Hot Air Intake Air Temperature values

[boostm3]

I usually post over in the alky injection section, since, while our cars may be different, we at least share that technology. But I also share something in common with you guys: I have no intercooler! Thus, my '99 M3 with Vortech blower, which Ive boosted to 11 psi courtesy of water injection despite the 10.5:1 static CR on the engine, does fine.. But Im wondering, have you guys measured your Intake Air Temperatures? I find that on my setup, I frequently have readings that are about ambient + 100 degrees F, if not a little more. Whats even more interesting is that I can get such measurements after a run without even using the supercharger! That is to say, on a 90 degree day, I can cruise for an hour at say 4000 rpms, with EGTs around 1100 degrees using no boost, and my IATs will be around 190 degrees. If I take a remote temperature reading of the intake pipe just before the throttle body, it will typically read about the same. So I guess the heat of the engine bay is heating up the intake pipe and the supercharger case even if Im not making any boost, and that this temperature is then leached off into the air flow..I would have thought the time spent in the intake pipe is too short for the air to pick up the surrounding temps, but I guess this isnt true.

Of course, as soon as I approach 5 psi, the water injection is triggered, and temps will rapidly fall by over 50 degrees. So, ironically, my IATs at 11 lbs of boost are way lower than they are with no boost...

Is this similar to you other hot air guys??.

 

[cool 84]

So we meet again lol. We had the old charge air guage on the car back when it was a hotair, before the conversion. Typical cruising temps on a nice 60-70 degree night were ~120. Boost it up to 18psi and they would near 300 degrees.

The vortech is a centrifugal blower, right? I have a theory on that one. Since a blower is not load dependant like a turbo but rather rpm based, when you're spinning the motor 4,000 rpms, even though your're off boost, the compressor wheel is still spinning the same speed as if you were on boost. While the compression of the air is what generates some of your heat, it's the friction of the blades of the wheel cutting through the air that makes the majority of the heat.

I wish we got into the alky before adding intercoolers but it never happened. There are a few hotair people around here that have had good luck with alky. I'm sure they'll chime in.

 

[boostm3]

Hey Cool84.... I think your explanation might be part of it. However, dont forget, mine and the better centrifugal blowers use a bypass valve. Which means, I thought, that at vacuum levels, much of the air would be bypassing the blower, right?

I thought bypass valves served two main functions: to allow the air to escape if the throttle is slammed shut so that the wave doesnt bounce back into the blower causing damage, and to allow air to bypass the blower when pressures are in vacuum.

 

[cool 84]

You could be right. I admittedly don't know a whole lot on how the blowers are set up. I've never heard of a bypass valve on a centrifugal setup, I guess you learn something new everyday.

Just curious, but looking at your intake tract, is there a way for air to completely bypass the blower?

With your kind of temps the blower almost has to be adding heat, I can't imagine that kind of heat coming from anywhere else. Even in hotair form, my car ran lower temps and that is with a crappy intake manifold that's heated with engine coolant. You do have some kind of cold air intake, right?

BTW, there's a local guy here with a blown M3. I think he's more into autocross but it's a nice car. I've heard he's waiting for the warranty to run out before he cranks on the boost.

 

[boostm3]

>>Just curious, but looking at your intake tract, is there a way for air to completely bypass the blower?<<

Absolutely. Theres a hose that runs from the intake tube on the output side of the blower, to the tube on the intake side of the blower. This serves the bypass in two ways: it provides the escape for the air that gets trapped when the throttle slams shut, and, it provides the route to bypass the blower under vacuum.

>>With your kind of temps the blower almost has to be adding heat, I can't imagine that kind of heat coming from anywhere else.<<

Well, look at it this way. Almost the entire engine bay is registering temps over 150 under heat soak. The outside of the intake pipe is like 190. But, even the piping before the blower is well over 100 degrees. Thats at idle. Naturally, at speed, some of these temps drop, but then, its hard to measure with my remote IR thermometer at speed

>>BTW, there's a local guy here with a blown M3<<

Yea, there are a fair number of us

 

[cool 84]

Maybe a good cold air intake is what you need. We saw ~50 degrees change in the IAT (located near the filter) on my dad's car with a cold air system. Of interest is the change didn't show up on the charge air guage and the air at the filter sensor was still quite a bit above ambient.

Another thing that doesn't pertain to this thread is on my car with a K&N located in the hot engine bay, the intake air temps would be hot, in the 120 degree range. On a WOT run they would go down to ambient. Even at part throttle the temps would start going down. This tells me that cold air induction systems only help during idle to part throttle.

 

[boostm3]

>>Maybe a good cold air intake is what you need<<

Already got one! It comes with the SC kit, and comprises a K&N mounted down near the wheel well, beneath the engine bay. But, by the time the flow gets through the heat soaked intake tubing, its over 150 degrees. Dont forget..on our cars, the IAT sensor is in the Intake Manifold, also subject to heating in the heat soaked engine bay. I think maybe what I should do is have somebody craft some exhaust vents in the hood, or buy a vented CF hood. Or just wait til someone comes out with a reasonablyl priced intercooler for this application. Believe it or not, there are only 2 avaiable for us now, and they cost over $3000!!!!!!!!! I know, our market is continulally getting raped. Til then, Im pretty happy with my 50-75 IAT drop from the water/alky injection.

>>a WOT run they would go down to ambient. Even at part throttle the temps would start going down.<<

Wow...mine goes down too, but from about 190 to maybe 170. With winjection under full boost, it will go down to about 140.

Maybe the supercharger is just heating everything under hood up so much theres not much I can do about it. Dont get me wrong; the car is still making nice power, but it could be better. You should feel it before heat soak sets in, or on a cool dry day, when it never seems to be much of a factor