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I just recently bolted on a c30-84 rotrex into my nb2 miata and first time on the track with all this hoopla was last sat.
Car performed well, but did notice temps got a lil high (stock coolant gauge in the red - installing proper gauge before next track day) in 80-90 outdoor temps.
Car has a reroute, supermiata radiator, tse 16 row oil cooler, half assed ducting (I added some coroplast from bottom of radiator to bumper opening to ensure air that going below the ic to the radiator) and hood vents. Future plans include better ducting, and hood vents.
Buddies argue that if I pull the AC, my heat issues will go away. I want to keep AC for as long as possible (I'm weak sauce) and wanted to see if anyone has had success with FI (250whp or less) in their track car while retaining AC.
I've read Andrew's Acama build thread, but couldn't find if he ended up being able to retain ac while enjoying decent track temps.
Tldr: Anyone running a reliable 250whp FI Miata while retaining factory ac?
Last edited by jtt; 05-15-2019 at 02:28 PM.
Reason: Clarity
if an oil cooler still doesn’t help enough and you already have all the ducting you can get then the next thing that I can think of is the trackspeed radiator.
if an oil cooler still doesn’t help enough and you already have all the ducting you can get then the next thing that I can think of is the trackspeed radiator.
Thank ya, I forgot to mention I have an oil cooler as well. Updated original post .
So next steps: finish ducting, add gauges to properly measure temps and if still having issues, throw money at car.
How long does it take for your engine to overheat?
And what coolant do you run? Looks a bit nasty.
Took about two laps in anger at thill West (1.8 mile track) for the gauge to show in the red during the hottest part of the day.
I recently replaced the coolant with distilled water, quart of coolant and half a bottle of water wetter... My overflow tank has dried coolant crap stuck on the insides that I prolly should hose out.
First get your ducting in line that will make a huge difference. I didnt notice if you are running the factory undertray. If you arnt that will kill you temps right away. There is no reason you cant keep ac on the car maybe just dont run ac on the track if it keeps being an issue.
Are you running a megasquirt? If so, do you have the fans setup to turn off after a certain speed or do the fans stay on indefinitely after the car is up to temp?
Also, do you have your megasquirt setup to pull timing as the temps increase? If so, that might exaggerate overheating issues by increasing exhaust gas temps.
First get your ducting in line that will make a huge difference. I didnt notice if you are running the factory undertray. If you arnt that will kill you temps right away. There is no reason you cant keep ac on the car maybe just dont run ac on the track if it keeps being an issue.
I was okay at 250 to 260 on the track with AC condenser still present. Was using an oil cooler and a triple pass radiator, GV copy lip, homemade undertray and ducting sealed up with foil tape. I also trimmed my bumper mouth opening on the top side to allow more airflow over the crossmember so it wasn't all having to go between the crossmember and the intercooler. I also space the intercooler as far down and back away from the crossmember as possible to allow more air to go around the intercooler. Are could travel beneath the intercooler as well. Must get air to the radiator.
Now that I'm over 300 it's all gone to hell again and I'm having to improve further.
Are you running a megasquirt? If so, do you have the fans setup to turn off after a certain speed or do the fans stay on indefinitely after the car is up to temp?
Also, do you have your megasquirt setup to pull timing as the temps increase? If so, that might exaggerate overheating issues by increasing exhaust gas temps.
Good call. I have a MS3 PNP will check tune to confirm.
Originally Posted by DNMakinson
I truly hope he is not running A/C on the track.
So you are saying I can't be cool and fast at the same time?
Originally Posted by matrussell122
First get your ducting in line that will make a huge difference. I didnt notice if you are running the factory undertray. If you arnt that will kill you temps right away. There is no reason you cant keep ac on the car maybe just dont run ac on the track if it keeps being an issue.
I have an LRB undertray that I've modified to allow clearance for the IC piping. I'll work on ducting next to seal all air from bumper to radiator.
I do, but I'm at 350+ WHP. I've had this setup a bit over 7 years.
Edit: Full ducting on the radiator, intercooler and for brakes. I also have a heater core shutoff valve and oil cooler. I'm using a PWR radiator.
Originally Posted by sixshooter
I was okay at 250 to 260 on the track with AC condenser still present. Now that I'm over 300 it's all gone to hell again and I'm having to improve further.
What does your heat exchanger stack look like? Basically how many heat exchangers do you have stuffed into the mouth of the car? How much "clean" air is the A/C condenser and radiator getting? If all the heat exchangers are in front of the radiator (IC/engine oil/Rotrex oil), you might want to consider moving them around to make sure the A/C & radiator are at least getting some clean air that isn't pre-heated by the IC or oil coolers.
Another factor is the fan setup. What fans are you using?
What does your heat exchanger stack look like? Basically how many heat exchangers do you have stuffed into the mouth of the car? How much "clean" air is the A/C condenser and radiator getting? If all the heat exchangers are in front of the radiator (IC/engine oil/Rotrex oil), you might want to consider moving them around to make sure the A/C & radiator are at least getting some clean air that isn't pre-heated by the IC or oil coolers.
Another factor is the fan setup. What fans are you using?
I'm using the fab9 ic, which makes an easy install but blocks a good amount of space in the front opening. I have rotrex and engine oil coolers out of the main stack and pulling in their own air from empty foglight holes. Stock fans are still in use. I think some ducting behind the bumper cross member and on the sides of the hear exchanger stack are my next steps?
That's a big intercooler. You should definitely look at where I trimmed the top of the bumper mouth to allow a larger volume of air to go up and over the crossmember and then to the radiator. Don't be afraid to duct the intercooler in such a way that air may pass from the bumper mouth bottom freely beneath it to the radiator.
My build thread is 11 years long. Start with the end and work backwards, lol.
I remember reading that the crossflow supermiata radiator is designed for a naturally aspirated track car, without accessories, with ducting.
Street car / dual purpose car with a/c requires the trackspeed rad.
Nope.
Works fine on boosted cars with A/C. The core is hyper efficient provided it has good airflow. Where a thicker, heavier core make sense is when you have poor airflow or rely on fans to move air at low (stop n go traffic) speeds.
We have run w2w at 400whp, close drafting in 80° for 40 minute races and never gone above 210° with the crossflow.
05-15-2019, 02:16 PM
Track FI car with ac?
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I was okay at 250 to 260 on the track with AC condenser still present. Was using an oil cooler and a triple pass radiator, GV copy lip, homemade undertray and ducting sealed up with foil tape. I also trimmed my bumper mouth opening on the top side to allow more airflow over the crossmember so it wasn't all having to go between the crossmember and the intercooler. I also space the intercooler as far down and back away from the crossmember as possible to allow more air to go around the intercooler. Are could travel beneath the intercooler as well. Must get air to the radiator.
I've had this setup a bit over 7 years. 
