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86.5 Turbo
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Discussion Starter · #1 ·
If you dyno your car with a 3.91;1 rear end and say your results were 280hp 325tq. If you swapped in the 4.30:1 and put it back on the dyno what numbers would come out. Would the tq be the same or higher? I believe it would be higher because tq is multiplyed be 4.3 instead of 3.91. let me know if I am right or smoking crack. The reason why im asking is because I used to have the 3.91 and now I have the 4.3 and it feels faster.
 

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Dr. Jeff Lange
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Torque to the wheels is higher, but speed is lower, so power is the same. Dyno measures power at the wheels, then uses engine RPM to calculate the torque.

Gearing can reduce or increase torque, but power is not changed by gearing (aside from frictional losses, etc).
 

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boost freak
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supraboostin said:
no sir. there are a variety of factors to consider- tq multiplication, engien loading, etc. from my exp, the difference between a 4.30 and a 3.73 is close to 400 RPM- the 3.73 spools 400 rpm SOONER due to increased engine loading. tq is down a bit (maybe 5%?), but spool is the largest factor.
 

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Dr. Jeff Lange
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drjonez said:
no sir. there are a variety of factors to consider- tq multiplication, engien loading, etc. from my exp, the difference between a 4.30 and a 3.73 is close to 400 RPM- the 3.73 spools 400 rpm SOONER due to increased engine loading. tq is down a bit (maybe 5%?), but spool is the largest factor.
Agreed. Turbos add even more complication because engine load is higher on the 3.91 than the 4.30.
 

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7m power
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drjonez said:
no sir. there are a variety of factors to consider- tq multiplication, engien loading, etc. from my exp, the difference between a 4.30 and a 3.73 is close to 400 RPM- the 3.73 spools 400 rpm SOONER due to increased engine loading. tq is down a bit (maybe 5%?), but spool is the largest factor.
thank you sir,i thought i had read somewhere that changing the gears wouldnt increase or decrease power but i guess i was wrong
sorry for the wrong info
 

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drjonez said:
no sir. there are a variety of factors to consider- tq multiplication, engien loading, etc. from my exp, the difference between a 4.30 and a 3.73 is close to 400 RPM- the 3.73 spools 400 rpm SOONER due to increased engine loading. tq is down a bit (maybe 5%?), but spool is the largest factor.
I think you brake boost on the dyno to get ur curve adam...you cheater! :)

jk, but thats a real good point about lower gearing and turbo spooling. :)
 

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all i can tell you is with 4.3 gears you get no traction in 1st and 2nd gear..too much wheel spin.

thanks dr. jones for the info also.

charlie
 

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boost freak
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NegativeGeForce said:
I think you brake boost on the dyno to get ur curve adam...you cheater!...
heh. i wish. just wait til you see some dyno results w/the AEM advancing the heck out of timing out of boost....

7mgtemk2 said:
all i can tell you is with 4.3 gears you get no traction in 1st and 2nd gear..too much wheel spin....
heh. better add 3rd to that list and 4th if there is a hint of moisture. ;)

7mgtemk2 said:
...thanks dr. jones for the info also.

charlie
np man, good luck!
 

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I was the wondering what different 60 ft time everyone has experianced with the two different rear ends as well as slick size?
 

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well shit don't the mkiv have similiar tranny gears as our r154 (talking about the v160) and running a massive 3.2 in the rear end? They have no problem cutting 1.5 60 ft times. So what is the deal?? :wtf:
 

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Dr. Jeff Lange
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No, the V160 does NOT have similar gearing to ours, with it's 3.27 rear end, the gearing is almost the same as ours with 3.73/3.91.


V160 with 3.27:

1st: 12.52
2nd: 7.71
3rd: 5.49
4th: 4.28
5th: 3.27
6th: 2.58

R154 with 3.73:

1st: 12.31
2nd: 7.27
3rd: 5.00
4th: 3.73
5th: 2.79

The V160 with the 3.27 rear end has shorter gearing from 1st - 3rd than the R154 with 3.73 has. Only from 4th-6th does it get it's taller gearing than the R154.
 

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Flying Dutchman Pilot!
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My experience with the 4.30 has been you shift before the 60' mark, while with a 3.90 you get passed the 60'mark in 1st, so comparing 60's isnt apples to apples.
 

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86.5 Turbo
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Discussion Starter · #15 ·
ok, so with my 4.30's I take off the line much faster then a 3.73 does. I cant tell if there is a difference in spool but I know it revs up faster which gets me into my powerbad quicker. This makes me feel like there is less lag.

I will see what happens when I get to the track this weekend.
 

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Escaped from infinite lag
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With my 4.3 rear and 16psi on the stock ct the car on a dry day is insane. If you launch too hard you get no traction at all but if you can get a decent launch and feather the clutch for light to light racing the 4.3 is much better IMO.
 
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