[Dr J]

After doing an EFI conversion and street tuning most of the VE table, I decided it was time to reinstall my rebuilt supercharger and take it to a dyno to tune boost and high RPM sections. When I talked to the dyno guy I told him I would have the supercharger belt off until I got there to ensure I don’t get into boost. He said to use the engine protect function of the ECU and limit MAP to not allow boost. So I did that and it worked. But, as I drove the car, I found something that concerned me.

Having IAT readings for the first time, I saw that it went very high when accelerating, even at a very conservative rate. They would go 150F or even 180. I’m sure I could get it to 200, and this without boost!

So I completed installation of a water meth kit to discharge at the inlet to the supercharger and used water alone to see if it helps. I did not see significant improvement in temps. So I calculated heat transfer from water at 90F to IAT at about 150F and found that it doesn’t have a big impact, particularly since the water doesn’t change states until 212F. I did not account for any evaporation since there is high humidity here anyway.

With the supercharger removed, there are no IAT issues.

I have a blow off valve and can feel the hot air come out of it when I manually rev the engine, and feel the bypass air. Also, the high IAT lingers for a few minutes which I believe is due to the response time of the “fast acting” GM IAT sensor. I took out the sensor to check that it is operating well and saw that the plastic protector at the tip of the sensor was curved. When I touched it, it came apart. The sensor though seems to work well, responds to temp changes and is close to coolant temperature and ambient temperature when first started.

So, based on the experience of others, are the IATs too high?

Any suggestions? An intercooler would be difficult since the supercharger takes 1/3 of engine bay, I have an AC compressor and a mounting platform for other sensors near the throttle on the passenger side.

Supercharger is a whipple twin screw. There is no intercooler. Water injection nozzle flows 350 cc/min though I can lower it to 170 by PWM the pump. This data was obtained via testing. The air intake is through cylindrical K&N filter close to the firewall.