RallyJon

Any of the on-line "tuner" shops can sell you a gauge so you can monitor intake air temperature. We were running the liquid intercooler on the rally car, and there were conditions when I would upshift based on either EGT or intake temp, rather than redline.

eclou

Good tip on the gauges. In my experience though detonation/pre-detonation is most likely to occur at peak cylinder pressure/peak torque and not necessarily redline

Sooner

This may be a dumb question, but if you are adding an RS/turbo wing, intercooler w/ radiator, water, & the SC itself, how much weight is all that? What is the true net HP gain after you fator in the weight of the additional parts?

While I am sure it's a good increase in HP, you should factor that into the $ per HP equation.

Marlon

To me optimum cooling of an H2O based intercooler would occur by routing the intercooler coolant through a specially designed and plumbed fuel tank of the 993, etc. Gasoline stays at a very cool temperatureduring it's time in the tank (even when its REALLY hot outside) and it would be an excellent sink to pull heat out of coolant lines that are plumbed either through or around the fuel tank. We did it in the military helicopter aviation industry. My helicopter was modded to route hot engine driven gearbox oil alongside fuel being drawn from the main fuel tanks. The fuel line and hot engine oil lines were actually co-located with each other in a twisty fashion so that the cold fuel was in close contact with the cold fuel line and it actually pulled the heat out of the hot oil line. The lines were metal-on-metal of course. This worked so well that the engine power was actually uprated based on tangibly lower engine oil temperatures during nominal engine operations and engine loading conditions. I will gladly give my correct name spelling for the credit line on this idea for the Porsche 993, et al

Stealth 993

They use JP5 that is basically diesel fuel, it needs to be heated to not turn into a gel.

Our gas needs to be cool! The higher the fuel temp, the more vapor & the specific octane will be lower, plus it will expand more, so you will get less HP per volume.

So basically, you would cool the IC & get lower IAC, but you would negate it with the far warmer fuel.

eclou

Have you considered perhaps using something like an Aquamist or Snow Water/Meth injection system?

TheOtherEric

A couple people here have done it on TPC setups, and it seems to work. However, I'm inclined to agree with Corky Bell (Maximum Boost) who believes that it's a band-aid, and a better solution is to install/improve intercooling.

I'm thinking that S/C's simply put off too much heat for reliable track use (Roots s/c's are very inefficient). They require LOTS of cooling, hence the A/W intercooler. But then you're talking a very complicated install with lots of stuff to go wrong (what if your water pump fails?!). Sure it works, but there's risk. A turbo conversion is much simpler, and since you're not fighting the extra heat generation, a simple air-to-air intercooler works fine.

RallyJon

Why not use a screw-type supercharger instead of the roots m90? Should theoretically allow more boost without detonation.

http://www.whipplesuperchargers.com/...sp?ProdID=1162

TheOtherEric

Yes, screw-types create less heat than Roots, but I know they have some disadvantages too. One is that they have an internal compression ratio, so they're compressing air (and using power) even when not under boost and vented. Would likely kill your mileage. Some good reading here.

Another +1 for the turbo. Very little parasitic losses when not under boost. The big downside to turbo is that you don't get as much torque at low rpm's.

RallyJon

Whipple's site says 1HP in highway cruise with the bypass open. I bet that's on an American V8 turning 1200 rpm, but still pretty low.

Another cool option is the Rotrex. It's a geared up centrifugal SC that supposedly gives better midrange (though certainly not as good as a roots). I wonder if you could mount it where the AC compressor is and even use the stock manifold? http://www.rotrex.com

Marlon

Hey Stealth - Excellent points! My military helicopter did not require the use of fuel with the Fuel System Icing Inhibitor (FSII) that you might be referring to. I have never seen any type of JP fuel in a gel state even in subzero conditions. In our aircraft, we were permitted to use commercial fuels since each of the three T64GE-416 engines had an adjustment that could be made on the FCU to accomodate the specific gravity of a particular alternative fuel. Primay fuels recommended for the CH-53E were JP4, JP5 and JP8 (basically Kerosene)
Also: I don't think hot air + cold fuel ='s the degree of zoom that you are hoping for. If the inlet air charge is very cool or downright cold, then you might be on to something. Mostly, our inlet air is fairly warm and fairly warmer in the Summer. The only time you get close to the highly desired inlet air nirvana is in the winter time. Cooling the fuel is one thing, but you gotta' have cool air too. The NA 993 does not get consistent cool inlet air.

Stealth 993

Sorry, don't have much direct whirlybird experience.

My point is Car fuel should be kept cold & Diesel type fuel works better when it's a little warmer. I was on a ship with JP5 & they used to have steam radiators in the fuel to keep it at a constant temp, & some additive, so it would not absorb so much water.

Marlon

LOL! Sounds like you were on an olde timey ship! Yes - ships have a lot of water in the fuel and a lot of fuel in the water. Remember the last time you took a shower and the water smelled like kerosene!

Stealth 993

It was a Guided Missile Nuclear Cruiser, CGN-36. 650ft long, 75ft beam, 500 crew.

TheOtherEric

Ok, back on topic guys. Thought y'all might be interested in seeing this SC kit, for a little perspective (for Lotus Elise/Exige). For $5000, the kit maker includes injectors and proper ECU remapping in the kit. No 7th/8th injectors. Kinda interesting.