How Much Is Too Much?

[basil135]

Is there such a thing as too much cold air going into the engine? I am fitting the typhoon cai behind the headlight, but am also looking at increasing the size of the top cai.

A workmate of mine told me that unless you have an edit done, the ECU will pick up on the extra air & re-tune the engine. Nett result - no advantage. (he drives a dunny door so what does he know)

Is it worth me going to the hassle of the larger cai, or is it a waste of time?

[cqae]

the engine can only draw in what it requires. Engine vacuum sucks in what it needs, this is measured by air mass meter or map sensor in the falcons case. The idea of the cold air intake is really to get in cooler, & therefore denser air which combusts better. Basically I dont hink you could put in too many cold air intakes, but it would be a waste of time, you can only get in so much air.

[bkofoed]

Remeber the manifold runs at a positive pressure when on boost. The compressor wheel creates a vacuum on the intake plumbing towards to atmosphere, and a positive pressure towards the engine.

It takes power from the exhaust to do this, by converting kinetic (energy in air movement) to mechanical (rotating exhaust and therefore compressor wheel in the turbo) to do this.

Sucking the air from the atmosphere through say a drinking straw would work, but the restriction to airflow would be passed on as additional mechanical resistance to turning to the turbo, and thus passed on againa as additional backpressure to the engine, resulting in sluggish performance and possibly even a rev 'cap' (airflow cap really) depening on how bad the restriction is!

There are benefits in adding the CAI, and certainly an increase in induction noise (coupled with a cotton/oil air filter such as BMC/K&N).

What is less proven is if this slight reduction in restriction causes any faster spool in the turbo (I.e. turbo reaching factory boost limit lower in the rev range) or not. After looking at other people's photos on the crossover pipe diameter in places I'm less conviced about the big-mouth CAI benefits, but given the low cost and satisfaction of extra noise (and doing it yourself!) I went for the bunnings 100MM plumbing pipe adapter and XR8 snorkel too.

Hope this helps!

BK

[cobrav8]

I like the straw analogy. Try breathing through a straw, and see what its like.

But..

Try breathing through a pipe that is a foot in diameter - comapred to a a 10ft one - wont make any difference. It all depends on whether the standard intake restricts the airflow (we would assume it does - hence the F6 having the CAI).

[bkofoed]

Do we know if the crossover pipe diameters internally are increased on the typhoon?

The photos showed a diameter on a normal T of about the size of a 50 cent piece as the intake air crosses the engine to the intake side of the turbo.

Maybe the crossover is redesigned to be less restrictive on the FPV versions? Maybe it's just wishful thinking

Intuitively I would expect a second CAI (the normal one is kindof a cold-air intake as it's mouth is ahead of the engine hot air) to add something of benfit, particularly at speed with the high capture area helping to pressurize the plumbing between the atmosphere and the compressor wheel.

Given that it is much easier to add the 2nd CAI than re-bore the crossover pipes, I'd be going for it.

As for factory ECU, yes it will restrict boost, but it does not actively restrict how quickly boost is reached due to more efficient plumbing (for the intake side at least- the exhaust system has a big influence on how well the wastegate works so radical exhausts can cause limp mode without other changes such as wastegate porting- been through that on my TX3 4WD!)

Ofcourse no intake plumbing and a smooth bell-mouth style adaptor direct to the turbo intake would be ideal. I still have images in my head from turbomustangs.com where you can see the compressor wheel through the front bumper! Ofcourse that was on a drag car, but still I wouldn't want to catch a bug on a 80,000 rpm+ compressor wheel!

Good luck

Edited 22/02/06 01:52 AM by bkofoed