View Full Version : Do Circle D converters rob top end?


its turbo time
04-04-2012, 10:12 AM
Do Circle D converters rob top end and trap speed more than other brand stalls??

I had a reputable tuner who is sponsor on this board say that the reason my car is trapping so low is because of the Circle D converter I have. He says they are known for robbing top end, which was news to me as everything I ever read about them was absolutely positive and how well it seems to work in my car.

This issue came up after I did a 224 cam swap on my bolt ons 98 ta with a 3200 circle d converter and my trap speed was only 107. I contacted the guy who did my tune and he said I was SOL and that he did everything he could and my car is basically a turd lol.

The car put down 360 hp/373 which seemed reasonable for how small the cam is, but the trap speed seemed really low. So I contacted another tuner and asked what he thought and he seemed to think that the Circle D converter was robbing my top end and that is why my trap speed was so low.

Is that right?

TA1364
04-04-2012, 10:54 AM
What was your 60' on the 107 run? I really doubt the converter is the problem.

black00ssFL
04-04-2012, 11:10 AM
Trans could be slipping. What's the DA on the 107 run?

SuperSlow02
04-04-2012, 11:26 AM
You'll gain mph... Only a manual trans will trap higher then a stalled auto unless you have a mechanical issue.

Circle-D
04-04-2012, 11:47 AM
I would like to know more info on this. Especially the tuner, you can PM me the details if you want. You can easily check the converter efficiency by logging TCC slip and compare it to the trap RPM. But also watch out for a false slip number if the 3/4 clutches are slipping. If you want to call to discus this further that is cool. And to answer your question, no - Circle D converters do not rob top end.

Chris

Jake's Performance
04-04-2012, 12:35 PM
I would like to know more info on this. Especially the tuner, you can PM me the details if you want. You can easily check the converter efficiency by logging TCC slip and compare it to the trap RPM. But also watch out for a false slip number if the 3/4 clutches are slipping. If you want to call to discus this further that is cool. And to answer your question, no - Circle D converters do not rob top end.

Chris

I've never seen this to be the case. We have multiple customers running Circle-D converters. They typically are very efficient on the top end.

We sell our own line of converters but we never steer anyone away from a Circle-D if that is what they want to use.

A looser converter can sometimes be a bit less efficient on the top end, and sometimes converter slip numbers don't tell the whole story (some combos need a sloppy converter) but I would say in my experience, Circle-D units tend to be more efficient and on the tight side.

its turbo time
04-04-2012, 01:10 PM
What was your 60' on the 107 run? I really doubt the converter is the problem.

It was a 2.0 60', I wasn't hooking at all! Only ran a 13.0. Pretty disappointing

its turbo time
04-04-2012, 01:13 PM
I would like to know more info on this. Especially the tuner, you can PM me the details if you want. You can easily check the converter efficiency by logging TCC slip and compare it to the trap RPM. But also watch out for a false slip number if the 3/4 clutches are slipping. If you want to call to discus this further that is cool. And to answer your question, no - Circle D converters do not rob top end.

Chris

I sent you a pm, I plan on doing exactly that when I get the chance.

A couple years ago I upgraded a lot of the components in the tranny. Like the beast sunshell, clutch packs and servos and a shift kit

jimmyblue
04-04-2012, 03:08 PM
As a rule a higher stall speed converter will slip more
up top (TCC slip RPM). If you go just by the number
it will look pretty bad sometimes (I had a TCI 3000
that was 97% efficient by 5K, have TCI 3500 data
that says 95% but has to get to 6K to get there,
and a TCI 3800 that was south of 90% at 6K).

But what you do not know, is how much of that
slip as %, is going to heat and how much to the
fading tail of torque multiplication. You'd have to
compare locked RWT@MPH to unlocked RWT@MPH,
to gauge that. My low-STR Fuddle is still multiplying
past 5000RPM, going by that kind of comparo. The
little TCI was not.

Look at the ratio of input shaft RPM to output shaft
RPM and compare to nominal in-gear ratio to assess
gearbox friction slip, separately from converter.

its turbo time
04-04-2012, 06:00 PM
As a rule a higher stall speed converter will slip more
up top (TCC slip RPM). If you go just by the number
it will look pretty bad sometimes (I had a TCI 3000
that was 97% efficient by 5K, have TCI 3500 data
that says 95% but has to get to 6K to get there,
and a TCI 3800 that was south of 90% at 6K).

But what you do not know, is how much of that
slip as %, is going to heat and how much to the
fading tail of torque multiplication. You'd have to
compare locked RWT@MPH to unlocked RWT@MPH,
to gauge that. My low-STR Fuddle is still multiplying
past 5000RPM, going by that kind of comparo. The
little TCI was not.

Look at the ratio of input shaft RPM to output shaft
RPM and compare to nominal in-gear ratio to assess
gearbox friction slip, separately from converter.

Hows your fuddle holding up? I had a 3400 that quit locking up after only a few months. Thanks for the info also!

Cam72aro
04-04-2012, 08:31 PM
Is this on street tires? 2.0 60' time is horrible. Get some tires on it. You can't expect to have a good mph with that bad of a sixty.

01ssreda4
04-04-2012, 10:57 PM
I've driven a Circle D car at the track. It performed as expected. So I'd say no I don't agree with your tuner. However, I'm curious what size converter you have? Not stall speed but what actual size is the converter? 11, 10.5, 9.5 inch etc...

Killer5.3
04-05-2012, 01:59 AM
I just put a circle D 3600 3c in a friends bolt on camaro. It has pacesetter long tubes, TSP off rd Y, SLP LId, ported stock t/b, magnaflow exhaust, and it trapped 108-109 consistently full weight with 225lbs driver in +1100 da. So I don' think that it hurt trap speed at all. Like was said in another thread you started , you have a problem with motor, tune , or could be tranny slipping more than likely is one of your problems.

its turbo time
04-05-2012, 07:51 AM
I just put a circle D 3600 3c in a friends bolt on camaro. It has pacesetter long tubes, TSP off rd Y, SLP LId, ported stock t/b, magnaflow exhaust, and it trapped 108-109 consistently full weight with 225lbs driver in +1100 da. So I don' think that it hurt trap speed at all. Like was said in another thread you started , you have a problem with motor, tune , or could be tranny slipping more than likely is one of your problems.

Yeah, I know. I really don't think it's the converter. I just figured I'd pose the question since the tuner made the claim.

bwkmaro
04-05-2012, 09:35 PM
well when my buddys grandfather get someone in the shop that is saying their tranny might be slipping he takes about 5 oz of lucas tranny fix puts it in then tells them to take it for a ride to see if its any better. (i think thats the only reason he keeps a bottle around haha) and he says its usually a pretty good determination the tranny is slipping. the guy is 78 and can build a 4l60 with his eyes closed in his sleep so it cant be to bad advice. i havent tried it yet tho :P

btw wanna race? another v8 under the belt wouldnt hurt, haha jking

projectX
04-05-2012, 10:32 PM
Possible tranny issue - my guess.

WhitePhoenix99
04-05-2012, 10:59 PM
Kinda weird your tuner is blaming the converter.. my cammed LT1 traps higher than your cammed LS1 and I run a Circle D converter.. clearly there is another issue here

its turbo time
04-09-2012, 09:48 AM
Kinda weird your tuner is blaming the converter.. my cammed LT1 traps higher than your cammed LS1 and I run a Circle D converter.. clearly there is another issue here

Thank you! Lol thats proof enough right there!

I used my timing tuner and added about 4 degrees of timing and it seems to pull harder on top end. Im thinking the tuner left timing out cuz he wrote me a no2 tune.

its turbo time
04-09-2012, 09:49 AM
Will that make the difference. I dunno, but im planning in taking it to the track tomorrow to try again

its turbo time
04-09-2012, 11:16 AM
well when my buddys grandfather get someone in the shop that is saying their tranny might be slipping he takes about 5 oz of lucas tranny fix puts it in then tells them to take it for a ride to see if its any better. (i think thats the only reason he keeps a bottle around haha) and he says its usually a pretty good determination the tranny is slipping. the guy is 78 and can build a 4l60 with his eyes closed in his sleep so it cant be to bad advice. i havent tried it yet tho :P

btw wanna race? another v8 under the belt wouldnt hurt, haha jking

So if that helps the tranny is slipping? Might try it...if you find yourself near STL we can line em up!