Air intake

[Petrus]

Have found several threads on the air filter. On leaving the lid, snorkels or not.
What was only mentioned indirectly was the áctual intake. That the cable entry in the upper part of the covers also lets air in.
The way I see it, the entries at the front the ´leak´ in the roof are the bottle neck.
Now, has anyone done anything to open up the entry?

This link has several photos which ilustrate what I mean.

BMW R18 Motor

BMW 1800 Big Boxer Höchstleistung 91 PS bei 4.750 U/Min, maximales Drehmoment 158 Nm bei 3.000 U/Min Die Bayern bringen den größten Boxermotor aller Zeiten. Optisch und technisch ist dieser Zweizylinder ein absoluter Augenschmaus.

www.1000ps.at

 

[Noelpolar]

Mmmm.... I'm not sure how much it matters. I've done the DNA stg2 thing, have open rear cans (still have the cats) and have a tune and ride mine hard on windy and hilly roads.... and I never think about more power..... just more torque (haha!). Have also done the suspension.

So what I mean is my fun is lots of throttle in the 1600 to 4,500rpm range in and out of corners, late braking etc etc. Power is really a revs thing and this motor is not about revs.... I'm not sure if more meaningful/significant torque is going to be dependant on less restrictive airflow in the usable rev range I use. Decating would be my next step but open rear cans is enough noise for me. I'm also not sure about cams either (not that there are any).... as I would not want to loose the tractability between 1,200 and 2,000 rpm.

I'll probally get mine dyno'd at some stage as I'm interested to see how it compares to a 114 or 117 now.

Maybe put some time into working on a low presure supercharger bolt on kit (6 to 8psi would be enough).... let me know when you get a kickstarter going....

 

[Petrus]

I did not mention ´powah´ no?!
For slow revving engines like the R18 it is all about bmep and the slightest difference in the flow will directly affect that. As such any restriction in the inlet counts. More so because of 900cc per gulp of air and the quite small air filter/air filter box.
It is fár more important than the exhaust because intake air is moved inside by the pressuere difference between ambient air pressure and cilinder pressure. The difference being max. 1 bar.
At the exhaust side the piston can overcome more.

Yes a compressor would ne GRÉAT for this engine and even retro: See the BMW 255. Would need an AR500 per cilinder so no. I will be looking at the air intakes.

Will fit a SprintFilter insert, open up the cover, leave the snorkels.Then would like to add more generous entry.

Will leave exhaust original.