c4cruiser

So for the last few years I have been using my '87 coupe for autocross and some track day use. The car has a few mods and is a 4+3. It does fairly well although it could use more power.

I'm thinking about a later C4; a 1993 with a built 383 LT1 and has the Z07 suspension. I've seen this car run and I know pretty much all of the work that has been done to it. I know the owner and I can get it at a good price.

But it's an auto trans car (4L60E) and that makes me want to ask just how good would an A4 work? Most of the events I run are on an old airport runway and typical course lengths are just under 1 mile. I know a few guys that use auto trans cars, but my concern is things like downshifting into 1st when I don't' want it to.

Opinions on an A4 for low-speed (35-75 MPH) autocross??

fleming23

If you have the software, you can manually shift and flash a TCM file that does not allow it to kick down based on throttle position, basically making it like a manual valve body trans. I did this for one track day, but was not autocross.

Solofast

There are a number of limitations that the automatic brings to the table, and a few advantages.

We ran as a BSP car and that limited what we could do with gears. First is ok, but second was way too tall. That is we gave up a lot of acceleration in second because we never got near the 80+ mph that we could do in second. If your classing allows you to put in a shorter final drive ratio that would help a lot. First gear was about the same as a C5 Z, but second was way way taller. But first was also tall enough that the shift to second was sometimes a problem, it would hit in fast mid speed corners and that would break the rear end loose..

With the automatic in BSP we ended up "between gears" a lot. That is, we'd end up low in second and not be able to put down as much power as a stick shift car in second. LIke I said, if you can run a 4:11 gear that would help a lot.

Another thing is that with a torque converter you can't steer as much with the throttle. If you lift a stick shift C4 it will stick the front end if it's just getting near the limit. Doing that with an auto doesn't do much of anything unless you are much further up in the rev range. It doesn't sound like much but when you are going through offsets and short choppy sections having that extra front end grip is huge. Again a shorter final drive would help this a lot, but with BSP rules we couldn't do that.

Automatic cars require a different setup because of this and Roger Johnson's C4 was set up for borderline hairy oversteer. Carriiere and Johnson could drive it but I never could. I was always a lot faster with just a touch of understeer and then pinning the nose with a throttle lift and when we went to the automatic BSP car we couldn't do that.

One year at nationals at the warmup Larry and I got to ride with each other. There was a nasty offset near the finish that was really fast. Larry drove it first and I felt it could be taken a lot faster with a slight lift and a toss to get thru it. I did it on my run and as we were approaching it Larry said something to the effect of "BRAKE"!!!! I just lifted to set the nose, and tossed the car thru and it went perfectly. Larry said he was sure we'd be smashing cones and was amazed we just shot thru, and not braking gave me almost a second in that split. Since this was taking place in a fast section it worked, but you couldn't do things like that if you were at low rpm in second.

Some automatic cars are set up with a lot of oversteer to get the car to turn, but you have to left foot brake them to increase the front brake bias and keep the car pointed in the right direction. This is a crutch but some folks are fast with that kind of setup.

Bottom line is that I don't think an automatic is as fast because it limits what you can do a far as weight transfer, but some folks can do it and it doesn't hurt them.

l98tpi

My .02 is; there are advantages and disadvantages with the auto. You do have to change rear ratios as Solofast said. Now my reasoning for a rear end change was for help with engine braking and I can maintain a constant rpm through the slaloms and transitions more often. Unless the auto you are looking at has a full manual valve body you will see inconsistent shifts. Even a tune with an electronic controlled Trans will sometimes have lags in shifts especially in higher rpms.

Your advantage with the auto will be left foot braking and no worry about depressing a clutch to shift a gear. Depending on a course set up you may or may not need to shift after the initial takeoff.

Hope this helps!

blackozvet

have you driven the auto car, or can you have a drive of it at a track you know ?
you could get a feel to see if you like the auto trans.

Im using the auto in hillclimb, these trans have a very low first gear, I put my shifter into second at the start, it shifts from first into second quite quickly and stays there. I dont have any issues with it downshifting. Some have manualised their boxes.
Its also an advantage for a standing start , has to be quicker over the first 60 feet. (im using a 3200 converter)

Solofast has some interesting comparisons, my car very much power oversteers, I left foot brake and I can trail brake into some corners.

c4cruiser

Good input guys!! I'm pretty familiar with the car I'm considering as the owner is a fellow competitor and I had helped him do some initial setup a number of years ago. We have also done some track days at local tracks and he says the car is rock solid.

A manual valve body for the trans is something I had thought about and it can easily be installed at my shop. I don't have a problem with having to shift manually; the '87 is a 4+3 and my '02 is a 6-speed.

I had a '92 convertible A4 that I used when I started out autocrossing but I can't remember much about how the car handled. It got me hooked on autocross and track days.

Unfortunately I can't get a closer look at the car or even drive it (it's still "street legal") until the end of November when the owner gets back home.

Anyone else that would like to chime in, it would be appreciated.

c4cruiser

So with thinking about a replacement autocross car, how can I go about selling my '87? I have a list of the mods that are on the car, but I would have no real way of knowing how the car would be classed in associations like SCCA or others as it sits now. I would expect that could make a difference to potential buyers.

Would it be reasonable to post up a list and let potential buyers figure out what class the car would be in at their local events? A buyer would get everything that I had replaced (OEM stuff) so it could be put back into street use but it would be hard to get around the engine mods for classifying (bored .030 over, ZZ3 cam, port matching, etc.)

I'll be ready to sell after my last event of the season (9/13) so the next step is writing up an ad. Should it go here in this section or maybe C4's For Sale?? Both places?

93Rubie

Sounds like a SSM car to me with the engine work.

c4cruiser

Also has headers, dual exhaust with X-pipe, Banski rear suspension components, and 32mm/28mm sway bars.

63Corvette

Spec Miatas are killer cars for autocross, 'cause they are cheap but "very" competitive!

NASCAR314

C4's with automatics are great with LT1 motors and at speeds under 65 mph where 1st and 2nd gear is all you need. I have 3.73 : 1 rear end gears in mine and it does very well, manually shifted and definitely "left foot braking". Higher speeds cause unusual handling on corner entry as mentioned earlier.

Tracks cause high trans fluid temps and related problems, unless your doing single laps such as an NCCC high speed autocrosses.

Having said that, mine is in the shop again with a broken planetary gearset in the trans. I up-graded to a 4L65E planetary (5 gears) from the 4L60E (4 gears) for higher torque handling. It lasted 14 months but to be fair, I am beating the **** out of it, with two drivers and many, many events + sticky 315 Hoosiers A's

I'm love my C5 Z06 "manual" back up autocross car (stock), it's been pretty bulletproof for me