EVO8LTW

iTrader: (41)

I'm planning to get back into autocross this season and was thinking of trying to do a 2nd gear specific tune and making it my alt map. Since the load on the engine is so different in 2nd versus higher gears, I would think that the tune could potentially be more aggressive if the car is not going to see more than 2nd gear.

Has anyone else tried to do an autocross specific tune?

Thanks!

211Ratsbud

iTrader: (1)

Step one raise rev limit to 8100. Step two. Mbc. Step three.. well I wanna know too lol..

RJones

iTrader: (5)

Why would you need a MBC? Everyone I know has ecu controlled boost...

cij911

iTrader: (14)

Ughhh....I am sorry but this ^ is useless advice.

Unless you know the course, it is hard to know which gears you'll be using. My guess is you'll be in 2nd and 3rd gear for most courses. As we have already discussed in PMs, you want to have a really responsive turbo - not crazy power and develop a nice fat powerband. Secondly, you should spend most of your time and money on the suspension and tires (depending on class rules).

To get back to your question, I would focus your tune on gears 1-3 focused on transitions and keeping the turbo spooled. Autox is quick vs road racing (on the course for a minute or so vs hours), so you'll likely be able to add timing.

Good luck

211Ratsbud

iTrader: (1)

I havent yet found a course. Where a raised rev limit cannot be of some benefit.8100 was an arbitrary number

EVO8LTW

iTrader: (41)

99% of the autocross courses I've done are all 2nd gear, so that's where I'd be focusing. I'm switching from my FP Black to a BBK Full (got a good deal on a used one), which should be closer to the response level that's worked for me in the past (FP White Rabbit).

My suspension is already fairly tricked out (Ohlins Flags, all ES bushings, WL RCA kit, etc.) and I still have my 18x9.5s that I used to run 285 R compounds on, though the nut behind the wheel is certainly a bit rusty after a few seasons off.

I guess I'll just have to experiment with the 2nd gear tuning and see what happens.

tscompusa2

iTrader: (22)

just tune the car in 3rd gear and then after youre done go through the gears to confirm its safe. for a road course car id tune it richer and make timing conservative to be safe.

MiTech

iTrader: (4)

I 100% percent agree because you are going to need fuel to make the energy to sustain it so it can be on the road course so remeber to be a lil extra rich

Mike

03whitegsr

iTrader: (8)

A fairly aggressive 3rd gear street tune for drag racing is too aggressive for auto-x, from my experience. While the load may be lower in 2nd, the constant on-off-on throttle and then being usually 60+ seconds in length builds up enough heat that you need to back off a bit.

You may want to verify you don't get large boost spikes nailing the throttle at like 5k RPM in 2nd gear.

I've kept my AFR fairly lean as it tends to make power delivery smoother. Also, I have fully tuned my car at every boost level from wastegate pressure to maximum boost. I have done some part throttle high RPM tuning as well. I feel this makes for excellent power delivery. Most seem to only tune the high load RPM path and smooth everything into that and it can leave the car pretty conservative off maximum boost.

I also turn the boost down a bit from the street setting as the huge surge of torque from a little turbo on high boost really doesn't help me out at all. Just upsets the car more then anything. That could just be my driving style though. I tend towards a slightly more traditional line where I know a lot of fast AWD guys go for a more "point and shoot" type of line and the torque might be better in that driving style.

RJSP

I am no expert but have been Autocrossing for the past year and self tuning my car (following a lot of the great advice in this forum). I agree with tuning in 3erd gear and also doing wot pulls at 5000 (in 1 -3 gear) to verify. Part throttle tuning also helps.

Track days (non competitive Autox events here) are great for setting up the car, one time I did a log of a 50 sec Autox course to verify tuning, had a copilot holding the computer .

My car is lighter than most 8´s or 9´s and I kinda like to drive point and shoot style going wot quite often in Autox, so I don´t mind the fast response of a stock turbo spiking to 25 -26 psi, I even added a 22 psi WG actuator to spool even faster! Had to port the exhaust housing wastegate ports and also installed the mbc as close as I could to the cormpressor and WG to lessen the boost spike.

I don´t know how to post a link, but if interested you can look at a video I posted of my car in an autox run.

Good luck!

Ricardo

cij911

iTrader: (14)

Agreed.

To the other post, he is NOT road racing, rather autox, so the time "on" is likely between 1 and 2 minutes (depending on course). Per my earlier recommendation, you'll really want to first tune your new BBK (in 3rd gear), and then refine in 1-2-3, 2-3-2 type bursts....

If you think you'll be in 2nd gear almost 100% of the time from 4k - 8k rpm, then make sure you spend 2x - 3x the amount of time focused on that area...

As to what RPM limit to set - this should be based off your engine. IIRC you have a built motor, so you could likely go as high as 8500 - 9000 rpm (if built properly). That said, you'll really need to look at your power curve to see if you should be shifting a lot sooner (more like 7500) - it really depends on the course, engine, and driver....

RJones

iTrader: (5)

It's rarely quicker to shift to 3rd than to just bounce off the limiter in 2nd in autocross... That's something to think about too. It may not be that worthwhile to focus a lot of effort on the 2-3 transition.

RJSP

One thing I forgot to mention, when doing 1rst and mostly 2nd gear Autox courses the peak boost I see is at most 21 -22 psi, eventhough my car reaches 26 - 27 when going wot on 3erd gear and above. I guess this is because of the decreased time to load the car and the fact that we are staying in the 5K - 8K rpm range for most of the time.

I´m not sure of the best way to incorporate this into the tune, maybe just logging simulated Autox driving would help, to improve on a good normal 3er gear wot tune.

Cheers,

Ricardo

cij911

iTrader: (14)

Use the v7 mod and use the Ecu to control boost via psi rather than load...That said, you may not be able to hold more than 22 psi at redline depending on what turbo you are running (out of its efficiency).

The downside about bouncing off the rev limiter is you are cutting fuel, so I don't think that is a good approach. Either raise the rev limit to accomodate the track or learn to shift faster . One also has to look at their power curve and choose gearing correctly...

Segfault

iTrader: (5)

I can count the number of times I've been in 3rd on one hand. Most courses don't benefit from going into 3rd as RJones said; the time wasted shifting is almost never beneficial. Bouncing off the top of 2nd gear for a few seconds isn't going to cause any real probs. Check out a few vids from Marshall Grice, Craig Wilcox, and Tom Berry and see what they do.

As for tuning for 2nd gear, this is something I'd like to try myself.