Supra Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1 (Edited)
My father recently picked up an mk3 with a completely stock block 2j/ bw s366 single/ th400 w/trans brake and 4200 stall. Im completely new to the track scene and the th400 scene and have always ran a 6 speed mk4 so hopefully you guys can point me in the right direction. This thing is a complete dog trying to spool it on the line to get a decent launch (probably 15-20 seconds pedal to the floor to get it into boost). Whats our issue here? Good buddy of mine recommended doing a small 50 shot to help it spool but would like to keep it off the spray if possible. Once it gets into boost its an animal! If any of you guys can make any recommendations and help me learn a few things id appreciate it!
 

·
Registered
Joined
·
668 Posts
how many rpms are you hitting on the brake loaded up (I assume you are on the cars brakes and not a trans brake?)

what electronics are you running (stock jz, stand alone etc).

is it powering through the brakes so that you are feathering off the gas --- or are you saying the brakes hold the car for a solid 15 seconds before boost starts to build
 

·
Registered
Joined
·
5 Posts
Discussion Starter #4
I should have been more clear. The car is on AEM and starts to spool around 4k, it takes us about 10-15 seconds on trans brake to even get this thing into boost therefore, getting tree'd on every single pass (thank god we dont race competitively) I just spoke with the previous owner who stated they never got it fine tuned because it would always push through foot brake before they installed the trans brake. Pullng a little timing may help us a bit.
 

·
Banned
Joined
·
96 Posts
Nitrous is a cheap/easy solution.... tuning the ecu to make the turbo spool easier by pulling timing near the boost threshold will help. A LOT of this is physical parts setup, however. As in, your hotside might be too large. Your stall might not be high enough.

If it were me and my car, I'd use the nitrous to get it on boost at the line and run the setup you have. Of course this doesn't negate the fact that you very likely have things to address in the fuel and timing tables on the ecu.
 

·
Moderator
Joined
·
4,932 Posts
Nitrous will definitely help. However, given you have a 4200 stall, you don't need it.

Going to be easier if you find someone that knows how to tune near you, otherwise you'll be slowly going at it yourself (fun but will take a while).

Can you post your timing map? If it takes 15 seconds to build boost on the trans brake, it sounds like you don't have enough timing on the low end of your map.

Should do basic maintenance first: verify plug gaps, verify timing at TDC is correct.

If you've got a trans brake you're in luck because that makes it infinitely easier than dealing with a footbrake and trying to stage. With a manual car, you can just retard the timing a ton (run -15* or so) and the car will spool very quickly. With an auto you need to keep some timing in it, because the converter needs torque in order to spin so you can't pull as much. Take the timing down to 5* or 0* or -5*, and lean the AFRs out to 13.0-14.0 and it should spool real quick.

I can spool a 6062 at 3000 rpm doing the above to 10 psi in maybe 3 or 4 seconds without a trans brake, just using two step.



Just for clarity, because in one breath I said 'you don't have enough timing' and in another I said 'pull more timing'...generally on a trans brake you should build boost because of the load on the engine if you're running enough timing. If you aren't, you don't have enough timing in that area of the map. If you lower timing even more, you'll start spooling the turbo with the exhaust energy...which will build boost. It's like a dead zone of timing in between.
 
1 - 7 of 7 Posts
Top