IcemanG17

Bill
Thats really odd with the WOT......I wonder if there is a roller cam you can add to increase the travel or leverage of the system like you did with the S/C setup you made? I don't really think something like that would fit under the intake......but gives you another reason to reinstall the S/C...??

Nicole

Ha - THAT might be the reason why we had so much pinging in the mountains, on our way to and from Denver last year. Since then the throttle has been adjusted with the help of Bill's laptop diagnostic tool, and I have not noticed any pinging recently. Need to pay some attention to this next time I drive.

worf928

I believe that the WOT switch will cause the LH to switch to the WOT maps and disregard the 02 loop at any RPM. I believe this to be the case based up on dyno charts I've seen for cars with functioning WOT switches and for those without functioning WOT switches. In the former case the A/F mixture drops below 13 within the first few samples periods and in the latter case the A/F mixture straight-lines at 14+ for the whole run. I could be wrong and some other combination of factors could reproduce the behavior. But, I believe in Ockhams's Razor...

I've tested WOT switches directly. I've yet to find one that triggers at anything less than ~80% of rotation. I find that, typically, the WOT switch will trigger only in the last 1/2" or so of pedal travel. This doesn't seem dependent on age, mileage, or whether the switch has been replaced - for 87+ at least that is. I've tested a 90 with 24k miles, new WOT switches, my '91 with it's original switch... they all seem to trigger much, much later than where the WSM says they should.

jorj7

Bill,

Just a quick check in. The Z06 is a very good ride for ORR. Great handling and power.
I figure it could do a 160 mph average without too much trouble. Thanks Paul for letting
me co-drive the car. But I still can't wait to get my car back.

I'm sure Tim will check in later, after his head clears...

John Speake

IIRC the WS manual mentions that the 85/86 cars throttle switch goes to WOT at 2/3 travel. But the S4 and later switches are different, so maybe they do close the WOT contacts at a greater angle from idle. I have a couple of switches arriving soon, and will check.

Dave is correct that when you first hit the throttle the LH gives a short burst of mixture enrichment (you don't have to hit WOT for this to happen, the LH senses the rapid change of MAF voltage).
This enrichment is to prevent the motor from having a brief lean out and stumble.

Steady state with WOT switch non-op would of course give you contstant 14.7:1. Too lean for high speed running.

Garth S

..... a digital accelerator pump, so to Speake ( for those weaned on carburetors)

Garth S

Bill,
Check out the flow characteristic (Cv) of a butterfly valve when used as a control valve - which is what the throttle plate is. Generally, above 80% opening, the butterfly is controlling absolutely nothing .... as max. flow through is already realized.ie., the last bit of travel achieves practically nothing.
I do not know where the stop screw is set on your TB, but if it is anywhere near 90 deg from closed, would be far less concerned about getting the plate to bang against its stops than having the position switch activated to defeat the O2 trim loop, etc.

John Speake

Exactly !

The amplitude and duration of the acceleration enrichments are edittable with the SharkTuner...

You have a good point about the throttle plate, I will check a new throttle switch and also a faulty one which I am retrieving from a loacl owner.

Bill Ball

I thought the last few degrees might not matter much, but I have seen other cars where the pedal causes the throttle plate opens all the way and it still seats against the idle stop when released.

Tom. M

You'll want to check the hoses under the intake too. In particular the one that exits the passenger side MAF boot and y's into the hose running to passenger cam cover (rear) and heads forward to the oil filler neck.
Mine was mispositioned and the throttle spring arm would contact it at near full throttle (making it hard to push)..and also wearing a hole in the upper part of the hose where I was getting false air after it wore through.
Good luck
Tom
89GT

Robert_H

Bill,

Congratulations on the ORR results. Even though you were off in the timing, I still think that it's a great experience and something that most of us 928 owners are in awe of.

Like Nicole, I also would like to see what is involved when you take your stock intake off to place your S/C back on. The accel cable with the slack (note: a couple of days before Bill went to the ORR, he ran a scan of my car and I also have a slack cable and no WOT capability. My car also runs a little hot as well) and other WYAITs are of great interest to me.

Rob

dr bob

Remember that the WOT map only engages when you are at 2/3 throttle or higher, under the best of conditions. Most of my driving, even in the local SoCal mountains I keep in my back yard, is done at well less than 2/3 throttle. If you have a noticeable pinging problem, you might be fighting a weak oxygen sensor, weak or non-functioning knock sensors, or perhaps something simple like worn or incorrect plugs. On the more serious/expensive side, a weak or dirty MAF can also be a cause.

Fuel quality is not wonderful these days, especially when purchased at higher altitudes; You may notice that the octane ratings for "premium" sold in Denver is lower than the 91/92 you are used to seeing at sea level. The lower effective compression caused by the thinner air generally means that there's less chance of pinging with the lower octane. Problems show up when your Denver gas gets down the hill, and you need the extra anti-knock capabilities. The push to higher levels of ethanol in our fuels is also a sucker deal in many ways for motorists and taxpayers. It takes more pounds of fuel to go the same distance, and that extra flow requirement may strain the fuel management system's capability in the car. The "good news" is that all the taxpaying population is paying for the ethanol with subsidies, and you get to pay for it again at the pump.

Bill Ball

dr. bob: I think you're right about Nicole's pinging. We rarely drive these cars at WOT for more than a few seconds, but then again, Nicole is WOT a lot more than other people.

Tom M: I've had that experience with several intake restorations. You have to get that hose just in the right position or it jams againt the throttle linkage. If you don't check it carefully before bolting the intake down, it can be real fun later to get it into the correct position.

I can manually move the throttle to WOT by pulling the lever for the second half of the cable at the quadrant, and the WOT switch will trip, so the mechanism is free, but my pedal cannot pull it far enough. I have all the slack out and the idle switch trips immediately, so I cannot tighten it more. So, the WOT switch is still working. It just comes on SOOOO late now, I can't get the throttle plate to that position.

Richard S

Bill, despite your problems, I hope you still had a great time. Cow on the course is almost a worse-case scenario....big, slow, unpredictable. I'd rather see the red-flag than have someone plow into it.

Funny how we can think our cars are prefectly fine, then a simple little task like, say, driving 160mph through the hot desert, will expose any weakness. But you have plenty of time before the Pony Express to work it all out! (Unless you take a ride with the Dark Side...)

Speaking of which, George, you sound impressed with the Z06....I know Paul certainly is, and it appears to be the perfect ORR car right out of the box. Since it was "loafing along", was that in 5th or 6th gear?

And congrats to Matt as well....another one hooked on the go-fast crack pipe!

Now, time for Tim and Cheryl to fill us in on the Beast's run....

Glad everyone is safe and sound, see you at the Pony.

Rich

Tahoe Shark

Just a brief interuption on the WOT issue.

After the fog cleared on Sunday morning from our celebration Cheryl and I reflected on the weekends results. Awesome, Yipee, E gads, Holy Smokes, Spectacular!!! On the way down (northbound) the car was a rocket. We ran the trap at 207 mph, the promoter clocked us at 205 average over a measured distance so that is the number that will stand for the north bound run. I on the other hand will count my proven mph as 207. (See below) At MKM you must backup your run on the way back or it doesn't count as a "200 Club Member" so we prepared the car at the turnaround for the return leg.

Just before we go off the line the starter Lincoln tells up that the winds have come up and we will be bucking a 15 - 20 mile head wind on the way back and to be carefull because deer have been reported at the haystack ranch. Great, how about no issues for a change. The first 2/3rds of the run were non issues and when the car comes to the crest turn to start the 2 1/2 mile runup the wind hits us and we LOSE 4 mph. Wonderful, I press the pedal all the way down and am pretty sure I have dented the floorboards. The car is accelerating very slowly and I briefly think about downshifting then realize that at 192 I really can't do that. One 1/2 mile to the trap and we are at 197 and not going anywhere. All of a sudden the wind absolutely dies and the car takes off. We go throught the trap at 200 even on the GPS. I keep the pedal down because it is a measured average and I don't want to come up short. About .5 mile past the trap is a left hand "kink and we blast around the turn at 202 mph. Never done that before and won't do it again. The car never slid, slipped or became unsettled in the turn but that was stupid. Cheryl and I are horribly disappointed because we know that our gps reading will be reduced by 1 or 2 mph. We try to get back on time but we have run so fast for so long that we cannot drop that much time before the finish line without being disqualified for going to slow. (minumum speed for SS is 130 mph). We cross the finish line with a bad attitude and a very dirty car because the expansion tank hose came off and dripped oil all over the passenger side. We don't stay at the finish to talk and drive back to the parking lot at the hotel. We immediately break out the beer and begin drowning our miserable performance and I am really p*ssed off about not making the 200 mph club. The other SS guys come up and try to cheer us up but that is not working very well.

We briefly consider not even going to the banquet because in our quest for the speed we really did not time keep this on this run. Cheryl's main job this time was to keep me on the road and give me speeds and directions. We finally decide to go to the banquet and take our personal shame and try to hide it. All of our friends are receiving there trophies and they get to the 160 class and call third place. Not us? Uh Oh, I know we did really badly, did we get disqualified for busting tech again? Crap we thought. 2nd place goes to ... Car # 4, Tim & Chery Dey? Really, maybe a small consulation but not the one I wanted. Then they announce that there is another award to the newest member of the "200 mph Club". WE MADE IT!!!! Exactly 205 and 200mph. I was so thrilled I could not stand it. Remember that 202 turn, the radar guys said that if I would not have kept the throttle on I probably would not have made it. So now I'm happy, we have accomplished the first part of what we set out to do last year.
Thanks to everyone that has ever helped with this car! Bill, George, Paul, Rich, Dave everyone who has helped us at the races.
Thanks also to DEVEK for building the car and believing in us and our goal. I owe Marc & Susan a big thank you.

Later