Missing Gear Ratio...
#1
Drifting
Thread Starter
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I'd always assumed that Auto boxes didn't have the equivalent of first gear in a manual box, but when I decided to check the charts I found I was completely wrong:
928 Transmission Info
MPH per 1000rpm (S4 Man vs S4 Auto)
Gear..........Man...........Auto
1.................7................7
2...............11...............11
3...............15
4...............20...............19
5...............27...............28
Auto boxes are missing the equivalent of 3rd gear - weird...
928 Transmission Info
MPH per 1000rpm (S4 Man vs S4 Auto)
Gear..........Man...........Auto
1.................7................7
2...............11...............11
3...............15
4...............20...............19
5...............27...............28
Auto boxes are missing the equivalent of 3rd gear - weird...
#2
Three Wheelin'
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Hi PAUL ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
My S2 Auto does....44 in first....77 in second....117 in third and 160+ in top![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
There is something weird about that table...but I cannot quite figure out what lol
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
My S2 Auto does....44 in first....77 in second....117 in third and 160+ in top
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
There is something weird about that table...but I cannot quite figure out what lol
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
#3
Drifting
Thread Starter
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Hi Brett
Your figures approximately equate to the shift up points for a A28.02 box under kick down, which you will find on the same page on the link I posted.
MPH per 1000rpm on your on your box is roughly:
8.5
13
22
31
Your figures approximately equate to the shift up points for a A28.02 box under kick down, which you will find on the same page on the link I posted.
MPH per 1000rpm on your on your box is roughly:
8.5
13
22
31
#6
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Hi Paul ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Mine is a 28.08 box (last of the S2s) which is interesting as it gives me 11 mph better than an S4 at top of third gear...(due to diff ratio)
I wonder why they lowered the ratio for S4s...and also raised the rev limit I think....I would assume they raised the rev limit to offset the diff ratio alteration.....but WHY alter the diff ratio in first place???
Any ideas anyone ??
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Mine is a 28.08 box (last of the S2s) which is interesting as it gives me 11 mph better than an S4 at top of third gear...(due to diff ratio)
I wonder why they lowered the ratio for S4s...and also raised the rev limit I think....I would assume they raised the rev limit to offset the diff ratio alteration.....but WHY alter the diff ratio in first place???
Any ideas anyone ??
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
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#8
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My '88 S4 A/T shifts at 5500rpm in first, so no help there. 2nd is good to a documented 94.25mph while banging the rev limiter ('87 S4 A/T at the drag strip), and third is 145mph (according to the ever so accurate stock speedo). Never held it flat in 4th to top speed.
#9
Drifting
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Originally Posted by FlyingDog
Your rounding is a little off, and they're doing some funky math.
I'm still interested in how Auto boxes can cope without the equivalent of a manual's third gear.
#11
Race Director
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Originally Posted by UKKid35
I'd always assumed that Auto boxes didn't have the equivalent of first gear in a manual box, but when I decided to check the charts I found I was completely wrong:
928 Transmission Info
MPH per 1000rpm (S4 Man vs S4 Auto)
Gear..........Man...........Auto
1.................7................7
2...............11...............11
3...............15
4...............20...............19
5...............27...............28
Auto boxes are missing the equivalent of 3rd gear - weird...
928 Transmission Info
MPH per 1000rpm (S4 Man vs S4 Auto)
Gear..........Man...........Auto
1.................7................7
2...............11...............11
3...............15
4...............20...............19
5...............27...............28
Auto boxes are missing the equivalent of 3rd gear - weird...
These are the about the same #'s I came up with, but yours are a touch low.....my auto will do over 50mph in 1st, 80ish in 2nd, 140 in third & ??? in 4th, but mine does shift at 6200rpm in every gear too...so if a 5 speed if driven without third gear it is the same as an auto (for 2.20 S4's)......once the 5 speeds and autos had different rear ends then things get different....
#12
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Originally Posted by mark kibort
just give me the ratios and ill give you the speeds at 6500rpm
S4s with 2.2 manual is:
55mph
80mph
115mph 4.5:1
155mph 3.2:1
220mph 2.2 :1
MK
S4s with 2.2 manual is:
55mph
80mph
115mph 4.5:1
155mph 3.2:1
220mph 2.2 :1
MK
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Ratios...
1st = 3.676
2nd = 2.412
3rd = 1.436
4th = 1.00
The rev limit is the bad point here...on my S2 the rev limit is set to 6375 revs (unalterable) on an S4 auto I think its 6500 ?
Under hard kickdown... my autobox changes up at 5900....with a final drive ratio of 2.357...
Under hard kickdown PLUS Nitrous....I can actually hit the rev limiter (not a good idea) because the engine is increasing revs so fast it sort of beats the change up mechanism....
All the best Brett
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