Just saying hello and showing off an rx8
04-12-2005, 04:17 PM
#27
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Where's your team going to race? What city or cities? That must be real fun pushing the 8 like that. :D Dont be offended by any remarks on this forum btw. We're all a bunch of hard headed bastards. 
04-12-2005, 06:42 PM
#30
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I think I know what this "secret" is in terms of their exhaust design. It isn't so much a secret as it is common sense when applies to aerodynamics and pressures. Strangely enough there are many race teams out there that haven't figured this out yet. I don't know why. It's fairly obvious if you just think about it.
Think about this. What is everyone's goal in terms of a new intake? It's usually "ram air". By placing the air intake at the highest pressure point of the vehicle, we can get more air into the engine than simply letting it suck it in on it's own. Let's apply this to exhaust. If we want to get more air into an engine, we place the inlet in a high pressure zone. If we want to get more out we should put the exhaust outlet in the lowest pressure zone. If pressure at spots is lower than ambient you will actually get a suction effect on the engine and it will help pull gasses out of the engine. This should hold true regardless of the exhaust system being used.
He mentioned that the exhaust exits the center of the car. The benefit isn't because it is a straighter path (it is). The benefit comes from the fact that the center rear of the car is lower in pressure than on the edges of the bumper where the stock tips are. Air is spilling past the outsides of the bumper at speed and causing some turbulence and pressures to be exerted on the exiting exhaust air in the stock location. This isn't happening near as much at the center of the rear. They are getting more of a scavenging effect at higher speeds because of this. On a race track this adds up to higher speeds on the straights.
Alot of companies/race teams use various testing methods to determine aerodynamics and power. However they only test one aspect at a time. This team has obviously done their research as I doubt highly that this system was designed on the dyno but rather on a track where it counts. Here are 2 big problems with standard testing methods. When was the last time you saw a car in a wind tunnel with a running engine? When was the last time you saw a moving car on a dyno? Aerodynamics and power both play a combined role on each other but from static testing of only a single method at a time, you'd never know it.
Think of the shape of the air that is being punched by a moving car. The perfect shape is like a rain drop. It gradually tapers off to a point behind the car. What happens to this shape if we have rushing exhaust gasses going out the side of the car or somewhere else into the high pressure air stream? This shape is altered. You wouldn't see this in a wind tunnel without the engine running. When you alter this shape, you make the hole you are punching through the air larger. You also make it longer. The longer the hole that you punched in the air is, the easier it is for the guy behind you to draft you! Bad idea in a race. By carefully selecting your exhaust outlet point, you can minimize this hole which will make it harder for the guy behind you to draft but more importantly your coefficient of drag will decrease and you'll go faster. As an added benefit you now also have a greater scavenging exhaust and are making more power. The guys behind you will swear that you can't be drafted. That's a good thing in a race.
It's amazing how something so minor can make such a large difference. I guess if the other teams don't know this it could be considered a "secret". It's really just common sense though. If they'd angle their exhaust tips up a few degrees, the benefit will be even greater as the exhaust is directed to the center of the low pressure aerodynamic cone behind the car. Of course I'm no aerodynamic engineer so what do I know.
Again, I never intended to bash or come across as harsh in previous posts. That wasn't the intention.
Think about this. What is everyone's goal in terms of a new intake? It's usually "ram air". By placing the air intake at the highest pressure point of the vehicle, we can get more air into the engine than simply letting it suck it in on it's own. Let's apply this to exhaust. If we want to get more air into an engine, we place the inlet in a high pressure zone. If we want to get more out we should put the exhaust outlet in the lowest pressure zone. If pressure at spots is lower than ambient you will actually get a suction effect on the engine and it will help pull gasses out of the engine. This should hold true regardless of the exhaust system being used.
He mentioned that the exhaust exits the center of the car. The benefit isn't because it is a straighter path (it is). The benefit comes from the fact that the center rear of the car is lower in pressure than on the edges of the bumper where the stock tips are. Air is spilling past the outsides of the bumper at speed and causing some turbulence and pressures to be exerted on the exiting exhaust air in the stock location. This isn't happening near as much at the center of the rear. They are getting more of a scavenging effect at higher speeds because of this. On a race track this adds up to higher speeds on the straights.
Alot of companies/race teams use various testing methods to determine aerodynamics and power. However they only test one aspect at a time. This team has obviously done their research as I doubt highly that this system was designed on the dyno but rather on a track where it counts. Here are 2 big problems with standard testing methods. When was the last time you saw a car in a wind tunnel with a running engine? When was the last time you saw a moving car on a dyno? Aerodynamics and power both play a combined role on each other but from static testing of only a single method at a time, you'd never know it.
Think of the shape of the air that is being punched by a moving car. The perfect shape is like a rain drop. It gradually tapers off to a point behind the car. What happens to this shape if we have rushing exhaust gasses going out the side of the car or somewhere else into the high pressure air stream? This shape is altered. You wouldn't see this in a wind tunnel without the engine running. When you alter this shape, you make the hole you are punching through the air larger. You also make it longer. The longer the hole that you punched in the air is, the easier it is for the guy behind you to draft you! Bad idea in a race. By carefully selecting your exhaust outlet point, you can minimize this hole which will make it harder for the guy behind you to draft but more importantly your coefficient of drag will decrease and you'll go faster. As an added benefit you now also have a greater scavenging exhaust and are making more power. The guys behind you will swear that you can't be drafted. That's a good thing in a race.
It's amazing how something so minor can make such a large difference. I guess if the other teams don't know this it could be considered a "secret". It's really just common sense though. If they'd angle their exhaust tips up a few degrees, the benefit will be even greater as the exhaust is directed to the center of the low pressure aerodynamic cone behind the car. Of course I'm no aerodynamic engineer so what do I know.
Again, I never intended to bash or come across as harsh in previous posts. That wasn't the intention.
Last edited by rotarygod; 04-12-2005 at 06:45 PM.
04-12-2005, 08:38 PM
#32
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The exhaust does need some backpressure. THe muffler is there for noise and to help something in the power band...not really sure...I am the driver not the mechanic. The wheels that were on there are some junkie ones and we run 225 allthe way around. WE now have ssr type C rims. the suspension is JIC Flt-a2's race version. We are in laguna seca the 29th through the 1st. and then canada i belive is next. I'll keep everyone posted on the updates. I appreciate all criticism.
There is alot of relavance. I belived he used a trirotor in the boat.
There is more to the exhaust than one meets the eye. but alot of tunning and hours on the dyno are key as well.
There is alot of relavance. I belived he used a trirotor in the boat.
There is more to the exhaust than one meets the eye. but alot of tunning and hours on the dyno are key as well.
04-12-2005, 08:41 PM
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rotarygod is right. THe aerodynamics of the car. This is the reason why we don't run the mazda speed kit like most people also allows us run lower than our competitors.
also allows us run lower than our competitors.
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