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The Scarlet one returns...
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Discussion Starter · #1 · (Edited)
"What's that then?" i hear you ask, well for some time now Rob Bell (from the MG Cars forum) and i have been toying with designing and manufacturing our own cold air box, similar in concept to the ITG Maxogen.

"Why do this?" is the next question. The ITG is very expensive, we are talking nearly £300.00 here and most people have already purchased a K+N 57i. The ITG box is specifically designed for thier filter so a K+N or a Piper X wont fit. Rob has been playing with heat shields and a Rover 820i air box and i have been designing one that will cater for any cone filter and any throttle body / inlet plenum arrangement.

"What are the benefits?" Well, the reason the K+N 57i produces such a large power benefit is because the standard air intake system on the MGF suffers from the mid engine location and an excessively convoluted intake route. The K+N 57i, as well as being a more efficient filter medium, has a pair of cold air pipes that are mounted, forward facing on the underside of the car. This provides a cold air feed (cold air being denser and thus contains more oxygen), with a 'ram air' effect directly to the filter. This set up has been independantly proven to produce +8bhp on a 1.8 MPi and +15bhp on a VVC. BUT! the filter is mounted at the top of the engine bay, surrounded by hot air (heated by the engine), so a large part of the cold air is diluted by the ambient temperature of the air in the engine bay. The ITG system isolates the filter from this ambient air and has a dedicated cold air feed from the side air intake, thus overcoming the shorcomings of the K+N set up.

So, the ideal would be a fully enclosed air box, with it's own dedicated cold air supply that could accomodate a K+N, Piper X or ITG filter and cope with the various throttle body / inlet plenum variations.

I give you, the Generic Cold Air Induction Chamber...

>> http://www.mgfcar.de/airfilter/Andrew_Airbox1.jpg <<

This is the latest design, and it has been passed to a manufacturer for cost analysis and the production of a prototype, i am hoping to (all being well) get these made up and undercut ITG by a big margin - the main benefit is of course that if you already have a K+N or Piper X you can make use of the chamber and maximise the performance of the filter.
 

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MGF MoD
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57 Posts
Hi,

had looked up for the OEM of the flexible hose used at the Elise on the other thread.


OEM is BONRATH located in D. They offer kits for several cars
http://www.bonrath.com/e/pr.htm
http://www.bonrath.com/

I think the short reduction piece you may need should be availiable independant as well. TBA.

Should I inquire at the german company ? ;)
If so then at first suggest the inlet diameter to your box. The other is clear with 70mm. So 80mm or what on the air box side ?
Length is for sure almost the same with app 40 to 50 mm only.
 

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The Scarlet one returns...
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1,040 Posts
Discussion Starter · #3 ·
Hi DK :)

Rob is talking about a flexible hose to take up differential movement between the box and the TB, bearing in mind that one is attached to the engine and the other is fixed to the original airbox bracket. The 'rubber ring' in the new air box is intended to provide a seal around the air filter pipe, allow for different TB/plenum configurations AND absorb any differential movement.

At some point in the future i will need to get these, and the two pipes sourced from somewhere and Bonrath seem to be able to provide these sorts of items. However, i need to get hold of the prototype box and fit it to see if it works as intended. If this is OK (and i'm only expecting minor amendments - maybe make it a little smaller to ease fitment), then i shall need to get it 'productionised' and this will involve sourcing the rubber components.
 

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MGF and ZTT pilot :)
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863 Posts
Nice work Andy :)

Been thinking about this airbox problem for some time - and primarily how to make it cheap!

Options so far investigated include a heat shield (no more than a length of 220 mm diameter ali chimney ducting), the 'flobba-dob' flower pot airbox (thanks to the Lotus Elise BBS for that one) through the Rover 820 airbox (current project, as seen on http://www.mgf.4mg.com/new_airbox.htm) to the airbox concept that I passed on to Andy.

The dimentions of Andy's box were derived from the heat shield and the flowerpot airbox mods. The 'interesting' bit on the prototype that Andy has worked on is on the inlet side. The idea here is to gradually increase the diameter of the inlet path so as to accelerate the inlet airflow. In doing so, one creates a low pressure wave that effectively acts as a vacuum to suck air in - a ram-air effect. This will work well at higher engine speeds. The difficulty is knowing the rate at which the inlet diameter should increase without causing turbulent airflow (which would ruin the whole ram-air effect we are striving to create).

Anyone have the necessary fluid dynamic modelling software? ;)

You never know, someone might have something suitable! :D
 

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The Scarlet one returns...
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1,040 Posts
Discussion Starter · #5 ·
Interestingly, the ITG box is 'waisted' at the start of the inlet cone. It is a 100mm diameter inlet pipe, then it narrows briefly to approx 75mm dia. From here it expands to around 170mm. My design (primarily for manufacturing reasons) does not have this waist - at the moment i am not sure what sort of effect this will have on the air flow characteristics, we are trying to achive an acceleration of air flow which remains laminar in nature; a very tricky task. Moving air tends to become turbulent as speed increases. I suspect that the waist creates a 'backlog' of air in the induction pipe, thus ensuring that the air entering the cold air box does so at a uniform speed, enabling the rate of acceleration to be calculated as a constant and thus producing a design with a constant laminar flow of air to the filter. My design is unlikely to have this characteristic and may be more or less efficient at different road speeds - however, until this is tested it is all theory.:)
 

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MGF and ZTT pilot :)
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863 Posts
We are being very conservative with the change of inlet diameter to be honest, especially with the length of the inlet 'trumpet' I figured when thinking about these ideas originally that being conservative was probably better than being too aggressive- whilst we may miss the 'optimum' shape of the airbox, at least we will not encounter 'de-lamination' of the intake air flow which IMO would be diasterous.

Not sure about your 'backlog' theory. My take on this is that they've used 100 mm duct to ensure that there is no restriction to airflow BEFORE the airbox. So what they have there is a air supply system that has plenty of reserve capacity before the airbox, and effectively, the inlet might just as well be sitting in the open, free air.

Very interested to read your measurement of the ID of the ITG airbox inlet. 75 mm is almost identical to that used by the Rover airbox I have (74 mm). This maybe very important: if the inlet to the airbox is too large, then we'll not get any significant acceleration of airflow... The box will still work, but maybe not as well as the ITG.

At the end of the day, I reckon you are spot on Andy - the proof will be in the comparison of the two designs. :)
 

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The Scarlet one returns...
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1,040 Posts
Discussion Starter · #7 ·
My thoughts on the size of the inlet are that the acceleration of air is caused by the difference in size between the narrow entrance and the wider exit of the cone. As i mentioned before the ITG one is 'waisted' at the entry point and then is a constant splay to the air box end. I have tried to keep the ratio between the inlet diameter and the airbox (exit) diameter the same as the ITG, but in my case, because i do not have the waist (oi don't get personal!), my inlet and exit diameters are significantly wider allowing more air into the chamber.
 

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MGF and ZTT pilot :)
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863 Posts
That's true, but because the inlet diameter of the box that you are planning to make is 100 mm, the inlet air will be moving more slowly than the ITG with a 74 mm inlet throat at any given engine speed.

I'm no expert in the field of fluid dynamics, so I have no idea whether this is a good thing or bad. I think that practical experience will be the decider on this! ;)

BTW I trial fitted the Rover 820 airbox over the weekend. It fitted as though it was always supposed to fit there!!! :) Now all I really need is a suitable length of flexible induction tubing... :) :) (Oh and a 74 to 100 mm adapter for the inlet duct)
 
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