"modded" my air intake :)

[NUTTTR]

I decided tonight i'd rip out the air intake tube (above the radiator) from the car and take a look at what all that extra crap on teh back of it was.... Firstly, i can recommend to everyone who thinks that taking it out is a good idea, it's not...... it's an absolute bitch to get out... I can almost guarantee you won't get it back in without modding it first....

There's 2 chambers on the "back" of it that obviously are used to prevent resonation or something, because otherwise, they serve no use at all, so i chopped them off :) Then i was left with 2 big holes, you have to be creative, but i got a piece of plastic off something else and cut off a piece off the bits i'd cut off the air intake and pop-riveted these over the holes, then silasticed them up to seal it from hot air, etc..... Putting back in like this (all the back bits removed) is still bloody hard, but do-able!! i will report tomorrow on any difference in sound/driving....... i'd expect a sound difference, but doubt a performance one.... now i can fit my hand between the radiator and the engine!!! I don't know why they included those pieces!!

On second notes, the airbox in the 2.2L doesn't allow the car to use the surface area of the filter, the "bulges" in the bottom of the airbox block 75% of the surface area!!!! Might have to work on that :)
Aaron

[macquered]

Yeah, those engineers that spend ages working on these things don't know shit. They must have had some excess plastic that they needed to use up. Chop them off.

[NUTTTR]

Bah :P
They are there for simply resonance removal.... Without them, you'd expect more intake noise and also less turbulance....... it looks just like the ones regal sells now :) They dont' have any, they are aftermarket, and work well!
Aaron

[macquered]

Yay for backyard engineering!

[DoomTrooper]

i just have sum PVC pipeing
still get not resonating noise so i don't know why the original tube had all those funny knobs and stuff

[Anonymous]

Those tubes are there for a reason.

Hot4's investigated them a while back (they asked the same question as you guys), and found that by removing them, they lost power.

macquered was onto somthing in his first reply :P

[DoomTrooper]

maybe if he wrote (sarcasim) ppl might understand him better cause there is no tone of voice when u type a msg, i think i'll stick with my big tube as opposed to pretty much the stoc straw with some pockets in it

[macquered]

....and why is that?

[DoomTrooper]

because the larger the tube, the less of a funneling effect it has and hence the faster the air can flow through,

[macquered]

Actually it is the other way around. If you have a given amount of air going through a smaller diameter pipe it will flow faster, which is what the manufacturer tries to achieve. Maintaining air velocity is an important factor for engine tuning.

[DoomTrooper]

I understand that a smaller pipe makes the air move faster, this is proven by the fact that if u blow through a cardboard tube or a straw, the air comming out of the straw is faster, but if u turn that around and now try and suck through the straw and the cardboard tube, which one will be easier to suck through, the cardboard tube, now if u suck hard enough then the air will travel just as fast through the cardboard tube as it would through the straw except your sucking alot more air, however if u applied this same amount of suction to the straw you wouldn't breathe nearlly as easily, you would recive less air, hence why a larger tube in and out of the engine helps airflow

[DoomTrooper]

i should mention of cource there is an upper limit to the size of the tube, when the engine doesn't suck hard enough to create a fast enough flow through such a large pipeing and of cource the air will get hotter etc, but since my tube is the same size as the pipe that goes actually into the airbox, just that i continue that size the whole way to the bumper instead of it geting smaller like the stock one

[macquered]

You are making a few basic errors in your assumptions. Of course there is a compromise and thats why there is a stack of engineering in these setups. There is a hell of a lot more science in a modern inlet tract than just pipe diameter and you'd need a degree in fluid dynamics to understand and therefore improve it, hence my backyard engineering call.

[DoomTrooper]

funny thing is that i am an engineer and i do study fluid mechanics, just trying to provide an example ppl can identify with

[macquered]

So then you should be able to tell me exactly how much restriction the standard setup is imposing on the motor.

An engineer at age 20? You must be pretty damn smart.

[DoomTrooper]

well buy me a wind tunnel and we shall test away won't we,
ok so i may have overexaggerated a little, :) i'm a member of the AIE, but i have yet to finish my degree but i am studying fluid mechanics this semester so it is pretty much right up my alley, but i'm not saying your wrong but the only point you've made is that because it was designed along with the car therefore it must be right, but you see that when they design a car they factor in more than just performance, also fuel economy and durability, whilst it maybe more efficient to have a bigger tube it may also effect fuel economy or make it wear faster, so to compromise they choose a happy medium, the springs that came with my car arn't as good as the ones that i put in, but holden would never use them as stock as they're too harsh for the average go from A to B commuter

[macquered]

I'm not saying you're wrong either but one trend I just can't understand is saying that one solution is better than X without actually measuring X in the first place. People say 'oh my derestricted airbox is better because it flows more'. How the hell can you tell? One bright spark here told me he could *hear* more air going in. Well I'll be damned if that is a recognised measure of air flow.

I don't see how durability and fuel efficiency come into it either. Durability? I've never seen durability of an air intake affect flow. Fuel efficiency is measured by use of fuel. How does a restrictive intake affect this?

[DoomTrooper]

surely u know that if u put more air in then the ecu will put more fuel in to keep to the ratio?
durability of the engine as a complete unit, not just the tubeing

[NUTTTR]

Well, the actual pipe itself (hence why in a few weeks i'm going to get a bigger pipe made up) has almost 20% less surface area (at it's smallest point) than the throttle body....
That's part of the reason, to smooth the airflow and stop the turbulence.... It (to my ears) is now louder... but it might not be, i have an spl meter but didn't measure it before i changed it....
Aaron

[macquered]

surely u know that if u put more air in then the ecu will put more fuel in to keep to the ratio?

Yes of course. So how does that make it less or more efficient?

In a nutshell, there are many other factors that determine fuel efficiency and I would be surprised if the intake is starving the engine of air as you are suggesting.

I think you'll find that a lot of modern naturally aspirated intakes actually generate positive pressure in the manifold, giving the engine very impressive volumetric efficiency. Why do people think they can better that by cutting off bits and pieces in the inlet?

[astra_city]

Well all I know is, that ever since installing my CDA my car is definitely more responsive and also has more kick to it as well - I have the chance to compare whenever I want to my mums standard Astra :P

Also, speaking of modifications, engineers do a lot of things that can be improved upon. Exhausts are a prime example - yes the manufacturer puts effort into achieving the best balance of power and noise, but it is always a compromise, as they have to sell their cars to a large demographic. I guess there's arguments for and against both

[DoomTrooper]

the stock tube, starts smaller than it ends, therefore the air is more restricted at the entrance to the pipe, i merely made mine straighter and without any size changes hence a faster less restrictive pipe
not to mention the fact that pvc is less heat conductive than the stock pipe therefore the air entering the engine is marginally cooler,

from what i've read the air intake does starve the engine at higher rpm, and i personally have felt the diff between a pod and the stock box and tube and the engine is starved, the fact is that by dropping half a litre per 100km's on the fuel efficiency by sacrificing a few kw is going to improve sales as the majority of astra owners care more about their fuel efficiency than how much power the car has

the car is designed to make money not be efficient

i never once said that cutting it was the way to go

[NUTTTR]

Partially the reason i did cut the bits off was how hot those parts got, they basically sit on the radiator!!! All the heat used to come mainly from those bits into the air intake... now there's hardly any heat compared to before, the whole intake tube is cooler.....

[macquered]

from what i've read the air intake does starve the engine at higher rpm

Where did you read this?

[dan_kind]

not that i know much about fluid dynamics, engineering, etc...however, from my basic knowledge of workings the following are the assumptions i have made;

1. The 'intake' pipe design would create a substantial amount of 'noise'. therefore, the additional chambers, placed where they are would reduce this.
2. The 'intake' pipe design would also reduce strange occurances with air pressure/vacuum *being as though it is exposed to the front of the vehicle, where the air begins (i beleive it just in front) to splsit*
3. I have had a fluke multimeter with a thermo probe stuck smack in the center of the intermediate pipe to the air box, and while travelling, the air is +1C of ambient air.
4. I have also had the same thermo probe in the air box with and without the front 'intake' and found that even while at high way speeds, constant temperatures of +5 to +10 were recorded. In the m5 tunnel a air box temperature of 89degrees was recorded. After removing the air box, and located a pod as low as i could, with the original 'intake' piping left in place, the maximum in the m5 tunnel was 55 (-40 on engine bay temp), while cruising sees the in thermo probe i placed just above the butterfly reading +2, so for my vehicle at least, there is enough air flow to permit a pod filter without temperature issues...
5. The box design is again to reduce intake manifold noise, as much as it is designed to create flow so as to cover most of the air filter...removing the pipes on either side tends to have the air flow through the center of filter...
6. I would imagine the flow characteristics of the box are so as to allow maximum power while the following design considerations are taken into account;
- Maximum air flow
- Longest life of filter
- Quietest operation of intake system
- Coolest air.
7. 'derestricting' air boxes and/or changing intake design cant make a huge difference in my opinion.
8. The ECU will compensate for changes in air flow/temperature via the mass air flow sensor or 'hot wire', however these changes will mostly save you from any sort of major catastrophe (along with the knock sensor)..

[VF]

i have done a similar thing to my astra 1.8 5door.

i inserted a PVC section onto the air box and then fed a black plastic agri pipe to wards the bottom of the bumper.

The car's acceleration is great when temperatures drop below 15 degrees. Fuel efficiency is good too.

This is the first modificaton i did and I stronlgy recommend it. vehicle manufaturers have been restricting air flow on 4 culinders for years.