K&N Explanation please

[Bendy toy]

My 1.7 litre HGT Fiat made 130bhp but a decat and fancy exhaust would get to 150 or more. Power per cc not so much different to an R1200.
The HGT has a single throttle body which doesn't seem to be a flow issue until fancy cams are used. Even then it never gets a throttle body per cylinder.

So apart from tradition why does an R1200 need two throttle bodies? They quite possibly cause more negative side effects in terms of power and reliability than the ever give in terms of power output.
Space can't be the issue - the standard air box is huge.
A single TB would certainly be a lot easier in terms of engine management which should mean less cost and a better outcome.

 

[Deleted account 190920001]

Bikes always have separate TB's mostly because they don't have the room for the runners and plenum that you need for a single TB. The runners from the inlet to the TB would also have to be solid so they don't collapse under vacuum. If you look at a car you will see inlet runners then plenum then TB and then the pipework to the air filter and air filter itself. Thats a lot of stuff to fit into a bike which traditionally has very short runners from inlet to TB or carb then pipework to the air filter. Plenums are also an art, They have to be big enough to stop the pulses from other pots destroying airflow to another. Too small and it will choke leading to big performance issues. Its just easier and more compact to do multi TB on a bike. I would bet that there are plenty of your Fiats out there that have been converted to ITB as well. I found a few just on a quick google claiming 40 BHP from them. 4Cyl bike TB's are cheap now and lots of guys are using them on cars along with aftermarket ECU's. Where it used to cost thousands to convert a car £500 including a Megasquirt will get it done for you. I have done a few V8s for people with bike TB's for not a lot of money. Most of it is in the custom inlet to fit the TB's but if you can fab that up yourself you save a big chunk.

 

[cookie]

Several guzzis have single throttle bodies

 

[Deleted account 190920001]

Several guzzis have single throttle bodies

So do Harleys. Doesn't make it good though lol.

 

[bone48]

So if it runs lean because the ECU doesn't have the required sensors to do the job properly am I correct in assuming that it runs too lean as standard?


Sent from my iPhone using Tapatalk

 

[cookie]

So do Harleys. Doesn't make it good though lol.

i didn't say it did, but you did say "Bikes always have separate TB's".

 

[Bendy toy]

Bikes always have separate TB's mostly because they don't have the room for the runners and plenum that you need for a single TB. The runners from the inlet to the TB would also have to be solid so they don't collapse under vacuum. If you look at a car you will see inlet runners then plenum then TB and then the pipework to the air filter and air filter itself. Thats a lot of stuff to fit into a bike which traditionally has very short runners from inlet to TB or carb then pipework to the air filter. Plenums are also an art, They have to be big enough to stop the pulses from other pots destroying airflow to another. Too small and it will choke leading to big performance issues. Its just easier and more compact to do multi TB on a bike. I would bet that there are plenty of your Fiats out there that have been converted to ITB as well. I found a few just on a quick google claiming 40 BHP from them. 4Cyl bike TB's are cheap now and lots of guys are using them on cars along with aftermarket ECU's. Where it used to cost thousands to convert a car £500 including a Megasquirt will get it done for you. I have done a few V8s for people with bike TB's for not a lot of money. Most of it is in the custom inlet to fit the TB's but if you can fab that up yourself you save a big chunk.

I have no argument with this for a high revving 4 cylinder bike that has short inlet tracts. And of course for ultimate high revs top end power this is the only way to go.

But on a big relatively slow running engine there is little or no benefit. Also the R1200 already has a humungous air box. A plenum chamber by any other name. There is more than enough room for a proper plenum with single throttle body. At a stroke we solve the engine management and maintenance issues of twin throttle bodies. We would probably get a better airflow into each cylinder. The current setup is not giving a fully smooth flow into the cylinders and it favours the lower inlet valves.

Back in the 1970s David Vizard was getting amazing results from BL A-Series engines. 120bhp from a 1275 was quite possible with a single 1.5" SU carb. There were fancy cams and all sorts of gas flow work, including the carb, but he showed just what can be done with what was (even then) a very compromised cylinder head design.

Separate inlet chokes (slpit Weber side-draughts) would give ultimate race power (which is what we have today in 4 banger bikes) but that was totally unsuitable for the road.

 

[Nick dj]

Good choice

I fitted an Akro end can just before my 12k service which made a big difference and somehow seemed to make the bike run smoother.
I was offered a K & N copy as part of the service by Alan Jefferies for £15 extra.
They assured me the bike would be set up to run correctly with the new filter and the new end can.
WOW even better still, pulls better throughout the rev range.
May not be quiet as good as Hilltop, but for £15 it was worth it for me.

Would highly recommend just the Akro to any Twin Cam owner

Nick

 

[facom]

MAF sensor ,knock sensor and lambda sensor all help to let the engine run at its most efficient at any given revs, so fitting a freer flowing filter will not make an engine run lean because the ECU will compensate and get the engine running as close to lambda 1 as possible

 

[cookie]

MAF sensor ,knock sensor and lambda sensor all help to let the engine run at its most efficient at any given revs, so fitting a freer flowing filter will not make an engine run lean because the ECU will compensate and get the engine running as close to lambda 1 as possible

There is definitely no MAF sensor.

I believe the lambda controlled closed loop does not work throughout the entire rev range.

 

[facom]

are you sure ? because there is a sensor fitted to the n/s intake duct of my GSA

 

[cookie]

Are you talking about the tps unit?

 

[facom]

Are you talking about the tps unit?

tps ?

 

[Deleted account 190920001]

There is a intake air temp sensor on the nearside and as cookie said a throttle position sensor on the nearside TB. Definitely no MAF sensor on a 1200GS.

 

[facom]

your right, I'm wrong

 

[Bendy toy]

There is also no diagnostics on coil failure and (I believe) non on O2 sensors either. Faults are found by picking up the symptoms. At least it means less hassle with computer jockeys telling you the tyre pressure sensor is causing the black exhaust smoke.

 

[Deleted account 190920001]

You can pick up O2 sensor faults with GS911 via codes and via looking at the trace. Nothing for coil though.