Dynamometer Results & Comparisons - what could be the problem with locking a stall on a dyno run?

I see people with locked dyno runs all the time, and I cant figure out why it could be a problem, but Ive been told (or really a friend has been told) that its not good for the trans and the locked #s arent real world. this would be for a 4L60E Im wondering about.

now I have a 700r4 in my 95 (its out of a 3rd gen) and I have a manual lockup switch and plan on testing with it on and off. I use it on the freeway (seems to be good for about 250-300rpm on my 3800 stall) and at the track, but I need a shift kit cause I dont think it locks under WOT with out the shift kit.
I know the GN guys have been doin this forever and gain alot of MPH from it at the track. so why dont 4L60E guys run a lockup switch for track times?

so why dont 4L60E guys run a lockup switch for track times?


I do. I pick up 2 extra MPH out the end when locking my converter. You have to be somewhat scientific about it though and not just lock it up when you feel like it during a run. Go to a dyno and get a dyno pull locked and then unlocked. There will be an exact MPH where the curves cross. That's where you lock the converter up for the maximum gain from doing this. Try it.
BTW on my stock longblock bolt-on motor this point was 84.4 MPH with 3.90 gears and PT4000 converter. I've yet to find out where this point is with my new head/cam combo but you can count on me getting this information.

The curves cross at 5250, so just log and look to see what MPH you are at.... although I'm not sure what gear he is locking it up in; from the MPH I'm guessing 2nd?

whats the whole idea about locking the conv. at the cross over point? cant figure out on my own what the bene of that would be. obviously, you dont want to lock it in first gear (700r4's cant physically anyways due to the port in the valve body being blocked in first gear) cause you'd lose all torque multi. from the stall, but once in sec. I cant figure out any benefit to waiting to a certain MPH. please explain.

so can anyone point to anything neg. about locking on the dyno?


Frost, just read your thread about your car build. I must say VERY SWEET. Im sure you are enjoying that car with your setup. what kind of track times you seeing now, and whats the boost up to? and what the hell happened to your oil pump oring? was it cut from someone jamming the pipe into the pump? cant figure out how that happened while assembleing the eng. on a stand. anyways cool story and thanks for all the pics and story.

chris

so can anyone point to anything neg. about locking on the dyno?


Frost, just read your thread about your car build. I must say VERY SWEET. Im sure you are enjoying that car with your setup. what kind of track times you seeing now, and whats the boost up to? and what the hell happened to your oil pump oring? was it cut from someone jamming the pipe into the pump? cant figure out how that happened while assembleing the eng. on a stand. anyways cool story and thanks for all the pics and story.

chris

As far as locking it on the dyno, I guess it depends on a number of things... Is the converter MADE to lockup under load? If it slips at all really it's just going to unlock in most cases.

...there wasn't an o-ring problem, either a new comp OE lifter failed and wiped a lobe, leading to eating a bearing, or the bearing went and the trash stopped a roller on the lifter. Either way, same outcome. I am running 15.5psi with methanol on the HPE shortblock with TEA heads and it feels NICE :chug: I've been at this level for about 900ish miles. I don't know how quick it is yet, it hasn't been on the track, but I was dead even with a new C6 Z06 for 3 pulls from second gear to the top of fourth when I was at about 9psi, and it's a whole different animal at 15psi :judge: The turbo brings the luxury of a tall rear end gear, so the M6 is coming out for the th400 and a 3.08 gear with a hefty but tight stall. I hope to be on the track by May with it. Thanks for the intrest :)

I think you guys missed what he was saying about the cross over. He is not talking about the TQ/HP cross over. He is probably looking at the TQ of both unlocked/locked runs (or HP of both, not sure), over laying them to see where the cross over is. Locking it there.

There is nothing but advantages by locking up the converter to better anaylize just engine mod comparisons assuming that you have a TCC that will not slip and you always do your comparisons this way. Unless you do HP comparisons by MPH rather then RPM, an unlocked slipping converter's reading can be very misleading, especially trying to analyze different stalls. If you are troubleshooting your converter, TCC or complete drivetrain, then it's a different story.

As far as locking the converter during a race, using the fact that it's he who can average the most HP in each gear will be quicker all else equal, find at what RPM your engine HP peaks, then lock the converter so that your RPM drops and crosses that point again, like another gear. Another way to look at it, if we had an infinate ratio transmission and a joy stick to control it, we would hold the RPM at the peak HP RPM point throughout the entire race, this is what we are crudely trying to accomplish with the TCC lock up.

I think you guys missed what he was saying about the cross over. He is not talking about the TQ/HP cross over. He is probably looking at the TQ of both unlocked/locked runs (or HP of both, not sure), over laying them to see where the cross over is. Locking it there.

This is it exactly. Overlay the horsepower curves locked vs unlocked using a MPH scale. Where the locked curve crosses the unlocked is where you lock it up in Drive for maximum gain at the track. Locking it up in 2nd drags the motor down too far when you shift into Drive. I know, I've tried this as well.
Try this, it works.

what MPH was yours at? just curious. your talking about lettting the car automatically shift, but at the given mph, say 68mph, lock the conv. for the remainder of the run right?

what MPH was yours at? just curious. your talking about lettting the car automatically shift, but at the given mph, say 68mph, lock the conv. for the remainder of the run right?
This is exactly what I'm talking about. With my bolt-on engine combo it occurred at 84.4 MPH in Drive. What surprised me was how low of an RPM this actually was. It was just under 4100 RPM where the curves crossed when it was plotted by RPM and not MPH. It sounded like it dragged the motor down way too far when you actually did it but the dyno curves and the track MPH traps don't like. I actually have a full manual valve body in my transmission so I can't let the car automatically shift. However, even if you let yours shift automatically the same principle applies. If you don't have a dyno to test this I can't imagine getting much, if any gain from doing this though. If you lock it too early, say 68 MPH in your theoretical example, it'll drag the motor down too far and slow you down. If you wait too late you won't have the benefit of the added horsepower long enough to make an appreciable difference. Get to the dyno and plot the horsepower curves locked vs unlocked. Lock the converter where they cross in Drive.

what trans do you have? 60E? I wasnt aware they made a man. valve body for the 60E yet? as for me, Im using a 700r4, and manually shifting it (b&m hammer ratchet shifter) cause I like to shift it. been thinking of doin a manual valve body in the car, just havent had the nerve/money to yet. no question when I get around to working on my Iroc again that will have a manual valve body in it.

when I get my dynotune done, I'll have to have him plot it diff. so I'll be able to see at what mph that happens. and give it a back to back test at the track doin it that way, vs the way Ive always done it. which is turn the sw. on at the starting line after Im staged and back in first gear.
man I cant wait to hit the track again.

what trans do you have? 60E? I wasnt aware they made a man. valve body for the 60E yet?


I'm using what started out as as Rock-On Stage 5 4L60e. It's been totally gone through again and the full manual option was chosen. Mine can be switched back to automatic shifting by going back into the valve body and changing a couple of things. Automatic gurus please chime in as I'm sure you can explain what I'm talking about.

Don't look for great ET gains from doing this. You're only using the extra horsepower available for 4 seconds or so of a track pass. I'd expect .05-.1 gain at the most but your trap speed will go up.

We ran a BBC monte carlo yesterday, locked and unlocked (700r4). It made 472 HP unlocked, and 503 HP locked. It picked up almost exactly what I told the owner it would pick up. That being said, it is my belief that it not good for the converter clutch. My tranny builder says its not good for it. But he says that it IS good for his business!!!lol

smokinstorm-
I see. basically full manual option in your shift kit.

far as track times, in my case, with my old iroc, I picked up .15 and 2 mph consistantly. that was with a faily tight conv. though. full size, 2800rpm stall speed on a mid 12 sec. car. seems there would be more to gain with a higher stall speed, and a car that makes more torque.

interesting though edcmat-l1.

keep them comeing. anyone else?

The curves cross at 5250, so just log and look to see what MPH you are at.... although I'm not sure what gear he is locking it up in; from the MPH I'm guessing 2nd? i don't think he is talking about the hp and tq on the same run. i think he is comparing two differnt runs unlocked vs locked, in the run the locked converter will eventualy pass or cross the unlocked converter. it is this crossing point that you would engage the electronic lockup and pickup a few mph

whats the whole idea about locking the conv. at the cross over point? cant figure out on my own what the bene of that would be. obviously, you dont want to lock it in first gear (700r4's cant physically anyways due to the port in the valve body being blocked in first gear) cause you'd lose all torque multi. from the stall, but once in sec. I cant figure out any benefit to waiting to a certain MPH. please explain.

so can anyone point to anything neg. about locking on the dyno?


Frost, just read your thread about your car build. I must say VERY SWEET. Im sure you are enjoying that car with your setup. what kind of track times you seeing now, and whats the boost up to? and what the hell happened to your oil pump oring? was it cut from someone jamming the pipe into the pump? cant figure out how that happened while assembleing the eng. on a stand. anyways cool story and thanks for all the pics and story.

chris
then the converter is unlocked it is slipping similiar to a standard clutch. if it is slipping it is not transferring all of the available horsepower to the wheels. lets say it is slipping 15%. when you car is generating 400 hp this would be a power loss of 60 hp. when you lock it up you can recover most of it and say only lose 4% or 16 hp. you just gained 44hp by locking it up.