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Hi all,

the other weekend i installed a DNA filter in my tenere. All went well and i can feel the bike breathing much better. I'm also running an iridum plpug.

But i am now 3 tanks of fuel into the new filter and my f-trip now comes on at 210 miles where is was coming on at 250 miles before hte DNA was instelled.

I ride the same router everyday to work...same rider...same roads...same fuel..nothing has changed.

The idle has not chnaged in any way either.

So is this normal? Should i expect such a drop in MPG?

i will get a kev mod soon but need to do xmas first.

Any ideas please?

Mike

There was a thread about the bike's not running so good on the iridium plug's, i've not fitted mine yet so cannot comment, but might be worth a search :)

Good point, I would go back to the original plug and try 3 tankfulls as if you make only 1 change at a time you have a chance of understanding the changes.....I found a slight increase in fuel consumtion when I fitted the Stage 2 DNA filter but I think that this was down to a new er even-open throttle hehehe.....

Quote:

Originally Posted by SimonRoma (Post 194908)

I forget to mention that i fitted the plug a couple of months ago and didn't notice a change in anything.

It's only since putting in the DNA stage 1 that i've seen such a drop in MPG.

Mike

I notice a drop in mpg once it gets colder, maybe its that?

A change from 250 to 210 miles before the F-Trip is almost a 20% drop in fuel economy – which is quite a lot! I very much doubt that a change to a DNA stage 1 filter will have caused this all on its own?

Has the filter been over-oiled? Brakes binding due to the salty roads? Chain deteriorated? Are you being more throttle-happy? As you said, you can “feel the bike breathing better.” I’d guess the ambient temperature is also a lot lower on your commute recently, more so than when you had the OE filter in? Is it a short commute? That’ll make the negative effects of cold weather on fuel economy more pronounced.

I’m with RBJ on the cold weather conspiracy.

All engines have an optimum operating temperature, and the colder it is, the longer it takes to get there. Although the sensors and ECU take account of a lot of variables, the essential fact is that the fuel injection system is only fully efficient when the engine is at full operating temperature. When the ambient temperature is low, the motor requires a longer period of time to reach full operating temperature (and efficiency) —and it’s in that warm-up period that a lot of fuel efficiency is lost.

Colder weather increases friction too. The oil is thicker and more resistant to flowing when cold, so it’s harder to pump, which means more work for the engine. Rolling resistance also increases with a drop in ambient temperature, which isn’t what we naturally assume – usually we think of dry hot days as good for high friction (grip). Tyres, for example lose approximately 2psi for every drop of 10C, which increases rolling resistance and hurts economy.

Also, add to the above the fact the battery takes longer to recover from starting, so causes more drag from the alternator as it tries to get the battery voltage back to where it should be.

Having said all of that, I tend to get more mpg in the winter! However, I definitely know I ride less enthusiastically in the colder months, which kind of cancels things out.

Blimey, excellent analysis Pleiades!!! I too notice a great difference in how my XT performs when the weather changes and I too ride differently but I do not usually see my fuel consumption change by more than about 10%, the 20% stated is alot.

Quote:

Originally Posted by Pleiades (Post 194920)

A change from 250 to 210 miles before the F-Trip is almost a 20% drop in fuel economy � which is quite a lot! I very much doubt that a change to a DNA stage 1 filter will have caused this all on its own?

Has the filter been over-oiled? Brakes binding due to the salty roads? Chain deteriorated? Are you being more throttle-happy? As you said, you can �feel the bike breathing better.� I�d guess the ambient temperature is also a lot lower on your commute recently, more so than when you had the OE filter in? Is it a short commute? That�ll make the negative effects of cold weather on fuel economy more pronounced.

I�m with RBJ on the cold weather conspiracy.

All engines have an optimum operating temperature, and the colder it is, the longer it takes to get there. Although the sensors and ECU take account of a lot of variables, the essential fact is that the fuel injection system is only fully efficient when the engine is at full operating temperature. When the ambient temperature is low, the motor requires a longer period of time to reach full operating temperature (and efficiency) �and it�s in that warm-up period that a lot of fuel efficiency is lost.

Colder weather increases friction too. The oil is thicker and more resistant to flowing when cold, so it�s harder to pump, which means more work for the engine. Rolling resistance also increases with a drop in ambient temperature, which isn�t what we naturally assume � usually we think of dry hot days as good for high friction (grip). Tyres, for example lose approximately 2psi for every drop of 10C, which increases rolling resistance and hurts economy.

Also, add to the above the fact the battery takes longer to recover from starting, so causes more drag from the alternator as it tries to get the battery voltage back to where it should be.

Having said all of that, I tend to get more mpg in the winter! However, I definitely know I ride less enthusiastically in the colder months, which kind of cancels things out.

Morning,

thanks for the long reply. I've had a good think and gone through most of what you say and here are my answers.

The bike is was cleaned spotless about 6 weeks ago and the covered in ACF50 so salt is not an issue.

The commute has not changed in the past 6 montsh and is 35 miles/1 hour each way.

I use the same fuel from 3 different stations.

I have no other electrical devices other thna a Zumo 660 which takes nothing really.

The brakes are fine as is the chain.

3 weeks ago the weather was the same as we have now and i was getting 250 before f-trip and now i'm getting 210 at best.

All that has changed is the DNA filter...which was not oiled at all.

The bike does seem to rev a bit cleaner.

I ride no different to before and if anything i ride slower than 2 months ago due to the dark and slippery roads.

One thing that i have noticed is that before the new filter the bike would pull hard on full throttle from 3k without any banging or bucking. Now it's about 3200 before i can give it lots of right hand.

The bike has 11k miles on it as of this morning and is a 2010 model. I chanegd the filter at 10K...it was the OEM filter fomr new and was very dirty inside...lots of dead insects etc.

Mike

OK, so the riding conditions are the same and the weather can be ruled out.

Short of getting your bike on a dyno, it’s going to be difficult to second guess what’s going on.

However, there are a couple of tit-bits of information you have just revealed which may give a clue as to what’s happened.

Quote:

Originally Posted by Mike101 (Post 194944)

One thing that i have noticed is that before the new filter the bike would pull hard on full throttle from 3k without any banging or bucking. Now it's about 3200 before i can give it lots of right hand.

Now, in my experience of the XT motor, when the bike runs towards the rich side of a 14:1 A/F ratio the tractability improves, when on the lean side of this it doesn’t pull until 3000rpm+ (what you have noted). You say that the point at which it pulls cleanly has risen a little since fitting the filter, which would suggest that the fuelling has indeed leaned out a bit.

Quote:

Originally Posted by Mike101 (Post 194944)

The bike has 11k miles on it as of this morning and is a 2010 model. I chanegd the filter at 10K...it was the OEM filter fomr new and was very dirty inside...lots of dead insects etc.

If you were running a dirty 10K mile OE filter previously it could well be that, ironically, the dirty filter was in fact causing a slightly lowered A/F ratio (effectively slightly choking the motor), bringing it closer to the optimum which the XT motor runs more efficiently at? ~13.6:1 being roughly where it runs combustion is most efficient.

Changing to a new, clean air filter will lean things out anyway (normal), but changing to a high-flow filter straight from a dirty old OE one may quite possibly have exacerbated the effect. This may explain the larger than expected 20% jump in mpg. It would probably have been a significantly less so if going from a clean OE filter to a new DNA filter (like for like)?

Now, you probably think a leaner running engine is more fuel efficient, but more often than not it just isn’t the case. Economy and engine efficiency will be best at the optimum A/F ratio. As the combustion is less efficient at higher (weaker) A/F ratios, wider throttle openings (often subconsciously on the rider’s part) are required to achieve the same forward momentum, hence the potential for lower economy.

I would imagine fitting a Kev Mod or other fuelling devise to enrich the A/F ratio to ~13.6:1 will improve your economy situation...