Two races ago I took it to the semis and did a terrible job driving the stripe. Rolled it in the trailer without downloading the run. Last race I downloaded the run and the engine RPM has a big hump in it at the converter flash. I’ve never seen anything like this and all the other runs from the day lay over each other nicely like usual.

Last week I went 3 rounds and every run overlaid nicely, so the issue didn’t present again.

The weather conditions were pretty nasty, 89 degrees, 112 water grains, 3550 DA. The semi was run about 30 minutes after the quarterfinal so not a crazy hot lap. I do have trans temp gauge but never looked at it since it’s shared with engine temp gauge and I never flipped the switch.

These two runs are the quarterfinal and semi. In the quarterfinal as with all the other rounds it flashed right at 6300. In the semi it went almost to 6600, there’s a 342 RPM difference in the spot on the run I have highlighted, .36 in. The converter is a spragless FTI.

The crazy thing is the time slip was only .002 different in 60’ from the previous round and the rest of the numbers were close too. Actually the numbers in the semi were closer to the fourth round, the quarterfinal was about .01 slower than 4th round and semi.


Anyone see something like this before?

Link to graphs

Trans Temp got very Hot, changes the viscosity of the fluid. Which in turn raises the stall speed.

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Driveshaft graph tells you it spins a little there comparatively.

Looks like the yellow driveshaft graph goes with the blue engine rpm graph.

Yellow and blue do go together. On my link at the top the RPMs and colors are there.

I don’t believe the slight spin to be worth 300 engine RPM even if the yellow driveshaft went with the red engine graph.

This message has been edited. Last edited by: 183N,

"Comparatively", You'd think it would only do it once (slip the band in low gear) but I'd count the turns to 72 inch pounds on the band to eliminate it as a variable. Should be 3.5 turns. Compare your flat driveshaft problem E5 run to other driveshafts.

quote:

Originally posted by 183N:
Yellow and blue do go together. On my link at the top the RPMs and colors are there.

I don’t believe the slight spin to be worth 300 engine RPM even if the yellow driveshaft went with the red engine graph.

It won't be. You might right click on the field and mark data points just to make sure it didn't throw up an errant data point. It looks pretty smooth though so I doubt that is the issue. Worth looking at though.

With 30 minutes between rounds but at only 89° ambient temp I would be surprised if trans temps were it unless they were above 240° but with that said anything is possible.

Mike if it slipped the band I couldn’t imagine it would lock back up and follow the other run like it did, and ET about the same ??

Curtis I went through the same thought process of errant data point. But it has more voltage, oil pressure, and fuel pressure on my belt driven pump so that graph is what actually happened. Errant data points are usually straight up or down on the graph then back right away.

quote:

Originally posted by 183N:
Mike if it slipped the band I couldn’t imagine it would lock back up and follow the other run like it did, and ET about the same ??

I'd count the turns on the band to 72 inch pounds to rule the band out of the equation. If I'm reading this right it has done this twice. The only way I can see for that to happen is if the transmission has a stock band. A stock band will work real good, I use them myself. They work well up until they start digging chunks out of the drum. I could see it slip the band a handful of times plus or minus and not lose anything in ET with a stock band chewing the drum, it wouldn't even be noticeable in the seat 300 rpms. First thing to do is count the turns to 72 in pds. Should be 3.5 turns. I can't see it being the converter but anything is possible.

Not sure I wouldn't chalk it up to one of those things unless you start seeing it more. Like you said it really didn't affect much.

Curtis

quote:

Originally posted by CURTIS REED:
Not sure I wouldn't chalk it up to one of those things unless you start seeing it more. Like you said it really didn't affect much.

Curtis

Agree x 1000. Data is good, but sometimes we know and see too much about our cars that really doesn't matter.

OP, do you log converter pressure off the out cooler line? Maybe the oil is crawling the back of the pan uncovering the pickup intermittently. A loss of converter pressure would make the converter stall higher. Spragless converter the stator is splined through a sleeve to the stator tube. I'm sure it's a steel stator so there's nothing to malfunction intermittent such as with a one way clutch/sprag type converter. Pressure could do it though.

Curtis it could be a bit of data logger itis- I wouldn’t know there is a problem if I didn’t have a logger. But this is one reason I have a logger, to spot problems before they bite me and this is WAY different than anything I’ve seen ever with this combination. It’s telling me something and I’m sure I’ll find out what it is sooner or later. Hopefully not by blowing up a bunch of stuff.

Mike this only happened one time, in the semis. Raced it since then and it was good. All other runs that day and after look like the other run in the graph.

Not sure what band is in it but the trans is fresh this year and the band was replaced. About 60 runs ago.

Don’t log converter charge pressure.

Oh I get it. I do the same thing sometimes having my logger. LOL I will see something from time to time and I wonder what the heck is going on and it doesn’t change anything on track but I still worry about it.

You’re right they absolutely will help you find problems. My car fell off .035 one run out of the blue and I saw my vacuum had gone positive. Lost the belt off my pump. Put another on and right back where it should have been next run. Good reason to carry.

Bringing this thread back from the dead because I think I found the issue.

After my post I talked to FTI and they hadn’t seen anything like it. I raced the car twice and the issue presented itself sooner and sooner in the race day. At the bracket finals my graph started looking weird on the second run and by the fourth round it looked very similar to the graphs I posted in this thread. Actionracingphotos beat me in the 5th round in a good race.

Was talking to a guy at the bracket finals and he recommended changing the transmission fluid. His thought was nothing mechanically is broken, it acts right next time you race it, maybe the fluid is broken down. It had Amalie dex 3 in it. I changed to the FTI fluid and have raced the car twice and haven’t seen the issue at all. I don’t have enough runs to say for sure that it’s fixed, but I think it is.

Good find if the problem stays away.

You might laugh but I put Valvoline Max life multi vehicle ($18 a gallon at Walmart) when I went to high gear only because I was going to change the transmission fluid with the oil. I ended up going the whole season putting 200ish runs total on the fluid.