Are you proposing there is more pressure from the cowl induction in comparison to the air entering directly through the grill exiting directly out the rear of the radiator? Honestly, the removal of the boxes should make a difference. I should really stop yapping and try to get some solid proof. The best I can say right now is that coming down the mountain my temp gauge will now drop completely to the bottom - it will literally drop down to temps below the car's idle,

To better illustrate:
I can see positive pressure building up in the engine bay via cowl induction (holding the heat in) if hood tilt were performed here ->


From another thread:

I personally have had my intake tubing heat wrapped for quite some time, with the trays removed, with the hood tilt/weather stripping removed (in combination with some other cooling mods) and can say heat soak/laggy throttle response seems much much less apparent than a stock car! Like I said, IMO for this mod to properly function you must be pushing air in the front of the bay (via radiators/fans) in order for it to exit the back of the bay (vent). Lateral engine bay air circulation gets a from me.

Geez, thats a lot of talk with little hard evidence to back myself up!

 

I agree removing the front boxes should help.

I am proposing that the air coming in from the cowl increases the pressure in the engine bay reducing the differential between the front of the radiator and the back of it at highway speeds reducing overall flow through the radiator and total heat transfer as a result. That is based on the fact that Justjim saw air entering the engine bay at high speed. That means that air is moving from high pressure to low pressure in an attempt to equalize. So the pressure inside the engine bay will be increased vs. sealed at highway speed.

Again I know this mod. works for reducing temps around town and stop and go driving and recommend it for people that have temp. problems in traffic. I don't think it works for track driving and high speed temps. I've done both and have an analog temp gauge that tells me the low speed driving temps are higher but high speed temps are lower. In my neck of the woods it's not really an issue around town so I am choosing to revert back.

 

Ah, some thoughtful input! Just seemed many hadn't understood the concept of allowing the air to actually pass through.

 

If the air in the engine bay became pressurized, or more pressurized than normal via the cowl induction, wouldn't the evacuation of air from the engine bay be assisted since it will be exiting a higher pressure system into a lower pressure system? Or is the argument that the pressurized engine bay will prevent air from flowing IN to the engine bay effectively? But wouldn't the added air flowing in from the vent be what makes up the difference? Wouldn't more net air than before have to be entering the engine bay for it to become pressurized?

 

The idea is we have a liquid cooled engine so we want to get as much air as possible to flow through the radiator to remove heat from the coolant which in turn removes heat from the engine which keeps us happy and revving.

To do this we want the air in the engine bay to be as low pressure as possible. this will allow more air to flow in to the engine bay. Air is a fluid and will move from high pressure to low pressure so the lower pressure the engine bay the more air will want to move in to it. We only want it to flow in through the radiator. Anything else is not helping to cool our engine. So we only want openings in our engine bay,other than the radiator opening, that are going to help evacuate air. At low speeds and in traffic most of the airflow is driven by the fans sucking the air in through the radiator trying to pressurize our engine bay. So more openings will allow more air to move out of the engine bay and keep the pressure differential as large as possible across the fans. So the hood vent works really well since it's a relatively large opening.

At high speeds a high pressure area builds up in the area in front of the windshield. If the pressure is higher in front of the windshield than in the engine bay air will move in to the engine bay. If it's higher in the engine bay then air will continue to move out of the engine bay up to the windshield. If air is moving in to the engine bay from the windshield then it is increasing the pressure inside the engine bay causing a decrease in flow across the radiator. As justjim demonstrated this starts to happen at highway speeds. That makes sense since the air pressure builds up as speed increases.

So again around town and in traffic this is a great mod. On the track not so much.

 

Interesting stuff.

 

There is an issue with this seal as you say - its MEANT to stop any engine bay fumes or heat getting into your ventilation system. The other side effect will become obvious during heavy rain / cold weather - the heat from the engine will cause fogging or condensation on the outside of the screen - making visibility an issue...

This I learned by default when a car I had once was delivered with the seal missing in the first place.

 

OFF Topic Question...

But how do you stop the Ventilation on Fresh Outside Air from being Heated...
I like to have cold fresh air into my cabin, but, it always is heated...what am I doing wrong.

Adjusting the temp dial does nothing, my manual is very vague on this one too.

Thanks
Ash

 

sounds like a good idea and if mm says it works i gotta try it. will do this today or tomorow

 

I'll chime in since I've been running this for over a year. My only cooling mod is the Mazsport fan kit - great investment. With the rubber removed my fans came on constantly not to mention that the vented cabin air was warm as hades. Replaced the rubber and my unscientific observations and conclusion is that: a) my mileage is up by 2-3 mpg over the past 3 tanks and b) fans don't come on quite even half as much.

I've got no gauges so I can't give you "hard" data. I've got nothing to gain, nothing to lose, just my observations.

 

do you mean how do you stop it if you remove the seal ?
You can't - only way is to recirc the air inside the cabin .
I gave up on this mod altogether recently - sick of smelling engine fumes .

 

Sorry, should of made it clearer.. not talking about Vent Mod..

If it is 14C outside and you like cool (cold) fresh air in cab, it appears the lowest it will go down to is 18C on my Dash Temp Dial, so the air is being coolant heated by the cars heater to 18C, you can't actually turn heat off...and get the 14C fresh air through vents?....is this any clearer...

The actual Hood Vent MOD, I agree, don't like it at all.

 

just because it says 18c does not mean it is heating the air ...

 

Not so sure, when I stick my hand out the window it is much colder than out the vents, so the air must be heated?...how does it get warm?

I liked my old car, when you slid the HOT/COLD all the way to the left the heater tap was OFF..no coolant, no warm or hot air..on FRESH air in cabin.

 

Could be just picking up heat from the ducts . I really do doubt that any heat is being added by engine coolant .

 

At night time???..

 

If you really do suspect there is an issue there - jam a thermometer in the duct and compare it with your outside air thermometer . Taake it to the dealer and complain if it is any more than a couple of degrees higher (after allowing sufficient time).

 

Does your dial do anything? I know you have an 09 which is different but the rest of us have failing HVAC controls. Maybe the following test works for you...
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-no-heat-repair-heater-control-158200/

 

ASH8 have you every found a solution to this?

 

^ yes !!!

sorry to respond that late...:
Ash, if i may be of some assistance:

you actually have to turn the A/C on, reduce the shown A/C temp for a while and then shut down the A/C.

then the fresh air that comes in the cabin will be equivalent to the ambient air !!


well, if this helps you, then i might have somewhat redeemed you (0.00001%) for all your posts that have helped the Greek Community !!!

 

^
Yes this will do the job but only for a limited amount of time. After that interval the air will be heated again. So this is a temp solution.

Now about redemption for this post I would say it is not the case. You need to post some more helpful posts. [Άσε τα κατσίκια και τους γάμους και κάνε καμία βόλτα με το 8αρι . This means keep the good work )))) ]

 

IF you have an Auto-Climate type HVAC system, at any stage the temperature can not be lowered lower than 18c (64F) according to dash temp number.
Without the use of Air Con...when it is 10 degrees or less outside!..

Example (Winter time)
So if it is night time say and you want FRESH air ONLY through your dash vents and it is say 10 degrees (C) outside (outside dash gauge tells me so) the Fresh air WILL be heated automatically to the min of 18c (64F)...which to me is BS, I don't want my fresh air heated at all..sometimes.

So STILL the only way to prevent fresh air being heated (by engine coolant) through dash vents in winter time is not to have fresh air IN Cabin ON!

Frankly Mazda can stick the AUTO Climate Air where the sun don't shine, it is crap...
Thank god Mazda Australia's penny pinching prevented it in my new MX-5...I am in control.

 

Why, thank you for your kind words.

 

Has anyone tried to open up the vents behind front wheels since they are connected to the engine bay? Just to get lower water temps. I have temp issues
track days.( 110-113C ). Oiltemps 110-115C. Autometer gauges in ashtray panel. AC cooler still in place. 2004 RX8 with new shortblock 2010. Since 2006 a DNA supercharger 285-295 RWHP, Mazsport fan kit, Mazsport waterpump, Mazmart 74C thermostat, Ron Davis Radiator, Red Line Water wetter, max opened front, Scoop on the bonnet, boxed in airfilter around the Procharger (earlier KN filter, now a large ITG since one week back, witch gives higher output than KN. Planning to take the AC cooler out if I don't get lower watertemps. Just started to make hood vents too. The liner is taken away also. Like MM said, the temp goes down quicker with Ron D rad. than OEM and Koyo. Have tried last year to take the rubber from rear of hood but couldn't see any improvements at that time. I will try tomorrow to lift the rear 12-15mm