bmylez

iTrader: (3)

Gimme dem EXHOUST gasses.

black_ax

lmao :d

ravenls6v

And one has absolutely nothing to do with this thread. A cts v1's handling will not be affected by exhaust pressure on any measurable real world scale, I don't care how many diagrams of unrelated race cars you post.

black_ax

I was trying to show how an exhaust flow could affect downforce levels and using proven real world example might help explain what I was talking about. As neither of us have had this issue I don't think there is anymore we can add to this topic.

I would be very interested in your ideas about how removing the catback could cause this issue.

ravenls6v

I'm not certain what the issue is either but I'm certain it's not exhaust gas pressure creating lift on the rear end of a ten year old 2 ton gm sedan because f1 car. The guys are experiencing stabilitrack intervention shifting from 3rd to 4th gear on the street and you are talking about sustained high speed and lift being created by extra exhaust pressure under the car and those two things do not jive. Theoretically between the shifts the rpms would drop and the exhaust pressure under the car would decrease considerably shortly before the time the stabilitrack is intervening, if it were even a factor at wot in the first place.

ls1247

iTrader: (2)

Most 10.5 radial and outlaw drag cars are dumping the exhaust through the front fender just ahead of the wheelwells with turn-ups to take advantage of the downforce it creates in order to take every opportunity to keep the front tires on the ground. Must be a little something to it.....

ravenls6v

Ehhh, yes outlaw drag cars and f1 cars are just like first gen cts v's...so all the same physics apply. I mistake my V for a 1500hp race car all the time.

NIKDSC5

iTrader: (10)

Lol I'm with you! I have been laughing at this conversation all day.

ls1247

iTrader: (2)

My v and an f1 car have a lot in common....I run premium and my tires are almost bald.

I think most of us know that dumping a v1's exhaust underneath the car won't cause it to get out of shape but on the flip side, there are forces being applied, negligible or not.

black_ax

Here is a little areo info http://www.autozine.org/technical_sc.../tech_aero.htm
"Lift

Another important aerodynamic factor is Lift. Since air flow above the car travels longer distance than air flow underneath the car, the former is faster than the latter. According to Bernoullis Principle, the speed difference will generate a net negative pressure acted on the upper surface, which we call "Lift".

Like drag, lift is proportional to area (but surface area instead of frontal area), the square of vehicle speed and Lift Coefficient (Cl), which is determined by the shape. At high speed, lift may be increased to such an extent that the car becomes very unstable. Lift is particularly serious at the rear, you can easily understand, since a low pressure area exists around the rear screen. If the rear lift is not adequately counter, rear wheels will become easy to slip, and that is very dangerous for a car travelling at something like 160 mph."

UnsafeAtAnySpd

Man, this conversation is getting intense...

Mine will activate at lower speeds as well by the way. And running the cutouts open on the track, I've noticed no ill effect. Still good (and amusing) discussion going on here.

Edit: My long term plan (if possible) is to somehow run side exit exhaust through the rockers similar to the VR. Possibly still retain the cutouts to run through a simple muffler in the stock resonator location with some turn down tips in case I need to drive highway a long distance.

ls1247

iTrader: (2)

what we need here is an engineering cage match....paging fuzzylogic

black_ax

LOL ya I think we have all jumped off the deep end. Now i'm even more interested in whats causing the problem. Can you reproduce it at will? or is it mostly random?

Running the exhaust though the rockers would be killer, I know i've looked into it a few times and it would take cutting and sleeving the "frame rail".

NIKDSC5

iTrader: (10)

What!? No one here jumped off the deep end except you! Lol the exhaust caused the car to get light?! Do you hear yourself? Yes I have read your argument in later posts and it is just comical. Also, the exhaust added underneath the car would technically negate your lift thought. If you were to add air underneath a wing it would increase the speed underneath, no? Causing a loss in lift. you are claiming this is happening at only 100mph (apparently 100+exhaust is enough to loose traction). While an f1 car at 220 may cause problems, a 4,000 sedan is laughing at you. And so are we.

Later you claimed cars are designed to cause lift for fuel mileage?! Ahahaha please give me that source.

So instead of a high frequency noise and vibration near a sensor that is directly related to the stability system you think the added exhaust pressure is lifting the car? Or maybe, it's acting like a hot air balloon with all the extra heat! Gimme a break.

black_ax

Few things first lets agree on termonialigy first (or i'll try to explain what I mean by it)

This is what i'll call an airfoil


and this is what i'll call a wing


They are the same thing just one is turned upside down to make negative lift Also known as downforce.



When and area of high pressure relative to the area of low pressure travel across an airfoil lift is created.

Cars are inherently like airfoils witch means that if no corrective actions are taken the car creates lift. A corrective action would be to add a wing to a car to create downforce. Another way to create downforece without a wing is by using a Diffuser

The diffuser works by expanding air back to ambient pressure. It uses Bernoulli's principle, such that the pressure decreases while the velocity increases. Since the pressure below the car is lower than on the side and above the car, downforce is produced in the diffuser. A way to increase the effeteness of the diffuser is to "blow" it

A blown diffuser is basically a way of using the exhaust gases to interact with the diffuser airflow To re-energize the air at the back of the diffuser to create more rear downforce








So back to your argument "adding air underneath the car would technically negate your lift" No because you are adding more pressure and increase turbulence which also slow down the air flow witch increases lift to the underside of the car



I hope we can all agree that the V1 doesn't lose traction at 100 mph, but i'm not sure how many of you have been higher. 120? 140? 160? If you have traveled at those speed or been in a car traveling at a high rate of speed you know that cars can get squirrely. This is because the increase in lift. (higher speed = Higher lift)

So my theory is that with the increase of exhaust to the underside of the car this raises the pressure witch creates more lift at a lower speed. witch causes te car to get squirrely Witch causes the stability control to engage.

Also stability control also uses wheel speed sensors to know if it needs to engage or not. Not just the YAW sensor. So even if the YAW sensor was giving it a wacky single to the computer you would most likely get a service stability control message not the stability control being enabled.


And its fine what we disagree (part of the fun in life) it would just seem if you make the comments less personal attacks and more about the subject we could all share and learn more about a subject that non of us are experts in.

UnsafeAtAnySpd

You get both. On the track after about five minutes or so the service stability system soon message appears. I'm assuming, even with the system deactivated, the car is still receiving the inputs and thus registers this message. It doesn't happen for a while though.


Anyway... "There's something on the airfoil!"

NIKDSC5

iTrader: (10)

Turbulence under the wing (yup a planes airfoil is the wing) will cause drag, not lift. And likewise for helpful comments.