General Cam tuning with an Auto

[Nate355RS]

I'm in the process of getting my IPT 2800 stall and FP Green to play nice together off the line, without nitrous. I want to pick some of the auto guys brains about overlap and cam timing for getting an auto to launch hard. It seems like the general consensus for cam timing on our cars is less overlap means more power. But my understanding is that it also decreases lower RPM power which is bad mojo for a guy in my situation. I'm having a hard enough time getting on the converter and building boost as is with the cams straight up. I've tried high timing lean AFR, low timing rich afr, and everywhere in between. My launching has gotten better, but it's still not where I want it to be and I think cam tuning might be able to help.

Does anyone with an auto tune cam timing for launching? If so what settings have you found to work best to get the car off the line and down the track?

 

[Vegas Smith]

@Kapok6

 

[Kapok6]

What cams do you have? My HKS 272's stalled up my converter with a DSM76 HTA in 10sec. My S2's s were very difficult to get to spool and even when I got it to happen, it took way too long. Conventional wisdom says Retard the exhaust cam or advance the intake cam. (increase overlap). That stuff didn't work for me on this setup. I actuslly decreased overlap and was able to get it to stall, but again, it takes longer than I'd like, so I put a dry 35 shot on, it stalls in like 3sec and I don't have to worry about stressing the trans out by making the fluid stupid hot.

 

[Nate355RS]

I have the HKS 272s, I'm in the same catch 22 situation you were in. Increase overlap for boost off the line, or decrease overlap for crazy long stall time. Nitrous is the simple answer, but I really don't want to go that route yet until I'm sure I have the launch as good as I can get it without.

 

[GST with PSI]

You can also play with the anti-lag feature to try and get boost up on the converter. I've read about a few guys using it successfully.

http://www.dsmtuners.com/threads/auto-brake-torquing-2-step-anti-lag.272887/

N2O is nice because it will spool up almost immediately, which lowers the time you're on the converter cooking the trans. If you don't have a legit trans cooler, N20 will let you cheat a bit. Depending on your setup, you may not have the luxury of staying on the brake for 10 seconds while the car stalls/spools up.



On an unrelated note, it's nice to see some of you regulars commenting and tagging others who you know have the knowledge and experience to directly address the OP's particular question(s). That's the way this place is supposed to work . Thanks.
@Vegas smith @Kapok6

 

[Chumpaumpalumpa]

Again use the ALS function. And again get a 35 or 50shot for spraying on the line and through first even. If you "have the launch as good as I can get it without."You're going to have to completely retune when you switch to nitrous. Just do it the easy fun Less hassle way. You'll see longer trans life too since you won't be trying to boil the fluid

 

[Nate355RS]

The biggest reason I'm not running nitrous now is because I don't know a single shop that sells it in my area. If I could get it I'd be all about it. I'm still looking, but I'd like to get as much as I can out of my setup now.

I tried ALS but the auxmaps worked better for me. I like having more control over timing and AFR than just locking in single values. My launch isn't terrible, just not what I want it to be.

Kapok6, that's interesting you stalled better with less overlap. I would've thought just the opposite. I'll probably give that a try, sounds like a good place to start.

 

[Kapok6]

I had to just play with cam gears a lot to see how the car reacted.

I was surprised myself, about my results when decreasing overlap. I'm not saying it gets over the "hump" quickly. It still takes longer than I would like and fluid gets warmer than I want, but it will do it. I didn't set my cams where they are for the purpose of stalling up though. I was playing with them to try to tune out some knock. The car idles a lot smoother, but the powerband was shifted significantly to the right. The stall up was just a side benefit. Having gone with a 35 dry shot though, I can't see myself ever looking back.

As for nitrous, you may be surprised at who sells that stuff. A place near me that sells lawnmowers and tractors and stuff also sells nitrous fills and race gas.

 

[b00stedtalon2]

On my car, advancing the intake cam 4-5* and leaving the exhaust cam at 0* helped a lot. I only lost about 1mph in the run.

I still prefer nitrous. I put a 50 shot on and it stalls to 3800 in under 2 seconds. Feels like a manual car revving up to the 2 step. My trans temps are also much lower at the end of the run.