I don't know anything about what values are used for two steps when building boost so can someone suggest some ballpark numbers for setting up the 2-step in MSPro that will get me close? See table.

Some Details:
2002 GT, 4.6, 2V, E85, 32-35psi boost street car
4R70, 2800 stall triple disc lockup
Launching off foot brake with slicks
Foot brake into as much boost as I can get.
Line lock will be on Rear brakes while foot braking
2-step will be activated when line lock button is pushed.

Thnx
Kevin
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Set the limiter to an RPM that you can achieve while holding the brake. Say 2600-2800. Then you can try pulling timing out into the single digits and see if it will light. I've had success doing that.
I'll add that I don't like the line lock on the rears only. Good in theory, but didn't work at all for me.

 

I got the 2-step working, now I'm making adjustments to try and get more boost while power braking:

1. Currently the timing is -15 to -20 ATDC - Question: How far can I go? OR How far have people gone to build enough boost?

2. Adding Fuel (Fuel Addition ms): How much have people added in order to get the explosions violent enough to build boost? I tried the recommended .5ms then 1.0ms and not much difference between these settings. Is this too much or not enough..? I have no frame of reference for what settings people use.

My issue is I have a 2800 stall (full street car complete with three mufflers) so I can't get much RPM to spin the turbos to build a lot of boost unless the launch settings can still be adjusted. I get no violent explosions or flames out the pipes but this could be due to running three mufflers.

With settings of -15* to -20* ATDC, Fuel addition of 1.0ms and Hard Launch set to 3100 RPM I can powerbrake it to get 6psi of boost but that's it. I'm still working on the brakes to try and hold the rear tires from moving so I MAY be able to get a bit more RPM but I'm not counting on it. Hopefully there are settings that can be tweaked to get more boost otherwise I will chalk it up to not enough RPM/stall to get any more.

KS

 

The three mufflers may be part of the problem. Backpressure on the exhaust side of the turbo is multiplied by the pressure ratio, IE a small change makes a difference in spool. Is a cutout at the bottom of the downpipe for the track possible? (assuming you aren't using the 2 step for the drive through).

3 mufflers and a turbo seems like really a lot, what's the deal?

 

Three mufflers is probably the majority of the issue, I'm completely aware of that, but it's part of the car design that I am willing to work around or accept the limitations it creates. I just want to make sure there isn't something in the tune that I'm missing, or could do, that may help a bit more. Like the additional fuel, I have no idea what people have run. Is 0.5ms a lot? Or is 1500ms acceptable?

If I can't get more than 6psi it's not big deal and I'll take what I can get. I don't need a great 60' to run the MPH but I want to do whatever is possible to get a good 60', plus all the more fun. On the street once the boost gets to 9psi it will hit 32psi in 0.4 seconds but it's just getting it up to 9psi that takes a bit of time.

This is a pure street car that is quiet and comfy with AC and enjoyable to drive every day. After 30yrs of driving "race" cars on the street I got sick of the noise they make so I wanted to build something that is really quiet, smooth and will still run over 150mph in the 1/4 in street trim (except slicks) so no exhaust cutout. It has great power now so I'm hoping I get to test it at the track this year.

The 3rd muffler is something I built myself and works great for canceling noise. Both turbos feed into this then exit into a pair of Dynomax units in the stock location.

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ks

 

Quick Update for the archives:

I wasn't adding fuel correctly. Someone told me to use 50% of the inj pulse width that is set in the tune. This is incorrect. You want around 50% of the PW while the engine is loaded at the 2-step RPM.

For me the inj pulse width while power braking was around 6.0 ms so I added 50% more fuel (3.0 ms) and set timing to -20* ATDC. I can't say that it made a lot of difference, maybe .2-.3 psi more and no major popping/flames out the tail pipes. I'm confident that this is b/c of the mufflers I'm running. Boost was around 5.9psi at 3000rpm.

I tried -25* ATDC then raised the 2-step RPM from 3100 to 3200 and this was worth another 1psi while power braking but it's difficult to hold the rear tires from turning even with the ebrake on and my foot through the floorboard. Currently it's getting 7.0psi which is definitely better than nothing so I will take it. I think adding the additional 1000rpm to the 2-step did more good than the timing/fuel changes but I will leave it for now.

Hopefully when I get the line lock installed on the rear brakes I can pump up the rear brake pressure beyond the ebrake pressure and hold the rear tires from turning and maybe get a bit more RPM or at least hold the car more steady. I'll then dial back the timing and fuel to the point it starts decreasing the launch boost.

ks

 

What is your brake setup on the car ?

 

At this time just factory 2002 equipment w/o ABS. Once I get the line lock plumbed to the rear brakes I will test it and if needed update the rear pads to something that may hold better. That's about all I will do to the brakes.

ks

 

Are you still running the factory proportioning valve ? If you are it is most likely limiting pressure to the rear brakes. It may help to go to an adjustable one and turn up the rear bias.

 

I'm hoping the line lock on the rear brakes will eliminate the need but I'll see.

ks

 

This had me curious so I pulled screenshots from my MS2 for the 2step. I don't have the options you do in terms of added fuel. When I set it I checked it in neutral to see how it worked, somewhat taking the brakes out of the equation.

My plan is similar to what you describe -> tie 2step and line lock together and get brakes to hold.

I guess I don't have much to add but I'm in for updates to see what you learn
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It may not be what you were initially thinking of, but have you considered plumbing in a small nitrous system? Have the system turn on when you hit the line lock (might be tricky with part throttle, though) and shut off when you hit the desired pressure. Or, have the system on between atmospheric (0 boost) and 9 psi and between 2500 and 2900 rpm only. Have the relay control the ground on the solenoid, it is less noisy that way. Nitrous makes a lot of exhaust gas and it can spool turbos like a shot. It is really only a starting line aid, not used for power production so a 5 lb bottle should last quite a while.

 

Naaa...

 

Never know, it could be fun. One tube for the driver, one for the engine.

Just kidding about the driver. If you're driving something like what you have, you need to have your wits about you. That is a very serious car.

Nitrous as a starting line aid does work pretty well. I used one on a bracket car and could get to desired MAP in one bulb on a bracket tree. Otherwise it sounded as though we were trying to drive the crank through the radiator.

 

ha...funny.

I used nitrous for 20+ years starting in early 1980 so I'm well versed in it, just don't want it anymore.

Once the car gets to 7-9psi of boost it only takes 0.4 seconds to jump to 32psi so in reality any small delay isn't going to hurt the 60' too much. I'm still waiting for the relay board to arrive that controls the line lock/2-step but I hope to get things installed by the end of the month.

In the meantime I'm converting boost control from the EBoost2 to the the MSPro and currently working on the tune settings.

ks