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2step - Building more boost at the drags

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I finally got to test my new setup last weekend at the drags, managed a 10.140 @ 139mph with a 1.690 60ft.

Leaving the line at 4200rpm making 17psi, it grips up and takes off no worries, no wheel spin

I would like to change my launch control to make it launch harder, around 22psi even more if possible but unsure on how or what to adjust to make it do it

Specs of vehicle below

built 1jz (2.5lt)

2speed powerglide

4000rpm stall converter

garrett GTW3664r

water/meth injection (turns on at 1bar)

Link G4

Is it true that automatics can't have as much timing retard compare to a manual car?

I have attached the tune & data log, any help would be great or information for me to understand whats going on and how to make more boost, is it a matter of more RPM, more/less timing, more fuel, more wastegate duty cycle?

Will more RPM play on the stall converter?

I had a play around with changing the timing today, each time coming stuck and not making more then 17/18psi so I am not doing something right here


Attached Files

i would suggest something like the settings i have changed to

in the attached file

Regards Ross

Attached Files

Hi Ross

I will give it a try tomorrow and let you know what it does

Does the wastegate dc play a part in getting more boost on 2step, could that also be a limiting factor ?

Thanks for the speedy reply!

I think you will also need to bring the launch RPM down to get effective 2 step. Your converter is starting to drag pretty hard by 3500RPM and looks like it is fully stalled by 4200 so with your limiter set at 4500 you are only just kissing the limiter occasionally and dropping back out of the limiter range. I think it will need to be in the 4000-4200 ballpark for this converter.

Morning Adam & Ross

Uploaded the test file, but took Adams advice and set the limiter from 4500rpm to 4200rpm

Have uploaded my log, boost is on the right track, but I backed out as it was climbing heaps..What numbers do I change to bring it back to a steady 22 odd psi?


Attached Files

Yes the boost controller does have an effect on the boost during launch control so setting up a 2nd table for this will help but normally the retard will do most of the work so more Reese’s creates more boost and vis versa

regards Ross Honnor.

Hi Ross

So the launch ignition trim is currently at -20deg, so changing this to -10 I should see less boost on limiter?

Do you also think leaving the launch RPM at 4200 from 4500 is ok from what Adam suggested?

I guess some more trial and error at the track will help with launch RPM if it blows the tyres


So just done another test after letting it cool down from this morning

Worked well, just made an almighty bang from exhaust, so I backed off in the video

So far is this on the right track?

What was I doing wrong in my tune file?

Was the massive backfire the car hitting the 4200RPM launch?

Video of this log - [url=https://www.youtube.com/watch?v=iEyYD7gTbKk]https://www.youtube.com/watch?v=iEyYD7gTbKk


Attached Files
  • 24PSI_-20IGNTRIMLog-2020-08-4-15423-pm.llg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

Its still not even hitting the limiter in those logs. The retard is kicking in but not the limiter. The bang at the end is the one time it hit the limiter - it should be banging like that the whole time.

Try it with the launch ign backed off to -10 absolute and ign trim activation raised up to 4000. I think you may need to drop the Start cut (TP100) back a bit too but try those first two changes first.

Have made the changes you requested

Video - [url=https://www.youtube.com/watch?v=u7Zbzcm6MNw]https://www.youtube.com/watch?v=u7Zbzcm6MNw

Log attached

Attached Files

Can I get your current tune, Ill make some adjustments. As suspected that start cut is too high but I also want to make a couple of other changes to get you closer quicker.

Hi Adam

Tune file attached of what I tested this morning

Quite morning at work for me today

thank you

Attached Files
  • 03_08_20-Deo_Tune-ross-suggestion4200_-10.pclr
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

Ok, try this. I have brought the launch RPM down further so we can concentrate on getting the limiting action better with less influence from the convertor. You may be able to bump it back up once we have some more consistent limiting. You can use the file compare function to highlight what I changed.

Attached Files

Getting there by the sounds of what it did

log attached

Attached Files

Hmm, I stuffed up the ign trim in that one but its still needing very little limiter to hold it back. I suspect this converter is a bit tighter than Im used to.

I was trying to aim for spark around TDC and forgot 0 ignition trim disables it. So, another couple of small adjustments.

Attached Files

Another test done, log attached stable 11psi

Yes stall converter is tight for 4000rpm..?

Attached Files

Getting closer.

Attached Files

struggled to get onto limiter

so I backed out

not sure what happened there

Attached Files

Yeah, its the converter coming in too early for the turbo size I think. The converter starts to bite pretty hard about 2800, and by 3600 it is absorbing all the torque the engine can produce. So as soon as we add cut or retard to make more heat you lose torque and the RPM falls below the activation. If you could get the engine to make more boost at 3500 then torque would increase and the RPM will flare a little more but it seems you are sitting right on the point where there is not enough airflow at that low RPM to get it all happy. You can try bringing the launch RPM and ign activation RPM down a little lower but I think we are already getting lower than ideal for a set up like this.

So what can I do to fix this issue?

Looser converter

That's my feeling. I dont have a wide experience pool with auto drag cars to draw from, but from the experience I do have and the last few logs above I think your turbo is happier up around the 4200-4500 ballpark, so you need the stall up around that level or a little higher. Obviously there's a lot of guess work with converters as the builder needs to estimate how much torque the engine is making at or near the planned stall RPM. When you have something common like a SBC they get it right first time, but less common applications will often need some tweaks to get the converter working well with everything else.

I'd still try bringing that launch activation down a bit but I dont think it is going to make any boost.

So I don't understand how when I uploaded the launch tune file from Ross, it made 26psi easy...

I called Domanator, they can loosen the converter for me but then this could cause problems at full track and reaching my engine RPM limit, as at the moment I am crossing the line at 8100RPM, making the converter more loose could see that I hit the engine RPM limit, and I could possibly have to change diff gears..

Just wish I could get my head around it easier, thanks for your efforts this morning Adam

Launch control wasnt even working in either of the logs you done with Ross's settings as the RPM never even reached the activation point. It was just sitting against the converter, there was some retard bouncing on/off which probably helped but no 2 step.

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