I have changed my converter to a much much tighter unit due to driving throught the other one. I had no problems two stepping and bringing the car up on boost with the looser converter. Now with the tighter converter Ive ran into a new situation. I cannot brake torque the car with out it starting to stumble and sputter around 3000 rpm with this converter the only way I can get the car to come up on two step\boost is to flat foot the excelerator. But comes up extremely slow and has a very noticeable hesitation around that 3000 mark. It seems to happen right at the transition from vacuum to boost about 1.5lbs. Once it gets past that the motor pulls up the the 5200 chip and 12lbs of boost. I will be pro tree racing the car and by no means can do it with the current tune. The motor is a 397 cid Olds with twin 76mm Q trims and Seqential 160lb per hr injectors. Car did a 1.02 60 ft would like to see .980's. Any help is greatly appreciated !!! Thanks
Stumble with FAST
- Thread starter TD2593
- Start date
- Joined
- May 28, 2001
How much stall does the new converter have?
What does the EGT show at 3000 rpms?
My first guess would be to lean it out around that area. Especially if you are not into boost. Hotter gases make the turbos spool quicker.
Just dont kill the motor in the process.....
Twin 76s on a 397?
Wow
What does the EGT show at 3000 rpms?
My first guess would be to lean it out around that area. Especially if you are not into boost. Hotter gases make the turbos spool quicker.
Just dont kill the motor in the process.....
Twin 76s on a 397?
Wow
Ive leaned it in the area of the VE table that the stumble starts and makes it worse, Ive richened in the same area and makes it worse. Ive changed the AE vs Map and made it alot better but am lost. I feel it should brake torque smoothly and not have to flat foot it to get it up on boost. Im missing something. Car ran good at WOT. I need to beable to bring the RPM's up and bump into the lights before I lock the trans brake . Im not running an EGT
- Joined
- May 28, 2001
Can you send me the GCT file?
I can look at it for you.
I can look at it for you.
- Joined
- May 28, 2001
I noticed you have the O2 sensor set to kick in at 4250 ( not looking right at it ) .
You might want to try to set it at 2000 rpms and see what the sensor does for the stumble. Let it correct for it.
Where is the rev limiter coming in at? You said it was a two step?
You might want to try to set it at 2000 rpms and see what the sensor does for the stumble. Let it correct for it.
Where is the rev limiter coming in at? You said it was a two step?
Seem to have it worked out, I moved the cam sensor from 80* BTDC to 45* BTDC with no other changes the car revs clean on the TBrake all the way to the 2step. Brake torquing also is clean now. I also took a tip from Craig Smith and pulled out timing in the area of the two step and added more fuel and was able to gain more boost on the 2step as well. Converter is going to be abit too tight but atleast I can make a reasonalbe pass now. Thanks for your help Reggie. I appreciate it.
- Joined
- May 28, 2001
TD I am looking at your A/F tables and I am noticing just how rich that thing is. I would say you are about one full point across the board too rich. This is just a suggestion. I dont know, maybe you need that much fuel with 2 monster turbos and 397 cubic inches.
With the file you sent me you have the Closed Loop settings at 4500 to start and 6350 on the high end. Your RPM map goes out to 8250. I would suggest you set the sensor at 2000 and let it go to 8250. You may get some good insight as to what the motor needs.
I have seen a way to make a log of a run and then overlay the run on top of the VE table. Maybe Craig can elaborate on how to do that. I have seen it done on the dyno but I cant remember how to do it.
Last thing.. does that motor really idle at 1200 rpms?
FWIW if you are running rich and it is a little rough on the tune once you get it really dialed in this thing will be a bad ass ride from hades
I hope this helps you out some.
With the file you sent me you have the Closed Loop settings at 4500 to start and 6350 on the high end. Your RPM map goes out to 8250. I would suggest you set the sensor at 2000 and let it go to 8250. You may get some good insight as to what the motor needs.
I have seen a way to make a log of a run and then overlay the run on top of the VE table. Maybe Craig can elaborate on how to do that. I have seen it done on the dyno but I cant remember how to do it.
Last thing.. does that motor really idle at 1200 rpms?
FWIW if you are running rich and it is a little rough on the tune once you get it really dialed in this thing will be a bad ass ride from hades
I hope this helps you out some.
Craig Smith
That was easy!
- Joined
- May 25, 2001
Reggie, I suspect you have the concept of the closed loop settings backwards. If closed loop low is 4000 and closed loop high is 6350, it won't go into closed loop until you exceed 6350, and it will stay in closed loop until you go below 4000. The low and high settings don't define a window of operation.
- Joined
- May 28, 2001
Thanks Craig.
What about overlaying a log on the VE table?
The guy who helped us was using a FelPro version of CCom but I did not know if you can do it with a Windows based version of the software.
What about overlaying a log on the VE table?
The guy who helped us was using a FelPro version of CCom but I did not know if you can do it with a Windows based version of the software.
Typically when you hit the gas and the motor stumbles, that is related to AE. Have you played with the AE vs. TPS TD2593?
It sounds like the motor hestitates before it comes up to speed, a typical symptom of not enough AE vs. TPS. If you stab the pedal in neutral, will it stumble? Or will the RPMs shoot right up?
My understanding is that the AE vs. MAP is really there to compensate as the boost climbs, and from what you describe I'd be playing with the AE vs. TPS.
-Bob C.
It sounds like the motor hestitates before it comes up to speed, a typical symptom of not enough AE vs. TPS. If you stab the pedal in neutral, will it stumble? Or will the RPMs shoot right up?
My understanding is that the AE vs. MAP is really there to compensate as the boost climbs, and from what you describe I'd be playing with the AE vs. TPS.
-Bob C.
Craig Smith
That was easy!
- Joined
- May 25, 2001
AE vs. MAP should really only be used for throttle response below any substantial boost levels. Additional fuel for boost is handled by the speed/density calculation.
Thanks for all the tips guys. By moving the cam sync to 45 it revs smothly to the chip now. Before it would rev smoothly untill you put a load on the motor. The reason the wide band is set so high is due to the launch the car goes to 6200 as soon as it moves I didnt want any ocsillation in the AFR due to over under correction of the O2 too early off the chip. Converter is still on the tight side but now I can work with it and see what the car really needs for a converter. LOL Reggie Ive got it idled up to 1200 for the line pressure on the PG for the trans brake. It idles great at 800. Camshaft is 270/256 @ .050 on a 114. Next step is to work with the NOS function and pull out timing and add fuel and see if we cant get this thing to really BANG on the two step for more boost. Thanks again guys !!
Joe Lubrant
" The Right Stuff "
- Joined
- May 25, 2001
TD2593,
Another option would be you could still enable the 02 at a lower rpm, but disallow any+/- 02 corrections (A/F) in the rpm/boost areas of concern. (2-step area & flash)
Just a thought, works for most of the 7 & 8 sec. cars I have seen.
Joe
PT&E
219-996-7832
- Joined
- May 28, 2001
You have a good point about using the O2 below the rev limiter.
But I bet the VE map could be refined a lot and you would benefit from making a couple of runs with the O2 and datalog it.
That was the beauty of buying a system like this in the first place. You can datalog a great deal of inputs along with the O2 to see what the motor is really doing and make intelligent changes to the motor.
Keep us posted on how its going. That is a monster of a motor.
But I bet the VE map could be refined a lot and you would benefit from making a couple of runs with the O2 and datalog it.
That was the beauty of buying a system like this in the first place. You can datalog a great deal of inputs along with the O2 to see what the motor is really doing and make intelligent changes to the motor.
Keep us posted on how its going. That is a monster of a motor.
We were able to get the car out this past Friday for a little testing and the sputter problem is gone car feels really good, just need to work on getting boost up faster, looks like a looser converter is in the mix for sure. Thanks for all your suggestions it really helped out. We were able to run a 4.29 at 166 1/8th with a 1.000 60ft, car was really really moving around track was not good at all. that was the only pass we made decided to come back when track is better and then work on the tune up. Any of you guys got a special trick your using to get the boost to ramp faster with the tight converters ??? Im out on the track 200ft before I see over 20lbs.
