monitoring intake temps

[twospoons]

thnx for the info jeff... i really wasn't sure where they got that 1075* number... and if that really was a "combustion temp"... then why do we see egt's in the 1600*F range ... its not like the temp is gonna shot up 600* as it leave the combustion chamber and goes into the manifold???

wraith: if i can scrape up the money for some sort of IAT gauge i'll get some numbers before and after i do my dsm sidemounts upgrade... got 2 nice looking 1g dsm sidemounts (only $50!!!) sitting in my kitchen... just need to find a decent aluminum welder in the area.

[Jeff Lucius]

There is more to IC efficiency than just the size. I don't know if the Alamo's are typical or not as far as efficiency goes for their size. Reading on the internet () I see numbers around 50-65% eff. for some factory ICs. Looking at aftermarket ICs (name brands) we see IC eff. in the range of 65-85%. I would guess an IC that has an efficiency above 90% would be exceptional (and worth getting!!). Heat soak would be the other IC function that should be important to us. This is where size, or mass, may help a bit. *If* 75% is average efficiency of the Alamos then that would make them "OK", not bad and not exceptional.

As you guys have pointed out, we need before/after IC and ambient temp measurements for factory and aftermarket ICs under different driving conditions (idle, street driving, highway cruising, WOT, drag racing, open track racing, etc.) so that we can evaluate which IC would be best for our cars and driving situations.

Unfortunately, few owners are willing to shell out the bucks to take these measurements. Think about how many 3S owners have ever had their fuel pumps flow tested. Maybe 6? Owners love to get free info and rarely want to pay to find out for themselves (there are some notable exceptions). Just another reason that 14 years after our platform's introduction we are still struggling to advance its performance.

[cbatters]

Two questions.

1. I have seen conflicting data on power gains based on lowering intake temperature. Obviously lots of factors beyond increasing air density ( reducing detonation / pulled timing etc.)

What do you think a reasonable estimate is for HP gain based on lowering intake charge temp? (Is it the best HP/$ ROI)

2. Any opinions on chilled water IC systems? Storing up chilled water and using it to lower intake charge temp seems interesting. I have looked at several systems online but have not seen any hard data about performance gains. (I also need to do the math to see how much chilled water would be required to store enough BTUs to lower intake temp by 50 degrees for ~30 seconds to see if it would be practical.)


Clint

[Jeff Lucius]

You mean IAT in the plenum right?

You know, most of the "wisdom" is for normally aspirated cars. And for sure, they need all the help and tweeks they can get. Forced induction is a different ball game. For us (VR4/TT) lower IAT (in plenum) means most of all reduced tendency for detonation. With that we can raise boost and make more power. On the other hand, as long as knock is controlled (or kept to a reasonable value) just about any IAT or boost is fine (as long as bottom end can handle the cylinder pressures). Lower IAT (in plenum) is always good; it is just not always required to make big power.

Remember mass flow is constant, for the most part and over a short time period, through the intake system. Mass flow out of the turbo at 260ºF is the same as the mass flow into the plenum at 108ºF. The difference will be the pressure and density. The difference between 260ºF and 108ºF sounds like a lot till you remember the comparison must be made on the absolute temp scale, 720ºR vs. 568ºR or about 26%. My web page below steps through the changes.

http://www.stealth316.com/2-primer.htm