95jersey

How fast is too fast without using some kind of wing or special aerodynamics enhancements?

For you guys that go to track events in your stock or modified street cars with lots of HP, how fast do you go on the LONG straits without backing off? You can really get the speed up there on some of these ROVALS (nascar ovals with road racing infields). Even though our cars are capable of 180mph+, it seems that this would be way too fast without having at least a wing. What do you guys think? When should you consider backing off?

willi

I could be wrong, but I thought wings were more for generating cornering force than going straight. So how fast do you want to corner and do you have a suspension with tires that will hold at those speeds?

I've been somewhere around 140 on a straight and don't think anything was particularly unstable. It's the turn at the end of the straight that makes me think twice about staying in the throttle until it's time to hit the brakes.

fluxen

I don't know how fast is too fast, but it's a lot faster than my Z06 will go. I've never been on a track where I was going so fast I was worried about the speed, or where the braking zone at the end of the straight was "scary". Having said that, the Rovals might be a different story. 160 - 170 might be the neighborhood, but at WSIR (the fastest track around here), it's more like 140 - 145, and that's far from too fast...

And the wing may give you rear end stability under braking, for instance, but it is for the corners. You should be stable just accelerating in a straight line as is...

Gary2KC5

@ Road America, @ the end of one of the 4500' straight you can be going 165-170 mph before getting to the 500' brake marker and getting slowed for a 45 mph turn in.

I've wondered about a front splitter / rear wing before but I've come to the conclusion (from input from racers like Dave Farmer) that the C5 was design with enough downforce that it won't begin to fly at those speeds.

In fact, a wing on the straight away will rob you of about 15 HP.

end of wing/splitter discussion for me when I realised it would take HP away.

fluxen

I look forward to the experience at Road America :D We'll be going there later this year.

As to aero taking HP away...I'm sure you mean you're losing MPH, not HP?


[Modified by fluxen, 4:34 AM 3/14/2003]

cgh1

Charlotte (Lowes Motor Speedway), which is a ROval is good for about 160 or so down the back straight. VIR back straight gets me to about 145 'cause i don't shift up to 5th. It's a long straight but you spend a lot of time going up hill (a big hill...) which takes away from some of your torque.

I've never felt uncomfortable about stability. Only pucker factor is "will I have enough brakes left this time around to slow me down?" - which is usually at turn 1 of VIR (down from about 135 to about 70 from sign 2.5-3) and/or turn 1 of Roebling (140-145 down to about 70, again from about sign 3). Charlotte is not too much of an issue as it is a ROval - NASCAR 3 & 4 are about 145MPH turns for me. The entry into the road course is hard on the brakes from about 130-140 down to about 50-60...

I'm rambling now - sorry.

To me,
Too fast = 100-120 or above on public streets, 'cause you never know what
moron might pull out/over in front of you.

Too fast = ??? on track... how big are your brakes, and your cahones? :)

John Shiels

Pocono going to tunnel turn 163 with a pasenger. Hope for 170 with more HP and no GF in car to make me worry. Top speed depends onhow fast you exit the corners to gain speed.

z060ntrack

I pretty much agree with all the speed assesments that are stated here but basically the issue with the C5 is front end lift from high pressure under the hood. Your money would be better spent getting a hood like the one Doug rippie sells which will reduce that lift and lower temperatue at the same time.

fluxen

Do you have a link to someplace with numbers on lift at speed? Where are you getting the info?

LTC Z06

I've done turns and hills on the autobahn at 160+ mph, no problems, the C5 has (mine is lowered) has great aerodynamics.

JSA 007

Sorry, I just don't think my vette could go anywhere near over 150 MPH, but I have a wing anyway. :D I've yet to race around a ROVAL but someday I'll see what my car's limits really are :cheers: From my limited experience though, the vette's always been surprisingly stable over 100.

Jim 47

Too fast is easily definable, when you go sailing off at the end of the straight, you are going too fast. :D

A properly adjusted wing on any car will create Down Force, which will create more "Grip" of the tire you have on the car, wheather that car is going straight or cornering. The more the Grip, the greater the side force (centrifical force) the car car resist before it starts to slide in a corner, and the better stability you'll have on the straights.

Personally, I think that my C5 is very stable at 150 mph, with no wing, but the lowering and the stiffer shocks both help that stability. I've talked to some dirvers who have run the the 160-175 mph range on a race track and they think the C5 is somewhat darty at those speeds with no wing, and they are running the T-1 suspension. I think that a wing at those higher speeds would add stability to the car on straights and also improve cornering speeds.

John Shiels

I want to vent my hood but only found some vents I am not crazy about. Was thinking of Vipers hood vents but they are made for a straight surface. I hate raised hoods. My car was stable at 175 stock Z51. When LPE did the big end you see the hood raise you know it is lifting badly. I did want to do splitter/wing deal but never got a call back from APC.

till

I know people in Germany who claim they did 190mph+ on the Autobahn in a C5. None of them said they did not feel comfortable about the cars dynamics at that speed.

My car only goes 165mph and it has a small wing and front spoiler (I am not sure this qualifies as a splitter). It feels perfectly stable at that speed.

Till

Jim 47

John:

You can get some hood venting and thus more front downforce by removing the gasket at the rear of the hood (by the base of the windshield). This will let the air escape from the engine compartment and lower the under hood temp and pressure. :cool:

h rocks

I've never done it, but I've got to believe that if Mario Andretti, and John Lingenfelter say that a stock bodied C5 coupe gets squirrelly at the top end, that's good enough for me. I seem to recall that because of the design of the big butt, there's a fair amount of lift around 150. Dave Farmer has posted some drag and lift numbers in the past when the wing/aero question has come up in the past.

fluxen

I don't have C5 specific info, but this is generally not true. The base of the windshield is a high pressure area on every car, and lets air *in* through the rear. This decreases airflow through the radiator, fyi. Whether the C5 has more pressure under the hood or at the base of the windshield due to it's "bottom sucker design" is a question I don't know the answer to.

Jim 47

I was told about this (removing the gasket) by three T-1 racers, and I guess I assumed that they knew what they were talking about since they had used this method on a regular basis. I think that some of the "extractor" hoods are made to extract air from the engine compartment at the rear of the hood, just in front of the windshield, so there appears to be lots of evidence that your theory is incorrect.

I think that you are correct that there is a higher pressure area at the base of the windshield, but the pressure there is not as great as the engine compartment pressure, thus the hot air will exit at that point. Right now I'll go with the experience of the racers I have spoken with. :cool:

fluxen

I hope you're right, because that's a hell of a lot cheaper solution than getting a vented hood. I'll have to look into that! :cheers:

LTC Z06

I tried this, it worked! Hood had hardly any movement at 150mph and after doing some laps brake fluid was cooler.