I have heard that a desirable IAT at WOT near the peak of the power curve is about 20 deg F above ambient temperature. Is this a reasonable goal, and why? Also, if one has a system that reflects that level of IC efficiency, what will be the power gains from going below that level with something like alcohol-water injection? How low can/should the IAT be allowed to go?

I know there are a lot of variables affecting the development of power and torque, but my questions above assume the other factors are held constant, with ambient temperature and IAT being variable. Any comments would be appreciated :smile:

 

I don't see any hard and fast rule for intake air temperature, other than lower is better in most cases. IAT varies greatly in the MCS, depending on driving conditions, mods, etc. Even completely stock, IAT can get VERY, VERY hot just idling in traffic on a warm summer day. I've seen 80C (176 F) under those circumstances. Of course, once traffic cleared and I started moving, airflow through the IC dropped that figure about 40C very quickly. Since the engine runs fine in sub-freezing temperatures, getting the IAT significantly below ambient shouldn't be a problem.

The relationship between IAT and its contributing factors is pretty complex in the case of the MCS, and is made further complex due to the presence of mods (like a 19% pulley, which has a much steeper temp climb than the stock pulley or even the 15%). The best we can do is try to get IAT's as low as possible in the conditions where we really need the air to be dense (WOT), without restricting the flow any more than absolutely necessary. Bolting on a larger IC is a double-edge sword. On one hand, the extra mass serves as a bigger heat sink to absorb heat from the intake air. On the other hand, that extra mass holds onto that heat and requires more time/airflow to get rid of that heat than does the stock IC.

A sprayer or evaporative injection setup can definitely help if done correctly since it makes the most of the heatsink that you already have. Of course, the downsides are complexity, refilling of your evaporant of choice, etc. AutoSpeed had a great article about their IC sprayer that seeks to anticipate when the spray will be needed, for the best performance:

http://autospeed.drive.com.au/cms/article.html?&A=0527

 

andy: I saw a guy using your temp gage on Food TV measuring intake air temp (or was it exit air temp?) on a Weber grill full of smokin' ribs

 

Yeah and he still didn't get close to your IATs.

 

Andy,

Many thanks for your post and reference to the articles in AutoSpeed. After placing my subscription order, I read the articles and found them to be most informative. I've heard very favorable comments about this magazine, and now I'll be checking it out every week

Be cool (pun intended),

 

Andy,

do you have any data as to what temps affect has on power? i.e. IAT of 180F means you will lose 20% of your power...???

 

I saw an updated version of the Andy intake temp gauge...now it has a recorded voice that tells you "your turkey is done"

 

https://www.northamericanmotoring.co...ad.php?t=23089