I know that autocrossing related posts should be in the roadrace/autoX, but I figured more guys on this portion of the board would be knowledgeable about auto transmissions.

I'm in an AutoX class that basically allows bolt-ons, tunes/aftermarket ECUs, minor weight reduction, LSDs and clutch/torque converter replacement and wheels/tires (R-compounds). I've got an 07 5AT. I don't plan on switching to a manual, unless it becomes readily apparent that it is far superior. The class is what it is, so I'm not shooting for another class that'll allow turbos/cams/superchargers/etc.

I'm building a roadmap for my changes to the car, and I understand there are at least 2 companies making an aftermarket torque converter for the Z. All the autocrosses I've attended have a standing start, so favorable launch characteristics would benefit a tenth or two.

Considering that it'll likely have full bolt-ons only (no real internal changes), I'm assuming a ~30-40ish HP gain over stock, and maybe 100-150 lbs less than stock. (feel free to let me know if my numbers seem off. I'm no expert here.)

I'd like to know anyone's experience (if there is anyone with that experience) of similar power levels and going to an aftermarket torque converter.

1. General remarks about differences in feel/behavior?
2. Change in dynoed HP?
3. Change in MPG?
4. Weight differences?
5. Other measurable performance differences?

Basically, I'm trying to see if an upgraded torque converter should be slotted into my preparation roadmap, and if so, where.

PS, adjusting the nut behind the wheel is the first priority.

 

i maybe wrong but if you just doing bolt ons and a tune i dont think you will need after market tq converter until you hit FI.

 

What use would a tq converter be for autocross? I figured tq converters were for getting out of the hole at the strip.

 

I don't know if you have any experience with autocross, but
1. It features a standing start. A good launch can make several tenths of second difference in overall times. It can easily make the difference in ranking.
2. Considering that I'll see some 10+ turns within 40 seconds, removing an operation that requires concentration (manual shifting) means more concentration on car placement and throttle control.

I think, effectively, I can be as fast as a manual in an automatic Z on an autocross course, and I'd like some help in exploring an alternative option.

 

I am currently running an edge racing tq convertor with a 3200 stall.

1. General remarks about differences in feel/behavior?
It feel stock. People told me there would be a noticable difference in drivabilty and there wasnt. The only thing you may experience is occasionally rolling backwards on a very steep hill.
2. Change in dynoed HP?
I dont have any back to back comparison on the dyno. From what I have read is that it actually takes away some HP.
3. Change in MPG?
Never paid much attention to this but it shouldnt affect it at all. Like I said it drives stock.
4. Weight differences?
Its basically a modified stock tq convertor so weight shouldnt change.
5. Other measurable performance differences?
As you know the biggest advantage is that you can launch your car at a higher RPM than what you would be able to stock. I drag race alot and I very rarely actually launch at 3200(my stall) mainly because my local tracks are not prepped well enough to do it. On a perfectly prepped track Ive been able to pull 1.64 60' foots on slicks launching at 3200 and 1.8 on street tires. I really dont think it would have happened with a stock stall.

Do you have an aftermarket valvebody?

 

PM Gator he auto- x in his 5at Z he even changed out his gears and LSD.

I don't know if he has a modified TQ maybe upgrading to a 3.5FD or 3.7 would be better.

 

AJ you launched at 3200 that day? I wish I could launch that high.

 

Yeah man I actually rev'd it a little to high one run and the car started moving before I was ready.

 

No aftermarket valvebody. It doesn't appear that the ruleset I'm building to allows it.

I have the manual ring and pinion ready to install. Ruleset allows me to swap between OEM 350Z ratios only. I'm waiting on the fundage for the LSD (likely this winter). Once the LSD is purchased, I'll be swapping out the pumpkin to 3.5 ratio, LSD and delrin or poly diff bushings (metal not allowed).

If ajcool is correct on all counts, then I won't be needing anything until I switch to R-Compounds. I may have to get in touch with the manufacturer to see if it's worthwhile.

drivetrain-wise, it's been recommended to me to add a trans cooler. Can anyone speak to this?

 

My limited autocross experience there is usually a 90 degree right or left turn directly AFTER the starting line. The purpose is to keep starting speeds down. Can anyone any vehicle finish the first 60 feet in say 2.0 seconds? Highly doubtful.

Torque converter is not a popular subject in the autocross forum because it is for practical purpose useless.

 

I do acknowledge that most of the autocrosses I've been to have had a turn within 30 feet from the start, but some 20-25% of them do a standing start with a short straight. It all depends on the course designer.