[s-cars] Re: wrt pushing RS2 to the edge...

Sat May 10 21:09:02 EDT 2003

Mike,

At 11:24 10/05/2003 -0600, mlp qwest wrote:
>Mihnea -
>
> >From my limited experience, and I readily admit it is both limited and
>probably suspect at best, but on a "BTDT" basis I do feel comfortable saying
>that 28 psi @ 350F+ isn't the same as 28 psi at 225F +/- a degree or two.  I
>further suspect, but again admit that I also don't really know, 28 psi at
>350F+ wouldn't be quite the same, or necessarily better than 26 or 25 psi,
>or maybe even 24 psi at 225F or less.
>
>I think a KKK RS2 K26 pushing 28 psi at anything over, oh say 5,000 rpm or
>so is going to be more likely to be in the former, i.e. 350F + camp, than
>the latter.

Of course I've never said 28 psi should happen at over 5000 RPM, nor should
it happen otherwise than in overboost.  More than 1.5 Bar or about 21 psi
at 5500 RPM is the maximum an RS2 turbo can take, and hopefully I've never
Been There Broke That yet because I've always limited boost correctly in my
programming. Please, what's 350F???? Is that chinese? ;-)
This is why I mentioned about "maximum boost pressure" or overboost figures
and "continuous" or after overboost pressures. 2.0 Bar for a short period
of time in overboost isn't bad for the turbo, if boost is lowered enough
past 5500 RPM.

>Before going off on maximum psi figures, I wish someone had the
>instrumentation at hand to correlate those with an actual charge air intake
>temperature and power perceived",

I have. with 1.8 Bar overboost on an RS2 turbo and 25°C ambient air temps,
the intake air temps in the IM go to around 70 degrees C, and timing is
being pulled off a few degrees (professional secret, I won't say how many).
This is still good for 520 Nm of torque (~380 lb/ft) even though with 15
degrees ambient temps and 55-60 degrees intake temps torque bumps to 540,
and IMHO 20 Nm is something that one's 'buttdyno' can feel. Thus, yes, too
hot isn't really good but it's still better than 1.6 Bar with less timing
retard (because of lower intake temps).

>.... like, as I understand, the ECUs are
>already measuring & doing and report on via "the VAG display group 03, Field
>4 (Bentley Table J 01-76) off the air temp sensor located, I think, in the
>intake manifold after the intake charge passes the throttle plate.  That
>particular sensor is there, and in that specific place for a reason, right?

Yes, it is there in order to correct the following things:

-timing advance at WOT and part throttle
-fuel enrichments
-boost control.

>mlp
>
>~-----Original Message-----
>~From: On Behalf Of Mihnea Cotet
>~Sent: Saturday, May 10, 2003 10:43 AM
>~To: QSHIPQ at aol.com; robert at s-cars.org; pizzoman at yahoo.com;
>~s-car-list at audifans.com
>~Subject: Re: [s-cars] Re: wrt pushing RS2 to the edge...
>~
>~
>~Scott et al.,
>~
>~
>~28 psi *does* gain over 26 or 21 ....
>
>snip
>
>~RS2 torque is 420 Nm at max. 1.4 Bar. I know 28 psi isn't efficient, but
>~for torque no one needs 100% efficiency. So what does your statement of 28
>~psi being almost double the factory boost levels mean? Stock AAN boost?
>~Maybe, okay but what's the point? What's the point in comparing apples with
>~oranges?
>~
>~So, sorry to insist, boost means torque and if timing is properly
>~programmed (sorry to insist on that point again), 28 psi will be a lot of
>~times better than 21, I've personnally BTDT many times.
>~
>~Then, according to several serious tuners here in Europe (what do you say
>~of Dupre Motorsport's racing engine management director during the 90's?
>~He's the guy that helped me with most of what I know about chip tuning),
>~stock rods (including the crappy AAN units which are the worst Audi ever
>~used, i.e. the thinnest) are known to break at 600 Nm crank torque, meaning
>~in excess of 2.5 Bar or PR. This also means that running 30 psi (or 2.0 Bar
>~or PR) won't break rods, except if the timing/fuel chip is done by an a$$
>~and if knock sensor function is suppressed or the threshold raised.
>~
>~Furthermore, maximum boost people are stating doesn't mean anything to me
>~in terms of HP, what boost levels are you guys seeing at 5500, 6000, 6500
>~and 7000 RPM? This is more relevant than maximum boost you see for a few
>~seconds during overboost.
>~
>~HTH and my 0.02 Euro,
>~
>~Mihnea
>~
>~At 12:27 10/05/2003 -0400, QSHIPQ at aol.com wrote:
>~>Hmmm...  I personally think running 28psi on an S-car is silly (I'd say
>~>stupid, but long nerdy posts about effective compression ratios I don't
>~>need).  IMO, you are "safer" increasing the Density Ratio than the
>~>Pressure Ratio.  I'd also venture to say that 28psi probably isn't gaining
>~>any performance over 26psi, which means Motronic is probably saving a lot
>~>of butts here.  I'd also venture to say that the difference between 24psi
>~>and 26 psi is barely measureable.  I'd also venture to say that the
>~>difference beyond 21 psi (RS2 equipped only) comes at a massively
>~>diminishing rate of return.
>~>
>~>I'd further venture to say that rods are known to pop at 30psi, which
>~>means the closer you get to it, the higher the danger.
>~>
>~>All anecdotal "evidence" so noted, 28psi is almost double the factory
>~>boost levels.  For street driving, probably not there long enough to worry
>~>about it.  The long straight and intense 30minute track session?  I'd be
>~>worried about it.
>~>
>~>Boost, specifically Pressure Ratio, is only part of the equation in tuning
>~>for performance gains.  Cars *can* run at maximum parameters, but small
>~>hiccups in any of the ancillary systems can cause catastrophic failures
>~>because of boost.  The good news Joe, is that you can respond in the
>~>"takes one to know one" concept.  Specifically, if it's stupid to run
>~>28psi, in reality, with no other changes, it's really no "smarter" to run
>~>it with race gas.
>~>
>~>HTH and my .02
>~>
>~>Scott Justusson
>~>
>~>
>~>In a message dated 5/10/2003 8:07:52 AM Central Daylight Time,
>~>mik at info.fundp.ac.be writes:
>~>
>~>Joe,
>~>
>~>Someone stating 28 psi without race gas on an RS2 motor is stupid simply
>~>doesn't know what this motor/turbo is. Period.
>~>Then, you can log timing advance and IAT with VAG-COM, I don't remember
>~>where exactly but you can.
>~>
>~>HTH,
>~>
>~>Mihnea
>~>
>~>At 05:00 10/05/2003 -0400, Robert Myers wrote:
>~> >--
>~> >[ Picked text/plain from multipart/alternative ]
>~> >At 08:16 PM 5/9/2003 -0700, Joseph Pizzimenti wrote:
>~> >
>~> >>Well, this was sparked by a rather vocal argument I
>~> >>had with someone about water injection recently.  I
>~> >>was asking his advice and he has experience with B5
>~> >>S4's and 3000GT VR-4's, etc...he basically said I was
>~> >>stupid to run 28psi without race gas.
>~> >>
>~> >>Is there any way I can datalog ignition timing or
>~> >>intake air temperature with VAG-COM?
>~> >>
>~> >>Joe
>~> >
>~> >
>~> >I dunno, Joe, but I betcha you could get an answer on the VAG-COM list.
>~> >
>~> >Mailing-List: list VAG-COM at yahoogroups.com; contact
>~> >VAG-COM-owner at yahoogroups.com
>~> >
>~> >
>~> >
>~> >
>~> >____
>~> >
>~> >I've been wondering...  Who would Jesus bomb?
>~> >
>~> >Bob
>~> >*****
>~> >  Robert L. Myers  304-574-2372
>~> >  Rt. 4, Box 57,  Fayetteville, WV 25840 USA  WV tag Q SHIP
>~> >  '95 urS6 Cashmere Grey - der Wunderwagen   ICQ 22170244
>~> >  http://www.cob-net.org/church/pvcob.htm
>~> >*****
>~> >--
>~>
>~
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