A/F and timing while on the Trans Brake

T Hogg

Member
Hey guys, need a little help fine tuning my launch while on the TB. I was wanting to know what my A/F and timing should look like while on the 2 step and TB. Currently I have the 2 step set at 3600 and leaving on 6-8 lbs. My data log shows about 24* timing and the a/f bounces from 18.0 to 11.0 when hitting the 2 step. Would like to leave on 10-12lbs with not much more rpms. Is this possible?
 

StruckBy

FAST Eddie ;)
The a/f is bouncing around like that because the ecm thinks the engine is mis firing. What efi system are you running Terry?
 

rudder9

Active member
I would like to try an explain how we do this on my brothers car, but it's hard to put into words. Just like Ed said though, your seeing an artificial a/f because of the 2 step. You said your set to 3600 on the 2 step, but what is your launch rpm on the TB. We will usually set the 2 step below the tb to get some spooling and rpm and then hit the brake. That rpm is usually 400 rpm or so greater than the 2 step which will provide additional psi for launch. The a/f isn't so critical while doing this as much as the a/f transition once you leave when the real load is applied.
 

rudder9

Active member
Lean is mean and it will require tuning on the 2 step and brake to get where you want. I'm around 12.8-13 on my truck while on the 2 step. I was using a classic Fast. There will be a balance also with the brake where you want the torque to applied on launch, but keeping wheel speed in check so you don't blow the tires off every time.
 

T Hogg

Member
Launch rpm on the TB? Not sure what you mean. I foot brake until it starts pushing through the FB then roll into the first beam, hit the TB, floor it until it hits the 2 step, then leave on 6-8 lbs.

So are you saying I should set the 2 step just below the true stall? Also what A/F should I see when it launches? Right now it starts going down to 10.8s then back up to 11.20-11.5 through 1st 2nd and 3rd. Not too concerned about wheel spin w/ the 31 X 14s out back.
 

rudder9

Active member
This is kind of what I was saying that it's kinds kind of hard to explain. We go in the same way your saying you do but we run 2 rpm chips, one for the 2 step and one for the brake. Scott also has twin caliper rears so he can sit on the 2 step and not budge. The car is aiming for about 13.5 a/f while staging. I think your giving up some power if your dropping to 10.8, that would be leaving some power coming out of the hole, but it also depends on how fast your O2 is reacting. I had a similar problem this summer, I would drop to the high 9's after launch and we slowly tuned it out to 11.2-4 and my truck picked up all summer in the 60' and 330'.
 

T Hogg

Member
Ok. Good thoughts. Ill raise the AF and 2 step closer to true stall then see what happens.

What a/f do you see in 1st and 2nd?
 

StruckBy

FAST Eddie ;)
Launch rpm on the TB? Not sure what you mean. I foot brake until it starts pushing through the FB then roll into the first beam, hit the TB, floor it until it hits the 2 step, then leave on 6-8 lbs.

So are you saying I should set the 2 step just below the true stall? Also what A/F should I see when it launches? Right now it starts going down to 10.8s then back up to 11.20-11.5 through 1st 2nd and 3rd. Not too concerned about wheel spin w/ the 31 X 14s out back.

Terry your truck is pretty radical. It would be cool if you go into the first beam on the trans brake then creep in to light the second bulb. You could do that and eliminate a lot of extras if you went aftermarket efi. Are your 60' times where you want them?

- - - Updated - - -

This is kind of what I was saying that it's kinds kind of hard to explain. We go in the same way your saying you do but we run 2 rpm chips, one for the 2 step and one for the brake. Scott also has twin caliper rears so he can sit on the 2 step and not budge. The car is aiming for about 13.5 a/f while staging. I think your giving up some power if your dropping to 10.8, that would be leaving some power coming out of the hole, but it also depends on how fast your O2 is reacting. I had a similar problem this summer, I would drop to the high 9's after launch and we slowly tuned it out to 11.2-4 and my truck picked up all summer in the 60' and 330'.

Gregg is right on the money here.
 

rudder9

Active member
Not on Scott's car. He's never had an issue staging. He lights off quick. Converter issues? That's a different story.
 

T Hogg

Member
Terry your truck is pretty radical. It would be cool if you go into the first beam on the trans brake then creep in to light the second bulb. You could do that and eliminate a lot of extras if you went aftermarket efi. Are your 60' times where you want them?

- - - Updated - - -





Gregg is right on the money here.


I done it both ways. If I'm grudge racing I will go into the 1st beam on the TB. I f im T&T I will FB the 1st beam. I would like to get my 60's back down into the low 1.3s w/o the NOS. Right now they are around the low 1.4s.

Ordered the bump Box already. This will make staging easier and less jumpy. I'm going to lean her out more and move the 2 step to 4k. See how she reacts.

Thanks
 

droppedf100

Active member
Do you have any recent grudge runs you can post up? Nice to know at least one fast ford in the sea of Chevys down there.
 

rudder9

Active member
Slowly lean that transition area out and I think you'll see some pretty noticeable improvements. You'll get there. I can't tell you how much time we have spent on that area.
 

Modern Muscle

1000rwhp & 8 Second Club
I might be able to help answer some questions Terry, as I help tune Scott's (Rudder9 brother) car. You need more timing down low while building boost. Try 32-36 down low while building boost and don't pull any timing till about 4 psi. Air fuel should be in high 12s, low 13s while building boost. As everyone has pointed out, the two step cutting ignition will show lean on the WB. Then pull timing and add fuel at launch rpm. Didn't know you where running a PMS. That's impressive you got it running so good with the PMS. FAST XFI would make your life even easier :D Feel free to PM me with any questions.
 

T Hogg

Member
I might be able to help answer some questions Terry, as I help tune Scott's (Rudder9 brother) car. You need more timing down low while building boost. Try 32-36 down low while building boost and don't pull any timing till about 4 psi. Air fuel should be in high 12s, low 13s while building boost. As everyone has pointed out, the two step cutting ignition will show lean on the WB. Then pull timing and add fuel at launch rpm. Didn't know you where running a PMS. That's impressive you got it running so good with the PMS. FAST XFI would make your life even easier :D Feel free to PM me with any questions.

Looks like my timing is on point with what you suggested. Took her to the track last Friday and worked only on TB 60' launches. Started out at 1.54 @10#'s and by my 3rd hit I was at 1.41's @10 #'s. So then got a little excited and hit the that 100 shot with the 10#s and she reached for the moon, came down and was off to the races until the 3rd stage boost came in ripped all the teeth off the gears. So now I'm looking for a 8.8 3.55 Pro gear which no one makes. Looks like a it will have to be a Richmond 3.70 Pro gear.

The PMS has been good to me and easy to tune with. But I do feel I'm leaving some HP on the table by not switching to a better tuner. Every day I'm getting closer to switching to that new Holly system. Just lazy I guess. Hate to switch when the truck runs well with the PMS.

I'm going to PM you my number. Have a few more questions I would like to run by you. When you have time.

Thanks
 

T Hogg

Member
I might be able to help answer some questions Terry, as I help tune Scott's (Rudder9 brother) car. You need more timing down low while building boost. Try 32-36 down low while building boost and don't pull any timing till about 4 psi. Air fuel should be in high 12s, low 13s while building boost. As everyone has pointed out, the two step cutting ignition will show lean on the WB. Then pull timing and add fuel at launch rpm. Didn't know you where running a PMS. That's impressive you got it running so good with the PMS. FAST XFI would make your life even easier :D Feel free to PM me with any questions.

Can you send me the timing curve numbers you use at WOT from 4#'s - full boost and what fuel are using with those numbers?
817-822-0882 or I can send you an email if that's easier. Also did you every try out those front drag springs we talked about?
 
Top