Looking for feedback on radiator ducting

In reply to infernosg :

You need to post more pictures of that SA.  Spark Yellow?

In reply to Pete. (l33t FS) :

I made a "build" thread not too long ago.  Not much going on with it. Just trying to keep it running and on the road.

I vaguely remember people who raced these in SCCA ITS running 2 stock oil coolers run in sequence 

infernosg said:

In reply to sergio :

That's an idea.I guess I don't think it'd make much of a difference. The effective flow area is always smaller than the actual area of the hole. Holes in thin, flat plates only flow something like 70% effective area due to inlet losses, pressure heads, etc. I don't know how effective they'd be in this situation since we're talking round holes in a hollow, round bar. In the end I'd probably end up removing so much material I might as well just cut the hole thing out anyway.

In reply to WonkoTheSane :

According to the FSM the "relief" temperature is 149F. A "full open" temperature isn't specified but I think it's around 160F. It's a bypass style thermostat so there's always some oil going through the cooler. I don't consider the car truly warmed up until oil temperature is >-170F. If I'm driving on the street I struggle to get my temperature above 150F when the ambient temperature is 50F or less.

The radiator thermostat starts to open at 180F and is fully open at 205F. Unless I'm on track or just sitting there idling it won't budge from the 179-181F range.

Ah, my memory was off by 30° then..

I came across your thread on a search for oil cooler ducting and wanted to share what I learned when I was running an EP FC. You are absolutely correct to aim for 200C oil in a 13B...anything higher than 230C and the rotors can start to become unhappy. As the interior of the rotors are oil cooled paired with the very large surface area of the e-shaft and rotor bearings require nice and cool oil. 

Over a number of years, I went from a single oil cooler in the stock location to two oil coolers to two oil coolers with complex ducting. I looked at what Mazdatrix had done on their FC EP car and my experience was the Mazdatrix design was ace. 

The advice to watch pressures in front of and behind the coolers was validated by my experience. Here is what I had...200C all day in 90f ambients. Per EP rules, no hood openings either...

Best of luck, your FC is amazing!

So this is really embarassing but I completely forgot about this discussion and only rediscovered it in a Google search, FOR THE EXACT REASON I STARTED IT IN THE FIRST PLACE! This was a good discussion and I'm ashamed to admit I've only made one small change since then. I added a divider after the oil cooler:

Though the first page already has a good sketch I made another one that approximates my setup:

Everything in front of the oil cooler and radiator is just about fully-sealed. There may be some gaps here and there but they're small (<0.5 sq. in.). Anything that enters the front of the car has to go through the oil cooler and/or radiator. However, this setup is inadequate. This year, at hotter events, at tighter tracks and in more traffic I've seen oil temperature hit 240F and water temperature hit 215F. I'd be ecstatic to be back to 220F and 200F like I was complaining about three years ago.

There are lots of options for improvement. I can buy a bigger radiator and oil cooler and completely rework the front of the car but I'd prefer to do this incrementally and only do what's necessary. I'd like to stick with what I have and optimize it before upgrading. So keeping the current oil cooler and radiator I came up with some ideas.

Option 1:

This is as simple as it gets. Push the oil cooler back so it's right in front of the radiator. This is how most aftermarket oil coolers are added to cars. It maximizes clean air to the radiator. No split ducting is necessary and I could probably even cut out the crossbar to better seal up the whole thing.

Option 2:

Basically the same as #1 but the oil cooler is perpendicular to the airflow direction. In theory this should provide better airflow through the oil cooler but it blocks more of the radiator and the gap between the two could work against airflow. As with #1 no split ducting is necessary and the crossbar could be removed.

Option 3:

Basically the same as #1 but the oil cooler is moved to the top of the radiator. The idea here is the higher mounting location is preferable because it's in front of the hotter part of the radiator. What concerns me about this is it puts the oil cooler well above the oil pump and I'm concerned about oil flowing back into the pan when the engine is off unless I install some kind of one-way valve. I stumbled across this configuration in the Mazda Competition Manual for the 1st generation RX7s:

It's interesting to point out we essentially discussed the "horizontal type" on the first page. The Mazda Competition Manual even says it's good for a 15F reduction over the "vertical type." While I could make this work it would completely separate the oil cooler and radiator flow paths. While this is good it also means the oil cooler only sees airflow when the car is moving. I could make a shroud and fan assembly specifically for the oil cooler but that's getting into the area of "more work than may be necessary." The goal is to make some slight changes over the Winter to try out in 2024. If I'm still too hot I can make bigger/better changes next year for 2025.

I'm leaning toward Option 1 as it's by far the easiest. I like the idea of Option 3 but have concerns about the cooler being above the pump and there may be some space issues with fittings. I suppose I could put the oil cooler at any height really.

is there any way to do a 'B' modification of the horizontal type like this:

that helps get the oil cooler exhaust air out the top instead of the bottom; and continues the benefit of the original horizontal setup having independent duct sources for each cooler.

In reply to sleepyhead the buffalo :

I'm going to say "yes" but it would require quite a bit of modification and I'm not sure I want to commit to that level just yet. It actually looks pretty close to what andrewjsanford posted above for his setup. I know there's a lot to be improved on but I'm hoping to stick within the confines of existing hardware without hacking too much apart for 2024.

The ultimate end-game would be replacing the Koyo radiator for a cross-flow circle track style and the stock oil cooler with the biggest Setrab 1-series I can find, then mounting it in a horizontal configuration with some extra fans. With the way the car is being used right now that just seems like overkill.

Is the opening in front still the same as on the first page?

In reply to j_tso :

Yep, little has changed in three years. I realized the temperatures I was worried about then were really no big deal and just kind of sent it. The only thing I added was a divider behind the oil cooler between the radiator.

I'm thinking along the lines of getting more air into the front by widening the duct.

What's behind the sheet metal pointed to in green? I tried looking for bumperless FCs on rx7club but the ones I see have an intercooler blocking everything.

Can you move the oil cooler in front of the radiator?   

I run 2 stock coolers in parallel on my RX7. Both vent separately under the car through slots and the radiator gets its own supply from over the top of the cross member. Oil cooler air doesn't go through the radiator.

Water stays under 200 and oil stays under 220 now matter how hot it is outside. (car lives in Florida)

In reply to j_tso :

There's nothing behind those side pieces. They were originally square to the front of the car but a few years back I changed to the angles pieces you see now. It wouldn't be difficult to widen the inlet but I've been following the 1/3-rule so figured the extra width isn't necessary. It doesn't seem like it but the inlet area is approximately 1/3 of the total heat exchanger area.

In reply to jfryjfry :

It's already in front of the radiator but there's about 2-3 in. of space between them. On a factory car this is where the A/C heat exchanger and power steering loop live. In most aftermarket oil cooler installations it looks like they're mounted directly in front of the radiator with little/no gap, which is what I'm considering doing.

In reply to jgrewe :

Did you notice any significant pressure drops with the two coolers? I know a lot of people praise the stock coolers but I think their effectiveness is more due to volume than anything else. The design isn't great from a flow/pressure perspective. Also, do you have a separate fan for the oil coolers or is there only airflow if the car is moving? I have a spare, clean one I was planning on swapping in this Winter but it wouldn't be difficult making a parallel setup. It also wouldn't be hard to lay one or both coolers horizontally like the Mazda Comp guide but I'm concerned about conditions where the engine could be running for long periods of time while the car is stationary (i.e. dyno tuning or bleeding the cooling system).

Since I'm not racing, I don't necessarily want to jump in and make big modifications and spend big money on a setup that's overkill for my application. I've already ducted the stock setup but that doesn't appear to be enough now. The idea was the next phase was to modify and/or optimize stock or direct-fit aftermarket components. If that still isn't enough then the real modifications would begin.