I'm lost. My 88 TA isn't performing as I hoped. I've made several trips to the strip, and cannot get the car to perform. Have an Procharger PSCH-1. Problem is, my best time is a 12.86 @ 97 mph. The car just dies when it hits 3rd gear. Cut a 1.87 60ft, running 87-88 mph @ the 1/8, then nothing! Only things that come to mind is the computer pulling out timing when boost climbs under the 3rd gear load, or I'm running too rich. I have a MSD BTM, but it doesn't seem to matter whether I boost reference the timing, or take it out completely. Running Big Tube runners, ported plenum, 24lb inj. 52mm TB, Big Mouth Base, Trick Flow TW heads, ZZ9 cam, 700R4, Vigilante converter, 373 rear gear. Tranny doesn't seem to be a problem......It's just dying in 3rd. Should be low 12's at least. Every LS1 I've come up against gets the crap scared out of them for the 1st 1/8, after that, they be laughing!!!

 

Sounds like your torque converter is locking. I had this problem too and couldn't figure it out for about one year. On some nights, I'd run low 12's and 105 mph. On others, I'd run low 12's and 115. Comparing time slips of each of these types of runs, I discovered that my numbers were almost identical at the 1/8-mile mark, so I knew it was only in the top end where I was losing some hp. My torque converter would lock up at around 80 - 85 mph, causing my top end to go south. At the 1/8th, I'd be almost at 90mph.

GM states that torque converters cannot lock up in WOT, but mine is the second 700R4 I know of that does and have heard of others doing the same.

Do you have a scanner? You can conclusively identify this problem with one, assuming it's the torque converter.

 

Willie; Thanks for your reply. I do have an AutoXray, but am fairly confident the torque converter is not locking up under WOT. I have it wired to do so, if I choose, and know the feeling. Checked out your SC Z. It's obvious you take great care and pride in your work. That's some beautiful work, even under neath. So I guess you can understand my woes. I'm running a 355. My suspension is stock, but as I said, my 60ft times are o.k. considering this. The car just feels like a slug when it hits 3rd. I notice you're running the superfueler. I'm wondering if my fmu is working properly, or working too well. It's kinda hard to diagnos all this, going down the track. By the time I figure it all out, the car will be all used up! Can too rich kill it as well?

 

I too can manually lock up my converter. The ironic thing is about one year ago before I knew what was happening, I flipped my manual lockup switch at the track at about 100mph. My rpm's did not drop as expected. I thought, "That's odd, maybe my switch isn't working." On my way home that night, I flipped the switch at a much lower rpm's and much lighter acceleration and it worked. Odd, I thought.

Just to make absolutely, positively sure that your converter is not locking up, try what I did. Flip your switch at WOT once in third gear and over at 90 mph. If your rpm's drop, then you know it's not locked. If it doesn't drop, well.... we've figured it out. I know on my car, locking up the converter in the above scenario drops the rpm's about 1,400, which is plenty to make my third gear feel like I'm driving my mini-van. It makes a world of a difference. I also know that manually locking a converter at WOT is not nearly as harsh a "feel" as when at light to moderate acceleration.

So before moving on to other things, I'd absolutely, positively rule this out first, not with only a certain degree of certainty, but 100 percent conclusively so.

Your FMU only "sees" boost. Any level boost in first and second gear would be the same as third gear, so I would rule out the FMU as malfunctioning. Also, if you're running super rich, you'll know by the trail of black smoke!

And I appreciate the compliments.

Willie

 

you mite be running out of fuel!? Your combo should rock..i'd think 11s fairly ez

 

I might like to add just a few cents here, depending on the year model and build of the 700r4 there can be two lock up valves one "connected" to the selenoid's operation and one in the valve body. Stroke of the valve in the valve body will cause lockup regardless of the selenoid condition. Also if a lock up selenoid is not operating properly and or is partially plugged it can perform as if it is commanding lockup. this lockup will sometimes not occur until TV pressure is low enough and govenor pressure is high enough. This lockup "inhibit" can be seen in some trannys by "flipping the switch" while in gear and stopped to see if the car dies. Some will die some wont and it doesnt mean anything is wrong. My point is that even with manual valve control lockup can be both inhibited and commanded without control of the electronics even though in some trannys and not others. When a trans go shift kit (and some others) is installed, a .380" ball is placed in between the lockup selenoid and the lock up valve retention plate orafice. this is done so that even if the lockup selenoid fails locked or unlocked the tranny will still lock and unlock as if nothing is wrong.

 

A recent development strengthens my hypothesis. I received the latest EPROM definition from Tuner Cat. There is a constant setting which I've never seen before. It is, "TCC Unlock Prevent / Auto O/D Engage Speed". Mine is set to 80 mph. My data from all previous runs at WOT show my converter locks up somewhere between 78 and 83 mph at WOT. I'm willing to bet this is the constant. I have seen changed it to 255 mph (maximum) but have not tested it yet.

Willie