Radical difference in fuel consumption with exhausts(solved)

[thunder]

Hi everyone.

Now i know these girls are thirsty, but i have a set of aftermarket(very loud and a gorgeous sound) exhausts as well as the originals.
With the originals i get 160 km per tank.
with aftermarket i get 100km per tank.

??? Why?

The jets haven't changed. The system is more free flow with the aftermarkets but it's a huge difference in consumption...

Any help explaining this is appreciated as i cannot figure why the difference is so great.

[agentpineapple]

i'd put money on the fact that your bike is now running rich because of the exhaust change and not having re-jetted the carbs, and maybe being a bit more generous with the throttle because the bike now sounds/feels better.......imho

[thunder]

, pretty sure I've been a bit heavier on the throttle.
But not 60km worth(nearly half my range less)
But (to my thinking , and i could be wrong) , free'er flowing pipes would require a larger jets?, that would explain a heavy juice consumption, but putting the pipes on without
a re-jet, is still causing a huge increase in consumption?

[Fireman on a Storm]

Strange! On both of my storms without re jetting my fuel ecconomy improved when I went from standard cans to race cans! Must be the right wrist!

[thunder]

Well, honestly i'm not riding a third more aggressively or faster.
I'm going to fill 'er up again, and double check my figures, and if they are as bad as this last ride, back goes the originals.

[AMCQ46]

Strange! On both of my storms without re jetting my fuel ecconomy improved when I went from standard cans to race cans! Must be the right wrist!

same here, race cans and filters will generally lean the bike off, so you would add richer jetting, then you go back to stock and you are too rich and waste fuel.

cant think how it is working the other way round, but a dyno test will tell you if you have it set up correctly for the race cans

[seb421]

Strange! On both of my storms without re jetting my fuel ecconomy improved when I went from standard cans to race cans! Must be the right wrist!

Same for me this, i noticed i longer range when i changed from the originals

[thunder]

Bloody hell, just filled up... 90 odd km from the last tankful.

I cannot think of any reason the bike should be +-1/3rd heavier on juice with aftermarket cans on? Anybody?

Well, I'm going to run this tank dry to confirm the terrible mileage, then back to the old ("i didn't see you") quiet cans .

Original CANS += Town riding: +- 145km (conservative)
Highway +-180km

Aftermarket CANS Town riding +-90km?!

I know what you guys are saying, about it being the other way round, so this doesn't make sense to me.

The bike seems to run fine, starts fine, cold or hot, goes etc...

Just a thought, i haven't changed air filter this last service, would that account for any petrol difference between the cans?

[seb421]

Bloody hell, just filled up... 90 odd km from the last tankful.

I cannot think of any reason the bike should be +-1/3rd heavier on juice with aftermarket cans on? Anybody?

Well, I'm going to run this tank dry to confirm the terrible mileage, then back to the old ("i didn't see you") quiet cans .

Original CANS += Town riding: +- 145km (conservative)
Highway +-180km

Aftermarket CANS Town riding +-90km?!

I know what you guys are saying, about it being the other way round, so this doesn't make sense to me.

The bike seems to run fine, starts fine, cold or hot, goes etc...

Just a thought, i haven't changed air filter this last service, would that account for any petrol difference between the cans?

well something is up unless your town riding is 1st and 2nd gear twatting it about

[gafr]

freer flowing pipes, no matter weather noisier or not , means more fuel use, i.e. less m.p.g.
you need to put the bike in for a carb balance, re-jet and general tart up to get the miles per sorted, right now thats really expensive, even if it does sound brill!

[tony.mon]

You may well find that the bike is producing less power in the midrange, where most people ride these, and you're just using more throttle to compensate.
Get it set up on the dyno.

And if you fit cans, might as well fit a filter and jet kit, otherwise all you'll get is more noise.

[Sandyback]

This is a confusing thread...........everything I have read or heard about regarding free-flow exhausts (compared with stock) is that they make the vehicle run leaner and therefore, if anything should be more fuel efficient.
I've recently fitted a set of Fuel cans to mine but haven't taken her out for a decent run yet so don't know how mine will be - should be out next month, weather permitting

[Sandyback]

"I cannot think of any reason the bike should be +-1/3rd heavier on juice with aftermarket cans on? Anybody?"

You haven't got something partially blocking your air intakes? or a really shitty air cleaner I presume?

[thunder]

Well, not knowing where to find a dyno around here, (cape town, south Africa) , let alone a VTR guru who knows his way around jets, i am unfortunately going to
put the original cans back on.
I know it doesn't make sense... but my figures (re-checked again) are not wrong, it really is much lighter on fuel with the original cans on (no re-jetting at all).

Eventually, i will get these aftermarket ones semi-packed and see if they make a difference then.

Could back pressure have anything to do with it?

Thor

[bazza696]

just putting it out there, could it be that she has larger jets and air filter with the standard cans(we know that people change them back to make a few dollars extra) but left the dynojet jets on, now the aftermarket cans has made the bike run better harder on the wrist and thus more fuel.