Air intake mk?

[GERFIX]

Originally Posted by baxlin

Colin, ask Mrs G, isn't that to REDUCE suction, for use on curtains and the like? Sort of endorses my point, maybe?

Malcolm

It can't reduce suction, surely. If air is being drawn from the original opening of the air intake then it won't exit through the extra opening. If you put your hand over the extra opening on a hoover it's still sucking, not blowing. So to speak. The extra hole allows more air to be drawn in in the case of the main one being blocked or having the suction severely restricted.

I may be wrong though, as I am no expert on car or vacuum induction systems.

[baxlin]

Originally Posted by GERFIX

I may be wrong though, as I am no expert on car or vacuum induction systems.

Nor me, Colin, but I'm fairly sure about the reason for the adjustment on the Vacuum cleaner hose. Perhaps it wasn't such a good comparison to have made in respect of the air intake.

I must admit I made the initial comment about losing airflow half in jest, but I'm not so sure now. Proof of the pudding will be in the eating, no doubt.

Malcolm

[GERFIX]

Originally Posted by baxlin

Nor me, Colin, but I'm fairly sure about the reason for the adjustment on the Vacuum cleaner hose. Perhaps it wasn't such a good comparison to have made in respect of the air intake.

I must admit I made the initial comment about losing airflow half in jest, but I'm not so sure now. Proof of the pudding will be in the eating, no doubt.

Malcolm

I'm sticking by my last statement Malcolm, expert or not. As you quite rightly say though, the proof of the pudding etc.

What we need are some induction experts!!

[CDTi]

Originally Posted by GERFIX

... the proof of the pudding etc.

What we need are some induction experts!!

The pudding is eaten, but the jury is out on the proof . After a 120 mile trip today, I'm unsure whether this made any great difference or not.

There in no great difference at all that I can see at lower speeds. At higher speeds/revs, I think the engine response is somewhat improved.

I suppose this does make sense in that the higher revs need more air and it is now available to the engine.

Maybe 120 miles is too short for the ECU to have "learned" that it can breathe easier?

[desperado]

do it after looking at my air intake .i don't think rover could have made it any smaller if they had employed dwarfs

[Kearton]

Originally Posted by desperado

do it after looking at my air intake. i don't think rover could have made it any smaller if they had employed dwarfs

I think the restrictiveness of the intake was BMW's doing so it suited the original 116 hp model to ensure it couldn't embarrass any BMWs.

Regarding the physics of induction:-
1) Air naturally flows towards a lower pressure area, i.e. from the atmosphere to the air box who see pressure has been lowered by the engine & turbo sucking it in.
2) the speed (rate) at which it will do this depends on
a) the size (minimum cross-sectional area) of the opening / pipe, and
b) the flow characteristics of that pipe due to its shape & length. A smooth, circular cross-section pipe will have the best flow. Bends and intrusions, e.g. the bellows section of the intake, will reduce the flow.
In a smooth pipe, the pressure drop along its length will be the minimum possible.

So,
- cutting extra holes in the front will improve (2a), but the limiting factor is the size of the hole into the air filter box.
- cutting off or replacing the bellows section with a smooth telescopic section would help (2b).

Regarding water ingress, there is already a water deflector under the bonnet slam panel which should be sufficient. I've read that BMW were very fussy about ensuring it met their water ingress standards and as a consequence the 75 / ZT is better in that respect than the 3-series. However, it too restricts air influx. (There has been some debate as to whether this was fitted to all diesel models.)

I hope this helps.

Kearton

[Kearton]

Originally Posted by Kearton

I think the restrictiveness of the intake was BMW's doing so it suited the original 116 hp model to ensure it couldn't embarrass any BMWs.

Regarding the physics of induction:-
1) Air naturally flows towards a lower pressure area, i.e. from the atmosphere to the air box who see pressure has been lowered by the engine & turbo sucking it in.
2) the speed (rate) at which it will do this depends on
a) the size (minimum cross-sectional area) of the opening / pipe, and
b) the flow characteristics of that pipe due to its shape & length. A smooth, circular cross-section pipe will have the best flow. Bends and intrusions, e.g. the bellows section of the intake, will reduce the flow.
In a smooth pipe, the pressure drop along its length will be the minimum possible.

So,
- cutting extra holes in the front will improve (2a), but the limiting factor is the size of the hole into the air filter box.
- cutting off or replacing the bellows section with a smooth telescopic section would help (2b).

Regarding water ingress, there is already a water deflector under the bonnet slam panel which should be sufficient. I've read that BMW were very fussy about ensuring it met their water ingress standards and as a consequence the 75 / ZT is better in that respect than the 3-series. However, it too restricts air influx. (There has been some debate as to whether this was fitted to all diesel models.)

I hope this helps.

Kearton

P.S. In the vacuum cleaner analogy, the suction (pressure drop outside to inside the pipe) for the normal intake opening is reduced, but it is the air flow rate that we are interested in.
As GERFIX says, the secondary intake allows extra air in and will do so even if the main hole is not stuffed full of your best lounge curtains.
The more air that can be supplied to an engine, the more potential there is for producing power. Normally aspirated engines suck air in whilst turbo or supercharged engines push it in, which is why they produce more power per litre.
In physics mode, if we double the cross-section of the inlet pipe, the pressure drop (suction at the inlet) will be less, as will the air speed, but the air-flow rate will be higher.
Another factor designers have to consider is that at low engine speeds, the pressure difference, and hence the air speed, is lower and makes filling the cylinders harder (teh degree depends on the proportions). This is why engines with big carburettors / intake diameters can produce lots of power at high speed, but run poorly at low speed - e.g. racing engines.

Kearton

[desperado]

[QUOTE=Kearton;163057]I think the restrictiveness of the intake was BMW's doing so it suited the original 116 hp model to ensure it couldn't embarrass any BMWs.

yes i've heard that to ,more so with the mgf, didn't want it better than the z3. vw seemed to manage with all their brands ,thanks bmw ,rover may still be producing cars if you weren't so paranoded.rant over thank you dan

[GERFIX]

There we go, simple as that. Ouch, my head hurts.

Thanks for that Kearton, it is very useful to have these things explained properly.

[CDTi]

Originally Posted by GERFIX

There we go, simple as that. Ouch, my head hurts.

Thanks for that Kearton, it is very useful to have these things explained properly.

Thanks Kearton, that does make things clearer.