Cool air vs. plenums?

[Paul Workman]

I went for a zip in da Z and the temps were in the mid 60s. I was somewhat used to warmer weather performance (summer), but that relatively "cold" air really made a noticeable difference in the LT5s output!

Which brings to mind plenum heat: A while back I saw (I believe) an LPE gasket, specifically designed to isolate the plenum from engine heat. Not to doubt LPE, but I wonder how effective the gaskets could be, considering the fact that coolant is routed thru part(s) of the plenum? The gaskets appeared to be made from some black synthetic material, about 3/8" thick. Anyone know about these??

In any case, it seems to me the LT5 might benefit from a plastic intake, similar to those used on the LSx engines, as far as keeping the intake as dense as possible...or would our ECMs and MAP system not be able to incorporate the cooler intake. I don't know squat about our ECMs capabilities in this specific regard, but some of ya do. What do y'all think?

TIA,

P.

[Aurora40]

No doubt a plastic intake would perform better and shed some pounds. I don't believe they are cost effective though, and they already put all that stuff under the plenum. I don't think you'd have room for all that crap with one of those plastic intakes.

Also the ignition module is cooled by the plenum, so you'd need to find some other way to cool it.

[Jeffvette]

My theory:

Heat rises. The plenum is on the top. Therefore heat will rise to the plenum. Doesn't matter if you have the pheonelic spacer plates or not. The under hood area does not get a lot of air circulation, and having that little bitty spacer isn't going to do much good.

[RICHARD TILL]

Heres an example of what a weather change will do to a high performance engine. If the temperature is in the low 80`s my 10 second dragboat will run in the middle 9.90`s. On a 90 degree and above day the time will increase to sometimes 10.15 seconds. Saturday is usually qualifying and Sunday is win the round or go home. I try to conpensate for this by advancing and retarding the timing by about 2 degrees.

[Paul Workman]

No doubt a plastic intake would perform better and shed some pounds. I don't believe they are cost effective though, and they already put all that stuff under the plenum. I don't think you'd have room for all that crap with one of those plastic intakes.

Also the ignition module is cooled by the plenum, so you'd need to find some other way to cool it.

Well, I was thinking more of a plastic replica of the existing Al plenum. That way nothing would have to be relocated. And, the plenum could come molded in any color with the 36mm bores in it, or the Siamese partition removed all together. Then one would only have to port the IH for a top end P&P project.

I know someone that does prototype fabrications using a computer and a special 3-D program and a machine that actually lays down the prototype in thin layers of plastic - takes a couple hours or so to go from graphic to physical "part". The dies are the expensive part - once it has been determined that the prototype has been vetted.

Just mulling over what could be done: "what if", as it were.

P.

[Aurora40]

Ah, gotcha. I wonder if it would be easier then to simply do it in CF since you could create the mold from the existing stuff. It wouldn't require expensive tools, just skill and patience. Would you also do the injector housings this way?

According to the LT5 STG book, the ignition module pumps heat at a rate of 110W into the plenum though.

[Jagdpanzer]

Has anyone ever taken temperature measurements of the combustion air inside the plenum when operating the engine under real load conditions on the road? Would be interesting to see just how much the temp gain is with high air flow going through it. I suspect it is a lot less than what is seen with the hood up and engine idling when very little air is passing through the plenum by comparison.