because of heat soak? When the car is not fully warmed up I sense that the car is much quicker than after I've been on the road for over 15 minutes or so. Anyone been to the track and measured this?

 

Probably have better luck posting that on the S4 forum - or emailing NASA directly

 

with the A6. I suspect that the S4 might be worse than the A6 because of a slightly smaller engine bay.

 

If you are moving in traffic there should be no heat soak at all. It becomes a factor when there is little/no air moving over the intercoolers. In other words, when you are at a stoplight there will be some heat soak. The excess heat should be gone less than 1 minute after you leave the light.

Having said that, it would be nice to measure 1/4 mile times with the post-intercooler intake temp. logged, perhaps via VAG-COM. I am curious to know how much difference exists between intercoolers at 140°F and intercoolers at about ambient temp. Would it mean 1 tenth in the 1/4, 3 tenths, more?

 

They are vented in front, right behind the intercoolers, presumably to allow more flow through the intercoolers. So they might unsoak faster.

Has anyone investigated trying this for our cars?

 

When 0-60 runs were done the best times occurred when the temp was between 175 and 200. Now as the car got hotter the times were slower.
Now when I got the car up to its operating range of 225, and would just let it sit for a bit then re ran the car the times were .15 to .18 slower 0-60mph(timed with gtech). Since I did not have any air moving I attributed this to heat soak. Its better to at least drive the car around to get the air flow.
At the drags you would run a race then get back in line. The line doesnt move very good, so your car just sits there. This will affect your time times by as much as .20 to .30 in the 1/4. We found it good to spray water to hopefully help battle the heat soak. After we did this, the next runs where not affected by the heat soak problem. In fact in three straight runs with ~15-30 minutes sitting in line the runs where in order 14.06, 14.05 and then 14.02. I was laughing doing this because Nasaracer(S4) was doing the spraying and he couldnt really find the opening and was just spraying everything under there( I believe easier on the S4)!!!
On runs that we did not spray, I noticed that times dropped by an average .2 to .3. I tried to be as consistent as I could with how I was driving so that I could attribute this to the heat soak.
Just some gut feel and some timed runs make up this WAG(wild *** guess) since I did have any temp measuring equipment. I will get with Nasa to get his opinion on all this. Maybe he can shed more light on it.

 

After the car has been running about 5 minutes it just feels sharper at the stoplight launch than when it has been running for over 15 minutes. Most of my driving is in town and in moderate traffic (lots of lights too) so I think I am affected by heatsoak. I actually find myself compensating for this when I first get in the car. I try to be light on the throttle because it seems to have more kick when cool. Once it warms up I find myself being a little more aggressive because it no longer has that kick.

I will need to fight the urge to water spray at stoplights when sitting next to the guy with the Folgers can :P

 

I've taken the front grills off to expose the fogs and the intake ducts to the intercoolers but I haven't looked behind them yet.

 

Turn the wheels right, then forward in the driver's wheel well. You'll see "gill slits" in there. Supposedly it provides an outlet for all that ram air that comes in the front over the intercoolers.

Perhaps our car is designed differently and doesn't need it. Or perhaps we could benefit from it.

 

my last outing to the track, I was trying to beat my low ET of 14.4. I drove to the track direct from work, not much traffic, only slowed to below 40mph about 2-3 times. Signed the release forms, went thru tech inspection, got my helmet, went to staging lanes. Car was never shut off, it had been running for over an hour straight. I ran a 14.58 @ 95 and change I believe.
Not bad on a hot motor. I went back to the staging lanes, and had to wait about 10 minutes for the next run. I shut the engine off. Restarted about 2 minutes and went to the starting area. As I was blipping the throttle in the staging area, I knew this was gonna be a bad run, there was tons of "turbo lag" and the throttle was extrememly sluggish.
I ran a 15.1 @ 92 mph, showing that I was definetely missing a few ponies from the equation.
I made another run about 15 minutes later, and that one was a 15.3, getting slower with each run, I assumed this was because of the hot engine.
A proper cooldown (about 20 minutes with the hood up) netted me the runs I was used to, another 14.58, followed by a 14.6. Keep in mind that it was very cold this night, in the high 30's, but the engine had built up enough heat to slow it down.
I noticed over the past week that the heat buildup affects the engine in a big way, since It's been in the high 80-'s, low 90's in NYC. Last night for example: I got home from work, and proceeded to drive around the neighborhood putting up flyers on telephone poles. After about 30 start and stops (over about 30 minutes) the engine was good and hot.
I then proceeded to drive to my fiance`s house. As I merged onto the expwy, and mashed the throttle. The throttle response was best measured with a hourglass. About 2 seconds, and you would get a feeble surge of power. Still enough to accelerate the car well, but much less than usual.
5 minutes on the expwy (at about 60mph), and I shifted to 4th (like when I entered) and mashed the throttle again. All was well with the minions under the hood. All 250 horsies were anxiously awaiting for me to give them a little exercise. I might add, that I was happy that they were ready to play, and gave them their daily workout..