I agree completely with this, and on these system they start very large in diameter and gradually get smaller squashing the air in. However on the six the initial intake is large at 72mm it then does down to around 62mm entering the airbox. It's then back out at 72mm and goes down to 60mm on the bend and then back out to 72mm for the entry into the AFM.

I ideally would have liked to have done and 80mm down to 72mm, but i would have had to use lots of samco and reducers. So in the end i went with a 72mm Alumnium pipe with one 70 degree bend to prevent water ingress after leaving the filter and then a 90 degree samco bend which keeps The same diameter all the way through. Obviously because the filter has access to so much more air rather than being restricted by the intake pipe (72mm) on the standard system their is a ram effect, but certainly there is potential for doing more than i did.

Here is an article that i wrote for the club magasine.

James

The colder the better

By James Sohl

 

 

This story really began about a year ago when I attended a rolling road day with my 635 CSi. What a great day I had seeing all these Bavarian motors having their necks wrung to get that last possible BHP out of them. On this day I noticed a couple of things. Firstly there were a number of cars that had modifications. Secondly some of those modifications made the car worse than standard and thirdly that my own car was running rich and got richer as the revs went up.

 

I asked lots of questions on this day to the engineer controlling the rolling road, other owners who had made good results and some of the poor souls who were disappointed. My own score was not at all bad at 207bhp at 5100rpm and 247lbs/ft or torque at 2200rpm. That is on a 20-year-old M30 engine that was one service light away from a service and had covered 123,000 miles. Factory figures indicate 218bhp at 5600rpm and 220lbs/ft of torque. (Rolling Road Photo)

 

The biggest thing I came away with from the day was that if I could get a better cold air feed to the engine this would make my car run a little leaner and this would equate to a better breathing, more powerful engine. So I attended another rolling road day and took mental notes on different induction systems. There seemed to be a trend in that many cars were running conical filters and the ones that made a difference were heat shielded while the ones that weren’t generally resulted in the car having less power than standard.

 

I now started looking at the M30’s system and the problem was almost immediately apparent. The large BMW air box (that has a cold air feed incidentally) sat almost touching the exhaust manifold and the size of induction tubes varied from 62mm to 72mm and back down to 62mm again before going into a 72mm opening in the air flow meter. This constantly changing tube thickness slowed the air down and so before it had been sucked into my engine it would be significantly hotter. This all made sense as on hot days in the summer that car had a tendency to be very sluggish after a short wait in traffic.  (Engine Photo)  

 

I read as much information as I could find and looked for an off the shelf solution for the 635. Unfortunately no system was out there that looked like it dealt with the problem of excess heat. Green cotton made a system, but there was no heat shield. So I bit the bullet and started to design my own. My primary thought was to try and get a conical filter located as far away from the heat sources of the exhaust manifold and radiator as I could. I then needed to have a conical filter that would fit the desired space. I worked this out by making cardboard cut outs until I had the perfect size and then ordered the filter. Another consideration was that I had to design the pipe work so that the car was protected as much as possible from sucking in water that would kill the engine. The last consideration was to design a heat shield in such a manner that the filter could be removed just as easily as the factory system for routine servicing. (Mock Up Photo)

 

From the first mock up a number of slight adjustments were made until I was at a point where construction could begin. My first fabricator, who shall remain nameless, wasted about three months of my time by not keeping appointments we had made. So I went to ALTiSS Engineering who specialise in bespoke aluminium, titanium and stainless steel work. On a trip up north I dropped in on Nigel the owner who measured up and began making the induction piping and heat shield. On my way down south three days later he had completed the work. The fitting, however, was not quite as simple as the heat shield was out. This was largely as a result of making the mock up out of cardboard and cardboard flexes and aluminium does not. So another mock up was made and Nigel sent me the completed article in the post. The next time I went up north the final adjustments were made and the installation was complete. In total from conception to a finished article it took 6 months. The components needed included the pipe work, a 90-degree silicon bend, a conical filter element, neoprene insulation and the heat shield. (Finished Article Photo)

 

Overall the car feels a little more responsive but I need to wait for a dyno run to be completed before I can give you actual figures to show any improvements in bhp or torque. Noise-wise on mild throttle and cruising it’s no louder then standard, but when the loud pedal is used in anger the character changes and there is a lovely induction roar - think new E46 CSL! The biggest change, however, is on a hot day and in traffic. The lacklustre performance when you have been sitting around is no longer there and the car just takes off. The other big benefit I have noticed is that fuel consumption has improved. On a run from Leeds to London cruising at motorway speeds and not thinking about fuel economy I achieved 31mpg which is not bad for a 20 year old 6 series with 135k on the clock. The plan is to rolling road the car in February on the same dyno and to get an objective indication of the performance gain.

 

I would like to thank Nigel at ALTiSS Engineering and would like to give him a small plug as without his help I would not have finished the above project. If you need any metal work done in any material he is your man and can be contacted on 07890 591618 or ALTiSSeng@aol.com

 

 Thanks Guys, sounds as if a standard filter may be the way.

Despite the ridiculous amount of time I've invested in
this I do actually agree with Andy. I've enjoyed
mucking about though and no doubt it won't stop
there. Fritz Manifold next.

Hi Leroy,

I'm just going through the same process at the
moment and have had numerous emails with
James Sohl who undoubtedly has an amazing set
up.

I nearly went for the same set up as James as you
won't find any induction kits for the E24 listed. The
problem of forced air induction and heatshield
protection to keep the air cool seemed to be the
problem.

Only yesterday I was set to order a Pipercross
Venom (universal set up £120) or the Viper at £250.
But I didn't after speaking to a performance
specialist who builds rally cars, he told me that I
was wasting my money on fancy induction kits as the
car under normal driving conditions will suck in
loads of cold air to the filter and only gets hot when in
slow moving traffic. He recommended the
pipercross Vector which you can order to the
required bore size. He fits loads of these and he
said it would make a significant difference (some
say not). He seemed really sound and wasn't trying
to sell me anything as he knew I was going to
Halfords anyhow. In short what he said made total
sense.

To cut a long story short I've ordered a Pipercross
Vector filter with a 76mm bore size (£75) and an
80mm Samco 90 degree hose. I may need to
fashion a bracket to support it and I may make a
heatshield and fit a cold air feed depending on how it
performs.

Pete

 Hi All, about time i replaced my air filter and I'm just wondering if any one has got, or tried the performance ones you can get? not induction kit just the filter.

Do they make any difference?