I am getting different opinions on this so I came here to see what people think. I had a Midwest 2800 stall and was running 12.2s-12.3s consistantly, while slightly spinning out of the hole on DRs. I decided to go with a custom 3600 stall which was built by a local guy that mimics the exact specs of a Yank SS3600. Well, since then, I haven't been able to get even into the 12.4s anymore, not even in good weather. I went last week and I ran 12.80s @ 106, time correction only dropped it into the low 12.6s, and I was hooking on ET streets. Anyway, I changed out the plugs and the fuel filter. Threw a scanner on it. The car misfires at RPMs just over idle and around 2000 RPMs while you have your foot slightly on the gas. At WOT, it knocks once in a blue moon. I don't know much about this stuff, but I have two people telling me two different things. One believes it is the tune that I had done, because he has the same converter and his is doing it. But, I talked to the guy who tuned my car and he says that is typical on a 3600 stall and you will have to live with it because of the positioning of the knock sensor. Also, at about 70 MPH, I am at about 2300 RPMs with my 3.42s, but when I start to go up a hill at any speed, the converter unlocks and, say at 70MPH with the cruise on, the RPMs are at almost 3000RPMs. Here is what I want:
1. Times like I had before.
2. The same driveablilty as I had before where the converter wouldn't unlock up hills, hurting gas mileage.
3. A car that runs RIGHT!!!

What is wrong? What needs to be done? Sorry for the as you can tell semi-technical post from someone not so technical (I'm learning so bear with me).

Thanks in advance!

 

Did you mean to type is or is not? I assume you mean is not. I know you've already heard from me also but I’ll add a few things to my opinion and I have a few questions.

First, is your car pinging as in you can hear it detonating? If so, that’s true spark knock and probably doesn’t have anything to do with the converter, although I personally would not have volunteered to be the guinea pig on that converter either. I’m pretty sure the converter can cause knock retard but not true spark knock. As you probably know, the knock sensors look for certain audible frequencies, which can be caused by a number of things including detonation, carbon build up, pipes banging, etc. All of which have the same results...KR. The PCM then pulls timing, which does affect your performance somewhat. How much is hard to say but in my opinion/experience it wouldn’t be four tenths, maybe one or two at the most. We’ll just have to see exactly how much KR you are getting and where in the rpm range it is occurring. One other thing to remember, you will lose some trap speed with the slicks/DOT slicks over DR's. You shouldn't lose ET though, especially if you were spinning on the DR's.

I personally think the tuning is the problem. I don’t know if the tuning was not done right or maybe it was but now you have an issue with the MAF readings. You know I’m not an expert by any means but from what I’ve learned over the past 5 years on ls1.com, ls1tech.com, CamaroZ28.com, working on my ’99 Z28 and now on my ’02 Z28, I can tell you I would bet money you have a significant tuning issue affecting the performance. I would not rule out the converter though. If all else fails, install a different converter and see what happens.

He is probably talking about false KR. I have not heard that that is a typical problem though.

Your transmission probably dropped from overdrive to third gear. In the heat of the summer your not going to be producing as much torque so the car may need to downshift. There may be more to it but imagine a V8 truck going up hill in overdrive with the cruise control on, say 70 like in your situation. Say in the cool of the fall or winter this truck makes it without needing to downshift. Now take that same type of truck but in a high mile V6 on a hot summer day, it probably needs to downshift to get up that hill and still maintain the speed that you set the cruise to. The summer heat can have the same type of effect even on your car, especially when you are relying on only 2300 rpms to maintain a speed of 70 mph going up a hill. You need more power to maintain that speed so the car is going to downshift to third. Does this make sense or is this not the type of problem you are having?

Hopefully some others here will chime in about all of this. I’d feel more confident in my opinions if others agreed.

See you tonight, check your PM’s on FAST

 

No, I can't hear it at all and neither can Dave.

I guess I shouldn't have said unlocked. It slips. It stays locked but the RPMs raise.

I am just so mad right now, I really can't describe it. But I'll be over right around 5:30 tonight with Dave so we can log some data and see exactly what is happening so if it is a tuning problem, I can present it to Keith.

 

Hmm… I’ll go for a ride with you so you can show me what it is doing. If it really is slipping, that is probably the main reason why you are running a lot slower. If so, get a freaking Yank and be done with that problem.

I wish I knew more about all of the different functions of EFILive. I have the professional version so we could actually make changes to the PCM but not permanently. but at least enough to try some things. Jason is coming over around 7:30 tonight and he actually knows a bit about air/fuel tuning. On a scale of 1 to 10, I’m only about a 3.5 when it comes to tuning so I won’t be too much help.

Charlie, don’t let it get to you, this stuff is the norm when it comes to drag racing. With all the resources we have today we’ll figure it out, it may hurt your wallet (as in a new converter?) but we’ll figure it out.

 

as information, except for the slower track times what you are describing as slippage is exactly what I feel since installing my PT4400 yesterday.
I had a tight feeling Midwest that did just as you said - stayed locked, pulled in part throttle conditions. The Yank flashes to about 4000 and the car catches up with the rpms.
I personally prefer the car to be in it's powerband like it is now, opposed to staying locked and needing me to either downshift or give more throttle.
I'd think tuning too, but my convertor threw the SES with a spark knock as well!! It does seem common that they are less able to keep the crank in balance and the PCM thinks things are knocking. I think my tuner broadened the requirement to sense the knock to avoid the SES light and actual timing retard. Now that I put the PT in, it threw the SES after weeks of no light driving the Midwest.
I'll know Saturday if the code is knock again but that's my guess. Nothing else hanged and the car is running great!
Good luck and please post your findings.

 

converter lock-up, downshifting.

From my experience daily driving mine 40+ miles on 270 and 44 when I was in school, I do not have a problem with the t/c unlocking or downshifting going up hill unless i get into it. I can still acclerate in 4th up a hill without it needing to downshift or unlock. My lockup speed is 38mph and if there wasn't any traffic I could pretty much drive all around town locked up in 4th at 45 mph if i babied the gas pedal.

I should of bought your Midwest, seems like a good driving converter.

 

Just to let everyone know, after throwing the car on EFILive last night, the tune is virtually perfect and the car is running as it should. But the converter was slipping hard. Lets say the motor was spinning at 5500RPMs, the converter was slipping so bad it was spinning at 4500RPMs. So the problem with my decreased performance is indeed my torque converter. Thanks for your replies. I'll be getting it taken care of and probably buying a REAL Yank SS3600 next week. Thanks to you especially Derrick!

 

I have questions, as my PT400 has caused similar issues with my car now that I've driven it 100 miles
1. the idle surges when coming to a stop.
2. the slippage seems exsessive - but how do I know how much it's slipping?
3. It threw SES codes
a. intermittant engine misfire
b. ranmission component slipping.

None of my other convertors did this....
was this like your problem?
How did you find your slippage rate??

 

The knock sensors go into the block under the intake manifold. I don not see how a converter swap effected that.

Did you change gears from 3.23 to 3.42s? Sometimes a gear swap confuses things. I know that after I went to 3.73s, I had to tinker with the tables to get downshifts and lock-up to occur where I expected them.

 

I did change to 3.42s, but about 3 months before I got the new 3600 stall. I have my stock stall in right now and she is running like a dream.