80tq drag racing- Intercooler reevaluation [long]

[ed armstrong]

Hmm, what makes the S4tt setup work so well ?? Its
intercooler is smaller than yours, right ? Maybe your
boost was set too high for these conditions.

--- JShadzi at aol.com wrote:
> Well, I drag raced on Sunday at Buttonwillow, had
> fun, but learned something 
> about the car, here are the specs:
> 
> Time: 10am to Noon
> 
> Temp: 90-105F(by 11:00)
> 
> Conditions: Sunny
> 
> Track condition: quattro, need I say more?
> 
> Clutch: Slipping, so I was easy on it-but not so bad
> that it could not do 15 
> consecutive runs, and still feel fine afterwards
> (stock 240 mm 7A BTW)
> 
> Detonation: Little to none, but I am sure the 105
> Oct. helped...
> 
> Boost: 17.5psi
> 
> ET: 15.8  (I know, I know, let me explain...)
> 
> Trap speed: 96 mph (I will talk more about this too)
> 
> 60': 2.2 sec.
> 
> # runs: 15 in 1.75 hr. (basically a run every 6 min
> or so)
> 
> Ok, so my ET sucked, and was way off my "street
> estimates".  I really figured 
> I would be in the low 14's, or mid 13's.  Despite my
> best efforts at tuning 
> the fuel curve, I remained consistent within 2/10th 
> of a second on all 
> completed runs, so at least I was consistent!
> 
> Here is what was happening-I was getting a great
> launch, I was never 
> "outlaunched" all morning, acceleration thru 1-2 was
> strong, what I expected, 
> 0-60 felt in the 5 second range.  But, the top of
> 2nd would get real soft, 
> and by 3rd gear, the car would essentially NOT
> accelerate.  By the 4th gear 
> shift I was crossing the 1/4mile mark, usually in
> the mid 90's.  To give you 
> an idea, I put myself up against a chipped S4tt for
> a few runs-typically, I 
> was 2-3 carlengths in front of him by 2nd gear, but
> once into 3rd he would 
> accelerate past me to finish about 4-5 carlengths
> ahead, very frustrating!  
> So, after my session, I was perplexed and
> dissapointed-cars are either fast 
> or slow for a reason, and my car is not slow, so I
> needed to find the reason.
> 
> Obviously, heat was a factor, I have done all the
> driving and tuning on my 
> car in the SF region, where temps. have rarely
> cracked 75F all summer, so the 
> car is a rocket, but in the 100F+ temps, I
> definitely felt it.  I began 
> wondering how much my (what I originally though)
> huge IC was really cooling 
> my intake charge?  A few test runs revealed a huge
> problem...in a run from 
> 40-80mph, my intake charge went from 41C to 91C! 
> Over a doubling in temp, 
> and imagine what it was doing in a full 0-95mph run.
>  One indication of this 
> was that I was noticing my boost falling from a max
> of 17.5 in 2nd, to below 
> 14psi in 4th.  A few hours of data logging on the
> way home revealed 
> incredible rates of heat soak whenever boost was
> present, and the rate was 
> the same, whether ambient was 15C or 50C
> (obviously).
> 
> One mistake I likely made before the race was
> turning boost up.  Looking 
> back, I bet my ET would have been much faster with
> only 10psi, leaving the IC 
> in a heat range that it could more easily manage. 
> Sitting in 100F in the 
> staging lane did not help either, an IC mister would
> have gone a long way to 
> help this (or one of those computer dusters in a
> can).  An interesting thing 
> to note, a trap speed of 96mph is more indicative of
> a car in the mid-14's, 
> for example a WRX (also all wheel drive) does a 14.4
> @95mph
> 
> SO, I will be upgrading the IC here real soon, my
> plan is to keep the IC I 
> currently have, but add a second identical core to
> the bottom of it and 
> modify the endtanks accordingly.  Thus, my new IC
> will be 18Lx14Hx3"Thick (up 
> from 7" high), and will flow over 800cfm.  Much
> "modification" will have to 
> be done to the front core support, I will be sure
> the post pictures and info 
> when it is all done.  
> 
> Another consideration- I believe I am running the
> stock k26 close to its 
> surge limit, where efficiency is poor and thus temps
> are high (the reason the 
> air-cooled Porches used a massive K27 was to keep
> the turbo in a high 
> efficiency range, thus reducing heat).  I am looking
> at possible T3/T4 combos 
> and a tube header in the future.
> 
> Any thoughts are welcome, gotta love these
> "experiments".
> 
> Javad Shadzi
> 80tq.com


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