Stroke, bore, cam & RPM's

[Tim]

MK, you have good advice from Hank and Taka. Two more cents: The bigger the
bore, the bigger -- and consequently heavier -- the pistons. The heavier the
pistons, the more stress on the rods, and -- you guessed it -- the lower the
safe RPM ceiling. And yep, you get bouncy valves (float) with higher RPM and
higher cam lifts, which calls for stronger springs (as Hank wrote), which
calls for, often as not, hardened valve seats to keep the stronger springs
from slamming the valves up into the head... and changing cam profiles
without a rocket science degree usually ends in a tradeoff between power and
driveability. It's an interdependent little can of worms.. :-)

Cheers, Tim

93, er, acura (stunt double for dear departed 86 4000csq totaled by 68 m
benz and soon to be trade-in for another q)

> --__--__--
> 
<thread --> -->

> From: BBBurban at aol.com
> Date: Sun, 13 May 2001 10:30:49 EDT
> Subject: Re: Stroke, bore, cam & RPM's
> To: quattro at audifans.com
> 
> I believe that valve float can be avoided with stronger springs if I am not
> mistaken... In addition to this with a higher lift cam a set of roller
> lifters will be able to follow the cam lobes more easily.
> 
> Hank 90q20v 
> 
> uneducated 2 cents
> 
> --__--__--
> 
> Message: 7
> From: "TM" <t44tq at mindspring.com>
> To: "MK" <mklovelady at home.com>, <quattro at audifans.com>
> Subject: RE: Another question
> Date: Sun, 13 May 2001 10:31:29 -0400
> 
> MK, please post in plain text rather than HTML. Thanks.
> 
> As for your question, I think it is a known fact here that you
> will need to significantly upgrade the intercooler, turbocharger
> and the fuel system in order to get to 300hp on the 10v engine.
> 
> The only one I know who has done this has a hybrid K26 hot/K27 cold
> turbo and IIRC, Merc 6.9 CIS injectors and custom IA programming.
> 
> I would not bore the engine out for strength reasons and I would maintain
> a close to stock CR as well, if you want to go high boost.
> 
> You don't really need to do much w/ the cam either- just make sure the
> engine is properly rebuilt w/ new rings, valve seals, etc. and strengthen
> the cooling and fuel systems before turning up the boost.
> 
> Anyone know what the max boost is for a stock K26 w/o exceeding the
> efficiency limits?
> 
> If I ever do it, my 3B engine will get a larger turbo, better radiator,
> intercooler and oil cooler and larger exhaust if I am to get big power
> out of the car.
> 
> Taka
> 
> 
> -----Original Message-----
> From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
> Behalf Of MK
> Sent: Saturday, May 12, 2001 11:14 AM
> To: quattro at audifans.com
> Subject: Another question
> 
> 
> If you recall I wanted to take the turbo charged engine out of my rear
> ended 1985 5000 S Turbo and place it in the 1986 4000 CS Quattro. I am aware
> of the site with the change over to turbo but my question is this.
> I want to take it as close to 300 horse as possible, planning on a
> complete rebuild I had noticed some comments on the size of the bore
> affecting the RPM or on how high the RPMs will go.
> I guess is can the wrong piston, bore and cam affect the rpms? This is a
> do it my self because I cant afford a mechanic type thing and I want to do
> it right any input would be appreciated.