no ac after 140mph???

[rsiwicki]

okay...I have got a funny thing going on with my car at very high speeds, 140+ with throttle floored

I have noticed this several times now that after I do my last 3-4 shift...the AC goes out and also I am getting some kind fine water spray/mist on the windshield...the air is still blowing fine...but the air turns from all of a sudden cool to outside air. Is there something on the inside vs. outside air ducting selector that at these high speeds is just forcing the warm outside air through the duct work? I have no idea what the fine water spray mist could be as I have only done these high speed runs at night so I can't tell where infront of the car it is coming from?? but it does not appear to be of any color and I am just wondering if it is somehow from the windshield washer fluid???

All seems to be fine and everything return to normal as soon as I let my foot off the gas from having it hammered to the floor and coasting down to 135mph or so....

I raced a heavily modded E500 tonight...it looked just like an damn E55, but was a new E500 that the guy just got out of the performance shop a week ago and was sporting it around town. We went at it from 60mph all the way to 145mph trading a few feet here and there but neither of us could pull more than 4 feet on eachother...it was one of my best races yet just sitting side by side for those 15+ seconds watching/listening to our cars run. The guy was cool and had a buddy who has a M45 and thought that he could outrun me but was really surprised with me all the way along side of him...his mods were way to numerous at about $10K he told me all together

btw...I appreciate your concerns for safety and I can hear the comments alreay coming to say that I should be more worried about my tire specs, etc. We have already been down that path before and I am well aware of the risks that lie with my driving so please save them for somebody else

[squeefoo]

Probably a shutoff so the A/C doesn't over speed - on most cars there's a WOT A/C cutoff . BTW I would turn it off before I raced someone. Don't think the WW fluid could pull out from the nozzles, that's a high pressure zone at speed. Could it be sweat from the inside?

[rsiwicki]

sweat from the inside....too funny. It is not like I plan on doing these 140mph runs, it a carpe diem (seize the moment/day) kind of thing as all the elements were right for race to run this fast as there were no other cars on a wide open straight away of interestate

[PalmerWMD]

squeefoo summed it up pretty well IMO.

Fred...

[elwesso]

He is correct, there is an alternator cut as well as a AC cut, I believe it starts about 65-6700 RPM and ends at the redline...

[pito11213]

Damn you did 140 with the AC on. Good job on showing up the guy who spent crazy paper just to keep up with you.

[elwesso]

Damn you did 140 with the AC on. Good job on showing up the guy who spent crazy paper just to keep up with you.

And still has a car payment.....

[russg]

Some thoughts:

There are probably several things that will deliberately cause the AC compressor to disengage. Engaging the starting motor, WOT, and most probably a high engine RPM cutoff. I experience the first two every time I'm in the car, and had an inadvertant experience with the third a couple of years ago. Turning on to Bush Highway after leaving my marina, I absentmindedly left the trans on my 2000 Q45 in 2nd gear. after a couple of miles of a 65 mph run on cruise control, I noticed the compressor was clearly not doing its job. For about the next minute, I bemoaned a trip to the dealer for a service call under warranty. No big deal, but a minor inconvenience at least. I then performed a routine intrument panel scan and noticed the tach was reading significantly north of where it should be. A heretofore dim bulb in my head finally shows some light and I realize that I've been cruising the last several miles in 2nd gear. The engine was so damn quiet in that car I never noticed it. Nudged the trans into Drive, and the compressor immediately went back on duty. Since I was a long way from WOT, I can only assume there was an RPM cutout feature that had been engaged. It could also possibly be a high head pressure cutoff being activated by the high head pressure in the system being generated by the extended high RPM compressor speeds.

As far as the spray on the windshield, I would attribute this to the wind turbulence generated at your slightly sub-sonic speed. With the compressor disengaged, there is a natural occurance of any icie formed on the coils or the under hood refrigerant lines to melt off. Normally this is evidenced by a puddle of water that accumulates under the car after being parked. Not much chance of puddle formation at 140+. Instead I propose that the significant air turbulence created at this speed is driving this moisture up throught the cowling and distributing it across your windshield and elsewhere in a somewhat higeldy pigeldy fashion. Essentially, wind power trumping gravity.

Russ

[louiegz]

I guess at 140mph, even in the Miami heat, you should shut off the A/C. The old Q still has it.

[rsiwicki]

thanks for the answers guys...much appreciated and yes...the old Q still has it movin although I did recently spend about $10K myself in speed mods so I am about even with the guy in the E500...although he spent an additional 15K in brakes, wheels, paint, sound system, etc. The benz guy was really cool to race against as some people get really pissed and give me the universal sign while I am hanging or beating them and I still never pick a race first...they still come to me.

[911/Q45]

I would check very carefully for a slight coolant leak that only happens under extreme conditions(140 mph probably qualifies) to account for your windshield mist.

[PoorManQ45]

I guess at 140mph, even in the Miami heat, you should shut off the A/C. The old Q still has it.

That's not true. I live a few hundred miles North of rsiwicki. I had the AC on when I was doing a top speed run. I got up to 165mph with the ac on. It was blowing semi cold still. I turned the AC off manually and continued up to 175+mph before I shut-down.

I guess my Q is just special.

[PoorManQ45]

okay...I have got a funny thing going on with my car at very high speeds, 140+ with throttle floored

If you're not in a racing situation, don't go WOT. That will keep the AC blowing on your car. In a race situation, just turn the AC off.

[911/Q45]

That's not true. I live a few hundred miles North of rsiwicki. I had the AC on when I was doing a top speed run. I got up to 165mph with the ac on. It was blowing semi cold still. I turned the AC off manually and continued up to 175+mph before I shut-down.

I guess my Q is just special.

Gee, how did you get past the speed limiter and how did you read 175 on a 160 speedometer? I guess you must be just special.

[PalmerWMD]

911:

He doesnt have a speed limiter, he has the Brabham Q45.

Fred

[elwesso]

Quickly children to the short bus!!!!!

[Rex]

911:

He doesnt have a speed limiter, he has the Brabham Q45.

Fred

I thought someone in AZ had the Brabham Q??

[HeavyDuty]

That's not true. I live a few hundred miles North of rsiwicki. I had the AC on when I was doing a top speed run. I got up to 165mph with the ac on. It was blowing semi cold still. I turned the AC off manually and continued up to 175+mph before I shut-down.

I guess my Q is just special.

PMQ,

Uh,

Hmm,

Yeah.

Buddy, you simply *must* stop throwing caution to the wind with your comments.

I usually try to stay out of the fray, but....there's not a street driven Q in this forum that would do 175mph if driven off a cliff.



Thus far, you're a good argument for banning the use of forceps in the delivery room. This is not an obnoxious group of people here, there are designers & engineers & techs & generally people who don't frequent chat rooms filled with prepubescent angst & outlandish claims.

I hate to be a jerk, but please, if you were to try a little less hard to impress people & assume a place in here like the rest of us, your chances of being ridiculed publicly would dramatically decrease.
Modified by HeavyDuty at 8:54 PM 9/12/2004

[Jesda]

I think PMQ has an optimistic speedometer, which is true of most vehicles after about 100-120mph. The faster you go the more exaggerated the displayed speed is. When the needle is that far up youre actually doing 15-30mph less than it says.Ryan (1992Q45A) has the 318hp Brahbam Q.

The only true speedometer is GPS-based.

-Jesda

[PalmerWMD]

Sorry guys for some reason I confused him with Ryan,

I'll go to bed now, this is my second mistake tonite.

Fred..

[maxnix]

I think PMQ has an optimistic speedometer....

-Jesda

Maybe he has those little hooptie 13" wheels on 8" spacers.

That would be good for a 25% speedoometer error.

[PoorManQ45]

Refer here if you want to know how I got over 170mph

http://www.nicoclub.com/zerothread?id=73516&page=1

[PoorManQ45]

I think PMQ has an optimistic speedometer, which is true of most vehicles after about 100-120mph. The faster you go the more exaggerated the displayed speed is. When the needle is that far up youre actually doing 15-30mph less than it says.Ryan (1992Q45A) has the 318hp Brahbam Q.

The only true speedometer is GPS-based.

-Jesda

That is true. Speedometers arn't very acurate at higher speeds.

Does ryans car have 318rwhp? Or is that at the crank/flywheel?

[PoorManQ45]

92 Q does not have speed limiter.

[Jesda]

I dont recall, but an article on it is here:http://www.q45.org/brabhamq45a/

[elwesso]

92 Q does not have speed limiter.

Try again!!!!!

[PalmerWMD]

92 Q does not have speed limiter.

The only non speed lim ited Q45 's were teh first few ( some say 6) weels of production of the 90 MY.And for those who have the JWT ECU.

All other G50 Q's are limited, (to 150 mph, tho some sources claim 155 mph).

The Y33's are limited too, I am unsure about the 2k2+'s to which mph they are limited to but they are also limited.

Fred..

[HeavyDuty]

http://www.racerpartswholesale.com/physics6.htm

Interesting read on hp required just to overcome wind resistance once frontal area, cd, gearing, tire height, rpm, etc are calculated.

Another good one at smokemup.com will do it for you if we have all the info posted above.

Let's say it was a first six week 1990 production car, (the 150 mph one) in perfect running condition, perhaps we could cajole Tech into calculating the *extra* necessary horsepower to achieve 170,

...providing the speedo even read that high....

Way above my head (DCB).

Clue> exponentially more than one would think.

S.W.A.G. = 500 bhp

What do you say fellas? Step right up, get a hunch & bet a bunch, who's next?

[AZhitman]

PMQ, I gotta echo what Heavy said. You simply can NOT come in here slinging such BS without someone calling you on it.

I would bet the title of my pristine and perfectly-maintained Q against you exceeding 155 (much less 170) in your Q. Ever.

I have seen 140, once, with the proper tires, with no extra crap in the car, and in perfect mechanical condition, and it's a scary place. The lifting of the nose, even with a 1.2" drop, was enough to convince me that the car is best kept at/under 135.

I'll step aside while you retract your error.

[rsiwicki]

wow!!! I can't believe all this excitment.

greg....just curious as to why you would be feeling a "lift" in the nose of your car as I am thinking that you should be feeling the lift from the rear of your car. From my limited high speed driving experiences and limited knowledge from car mags...you should being feeling a lift from the rear of the car. The spoiliers on the rear of cars are to keep the back end down and more stable. I could easily be wrong but I would like to know if what I am assuming/read to be true that you should feel a rearend lift before any front lift from high speed driving...I have felt a rearend lift before where the front was glued down, but the rear felt really light and a tad wiggly, but not on my Q...it was my mom's car that I was driving in high school.

I have only gone to above 135 about 10 times and all 10 times being since I got my car all modded. And above 140 has only been 3 times to about 145 and I just so happened to notice the AC went out each time and just started blowing warm air. I would love to find a road to just cruise at 140mph or so to get a true feel for the car.