damon_Z

I know that you need a high velocity fan blowing on your car for a cold air induction mod (such as SSRA2) to increase rwhp on the dyno, but would a high velocity fan also be needed for other induction mods like a ported throttle body or a lid for them to show any rwhp gains? If not, then will these mods increase rwhp even more if there was a high velocity fan blowing on the car while on the dyno? Thanks in advance for the info.

300bhp/ton

don't fully understand your question here, but I'll try and explain.

To start off, Ram Air is not really Ram Air. it is a marketing tool.

Ram Air means to force more air into the engine by compressing it. Very few if any such setups are actually designed to work in this manor. And at speeds below 150mph you'll see next to no gain with the Ram Air systems that do work. So no electric fan on a dyno is going to do anything in terms of Ram Air.

Now before people start beating on me, I'll explain further. These so called Ram Air setups do actually do something. A more appropriate name would be 'cool air duct', but it doesn't sound quite so sexy as Ram Air.

What these 'cool air ducts' do is allow ambiant air to enter the intake. Remember it's not necesarily cold air, as there is no real cooling taking place, it is mearly outside air instead of heatsoaked air. So there is no real way of getting the intake air temps below ambiant.

The only way to force more air into an engine is via compression, not air flow (although they are related). Think of it this way, if an engine sucks in 1 litres worth of air to completely fill a 1 litre space you can not simple try and add another litre of air because there is no room for it. This is what any fan will try and do. What needs to be done is get 2 litres of air into a 1 litre space. If you think back to school when you drew diagrams of gas/liquid/solid particles. The gas particles are far apart allowing them to be compressed. this is what FI does.

A Ram Air system if designed to can actually compress gases, but only slightly. The rule is that below sub-sonic speeds the air intake MUST widen. So a narrow opening into a large space or a reverse funnel. It sounds backwards but this is how it works, as the air enters the larger area it slows down (think of traffic on the highway, when one person slow infront all the cars bunch up together increasing their densisty).

At supersonic speeds, the reverse is true. So there must be a narrowing of the intake track. However cars do not as rule travel at supersonic speeds. So therefore any Ram Air system that has a narrowing of the intake passage is actually REDUCING air intake pressure rather than increasing it.

This however, can have benefits of its own. The following is only supposition and I have no evidence as yet to back it up.

It is established that when you compress air, heat is produced as a by product. Hence FI cars often run intercoolers to lower the air intake temperatures. Reversly, if you reduce the pressure of a gas it should have a cooling affect. If you've ever used a CO2 air gun, you'll know that after a few shots the CO2 canister becomes cold, maybe even frosted. This is the cooling affect caused by the expansion or pressure reduction of the CO2 gas.

And as we all know colder air intake tempertures are good for power, as the charge density is increased. A few weeks back someone fitted a Ram Air kit to an Fbody, and they where recording lower than ambiant intake temperatures, the only theory I have come up with is what I have just described. Of course the possibility exists that they're test results where inaccurate.

There is one final, thing to consider and that's 'air box resonance'. This is a harmonic affect where the intake system resonates at a particular frequency promoting the draw of air. Much in the same way many musical instruments work. This harmonic balance will normally function at certain rpm's and not thru the entire range, if you can match the resonance with either PEAK torque or PEAK BHP then there will be a noticable increase.

If you can get your head round HOW and WHY the intake system works, I think you'll be able to answer your own question.

Jpr5690

iTrader: (13)

the fan is for cooling not to help out the ram air

damon_Z

How can your reply refute the evidence gathered by Install University? They performed two tests on the FTRA. First, they used Autotap and four runs--2 runs without the FTRA and 2 runs with the FTRA. They took the average numbers logged for both types of runs and discovered that the average intake temperature dropped by 11 degrees Farenheit and the Average Volumetric Efficiency (%) increased by 0.9%.

The second test consisted of the following (quoted from their article):

After many passes down the track testing out our kit, we sit down and averaged out the results. Our local track is an 1/8th mile track so we miss out on a full run down the quarter mile but we still showed nearly a tenth and one half mph (see Table 3). A one half mph gain in speed results in a nice 5 rear wheel horse power increase in the 1/8th. This should be greater for those running the quarter mile because the VE would increase even more as you achieve much higher speeds.

The only thing more important then being the fastest you can be at the drag strip, is getting an increase in gas mileage from a part that helps you go faster. After a day of driving on the interstate we ran the numbers on our gas receipts to see how much of an improvement would be had from the FTRA kit. With the FTRA kit blocked off and not in use we average 26.5 mpg. When the block off plate was removed and the front of the air box sealed off, we hit 28.1 mpg for a 5.7% increase in fuel economy. This alone will pay for the kit within 3,000 miles of driving with gas prices as high as they are these days.

From http://www.installuniversity.com/ins...sity/index.htm, click on Tech Articles, and find the FTRA article.

383ss

iTrader: (14)

that certainly doesn't prove that it 'rams' any air


that is the key statement and EXACTLY what 300bhp/ton stated.

damon_Z

Really, I thought he said:

What these 'cool air ducts' do is allow ambiant air to enter the intake. Remember it's not necesarily cold air, as there is no real cooling taking place, it is mearly outside air instead of heatsoaked air. So there is no real way of getting the air intake air temps below ambient.

And the article said:

the average intake temperature dropped by 11 degrees Farenheit

I'm confused. Please tell me how there is no ram air effect. Thanks in advance for the info.

waSStock

the drop was 11 degrees closer to ambient air temp, not 11 degrees below ambient

damon_Z

Now I get it. Thanks!

300bhp/ton

cheers, next time I'll post up the BIG print, picture edition for those that don't read things correctly.

damon_Z

That'll be nice.

Wnts2Go10O

iTrader: (12)

wouldnt it be almost physically impossible to drop the IAT's below ambient temps, especially with all that heat under the hood? i think the numbers would be flawed if it read the iats below ambient.. unless god was driving his beloved creation. one more question, is there a point at which air just simply cannot be compressed anymore?

300bhp/ton

Well I did convey my theory on how IAT's could drop, due to pressure decrease.

As for the limitations of compression, yes there must be a physical limit, but you'll not get anywhere near it, due to the limitations on how its compressed and where the compressed air is then stored. The intake system and engine would not be able to contain the pressure.

And besides, most V8's run quite sedate psi levels. 8-12psi which isn't all that high.

LSONE

iTrader: (1)

I was always under the impression that air didnt compress its sefl untill around 600mph? And even if it was compressing upon its self you wouldnt be dropping iat, they would be shooting up.

300bhp/ton

no it can be compressed at lower speeds, many of the WW2 fighters utilised it. From my reading (from an article about the Concorde Jet engines by their designer) it was claimed that signifcant gains can be seen at around 350mph.

600mph (altutude dependant) is getting rather close to the sound barrier, with things change quite a bit.