bonnet vents
11-06-2006, 10:12 PM
#62
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Porsche apparently considered vents on top of the engine- look at "Project 928" some time- it looks like they designed the car with vents built into the fenders, but deleted them after testing. I suspect they found little gain and lots of aesthetic destruction from these vents.
Wally pointed out something important: the 928 cooling system is designed to duct hot air around the bottom of the engine, and I suspect the faster you go the stronger the effect. I'm a pilot, and one thing I know for sure is that changing air flow doesn't always give you an advantage! It is easy to change airflow in ways that you think make sense, but actually hurt you. You boostards/racers go ahead and try adding vents to the hood- It will make for interesting reading, from my standpoint.
Aesthetic: Sorry, I think the long, curved hood is one of the best lines of the car, and to mar it with a vent is to throw paint on the Mona Lisa. It's your car- I APPLAUD the effort, but I sure as hell won't do this to my own S2!
N!
Wally pointed out something important: the 928 cooling system is designed to duct hot air around the bottom of the engine, and I suspect the faster you go the stronger the effect. I'm a pilot, and one thing I know for sure is that changing air flow doesn't always give you an advantage! It is easy to change airflow in ways that you think make sense, but actually hurt you. You boostards/racers go ahead and try adding vents to the hood- It will make for interesting reading, from my standpoint.
Aesthetic: Sorry, I think the long, curved hood is one of the best lines of the car, and to mar it with a vent is to throw paint on the Mona Lisa. It's your car- I APPLAUD the effort, but I sure as hell won't do this to my own S2!
N!
11-06-2006, 10:15 PM
#63
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YEah, gearing! Lmao....
Well, it looks like if you want to address creating a little less negative pressure, you should run about an 18 in heating duct from the engine compartment to the sunroof, since thats where there is REALLY low pressure...
Mark, I see what you are saying, and you are right about the fender ducts- IF you seal the fender to wheelwell with a flat sheet going straight up, instead of the formed piece we have now. As it is, the engine compartment is open to fender above the wheel because of the how the stock fender liner is formed. So, you should put the Aston vents in as shown above, but farther forward, and seal off the fenderliner and add vents in the fender to help even more...
Need to find somebody with a louver press...
Steve
Well, it looks like if you want to address creating a little less negative pressure, you should run about an 18 in heating duct from the engine compartment to the sunroof, since thats where there is REALLY low pressure...
Mark, I see what you are saying, and you are right about the fender ducts- IF you seal the fender to wheelwell with a flat sheet going straight up, instead of the formed piece we have now. As it is, the engine compartment is open to fender above the wheel because of the how the stock fender liner is formed. So, you should put the Aston vents in as shown above, but farther forward, and seal off the fenderliner and add vents in the fender to help even more...
Need to find somebody with a louver press...
Steve
11-06-2006, 10:59 PM
#64
Rennlist Member
sure, we are changing air flow from going around the engine to venting to a lower pressure area. all that would happen would be some greater downforce on the front of the car.
however, the body kit above, has the vents near the base of the windshield, clearly in the higher pressure zone. all that would do would be to push air down into the engine compartement, that is if you believe the 928 pressure profiles.
i tend to agree about the asthetics, however, if i can avoid this by using a bigger splitter, ill go this route.
mk
however, the body kit above, has the vents near the base of the windshield, clearly in the higher pressure zone. all that would do would be to push air down into the engine compartement, that is if you believe the 928 pressure profiles.
i tend to agree about the asthetics, however, if i can avoid this by using a bigger splitter, ill go this route.
mk
Originally Posted by Normy
Porsche apparently considered vents on top of the engine- look at "Project 928" some time- it looks like they designed the car with vents built into the fenders, but deleted them after testing. I suspect they found little gain and lots of aesthetic destruction from these vents.
Wally pointed out something important: the 928 cooling system is designed to duct hot air around the bottom of the engine, and I suspect the faster you go the stronger the effect. I'm a pilot, and one thing I know for sure is that changing air flow doesn't always give you an advantage! It is easy to change airflow in ways that you think make sense, but actually hurt you. You boostards/racers go ahead and try adding vents to the hood- It will make for interesting reading, from my standpoint.
Aesthetic: Sorry, I think the long, curved hood is one of the best lines of the car, and to mar it with a vent is to throw paint on the Mona Lisa. It's your car- I APPLAUD the effort, but I sure as hell won't do this to my own S2!
N!
Wally pointed out something important: the 928 cooling system is designed to duct hot air around the bottom of the engine, and I suspect the faster you go the stronger the effect. I'm a pilot, and one thing I know for sure is that changing air flow doesn't always give you an advantage! It is easy to change airflow in ways that you think make sense, but actually hurt you. You boostards/racers go ahead and try adding vents to the hood- It will make for interesting reading, from my standpoint.
Aesthetic: Sorry, I think the long, curved hood is one of the best lines of the car, and to mar it with a vent is to throw paint on the Mona Lisa. It's your car- I APPLAUD the effort, but I sure as hell won't do this to my own S2!
N!
11-07-2006, 04:31 AM
#65
Drifting
Thread Starter
i disagree about the aesthetics if done nicely aka fat bully/pierre martins car. he has integrated the vents really nicely and in such a way that the aesthetic is enhanced imo - im not making any such claims about mine except that i like them i think they make my car look more like a racer for sure - the warm air coming back through the hvac will be a problem in summer but at least ive got a few months till i need to worry about that!
in terms of pressure i think that right about the level of the strut brace is optimum.
i think they make my car look more like a racer for sure - the warm air coming back through the hvac will be a problem in summer but at least ive got a few months till i need to worry about that! in terms of pressure i think that right about the level of the strut brace is optimum.
11-07-2006, 09:15 AM
#67
Drifting
Nick, pierre's vents look like they would be good for ram air effect on intake air. Also for under hood temp reduction I have read that "header wrap" around your exhaust manifolds would reduce temps by 30 degrees F. Have you done that?
Does anyone know if header wrap would be good or bad to the longevity of the HEAVY and THICK stock manifolds on a euro S2. I had heard the extra heat would somehow corrode the metal. They are so thick i have trouble believing that. Anyone know?
Does anyone know if header wrap would be good or bad to the longevity of the HEAVY and THICK stock manifolds on a euro S2. I had heard the extra heat would somehow corrode the metal. They are so thick i have trouble believing that. Anyone know?
11-07-2006, 02:43 PM
#68
Drifting
Thread Starter
tv, if you look closely, (appologies if you see them already )as well as the forward facing intake scoops on pierres bonnet there are also gill like openings further back and these are the type of vent that i first had in mind - only i would have put them further forward. my gts engine has header wrap around the manifolds, i dont imagine it will affect the header longevity one way or the other.
)as well as the forward facing intake scoops on pierres bonnet there are also gill like openings further back and these are the type of vent that i first had in mind - only i would have put them further forward. my gts engine has header wrap around the manifolds, i dont imagine it will affect the header longevity one way or the other.
11-07-2006, 02:52 PM
#69
Rennlist Member
right! the vents toward the back are too far to the rear, and the inlets for ram air are useless as that is not a high pressure zone. (the nose would be). In fact, there is no ram air as there is a vacuum present at any point on top of the hood, until you get toward the base of the windshield. he would be better off using the rear vents for intake and the front vents for engine bay air to escape. the air flow stuff is not as intuitive as it seems. the maximum vacuum is right where the intake inlets are position. nice for looks, bad for performance. the stock source for air is pretty darn good, as its right below the nose where there is some pressure increase to be found.
From the diagram, having the vents around the cross bar is the max vacuum to vent the hood from. intake should be at the nose as comes stock with a 928 or the base of the windshield. (or both as i have it)
MK
From the diagram, having the vents around the cross bar is the max vacuum to vent the hood from. intake should be at the nose as comes stock with a 928 or the base of the windshield. (or both as i have it)
MK
Originally Posted by drnick
tv, if you look closely, (appologies if you see them already )as well as the forward facing intake scoops on pierres bonnet there are also gill like openings further back and these are the type of vent that i first had in mind - only i would have put them further forward. my gts engine has header wrap around the manifolds, i dont imagine it will affect the header longevity one way or the other.
)as well as the forward facing intake scoops on pierres bonnet there are also gill like openings further back and these are the type of vent that i first had in mind - only i would have put them further forward. my gts engine has header wrap around the manifolds, i dont imagine it will affect the header longevity one way or the other.
11-07-2006, 03:17 PM
#70
Rennlist Member
looks like these are just in the range of low pressure to get the air from entering the radiator (high pressure) to exit at these vents. they look pretty good too. im not crazy about the bolt-on (rivet-on) solutions. i think a neat screen can do the trick like on the austin martin DB9 or Vanquish.
how did you cut those holes ? dremmel, or something more sophisticated.
I think im going to lean on doing either the vents like this, or the austin martin style with a screen.
Mk
how did you cut those holes ? dremmel, or something more sophisticated.
I think im going to lean on doing either the vents like this, or the austin martin style with a screen.
Mk
Originally Posted by jorj7
Nick,
I cut some slits in my hood last year to help get the heat out from under the hood. I was
going to put them behind the radiator, but Marc T. advised me to move them further back,
about even with the rear of the wheel well. This would allow the most hot air out.
Here is a photo of Bill B helping me put the hood on:
I did seem to help keep the engine cooler. By the way, the hood was donated
by Beth and repainted to match my car.
I cut some slits in my hood last year to help get the heat out from under the hood. I was
going to put them behind the radiator, but Marc T. advised me to move them further back,
about even with the rear of the wheel well. This would allow the most hot air out.
Here is a photo of Bill B helping me put the hood on:
I did seem to help keep the engine cooler. By the way, the hood was donated
by Beth and repainted to match my car.
11-07-2006, 07:36 PM
#72
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Mark,
The vents in my car were cut with an air powered rotary saw at D&M Auto Body in Albany.
They also painted the blue hood to match my white car.
By the way, I made them that width so that I could tape over them with
racers tape if it rained.
The vents in my car were cut with an air powered rotary saw at D&M Auto Body in Albany.
They also painted the blue hood to match my white car.
By the way, I made them that width so that I could tape over them with
racers tape if it rained.
11-07-2006, 08:25 PM
#73
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Most cars these days are engineered for under-car air evacuation. The air dams are not just designed to suck the car to the pavement, they are there to pull air through the radiator. I suspect that metal parts installed UNDER the car can have a far greater effect on air flow through the radiator!
This is all a moot point. There's nothing wrong with the stock radiator and the stock air flow, up to the level of Mark Thomas' 211 mph Silver State Challenge car. Adding vents to the hood should be done for aesthetic purposes, since I'm sure that they acheive nothing at all, performance wise.
I applaud anyone who tries something different! At the same time, I can tell you I will NEVER put any sort of vent on my own hood, thus ruining one of the best curves the car has.
B safe!
N!
This is all a moot point. There's nothing wrong with the stock radiator and the stock air flow, up to the level of Mark Thomas' 211 mph Silver State Challenge car. Adding vents to the hood should be done for aesthetic purposes, since I'm sure that they acheive nothing at all, performance wise.
I applaud anyone who tries something different! At the same time, I can tell you I will NEVER put any sort of vent on my own hood, thus ruining one of the best curves the car has.
B safe!
N!
11-07-2006, 09:11 PM
#74
Rennlist Member
actually, Ive never questioned the cooling, as both mark anderson and me are still using stock radiators. The cooling is not determined by "pulling " of air through the radiator, but its the pressure generated in front of it. the design of the 928 S4 and pre S4 is to have a high pressure area at just below the bumper to create a sizable pressure region to push air through the radiator. however, that air has to exit somewhere, and that somewhere is a region of lower pressure. if that lower pressure is underneath the car, then the air will go there. however, if you have vents to the top of the hood, then that area being of lower pressure than underneath the car, will direct the air flow on top of the car creating some sizable downforce. downforce is the only thing really produced by hood vents (besides some small temp changes in the engine bay)
im debating doing any cutting for the reason you mention below! tough call. the question is , how much downforce will i gain and can i gain it by making a more efficient splitter.
Mk
im debating doing any cutting for the reason you mention below! tough call. the question is , how much downforce will i gain and can i gain it by making a more efficient splitter.
Mk
Originally Posted by Normy
Most cars these days are engineered for under-car air evacuation. The air dams are not just designed to suck the car to the pavement, they are there to pull air through the radiator. I suspect that metal parts installed UNDER the car can have a far greater effect on air flow through the radiator!
This is all a moot point. There's nothing wrong with the stock radiator and the stock air flow, up to the level of Mark Thomas' 211 mph Silver State Challenge car. Adding vents to the hood should be done for aesthetic purposes, since I'm sure that they acheive nothing at all, performance wise.
I applaud anyone who tries something different! At the same time, I can tell you I will NEVER put any sort of vent on my own hood, thus ruining one of the best curves the car has.
B safe!
N!
This is all a moot point. There's nothing wrong with the stock radiator and the stock air flow, up to the level of Mark Thomas' 211 mph Silver State Challenge car. Adding vents to the hood should be done for aesthetic purposes, since I'm sure that they acheive nothing at all, performance wise.
I applaud anyone who tries something different! At the same time, I can tell you I will NEVER put any sort of vent on my own hood, thus ruining one of the best curves the car has.
B safe!
N!
11-08-2006, 04:31 AM
#75
Drifting
Thread Starter
normy, as you can see from the pic of my car this is less of a moot point as my whole front end is non standard - and ive added the vents my front nose clip seems not as efficient at creating the high pressure to force air through the radiator. the other day while driving through france on our way to the ring i picked up some leaves into the front grill and the temp started climbing. the thing that surprised me was that there were not so many leaves covering the grill and it seemed they were mainly collected along the lower edge, as if the pressure distribution was not even... the actual area of high pressure feeding my rad may be reduced.
as for the white car i recall the devek site saying something about there need for a larger radiator than stock (modified stock i think) and also raising the rear edge of the bonnet to improve cooling.
anyway your point is moot because the 928 is not most cars, it is a supercar and most supercars try not to disturb the underfloor airflow with turbulent hot air - and you arent allowed to cut holes in your bonnet unless you are racing or adding a bodykit
mark, the engine running temp on my car dropped through adding the vents enough that i can easily see it in the capilliary gauge i have installed - maybe 5 degrees centigrade average - but less at high speeds. i think you should vent your hood for the downforce and add the improved splitter as well, following the motto if some is good more is better! id go for the mesh screen, i was thinking that would look after after i had the holes cut.
my front nose clip seems not as efficient at creating the high pressure to force air through the radiator. the other day while driving through france on our way to the ring i picked up some leaves into the front grill and the temp started climbing. the thing that surprised me was that there were not so many leaves covering the grill and it seemed they were mainly collected along the lower edge, as if the pressure distribution was not even... the actual area of high pressure feeding my rad may be reduced.as for the white car i recall the devek site saying something about there need for a larger radiator than stock (modified stock i think) and also raising the rear edge of the bonnet to improve cooling.
anyway your point is moot because the 928 is not most cars, it is a supercar and most supercars try not to disturb the underfloor airflow with turbulent hot air - and you arent allowed to cut holes in your bonnet unless you are racing or adding a bodykit
mark, the engine running temp on my car dropped through adding the vents enough that i can easily see it in the capilliary gauge i have installed - maybe 5 degrees centigrade average - but less at high speeds. i think you should vent your hood for the downforce and add the improved splitter as well, following the motto if some is good more is better! id go for the mesh screen, i was thinking that would look after after i had the holes cut.