I got a 07 R1 that running hotter than I'd like this time of year, I have had the issue for a while and went to a bigger radiator this year hoping maybe it might help but didn't. I got a restrictor in the thermostat housing with a 5/8 hole and still running warm, the water is moving pretty quick thru the radiator so thinking maybe I need to restrict it more but thought maybe someone else has had this problem and found a fix. I am on alky.

STIF

We run a stock thermostat with 4 1/4" holes drilled around the outer portion of the thermostat. Most ECM's are mapped to work best at 190 degrees. If you can see water circulating it is probably moving too fast. As mentioned in other posts a partially clogged injector will also build extra heat. Is your radiator upright or layed down?

It is possible to race at 190 and as soon as the car slows and leaves the track for the temp to spike up also.

Honest Dad himself

WE RUN A 32# CAP/WATER WETER/50-50 MIX ANTIFREEZE/1/2" ID.FENDER WASHER FOR THERMOSTAT..STILL RUN 220-230. EVEN OPENED ALL AIR VEIN IN RADIATOR. HAD A NEW FUEL MAP HOPEING TO CORRECT HEAT ISSUE. ALL THE THINGS WE'VE TRIED HAVE NOT REDUCED TEMP HARDLY ANY. LAST YEAR CAME IN A FEW TIMES AFTER FEATURE AT 245. WE happen to have a hoist and raise the front of car (while running) to make sure all air is out of system.

I know the guys who put the R1 motors in Rhinos all had temp problems. They started off running dwarf car radiators and all ran about 250 so they went to much bigger radiators to get the temps down. Also most went to a lower temp setting to turn the fan on earlier. End of the day its the radiators job to cool things down, if the radiator is to small restricting the flow isn't going to help. You need to throw more COOL water at it to cool it down, you also need to look into how much air the radiator is getting. There needs to be a positive pressure in front of the radiator and a negative pressure in back, without enough airflow the radiator is just going to turn into a big hot lump. To high a percentage of antifreeze will also make things warm.

Ron

We welded a little 3/16" bung in the top rad tank and used the bleed tap in the block an hose to bleed it as it runs. We also use a catch tank so that when any water blows out when it cools it pulls the coolant back into the radiator. Try the thermostat deal.

Honest Dad himself

Something I'm sure no one is doing would be to to use an expansion tank mounted up high on the firewall to bleed the system the entire time the car is running, would help big time if the radiator is lower then the highest part of the motor. You just run a bleed line from the top of the radiator and top of the motor to the expansion tank to bleed the system and a #6 or #8 line from the bottom of the tank to the line going from the radiator to the pump.

Mac

We did that expansion tank a few years back, The biggest problem is there is very little room on a mini sprint firewall and a coolant recovery bottle works just as good and is easier to mount. We had so much problem cooling a little old F4 Honda on gasoline that we had Griffin radiator fabricate a radiator with a NASCAR Winston Cup core in it. It worked pretty good but it sure was heavy and a bit pricy also. Wonder if any of the guys racing Engler injection and using electric water pumps are having this problem also with the R1.

Honest Dad himself

Lmao,,,yeah thats it....

Heres a pic, doesn't take much room

Mac

What kinda of car is that anyhow? Where is the firewwall? What is that big tank on the left of the pic for? What is that thing made in Spain? Is the surge tank mounted on the firewall?

We used that little half ball type tank but only because we were trying to be like midgets at the time and laid the radiator down and below the cylinder head.

Nice workmanship and neat and well planed.

Honest Dad himself

Heres a dirty little video of the car. I made a big shock change, you can see the rear is way soft but notice how much torque the R1 has.

https://www.youtube.com/watch?v=KG5mqCVWr6I