NA6 Intake/Exhaust Mods

[PaulF]

They seem to me to be like the mania setup, perhaps better than stock but in no way designed for maximum performance.

What's the difference between yours and the Mania setup, other than the price and the fact that you were really anal about making sure it was perfectly sealed?

[Cerberus]

I will let it be known I am no expert in this field.

But the idea of taking the intake tract away from next to the exhaust manifold seems like a good idea.

As for the high/low pressure areas I know very little.
I understand a certain amount of pressure in the intake is required to improve the airflow speed and torque curve but am unsure what the best route to take would be.

Benefits/detriments of shorter intake tract?
I dont like the idea/look of the cowled firewall intakes.

What say you?

[gslender]

If they take air from the bumper/bonnet gap no way. Thats a super low pressure zone and is sucking air out of the engine.

How do you know that? Can you explain in detail or is this just your guess?

G

[NitroDann]

You can find many diagrams all over the interwebs showing the pressure across an mx5 bonnet. Including some wind tunnel pressure maps.

For an explanation thats easy, think of a wing, from the bottom of the windscreen forward the mx5 (and almost every car) is shaped like the leading edge of an aeroplane wing, with the flat bottom and curved top. Look at an mx5 side on, then look at a wing cross section with google images.

This is why we get lift at high speed. this is also why extraction hoods work.

PaulF:

My intake is sealed which is one big one. Its not just sealed to the filter, its sealed together completely and sealed into the cowl hole. The other major difference is heat shielding. Along with my extractors heat wrapped and sheilded, the intake itself has 2 layers of sheilding. as SHOULD my intake pipe, which Ill be fixing during my saga.

The bloke who said he wasnt sure about pressures. think of a turbo, it pushes air in pressurised, so there more oxygen atoms to burn with more fuel and make more power.

For example, a Subaru WRXs turbo pushes in 7 PSI of pressure (boost). at 100km/h my intake pushes in a tad over 1psi.

If somebody requests it in my build thread, ill happily dissassemble my intake and show how its made and why it all works so well.

Dann

[Hjt]

or they can get some sealant and extra heat-shielding added to there existing mania intakes?...

[NitroDann]

They sure could. But that would defeat the purpose of buying one wouldnt it?

Dann

[Hjt]

yeah but some people purchase cars with them already installed etc.. mine i just have the stock airbox with a bendy aluminium pipe heading down to some sexy airflow areas

[gslender]

You can find many diagrams all over the interwebs showing the pressure across an mx5 bonnet. Including some wind tunnel pressure maps.

For an explanation thats easy, think of a wing, from the bottom of the windscreen forward the mx5 (and almost every car) is shaped like the leading edge of an aeroplane wing, with the flat bottom and curved top. Look at an mx5 side on, then look at a wing cross section with google images.

This is why we get lift at high speed. this is also why extraction hoods work.

That explains why the cowl intakes work, it doesn't explain why the intake that takes cold air from between the hood gap is a "low pressure zone and sucks air out of the engine". You repeatedly (from other posts) claim this area to be no good but you never explain why. If JR thought it was worth doing, and they have a fairly good reputation for engineering, don't you think the science of air ramming into the massive sized mouth having positive pressure would push air into that gap between the hood and the top of the radiator. The air isn't going to easily push through the radiator, fans and engine block without some of it wanting to positively push into that intake duct???

I mean, your relying on air to positively push through the cowl area, turn 90 degrees etc and that isn't the most aero-dynamic place for tunneling air!

G

[NitroDann]

It doesnt work because its a low pressure area at the hood bumper panel gap. This is true because air pressure maps say so. Ones available on the net that are from mx5s in wind tunnels.

Testing it with a piece of wool shows the same thing.

The intake gets its air from its opening, buy a manometer and find out if its above 101kpa at speed (or whatever air pressure is at that time and place). The intake is not sealed to the rad opening. Its left open to just get air from above it, inside the engine bay, just like stock but in front of the heat.

Jr makes them because people buy them and on a dyno it makes marginally more power due to cooler air in a dyno situation, because unlike the stock airbox its unlikely to heatsoak quickly. This leads people to believe that they improve performance.

Dynos dont go 200kph and generate high and low pressure areas though do they?

Dann

[gslender]

Rofl.

Dann, I don't think you understand where the JR gets it's air from. Lol. I've just figured out why you think it's so bad, and your are right, if it was getting air through that ridiculously small panel gap between the bumper and hood (facing up across the wash of the bonnet), you'd be right.

It's not though!

Air comes in through the grill (mouth area where you've installed your brake ducts) - it then can only go through the radiator or before that, in any direction that has an opening. The intake is facing forward, over the radiator in a 1 inch gap where the hood latch is. You can see down into the grill/mouth area..... That area is a MASSIVE positive area due to the fact it is a) in front of the car, and b) because all of the cooling junk in the way. Air would pressurize that 1 inch gap.

I want to understand why you think it can't (perhaps a drawing showing you understand how the JR system works would help)

G

[NitroDann]

I understand that it has its intake mouth between the radiator support panel and bonnet. And the air is SUPPOSED to go around the radiator through the gap between the radiator and the bumper and into the intake, but the panel gap above it creates suction and the intake mouth is not sealed to the high pressure area in front of the rad, so whos to know what the pressure there is? Its essentially just at the front of the engine bay, but its still inside the engine bay, just like stock.

Dann

[gslender]

Ones available on the net that are from mx5s in wind tunnels.

Testing it with a piece of wool shows the same thing.

Dude, those two statements are classic.

The first is a "I have seen pressure maps" but no link so no one can dispute this. I just Googled and can't find any. Share the Google search phrase...?

The seconds tells me you don't understand - the piece of wool trick is used outside the car, not inside under the hood where you can't see why driving along. Lol. So I put the wool where, inside the grill mouth? Are you honestly saying it won't be rushing into the radiator? If thats your point, then the eddie current you use in a cowl are the same when you look at that space above the radiator under the hood.

For your view to be correct, the radiator area would have to exit air at the exact same speed as it enters. If that is true, why did you build an air vent on the exit side? I guess you know that the air coming in can't escape fast enough, ergo there is a restriction which will result in the entire area being positively pressured at speed.

Lawyered!

G

[gslender]

but the panel gap above it creates suction and the intake mouth is not sealed

Perhaps on your track pig, but on my mx5 the hood is sealed against a rubber strip that would be sucked up and seal firmer (if indeed the air pressure was that strong between such a small panel gap) so I don't think so.

G

[NitroDann]

Im on a mobile phone so cant easily find the images or the links with info regarding manometer tests. The info regularly comes up on MT and Mnet in hood vent threads, showing the low pressure areas to vent from.

Yes there is high pressure air in front of the radiator.
Yes some of the air overflows the edges, but is it still high pressure when it does? how about when it gets a vacuum on it via the panel gap? How about when the area isnt sealed at all forwards and is just part of the engine bay airspace, aiming forward?

If it were designed for max performance like you think jr would have done, why no heat shields? Why no seals?

About the wool, what im saying is that if you tape wool to the panel gap you can see whether it gets sucked in or blown out.

Buy a manometer and find out. Ive not done the tests on that area but many have.

My intake produces over 1 psi of 'boost' by 100kph, theres no way the jr does this. And my intake gets air in within 6 degrees of ambient (max difference ive ever seen)

Dann

[Hjt]

Not to object to your comment Dan but the thermal qualities of the JR intake arnt as important as the stock intake box because of the placement and the lack of direct heat from the headers/extractors.

The JR intake is most definately an improvement from the stock setup, I think the best results would be from a pod filter exposed to the mouth of the car near the passengers side radiator outlet then into a large intake manifold like the ARC one, leading into the intake manifold.

All personal opinions though subject to test results