STR on converter question?
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 85
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STR on converter question? My next mod is going to be a Torque Converter and 3:73s , they will be installed around the same time. My question is About the STR what is a good STR on a 3500 stall. I dont really understand what the STR means so I dont want to order a Converter not knowing what I got. The Converter I have been leaning towards getting is a TCI 3500 stall and the str is 2.5:1. My car is not a daily driver but its also not a car running at the track all the time either. I want a converter that is gonna get me going from a stop but I also want 1 to hold its own from a roll 2. I see most guys who post on here have a str around 2.1-2.2. Can some1 explain?
The higher you go, the looser it will feel. 2.5 is what I had planned on in my 99 Z with a th350. It'll give plenty of punch while still feeling pretty close to stock...But still a bit looser.
2.5 will be good all around, lower than that feels too close to stock and higher than that will start to feel really loose. I think my mustang's is around 3.0 by the feel of it.
2.5 will be good all around, lower than that feels too close to stock and higher than that will start to feel really loose. I think my mustang's is around 3.0 by the feel of it.
Originally Posted by 2002LS1Z
3600 2.5 STR is what I just put in mine which is a daily driver and sees the track every few months.
STR stands for static torque ratio. it is basicly how much a torque convertor multiples the torque as the engine is approaching stall speed.
what this means is that the higher the STR the harder the hit to the tires. so you will spin more with a 2.5 STR than a 2.2
when people say "looseness" they mean how much the convertor slips as it approachs stall speed. the higher the STR the tighter the convertor is.
also, with any convertor, you will lose a slight amount of top end(ex. low dyno numbers on A4 cars) but the other attributes of the convertor more than make up for this.
if i got any of this wrong, feel free to correct me.
what this means is that the higher the STR the harder the hit to the tires. so you will spin more with a 2.5 STR than a 2.2
when people say "looseness" they mean how much the convertor slips as it approachs stall speed. the higher the STR the tighter the convertor is.
also, with any convertor, you will lose a slight amount of top end(ex. low dyno numbers on A4 cars) but the other attributes of the convertor more than make up for this.
if i got any of this wrong, feel free to correct me.
Thread Starter
Staging Lane
Joined: Mar 2006
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Will a converter with the STR of 2.5 still be able to get good traction on some drag radials and cut the60ft time down?Also does your trap speed at the track tend to go down with a converter? Overall do you think its better to get a lower str than 2.5 maybe a 2.1 or 2.2.
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TECH Fanatic
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From: Grand Rapids, Michigan
Originally Posted by SRpwred240
Will a converter with the STR of 2.5 still be able to get good traction on some drag radials and cut the60ft time down?Also does your trap speed at the track tend to go down with a converter? Overall do you think its better to get a lower str than 2.5 maybe a 2.1 or 2.2.
It depends on the effiency of the converter, but usually you won't drop any mph but some people with PI converters tend to lose a little mph but still turn respectable 1/4 mi times.
If you are really concerned with roll racing a lower STR might be for you (more efficient up top), but it will feel a bit looser than one with a 2.5.
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Originally Posted by SRpwred240
Will a converter with the STR of 2.5 still be able to get good traction on some drag radials and cut the60ft time down?Also does your trap speed at the track tend to go down with a converter? Overall do you think its better to get a lower str than 2.5 maybe a 2.1 or 2.2.
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 85
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I just emailed Fuddle and TCI to see what they recommend. I told them I want a converter to cut my 60ft times and be able to hold its own from a roll race too, since it seems like most of my races do come from about a 20 50mph roll on the street.
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Joined: Mar 2004
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From: Australia
I currently run a Fuddle 3400/2.1STR and its about as big as I would want to go for a DD with major city duties. The best all round converter for DD is 3000/2.0 with respectable track performance IMO. Dont go less. On a big-*** GTO like mine add 200RPM flash stall.
Thread Starter
Staging Lane
Joined: Mar 2006
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MNR-O How do you like the str of 2.1 do you get off the line pretty good with that 2.1str and how does your converter do from a roll race,and if you dont mine me asking how much did you pay for your converter from Fuddle
STR stands for Stall Torque Ratio. Basically, STR is torque multiplication. If a car has a higher STR, it will feel tighter on the street because the converter is multiplying the input torque by a higher number. It will also give a harder punch out of the hole. STR is created by two components inside the converter moving at different speeds. Shortly after launch, those components reach an equal speed eliminating STR completely.
a 2.5str and 3.73 gears will destroy any tire you throw at it on the street from a dead stop. Some A4 guys get gears to tighten up their converter. IMO, you need to match the str of the converter to your gear ratio.
If you want 3.73 gears, then a 3600 stall 2.0-2.1 str verter is good for you. You'll still get that kick down low with 3.73 and maintain better hp efficiency up top with a 2.0 str.
If you want 3.73 gears, then a 3600 stall 2.0-2.1 str verter is good for you. You'll still get that kick down low with 3.73 and maintain better hp efficiency up top with a 2.0 str.
Don't do a gear change yet, get used to the converter first then if you want, add gears later. You will have severe traction issues if you do both at the same time and are not used to it. 
i have a 3600 fuddle with a 1.8 str, it feels a bit loose, but still hits hard off the line and does very well from a roll. im thinking about getting some 3.42's or 3.73's to tighten it up a little.
