AF-XIED for a standard bike?

[DeuceBG]

Like I said, it's a free country.
I think most people end up with a remap or AF XiED's, after trying booster plugs, exhausts, filters, etc.
De-cat headers seem to give a slight boost at the higher end of the revs, although my OPINION is that there may be a reduction in the mid range.
With silencers, I think much of it is in the mind.
A German magazine tested all available aftermarket silencers at the time on a TC and dyno'd them rather than using opinions.
The vast majority, and there were plenty, actually reduced power, despite being louder. A couple of the top end ones like Akro, gave the same as stock. Only two improved the power output by two or three bhp and they were seriously LOUD.
Their conclusion was that BMW had produced a system that gave the best power with a modest noise.
By the way, they did a video of the tests to allow people to hear the silencers and just about all of them had that hesitation moving off, which to some of us, is but a memory.
The stock ECU with or without AF XiED units, will quickly adapt to changes to headers and silencers. I believe that I read that Geoff in Hilltop felt that to change the air filter as well, might be a step too far in terms of fueling.
I think many of us feel that once the fueling is sorted out by whatever method, what's the point of assaulting your eardrums by using a louder exhaust when there's no real advantage?
For me, the TC standard exhaust, especially without the flappy valve is noisy enough. It sounds sporty to me and I don't care about impressing anyone else.

I'll definitely be keeping the AF's and the Akro Can has long since been removed.
My only remaining interest in the Discussion is whether or not to keep the K&N and the Akro Headers.
From what's being said across the Board I may well revert to Standard on both Counts.
Impressing People never entered into it as far as I'm concerned, just getting the best from my Machine.

 

[Bendy toy]

The ECU adapts so fancy exhaust with standard map will make no difference to the power. And as said may well spoil the mid range.
However add a remap or AF-XIEDs and the free flow exhausts will certainly import with power and maybe with no damage to mpg values.


Sent somehow.

 

[Deleted account 200123001]

Their conclusion was that BMW had produced a system that gave the best power with a modest noise.....I believe that I read that Geoff in Hilltop felt that to change the air filter as well, might be a step too far in terms of fueling.

From memory when I read extensively about tuning up four stroke engines there is quite alot to consider just derestricting everything can be harmful to performance, so that doesnt sound unreasonable to me especially since the boxer engine is more about torque than power. De-restriction to the levels discussed might not actually be beneficial until 12,000 rpm say...often at the expense of low down torque.

I once remember reading an article in MAX POWER (yes i used to read that boy racer trash)....where a tuning company fitted varying lengths of 110dia waste pipe to the inlet tract of a 1.8MG ZS (even upto 3m). I can't remember the figures now but I seem to recall upto a certain length the longer inlet tract actually improved peak torque slightly at the expense of peak power, even though resistance in the inlet tract had theorectically been increased. Something related to the pressure wave phenomenon that occurs in inlet tracts I expect.

 

[comberjohn]

Think the days of opening up your exhausts, throwing away the filter and whacking in big jets are long gone.
Maybe it didn't even do much good all those years ago, anyway!
When you consider that they've had to make a 1200cc, air cooled twin produce a nice spread of power and torque, be smooth and economical AND meet ever increasing emission regs, I think they've done very well. Just that tiny increase in fueling that a remap or AF XiED's can bring, make it almost perfect.
DeuceBG, if it was me and you're happy with your exhaust, leave it where it is. Not going to do any harm.
Not so sure about the K&N, but maybe someone else has some thoughts on that. Anytime I tried one, it lost a lot of low down power. Although, that was using carbs where depression in the inlet was needed to draw in fuel. Fuel injection may be different.

 

[MattW]

I've always found it slightly incredible that the batch injection used in 11xx's actually works (half the fuel charge injected on the power stroke with no inlet draught to help it, the other half conventionally on the induction stroke). I assume that 1200's (being aware of crank position) inject it all in one go. I still think that the tuned length of the inlet tracts matters though - look at the fad a few years ago for swapping the inlets of RT's for the GS part to increase torque.

 

[younger06]

John, when we're up in Donegal, I'm gonna take you up on the offer to try your bike.....and you can have a spin on my bag of spanners, with open exhaust + K&N. It will probably be the little shove I need to purchase these american witchcraft electrickery gadgets. (that's of course if the offer is still open)

 

[Bendy toy]

Watch (in YouTube) what Dave Vizard has to say about conventional tuning.
The moment after the exhaust valve opens the cylinder pressure can drop to -7 psi. The valve overlap allows that depression to pull in the next charge. It explains why well sealed exhaust port gaskets are so important.
That exhaust depression is created as much by an exiting pressure wave as it is by the high speed gas flow. Pressure waves move faster through high pressure gas so a wide open exhaust really can crimp power output especially at the mid range.
2 strokes make heavy use of shock waves to create a suck blow effect in the exhaust but it happens with 4 strokes as well.
BTW high revving / strokes can raise the peak revs by increasing the expansion chamber pressure. Shock waves travel faster. The risk was overhead piston at the exhaust side.


Sent somehow.

 

[comberjohn]

John, when we're up in Donegal, I'm gonna take you up on the offer to try your bike.....and you can have a spin on my bag of spanners, with open exhaust + K&N. It will probably be the little shove I need to purchase these american witchcraft electrickery gadgets. (that's of course if the offer is still open)

Bugger, thought he'd forgotten about that.

 

[younger06]

Bugger, thought he'd forgotten about that.

I'm like an Elephant in many, many ways....... in this case it's my memory.

Sent from a OnePlusX

 

[comberjohn]

Aye, heard that. About the memory, too.

 

[Tractors are go]

When I had my first Cosworth's Lots of time and money was spent on different air filters etc.

Conclusion was if you have shares in K&N and the like buy one, if not don't bother.



Sent from my GT-N7105 using Tapatalk

 

[Mistacat]

For many years I used K&N filters with the K&N open foam over filters with tacky motocross oil on the over filter, when I was off road racing V8 4x4`s.
Paper element filters would have collapsed in a soggy mess and the K&N could be cleaned a couple of times a day.
The amount of rubbish they let through is frightening hence an engine rebuild every season.
So it is a stock paper element for me in the bike.
The twin cam filter has a greater open area in the metal outer support, Pre - TC is perforated compared to a cross of metal in the TC filter, How BMW justify the extra cost for a cheaper manufacturing option beats me.

 

[Deleted account 200123001]

I've always found it slightly incredible that the batch injection used in 11xx's actually works

That's interesting. I didn't know that. One of the draw backs of batch often peddled is puddling in a closed valve....But one could imagine that with a big lumpy twin when the valve does open it creates a vacuum which not only sucks in the fuel but causes a rapid evaporation aided by the heat.

.
The amount of rubbish they let through is frightening hence an engine rebuild every season.
So it is a stock paper element for me in the bike.

Now that is interesting....Some real world proof of what many have suspected. Time to bin my k&n filters I think.

 

[DeuceBG]

Now that is interesting....Some real world proof of what many have suspected. Time to bin my k&n filters I think.

Yes, I'm inclined to agree.
I'll keep the Akro Headers (for now at least) as I suffer no excessive Vibration etc but the Filter can go back to Stock and see what happens over the next few Tanks.

 

[Mistacat]

I think the fact that K&N claim to flow a lot more air but have a fraction of the filter surface area of a stock filter says it all.
Hold one up to the light !!.

 

[DeuceBG]

Hold one up to the light !!.

I see what you mean....It's PINK!!
That's reason enough to bin it IMO!!

Seriously tho, just refitted the Stock Filter and turned the AF's back to #7.
We'll see how she runs now.
Might even give me a few more MPG if I'm lucky...

 

[Bendy toy]

David Vizard did some tests on the K&N for all of the above reasons. He found it really did trap dirt as well as a paper element. The really big factor was to use the correct sticky oil and don't over do the oil.

I personally have a Piper oiled foam filter as its easy to clean. Im sure the filtering ability is good enough because my mother's Honda CB125S did 70,000 miles with the OEM oil foam filter and no signs of excessive cylinder wear. That was with 1970's filter tech and engine oils.

The Hexhead 1200 air inlet tube is way more restrictive than any filter. We have twin 50mm throttles at the engine yet the inlet stack has one crude venturi with a hole about 35mm diameter and petrol tank wall just in front to further restrict air flow. My Fiat Panda making just 60 bhp has a better designed air intake. For better air flow potential, chop off the inlet stack forwards of the front rubber mount and flare the cut edges.

 

[MattW]

For better air flow potential, chop off the inlet stack forwards of the front rubber mount and flare the cut edges.

Or don't if you want to maintain the tuned length of the inlet (which does matter).

And I've seen the damage done through use of K&N filters - I wouldn't use one if you paid me.

 

[Rockred]

I'v done about 300 odd miles now, and here is what I found. At first not a lot of difference, short ride 30 odd miles only. The 2nd ride out 130 miles,with a lot of dual carriageway and some mountain twistys, but noticed an improvement in the roll on roll off while in the lower gears. But today I was able to get out on my own, and do a lot of twists and turns in the mountains up to Ronda and back, and having to vary the throttle more. Did last leg from Sotogrande to home on the dual carriageway, so thought I would see if the bike had changed in the 4500 to 5500 rev range in 6th.......Wow, it pulled like a train, right through the rev range. It's also smoother in town traffic. Well worth it in IMO.

The Bikes a 1200 GSW 15 plate, I set the AF on 7 at first, but soon went to 8 after the first run out.

 

[oldnfat]

Sounds like a result....the effect on my TC was significant but a little surprised it has a similar effect on the WC....I would have that that engine management would have come along way an nullified the effects of lean running engines.