How much converter slip??

MEXJOE · 06-10-2010, 11:24 AM

What %converter slip is normal for a STOCK Elm. car?

Alan Roehrich · 06-10-2010, 11:37 AM

It depends on the combination.

MEXJOE · 06-10-2010, 11:39 AM

Quote:

Originally Posted by mexjoe

what %converter slip is normal for a stock elm. Car?

396 325 hp 69 camaro

Alan Roehrich · 06-10-2010, 11:50 AM

An average car will see around 12-14%, maybe a little more. The problem is that they need stall to get off the line, but cannot pull enough gear on top and make enough RPM and HP to really lock up a converter and make it efficient.

Robert Simpson · 06-10-2010, 10:27 PM

So I take it that if you have 8-10% you have a very efficient conv? I am speaking of a sb stocker. How do you determine the % correctly?

Robert

Alan Roehrich · 06-11-2010, 08:31 AM

Well, with a car that needs a ton of flash stall to get off the line good, but cannot turn a lot more RPM and make good power above that flash stall, yes, 8% is pretty good. That can be difficult with a lower HP stocker that doesn't turn a lot of RPM. If your finish line RPM is more than around 1500 RPM higher than your flash stall, and is also more than 800 RPM higher than your peak HP, it can be hard to get a converter to couple up really well.

Your finish line RPM and the MPH it should give, with your gear ratio and tire size, compared to your finish line MPH, will let you know about what your slippage is.

Of course, to do that, you are assuming the lights for the MPH clocks are set very accurately. That might be a big assumption, considering the variances you see in how well they are set of the starting line.

ron mattson · 06-15-2010, 02:47 PM

Robert, to figure slip multiply your mph say 114 x gear ratio 5.13 x 336= 196499 then
divide by tire height 29.5 = gives you a rpm of 6661 then multiply by 1.08 for 8 % =7193.
just enter your correct values. mph x gear ratio x 336=@ then divide @ by tire height =true rpm with no slip and multiply by 1.08 for 8% 1.09 for 9% and so on to get your final rpm .

Glenn Briglio · 06-15-2010, 05:28 PM

Most flogged out combos will have less than 5% slippage. Works on our car!

ron mattson · 06-15-2010, 07:15 PM

The formula above is for radial tires, bias ply tires will grow, each manufacturer can
tell you approx how much at a given speed for any size tire. Like Alan stated each
car can vary in how much flash it will take to get it moving and how it will lock up on
the big end will depend on how much power and powerband width are available.
Most of the converter companies can get you really close if you give them accurate
info for hp, tq, weight,gearing and rpm potential. one other variable is where you race
sea level will differ greatly from altitude and so on. trial and error!!!! just my .02$

demps45 · 07-18-2010, 05:59 PM

I could be wrong, but if you record the engine RPM, and record the driveshaft RPM, assuming your in high gear and it's a 1:1 ratio, then the difference would be the converter slippage.

06-10-2010, 11:24 AM	#1
MEXJOE Senior Member Join Date: Jun 2008 Location: nhranumbers.com Posts: 875 Likes: 137 Liked 165 Times in 51 Posts	How much converter slip?? What %converter slip is normal for a STOCK Elm. car?

06-10-2010, 11:37 AM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,573 Liked 1,837 Times in 417 Posts	Re: How much converter slip?? It depends on the combination. __________________ Alan Roehrich 212A G/S

06-10-2010, 11:50 AM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,573 Liked 1,837 Times in 417 Posts	Re: How much converter slip?? An average car will see around 12-14%, maybe a little more. The problem is that they need stall to get off the line, but cannot pull enough gear on top and make enough RPM and HP to really lock up a converter and make it efficient. __________________ Alan Roehrich 212A G/S

06-10-2010, 10:27 PM	#5
Robert Simpson Senior Member Join Date: Aug 2004 Location: Jacksonville, Florida Posts: 808 Likes: 7 Liked 20 Times in 12 Posts	Re: How much converter slip?? So I take it that if you have 8-10% you have a very efficient conv? I am speaking of a sb stocker. How do you determine the % correctly? Robert

06-11-2010, 08:31 AM	#6
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,573 Liked 1,837 Times in 417 Posts	Re: How much converter slip?? Well, with a car that needs a ton of flash stall to get off the line good, but cannot turn a lot more RPM and make good power above that flash stall, yes, 8% is pretty good. That can be difficult with a lower HP stocker that doesn't turn a lot of RPM. If your finish line RPM is more than around 1500 RPM higher than your flash stall, and is also more than 800 RPM higher than your peak HP, it can be hard to get a converter to couple up really well. Your finish line RPM and the MPH it should give, with your gear ratio and tire size, compared to your finish line MPH, will let you know about what your slippage is. Of course, to do that, you are assuming the lights for the MPH clocks are set very accurately. That might be a big assumption, considering the variances you see in how well they are set of the starting line. __________________ Alan Roehrich 212A G/S

06-15-2010, 02:47 PM	#7
ron mattson Member Join Date: Nov 2005 Location: cloquet mn Posts: 466 Likes: 17 Liked 67 Times in 30 Posts	Re: How much converter slip?? Robert, to figure slip multiply your mph say 114 x gear ratio 5.13 x 336= 196499 then divide by tire height 29.5 = gives you a rpm of 6661 then multiply by 1.08 for 8 % =7193. just enter your correct values. mph x gear ratio x 336=@ then divide @ by tire height =true rpm with no slip and multiply by 1.08 for 8% 1.09 for 9% and so on to get your final rpm . __________________ Ron Mattson 5015 STK Last edited by ron mattson; 06-15-2010 at 04:06 PM.

06-15-2010, 05:28 PM	#8
Glenn Briglio VIP Member Join Date: Nov 2002 Location: Massapequa Park,NY Posts: 1,285 Likes: 1,903 Liked 973 Times in 310 Posts	Re: How much converter slip?? Most flogged out combos will have less than 5% slippage. Works on our car!

06-15-2010, 07:15 PM	#9
ron mattson Member Join Date: Nov 2005 Location: cloquet mn Posts: 466 Likes: 17 Liked 67 Times in 30 Posts	Re: How much converter slip?? The formula above is for radial tires, bias ply tires will grow, each manufacturer can tell you approx how much at a given speed for any size tire. Like Alan stated each car can vary in how much flash it will take to get it moving and how it will lock up on the big end will depend on how much power and powerband width are available. Most of the converter companies can get you really close if you give them accurate info for hp, tq, weight,gearing and rpm potential. one other variable is where you race sea level will differ greatly from altitude and so on. trial and error!!!! just my .02$ __________________ Ron Mattson 5015 STK

07-18-2010, 05:59 PM	#10
demps45 Junior Member Join Date: Jul 2009 Location: Lockport, NY Posts: 7 Likes: 0 Liked 0 Times in 0 Posts	Re: How much converter slip?? I could be wrong, but if you record the engine RPM, and record the driveshaft RPM, assuming your in high gear and it's a 1:1 ratio, then the difference would be the converter slippage. __________________ Fred Dempsey G/S, H/S, I/S, D/SA