Stroker, Thanks for the pic. :icon_tup: Yep, I've a couple of ideas how to solve it. That is one... All my hardware s/b delivered w/in a week or two and I'm going to try a few things...

On a positive note...boost profile is coming back into form...
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• Blue: 10/20/18, when she was running well
• Brown: 5/11/19, after picking her up from the shop
• White: 5/15/19, today :)

https://cimg5.ibsrv.net/gimg/www.rx8...a020cba4e6.jpg

Stroker, Do you have record of what your IATs were after you v-mounted your IC, but before methanol injection?

I charted it somewhere in my post. IATs spiked higher (by about double) and were slower to return back to normal following a boosted run, which was to be expected. Mazda didn't do us any favors with this car. #blackrx8sarefastest

Just looking above at one of my previous post, my IATs went from 98 to 140 during that 12.5 second pull at 22 psi. Water temps went up 9 F and IATs went up 42 F...That was 60% ethanol and water/methanol injection. Couldn't imagine what it would be without either...

Nice ! Overlaying like that is really telling the story ;) !

Looks like you managed to stop the boost drop off at high rpm .... how did you do that ?

Thanks! SET and SET GAIN on my EBC were adjusted too high. So, it wasn't boost drop, which I originally thought, but spiking on the boost rise ;). So, I went thru some progressions reducing each of those until boost rise and hold converged.

Working on v-mounting my IC at the moment. Just a temporary mock-up to test... similar to Stroker's design. If temps work out maybe I won't need that 8" IC after all. :fingersx:

So, over the weekend I ducted, sealed and mounted my IC in a v-mount configuration ...but temps didn't change much. :sad: I also observed in this configuration that when the fans turned on they were reversing "top to bottom" airflow through the IC to "bottom to top", again overwhelming the little "Koyo rad that could:" So, I found it beneficial to install a partition dividing the incoming air: air flowing over the top being directed to the rad, and... bottom area to the IC; to stop the fans from reversing airflow through the IC. Even still... the Koyorad just doesn't provide sufficient system cooling capacity in 90F+ ambient temps. :nono: When the DP rad was installed earlier this year, albeit in 55F weather, system running temps were ~180-185F, w/ no boosted run issues.

Additionally, I tested and discovered that my thermostat is going...sticking and not initially opening until ~ 210F (though indications are that it remains open after that.) :eek:

So, this week I'm repairing the leaks in my dual-pass rad while a new thermostat is on order. When received the new thermostat and DP rad., sealed and ducted in a v-mount config., w/b going in. Then we'll see...:fingersx:

EDIT 1: Correcting the record here. I found later, post #319, that a bad thermostat was the root cause of my overheating issues. Once replaced the Koyo rad, ducted & sealed, was found to provide sufficient cooling capacity.

EDIT 2: For any who care to share...I'd be interested to know what radiator set-ups and normal coolant temps others are running that live in climates seeing 90F+ ambient temps.

• rad type?
• IC mounting config?
• typical system coolant temps?

Thanks in advance for any replies.
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https://cimg4.ibsrv.net/gimg/www.rx8...84b11ebf52.jpg
V-mounted IC
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One of the things I don't like about this style v mount with the stock bumper .............. you block off ALL the air that used to go to the rad. and replace that with a smaller opening that has to be split to go in two directions . If you had the Mazdaspeed bumper ......that would probably work better. IMO

True. I do plan to get a M1-speed style body kit...once the mechanicals and heating systems are sorted.

But without testing... seems 6 in one hand, half dozen in the other:
- With the IC front mounted you can direct the bottom opening air to the rad., but all the IC heat exhausts thru the rad as well. Counterproductive.
- With the IC v-mounted you lose bottom opening air to rad (w/the stock bumper) but the IC heated air is exhausted under the car (and does not impact coolant temp).

I received my 8" IC today. So, plan to experiment a bit with both configs..

Running with stock radiator and two OEM oil coolers I have no temp issues in the summer when it hits around 90F (32C). The bottom of my IC sits flush with the top of the wide opening at the bottom of the OEM bumper. This leaves a foot sized gap below the IC (about 4") for air to get a straight shot into the radiator.
https://cimg8.ibsrv.net/gimg/www.rx8...7e6c2844b8.jpg

https://cimg3.ibsrv.net/gimg/www.rx8...ce196e0a58.jpg
In your situation I would either cut 1-2" off the top off your IC and get the end tanks re-welded, or purchase a shorter IC (similar width and depth). This should create a lot of airflow underneath the IC to the radiator.

Here's my observation indicating my failing thermostat operation.

These were taken after starting and allowing my 8 to idle in the garage ~ 7-8 min... until seeing my Profec exit coolant temp gauge needle move... indicating opening of the thermostat. Vid is Profec needle movement on thermostat opening. First pic is inlet coolant temp the moment the thermostat opens. Second pic is inlet coolant temp ~30 sec later.

Hmmm, that's not right...:suspect:

Profec initial moment after thermostat opens:


https://cimg9.ibsrv.net/gimg/www.rx8...2a3531961f.png
Coolant temp the moment thermostat opens: 221F.

v

v
https://cimg0.ibsrv.net/gimg/www.rx8...2b9b72a4d0.png
Coolant temp ~30sec after thermostat opens: 201F.

v

I'm definitely going to take a lesson from Stroker and JimmyB...and cut away more of my crash bar horizontal a la Stroker's shown below to maximize airflow to the rad & IC. :yesnod:

Jimmy - btw...Good looking 8! Tastefully done. :icon_tup:

v
v

I chose to leave my crash bar intact (it's a JDM one which isn't as tall as the USDM one) because ................IDK ..................... there's a word in it's name that kinda alerted me as to why it's even there.

Pretty sure I put my crash bar back on after the initial mock up - the pic is just to give an idea of an effective location for the IC. I recommend retaining the crash bar!

Yes, I intend to retain my crash bar. I'm talking about cutting away more of the horizontal similar to what Stroker has done.

:yelrotflm. I'm keeping the crash "bar".

Update:


Found the culprit...bad thermostat. :icon_tup: Came out in three pieces. :suspect: Swapped in the new Mishimoto, topped up the coolant, and went for a cruise. In 91 F ambient temperature...

• The new thermostat pops at ~ 170F (inlet T)
• Cruising coolant temps stabilized at 175 +/- 3 F (inlet) / 190F (outlet)
• Coolant temps rose to mid / upper 180s F after a few mild / moderate boosted runs.

:ylsuper:
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https://cimg3.ibsrv.net/gimg/www.rx8...47efb78d38.jpg
Old thermostat...in 3 pcs
v
v
https://cimg5.ibsrv.net/gimg/www.rx8...4ec14abd64.png
~175 F cruising temps
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v
https://cimg4.ibsrv.net/gimg/www.rx8...dba1d151c0.jpg
190 F exit in 91 F ambient
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Its crazy to think that something so cheap could cause so many headaches. Glad you found the source of the problems.

Xero - Thanks! Agreed. Gauges saved my bacon. Lol. OEM coolant gauge is useless w/out an OBDII reader. :icon_no2:

Cooling capacity is good now..., but w/b even better after reinstalling my dual pass rad, I repaired yesterday, & new Treadstone 8" IC ...sealed up w/ my new aluminum undertray. :yesnod:

Where did you pick up a dual pass rad? The koyo is single pass but I also saw a triple pass on summit. Would it even be worth investing in a triple?

Rkesh,

I got my DP from RX8Performance. It's designed for the RX8, and properly ducted & sealed...provides plenty of cooling potential.
https://www.rx8performance.com/produ...mance-radiator

I've no experience / information on a triple-pass rad.

Once you have made a couple of passes and got nowhere ....another one isn't going to change her mind. Wait .................................................. .........what ?

:yelrotflm

Team, Lol, precisely. That's what I was indicating in my above post #313. :icon_tup:. I've already cut away the bottom half of the bar, but had intended to cut away a bit more similar to what Stroker has done. :yesnod:

But now... since installing my new thermo and my coolant system performing so well... even before reinstalling my DP rad, 8" IC, and aluminum undertray...; I dont believe I need to do anything further to it now. :cool:

Probably not ...at least not until you take it onto the track.