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Discussion Starter · #1 ·
On most of my old cars I've took it upon myself to fabricate my own versions of common induction systems Whether they be enclosed or open. Mainly because I don;t want to pay the extortinate price for a filter and some ally tube and also for a sense of achievment. However I've not fully research one part of these systems that could make a hell of a difference to torque and power delivery. This part is the length of induction tract. Has anyone ever done any experiments in shortening or lengthening the induction tract and have results of power/torque delivery in this situation?

I have a few ideas in mind for the 5 and want to try them out. One of which is to have a very short induction tract but I don't know if this would have a detrimental effect on the way the car runs. Any info would be appreciated.
 

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Let me know how you get on with this. I wanted to design a duct which allows the filter to be closer to the front grill (on a mk1) to allow it to get to the cooler air. I understand it can be dangerous driving in water like this but I wouldnt be daft enough to go driving through big puddles. This would be an open cone set up.

Another option would be to mimic the design of a DIA (made by bcm). Have a short duct from the throttle body/afm sensory to a closed filter and direct some piping to the lower section. This would allow the filter to be placed right into the engine bay. Probably gain better torque this way being an enclose filter.

I have currently just got a K&N pannel filter and am going to drill my airbox for noise.
 

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i know with 2 strokes the longer the induction the more torque less power and with a shorter induction you get a quicker responce and more power but less torque. should think it would be the same on a 4 stroke.
 

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i know with 2 strokes the longer the induction the more torque less power and with a shorter induction you get a quicker responce and more power but less torque. should think it would be the same on a 4 stroke.
Something like that.
A short system offers the least resistance to airflow. Thus, at really high revs where peak bhp is generally recorded, pleanty of air can get in.

A longer system has more air in it. air has a weight, and as such it can act as a hammer. As your piston whips down the bore the air within the intake hits its peak speed. Then as the piston passes bdc its no longer drawing in air, but the air within the inlet is still travelling at speed. Pushing air into the cylinder even after the piston stops sucking. Filling your cylinder beyond atmospheric pressure is quite possible.

So, for a good fill at lower revs the longer systems are king. Tuning intakes for peak torque or widening the peak torque band is quite normal. You can even help a system breath at a point it would otherwise struggle. Meanwhile a very short system offers no gain towards torque, but allows each stroke to fill better at very high revs where peak bhp matters.

As an example, motorbikes ofton use throttle bodys. This means while there revving there nuts off they get a good fill. They make great bhp. However bikes just dont have torque. They dont even do low revs. so much so that bike bodys open up very quickly compaired to car ones as there is no point regulating low revs stuff. The bike just cant do it.
 

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Heres mine I did last week.

Easy job and cost less than ?30

Ebay filter, ali tube and some silicone hoses

Lookin great mate. i remember the first time you took me out in here yearsssss ago.
Made me buy the FM2 after that
 

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Interesting subject this as I also want to fabricate some sort of air induction box for my car but mostly to keep the hot exhaust air away from the filter. I must admit I don't fully understand the mechanics of it all but I get the general idea I think. What about these ram pipe intakes? How effective is ramming air into the system via a front mounted funnel type affair? Surely this is how SC's and Turbo's work so must be good? In theory the faster you go the greater the ram effect right?
 

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Thanks for all your input. Makes interesting reading. So short intake equals better BHP but lower torque. Longer intake more torque but may have an adverse effect on bhp.

I was thinking of fabricating something along the lines of MX5 Dan with Silicon hosing and aly tubing. Readily available on e-bay. Just got to figure out diameter and lengths. I found this whic would help with the bit nearest the throttle body and give the idle loop back feed.
Universal Ally air breather pipe
Of course with the above fitted the cam cover breather would need to be removed and a small filter fitted instead.

Dan, what size pipe did you use? and what size is the silicon hosing from the throttle body?
 

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Don't forget about the weird shape of the intake track of the 1.6.

If I recall correctly it has a reserve of air that somehow flattens out the mid range torque, gets a dip without it apparently.

Ideally try to copy an ARC chamber type system. I think the Idea being that the intake track is short but with a large volume and very little restriction.
 

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Discussion Starter · #11 ·
All I can see in the 1.6 trackt is a resonance box that so many other systems have to cut the induction noise down. Can't see any reverse flow at all. Anyone else got pics or details of this system on a 1.6?
 
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