DIY: Improve OIL Cooler Air Flow Up to 10-15%
 

As we know the Engines OIL Cooler's are located under your Headlights, the principal of cooling your oil is identical to your cars Radiator which cools your engines coolant, your radiator has electric fans to assist in air flow.

Your oil coolers rely on natural air flow from your cars movement and they have No electric fan assistance.

So, air goes through the front to behind the oil coolers and is then extracted through a bank of 10 tiny slits in your front fender Splash Shield wheel arch area.

To improve the air flow in my RX-8 I have done a DIY that requires the removing of the LH and RH small splash shields and an easy mod.

IMO I have improved air flow between 10 and 15%, which has to help.

"C Ya L8r" Confirms a 15-22 Degree Temp Drop at 30 MPH!

So what do you do.

1. I remove the front wheels to make it easier, BUT, you do not have to.

2. Remove the 10 or so black plastic screw nut clips with a small Phillips head screwdriver.

3. Remove the 3 Threaded steel screw nuts near/under the front lower bumper (NOT the ones what hold on the small black plastic wind deflector that looks like a ruler on it's edge).

4. The black plastic guard will now easily come apart from the main one , the removed shield is now the part you will work on.

5. Use a blade saw and carefully remove the 3 vent partitions (in the two top vent slits, see the first pic) to lengthen the size so you now only have ONE middle partition vent joiner in each, so it will now look
like the bottom two vents.

6. Get a 9 mm drill bit or larger and drill holes at the area where there is no vent at the top slit. Use your blade saw and open up between the drilled holes at each end of your new vent slit.

7. Use a rasp file to smooth, straighten and correct all the new openings to match the original ones.

8. Wash off the Black plastic bits.

9. That is all, replace the shield in the reverse order when you removed it.

This is a VERY easy mod....

Note: I DO NOT RECOMMEND THAT YOU ENLARGE THE VENTS ANY BIGGER OR WIDER AS YOU ARE THEN EXPOSING YOUR OIL COOLERS TO TOO MUCH ROAD WATER SPRAY/STONE DAMAGE/WEATHER.

First pic is of the LH Front ORIGINAL OIL COOLER SHIELD...NOT MODIFIED

Second Pic is the RH Front MODIFIED Oil Cooler Shield. THIS IS THE FINISHED SHIELD AFTER YOUR MOD.

good diy ASH . did this myself a few months back

Good, Has to be worth the effort...:)

Oil Cooler Hose Joint Lubrication.
 

WHILE you are at this MOD, I highly recommend that you lubricate your Oil Cooler Hose METAL Fittings with a WD40 Type lubricant...

WHY you ask?....

In England there have been many that have corroded and required replacement....

They are exposed to water, Mazda have changed them in later models, however even my Series II has a slight amount of corrosion forming.

PLEASE make sure you DON'T directly spray WD40 or any sealant Directly onto the oil coolers themselves as over time the oil film will attract dust and dirt and COULD block fins and restrict air flow.

Get a small rag and wipe WD40 around the fittings.

Ash

Today I took my 8 out on a long trip (55 minutes), it is the first time since I did this Mod to the Black Air vents I have actually driven my car...

( I have been doing other work on my car, so it has been grounded for the week.)

Anyway, when I got home I checked the outside (front) of the Oil Coolers and they were noticeably Cooler to Touch, not as Heat Soaked, SERIOUSLY I am Not imagining this.

I can only conclude that the 15% Opening Up of the Extractor Vents has helped in the process of cooling the Engines Oil.

So this MYTH is not BUSTED....IMO It Works and is well worth the time it takes.

Ash

interesting mod.

Yea I think the fact that it would work is a relatively basic principal, improve exhaust efficiency (in this case the heated air as it comes out of the cooler) and you will see lower temps, it also allows you to upsize your oil coolers since improved exhaust flow combined with increased intake flow (the speed and ability of the air to contact the whole core and flow through easily) will mean lower temps, the exhaust should always be bigger then the intake to improve efficiency of the core.

Believe it or not if you were to create an actual duct, sheetmetal being easiest, that was large, and smooth leading to the wheel well aiming it downward (so the air passing under the car at speed is in the same direction, causing somewhat of a vacuum and sucking hot air out quickly) you'd see improved results on top of what you've experienced so far.

Also i 100% agree on spraying some lube on all the oil cooler line fittings, they rust horribly, are relatively expensive, and suck to completely replace.

kevin.

Very interesting DIY. We got the Jersey Techie approving. I think I'll consider!

Hi Kevin,

Yes, I actually thought of doing that one too, opening up the entire area, then placing a created duct over the hole behind the oil coolers but when I looked at it there is not a lot of room to do it without compromising the clearance between a manufactured ADD ON Duct and the outside diameter of the Tire.

So my DIY was the next best (albeit only slightly) to maintain the original set up.

Some heat actually does (hot air rises) move up and over the wheel well splash guards and out of the Fender/Turn Indicator Lamp Vent on the 09's, the "honeycomb" vent hole is about the size of a large egg.

Ash

both my oil cooler line fittings has rust on them all over and I've seen some "minor" chipping ... Do u think I can get it warranty covered ? Since I can sense a leak coming real soon (Just hope that when it happens Im not in the middle of nowhere :()

Great DIY, Simple and easy to do :)

Warranty won't cover rust, only an actual leak. The rust wont make it leak as long as it's not disturbed generally, the type of seal is pretty good and the sealing surface doesn't really rust. Generally the rust makes it so that when you go to seperate them you cant with disfiguring or breaking them.

the only 2 sets ive seen start leaking actually werent rusts too bad and leaked from where the hose enters the back of the fitting rather then the connection point.

It's weird because the lines are almost identical to the FD rx7 lines yet the FD's don't really rust lol.

kevin.

maybe because they changed the material on the line to cut cost ??

they have a recall in Canada for these oil cooler lines. too bad not for the US :)

probably considering the FD was a high-end-ish car aimed at a different market then the rx8 when it was released.

yea canada gets special consideration on lots of cars, cx-9s have axle clicking problems from the grease in the cv boots gelling up in canadian weather.

To make you feel somewhat safer i had to do a motor on one rx8 and his fittings looked like one piece of giant rust, i was able to get the c-clip out and the lines actually popped right apart without much force, i was amazed, cleaned up the outside of the fittings as good as i could and spray this rust eating/converting paint type stuff we have...think its a rust-o-leum product.

kevin.

I should clean the rust and put some stuff on so it wont rust again. Maybe at next oil change (did mine last week for all fluids, brake, engine, tranny, rear diff)

thx :)

I'll try to find the product, but im pretty sure it's rustoleum, it somehow chemically reacts with rust to turn it into something else, i dont fully understand it but hopefully i can find a link, if so ill post it here later

kevin.

Autoexe has commercialized this idea, but the openning may be too big in terms of rust problems ...

https://www.rx8club.com/showthread.p...xe#post2951742

Interesting...Could expose oil cooler lines to too much water and oil cooler damage from stones/rocks thrown up by Tires.
See rusted lines pics below.

yea, that's definitely a worth while mod there.

Personally the middle piece of plastic going across the middle should be at a greater angle to push the air down to where the tire meets the road, it would create more of a suction effect, the way its angled now seems to aim it at the middle of the tire, too turbulent, non-smooth flow is the same as a physical restriction. Altho its probably not noticeable since the increased size of the holes alone is probably a great improvement.

kevin.

ASH8 did you remove the rubber things in front of the oil coolers? They look like they are blocking from of the fins and if you look at track set ups they are right up front and flush to the bumper.
Thanks!

Don't forget I have the Series II (09)...

So on the "outer" Front of the car all we have is the larger "Exposed" Intake with that black plastic and Chrome molded one piece insert...I cant see any rubber rings there and no I had no need to remove anything from the outside.

Only the inner thin black plastic splash shield that is vented (see pics in first post).

Just had a look, there are no obstacles or "rubber" anything in the front of the oil cooler, just a horizontal plastic FIN in the middle, then there is a large 2 inch or more gap between the molded front finisher and the oil cooler....this is from the front of the car.

Behind the Oil cooler (see pic) after you remove the vented splash shield is just the black vertical slotted steel support bracket and the two oil cooler hoses.

So, I don't know the set up for S1 RX-8's unless I look it up in my parts files.

The inner vented splash shields that I suggest you modify are of the same design for both series RX-8's

Rusted RX-8 Oil Cooler Fittings, if left without rectification will leak engine oil...everywhere..

I was wondering this myself. I had my car apart the other day and the rubber was holding leaves and debris in there which can't be good for the oil cooler.

Bump....for you guys "UP There", you are coming into summer, good time to act and help your oil temps.

Anybody done a before and after oil temp gauge reading with this mod?

Mine look something like that.

hmm ... I need to buy some rust removal stuff before it eats my lines for breakfast :)

More interesting to me is that my lines are a zinc/brass color and not the silver that the pics above indicate.
They are completely corrosion-free, even after spending their first two years submerged in the wet, salty roads of Maryland.


About to do that.
It is over 100°F here, so it should be a good test.

when was the last time you replaced them ? or is it still the original one ?

cuz I think Mazda made changes to the lines ... same as the Canada ones now. maybe thats why ?

Never replaced them. They are the original '04 lines that came with the car.

hmm ...

so does that mean they went "cheap" on the 05s, the salt ate the "cheap" lines alive and they have to issue a recall(for Canada at least) and replace them all again ?

oh well, I know my lines has rust all over them :(

Move to California, my lines are spotless!

If not, just get the rust off and put a coating on.

Just did this mod today. I went for a short 4-5mile drive and recored the temps. I then did the same drive after the mod same speeds and temp 30 mph and 71 deg. The results wrere as follows using a IR thermometer on the outside of the cooler.
Before: DS-169 PS-155
After : DS-147 PS-140
15-22 deg drop in cooler temp is not bad for free. :)

C Ya L8r - That's good to know - thanks! Anybody have any problems with road debris hitting the coolers, etc after doing this mod? Just wondering why Mazda didn't have the openings bigger in the first place.

Jeff - any word on your "move where the food is - nothing grows here" desert test? :)

Thanks for doing the research on this!

Great to see mate, and thanks for posting actual temp results!!

I knew my guesstimation was about right, and I was not imagining things..

Yes, even for this slight reduction in temps it has to be worth it.

I can not though agree on the other mod which virtually exposes the oil cooler by 85%..can't be good for rocks, stones and road/wheel water and mud.

Ash

wow nice results from cyal8r, was waiting to see some hard data, anywhere near 20deg reduction in temp is AWESOME. your engine will be happy.

MazdaManiac - all the lines i normally run into are brass-ish but they seem to have a coating on them cause it doesnt look like any immediately recognizable metal. I'll start looking to see if i can find a pattern.

kevin.

Nope . There is no more chance of debris than before the mod as the holes are at an inverse angle to the direction of said debris .

As to why Mazda didn't do it - they probably just didn't think it was necessary ....

Now we need someone to measure oil temps before and after. My test proves tihis mod mkes the coolers more efficent. But thats not to say overall oil temps will drop 15-20. Also 30mph is pretty slow but I wanted a route where I wouldn't have traffic variables.

personally id imagine higher speeds will show a decent gain as well, air flow undisrupted of the "exhaust" air will definitely get more cold fresh air thru the cooler faster.

the fact it did anything at slow speeds is pretty good considering such a lack of air velocity.

as for why mazda didnt do it... probably so animals couldnt hop in.

kevin.

:lol:
Yeah, like little pussy cats, snakes, lizards, small crocodiles, baby giraffes..
Mazda has to cater for ALL nations and continents you know...:uhh:

lol, but seriously im sure it had some kinda link to not wanting stuff to get in easily...maybe to prevent people being able to pop the hood by grabbing the cable or something(if you pull hard enough it breaks the plastic clip piece and pops the hood up)?

kevin.

The strange thing is that there is a reacll in Canada for the oil cooler line corrosion...and one of the fixes was putting in fender liners without any cooling holes....I said NO THANKS....and left my stock ones with the bis assed holes I cut in them :)

Yup

Cool mod!! Was wondering if any of you knew the actual part number for those OEM splash shields. A curb reached out and grab one of mine the other day and I need to replace it, and plan on doing this mod while I have the wheels off anyways. Searching for "front wheel well inner vented splash guards" (or any combination of those words) doesnt seem to help. Or I just am using the wrong part names. Thanks in advance

I guess you are sorted "Scarslett...late reply.

Anyone else done this mod recently??...
I am just interested to know ...being your Hot Summer is a happening now!!

wow thats a pretty cool diy mod, wish i would of known of this when i was putting on my new rotors, too bad they dont make small fans we could just put behind the oil coolers, that would be bad ass:cool:

I did it, but won't be testing the temps. It was worth it to see the oil cooler lines. The drivers side had some rust, but the passenger side was clean. I'm going to buy some spray grease from Amsoil and coat those and a few other areas under the car. Once before and after winter should help with long term corrosion.

i was just thinking if you cut out most of the backing and if u put in some wire mesh to cover the hole that should help with keeping road debris out of the coolers, wouldnt that work and alow alot more air flow

Yes, probably OK for Summer, but I would be concerned during Winter or wet roads, too much water or snow or mud over your oil coolers would not be good, then there are your horns and some electrics. I guess you could insulate or waterproof spray these would help.

But hey, I have been thinking perhaps a quick replacement type plastic shield, one Open mesh type for Summer and the original slit vents for Winter?

Subscribed. Never new about this. Probably a winter project while its setting in the garage.

nice, i will do this this weekend :)

I'll have to do this soon.
If I do this in the next few weeks, I'll make sure to monitor the actual oil temperature and post my findings.