Why does Stage 1+ ping... Re: [s-cars] Octane and Unleaded Race Gas Article

[Keith Maddock]

Perhaps the MTM Stage 1+ should carry a minimum octane requirement of 93 octane.  I think this would probably also apply to the similar power-output level IA Stage 3+.  I'll call them both "Stage +" upgrades, unless Ned wants to pipe up with a disagreement..

Based on the info I have gathered over the past couple years, its my understanding that these "Stage +" upgrades are *really* pushing the limits of the stock turbo.   You're running the little K24 past its peak efficiency range, which means it's creating a lot more heat than a larger turbo to acheive these high boost levels.   (Nothing comes for free...)  Of course, you do enjoy the quicker spool-up as a reward.

With this extra heat, you're taxing your intercooler quite a bit, which I think we all will agree is one of the weaker links in the S4's turbo system (especially if you do not have your undertray installed, in my personal experience.

All this extra heat, coupled with the very advanced ignition timing of the "Stage +" is a very good recipe for pinging on anything less than high quality, high octane gas.

For people in warm areas without consistent, good supply of 93+ octane gas, perhaps you should stick with "Stage 1", and if you desire further power gains, go to a larger turbo that is more efficient at that power level.  OR perhaps install a PISS system or similar water injection / water spray system.

For a slightly less elegant approach, my experience during OneLap showed that the "octane booster" in a can goes small way towards reducing ping when your gasoline supply is compromised...  I would only consider this to be an emergency solution though.

Hal's suggestion of richening up your mixture may have some merit.  Personally  I'd start with the adjustable FPR before the larger injectors, as that would allow much finer control of probably what needs to be only a small increase in the amount of fuel...  One has also to be very careful of running too rich, I've heard of a lot of plugged cats in modified UrS's when they start running combinations of turbos, injectors, MAF's, and FPR's that arent an exact match for the software calibrations in their ECU...  Has anyone with a pinging "Stage +" car checked their ECU DTC codes for the "mixture out of range code" ?

Just my 1/50th of a Euro on the subject as a bystander... :)  (damn near the same as 2 cents lately, much to my dismay after transferring $23k US over here last week for my pending purchase of a 968CS)

Keith, pondering pinging in der fatherland, Maddock
93 S4 with IA Stage 4 SW, IA RS2 Hybrid turbo in Portland, OR
RIP:  91 200q20v with "Stage 1" and stock turbo (no pinging unless I bought gas *IN* Detroit)
94 968CS hopefully soon in Koblenz, Germany..



****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> Joseph Pizzimenti <pizzoman at yahoo.com> 23:32:29 07.09.2002 >>>
How about a simple aquamist on the outside of the
intercooler?  Shouldn't cost too much and should keep
you out of detonation.

-Joe
--- Rob Pecsar <rpecsar at pacbell.net> wrote:
> Igor and Joe,
>
> You are right, we don't anything better than 91
> octane in California at
> commerical outlets. I ruled everything else out that
> I could as the
> source of pinging - plugs, fuel filter, basic engine
> diagnostics. All
> checked out fine. So I added 5 gallons of Union 76
> 100 octane race fuel
> to my normal 91, putting me at ~93 octane. Result is
> zero pinging.
>
> Next step is when the tank is half full, I'll top it
> off 91 in order to
> test out 92 octane. At $6.00/gallon its not the
> cheapest solution, but
> at least I can finally feel the result of the MTM
> upgrade without
> damaging the motor.
>
> Do you think an intercooler cleaning will reduce the
> pinging? RS-2 E.M.?
> I guess anything to drop the combustion temp will
> help. Seems like
> alcohol injection may be the cost effective way to
> control pinging while
> maintaining the advanced timing that I paid for with
> the MTM
> upgrade...my old TAP setup doesn't seem so bad in
> hindsight.
>
> Rob Pecsar
> 92 S4
>
> Igor Kessel wrote:
>
> > Rob Pecsar wrote:
> >
> > > 92 S4 MTM 1+ with no ping on 93 octane in
> California
> >
> > Bob,
> > I didn't know you had anything above 91 in
> California?
> >
> > And what's the deal with "no ping" anyway? Water
> injection? Toluene?
> >
> > --
> > Igor Kessel
> > two turbo quattros
> >
> > 97 S6 MTM 1+ pinging away on 93 octane in
> Pennsylvania
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