[urq] Re: 10 vT EM?

[QSHIPQ at aol.com]

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In a message dated 4/30/02 4:36:40 PM Central Daylight Time, jiipm at sci.fi
writes:


>But I´m answering only for my one, because J does not
>actually have a collector, but 5 runners joined and mine
>has a "long" tube where they join...Just for velocity...

That makes little sense to me.  The way collector/nozzle theory works, is you
have a ratio of runner diameter to throat diameter.  Without purposely
picking a ratio you could actually create more reversion than velocity.  Did
you use any math in your design.  What target did you go after?

>Please, I would like to disagree and ask:
>
>1: What is big K-24 cold side?

hot side wheel stays the same size.  IMS there are a couple choices for the
cold side wheel and housing.  Commonly referred to as the "k24 sport", the
cold side wheel is of a different design and the scroll is slightly larger as
well.  This "upgrade" puts more cfm on the turbo map for a given PR.

>2. You say: not a big difference btw RS-2 and K-24 hot side?
>
>RS2 has 55 mm turbine dia at exducer and K-24 46 mm, IMHO
>it is a big difference. ( 45 mm is for 200-250 HP and 55 for
>250-350 HP ) . IMO K-24 cold side is good for some 300 HP )

You create more backpressure as you increase effective compression ratio or
volumetric efficiency of the motor.  At 2.1 liters and 10v, your backpressure
is acceptable with the k24 running within it's designed MAP.  A stock k24
turbo from the 20vt might be good for 300 peak, but not constant.  Constant
the CFM numbers work out to no more than 280 (being optimistic with the rest
of the DR/VE equation).

>Those small ones work, but with lots of backpressure and not
>too smooth.

What is "not too smooth"?  Backpressure might increase slightly, but
performance increases dramatically.  Doing back to back testing on the k26
water cooled (56.3mm exducer) to the k24 on my 83 urq, smoothness at low and
midrange is much improved, and high end gives little, if anything (again the
restriction is the CIS, not the turbo/EM on the urq) to the k26.
Interestingly Jukka, if you look at the exducers the RS2 has a smaller
exducer than the audi k26 10v turbocharger unit.  So exducer size is a guide,
but hardly THE only reference.

>What You want the engine do: blow the motor or flow the gas :))))

I want the engine, specifically the car, to PERFORM.  IF we use EFI, a lot of
options open up.  USING the CIS as a given, the 10vt urq is really well
matched to the k24, not the k26 that was supplied with it.

>An original 24 cold side is about 43mm, but there is no good
>variations, so the K-26 is a good solution. Here we have seen it
>with 50 compressor/ 55 turbine K-26 as a good one ( RS-2 has a
>K-? with 48/55 ) also a hybrid with K-27´s smallest compressor
>( 53 ) has been succesful. All later 26:s seem to have 55 turbine.
>( I´m now working with a Bimmer 745i with stock 64/53 K-27 )

I played with RS2's with bigger cold sides.  The hot side is well match to
the I5 up to the 400hp mark (you can get a RS2 to flow 700cfm with different
wheel and housing combos).  Beyond that, the backpressure becomes a factor,
but some reduction in that can be found by cutting the hot side wheel.  This
does create a loud turbo whine, obviously Porsche/Audi would accept that in
the RS2 car.  I drove Graydon's efi conversion years ago, and the k27
application of it, definitely had low end performance lag.    WRT 745i, when
you have more displacement k27's work well.  The biggest problem we urq
owners have, is 2.1L of displacement is a given, and to most, so is the CIS
and the IC.  WITH those givens, the k24 is most acceptable, I dare say, even:
 Recommended.

When you venture into the 20vt, things change some, BUT, you must eliminate
the biggest restriction in the system to really dictate a turbo larger/better
than the RS2; that being the MAF meter.  Ditching the motronic is a huge pill
to swallow, and modifiying it at a reasonable cost also appears to have a
large bill attached to that hat.  Up to 400hp, the RS2 performs well, which
is about the max of the MAF meter anyhow.

What you and Javad appear to be doing is going to the restrictions, then
coming back to the turbo.  Great!  Right now, I have Javad's EFI in my shop,
but working it to handle a CIS turbo to EFI turbo swap (as apposed to CIS n/a>
EFI turbo swap it was designed for).  After we get that running, I might
consider a turbo swap, but given the MAP of the RS2 turbo, the EFI with a
mongo intercooler (the app I'm working on) appears to be a fine 10vt
expectation.

>I started this thread, just to get some other ideas, than mine for a
>fiver project, but looks like we are "quite" far away;))

No problem, we are only "far" away because there are very few that are doing
EFI conversions to CIS turbo cars.  Once we can get that done, quite a few of
us would be happy to get closer and share EM BTDT.

HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago Illinois