Luder94

Can we get a discussion going on the advantages and disadvantages of a vented hood vs. a hood that is made for cold air induction?


Thanks in advance

Tanqueray

I am an engineer, but not a mechanical engineer, so keep your grain of salt ready...

It seems obvious to me that it is better to
1) pull ambient temperature air directly into the intake (using the hood scoop) than
2) use a vented hood to increase air flow through the engine area to lower engine area temperatures to reduce the intake temperature.

In case 1), if the intake draws air directly from the hood scoop, you are guaranteed to draw air that is near ambient. In case 2), you are hoping to cool down the engine area, but you will never reach ambient temperatures. For minimum IAT, case 1) is the better solution.

It also seems obvious that 1) will be a problem when it is raining; in AZ, I could get around this using a manual open/close of the hood scoop. I am sure that those of you in FL, TX, etc. need a better solution.

AusS2000

Agree with the above except that I would be surprised if 1) would be a problem anywhere if it was designed right. The amount of water you would get driving in the rain shouldn't be a problem, and if the cool air scoop feeds into the standard air box it will be trapped in the first compartment anyway. So long as when the car is standing no water drains into the scoop you should be ok.

And one thing we don't seem to be considering is 1) + 2). Surely 1) gets cooler air to the intake, and 2) allows the engine and ancillaries to cool better.

Schatten

hmmm, just my opinion, I believe a solution like MG's or Mugen's CAI would be better as an intake bringing in cooler air from below and in the grill, and use the hood as a way to bring down the rest of the underhood temps.

/my two cents.

bbsilver

[QUOTE]Originally posted by Tanqueray
[B]I am an engineer, but not a mechanical engineer, so keep your grain of salt ready...

It seems obvious to me that it is better to
1) pull ambient temperature air directly into the intake (using the hood scoop) than

Schatten

good point brent. personally I've seen increases in other cars with CAI's on them in the upper speeds - mainly anything over 70, there is definately an improvement, and that is usually because if you dont have a CAI / someway to route the air in, it blows right by the inlet.

Tanqueray

[QUOTE]Originally posted by bbsilver
[B]
Reason being, while you are pulling in relatively colder (denser) air under higher pressure, you are also restricting the flow.

AusS2000

[QUOTE]Originally posted by Tanqueray
[B]Also, can someone explain why need the airbox and other tubing?

ultimate lurker

Yes, I believe airbox volume is probably pretty important on this car at WOT. We have such a small intake plenum (deliberate, to improve throttle response, reference SAE article) that a large air reservoir in front of the TB may be useful in helping high rpm, WOT hp.

Additionally, there is no reason not to create both a ram/cool air and vented hood in one. As long as you isolate the intake scoop, venting for cooling (and reducing lift) shouldn't be difficult. Add a deeper front air dam to reduce underhood pressure further and you could make some significant improvements to cooling and downforce (then you need to take care of the rear, which generates about 80 lbs of lift at 125 mph according to Auto Motor Und Sport).

UL

The Reverend

[QUOTE]Originally posted by bbsilver
[B]
From the results I have seen so far, CAIs don't work so well.