Radiator Question
 

This is for a club racing application - not a street car.

This may be a stupid question but....does porting a rotary engine make it run hotter? If I have a cooling system that worked on a stock port engine do I need to add capacity to cool a more powerful engine?

I am building a street ported 13B that will run a Weber IDA carb. This is going in a racecar that I raced for 7 years with a stock port 12A fitted with a Niki. The 12A probably made around 125HP at the flywheel and the 13B should make 100 HP more. The 12A was spun up to 8-8500 pretty regularly.

For the 12A, the cooling system consisted of a Ron Davis dual pass cross flow two row aluminum radiator with a core that is 18" wide and 19" tall. I had a large electric fan I could run as necessary. The radiator had a complete sealed air box in front of it that pulled air from the stock opening. I did have an air dam to help direct the air.

To cool the oil I used a pair of Mazda coolers plumbed in parallel with -10 lines mounted in the air box in front of the radiator.

Oil and water temps were 200-210F even on hot days.

All of the EP guys I know running a street ported 12A or 13B are using Ron Davis dual pass cross flow radiators that are much bigger. Like with 26x19" cores. They are also using a couple of stock oil coolers in parallel for oil cooling. These setups work well but are heavier than my current radiator (they are bigger and hold more water) and have to mounted farther back in the car. The easy button is to copy what they are doing but....maybe there is a better way.

So, what are you guys that race doing.

i think yours would be good enough to try. it seems like it should be ok.

I think the increase in heat generation will be proportional to the integral of the extra HP you actually use around the course. Since you can't use extra HP all the time, I think your increase in heat load will be less than the 80% increase in HP.

This is probably of limited value, since you don't know exactly where you are with respect to the cooling capability of your rad.

Hopefully my experience will be of more help . . .

My car generates about 350 RWHP. I run 20 min sessions at medium-sized tracks like Grattan and Gingermann. During 90 deg days, I've run the car as hard as I can, and I haven't experienced any significant rise in coolant temp. My rad is a dual pass aluminum Northern circle track style with a core 19.5"W X 19"H. Stacked in front of the rad are a large intercooler (top) and a Setrab Com Oil Cooler (bottom) which is slightly larger than the OEM oil cooler. Obviously, the rad is seeing pre-heated air. I run 50/50 Water/Ethylene Glycol, I have a well-ducted front air dam with a larger than OEM opening, and my hood is vented.

I also think you should try your setup. Are you running pure water? Did you remove the rear hood seal? Did you have to use your electric fan in the past?

Thanks for the feedback.

I run water with a little antifreeze to prevent corrosion. I do turn of the fan on hot days and on cool off laps.

Temps spike at the end of long straights or when the car is at 8K for sustained times. RPM has always equaled heat in this car.

Something that I have noticed is that 12As seem to run hotter than GSL/SE 13Bs. My friends ITS/STU GSL/SE always made due with a stock radiator.

Sounds like pump cavitation. I used to get it when I had a NA 13B with the FB cast iron pump housing. Somehow when I went to the FC aluminum pump housing, high flow failsafe thermostat, and dual pass rad, it was cured. I mention these things because I really don't know which item(s) helped. As an example, I did a high speed run where I was at WOT for at least 2 min -- probably more. RPMs were at 8K and above for at least a full minute and temps held steady.

Which FC water pump housing did you use? One from an S4 or from an S5?

S4 fits really well. S5 doesn't. You can still do an S5, if you like lots of extra work, like ioTus, ;) but why?

Thanks guys!

I don't really know if the pump housing made a difference or not. I do know that slowing the pump down will work. Are you running an under drive pulley?

My current pulley setup is the serpentine setup that came on my 13B-RE. I wish there was a simple way to measure pump RPM while the car is driving.

you can, measure pulley diameters and do maths

Good idea, j9fd3s. I measured the pulleys:

Main = 128.5 mm dia
Pump = 95mm dia

128.5/95 = 1.35 or 35% overdrive. At 8K engine RPM, my water pump should be turning 10.8K RPM. Note that my measurements were to the OD of each pulley, when it really should have been to the top of the ribs (serpentine). But getting a good measurement of the rib peaks was difficult without removing the belt, and the error here won't be very large.

What's your pulley ratio?

probably close enough :)