[BigShow]

Having now finally got my suspension to my liking and my engine producing good power, I'm left with the personal challenge of sorting out my inlet temps.

I've thought long and hard, stared for hours as the MCS cooling system and read more info on intercoolers and CAI's than its healthy for any one man to admit (it helps getting wifi on the beach) Now, I think (he says tentatively) I've got to the route of why so many of the CAI's out there seem to lose horsepower rather than gain it.

The MCS supercharger significantly heats the intake air as it compresses it to create boost. The higher boost pressure increases the air density, but the increased temperature of the air can largely offset this density gain. In this case, we’re talking about the affects of pressure and temperature in a confined space, the intake system. Consequently, it is desirable to cool the compressed air before it enters the engine. In most cases, especially where boost levels exceed 7 PSI, cooling the compressed air with an intercooler is common practice as it increases the air density more than any density losses that occur due to the accompanying pressure drop due to cooling or flow restrictions through an intercooler. Or to put it into layman’s terms, intercooling results in a net density increase for the air entering the cylinder.

It’s for this reason that Mini fitted the top mount I/C, however, when you start to spin the supercharger faster than the standard I/C has been designed to manage by using 15% & 17% pulleys the cooling effect of the I/C is drastically reduced. It is therefore accepted within the Mini performance community that upgrading the I/C when upgrading the pulley should be common practice if horsepower gains are sought.

The Missed Opportunity

So having established the benefits of bigger intercoolers the next logical step is to look in-depth at the cold air intake (CAI).

In general the paper filters that Mini designed the car to be used with are very good and it’s not easy to increase horsepower simply by replacing the filter. Replacement panel filters will not therefore increase the horsepower of the Mini over a standard paper filter that is new, however paper filters become blocked with dust more quickly than performance replacement panel filters due to their smaller surface area and hence they can cause the power output of a car to be reduced over time. A performance panel filter will also flow less efficiently over time but it will not reduce horsepower as much as the standard filter.

One of the main benefits of fitting an induction kit on the MCS is, in my opinion, the increased supercharger whine, however out and out horsepower may be being reduced by a common performance induction filter due to it sucking in hot air from the engine bay. For every 10C increase in intake air temps, air density is reduced by 3% and therefore horsepower is reduced by 3%. So while one of the many induction kits available for the Mini will make a better noise and make then engine bay look better, it may not increase peak horsepower if it is not properly shielded from the heat of the engine bay. This is the missed opportunity!

Why is it a missed opportunity on the MCS? It has been proven outside the Mini community that the effective heat shielding of a CAI can increase power by 6.8hp on a 150hp engine due to reducing inlet air temperatures by 14C.

Therefore I conclude that CAI’s, if not shielded from the heat of the engine, can potentially cause power loss by drawing in a hotter intake charge. So if you want to ensure your engine is providing its maximum horsepower potential you should probably move away from the ‘open’ style CAI’s that draw in this hot air.

But I’m not going to expect you to just ‘take my word for it’, instead, I’m going to show you how in depth testing has proved this theory right on another make of car and then when I get back to the UK I will prove it on my own car which uses the ‘open’ style Alta V2 CAI.

The Test

The following results were found using heat shields to enclose an aftermarket Pipercross air filter versus the standard air box:

Urban driving: max: + 6.8hp with heat shields - temps 14C lower with heat shields over standard air box.

Urban driving: avg + 5.84hp with heat shields - temps 12C lower with heat shields over standard air box.

Open road: avg + 4.38hp with heat shields - temps 9C lower with heat shields over standard air box.

These gains solely take into consideration the hp gains due to lower temps and not the hp gains that the induction filter may also bring, in reality the gains are probably larger due to the use of a freer flowing air filter.

Background - Reducing the temperature of the air entering the engine will increase the horsepower.

References - f150 forum, viper club, temp conversion calculator, zx11, banks power, tech line coatings

Most of these articles have temperature in Fahrenheit. (5/9 Celsius is 1 Fahrenheit) or just over half.

How the test was carried out - Each test was carried out in the same manner. The idle temperature was taken by running the engine up to operating temperature with the bonnet open. The bonnet was then closed and the temperature of the intake charge was taken after five minutes. To test the temperatures on the road a route was devised which took in Urban, A Road and Motorway driving. The temperature was monitored on the route to determine the trends in the temp changes, the max and minimum temps.

Equipment - A digital thermometer was used. A Pipercross performance air filter induction kit was used, rated to 300hp.

Aluminium 3inch ducting was used for the cold air feed. Medium aluminium sheet was used as the heat shield. The car the test was carried out on was a Nissan Primera (P11) GT SR20DE.

Standard air box - Idle Temp: +41C ambient. Driving Min Temp: +36C ambient. Max Temp: +44C ambient. These temps will be taken as a baseline. The temperatures for the test below will be + or - the standard air box temperatures.

Trends - Temps very consistent once on the move. Temps rose slowly when stationary.

Foam Induction Filter Alone (No heat shielding) - Idle Temp +7C over standard air box. Driving: Min Temp +4C over standard air box. Max Temp +10C over standard air box.

Trends - Temperature changed very quickly. Temps rose when stationary, fell sharply when on move. Higher intake temperatures than standard air box.

Foam Induction Filter With Heat Shield behind base of filter - Idle Temp +6C over standard air box. Driving Min Temp -4C under standard air box. Max Temp +3C over standard air box.

Trends - Temp changed more slowly than with no heat shield. Temps lower in general compared to no heat shield. Temperatures generally higher that standard air filter.

Enclosed Air Filter With Intake Solely From Cold Air Feed - Idle Temp +14C over standard air box. Driving: Min Temp +3C over standard air box. Max Temp -1C under standard air box.

Trends - Temps generally higher. The cold air feed was routed to receive air from the bottom of the car. The heat soak from the engine was making the feed incredibly hot and therefore heating the intake charge as it passed through it. I would not recommend having a cold air feed routed in any part of the main engine compartment, and to keep the feed as far away from the exhaust manifold and engine block as possible. Cold Air Intake not as effective as imagined.

Air Filter With Opened Enclosure With Heat Shields Completely Isolating Air Filter From Engine Bay And Exhaust Heat - Air Flow In Around Headlight and From Inner Wing - No Ducting Was Used. - Idle Temp -6C under standard air box. Driving: Min Temp -9C under standard air box. Max Temp -14C under standard air box.

Trends - Temps lower and steady. When the car was stopped at traffic lights the temperatures rose very slowly approx 1C every thirty seconds. Once on move temps dropped very quickly.

Conclusion - Heat Shields should be used with an induction kit to ensure the intake charge is not heated by the main engine bay. Cold Air Feeds should not be exposed to the main engine compartment.. If possible a feed should be taken from the wheel arch or from the head light and a shield should be located to completely isolate the filter from the heat of the engine and exhaust.

[brainycheddar]

I've got a Minimania CAI, and it came with a proper heatshield. After cutting out the back panel to suck air from just past the hood, it seems my main problem is heatsoak coming from the top-mounting of the intercooler. upon startup (according to my scangauge) my inlet air tempurature is not that much cooler than my water temperature with the hood closed when I check with the engine off on a warm engine. after the engine idles a little, with more air coming through, the inlet air temperatures(IATs) drop to about 94 deg. F. with the car driving, the IAT usually sits about 20deg. F about the outside air temperature. so a larger intercooler would probably be the next logical step to lower those IATs even further...

[MarkW]

to be honest i'm surprised you needed to research that

[Lucky Dave]

A lot of your findings are well documented.

But its the conclusion I have to question, your findings measure air intake temps not BHP and your numbers could mislead some.

Your ideas could work on a NA engine but the heating effect of the charger does not just add standard amount of degrees to the air as it passes, the cooler air will be warmed more than the warm air. You dont mention where in the system the air temp was measured?

Also dont forget the problems of feeding air to the engine from low to the ground, you only need to see how many BMW diesels were damaged in the recent floods! Yes air intake at the bottom of the bumper, wheel archs can be worse due to the forward spray.

Im more inclined to inspect your scoup as that would appear to be keeping your intercooler temps higher? Im running a close spec to yours and my intake temps are lower than yours?

Sorry to be picky but the testing does not tell us anything new or am I missing something?

[Lucky Dave]

No wonder yours is hot, your in SA.!!!

[roland2003]

Hi, yes shielding to ensure the coolest air entering the filter is very important, the GTT Cold Ram goes one stage further by using a twin skin design on the side adjacent to the the hot manifold. The 2 skins have a 5mm air gap between. This is very effective as we found out also on the GTT twin skin heatshield for the similar induction kit we did for the R5. In fact its so effective here that even with a turbo glowing orange at 1000deg C just half an inch away ,its still possible to put your hand on the side of the shield ......
2 skins ....small air gap= very effective heat screening . Now wheres my thermos flask I fancy a picnic

[Paul Webster]

Dave I think you have to be on the track the same day and then compare IAT's, Its very hard to compare data on different days / tracks / weather conditions and I presume course layout.

Like you I would rather concentrate my efforts on the scoop / IC / intake manifold cooling.

[captint]

why can't the air intake be outside the engine bay

[BigShow]

I probably should have been clearer. This research was born from the recent track day in which inlet temps were high. I realise that was mainly attributed to scoop or I/C issues but when I placed my hand on the foam filter after time on track it was very hot indicating that it wasn't making the most of the cold air.

My idea is to seal the Alta box sides first (as Roland does on his CAI) with a skin that keeps the heat out then measure temps. Then cover the top of the Alta box with the same material so its not reliant upon the bonnet insulation to keep heat out and measure temps. Then I plan to add a scoop on the pollen vent to ram air into the Alta box and measure and finally replace all the tubing into and out of the Alta box with heat resistant material.

These mods ensure there are two safe ways of getting cold air into the scoop, the OEM way and the pollen vent scoop way which will quell the worries that Dave quite rightly mentioned.

TBH honest if I wanted to chuck money at it I would do a custom GRS front mount and copy Rolands GTT300T scoop air intake idea to make sure that temps on track were as low as possible but I want to try this first.

These are only my thoughts by the way from what I've learnt, reading back what I've written makes it sound like open top CAI's are an issue which I'm sure they aren't but I'm hoping to fnd out the benefits (or otherwise) of having a CAI system that is completely closed rather than the system I have now.

Afterall... every little helps

[roland2003]

Heres a way of checking the SUPERCHARGER intake temp (as appossed to the charge air temp )....
Take the temp reading from the UPSTREAM MAP sensor.
This sensor is actually a 1 Bar (absolute) T map sensor though the thermistor temp reading part is not used. DAVE! ...... (note NOT the T Map sensor in the inlet manifold) .
Now if you take the temp off here you could take the pressure reading off it t aswell to calculate mass of air. As you know any pressure drop (from restrictive plastic plenum/filter/TB ) will reduce temp. TBH you should always take the air temp and pressure tegother to calculate air mass ...you want low temp AND low pressure loss.
If you want to check total pressure drop across the entire induction tract here is the only place to measure it. This is how we know the plastic plenum for example can be more restrictive than the stock filter.

[batou]

The JCW/JCW includes a different back plate which opens a huge hole venting into the cowl area... how about a huge mad max style intake duct coming up from the cowl to net more air? I'm actually serious... it wouldn't have to feed through the engine bay at all it's would just dump straight in through the cowl vent

[brainycheddar]

well,. I think that the JCW, and most other aftermarket CAIs try to utilize the air coming from the front of the car, as well as the air coming from the base of the windshield, both of which are high pressure areas because of the air building up in these areas as it tries to go around the car (more technically speaking, as the car tries to go through the air). A hood scoop could get plenty of fresh air to the CAI, but I think it acts kind of like increasing the size of the plenum, not to mention the increased the amount of drag that the car is exposed to.

so is a possible fraction of a horsepower worth all the extra drag?

I'm not a fluid dynamicist, but I figure at 60mph, a car is mostly pushing against air, decreasing drag would be worth more than +0.1 hp

[alski]

sorry guys but as a member of the flat earth society can i point out that all this windscreen stuff appears counter intuitive to me
volume of air from front of car a] , meeting volume of air b] from opposite direction could fight against each other ?

their might be a magic velocity when volume and speed of a = volume and speed of b] so the pressure increase in the air box is good, and highest at the intake point
so this is the sweet spot?

but at low speeds their will be no pressure wave at the base of windscreen, the air will flow around and may even cause a venturi effect and suck air out of the box causing lower pressure

happy to be flamed and called a luddite, as all based on 20yr old recollection of a physics lesson which never had my full attention at the time anyway

ps.not even seen a jcw intake but could this be reason behind the famous flap?

pps. can we have mini "HOW" like in the 1970's i would watch it

[MINIMANIAUK]

Brainychedder has it pretty much summed up
The gains with any CAI are few ,but they exist.
the charger is consuming 300 cubic feet of air (if you can picture this) every 60 seconds at the higher rpms ,so it takes a lot of underbonnet heat to warm this volume of air at ambient temp .
whilst the car is moving heat is also being pulled out from under the engine bay.
The JCW flap was done more to reduce the charger noise and engine warm up ,than any performance reason,not everyone likes the extra noise generated!!! -thus it created an expensive oddity
heatshields work but low restriction CAI is the best design .
It is also beneficial to allow a small portion of underbonnet air to aid faster warm up of the engine in the winter months( If you look at the minimania CAI it has exactly this)
With the car stationary you dont need lots of cold air ,boost is low,engine load low,and the stagnant heat very quickly drops off when driving forward .
the intercooler is a better way to reduce temps at the intake or not produce the heat in the first place!!

[bahambart]

Quote: Originally Posted by BigShow300 (original)

It is therefore accepted within the Mini performance community that upgrading the I/C when upgrading the pulley should be common practice if horsepower gains are sought.

I don't think this is the case at all. If anything overtime it has been demonstrated that the stock IC is quiet efficient and after martket ICs either give you -

a) more thermal efficiency typically at a cost of pressure drop.
b) less pressure drop but typically at a cost of thermal efficiency.

Now depending on your application, you might want one attribute over the other but I have yet to see an after market IC that beats out the stock unit at both categories. And when it comes to making horsepower, the more generally acepted view is to spend your dollars elsewhere than replacing your IC. The last thing to replace is the IC when building out your engine.

[GT4 Baz]

I too think that the TMIC is the biggest problem that you guys have.

Having just replaced my WAI TMIC with a FMIC, I have seen a gramatic reduction in charge temps even running higher boost levels than before.

Since adding and FMIC seems very difficult with the SC outlet and TB inlet, maybe a water spray system for th TMIC would be a better solution?

Browser Warning

There is a series of articles with measurements on the above link which are well worth reading. The other option is to try and get a water spray tank from an impreza and plumb that in.

Or something like this : http://memimage.cardomain.net/member.../720526_55.jpg

The other option is to run water injection after the TMIC, this will greatly reduce inlet temps but obviously is a finite solution, the water will run out!

I think that a scoop at the windscreen for the CAI will not work particulary well either, air at the base of the windscreen is trying to escape the engine bay at high speed, just at the point that you are trying to ram more in!

[brainycheddar]

that's an interesting point you bring up about air exiting the engine, I'll have to get some 2" pieces of yarn and some masking tape and try and determine the path of the air around the car at this gap.

My feeling is that the air will exit out the back, as after a long country road, my hood is usually warmer than those holes around the windshield