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Ram Air calculations

M

moderndino

CEG'er
Joined
Jun 2, 2005
Messages
53
Location
south central PA
I don't mean to stir the ire of true forced induction types, but I wanted to ask compressor heads about my application.

My custom sports car will be Contour powered, 2.5L from 95. I won't modify the engine to start except for the intake plumbing and filter, and a low restriction exhaust.

The body of this car is sleak, and I will build air scoops behind the side windows (it's mid-engine) with an area of roughly 84 inches each, out in the clean air. Both sides will feed a common plenum with the engine air filter in it.

I realize there's not much pressure involved, but wild guess is between a half pound and two pounds at highway speed. So based on the bottom of the curves you compressor types have real knowledge of, will the stock metering range handle this? It's like going a bit below sea level if you want to think of it that way. Just causually, do you think there's maybe 10 HP there?

Thanks, and appologies in advance where needed,

Gar
 
You wont gain anything from a raim air setup. At least nothing from ramming air into the intake. It may draw in colder air which is good, but nothing like positive boost pressure. I think some people have tried a ram air setup and it has caused some stalling issues on the highway due to erratic MAF readings.

Btw, what engine management are you using for this motor? If your swapping over the contour engine harnesses, I suggest picking up a 96+ engine and harnesses so you dont have to deal with OBD-I. You may want to consider a 3.0L as well. Theyre just as cheap as the 2.5L, and externally the same size since its just a 2.5L bored .5L bigger.
 
With the size of the openings you're talking about you'll have to be travelling at roughly 95mph to achieve 1psi of positive intake pressure. Thats really not bad in terms of making power, however, any gain is going to be lost at speed due to drag created by the relatively large intakes. (food for thought)

Got any renderings of this sports car you're talking about building? I'd love to check it out.
-Mark
 
Thanks guys for the input on forced HP. Based on little or no gain, does that also mean it's a no-brainer that the stock engine management will supply enough gas to keep the mixture correct?

The car was a replica kit of Ferrari's poor man's line, Dino 246. It's a beutiful car. The Porsche 904 is the same shape. Mine was built by Kelmark. Some of these had a tube frame and used oldsmobile 8 cylider/FWD transaxle... The larger share used a VW pan, although many sub a Subaru or Maxda rotory for the VW powerplant.

I dream of eventually getting the Noble engine and 6 speed, but since I'm building from scratch, I'll be using the duratec pretty much the way it came out of the Contour, and spending loads of money on making the car drive first. Then in the next phase, I'll make it drive fast. For now I get the gain of the 1000 pound saved weight compared to the Contour, and mine was very peppy.

I toyed with using the alternator compressor, and even traded some mail with the designer (he once had a Kelmark himself), but I am a bit lery of the alternator belt slippage, plus I would need to do all the management cost before I get to drive it, and that tiny glimmer at the end of the build tunnel slaps me back to practicallity. The scoops will be on it in any case, cause it will look soo cool. There's loads of pictures at the Yohoo Kelmark group, or just google Dino 246.

Thanks again for the advice.

Gar
 
Well they definitely won't hurt. They won't help down low though.
Reduced restriction and even a little ram air effect will help reduce pumping losses almost like a lower restriction intake would.
I'd say do it if it makes you happy but don't count on any serious power gains. Use some sort of supercharging to get what you want (i.e. turbocharger or mechanicalsupercharger)
 
Doug,

You offered a mechanic shop suggestion for my girl. Thanks for that. Why not stop by for a visit down here and I'll give you the project tour. There's enough to see to be interesting, and I'm working on it most free time. Definately Saturdays. I make it up to Centerville exit in about 35 minutes. This weekend is slated for wet, but mildly warm. I'll make it a standing invite. PM for phone number.

Gar
 
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