Aftermarket Header - Advice Please

[Shilo]

Hi Folks

I have been offered a new catless header for my GSA 2006 which has been locally built and is not a Remus, Akro etc however looks pretty similar to the Remus without the balancer pipe, diameter appears to be about 48 mm.

I have done probably too much research on the fitting of header ppes on the BMW boxer that i'm now totally confused and not sure if i should go ahead and buy the header or not. This topic should become a sticky as i have noticed so much has been posted on this forum regarding headers and slip on cans, decatting OEM headers etc.

I have only ridden my BMW for a month now having previously ridden Jap bikes before and two strokes at that. I have found the GSA to be geared high which is great for touring and consumption however urban riding requires using the box often to keep her in her torque range otherwise the boxer starts moaning.

So now to the questions, this is not to find our which header is best or which can and header is best etc but rather to determine from those who are riding non OEM catless headers what is the ride like. Some tests on the net have proven that some headers simply transfer power and torque from one range to the next, others have lost some power and torque compared to the OEM funnily enough and some have shown gains up to 4 - 6%. Is the bottom and mid range smoother, is there surge, is there loud popping due to no back pressure from the non existant cat etc etc.

I want to avoid buyers remorse before i buy and fit so can we have some honest feedback from those who have gone and done the mod thanks.

 

[Tuono1961]

Just two weeks ago I purchased and fitted a secondhand Remus set bought off ebay for my 2008 GS.

Test riding the new twin cam made me do it, so it was either an upgrade or a new bike

My thoughts:-

I didn't go WOW after fitting them but the bike is nicer to ride. Much smoother in the lower revs (although not at idle) and slightly more urgent on the pick up.

The engine spins up easier, where before I found myself either riding on the low down torque or in the upper rev ranges and avoiding the 5k flat spot in the middle. Now I don't seem to worry about it as the engine spins through the middle without so much of a noticeable drop.

The engine note changes. Not as much as fitting an aftermarket can but it definitely sound a bit more throaty which wasn't my aim but I quite like it. The bike has a little bit more "Rumble" about it. And the extra noise is just enough to hide the tractor style cam chain rattle which always bugged me a little. I also think the louder pipe on the new Twin Cam goes a long way to making the engine feel better than maybe it is.

The top end rush doesn't seem as strong but that maybe down to the stronger mid range. Does it have more power ?? Don't know but doubt it, but it's definitely nicer to ride and makes the gap between my bike and the new twin cam so narrow I won't bother upgrading until I see the new Watercooled GS.

There is popping but on my bike but there was before. It doesn't "pop" more often but it is a little louder than before.

I paid £200 for my second hand set of Remus headers and overall I think I have a good return on my investment and would definitely do it again and recommend it. For the record I also have one of those £30 accelerator modules fitted

HTH

 

[Schtum]

An '08 you say - on Remus headers...?

*Sucks teeth*.....probably running far too lean.

Get it on the dyno to have the air/fuel ratios checked and be prepared to buy a Power Commander or something similar.

 

[Shilo]

An '08 you say - on Remus headers...?

*Sucks teeth*.....probably running far too lean.

Get it on the dyno to have the air/fuel ratios checked and be prepared to buy a Power Commander or something similar.

Okay, I have the lamda sensors on my 2006 and was advised that I would i not need to fit a module at all as the sensors will adapt to the flow etc

 

[Tuono1961]

An '08 you say - on Remus headers...?

*Sucks teeth*.....probably running far too lean.

Get it on the dyno to have the air/fuel ratios checked and be prepared to buy a Power Commander or something similar.

You obviously know more than Remus or Akra who are perfectly clear that the bike can cope with the changes without any issues. But hey what do they know they've only been developing exhaust systems for decades

 

[Schtum]

Okay, I have the lamda sensors on my 2006 and was advised that I would i not need to fit a module at all as the sensors will adapt to the flow etc

Whoever told you that, doesn't really understand how the injection system works. The lambda sensors will only alter the fuelling while the system is operating in closed loop mode, ie at relatively small throttle opening and medium revs and then only if the required fuelling lies within the parameters of the OEM map + trims.

At larger throttle openings and higher revs, where any damage from running too lean is most likely to happen, the system is in open loop mode, running off the fuel map + trims and information from the lambda sensors isn't taken into account.

However, my comment was aimed more at Tuono1961 who has an '08 bike which runs leaner as stock than your '06. I had a full Remus system on both my '04 and '07 GSes. The '04 was fine, the '07 was borderline and in general '07s and later bikes run too lean for a full system, according to my local dyno guy.

When the R1200GS was launched in '04, both Remus and Akrapovic claimed that their full systems could be fitted without remapping. That was probably true at the time but people seem to have taken this as never changing gospel. However, the OEM mapping on GSes has got leaner through time.

In any event, if you're fitting a full system to get maximum performance, it makes sense to have the fuelling checked and if necessary remapped to help provide that performance that you're looking for. I don't just mean maximum horsepower - the area under the curve and the smoothness of the horsepower and torque curves is also important.

 

[Schtum]

You obviously know more than Remus or Akra who are perfectly clear that the bike can cope with the changes without any issues. But hey what do they know they've only been developing exhaust systems for decades

See above. That was true in 2004.

 

[Tuono1961]

We aren't talking about a full system, just a change of headers

 

[Schtum]

We aren't talking about a full system, just a change of headers

It's the headers that make the biggest difference, since you're removing the cat'.

 

[Shilo]

We aren't talking about a full system, just a change of headers

I have a Akropovic slip on that is fitted to the std header at the moment so I would probably run the header with the Akro can.

 

[Tuono1961]

It's the headers that make the biggest difference, since you're removing the cat'.

Motorworks who have been supplying parts for BMW's for over 20 years say there's no issue. But hey, I suppose they know nothing as well

So every single supplier of these systems I could find on the net who provide catless headers for 08 and 09 bikes say "no further tuning necessary" but you seem to know something different. No wonder confusion reins on the net

 

[Schtum]

Motorworks who have been supplying parts for BMW's for over 20 years say there's no issue. But hey, I suppose they know nothing as well

There's only one way to be reasonably sure. Take it to a dyno with an operator who knows what he's doing and find out.

Also, as I said, fitting a set of headers without remapping the fuelling to get optimum performance kind of defeats the purpose.

 

[Shilo]

If running to lean at the top, is that going to burn exhaust valves or cause other damage to the motor, normal weekend runs are at 100 -140 Km/ph

 

[Shilo]

If running to lean at the top, is that going to burn exhaust valves or cause other damage to the motor, normal weekend runs are at 100 -140 Km/ph, I think we moving

 

[Tuono1961]

Also, as I said, fitting a set of headers without remapping the fuelling to get optimum performance kind of defeats the purpose.

No it doesn't. Fitting a set of headers gives a good seat of the pants performance increase and I believe is good value for money.

In my experience fitting a Power Commander type thing with all the associated Dyno time at the thick end of £600 doesn't.

 

[Schtum]

If running to lean at the top, is that going to burn exhaust valves or cause other damage to the motor, normal weekend runs are at 100 -140 Km/ph

In theory, yes but you really need to get it on a dyno to find out what it's doing in practice. However, as I said, my experience is that the earlier bikes, pre '07, are mapped richer as standard and aren't at such risk of damage from running too lean when you fit a set of aftermarket headers.

 

[Schtum]

In my experience fitting a Power Commander type thing with all the associated Dyno time at the thick end of £600 doesn't.

You've done this on an R1200GS...?

 

[Shilo]

Gents

The problem with the header is once i've fitted it and run it I can't take it back as we know the stainless is going to tarnish quickly hence my post on the forum.

At the current exchange rate, I'm looking at paying 390 P for the header so it's a bit of a gamble.

 

[Beemerman59]

Having spent the last two years gradually adjusting the exhaust/fuel system on my '08 GSA I still can only go on my opinion based upon "seat of the pants" experience. These are the combinations I have run to date other than a completely standard set up:

1) OEM headers & Akra can

Result - no performance difference but nicer noise

2) Remus headers & OEM can

Result - Slightly better low speed fueling and mid range. Nicer noise than a completely standard system but not as good as 1)

3) Remus headers & Akra can & Accelerator module (£30 jobby)

Result - Slight improvement on low speed fueling ( but still a bit jerky at slow speeds), I did'nt notice any improvements in mid range over 2) above. Lovely noise.

4) Remus headers & Akra can & K&N air filter & Wunderlich Performance Controller & Iridium plugs

Result - Finally got rid of the slow speed concerns and don't have to have my hand feathering the clutch at low speed anymore. Goes like stink all the way up the rev range. The engine finally feels free to run as it should. I am running the standard Wunderlich fuel map for open headers/sports can and free flow air filter. Other than the cost ( and the wish that I did'nt have to spend so much to fix the lean fueling as standard) I am now very happy with how the bike runs.

I have two other observations on the final set up I am now running. It needs the baffle in the Akra to run cleanly. Taking it out does not improve performance but does make it sound really nice especially on the overrun. The downside with the baffle out is that the engine will readily stall at low speeds as per previous threads on the issue. With the baffle in, the engine has not yet stalled under any set of conditions.

The bike now uses more fuel when I'm being enthusiastic and less fuel if I'm bimbling along enjoying the scenery. And while I think about it, the headers don't glow red anymore when idling in the garage which they used to do before fitting the Wunderlich or Accelerator module.

These are just my own observations you understand.......

 

[claw]

I have Remus headers and akro can on my 2008 GSA. It also has the accelerator module fitted.

I had it on a dyno in the summer and the guy running the dyno said it was running lean at high revs. Take the baffles out and it gets really upset and seems to 'miss' when your moving on a bit.

Its due for a service next week then i'm going to get the engine remapped.

My 2007 GSA had the same Remus headers and a remus powercone end can, and that ran fine with or without the baffle. Never had that one on a dyno run though.