Monday, April 10, 2006

"...no, I mean you're ON FIRE..."

Hey, at least we got the first crash out of the way.

Turned out to be a pretty good one, for me. It killed the Audi S4/RS6 and the Pontiac GTO, the only two guys in front of me. We went to yellow flag and I took the time to pit in, and was able to come out in the same position.

Here's what happened: The GTO's fat ass and massive torque likes to digest tires. Meanwhile, it's outsized engine likes to guzzle gas. They resolved the running-out-of-gas issue the only way they could, by cutting into the body and slapping in a bigger fuel cell. Cool! They learned math!

Problem: Gas has weight. Bigger fuel cell means more weight in the rear. Which is a good thing...they were able to launch harder out of turns. In the beginning, anyway. Race-grade gasoline weighs about 6.65 pounds a gallon (86-octane usually weighs about 6.216, and premium weighs around 6.35; it varies a little from refinery to refinery). Now, that translated to maybe 80-95 pounds of ballast in the rear. Unfortunately, when they retuned the suspension for the extra weight, they forgot about how that gas was going to gradually disappear.

Result: The GTO experienced massive tire-burning and unintentional throttle-on oversteer 15 laps after fueling. Around the time of the crash, he had basically no rubber left in the rear. "Bald" doesn't even begin to describe those tires..."scalped" is more like it.

So he did the natural thing and started braking earlier. Meanwhile, the Audi's driver was getting better behind the wheel, and he started making up time on the GTO. Eventually, they entered a sharp turn fairly close to one another, and when the GTO braked early...crunch.

Good night, intercooler. Good-night radiator. Good-night grille. Good-night intake. Good night, everything in front of the frame's nose.

The GTO, for its part, took the initial impact fairly well. The exhaust pipes crumpled up and twisted shut, which is a lethal hit...carbon monoxide will build up in the cockpit. Unfortunately, the GTO fishtailed and slid off the track and into a wall at a slight angle, which ripped the passenger-side wheel off.

Here's where the "fire" part comes in. I was a second or two back, with the Corvette, which was actually making a good showing. I hadn't gotten up to the point where I felt like really passing him, so we were kind of running side-by-side. I saw the crash, and the huge, hideous pile of Audi parts bouncing across the pavement, so I tapped the brakes and hung back in preparation for the yellow flag. The Corvette's driver dodged out in front of me and then noticed the enormous pile of debris.

One of the things I designed and built into the car was a little button that deploys two course mesh screens over the intakes. I figured, shit, both of them are right down at the front lip, it might be good to have a way to protect them while keeping them fully open during normal operation. My little button snaps the screens down in maybe a quarter of a second. I thumbed it just as I started braking.

The Corvette had no such trickery. What it did have was a big, open intake mounted on the hood. And as it roared through the debris field, it snorted a handful of Audi pieces.

But that's not where the fun stopped! The pieces ripped a big hole in the plumbing. And this hole occured after the Mass Airflow Sensor, which tells the ECU how much air is going into the engine so that the ECU can tell the injectors how much fuel to squirt into the cylinders.

The hole increased the mass of air going through the intake plumbing by virtue of giving it an unregulated opening to travel through before hitting the engine. The MAF saw all this air going down the tube and couldn't tell that most of it was getting sucked out through the hole. So it told the ECU, "Dude, there's a crapload of air coming in!"

The ECU replied, "Dude! I better tell those injectors to dump a crapload of fuel in!"

The intake valves, meanwhile, were weezing to let in a measly amount of air, while the MAF and the ECU clicked happily away in their own little world.

Now, when you get a whole crapload of fuel and not a lot of air, you end up with unburned fuel. Within the engine, this isn't too big a problem (unless you count detonation as a problem), since the fuel is mostly getting pushed out through the exhaust ports and into the headers.

All this fuel, which is travelling as a bunch of big, heavy droplets surrounded by a very fine mist, can only go so far before it hits something hot enough to ignite it.

This leads to giant-ass flames shooting out of the exhaust pipes. And the ignition of the bumper.

I clicked over to the driver's channel on the radio, which is kept open specifically for emergency events like this. The radio circuits we use were another little invention of mine. The driver's channel allows you to cut through all the bullshit--namely, your team and his team--and just talk to the guy. It plays through the left headphone, as opposed to everything else, which goes through the right. It's also encrypted, so we can use whatever language we see fit (everything else can be picked up by anyone with a VHF or even, sometimes, a clock radio).

Me: "Danny, ah, you're on fire."
Danny (Corvette): "I know, the car's dialed in today. What about keeping the channel clear?"
Me: "No, goddammit, I mean you've got some flames coming from the exhaust and your bumper's starting to go. Get it on the grass and kill the engine, for fuck's sake."

Luckily, it had rained the night before, so he didn't have to stop on the side of the tarmac. The grass was wet enough that it didn't light up.

We went to yellow for 5 laps and then raced the final 15. The M3 came damn close to acing me, and I thought the EVO was going to win until its tortured center differential finally gave out on lap 34. No matter...another win for better driving and the simple front-engine/rear-drive layout.

1 Comments:

Blogger speed junkie said...

Dude, congrats for the wins. Still got it then eh? Good for you mate. Btw, don't tell me that that's you in those Lexus LF-H spyshots taken at the Ring? Is it?

http://paultan.org/archives/2006/04/08/lexus-lf-h-spyshots/#more-1207

6:49 PM  

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