of power before it could run out of RPM in 4th gear, but not so with the 2.73 manual car, and that the manual would actually have a faster top speed, even with the higher gear.

I would not think they would be the same at all, even with the same rear end gear due to power losses in the automatic.

blown 87

In your car, yes, you have the power to pull a 2.20 gear, I doubt a near stock 87 like mine would.

Lizard928

The manual will always be faster.
But the auto to auto, or manual to manual they should be the same, or damn close!

jorj7

From my experience with a 2.54 vs 2.20 auto, with stockish horsepower, the 2.54 will have a 3-5+ mph
higher top speed. When you get more power (say 450+rwhp), then the 2.20 can go faster (depending on
the hp to rpm curve). The main reason I go with a 2.20 is that 200 mph is at 5,700 rpm vs 6,500+ rpm
with 26" diameter tires, thus less chance of blowing up the motor from oil issues...

blown 87

If had Andy's engine that would go to the rev limiter with a 2.20 gear it would go a lot faster than at the rev limiter with a 2.73 gear.
since I do not have that much power, I wonder which would be faster.

rear end ratio has a lot to do with top speeds if you have enough power.

blown 87

That is kind of what I thought, that even with a higher gear it would be faster with stockish power due to the 2.20 being to low.

killav

With forced induction, and 2.20 gears, and 1" taller tires than stock, I can vouch that it will travel much faster than the driver (me) is willing to go on public roads.

And you are right Greg, with this combination (before I added FI), it would take a looooong time to build speed when shifting into 1:1, felt like I would have needed 5 miles to get to top speed.

FredR

My late 90 S4 with Louie X pipe [no ST at that time] with its 2.54 gearing invariably ran out of steam before it could get to max power rpms. The taller gearing of the 2.2 box would simply fare worse. To make that work you need more than a stockish S4 is able to offer- hence why folks like George run the 2.2 because he has a sh*thouse full of power to drive it. So would Andy's new stroker motor.

The 2.75 is only available on manuals [correct?] so presumably there is a bit more available at the rear wheels as well. On top end, stock motor, I would say no contest. Thus why hot GT's can and do rev out in top gear- that and the hotter cams of course.

The stock S4 auto will struggle in 4th gear by comparison but in all fairness I have never been able to test this in 15C temps. When rwhp equals air resistance no more go- plain a simple. The S4 auto does high speed cruising very well but it takes a long distance to max out. I have long opined that a 2.75 final ratio would be far superior for warp drive missions. Thus 2.64 and worse, 2.2 will kill a stock S4 off- just loses the sporty feel and leaves it feeling way less than a "super car".

With a slight downhil incline and what I suspect was a bit of a tail wind I did once manage to see x87 kph on the clock but the ambient was still about 30C at the time so I would have been down about 5% or 15 bhp compared to standard [rated] conditions but that was exceptional.

Regards

Fred

blown 87

I have zero desire to find out how fast a stock one will go, much less in the beast you have built.

I do have a local cop buddie who has offered to find out how fast mine will go for me, must be nice to have a get out of jail free card.

hacker-pschorr

Speaking of cop buddies........

Our DOT has been building round-a-bouts like crazy the last couple of years. Recently a rather large one not far from my house. I asked one of my cop friends if he would like to do some skid pad testing with his car chasing me around it.

I'm pretty sure the look on his face was debating between using his gun or tazer on me.

justaguy

Stock 87 5spd with 2:20 will red line in 4th gear no problem( I think its around 140 MPH). I don't know about 5th never had the ***** to try it. That would take a lot of open road and maybe slightly illegal. I have seen 160 MPH, which was pretty close to the limit for both car and driver, Car had more to give, but the driver had reached the fear of death and or Jail speed limiter.

justaguy

Thats stock with Rmb, X- pipe and cat delete plus upgraded suspension. I meant stock versus gutted race car and cagged race car.