Lag question wrt comp ratio and turbo size (was Re: K24 ...5000cstq)

["The PC Handyman" <pchandyman@intrex.net>]

This seems bizarro-world to me.

The desire for a larger/slower/higher-capacity turbo on your higher
compression engine, and a smaller/faster/lower-capacity unit on a lower
compression engine, seems totally backward from the understanding I thought
I had of the interaction between engine and turbo. What seems evident is
that the k24 has sufficient flow capacity to supply the MC up to the
requirements of the popular boost upgrades. If so, then it's reduced lag
would be awesome, and that would be a gain/gain, and I understand.

As far as using a larger turbo on the higher C/R engine...I would think the
lag would be even worse.  I had envisioned the lower C/R engine spooling up
a big turbo faster, due in part to the low C/R presenting less of a barrier
in the intake tract for the charge air on it's way to the
(also-advantageous) increased volume and low pressure of the low C/R
combustion chambers where the lower C/R engine would also be able to handle
the higher levels of boost better, and make more HP from all that additional
fuel. In short, the lower the C/R is the larger turbo can be/needs to be.

Thus, in my world, the high C/R engine would only like the smaller turbo,
and the low C/R engine would like pretty much any turbo that you put on it,
as long as it would put out a lot of boost.

Can someone please tell me where I'm going wrong?


-Noah
-83 VW 16v Cabbie (Will this project ever run?)
-83 VW Callaway Turbo Rocco (Craving Audi parts)
-87 VW 8v GTI (Will this car ever die? 250kmi)
-87 Audi 5kCSTQ (recently aquired, not featured on my site)
see my cars and read about my obsession...
http://www.members.tripod.com/pchandyman/



Thus spake mike@urquattro.com:
Subject: RE: K24 finally installed in 1986 5000cstq


> Eric_R_Kissell@email.whirlpool.com decided to speak these words:
>
> >I do not yet have an aftermarket boost gauge, so all of my boost readings
> >are from the dash readout. I still need more/better data, but as a first
> >pass my MC-1/k24 gives the following:
> >
> >1.3 bar 1800 rpm
> >1.5 bar 2000 rpm
> >1.8 bar shy of 3000 rpm
>
> Really?  That's interesting.  That is about what i get in my UrQ with the
> MC-1 and the K26.  Of course, that is only in the higher gears, and
> depending on the way i throttle the car, but i can usually get boost by
> about 1500 rpm if i wanted to in the higher gears...  of course, i have
> also figured out how to get the 12lbs of boost with no load on the
> engine, just sitting still...but that is a whole other story...hehe
>
>
>
>
> later...
>
> Michael Sheridan Williams
> San Francisco, CA
> ICQ# 11740998
> 1983 UrQuattro, MC--1.8 BAR, borla, 2B Coilover/Koni Yellows, Delrin
> Bushings f/r, 16x7.5 OZ Mito's w/ Yoko A520's, Cibie H4/H1's, K&N (blah)
> 1985 4000S Quattro, Koni Yellows/Coilover (2B), strut brace, Sport 8000
> Tires, K&N
> http://members.aol.com/daserde2
>
>