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Discussion Starter #1
Hi there.

I have a GTV with a split intake hose and a knackered airbox.

I'm trying to make my own intake piping now as I have a few bits of alum pipe, silicone hose and a few cone air filters in the garage.

My question is - how important are all those plastic box thingies (like plastic boxes attached to the intake piping at various points) and what will happen without them?

Anyone got any ideas? I've seen them on may cars and never understood them.

James
 

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One of the pipes looks like a crankcase breather and that can be fed into a small filter (£20) or an oil catch tank (£90?). Apart from that it's just the MAF housing you need to accomodate from what I can see. The important stuff must go into the plenuim because Autodeltas carbon pipe doesn't allow for the "boxes"
 

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Those things are resonators. They're only there to muffle the induction noise. You don't need them. Delete with confidence.
 

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Those things are resonators. They're only there to muffle the induction noise. You don't need them. Delete with confidence.
Not quite..

They are there as resonance chambers, which are meant to increase torque, and increase the volumetric efficiency of the engine by making the induction system act like a tuned pipe.

Rather like a carefully tuned exhaust can help the emptying of the cylinders a tuned intake can help with filling it.

If it was there just to reduce noise the chambers on the 2.5 and the 3.0 would be the same, but they are different sizes.


Yamaha pioneered a similar system (energy induction or YEIS) on their motorcycles.
 

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Discussion Starter #7
Thanks Symon.

Hmm.. I'd heard something about this. I imagine its pretty much the same as why the Ford V6's have a secondary set of inlets that open at a certain rpm. It acts like a 18valve car until about 3000rpm and then the inlets to the other inlet valves opens turning it into a 24valve. In fact, maybe thats to do with increasing the velocity of the inlet gases at low rpm and less to do with "tuning the intake" - but is prob to increase low rpm torque as well.

Hmmm. What to do....

James
 

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You may or may not notice a difference taking it of, it depends how sensitive you are to performance differences.

I removed the cone from the airbox on my 2.0TS 156 which is meant to do a similar thing. And it made it produce noticeably less torque.


The V6 has plenty anyway so the diffence would be quite as obvious.
 

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For the following reasons, the increased torque thing is an internet myth as far as I'm aware.

1. Mechanics with decades of experiencs have told me that they're only to reduce noise.
2. Alfa never put them on any model before the Euro noise regulations came in.
3. Autodelta and others make intake pipes for the GTV and GTA which completely do away with these chambers, with no documented loss of torque.
4. I've never seen them on any high-performance vehicle, which I would expect if they did indeed give more torque.

If the piping you're replacing them with is as big as or bigger diameter than the standard, you won't lose any torque by ditching the chambers.
 

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Discussion Starter #10
Cheers Mel and Symon for all your help.

I think I'm going to play it safe (for the time being at least) and put the original intake back together with a new filter. If I'm only going to see the same (or possibly/debatably) slightly worse performance than I might as well stay stock. It'll also be one less mod to declare to my insurers when I eventually get round to shopping round for quotes.

Right, where's my duct tape..? ;)

James
 

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Junk the lot!?

why not try junking the lot & see how it goes? The intake noise alone will make you think it's faster! You can re-use one of its intake pipes like in picture 1 or a shorter one & a smaller filter as in the other 2, don't forget a small filter on the breather. I've been warned about back pressure but they seem to run fine. If you don't like it put it back to standard.

Clive
 

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why not try junking the lot & see how it goes? The intake noise alone will make you think it's faster! You can re-use one of its intake pipes like in picture 1 or a shorter one & a smaller filter as in the other 2, don't forget a small filter on the breather. I've been warned about back pressure but they seem to run fine. If you don't like it put it back to standard.

Clive
Looks nice, but why would you go for a small filter? Smaller filter = less power, almost defeats the object and effort of changing the intake in the first place.

Jules.
 

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FYI the 156 2.5 V6 and the 3.2 GTA use almost identical intake system so I dont think you will gain much no matter what changes you make to the intake system.........I've tried quite a few on my 156 and didnt really feel any significant difference.

This is my current setup with mostly GTA parts and standard Alfa filter.
 
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Yamaha pioneered a similar system (energy induction or YEIS) on their motorcycles.
I remember having one of them! Never tried taking it off to see what happened though.

I have to agree with Symon that their may be more to these boxes than some people think. Out and out top end may not suffer but drivability might.

Goudy said he removed a resonator box and the car seemed quieter! So you have to wonder what its real purpose was :)
 

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FYI the 156 2.5 V6 and the 3.2 GTA use almost identical intake system so I dont think you will gain much no matter what changes you make to the intake system.
I don't think there's any suggestion that the piping alone will gain any power - you need a more efficient airbox for that.
 

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i thought it was illegal, to allow the breather to filter into the atmoshere now:confused:

god knows where i heard that:lol:
 

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I don't think there's any suggestion that the piping alone will gain any power - you need a more efficient airbox for that.
I would agree .........but dont tell autodelta that ;)

Autodelta’s dedication to constant innovative research combined with the passion for creativity, has developed this sport intake.

Carbon-fibre in construction it replaces the original restricted intake baffled pipe and instantly gives a cooler intake temperature together with an improved throttle response.

With an increase of 5-6bhp coupled with more torque you can understand why this is our top seller.

The kit comes complete with a dedicated sport air filter.
 

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The original GTV intake isn't that bad at all.

I read somewhere that the maximum power you could get by modifying it was only 1-2bhp

I bet by removing the resonator boxes you could loose some of the midrange therefore making the car feel faster at the top end though.
 

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The original GTV intake isn't that bad at all.

I read somewhere that the maximum power you could get by modifying it was only 1-2bhp
If all you're doing is replacing the piping between the airbox and the throttle body, that's almost certainly true. But the section from where it sucks air underneath the headlight to the airbox is pretty restrictive and there are decent gains to be had by replacing this with a cold air intake (including the airbox itself) to the "fake grille" under the foglight assembly.
 
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