IROCThe5.7L

I seen quite a few debates on locked vs an unlock convertor when doing 1/4 runs. But I hear if you get your car dyno'ed, you should lock the convertor at about 50mph. From what I understand this will give you higher numbers along with a more accurate reading. Any truth to this?

sofakingdom

iTrader: (1)

HIgher, probably not; more accurate, maybe. Less accurate, maybe too. Depending on how you define "accurate".

Although with a stock-ish converter, as long as you're more than 500 RPM or so over its nominal stall, it won't make more than a few % difference anyway. Where it REALLY matters is when the stall is such that it goes back into slip after a shift. The torque multiplication will produce some genuinely weird-looking meaningless curves.

Dyno it like you run it, whatever that is. After all the purpose of a dyno run is to predict how the car will behave in the real world, not to produce some jaw-dropping "numbers".

IROCThe5.7L

I agree. I just want to make sure I get "real world" numbers. I was just a little confused on the whole "science" behind it I guess you can say. Unfortunately I'm pretty sure the cars going to dyno much lower than I would have expected-lol


Thanks for the reply!

project89

iTrader: (1)

if u have a high stall lock it or u will end up with a dyno graph that looks like mine

fireturd350

iTrader: (8)

Unless you have a converter designed for WOT lockup (multi-disck clutches) it is possible to burn up the lockup at WOT that's why stock converter wiring and most aftermarket kits unlock after certain vaccum drop.

1989GTATransAm

iTrader: (3)

I agree with the above post. I would talk to whoever manufactured your torque converter. It is real easy to burn up the clutch material.

Burnout91

Are you guys talking about locking up while at full throttle, or going full throttle while the tcc is locked?

Bill

fireturd350

iTrader: (8)

Apparently I was wrong about my previous statement with WOT unlocking with stock wiring.

https://www.thirdgen.org/forums/tran...er-lockup.html

From that post it looks like code is in the ECM to lockup above specific MPH. Dana also steps in and mentions it is possible to burn up a Vigilante 2800 stall converter doing this.

Orr89RocZ

iTrader: (20)

You will most likely ALWAYS see hp gain when locking up if you have any kind of higher stall converter.

10-15whp gain on bolt on L98. I got the dyno graph to show what happens when a converter locks up. It draws a circle

20-30whp on higher hp motors depending on the stall speed. We gained 15-20 on a 330whp setup.

I locked the converter for dyno tuning just to get higher numbers. Plus it makes more sense to me to lock it up so the driveline is truely a 1 to 1 ratio and no slipping is added from the converter.

Other reason was with a 3600 rpm stall, you dont see below 3600 rpm on the dyno. you have to start the pull near 3600 and go from there. If you locked it, the rpms drop to 1 to 1 ratio, so you can start your pull at 3000 and see what the motor is doing down low. You can dial in the air fuel and timing there alot easier.

On the street, I tuned my 383 with open converter and couldnt see the 3000-4000 range well. When I got on the dyno and locked it, I saw it was very lean between those rpms. On the street the rpms flashed by so fast, i couldnt read the wideband gauge.

I gained 30lbft on the dyno and ended up gaining 2-3 mph in the 1/4 mile from 116 to 118-119.

But like said, you have to be carefull. Some converters dont like to lockup. Mine was ok with it.

project89

iTrader: (1)

id never try to lock it up under wot unless the converter has a special clutch in it to handle it.

ont the dyno i would get the tires rolling then lock the converter with a manual overide switch then do the pull

on my tt i will be using a drive shaft speed sensor hooked t my megasquirt ecm to lock the converter at a very low mph for track use so it dosent take a full power wot hit @ 90mph

Orr89RocZ

iTrader: (20)

in the chip, I used TCC unlock prevention threshold constant, and set that to 50mph which just happened to be 1-2 mph higher than the MPH that my 700r4 would downshift into 2nd gear. Not good, you want to dyno in 3rd or your 1 to 1 ratio gear.

So at 50mph it would stay in 3rd gear when going WOT. I mashed the gas, and soon after it would lock and rpms would drop from 3600 to like 2300. Motor bogs and picks up from there. For some reason tho the run only started from 3000 rpm on the chart. We hit the 7K rev limiter too but the chart showed runs to 6400-6500 ish I believe. Oh well hard to say what happened, but I got solid torque readings from 3000-4000 when I couldnt before with the converter open.

IROCThe5.7L

Wow, I'm confused. I'm still running the stock convertor (for now). Should I lock it at 50 or not? My appointment is at 1PM. My TCC unlock prevention threshold constant in my chip is set at 95mph.

Orr89RocZ

iTrader: (20)

i'd lock it, as I've locked stock converter before but that was on a mild bolt on 254whp L98...not sure how well they do with high hp motors

If you dont, thats fine, stock converter wont eat up too much power, but just expect 10-15whp less once you get the numbers.

IROCThe5.7L

Ok guys, here are the numbers. I was expecting it to dyno lower by my poor track times. Stock L98 bottom end, AFR 195's, Comp cam (276hr10), HSR intake, and Ford 30lb injectors.

First run: 34 degrees of timing:

308rwhp@5750rpm / 295ftlbs@5200rpm

Second run: Nothing changed except I locked the convertor at 50mph:

313.6rwhp@5750rpm / 296ftlbs@5216rpm

Third run: Did NOT lock the convertor at 50, 35 degrees timing, added more WOT fuel, held it to a higher RPM.

316.5rwhp@6150rpm / 295ftlbs@5200rpm.

So a degree of timing and more WOT fueling gained me 8rwhp and no torque. But what I don't like is that on my highest HP run, from 5700rpm to 5900rpm the HP drops a little bit, then goes back up. So I think it might be an issue of too much fuel there? It didn't do that on my other runs.

Video:
http://www.youtube.com/watch?v=jPSc9XPJMdA

Orr89RocZ

iTrader: (20)

What air fuel did you start at and what did it end up at? What rpm did you hit full timing?

Torque and hp seem low for the combo but peak hp rpm seems abit more accurate

IROCThe5.7L

No windband. I have no idea. I gave up tuning it since I'm building a new engine over the winter. The car bone stock puts down about 200 to the wheels? I added about 120rwhp. Not to shabby. I made more hp every run. I wonder what I could have gotten out of her.

Orr89RocZ

iTrader: (20)

I would be too. My buddy's L98 with old AFR 190's and xfi 280 cam went 330whp before valvefloat. He was going to replace springs and retune, but decided to go with an LSx 6.0 swap. We'll never know what it would have done. I was guessing 350's whp and run 11.8's. It already went 12.2 in warmer air

IROCThe5.7L

My O2 mv's were around 900 all the way through the run. So I don't think my afr is way off. But I know I need a wideband. Isn't that 280 a larger cam than mine? I think I got one more trip to the track this year and the good ole L98 gets retired. I'm pleased though. Over 300rwhp and it runs great. It would have a stall already but I want to match it with the new engine.

Orr89RocZ

iTrader: (20)

yeah its abit bigger, but the heads arent as good as yours