Bazman

I've seareched but few touch on this subject.... so here goes

I'm currently running a Slingshot 2800 behind my 550hp LS1 that really only stalls around 2600 but at light throttle the engine will slip about an extra 500rpm to move out on light throttle, more on a hill, as I have 3.07:1 rear gears. Because the exhaust is fairly loud the slip is quite noticable around town. On the flat it will of course idle forward no problem.

I'm thinking of getting another converter with a lock up that can handle WOT at up to 700rwhp.

I don't want any more slip than I've got however! It feels loose as it is until I step on it.

So what converters are you guys running that could get more stall and be no looser than what I have and handle lock up at WOT?

Was thinking PC Vigilante 3200 with triple disck lock up - but have heard they are not as tight at light throttle as some. Can handle 500rpm slip - but 1000rpm would be a joke around town.

Cheers

mrvedit

I have a 525(?)HP LS2 with an aggressive cam (231/239 duration, .617/.624 lift, 113 LSA). I suspect you have something similar. I have set the lockup relatively high at 55 mph; anything lower and the engine/car will chug noticeable because the cam is not smooth under 1800 rpm. Others have reported similar chugging and "solved" it by also increasing their lockup speed.

I ran a Yank 3600 which I read is tighter than most around town (and conversely not as quick at the track). I don't have hills to deal with.

Considering that a triple disk is around $1000, I would suggest changing to a 3.42 or even 3.73 which will make your existing converter feel much tighter and make the car perform better at only a slight reduction in gas mileage.

justin hover

You have a 550hp stalled A4...pro/turbo charged?...nitrous?
Please fill us in...

Bazman

Custom STS supplied rear turbo on 5lb spring. Makes 450rw which is 550 at engine on an A4. 2000 Holden Commodore SS sedan.

Bazman

Sounds like a beast. No mine is a mild 222/226 @ 050 on 114/116 LC so will actually pull lock up from 1000rpm if I try (about 34mph) but from 40mph is better (in 4th). Around town speeds however (30mph or less) is the problem and there's lots of hills so it's sounds almost like a 4000 stall so it seems lol.

jimmyblue

iTrader: (11)

The lower the STR, the less pedal you will need to move
and the lower the light-throttle RPM rise will be. You also
would see torque multiplication continue to higher RPMs.
This (low STR) is not too popular though; I had to spec
mine custom.

Bazman

I've wondered about STR, that was good info. Thank you

My understanding is that a high STR only helps for the 1st second anyway as it dissolves once the car rolls out??

jimmyblue

iTrader: (11)

Right, STR is not just the raw torque multiplication
at stall, it also is the "slope" of how that multiplication
rolls off with RPM. A high STR hits hard and fades early
to 1:1; a low STR hits softer but multiplies further out.
With a 3500/2.0 I am seeing multiplication past 5000RPM
as evidenced by an uphill pull where I WOT-locked the
converter midway, and could see the acceleration fall
back.

Yank used to have some converter dyno curves in
their tech section that illustrate this (though I'm sure
there is variation by build / design, to the STR's relation
to efficiency, coupling-slope and so on).

Bazman

That is the clearest easiest to understand explanation I have ever heard after months of head scratching over conflicting info. Thank you, I wish the converter companies would make themselves as clear that.

So if I read that right - a big hit STR might be popular but is only any good for burn outs or on slicks? Then I'd far rather have the more efficient lower STR that gives more under the curve, has less slip at light throttle, and will still stall at the rpm you want at WOT.

mrvedit

Higher stall converters are also always looser; I don't think you would want a 4000 as you mentioned.

Jimmy: Yes, excellent explanation. I will also order a lower STR for my next converter.

LS-ONE_DAY

https://ls1tech.com/forums/automatic...str-guide.html