[s-cars] Why audi I5 started as 2.1 liters - Audisport Historical Trivia

[James Bufkin]

Jimmy and Scott,

I'm not going to support the idea that we are completely blind about what 
Turbos Audisport used and its misleading people to suggest that the K26 was 
possibly as prominent as the K27 in the Audisport program because "we don't 
know".   Put simply its not even close.

The manifolds... Have you ever seen an audsiport tubular manifold with a 
K26 flange?   I've seen lehmann 10V manifolds.  They had a K27 
flange.  Audisport used a Sport Quattro cast manifold with a K27 
flange.  Lehman 20V tubular manifolds had a K27 flange.

2ndly.  The sizes of K27 hotsides. #7 to #13 offers a much more usuable 
range of sizes along with a more robust shaft and bearing system.   It also 
allowed the fitment of K28 and K29 compressor housings.   I've also read 
what you described.  And there is certainly no way of knowing exactly what 
turbo was used on what car.  Its a hodge podge of stuff.  However, that 
doesn't mean we should assume they used K26s because they could and it 
suits someone's arguments and beliefs about an RS2.  Why not then argue 
that they used K24s!?!?!   It means we should all look at the evidence on 
hand.  That evidence is period pictures (which all show K27s on the 20V 
cars).  Parts (which are K27 flanges).  Actual Works cars (with K27s).  Its 
certainly possible they might have used a K26 in a series that required 
restrictors. Its also very possible they used K26 turbos on a very early 
10V car although I haven't seen any evidence of that.

My challenge.  Find me an Audisport 20V car with a K26 turbo.  I can 
produce dozens upon dozens with K27s.  MTM, Lehmann, Bruno, Buffum, 
Sprongl, Sutton<--All K27 based.

I'm not bashing the RS2.  Its a great turbo.  I do have an issue with those 
who say its a good track/race turbo.  Its not.  too small for prolonged use 
at 4000-7000 rpm so its not the end all be all turbo some say it 
is.  Others have already done the math(correctly) and seen what its doing 
at high RPMs.   And thats why you just don't see K26s in the 20V race 
cars.  Its a GREAT street turbo.  I'd use one in a heartbeat for that 
purpose.

Regarding Garret. I said before and feel compelled to say it again.  The 
Audi R8 uses a twin Garret turbo.  That speaks for itself.   So.. If not an 
RS2 then a larger Garret.   K27s don't even play into the equation anymore 
when going for pure performance.  Technology has moved forward.
There are still some great 20V cars out there with K27 based 
turbos.  Especially in Europe where the Garret craze isn't so predominant 
and they can easily get modern K27 turbos with titanium wheels and water 
cooling.

My opinion
James Bufkin


James E. Bufkin, P.E.
Bufkin Design and Engineering, inc.
2309 West 8th Street
Austin, Texas 78703
512-236-8070
fax 512-480-5927