Efficient Non Lockup Converter VS Looser Locked 3rd Gear Converter?

[GNVYUS 1]

I'm mulling over this idea after seeing only 6-700rpm shift drops on my 5 disc Precision.

Scenario, exact same GN with identical launch stalls and 60ft times etc.

Let's say the non locker is a PTC which has a 5% slip.

VS

Precision 5 disc that slips much more at of the end of 1st and 2nd but when locked in 3rd gives you 100%.

I have two thoughts on this,

1) PTC would barely win out due to it being tighter though out the run.

2) Precision would barely win due to it getting through the gears faster and then while in 3rd from 85mph on it's 100% efficient.

Any experience with this scenario or time slips?

 

[Dusty Bradford]

I don't have any data as a direct comparison. A lot of variables with the weather on different days being a huge part of it.

Maybe someone who's made the swap can offer some info. The thing to look at would be mph in the 1/8 and 1/4 along with the 330' times.

The deciding factor would be how loose the lock-up is while in 1st and 2nd. Some combinations they're pretty efficient while others blow through alot more than you want.

 

[turbo nasty]

Hard to beat the MPH that a L/U gets u

 

[GNVYUS 1]

For debates sake let's assume everything is identical so it's just the converters and not weather etc.

Though I'd like to think that even a loose 5 disc Precision when locked in 3rd would make up for the inefficient 1-2, 2-3 shifts, this pops into my head.

PTC 5% slippage = ( 5% at 1-2 ) + ( 5% at 2-3 ) + ( 5% in 3rd ) = 15% slippage total.

Precision 10% slippage = ( 10% at 1-2 ) + ( 10% at 2-3 ) = 20% slippage total.

So even though you spend a longer time in 3rd and the Precision is 100% locked, it seems to give up a lot at the end of 1st and 2nd where the PTC is the same all the time.

But does a looser converter help you get into 3rd sooner so when locked you actually might gain back and then some the slippage because it's 100% for so long??

I'm so curious now. :wink:

 

[bison]

Hard to beat the MPH that a L/U gets u

Its even harder to beat the efficiency a PTC 9.5 gives you all the time. Im shifting into 3rd at about 85 mph. I have never seen an unlocked LU ever go over 80 before the 2-3. Most seem to be at around 78. This might not sound like a lot but the gain is there in 1st also. It translates into the lowest 60' times and the best efficiency in first and second where its needed most since the car isnt moving fast yet. Big drop in eighth e.t. A 4-5% slip up top might be about 1 mph vs a LU unit. I said might. But the LU cant touch the un locked efficiency of the NL while unlocked. It also wears out in a high output application. The PTC 9.5's seem to be bulletproof so far. The LU converter is heavier also.

 

[Dusty Bradford]

One of the jobs of a converter is to multiply torque. It can't do it when locked. The slip % may seem high in 1st and 2nd but the car will be faster because it's multiplying torque.

These guys who look for every .01 they can get will test numerous converters. In some cases a converter with 9% slip will be faster than one with 3%. The looser converter keeps the car in it's powerband and although it's less efficient, it runs faster. Getting a converter locked ASAP will not always work. If you have the hp to pull it you can get away with it. Most of the time if a car picks up a good bit of et by locking it early, it's because the converter is slipping badly in the 1st 2 gears.

In your example it's hard to say. I don't have enough data to answer it. The only customer who swapped from a 5 disk to a 9.5 n/l did not give et #'s. He only said the n/l crossed at the same mph at only 50 rpm more than the 5 disk locked and he was hooked.

 

[bison]

One of the jobs of a converter is to multiply torque. It can't do it when locked. The slip % may seem high in 1st and 2nd but the car will be faster because it's multiplying torque.

Thats where the flash stall comes into play. Slip is higher at flash (where its needed on launch and upshifts for torque multiplication )and comes down as the driveshaft speed increases in each gear. This cant happen if the converter is locked. Dusty, i know you know all this. Just trying to clarify the need for some slip in almost all applications.

 

[bison]

In really fast cars a lot more things come into play as far as converter selection goes. Everything form valvesprings, to varying tire height, turbos, and rear gear selection. Keep in mind that most guys that are running in a race class like TSM have to build around some obstacles. A big problem with TSM is the block and the required use of a 3 bolt turbo. There is no restriction on the converter though:biggrin: . That is huge. Look at the numbers these guys are throwing on the boards now. The biggest gains in the last few years were from the converter tech. Im not suprised the fastest all run 9.5" PTC's.

 

[Dusty Bradford]

Thats where the flash stall comes into play. Slip is higher at flash (where its needed on launch and upshifts for torque multiplication )and comes down as the driveshaft speed increases in each gear. This cant happen if the converter is locked. Dusty, i know you know all this. Just trying to clarify the need for some slip in almost all applications.

Your exactly right. Slip is a good thing at times. Duttweiler showed me some useful info at BG. They calculated slip in real time during the run with the MOTEC software. You could clearly see the slip% drop as rpm climbed. It was interesting to watch a graph of slip% during the entire pass.

 

[GNVYUS 1]

Dusty your point on it slipping/multiplying torque and getting through the gears faster was my dark horse aspect in the efficiency game.

Bison your 85mph vs 78mph shift at the same rpm is great info, that's a lot mph especially since most street races are already over for us by then.

The good news is we have 2 converters that have proven to get the job done and for a great price. For racing I might go PTC because the weight difference has to be at least 5lbs which rotating on the crank has to be a big deal. But I do like the 1500 cruise rpms when locked around town.

Dusty I got a quote from Level 10 for a 10" billet 1G Talon converter, $1300. I told you there was $$ in this for PTC to come play and dominate.

 

[bison]

Dusty your point on it slipping/multiplying torque and getting through the gears faster was my dark horse aspect in the efficiency game.

Bison your 85mph vs 78mph shift at the same rpm is great info, that's a lot mph especially since most street races are already over for us by then.

The good news is we have 2 converters that have proven to get the job done and for a great price. For racing I might go PTC because the weight difference has to be at least 5lbs which rotating on the crank has to be a big deal. But I do like the 1500 cruise rpms when locked around town.

Dusty I got a quote from Level 10 for a 10" billet 1G Talon converter, $1300. I told you there was $$ in this for PTC to come play and dominate.

With the 16 blade in my sig its only about 5% at light throttle cruise. Not giving up hardly any mpg there.