Power logger file, converter slip questions, tuning recomendations

[Evaddave 87gn]

General info leading up to this particular run:

This past spring (2017) I finally spent some time working on issues with my car. I replaced the wastegate that was preventing me from running under 25lbs boost. I fixed a ground issue that was affecting the Maftpro from adjusting the timing. I also set the Maftpro to control boost and timing based on the gear I was in.

Next I started to level out my A/F ratio pulling fuel from my main scale, but I never finished my adjustments before life happened and I stopped going to the track in 2017.

This is the third and last run of the night. On this particular night I was verifying the timing and boost were correcting as I wanted, they were. So on this last run I added a couple psi and left the A/F and timing alone.

My hand logs say I ran 11.21 at 121mph with a 1.745 60'.

Spring 2018 plans:

This winter I am making some changes to the rear suspension, as think I will be able to start to work on my 60' time this spring. I really think I am getting close on my main scale adjustments, so I hope to focus on first and second by adding timing and pulling fuel down low.

Open to any tuning comments. Always willing to learn from others!

Converter questions:

I used the Powerlogger to take a look at my CS% and I could use some advice. I have very little experience with CS.

What should I see when the converter is locked at WOT? 0% or is under 5% acceptable?

I am seeing slip near 39% at times, it this just lost power?.

How does CS effect tires breaking loose at launch?

I am hoping to get 60' below 1.6 or lower, but I am wondering if the current converter will make it difficult.

Any input or advice is appreciated!

 

[SCOOBY DOO]

Looking at the log I think I know the answer. Did you lock the convertor in 3rd? Are you running a 26 or 28 inch rear tire?

 

[Evaddave 87gn]

Looking at the log I think I know the answer. Did you lock the convertor in 3rd? Are you running a 26 or 28 inch rear tire?

Thanks for responding!

Yes, I locked the converter at the top of third. I think it was set at 90 or 95 but I would have to look at the file to be certain. It drops 600 rpm. The speed seemed to continue to ramp at same rate.

28" drag radial.

 

[SCOOBY DOO]

WOT in OD isn't a good idea...throws a helluva load on the engine. We race these cars in 3rd...with the convertor locked somewhere in 3rd. I use to have Eric lock my convertors for me via his chip...but I can't remember the MPH. I run NL convertors exclusively.

 

[SCOOBY DOO]

I use the Wallace Race Calculators. Ask Eric the MPH he uses to lock the convertor. You can hook an ashtray switch up inexpensively and throw it partway in 3rd...or where the other guys are locking it.

http://www.wallaceracing.com/Calculators.htm

 

[Evaddave 87gn]

WOT in OD isn't a good idea...throws a helluva load on the engine. We race these cars in 3rd...with the convertor locked somewhere in 3rd. I use to have Eric lock my convertors for me via his chip...but I can't remember the MPH. I run NL convertors exclusively.

Sorry but I was not clear on my response. I was in third when I locked the converter at 90/95 mph. As soon as the converter locks I get the rpm drop, this is not a shift to fourth. I never went into OD (4th gear).

 

[SCOOBY DOO]

Sorry but I was not clear on my response. I was in third when I locked the converter at 90/95 mph. As soon as the converter locks I get the rpm drop, this is not a shift to fourth. I never went into OD (4th gear).

My bad.

Sorry but I was not clear on my response. I was in third when I locked the converter at 90/95 mph. As soon as the converter locks I get the rpm drop, this is not a shift to fourth. I never went into OD (4th gear).

My bad. Looked to be late in 3rd...so I assumed OD. Find out when the guys are locking it. I thot Eric locked mine earlier...but I could be wrong. Haven't run a LU in a long time. Grumpy went 9.98 at 138 with a 9/11. I don't have the slip numbers...but the MPH tells me it's pretty efficient.

 

[hensleyt]

I run a Edge converter and Lonnie at Extreme automatics recommended I lock mine at 85.It never goes to 0 slip on the PL.I drop about 400RPM I called Edge and he said it would be ok.Your making more power than I,but it just adds 1 or 2 mph to my time slip.ET is in the 60 ft times more than the top of the track.And I'm to close to being booted with no bar.
Dose locking yours add ET and MPH at HP?

 

[Evaddave 87gn]

2017 was the first year I started to focus on tuning with the Maftpro, it was also the first year I locked the converter at wot. I made so many changes in early 17 that my slips dropped from a consistent 11.5 range to 11.2 range without race fuel. I am certain locking the converter is adding to mph and reducing my ET. How much I cannot say. When it locks it feels like it is pulling hard, very hard and the tune still has a ways to go.

I set the lockup around 90 since I was reaching my rpm shift point that I have in 1-2 and 2-3 at that speed. Not sure if this was right or not, just seemed logical. Maybe I should be locking it sooner.

 

[Evaddave 87gn]

TTT

 

[Charles Young]

Like the OP I have little experience evaluating CS. Actually I just realized I can look at it on Powerlogger and am looking back at some files and would appreciate some feedback. I have a 5.7 TT chip and a 2800 (?) stall Vigilante converter. I'm running 255/60/15 DR's and have only made the 3rd and 4th gear CS factor adjustments in PL using 46.5 and 31 respectively and no separate correction for tire size. For now, what I am seeing seems like a lot of slip and no lock up in third gear. On several 1/8 mile runs from last year the data look about the same as follows: PL shows no CS in 2nd gear. Immediately after the shift to 3rd (about 62 mph) CS is about 80% and continues to go down to about 24% at the end of the run (about 85 mph, 3rd gear).
Questions:
- Do I need to make a tire size correction? If so, I can do that and report back.
- Are the 3rd and 4th gear CS factor adjustments OK?
- With my chip, shouldn't the converter lock somewhere in 3rd or am I not fast enough?
- Don't the slip numbers look real high???

Thanks for any feedback!

 

[SCOOBY DOO]

For racing...you have to ask Eric to lock it in 3rd gear for you.

 

[SCOOBY DOO]

Charles...plug your data in here...http://www.wallaceracing.com/converter-slip.php

 

[Charles Young]

Thanks Scooby Doo - Based on the Wallace calculator, assuming an 85" circumference tire, it shows about 27% CS; not far off from the PL calc.
High??

 

[SCOOBY DOO]

A good convertor should be in the single digits. One of the locals was at the track with me...and couldn't get the car past 112 mph. Convertor was slipping 22 percent. You can make all the HP in the world...but if the convertor can't get it to the back wheels...then the games over.

 

[Charles Young]

I wonder if my slip was say 9% how much diff it would be in the 1/8th? Any ideas? Maybe time to call Dave...


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[SCOOBY DOO]

I wonder if my slip was say 9% how much diff it would be in the 1/8th? Any ideas? Maybe time to call Dave...


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I'd tell you to go with a PTC race convertor. If you have to go LU I have a real world result with one of the locals with Daves 3021. Old skool 60 series turbo...bone stock long block...3" DP...aftermarket exhaust...Julios alky...TT alky chip...26 PSI. 11.4 at 117. Pretty decent for an unlocked convertor.

 

[Nigel]

You want a convertor that provides adequate stall at the line and does not slip excessively at the big end. A torque converter acts like a gear reduction, a fluid coupling is going to act more like a clutch. Off the line a convertor will multiply torque, but this requires the engine to run at a higher rpm(better be in the fat part of the power for this to be effective) than the output shaft, and the power that the engine is making is converted to torque. As the wheel speed increases instead of converting power to torque, the slip is loss of efficiency. A fluid coupling does not multiply torque, but couples very well when the output shaft speed starts to come close to matching input shaft speed. So the summary is a torque convertor can help 60ft but may kill trap speed and hamper ET by causing the engine to operate out of its best rpm range if the stall is too high. With higher horsepower, torque multiplication is less important than operating in the optimal rpm range through out the run. So the converter should operate more like a fluid coupling. The ideal scenario would be if the engine hit the power peak and sat there through the entire run, not quite a reality at this point unless somebody has data to say otherwise.

You have to get the power logger speed correction and CS factors correct to measure slip. So far the best slip numbers I have seen are the PTC NLU converters based on what has been posted in the past. The convertor is a critical piece that still gets overlooked. High stall, wheel spinning, and seat of the pants is not the way to judge. ET and trap speed will tell the tale.

 

[Charles Young]

Thanks again Scooby Doo! So you are thinking my slip is pretty high?
Also, at the end of your post above you reference an unlocked converter. Aren't Daves 3021's LU?
Probably a loaded question but why do you r commend PTC race?


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[Charles Young]

Thanks Nigel; very informative!


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