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Thread: Controlling afr on the tbrake turbo setup

  1. #1
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    Controlling afr on the tbrake turbo setup

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

    On the tbrake 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.

    I have a forged 347, twin tc76's, small cam, th400 rmvb, ford 9" with 3.25 gears, synergy 2 step, eboost 2
    98 - z/28 Twin TC76's l forged 347 l boost cam l moser 9" l th400
    07.5 - GMC Sierra 2500HD D-Max daily
    09 - G8 GT wifes daily

  2. #2
    Advanced Tuner blownbluez06's Avatar
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    I don't really understand your question although my mind is dancing around it.
    I know this doesn't address your question, but in case you haven't played with it, while you're on the Tbrake, use your VCM controls to push timing and fuel values around to find the sweet spot and then transfer that to your tune.
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.

  3. #3
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    I'm trying to command a leaner afr while on the brake, but I don't want that same commanded afr while not on the transbrake. Like for 7lbs on the brake and 7lbs under load while driving on the street. Is it possible?
    98 - z/28 Twin TC76's l forged 347 l boost cam l moser 9" l th400
    07.5 - GMC Sierra 2500HD D-Max daily
    09 - G8 GT wifes daily

  4. #4
    Advanced Tuner blownbluez06's Avatar
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    Yes. use a relay to change the resistance of the ECT or IAT circuit and switch to that resistance on the brake. Adjust the resistance to something that puts you in a place on the table that you would never be otherwise.
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.

  5. #5
    Advanced Tuner blownbluez06's Avatar
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    For the relay: assuming Transbrake has a hot out of the switch. Pin 86 to ground 85 to your transbrake switch, say if you added 6.8k ohms to the circuit it put you where you needed to be. Cut one wire and connect one end to pin 87a and the other to 30. Then run a 6.8k ohm resistor from pin 87 to 87a. At rest the relay has pins 87a and 30 connected. when energized, the relay connects pins 87 and 30, so in order to complete the circuit, it has to go through the resistor. FYI, I just put a ECT sensor on my meter. At 80 degrees ambient temp, the resistance was 2.5k ohms. I put it in a glass of ice water and the resistance went to 9.3k. A 6.8k resistor should work well. if you want to interrupt the coolant temp sensor. It doesn't matter which wire you cut and place the relay in. Make sure you make good, solid connections. Get on the brake and log coolant temp to verify proper circuit operation. For fueling, I'm assuming you're in power enrichment mode on the brake. There is a PE vs ECT adder. in the temps around your target temp, you can actually have negative numbers in there, thereby reducing your commanded from your current PE multiplier. Take your desired PE on the brake, subtract it from the other PE off the brake and that's your number. Put the -sign in front of it and test it out. For spark, find the airflow values that you're falling under on the brake and locate the ECT vs spark table. At that temp and airflow value, place your desired timing modifier value in there. Now you have new spark and fuel values on the brake that are separate from not on the trans brake.
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.

  6. #6
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    I never thought of doing something like that. I'll give that a shot.

    I did get my car to footbrake to 3500rpm though. I adjusted my proportioning valve and it made a world of difference. I can get 1lb of boost now so that's way better. I leaned it out to get that, it was really fat in that area. I already had 30* commanded. What kind of timing should I do on the brake in psi ranges?
    98 - z/28 Twin TC76's l forged 347 l boost cam l moser 9" l th400
    07.5 - GMC Sierra 2500HD D-Max daily
    09 - G8 GT wifes daily