I got back from the Gamblers Run Open Road Race about 3 am this morning. The race was its usual fun. I had forgotten that last time I ran it I had the supercharger and had no problem maintaining 145 MPH average. This time the supercharger and X-pipe were not on the car, having been removed a few months ago for California smog test requirements. The return leg of the race is uphill overall and was into a stiff headwind, and I could not maintain the 145 average. I hit 161 at one point, but after slowing for turns or running up hills, the car labored to get to target speed. So, I arrived 18 seconds late. Ugh! That is super bad.

The first 50 mile leg of the race did not count for me. A cow got on the road resulting in a brief red flag until the cow was scared off by a GT40 kit car passing at 150 MPH. I was the one of only two drivers to pass a checkpoint showing a red flag. So, I pulled over at the next checkpoint, only 2 miles from the finish line, and watched the other cars whizz by. So much for the first leg.

Also, on the tough return leg, the car ran right up to the coolant redzone, even creeping into it. I risked blowing a headgasket but the car seems to have survived OK. I had the throttle floored for almost the entire return leg. Even w/o the AC, it was just too much for the cooling system. Funny thing is that last time with the supercharger and running the AC, the car never got close to the redzone, although it might have been 8 or 9 degrees cooler weather. The cooling system is VERY sensitive to ambient temp.

I really need to improve the cooling system. I'd like to remove the in-radiator oil cooler and go external like the MY90+ cars. Porsche made that change for good reason. The S4 cooling system is marginal for hot weather prior to MY90. It would be nice to relocate the auto tranny cooler as well.

In other news - I will just say that Tim & Cheryl had a successful run in The Beast. They can report the details. THEY RULE!

Matt (edco) just missed placing in his class and George Suennen and Paul Mooradain drove Paul's Z06 to third place in the 155 class, only off .5 seconds from target. George said the Z06 was loafing along and was very stable and and handled turns very well. He found it hard to keep the car under the 172 tech speed limit. The Z06 is quite a car for open road racing, right out of the box. I hope to co-drive with Paul next time.

 

Bill
Right on...sounds like you had a great time.....how was your son as a navigator? Its a bummer I couldn't swing the trip to help out Matt......

After just a few track days in not so hot weather it does seem the stock S4 cooling setup (water-oil-tranny) has much room for improvement.....but ORR does seem harder on the cooling system than a track day when your on-off the throttle alot & only out there for 20 minutes...vs near constant full throttle for extended periods of time! At least you have good airflow during the ORR

 

IIRC the external cooler on 90+ cars is in SERIES with the radiator intercooler,not instead of....
jp 83 Euro S AT 50k.

 

In the 90+ cars the engine oil cooler is separate from the engine coolant cooler. I'm pretty sure that's what Bill's talking about?

 

Bill, what MY Z06?

 

Paul has a C6 Z06....the 505hp model

 

I would install an aftermarket water and oil temp gauge to see exactly what the temperatures are, especially so after installing an external oil cooler since you drive the car the way it was meant to be driven: FAST!

I'm telling you guys, those Z06's are bad-asses!

 

Yes, the oil cooler was REMOVED from the radiator in MY90+.

OH, AND I FOUND ANOTHER REASON THE CAR WAS RUNNING HOT. The WOT portion of the throttle switch gave out. This is a new switch, less than a year old. I had found with the Spanner and Theo's diagnostic program that I really had to snug up the cable to get it to trip. It is supposed to trip at 2/3rds throttle. Until I snugged the cable, using ALL of the adjuster at the firewall, it did not trip. Well, I just checked it again - it is not tripping at all. The WOT switch retards timing 20 degrees. Oh, well. When I reinstall the SC, it uses another throttle switch and it is more accessible.

The other odd thing is that even with all the cable slack out and no more adjustment avialable, the pedal does not fully open the throttle plate against the stop. So, I am loosing full throttle in two ways. There is no slack, but the gas pedal range is not great enough to go to actual WOT. Weird. If I tighten anymore, I loose the idle switch.

 

Hi Bill:

Glad to hear your car survived the ordeal without damage... As to the throttle, you might also look at the adjuster that couples the plastic gas pedal with that metal frame it moves. This is another area of adjustment that might have to do with you not getting full throttle.

Can I come watch when you remove the intake next time?

 

Nicole: That would make sense, but all of the slack is out of the cable. I know you can move the positon of the base of pedal, but it needs more travel. I don't think that is adjustable, but I need to get under there and figure a way to increase the travel.

 

And just as important, with no WOT signal to the LH, the LH will never move over to the WOT fuel maps and will continue to attempt to trim the F/A mixture with the 02 control loop. The result will be a F/A mixture that is tending towards 14.7 rather 12.6 and higher combustion temps from the leaner-than-desired-at-WOT mixture. That's your high temps right there.

 

Could this also cause pinging?

 

Nicole: Yes, the leaner mixture and resultant higher chamber temps increase the chances of detonation under higher loads.

Bill: More than a few Porsche cars have had problems with making WOT at full pedal travel. It may be that loose bearings at the bellcrank on the manifold are partially to blame, or it may be that the cables are stretching. Maybe a little creative geometry change on that bellcrank is in order. In a perfect world, you would be using about 30% of the end-of-travel spring on the cable with the pedal mashed and the throttle plate at 90 degrees. I need to go look at the relay arms and see what makes sense. Good news is that those little ball studs are pretty common, so you can play a little with position on the arms.

If the switches aren't holding up well, there are certainly some industrial-strength options.

 

Bill

 

Dave: Yep, I knew it was a real bad thing for driving like I was doing. I have found a number of cars, including Nicole's, where excess slack in the throttle cable resulted in the switch not tripping. And just about every car shows it tripping much higher than 2/3rds throttle. It's as if the lever arms on the throttle quadrants need to be longer or the one on the throttle body needs to be shorter. People complain about the heavy throttle action - this would make it heavier, unless the spring tension was unwound a turn. It might be better to wire in a WOT override switch right to the pedal.

Nicole: Yes, it could if the pinging occurs under full load and high RPM. I believe it has no effect below 4K RPM, and it's not supposed to be relevant below 2/3rds throttle. Dave may know if there is an RPM cutoff.