Converter Slippage 20-25% - Time to go to a non lock up? PL file.

[Justa6MB]

Hello, attached is a PL file and the time slip. My speedo is out since the last transmission change - but based on the track slip I calculated my converter slip %. I used Wallace's tool and got 20% and used TCI's and got 25%. Either way it's bad - I think... 6150 RPM @ 120 MPH ~ 11.38 @ 21# boost. I'm thinking about going to a non lock up from Dusty - hopefully he'll chime in. I understand shift points are important when spec'ing the correct converter. I'd like my shift points to drop for another reason and I'm also curious to know if there could be gains in going to a more efficient converter? It doesn't see much highway cruising anymore so I'm not too concerned about a few00 RPM's. Please let me know if you have any questions.
Thanks
D

 

[bison]

I cant imagine what it would be like at 25+. Converter would help a lot

 

[Dusty Bradford]

I can't see the log but anything in the 20-25% range in the 1/4 can surely benefit from another converter.

What rpm does it shift at? What is the rpm falling back to?

 

[TurboBob]

looks like 6060 RPM dropping 350

Its a powerlogger file, software attached. Its a windows program, no installation just unzip it to a folder and run it. You can drag the .DAT file onto the open program to load it or use the load button on the F3 pane.

Bob

 

[wickedtt]

What converter are you using and how healthy is the trans. shifting?

 

[bison]

Sounds like a converter that was built for a 400hp NA engine.

 

[Justa6MB]

Hi guys, the tranny is a stage II from EA new this spring, and the converter is a 3200 lock up - here's the info from vendor website:

"PTC 10" Lock-Up Torque Converter
This 3200 stall converter is great for most street applications up to 67 turbos in journal bearing or a 70GTQ in ball bearing. get out of the hole but still tight on top just like you would want. This is our new GO-TO converter they work great."

Thanks
D

 

[Justa6MB]

Oops, something happened to the post - I had the shift points listed. Anyway on the 1-2 shift it dropped from 6182 to 5816, and on the 2-3 shift it dropped from 6067 to 5681. So this converter seemed like a good idea at the time but we all know hindsight is 20/20...
Thanks
D

 

[Nick Micale]

.................. Please let me know if you have any questions.
Thanks D

The one question is what is the RPM at 0 boost when on stall?

Since I am unable to read your files posted, but have to go by your data posted, the 25% figure does not make sense?

A 400 RPM drop on both shift points does not sound bad to me, but knowing 60 ft times also would help.

At 66oo RPM, I have a 400 rpm drop in both shifts, and this is with a 5000 stall converter that has 0 boost at 3100 RPM. For a mid-11 car, a 9/11 LU converter has proven to be an excellent performer.

If your car is used mainly at the track, the most important job of the converter is getting you off the line quickly w/o spinning your tires.

So how is your performance there? I have a hell of a good top end, but E.T. is what wins the race.

You may not have the optimum converter for your build, but it is impossible to give helpful info without lots more data.

 

[JP112_89]

I had PTC 3200 l/u too. I was way to loose for my application. Shifts would only drop 350-400 rpm.

Ideally, I think 800 rpm drop is great. This is where I am at now with my tight 9/11.

Joe

 

[Dusty Bradford]

A 3200 stall at 0 boost is too loose for your power level and is why I rarely use that converter in a Buick application. Depending on your turbo size you want a 2800 stall or a 9.5 non lock. The 9.5 is loose down low and tight up top as the add claims.

 

[Nick Micale]

I had PTC 3200 l/u too. I was way to loose for my application. Shifts would only drop 350-400 rpm.......................Joe

Actually Joe, the PTC was too tight if you only had a 400 RPM drop and new converter is much looser if you have double the RPM drop.

As you increase HP and RPM shift points, the drop will be greater with a given converter, so as you change your baseline HP, you may need to re-stall the converter?

My experience is most guys run a converter that is too tight, especially for the track.

I prefer to start on the loose side, and then tighten the converter if needed, which is rare as we have gained experience with various builds to nail it initially.

Another issue to be aware of is the advertised converter stall usually will NOT be the same RPM where you are with 0 boost.

 

[Nick Micale]

Many of the street/strip builds I have done lately have used 67 to 70mm turbos.

I have found that if we do not have a converter that will stall a minimum of 3100 RPM at 0 boost, it will be a laggy dog, even if it is a BB center section!

 

[bison]

Actually Joe, the PTC was too tight if you only had a 400 RPM drop and new converter is much looser if you have double the RPM drop.

As you increase HP and RPM shift points, the drop will be greater with a given converter, so as you change your baseline HP, you may need to re-stall the converter?

My experience is most guys run a converter that is too tight, especially for the track.

I prefer to start on the loose side, and then tighten the converter if needed, which is rare as we have gained experience with various builds to nail it initially.

Another issue to be aware of is the advertised converter stall usually will NOT be the same RPM where you are with 0 boost.

It is my experience that the cars don't often perform close to the level they should so that the converter appears too tight even though it's really not if the engine was hitting the converter as hard as it should. The rpm drop doesn't mean much either. My typical stock shortblock with a cast 60-1 turbo and 9.5" converter may only see 400 rpm drop but the shift point is usually around 5500 with a small hyd cam unless the engine has really good heads and the boost (mass flow) is increased a lot. Then it likes higher shift points. My blue car ran 10.61 with a cast 60-1 and it was shifted around 5500. I don't remember seeing the rpm drop below 5050. I dynoed that car over 200 times trying various things. Peak power was right at 5100. The engine spent over 9 seconds of the pass within 300rpm of peak power. If I see more than 800rpm drop on any of these typical bolt on small hyd cam engines then the shift rpm was likely too high or the engine wasn't making crap for power and the converter is overpowering it.

 

[Dusty Bradford]

Nick. If the new converter drops more rpm it is indeed tighter, not looser. More rpm drop= tighter converter. In this case where the converter is flashing to 5600 rpm and only running 11.30, the converter is too loose. This is why he's seeing 20-25% slip. The flash point is too close to the shift point.

 

[Justa6MB]

Thanks for the posts guys. This converter stalls at 3800 at 0 boost. 60' on this run was 1.6920. My 60' times have been horrible - but I've just started to work on the suspension. So Dusty if 3200 at 0 boost is too loose then I assume that 3800 at 0 boost is really too loose then in your opinion? The turbo is a GT6765 water cooled. I really like the sound of 5500 shifts.

 

[Justa6MB]

Dusty I was typing when you posted So what is the flash point? And do you have enough information to spec a converter?

 

[Nick Micale]

Nick. If the new converter drops more rpm it is indeed tighter, not looser. More rpm drop= tighter converter. In this case where the converter is flashing to 5600 rpm and only running 11.30, the converter is too loose. ...

You are right of course Dusty, another reason I should not post early in the AM before my brain is awake!

 

[Dusty Bradford]

If your converter is stalling 3800 then it's 600 rpm looser than it should be. This is usually caused by variables in the transmission. The converter can be adjusted to make it tighter. Your shift rpm is determined by your cam size. 5500 is a little low for 6765. I hope your cam can support 5800. The converter could then be adjusted to flash to 5000-5200 which will give u enough stall to spool the turbo but still couple.

 

[Justa6MB]

Ok now I'm getting confused. So what variables in the transmission cause this higher stall RPM and should I be looking into the tranny? What is a 9/11 converter? Is it the same as a 9.5 Non Lock? My converter could be tightened up? Could the modified converter work as good/efficient as a non lock? On this pass once above 5800 I was only under 5800 for 2.2 seconds which was right after the 2/3 shift. Then finally what is the flash RPM?