2G GSX Auto brake boosting problems.

[Kdouglas89]

Hello guys, gonna give basic run down of relevant mods followed by the question. My profile is updated with a complete list, just naming only things relevant.

Built supertech head with HKS 272
Stock block
Stock tranny
Ported 16G, 1250 injectors, on 255
Dsmlink
Speed density
Running E85 on bpr7eix i think is the number.


I am unable to build more than 2lbs of boost at 2400RPM on stock converter at the line. My AFR is 13.2 during brake boost. Have been advised to drop it down to mid 12's, and swap my plugs to copper br6's.

Having a big debate between other DSM'ers about if I will have to swap out my converter to be able to build 10-15lbs off the time.

Have also tried to retard timing off the line to like 12 or so. I was unable to build boost after the change. Have been told retarding timing for a 16g would not do anything.

 

[91stocker]

Having a big debate between other DSM'ers about if I will have to swap out my converter to be able to build 10-15lbs off the time.

First of all, i wouldnt ask those "dms'ers" for advice anymore. You can spool up a hx35 on a stock converter. A 16g is no sweat.

I am unable to build more than 2lbs of boost at 2400RPM on stock converter at the line. My AFR is 13.2 during brake boost. Have been advised to drop it down to mid 12's, and swap my plugs to copper br6's.

Have also tried to retard timing off the line to like 12 or so. I was unable to build boost after the change. Have been told retarding timing for a 16g would not do anything.

Have you checked for boost leaks? Likely multiple leaks.

 

[Kdouglas89]

No boost leaks, hold 25psi fine from compressor, also no dropoff on log.

 

[bo0st]

No boost leaks, hold 25psi fine from compressor, also no dropoff on log.

Post a log for us to take a look at.

 

[Kdouglas89]

Post a log for us to take a look at.

Posted. This was my last run.

***I start brake boosting at around 23 seconds.

 

[Kdouglas89]

Bump

 

[Chumpaumpalumpa]

Around 37 seconds you are 100% throttle yet the RPMs drop off. Were you braking or something? You might have a huge exhaust leak somewhere. Also check turbo for shaft play.

 

[Kdouglas89]

Around 37 seconds you are 100% throttle yet the RPMs drop off. Were you braking or something? You might have a huge exhaust leak somewhere. Also check turbo for shaft play.

Not sure what you mean? At 37 seconds I let off the throttle. This is an 1/8th mile track.

There is no exhaust leak. After fresh rebuild, smoke only came out of exhaust tips. Tried to tighten down bolts after a heat cycle, and was still good. Turbo is in perfect shape, no up and down, or in and out.

 

[Chumpaumpalumpa]

From 37-38 seconds on the log it shows TPS at 100% meanwhile the RPM drops. Maybe it's just a logging issue. I'd encourage another BLT especially if you've taken any intake stuff apart since the last one or even better do a smoke test if you happen to have a tester.

 

[bigdnno98]

Could the drop in RPMs have been a shift?

 

[Kdouglas89]

^ That was shifting from 2nd to 3rd "Auto trans remember".

 

[Chumpaumpalumpa]

Durrr sorry guys I'm totally out of it today. That makes more sense than whatever the hell I was thinking. Anyways you could retard timing and add fuel at that RPM. I assume you're not driving through the brakes?

 

[Kdouglas89]

No problem man hah! I am not driving through the brakes. I get to roughly 2400 rpms before it won't climb any higher. That builds around 2-3psi. I found today that my transfluid is pretty low while in gear. Gonna fill it tomorrow. Will also be messing with the tune tomorrow, will keep this thread updated.

Thanks!
Kevin

 

[Chumpaumpalumpa]

Great to hear. Definitely post a log of retarded timing and enriched fuel there and/or maybe use the anti-lag function. You could try something like what I attached if it makes sense to you. I haven't done anything for an auto as far as launch control but I read a bunch of stuff where people were having the same problem as you and something similar to this seemed to work well for them as far as the anti-lag option just to retard timing under launch conditions without affecting normal driving. Might want to play with the timing and fuel enrichment though.

 

[91stocker]

I wouldnt go messing with the tune just yet. Maybe add some fuel and bring that afr down to mid-high 11's vs the 13.2 you're seeing now. But if you cant spool up a 16g on a "stockish" tune then theres something definitely wrong.

When i had a similar issue on my red 1g i found the IM was leaking and had a pretty heavy leak between the exhaust manifold and the head.

Im still betting on there being a leak somewhere.

You need torque to get up on the converter. Your car isnt making any so i wouldnt pull timing. It should be trying to rip through the breaks. It should also build what ever that 16g will make on the breaks as well, as long as the breaks can hold it back.

 

[pimpy rider]

i dont know anything about autos so i have no business posting here, but is it possible there is sonething wrong with the converter? worn out, slipping, not allowing you to boost more?

 

[Chumpaumpalumpa]

I agree with stocker up there I think there is still a leak, and even with no shaft play, spin it to see if it sticks at all. Does boost stay steady after you're already moving?

 

[bigdnno98]

boost is steady once moving.

 

[bigdnno98]

I don't think a factory AT car can use anti-lag can it? Since there's no clutch switch?

 

[gofer]

I don't think a factory AT car can use anti-lag can it? Since there's no clutch switch?

Sure you can...

Using Clutch Cut to Launch Auto works awesome

 

[bigdnno98]

Sure you can...

Using Clutch Cut to Launch Auto works awesome

Thanks for that!

I agree though that anti-lag shouldn't be needed to spool a 16g at the line on an AT. I would expect 15-16psi while on the converter.

 

[Chumpaumpalumpa]

Thanks for that!

I agree though that anti-lag shouldn't be needed to spool a 16g at the line on an AT. I would expect 15-16psi while on the converter.

You're absolutely right. Which is why it is likely that there is some other problem. A leak at the manifold perhaps? People have gotten 20 on the 16G, so 2-3 means there is definitely a problem somewhere.

 

[4cefedgsx]

This may be a dumb question, as i am on mobile mode and cannot open ur log file. But, is there a possibility that the wastegate is hanging open just enough to prevent low rpm/low load boost? Possibly pull the actuator arm off the flap and make sure once removed the flapper isnt able to close anymore?

 

[Kdouglas89]

This may be a dumb question, as i am on mobile mode and cannot open ur log file. But, is there a possibility that the wastegate is hanging open just enough to prevent low rpm/low load boost? Possibly pull the actuator arm off the flap and make sure once removed the flapper isnt able to close anymore?

Sorry for such late response. Have not been able to do much with the car. Hood flew up on track about 3 weeks ago, smashing windshield . Getting replaced tomorrow. Bigdnno above mentioned that to me the other day, and it could be a possibility? I am still on internal wastegate. Would pulling the arm off allow me to test to see if that's the issue?

Kevin

 

[hotrodssnova]

Only if you immobilized it. It will need to be wired closed so it can't move.