80tq drag racing- Intercooler reevaluation [long]

[JShadzi at aol.com]

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