adjusting afr on transbrake to raise boost
 

whats the best way to command different afrs while building boost on the brake?

change nitrous jet

Have you adjusted the timing? Timing can effect how a car responds on the brake a good bit depending on your converter. In efi live there is a boost ve table and boost timing table that I use. Im not sure but I dont think HPT has those tables. I'll look tomorrow and see if they do.

What are you using to tune the car?

the pedal on the right.

I'm using hp tuners.

Footbrake wise, it doesn't build boost. I either need stronger brakes or a looser converter, it only goes to about 2000rpm.

On the brake for 2.1 seconds it builds 7lbs of boost. That's also with a rich afr and 30* starting ramping down to 18* of timing on the brake. The commanded afr is 7.71, which is on the e85 scale. This is exactly where I have it on the boost enrichment table. My concern is that outside of the transbrake, there will be other times at being at the low boost level which is when I would want to have that afr.

I don't see the boost ve or timing table, but there is a boost enrichment table.

I guess I can make the enable kpa higher to use the PE table and then go to BE table, but i'm not sure if that would work either for what I'm talking about.

Sounds like you need a looser converter

What kind of launch controller are you running? Reason I ask is I got the LNC-003 so I can set the two step up to hold X rpm on the foot brake, and Y RPM on the trans brake. Also I am with Bwelch the converter is to tight down low I don't think any commanded AFR/ timing ect is going to help, I realize your are running twins I have a big single but typically my car wouldn't start building boost until the 2700 range when footbraking ,my converter was doing 3400 foot braking and the car would leave on 11 psi. Can't help you with HP tuners though my car is EFI live custom 3 Bar.

Also if your standing on the brake in the burnout box you will heat the brakes and they won't hold worth a shit, my car pushed through the beams a couple times when I was setting up the two step in the pits brakes would hold fine got on the track and the car would push out JP says Do it Bad Bob style problem solved. use a line lock or do it bad bob/ John Force style.

I have a line lock but something isnt right with it. So i have to use the brakes to do a burnout. Im going to get some drag brakes and see how it acts then. Which way does the proportioning valve have to be to direct the most pressure up front?

I forgot to mention i have a synergy 2 step.

Until you get the brake situation figured out pull in the water box wet the tires put it in first get em to spin grab second then when it starts to creep out grab third the higher gears will load the turbo and the car should have no problem keeping the tires turning. It will also put good heat in the hotpipe side and help it spool faster when your ready to launch.

Proportioning valve would depend on brand ect, see if the manufacture has some instructions.

:cheersSo it is a two step with a single limiter and it does some magical shit with timing. The timing part scares me since I don't like the idea of something effecting my own parameters, and the fact that you can build two identical motors and they will run different every time so there is no way in hell that its timing magic will work optimum on all cars. I does have the fastest studder rate I believe of the group. Hopefully I didnt hurt your feelings thats not my intent.

This is my two cents on the subject. Since you are running a auto I would get a MSD 3 step or LNC-003 since they have two limiters one for the foot brake that you wire as the secondary off the brake pedal, and wire the primary off the transbrake and set the limiter even higher. They are plug and play and easy to set up. I installed mine in about a hour.

There are several advantages with the 3 step setups over a two step first is the ability to leave on the foot brake first figure out where the car is going to blow brakes by standing on the brakes and bring the RPM's up until the back tires break loose set the limiter for 100 or so RPM less than that and the car wont push through the brakes anymore and you can mat the go peddle on the foot brake and build boost just like you do on the trans brake. Next set the primary limiter to come on when you go up on the transbrake. And bring the RPM's up to wherever you want it to launch at.

Here is the big advantage, after your burn out. Get up on the foot brake with the pedal mated and stage by letting up on the brakes a little and letting the car bump forward all the while the car starts spooling the turbo as soon as the second light comes on hit the transbrake button car will already be under some boost and will immediately come up to whatever its gonna make on the transbrake so you don't have to worry if the boost is gonna come before the lights drop. If the tracks not working well that night and you cant catch traction just don't use the transbrake and leave on the foot brake, or you can make quick adjustments to the primary to make it work by raising/lowering the primary RPM until your happy with the launch. You can also use the footbrake to get a good burnout going on the street or in the burnout box.

3 steps are the way to go on a Auto/ Turbo car period. That synergy is awesome for a 6 speed car but just doesn't have the capabilities of a good 3 step.

My synergy unit doesnt mess with timing. My timing logged is what is commanded. Im aware of the 3 step option as well. I was thinking about doing one of the plug and play units but i already had tjis one all wired up and didnt want to have to deal with selling it as used. I will get he bump box before i get the 3 step setup.

Im going to check the brake situation out, but the original question remains. I think leaning it out will dramatically help out, but i dont want to take that fueling out for normal driving. If it was a track only car then it would be easy.

I should have some time to check it out today. I'll post up what I find

adjusted the proportioning valve and i can get to 3500rpm now. I leaned it out and have 30* and can only get 1lb of boost. Im sure if i had the 3 step it would be better. I may just use the 2 step for staging and then leave off of whatever rpm the brake goes to. It feels much better now. Im hoping for a better 60ft

Did you try adding fuel?

What does the car do on the transbrake?

If it's making 1 psi on the footbrake without the two step at part throttle its doing pretty good, you really need to be able to open the throttle body up because the extra air will really wake the turbos up. The only why to do that is with a two step set just below the 3500 rpm limit.

Your second option of using the synergy for the footbrake, and transbrake to the moon will work but it is going to stress the drivetrain pretty hard namely trans temp, but as long as you got a good cooler and a way to monitor the temp you should be fine. Car will probably go up to about 4K on the brake as turbo converters really tighten up as you go up.

Make sure your wheels are pointed straight. lol

The fuel was there already, that's what made it sluggish. I leaned it out and it seemed to like it. Previously it would only go up to 2krpm and 62kpa, now it goes to 3500rpm and 104kpa. I think it's going to liven up the hit quite a bit. The afr was 7.6 and is now 9.0 on the e85 scale. I tried adding timing first, but it didn't help. So i backed that off and leaned it out and it made a world of difference.

transbrake will definitely take it to 4800 because that's where I was leaving before. So this option may work, but the reason that it might not I'm hoping is because of too much boost. I'll just have to wait and see this weekend as long as it doesn't rain.

twin 76's on a 346 and a 2k stall converter doesnt sound like it would work all that well.... lol bet a converter would make it a different car.

You can try an remove more timing. That will increase EGT's and may help some as well.