[Guest]

Sorry guys, but at any speed above 5mph I've seen no evidence of reverse air flow though the roof scoop. I've put a data logging air flow meter at various points behind the intercooler, and have taken a few hours worth of data at various speeds and weather conditions. I haven't taken data with the roof removed, so it's possible that reverse flow can occur at higher speeds without the roof... but given the data that I've logged, I'm very skeptical that there's any reverse flow at any significant forward speed with either the "S" roof or the Cup roof.

Thank you! Your data also proves my point.

:coolnana:

 

[L 33 HAW]

This is just based on my personal experience-------I have no data to support these conclusions.
I was driving my 240S around without the top,and while I was sitting at a light-ambient was about 85F-I could actually feel warm air-certainly warmer than ambient-coming out of my air intake. This was not a track day,and I was not driving it hard at all. Based on this,I have got to believe that the loss of HP is fairly severe without the top on. Again,I have no data to back this up. The wind buffeting(which I really don't care about) is much more pronounced in an Exige with the top off than it was with an Elise under the same conditions,which makes sense----and I am sure that the airflow to the wing is totally upset. If only someone made a scoop to use while the top is off,that might help. I can't imagine safety being a concern-do you mean in a rollover?
That said, on a beautiful summer or spring day,these things don't bother me-----For a track day,they would be a serious concern. This is on a totally stock 240S,I have Thomasio's intercooler but haven't installed it yet.
I still like the idea of a NACA duct on the drivers side sail panel,and the photo of the ducted air to the IC duct would also seem to be viable,but,of course,only when the car is in motion. I also noticed with the top off,when moving, the air coming over the windscreen is indeed warmer than ambient,but at the center of the windscreen(where the scoop would pick it up) it is actually cooler than the other spots!:wallbang::wallbang::wallbang::wallbang:

Sorry i dont mean safety if you were to roll over, but whether there could be damage to the intercooler/supercharger if poor airflow was apparent. I understand the roof scoop has no bearing on the engines cooling as a whole, but wasnt sure if the supercharger side of things could get damaged.

I think everyone agrees that if on track, or driving hard everyone keeps the roof on. But it would be nice to confirm for sure if driving topless on a sunny day will not cause any problems.

 

[Mag]

Sorry i dont mean safety if you were to roll over, but whether there could be damage to the intercooler/supercharger if poor airflow was apparent. I understand the roof scoop has no bearing on the engines cooling as a whole, but wasnt sure if the supercharger side of things could get damaged.

I think everyone agrees that if on track, or driving hard everyone keeps the roof on. But it would be nice to confirm for sure if driving topless on a sunny day will not cause any problems.

Poor airflow is an issue with or with out the roof on. The car is spec'd to run with out good flow albeit inefficiently, but safely. However lowering temps will maximize the car's performance potential and increase safe operating parameters when driving hard. higher engine temps decrease performance efficiency, and even higher temps than that cause engine damage. The latter is very difficult to achieve unless the car is driven very hard in very severe temps. If you want to cruise top off, it's IMO that would be totally "safe".

Top off (normal driving), IC will be fine, SC will be fine. Just keep an eye on the water temp, ease off when it gets over 100C.

 

[ericwgexige]

I'm not sure how to square your data with what I experienced driving with the top off. All I did was reach over my shoulder at about 20, 40, and 60 mph, and actually insert my hand into the air intake. The air inside the opening was quite hot and was exiting the opening where the roof scoop would normally match up. Anyone with an Exige S could easily duplicate this. To be honest though, this information doesn't seem that important, since the car was not intended to be driven this way. It also makes sense that this would occur with all of the buffeting air around the passenger compartment opening. The air running over the top of the car when the roof is in place is certainly much, much smoother and cleaner.

 

[robains]

I just finished opening up my mail box on my 07 S today. I also found a good misting spray nozzle and installed that. Now for the bad news, the GM water pump used in the windshield spray tank is a joke -- tested with it and all I got was short pulse of next to no pressure, it was beyond pathetic.

So I'm searching for a high pressure water pump for 12v DC and the only thing I've found is a Shurflow which can only do 130 psi max. After searching the net some I'm finding out that true mist systems (multi-nozzle) are running at 800-1000 PSI, weigh A LOT, very large, and some want 230 v 10amps+

I'm thinking I could probably get away with 200 psi unit for a single mist nozzle, but there are none to be found for 12v DC.

So in a word, external water mist on IC doesn't appear to be a workable reality until someone can produce small efficient light weight pump.

I've been made aware of a "yet to be released" alternative ... stay tuned.

 

[Illumiloti]

Sorry i dont mean safety if you were to roll over, but whether there could be damage to the intercooler/supercharger if poor airflow was apparent. I understand the roof scoop has no bearing on the engines cooling as a whole, but wasnt sure if the supercharger side of things could get damaged.

I think everyone agrees that if on track, or driving hard everyone keeps the roof on. But it would be nice to confirm for sure if driving topless on a sunny day will not cause any problems.

Well, since Lotus now sells an Elise which is supercharged and they don't even bother to put an intercooler on, I think that answers your question. The bottom line from all this testing is that there simply is not enough airflow through the "mail chute" at the top of the clam (or the back of the roof that connects to it) to allow the intercooler to do it's job and prevent heatsoak. So roof on/ roof off ultimately doesn't matter (regardless of what the salesperson at the dealership tells you). You're just gonna lose a bit of power once everything gets hot.

 

[Chris A]

I just finished opening up my mail box on my 07 S today. I also found a good misting spray nozzle and installed that. Now for the bad news, the GM water pump used in the windshield spray tank is a joke -- tested with it and all I got was short pulse of next to no pressure, it was beyond pathetic.

So I'm searching for a high pressure water pump for 12v DC and the only thing I've found is a Shurflow which can only do 130 psi max. After searching the net some I'm finding out that true mist systems (multi-nozzle) are running at 800-1000 PSI, weigh A LOT, very large, and some want 230 v 10amps+

I'm thinking I could probably get away with 200 psi unit for a single mist nozzle, but there are none to be found for 12v DC.

So in a word, external water mist on IC doesn't appear to be a workable reality until someone can produce small efficient light weight pump.

I've been made aware of a "yet to be released" alternative ... stay tuned.

How about this unit? I'm thinking about using it on one of my cars.

New High Performance Rapid Cool Radiator Mist System

 

[robains]

From the pic of the unit, that pump looks to be exactly like the GM pump used in the Lotus washer unit -- for long repeated spray durations it'll just burn out the pump. I couldn't see any specs on the pump at all.

1 or 2 Mist Jet Application for Maximum Coverage and Effectiveness

1 or 2?? Errrr...that isn't gonna do much good -- assuming it can even generate a "mist".

70 PSI 12v DC Flojet and this is about 12X larger than the pump you see in your link.

I've seen some smaller high pressure pumps, but that can't run for more than about 9 seconds and MUST cool down for a period before. I've also used a Shurflow 45 psi pump on an 04 STi and it wasn't able to really product a mist.

I've been searching and the more I search the less I find of intercooler misting systems that are viable for track duty.

The closest kit that might work (intended for home use) is this Unit from EZ Mister

 

[Chris A]

Not sure why this needs to be high pressue......Looks like the Hayden unit is designed speciffically for this application. I don't think you really want to douse the back of the engine compartment with water.


But...How about this system? Seine Systems > MPC

 

[Smoky]

Well, since Lotus now sells an Elise which is supercharged and they don't even bother to put an intercooler on, I think that answers your question. The bottom line from all this testing is that there simply is not enough airflow through the "mail chute" at the top of the clam (or the back of the roof that connects to it) to allow the intercooler to do it's job and prevent heatsoak. So roof on/ roof off ultimately doesn't matter (regardless of what the salesperson at the dealership tells you). You're just gonna lose a bit of power once everything gets hot.

They are using different s/c's in the s/c Elise. It is smaller, and doesn't *NEED* an intercooler (but should still have one, based on forum reports).

 

[robains]

Chris,

The pressure is needed so that you do NOT just spray water on the IC (this does more harm than good), the mist style nozzle doesn't "flow" a lot of water, it mists (very very small hole). The high pressure is needed to be able to atomize the water as much as possible thru this tiny hole -- as that is what truely cools the IC -- the mix of cool water vapor with the air flow -- best case is you can drop air temp over the IC by 35 degrees F. But misting takes pressure, lots of it.

 

[Ken Wright]

Well, since Lotus now sells an Elise which is supercharged and they don't even bother to put an intercooler on, I think that answers your question. The bottom line from all this testing is that there simply is not enough airflow through the "mail chute" at the top of the clam (or the back of the roof that connects to it) to allow the intercooler to do it's job and prevent heatsoak. So roof on/ roof off ultimately doesn't matter (regardless of what the salesperson at the dealership tells you). You're just gonna lose a bit of power once everything gets hot.

This is exactly why I bought the side intake kit and the larger side intake scoops.

ken

 

[EricH]

Chris, ...The pressure is needed so that you do NOT just spray water on the IC (this does more harm than good)...

I am not saying that a fine mist is not better but, just curious how would spraying water in any fashion (assuming its colder than the intercooler) do more harm than good?

My wife's old '05 WRX STI came stock with an intercooler sprayer... only on when a button was pressed (I rather have one activated automatically) but it was a low-pressure sprayer.. moreso like your windshield washers than some high pressure fuel injector-like mist sprayer.

 

[IamBatman]

I'm not convinced you need a lot of pressure to produce a decent mist. Those personal spray misters (you manually pump to pressurize the plastic bottle a few times and it sprays a mist to cool you) can't possibly be over 60psi and the mist is fine enough imho for intake cooling. I think its more important to look at nozzle orifice size/design and pump reliability over just pump pressure. What about those in-line fuel pumps you can buy off Jegs or Summit racing catalogs? They are probably overkill for the volume/pressure???

I still think the fans + temperature switch are the simplest and most elegant solution for most road use/weekend track applications.

 

[robains]

The Harm it does:

1. Doesn't actually cool the air flowing over the IC, in fact, it will most likely just generate more heat as the water turns to steam once it hits the hot IC and or engine which will generate a burst of hot steam to make things even hotter.
2. Rear tires (Hoosiers in my case) don't react well to water dripping on them and probably wasn't too good for anyone who might be following.

The water spray ultimately just heats up the IC and can cause the engine to start to detonate -- this has happened to my OLD 04 STi and to a friend's 03 WRX until we both removed the water spray and the detonation went away. Spraying with more water doesn't help either, I went thru 3 gallons per track session on my STi and it didn't help heat soak at all -- my lap times didn't change much with or without water spray.

When you go into a Sauna and want to generate some heat, what do ya do, you take a cup of water next to the heater and dump it on the hot rocks which in turn generates a ton of steam with heats up the Sauna more. This is exactly what you are doing if you just spray water on a hot IC and/or Engine.

 

[Monsi]

the laws of thermodynamics have a couple issues with your first statement there

 

[Chris A]

the laws of thermodynamics have a couple issues with your first statement there

I concur....as well as the last one

 

[robains]

All ears if you folks would like to provide details.

For any benefit, you want to cool the air going over the IC, not spray water on the IC. Have you stood under a misting system in 100+ degree ambient, it does indeed cool the air, and those systems run 800-1000 psi (10 nozzles).

But try it -- I sprayed water on my IC and my IAT went up, not down. Only when I really hosed down the IC with 4 gallons (aprox) of water continously from a garden hose did I seem IAT go down. So lets be realistic, unless your drive with 100 gallons of water in your car, a water sprayer isn't helping.

 

[IamBatman]

when water evaporates or converts from liquid to gas form, it absorbs heat and pulls heat away from the air/part it contacts. (thats why those misting devices work so well.) Water can not create heat or cause an increase temperature in the part, unless the water itself is hotter then the part it touches.

When you drip water onto a sauna, it is pulling heat away from the hot rocks into the air, it is not creating heat. It is simply not possible to create heat unless you have a chemical or atomic reaction. The water is cooling the rocks, part of the energy went to converting the H20 to gas form, part of it went to warming the air/steam.

I have no idea what happened with your IAT, but Subaru would not put sprayers on IC to decrease performance & reliability of the car. Spraying outside of the IC is not as efficient as spraying directly into the intake air, but it should reduce the temperature slightly.

 

[robains]

if you spray water on the IC it converts to steam which is then pushed thru the IC which in turn does NOT cool the IC.

Misting is performed on the incoming air to cool the air which then cools the IC.

I agree with you is some ways but you are removing the air flow from the equation/context -- yes you convert the heat into steam and reduce IC temp, but the steam immediately then flows over IC increasing it's temp.

The Subaru sprayer is manual, not automatic, and it wouldn't be the first time a gimic device has been but on a car...happens all the time.

I do have an idea, the water went thru the IC onto the hot engine which then converted the water to steam which raises up towards the IC which in turn heats the IC, not cools it.

The key here is to mist the air flowing OVER the IC, not to spray water ON the IC. You want the air to be cooled and water free by the time it passes thru the IC.