Getting ready to Dyno my DR750s, some timing related questions

[fastfalcon94]

My friend Jason owns VEMS (VEMS US | Versatile Engine Management Systems (http://www.vems.us)). It's the only AWD dyno in Vermont and happens to be about 10 minutes from my house. I am renting the dyno from him in the next couple of weeks for half a day, maybe even more to tune my DR750s. I had Ray do a base tune for me last year. Since then I have became very familiar with AEM. I'm running more meth, different exhaust, bigger injectors etc... I adjusted my fuel table, setup my knock table, and failsafes. The car feels really good at 25psi and an 11.3 afr. However I have never touched the timing table. I know Jason knows what he is doing. He built his own EMS ECU chip and software, but I'm curious on exactly how other people go about this. I figure I'd like to learn as much as possible before going in there.

From what I have read online, they look at the torque curve and will advance timing until you stop making power, then back it up just a little so the car will be safe. But what exactly goes through the tuner's head? Do they start with an rpm range (say 3500-4000), increase it, smooth out the timing leading up to 3500 rpms and after 4k rpms, do another pull, then compare?

This is kind of how I did it with my old DSM at the track, but I never ran Meth in any of my DSMs. I'd try a little more timing, if I saw it knock and the ecu retarding itself, I would back it off. I heard this is bad when using meth as it can hide initial signs of knock. I don't want to pound my bearings.

His Dyno is also different than normal ones. He has a Land and Sea AWD Hub dyno (as seen here AWD Dyno | VEMS US (http://www.vems.us/dyno)). So I believe he can actually tell the dyno to hold at a certain load. With AEM I could hover right in a cell block, increase it, and watch in realtime if it's making more power or not. I wouldn't want to do this for every cell though so maybe choose a few points, do this, then smooth it out?


94 vr4 4 bolt motor
Rays pistons/rods/wrist pins
port/polished heads
dr750s
1000cc pte injectors
aeromotive fp
800cc meth
AEM EMS v2 running speed density
HKS DLI
3" borla exhaust with mufflers cut out magnaflow straight through high flow mufflers, downpipe, no cat just a vibrate resonator
brand penn 20w50 oil



Here's a pick of my Suby on his dyno last year. My car is at 25psi right now, I was thinking of keeping it there or possibly going to 27psi. I don't have Ray's head lift fix.

http://i1192.photobucket.com/albums/aa327/fastfalcon94/subybuild/135.jpg

[J. Fast]

What does your current timing map look like?

[fastfalcon94]

This is my timing table.

http://i1192.photobucket.com/albums/aa327/fastfalcon94/aem/timing_zps2bbf801d.jpg

[NOMIEZVR4]

in....

[fastfalcon94]

This is what my friend Jason said about timing and holding a load on his dyno. Still not sure how he decides what RPM/load points to pick.

"Yes, it can hold a load, up to 2000AWHP, so no problems there. The only problem ends up being the car's cooling system when holding load like that. What you're trying to do is find MBT (minimum best torque) which is essentially the minimum timing for the best torque output. What you do is find where the torque tops out and reduce the timing to where it started to top out. It's much safer than the wait until it drops and back it off. I do that all the time when tuning. With Subarus since the ECUs are so painful being flash based, I don't do every load cell, as it would end up being a super expensive tune for customers."

[mjannusch]

Start with your regular tune, and make a full pull in whatever gear he wants you to run. Bump up timing 1 degree across the cells you were in and make another pull. If any knock, or torque doesn't increase then back it down. Repeat as necessary. For cells above and below, figure about .75 degrees of change per psi (+.75 for each less psi of boost, -.75 degrees for each additional psi). If you have time, you could back the boost down to 15 psi and repeat the bumping timing procedure and then vertically calculate the timing between the 15 psi and 25 psi rows to get in the general ballpark.

If you try to hold the load with the dyno for very long, I think you'll find the limits of the cooling system pretty quickly. There's just not enough airflow to keep the coolant temps down, no matter what kind of fan you point at the radiator.

[J. Fast]

This is my timing table.

http://i1192.photobucket.com/albums/aa327/fastfalcon94/aem/timing_zps2bbf801d.jpg


I happened to tune a DR750 3/S on a V1 AEM. Here's what my base timing map ended up looking like.

http://i788.photobucket.com/albums/yy163/JFastMotorsports/timingmap_zps1da102f0.jpg