school me on stalls
05-17-2007, 04:41 AM
#1
11 Second Club
Thread Starter
iTrader: (9)
Join Date: Mar 2007
Location: Avondale, AZ
Posts: 1,016
Likes: 0
Received 0 Likes
on
0 Posts
school me on stalls I'm new to the auto game. This is my 5th car and first auto. I love 5 speeds but well racing street or strip seems like autos always come out on top and less stress on everything. Anyways how does a stall converter work, what does it do etc. I know the basics but not much more....car i got came with a pro torque 3000 stall
05-17-2007, 05:47 AM
#2
11 Second Club
I'll use my converter as a specific example. I have a TCI 3500. There are four important numbers for any torque converter.
1). Stall speed.
2). STR (or stall torque ratio).
3). Shift extension.
4). Effiency.
The stall speed is basically what the converter will stall or flash to when you go wot from a dig or a roll. I have a 3500 stall so when I am cruising at 30 mph and I punch it my rpm's jump to 3500 and climb from there. The ideal stall speed is generally about 700 rpm's less then where your motor makes peak power. The whole idea of a stall is to go to where your engine makes the most power. LT1's make peak power down low in the rpm's so they generally stick with 2500-3000 stalls. LS1's make power higher in the rpm's so we get more from 3500-4000 stalls.
My converter has a 2.5 STR. This multiplies the torque off the line. Basically the higher the number the harder the launch. 1.6-1.9 is extremly mild. 2.0-2.4 is a good street/strip STR and 2.5+ is a great drag strip STR. Which STR is best suited depends on the tires and application. Street only car on street tires would want a lower STR. Strip only cars on slicks want a very high number. Street/strip cars with drag radials might benifit from the mid size STR's.
The shift extension is what rpm you drop to after a shift. Mine is 4,700 so if I went wot at 30 mph I would flash to 3500 rpm's, climb to 6,200 (my shiftpoint), shift to second, drop to 4,700 rpm's and climb up from there. You want the shift extension to meet your motor goals. If you're spraying you might want a smaller shift extension. For NA cars that make a lot of top end power you want a larger one.
Effiency is based on a percentage. The smaller the percentage the more HP it will rob you of. Just like a transmission and rearend eat FWHP so does a converter. Manufacturers and STR are the biggest factors in effiency. Yank for example makes more effiecient converters then TCI. STR is the other factor. The higher the STR the less efficient the converter. My converters effiency is about 90-93% I believe. But there can be 2.2 STR Yank converters that have 96-98% effiency. For street cars effiency matters more then big STR's. At the track I'll take the bigger STR anyday.
Now to sum this up lets look at my best ET time and run through the whole run. I lined up at the tree and brake stalled to 2000 rpm's. On the third yellow I floored the gas flashing my converter from 2000 to 3500 rpm's. With the help of a 2.5 STR the torque was multiplied to the point that I was thrown back in my seat hitting a 1.66 60' time. My rpm's climbed to 6,200, I shift into second, I dropped to 4,700 rpm's and climbed to 6,200, I shifted into third, I dropped to 4,700 and climbed to about 5,200 rpm's as I crossed the finish line in 12.31 seconds @ 109.45 MPH.
This is all about racing though. What about normal street driving? The higher the stall the more gas it takes to get moving. Big stalls generally feel looser. By loose I mean you hit the gas (not wot) and feel sluggish. Smaller stalls feel tighter. By tighter I mean you hit the gas and lunge forward. In my case I feel a nice inbetween of loose and tight. Perfectly streetable IMO. You'll also notice higher rpm's when going say under 40 mph, especially if you are driving uphill. I cruise 30 mph @ 1,800 rpm's where I was probably around 1,300 on the stock stall. Gas mileage in town will go up but the trade off is well worth it.
Finally, I have a 40 mph lockup. That means my converter locks whenever I am cruising at any speed at or above 40. So on the highway I will essencially bypass the converter and my rpm's drop back down to normal cruising rpm's. This is why city MPG go down with a bigger stall but HWY MPG is unaffected. Some race converters do not have lockup but all the street/strip converters by Yank, PI, Fuddle, TCI, ect do.
Sorry it was so long and I hope that helped.
1). Stall speed.
2). STR (or stall torque ratio).
3). Shift extension.
4). Effiency.
The stall speed is basically what the converter will stall or flash to when you go wot from a dig or a roll. I have a 3500 stall so when I am cruising at 30 mph and I punch it my rpm's jump to 3500 and climb from there. The ideal stall speed is generally about 700 rpm's less then where your motor makes peak power. The whole idea of a stall is to go to where your engine makes the most power. LT1's make peak power down low in the rpm's so they generally stick with 2500-3000 stalls. LS1's make power higher in the rpm's so we get more from 3500-4000 stalls.
My converter has a 2.5 STR. This multiplies the torque off the line. Basically the higher the number the harder the launch. 1.6-1.9 is extremly mild. 2.0-2.4 is a good street/strip STR and 2.5+ is a great drag strip STR. Which STR is best suited depends on the tires and application. Street only car on street tires would want a lower STR. Strip only cars on slicks want a very high number. Street/strip cars with drag radials might benifit from the mid size STR's.
The shift extension is what rpm you drop to after a shift. Mine is 4,700 so if I went wot at 30 mph I would flash to 3500 rpm's, climb to 6,200 (my shiftpoint), shift to second, drop to 4,700 rpm's and climb up from there. You want the shift extension to meet your motor goals. If you're spraying you might want a smaller shift extension. For NA cars that make a lot of top end power you want a larger one.
Effiency is based on a percentage. The smaller the percentage the more HP it will rob you of. Just like a transmission and rearend eat FWHP so does a converter. Manufacturers and STR are the biggest factors in effiency. Yank for example makes more effiecient converters then TCI. STR is the other factor. The higher the STR the less efficient the converter. My converters effiency is about 90-93% I believe. But there can be 2.2 STR Yank converters that have 96-98% effiency. For street cars effiency matters more then big STR's. At the track I'll take the bigger STR anyday.
Now to sum this up lets look at my best ET time and run through the whole run. I lined up at the tree and brake stalled to 2000 rpm's. On the third yellow I floored the gas flashing my converter from 2000 to 3500 rpm's. With the help of a 2.5 STR the torque was multiplied to the point that I was thrown back in my seat hitting a 1.66 60' time. My rpm's climbed to 6,200, I shift into second, I dropped to 4,700 rpm's and climbed to 6,200, I shifted into third, I dropped to 4,700 and climbed to about 5,200 rpm's as I crossed the finish line in 12.31 seconds @ 109.45 MPH.
This is all about racing though. What about normal street driving? The higher the stall the more gas it takes to get moving. Big stalls generally feel looser. By loose I mean you hit the gas (not wot) and feel sluggish. Smaller stalls feel tighter. By tighter I mean you hit the gas and lunge forward. In my case I feel a nice inbetween of loose and tight. Perfectly streetable IMO. You'll also notice higher rpm's when going say under 40 mph, especially if you are driving uphill. I cruise 30 mph @ 1,800 rpm's where I was probably around 1,300 on the stock stall. Gas mileage in town will go up but the trade off is well worth it.
Finally, I have a 40 mph lockup. That means my converter locks whenever I am cruising at any speed at or above 40. So on the highway I will essencially bypass the converter and my rpm's drop back down to normal cruising rpm's. This is why city MPG go down with a bigger stall but HWY MPG is unaffected. Some race converters do not have lockup but all the street/strip converters by Yank, PI, Fuddle, TCI, ect do.
Sorry it was so long and I hope that helped.
05-17-2007, 08:31 AM
#3
Originally Posted by darrensls1
My converters effiency is about 90-93% I believe. But there can be 2.2 STR Yank converters that have 96-98% effiency.
05-17-2007, 11:44 AM
#6
11 Second Club
Originally Posted by RevGTO
Jimmyblue has posted graphs showing his old TCI 3000 at about 97% efficiency. I doubt your 3500 is as low as your estimate. I'm not so sure Yank efficiency is head and shoulders above everybody else.
In the 2800-3600 range I'm sure Yanks are not head and shoulders above the others. But with 3800+ and 2.6+ STRs I think the extra money for Yanks can be seen in effiency over TCI, Fuddle or Midwest. At least that has been the word around here the past few years.
There is actually a lot of good info on Yanks website about converters and effiency. Of course they are a bit biased
http://www.converter.cc/faq/faq_main.htm
