Bonnet Scoop - Air Vents for Cooling

[fastfreddygassit]

I am no expert in engine performance but what I am hoping to acheive is to "push" as much cold air in to the air filter as possible rather than having the engine struggling to "suck air through a straw", hence I need to locate the best high pressure air location and catch as much air as possible. Does this principle seem sound in relation to engine performance or am I likely to cause more problems with the ECU etc?

What you are almost describing is a "ram air" system. These have been used on production motorcycles since the early 90's (zzr1100 anyone?) and are common place now.
What is interesting to note is that afaik no-one locally has been able to replicate the ram-air effect when dyno tuning a bike.
Mainly because the ram-air doesn't really make a significant difference until speeds of 190+km/h. And I think you'd have to dyno the bike in a wind tunnel to replicate that.
So the "push" you are describing won't really bear fruit until you reach naughty, go directly to jail, speeds.
Also worth noting is that motorcycle ram air systems are totally sealed. You put your hand on the front of the intake, give the bike a rev and the bugger tries to swallow your hand.
Cool trick to play on unsuspecting nubile young women as my personality tends to scare them away anyway.

Your thoughts on cooler (denser) air are spot on.
What I have tried to do (NA8C though) is decrease the length on the intake tract (and remove the helmholtz/resonance chamber), increase its diameter, and put a high flow air filter in.
I aslo have a cold air duct feeding to just forward of the radiator, which utilises the shape of the underneath of the bonnet to feed cool(er) air to the intake. It cannot be seen
in the below image but the opening is just forward of the Mr Enforcer engraving. This is fed from a duct on the mouth of the front bar.
It does work as after a good run, the radiator top surface is quite hot but the are where the duct feed is very cool to the touch.

[MX5CHIC]

The system I hope to come up with is basically a forced air intake, exactly what your grille and radiator do to cool your car, the air entering the grille is forced through all those small slots in the radiator whilst the car is in forward motion.
I will look at a method to utilise some of that grille area to capture air and force it up and through the existing hole behind the left headlamp on the NB8A, the trick is to scoop that air forward of, rather than beside the radiator and to capture air across as large an area as possible therefore increasing the pressure as the air is forced into a smaller space, there is plenty of room behind the bumper for ducting which makes things easier.

[Okibi]

Yeah I use to have a bit of metal in the corner of the "mouth" like a scoop on the NB forcing air in behind the passenger side of the bumper so it would escape through the hole under the headlight (I've sealed the vents in the wheel well).

In the NB8A you can dremel the headlight to make it easier for the air to use that hole (look at the difference between the NB8A and 8B headlight.

[MX5CHIC]

Now that's a good idea Okibi, sealing the vents would make the only escape through the hole and up to the filter - so many great minds on this forum! .... that would certainly cause a high air pressure and even without a "scoop" the air is still going to be far colder than under bonnet temps ...... must get to work on it

[randymx5]

Hey i can recall seeing a carbon fibre scoop that looks a bit like the wrx type. Sounds bad i know, but it is non offensive and sits just below the wiper , between the wiper and bonet. Would be great feeding a loche stewart air box i would have thought. Ill look for some pics and post them if im not beaten to it!!

[Steampunk]

Fast Freddy.... you've got your air filter connected to the top radiator hose?? Coooool!

Guys, putting vents and intakes in your bonnet may sound like a good idea, but ever thought of rain and debris that they collect? Take a look at the underside of bonnets of cars with scoops and vents. They are not JUST holes.

I've dríven a car with those Lach Steward fire-wall intakes and there is definite merit in it as the low/mid-range torque is MUCH better, but I am also in agreement that I do not want to butcher my car in such a fashion.

Zoom zoom has an interesting set-up for his version of a CAI that I've never seen anywhere else. Send him a PM.

[fastfreddygassit]

Fast Freddy.... you've got your air filter connected to the top radiator hose?? Coooool!

Andrew you goose!
To be perfectly frank, I expected more from you.
It is obvious that the "radiator hose" is actually the out feed pipe, from that large shiny intercooler, that feeds directly into the air filter.
Cooler thus denser air=more power (and smoke)

actually my name isn't frank either.....

back to normal programming...

[wun911]

We still want the forumla....

How many degrees cooler for how many kilowats?

[Rotary]

I experimented with a tube from the standard air box with the inlet coming from the front of the radiator, it worked in principle but I used expandable 2 1/2 inch flexible aluminium tube which I considered was losing any advantage by causing more restriction via it's length and bends, a much larger intake area and larger tube diameter would have worked much better. I ended up removing it when the car was dissasembled for it's respray.

I am no expert in engine performance but what I am hoping to acheive is to "push" as much cold air in to the air filter as possible rather than having the engine struggling to "suck air through a straw", hence I need to locate the best high pressure air location and catch as much air as possible. Does this principle seem sound in relation to engine performance or am I likely to cause more problems with the ECU etc?
I have been reading a great deal on this and other forums and tech sites and a lot of it sounds contradictory BUT; one thing I always notice when driving my car (and feel free to question me on this) is that in cold weather, my car seems far more responsive and smoother RE: dense cool air.

Your ideas are sound, and its good to see someone challenge the thinking in current designs, and rightfully so, as from a performance perspective there is much to be gained over most existing systems,

My CAI Design is like you are thinking, with the Pod in the enclosure where the fog light would sit in a NB8B(drivers side). Resulting in gains of around 8% according to the Gtech’s real world dyno.(Backed up by the WSID times)
But I can’t recommend this Mod as its not suitable for all possible road conditions, and is more a Race only Mod. Your most welcome to have a look at it and discus it either at the next event or another time (I’m 10mins from pyrmont)
Matt.

[Okibi]

"..NB8A, 14.9@148kph WSID" It's obviously working then, my last 1/4 mile was 16.2

[SuperMazdaKart]

something like this is the goer i reckon

[MX5CHIC]

Ok, love the ideas - here is the AutoExec System at around $400 UK Pounds




And next we have the Mania Cold Air Intake @ $250 AUD which claims "up to 12kw" power gain .....




I currently have K&N cold air intake and filter, I have the option of "boxing it in" which requires some difficulty and much time, or making up a system similar to the Mania CAI, I'd prefer the second option but need to find where to buy the outer "funnel" or housing that sits around a K&N Filter - I've done some searching but can only find the complete CAI Kits which would mean starting from scratch.
The idea of placing the filter behind the bumper is good but not practical for daily road use, so I may opt for building an aluminium housing for the filter and taking air from behind the firewall, this will take some work as I prefer a very professional finish.

Time to get some measurements underway ...

[grump]

i think that getting the cold air to the engine is only half the problem, and getting the hot air out from the engine bay is the other half

[Rotary]

"..NB8A, 14.9@148kph WSID" It's obviously working then, my last 1/4 mile was 16.2

That as well as a few other little mods not really supposed to be for every day use, like the 18 Deg ign timing, light oils, missing cat to name a few. but with extra care and the right precautions less risky when dríven occasionally,

The CAI definitely makes a nice difference, I would guess more around a 15.3-15.4 e.t. without it. And the 8% gain is across most of the rev range so very usefull.
I haven’t researched it any further to determine if it’s all Cold air or from improved flow, maybe a bit of both, and I can still see where further improvements can be made.

Although I am dying for more power, Im waiting till I learn how to drive properly on the track(1st time last month), and it is fun in a 5 anyway, whereas in other cars would be boring.

MX5CHIC, i think mania's looks better than most in terms of recieving fresh charge, but its length and position and therefore possible heat uptake is what i would want to know about. Not saying its bad, as i haven't tested it, but i would stick a temp gauge at its inlet and just before the TB, to make sure.

[MX5CHIC]

I guess it's all relative when it comes down to it, I work as a Consulting Engineer and much of my work is in the area of Air Conditioning so I take the priniples of heat load, air pressure & restrictions to airflow etc into account when looking at my air intake system on the MX-5 - force more air in at a lower temperature and produce higher efficiency, I agree that is over simpifying things but the basic principles remain the same.
My current K&N system and most such systems do improve total airflow by creating a smoother path and less restriction of airflow but technically speaking cannot really be described as "Cold Air Intake" Systems unless they have air being drawn from an area other than the very high temperatures under the bonnet.
Ambient and Radiant heat (via headers) under the bonnet will transfer a percentage of heat to the intake tube, but become more negligable as the total volume of air through the tube increases, meaning that the intake air from outside will act to a degree to cool the intake tube thus overcoming some of the heat transfer, materials used also have an affect on this heat transfer.
What it comes down to is that ambient temperature is always going to be considerably lower than under bonnet temps, lower intake temp equals denser air and thus better engine efficiency ............... we then add the factor of reducing further the restriction caused by the components of the intake system, this can be accomplished via a turbo, a supercharger or simply by pressurising the air via pushing air down the intake system with efficient positioning of the intake by placing it in a high air pressure position on the car as it moves forward - both cooler air and higher pressure (pushed) air can only add to the efficiency of a motor.
Efficiency does not simply equate to a power increase, as a gain in fuel savings and lower operating temps are positive outcomes as well.
It would be very interesting to see actual Dyno results in MX-5's taken with a standard setup, a (so called CAI) System and a true CAI system using air from other than under the bonnet ..... I will keep tuned into the Dyno results pages.