# [Audi20V_Kruemmer] RE: [s-cars] Question about compression ratiosand tuning - More 20vt

Paul Gailus gailus at mindspring.com
Thu Feb 5 01:35:06 EST 2004

```Interesting site, Mike.

I think you may not have divided by the factor 2n
as needed in the formula:
Z = (N**2) S (1+ 1/(2n) ) / 2189

Instead, I think you left the "n" on top as in:
Z = (N**2) S (1+ (1/2)n ) / 2189

Using the first formula you get:

7000 rpm @ 144/86.4mm -> 1.667 ~> 109,400 ft/sec^2
7000 rpm @ 144/95.5mm -> 1.508 ~> 112,100 ft/sec^2
7000 rpm @ 150/95.5mm -> 1.571 ~> 111,000 ft/sec^2

Note that (111,000 ft/sec^2) / ((32ft/sec^2)/g)  = 3470 g's
of acceleration.

Paul

----- Original Message -----
From: mlp qwest <mlped at qwest.net>
To: <Audi20V_Kruemmer at yahoogroups.com>
Cc: <s-car-list at audifans.com>; <QSHIPQ at aol.com>
Sent: Wednesday, February 04, 2004 10:49 AM
Subject: RE: [Audi20V_Kruemmer] RE: [s-cars] Question about compression
ratiosand tuning - More 20vt

> A couple of other sites of varying sophistication dealing directly or
> tangentialy with the matter:
>
>   http://victorylibrary.com/mopar/cam-tech-c.htm is a site I originally
came
> across in looking for better information on the effects of connecting rod
> ratios in the "stroker" motor.
>
> Going back to a previous thread on piston speed, the victorylibrary has
some
> interesting material on the effects of long vs. short rod on piston speed
> vs. maximum accelerations.
>
> 7000 rpm @ 144/86.4mm -> 1.667 ~> 139,595 ft/sec^2
> 7000 rpm @ 144/95.5mm -> 1.508 ~> 147,615 ft/sec^2
> 7000 rpm @ 150/95.5mm -> 1.571 ~> 150,259 ft/sec^2
>
> But I suspect something is wrong with my math, or interpretation of
Victory
> Library's formula, if I assume the longer rod ratio in example #3 with the
> Eurovan 150mm c-to-c rods ought to have returned an acceleration less than
> the that of the 144/95.5mm rod combination.  In any case, all the values
> apear to be well above Victory Libraries suggested "100,000 ft/sec^2"
Gotta
> love those motorcycle guys  :-)
>
> Also there's  http://www.mix-net.net/~red/uccr.html  -
>
> Mike

```