Everything what works > RS4 B7

[sar]

june??? you work to hard rick
i thought rob must have had his fitted by now, tell him to get some vids done.

[MikeFish]

Needs a 1/4 mile slip.

/Sakimano

normally I would agree, but rick's chart is pretty compelling. I...I may be a buyer of this air ramming system.

Hey rick speaking of air ramming, did your exhaust arrive yet?

yes it did, looks like an awesome piece of kit, Rob (Cecilthesausage) has had his fitted and it sounds amazing, i dont have any spare time to get it fitted until the middle june unfortunately

You need to sort out your priorities!

[bam_bam]

Needs a 1/4 mile slip.

/Sakimano

normally I would agree, but rick's chart is pretty compelling. I...I may be a buyer of this air ramming system.

Hey rick speaking of air ramming, did your exhaust arrive yet?

You've changed. I don't know you anymore.

[Rick_RS4]

You need to sort out your priorities!

yes your right, that and the exhaust guy is busy when im free and vice versa.

[MikeFish]

Find a new guy!

[Speedr8]

the air mass is increased by pressure to + 40 g / s
But a big loss-free air filter is important!

Example:

The Audi R8 V10 GT sucks air through the rear door.
A Derating from 6 kW (source Audi) to the
Audi R8 V10 with side intake exists.

Is a power in the RS4 B7 by 15-20hp with RAM air,
but not measurable

Tom

[adsgreen]

So obviously they didn't change anything else on v10 gt to get 6kw more except add ram air scoops.
Don't be so ridiculous.

Ram air on a road car simply doesn't work at anything less than 100mph and even then not measurable.
Maf readings alone are not accurate - plenty of cases with tuned cars with similar maf readings having completely different performance changes. And sure as hell wouldn't be reproducible in a dyno.

If you want to prove ram air then put a pressure sensor on the intake manifold airbox.

However after studying airflow dynamics a long time ago, it's interesting just how air doesn't compress that easily. If you put a massive funnel on the front of the car and drive then 99% of the air will simply spill out the sides rather than be compressed and forced into the intake.

[Speedr8]

I know myself

Ram air on a road car simply doesn't work at anything less than 100mph and even then not measurable.

RAM air more power available is that you can see in the formula 1

There is in the www. information.

regards Tom

[Speedr8]

search > Formel1 V10 Hans Alten

find: http://www.heron.co.at/_lccms_/download ... wnload.htm

Tom

[adsgreen]

I know myself

Ram air on a road car simply doesn't work at anything less than 100mph and even then not measurable.

RAM air more power available is that you can see in the formula 1

There is in the www. information.

regards Tom

Which is why I clearly said "road car".
1) f1 cars generally operating between 80-200 mph.
2) the intake plenum is specifically designed with the very short distance between the intake and the manifold
3) roll bar scoop offers excellent un disturbed air unlike the side panels which are very turbulent

The fact you are comparing the BNS engine with a formula one engine just adds to the laugh-ability stakes.

[adsgreen]

If we are posting random internet links
http://www.formula1-dictionary.net/engi ... ntake.html

As said here, the engine is consuming air far faster than even a formula one car can 'ram' it in.

Consider the old 2.4 v8s. At 100% ve it would be consuming 2.4 x 0.5 x18'000 = 21,600 litres of air.
Due to the designs it's actual ve is way higher so how much do you think this is due to ram air?
Sure, it will be a factor but even on purpose built top flight engines it's tiny so a road car? Pointless.

[Rick_RS4]

Adsgreen

question, when i had my standard airbox blocked off wing vent and had a 4'' cai straight in to the airbox , (airtight bar the inlet and outlet) it felt more torque'y but when i accelerated to 3 figures it threw codes like i was getting too much air flow, is this not ''ram air''?

this isnt a dispute just these past few posts reminded me of this so thought id ask.

[Speedr8]

It is pointless to discuss here the adsgreen know anything better.

Here in Germany we may drive as fast as the engine power has
and the RAM air is very effective for us.

Tom

[adsgreen]

Adsgreen

question, when i had my standard airbox blocked off wing vent and had a 4'' cai straight in to the airbox , (airtight bar the inlet and outlet) it felt more torque'y but when i accelerated to 3 figures it threw codes like i was getting too much air flow, is this not ''ram air''?

this isnt a dispute just these past few posts reminded me of this so thought id ask.

Tbh, it's difficult without the codes. The main problem is that the maf sensor is expecting a certain intake profile and it's easy to fool it. After all it's only a heated wire set at a fixed temperature and an air temp sensor. Using the temp of the air and measuring how much the air cools the wire it can make a pretty good estimate as to the mass of air flowing past. But this require some assumptions that can go wrong. If the air the maf is reporting doesn't correspond with the amount of O2 in the exhaust after setting what should be the ideal feeling mixture then you will get lean/rich errors.

As for the 4" cai... Well deep breathe and we'll dive into some Arthur.
A 4.2l 4 stroke engine running at 8000 rpm will at 100% volumetric efficiency draw in
4.2 x 8000 /60 / 2 or 280 litres of air (also express able as 0.280 m3)

If the car is at 100mph then that is approx 45m/s.
So assuming the intake is perfect then the required 0.280m3 of air per second travelling at 45m/s only requires an opening cross sectional area of 0.280 / 45 or 62.2 cm2

A 4" diameter cylinder is a radius of 5.08cm so it's cross sectional area is simply pi x 5.08^2 or approx 81cm2

So cool - the tube is much bigger than what we need.
At 45 m/s we will have 45 x 0.0081 = or 0.365 m3 of air

Now the engine will consume its 0.280m3 of air and the remainder will act to compress the remaining air.
One way of representing this is that if you have 0.365 m3 of air travelling at 45m/s but consume 0.280 then the remaining air will be in effect compressed with the remaining speed.
1 - (0.280 / 0.365) = 0.239 or 23.9%.
Ie the air is effectively moving at 0.239 x 45 or 10.7 m/s

There are a couple ways to work out how much air compresses when moving (dynamic pressure)
A quick one is q = 1/2 p v^2
Where q is pressure, p is the density and v velocity.
At sea level at 20c Air is about 1.2 kg / m3 so:
q = 1/2 x 1.2 x 10.7^2
= 68.6 pascals
Or in other words this is an increase in pressure of about 0.01 psi.

Let's hit 200mph
The air is being compressed at a speed of about 28 m/s.
End result is 470 pascals or 0.07 psi.

The issue is simply the intake area - in order to take advantage of ram air effects you need a lot more than just a pipe facing the direction of travel. Think the big bonnet scoops of some cars. Going back to f1 their intakes are something like 200cm2 plus. There needs to be a lot of left over after then engine has drawn it into the cylinder and a 4" tube simply doesn't scoop enough.

The main reason I've found (and this is true with me) is that it's far too easy to link 'sounds' faster with 'feeling' faster. A nice intake with a decent intake burble sounds lush and at full power the reduced silencing just sounds too good to be anything other than it must be faster. Not saying this is the case but even with stock rs4's people do go on about the airbox flap opening...
One other thing to consider is that the wheel arch area is actually a high pressure zone - blocking it may actually be hurting air getting in. Also on the rs4 you want another entry point for air with a cai - if the cai gets submerged with water then the air will just be drawn in from the other vents. If they are blocked then it'll suck up water (potentially).

Of course the above is very simplified - it's missing other parts on induction tuning. When a valve closes the air that was rushing headlong into the cylinder suddenly stops. This in itself has a degree of compression but it also causes a shock wave to bounce off the valve and back up the intake. If you can time the return of this pulse back with the opening of the valves then this pressure wave has a reasonable positive effect. (There's also a supercharger design based solely on this principle).

You can get ram air to work but on its own and retro fitting to a generic design isn't going to see massive gains. Sure it won't hurt and 'why not' but it's not a one hit magic golden bullet and you need to the whole thing redone from start to finish. The rs4 intake is already compromised to get under the bonnet but does a reasonable job (consider most supercharged setups are running stock airbox system - it's not actually that bad).

Wow. Longer than I thought. If you read this far then you have earnt a beer I say

[bam_bam]

Some of the best Arthur I've seen since, well, since Arthur used to frequent the forum. He's changed, Merc lover.
He says, drinking a beer.