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From dual oil cooler to single

Old 11-10-04, 04:45 AM
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From dual oil cooler to single

Hy,

My 94' FD has dual oil coolers (OEM) but I have found several big oil cooler kits for only the driver side.
I would like to do this mod so I can usethe passengers side bumper hole as an air duct for the intake.

What size oil cooler would be sufficient to support a +-400HP 13b-rew engine (future, now stock). I'm looking into Mocal coolers.

The kits available have 25rows?

Thanks
Neal
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Old 11-10-04, 09:01 AM
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RotaryExtreme has up to a 34 row kit.
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Old 11-10-04, 09:28 AM
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is it really necessary to go that big?I really want it to fit the drivers side oil cooler place (custom brackets are no prob)

Can I somehow calculated what I need?
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Old 11-10-04, 12:27 PM
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I'm not an automotive engineer - can't help you with finding the formulae for oil cooler size. However, there is more involved than just the size of the cooler - airflow through the cooler is critical. A larger cooler won't do much good if it's only getting air from the stock opening.
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Old 11-10-04, 12:54 PM
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This is a very interesting question.

Do you have an R2?

The non-R1/R2 models came with one oil cooler only.

Why would the Mazda engineers use dual oil coolers in R1 rather than one large one? Is it because, there is better cooling of the oil with dual oil coolers placed in series since the oil would be cooled by the first oil cooler and the cooled further by the second.
Is it possible to obtain the same degree of cooling with one larger oil cooler?
Why didn't Mazda use one larger cooler instead of 2 which would inherently have more failure points?
I don't know the answers to these questions but it does make me wonder about the possible answers.
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Old 11-10-04, 02:07 PM
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Lots of 500+ hp V8s do fine with a single oil cooler - it's more an issue of total cooling capacity (size & design of cooler + airflow) than number of coolers. I don't believe (and as a non-engineer, this is belief - not knowledge) that there is a significant difference in the performance of dual oil coolers in parallel vs. sequential. I suspect the reason Mazda did dual oil coolers was simply finding a decent place to put them that didn't ruin the lines of the car or require some extensive difference between the base/touring and R models.
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Old 11-10-04, 06:15 PM
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One oil cooler should work just as well, assuming it's getting sufficient airflow.

They might have used dual oil coolers for a couple different reasons, including a more uniform weight distribution (even left/right split), modularity for easy expansion (add a 2nd one for the R1, cut it for the base/touring), and the fact that each oil cooler has a dedicated exit vent (the ones in the fender, behind the front wheel), which makes it easier to get sufficient airflow.

Advantages of single oil cooler would be that it's slightly less weight than duals (less materials in one container vs. two, also removal of associated lines), and you could use the free space of the 2nd unit for something else. Plus you could sell the used R1 oil cooler, I believe people still buy them.

-s-

Looks like this has been discussed before: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/r1-r2-2nd-oil-cooler-vs-single-larger-68250/
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Old 11-10-04, 06:34 PM
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My dcar is a European R1/Touring with stock dual oil coolers. I want to put a bigger one on the drivers side to use the passengers side for an air duct to a custom airbox I will be building in a few weeks.

I"ll have the Wise Sports front on the car when it's done

Don't they make small fans like radiator fans for use on oil coolers for extra air flow on hot days or serious track work?
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Old 11-16-04, 05:40 PM
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yes I believe SPAL has a fan for your application.

Additionally it is unfair to compare the oil cooling needs of a 500hp v8 to that of a 400 hp rotary. This is because oil facilitates a high percentage of the cooling in a rotary where it does not do so to the same degree in the v8.

Personally I'd keep dual oil coolers. Reason being that ducting a cold air box has little or no benefit on a turbo car. I would simply build better heat shileding for my turbo or get the turbo inlet ducts ceramic coated. I'd never risk sacrificing oil cooling for ~3 hp.
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Old 11-17-04, 09:24 AM
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I think the reason Mazda (and some aftermarket kit) are dual coolers is because the inlet openings in the bumper are small... I believe the CWR duals were 18-row each, and the front surface is still probably 40% larger than the opening. The 34-row RE is roughly the same size as the two 18's (2 row difference), but in order for it to be as effective as the two, you'd need to have an opening on that side that's twice as big as stock (like on the '99, GTC, or other aftermarket bumpers), and have it well ducted.

FWIW, even with the dual CWR's, folks on track in hot weather (like here in VA) see MANAGEABLE oil temps... not exactly super-cool ones, so to some extent, I don't think you've reached the overkill stage yet. Its hard to get enough cooling of anything in these cars.
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Old 11-17-04, 12:51 PM
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how about all the extra ducting for dual coolers? it's taking the oil quite a distance to even getting cooled down.

Not to mention the difficulties to get the old oil out when you're changing engine oil.

Wouldn't a shorter circuit and bigger surface compensate for something?(reading single big cooler kit)
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Old 06-20-05, 03:00 PM
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this is old but kinda interesting...I'm thinking of upgrading my single stock oil cooler to a larger cooler...and a larger trans. cooler for the TH350...any suggestions???

(I'm thinking mazda may have used 2 coolers b/c they used/needed the second cooler as a tranny cooler on the auto models)
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Old 06-21-05, 12:36 AM
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I use two stock FC coolers in my road race FC, in series, and they work very well, ~190 after ~1/2 hour at ~80 ambient, and ~350rwhp. I am moving up to ~450rwhp, we shall see how they do. First set up was a oil & water cooled turbo, new set-up is oil cooled only
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Old 06-21-05, 06:00 PM
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doesnt the size of the opening needed have to do with the pressure drop across the cooler? its certainly not 1:1. the stock opening might flow enough air to support a larger cooler than the stock one. the question is how large can you go before you stop seeing any more gains.
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Old 06-21-05, 08:57 PM
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I find it EXTREMELY hard to believe that a larger single cooler, especially with the stock bumper, will cool better than the stock dual setup. I would put money down that an aftermarket dual setup of 19-rows or larger will out cool any single cooler.
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Old 06-21-05, 10:11 PM
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airflow is important but so is the temperature of the incoming air as well as it's orientation to the cooler. Also, different positions of the cooler can help get better convective/radiative heat transfer.... Really well prepared racecars take advantage of this. you can also play with the aero a bit using the radiators/heat exchangers
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Old 06-21-05, 11:19 PM
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I agree with Carl............The two stock coolers on the FD are perfect with dedicated ducting. Use braided line and forget about it. Petit racing used the two stockers on their Daytona 24hr car with out issue. Use the turn signal opening for the intake. Oil runs 190 after all day use.
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Old 06-22-05, 12:24 AM
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A water cooled turbo is a fine heat exchanger My oil and water temps are withing 5* of each other(190). I have a very large FMIC, then about 6" opf air space within which my CAI resides, then two oil coolers mounted flush against my radiator. Each oil cooler is 22x5x2, and are fed in series with -12 lines I made. Nothing fancy, some home made brackets, and an aluminum air box to direct the air
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Old 06-22-05, 01:19 AM
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Originally Posted by SHPNOUT
...The two stock coolers on the FD are perfect with dedicated ducting....
NOT.

Why do you think there are aftermarket oil cooler kits out there for the FD? Any track junkie can tell you of 250F+ oil temps on a warm track day with the stock dual coolers...you should have seen mine with just the stock single cooler. Truly scary (260F+ on a 50F day!).
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Old 06-22-05, 01:41 AM
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Rynberg, SHPNOUT speaks from experience as well. remember, he said with dedicated ducting. I dropped my oil temps over 40 degrees by cutting my bumper(FC), and cantilevering the rear of my hood with the two coolers. SHPNOUT has a Petit car, and has been running it at T'Hill IIRC. Carl
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Old 06-22-05, 06:31 AM
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Originally Posted by Carl Byck
Rynberg, SHPNOUT speaks from experience as well. remember, he said with dedicated ducting.
The FD come with oil cooler ducting from the factory -- it may not be perfect but it's pretty decent. I don't just speak from my personal experience but every other tracking FD owner I've ever talked to IRL or on this forum.

Just wondering what it is about SHPOUT's setup that is different, because more efficient ducting does not account for a 60-67F temp difference.
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Old 06-22-05, 10:14 AM
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Rynberg..........Aftermarket items aren't always the best way to go.........It is amazing how people feel the need to spend the money when smart engineering can solve a lot of issues for little cash. I know becuase I have made the mistake many times. Just because it's for sale doesn't mean it's good.

Direct air flow.......from bumper inlet to hose to cooler. Nothing behind the cooler. ie no fender liners.

Other issues at play for oil temps.......Water temp......I run a huge verticle mount Ron davis radiator, have a vented hood etc. Intake temps, I run a huge front mount intercooler. It is all part of the equation when it comes to keeping temps down.

Only one stock oil cooler on a track FD is NOT a good thing. Get a bigger one or add the second stocker. My first FD was an R1 and tracked hard with no improvments over stock ducting and I had no issues.

Cheers
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Old 06-22-05, 11:01 AM
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maintaining your equipment is a big issues as well. If it's got crap built up on the walls, ( there is a term for this but i am blanking) then it's efficiency will drop off greatly.
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