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Discussion Starter #1
Hi again,

got another question that you guys should be able to answer because people here are very smart :D

My bf got a 07 M50 and changed the pipes for the Cobra's Slashdown and added a Cobra Fi 2000 Fuel Management and also changed the air filter for an K&N one.
The problem is that after all this changes he's using more gas than before, about 40 miles per gallon and when the bike is on idle you can smell gas, so we think is running rich. Right now is set on the factory settings (3.5-5-3.5) and we called Cobra and they recommended to change the settings to 3-4-3.
Do you guys think that that should take care of the problem or should we do something else?
Has anyone else had has that problem also?

Thanks!!
 

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This is how I understand it, but I might not have it completely correct.

Engines are designed with a particular air-to-fuel (AF) ratio in mind. By changing out the stock air filter for the K&N there is more air being introduced to the engine. In order to maintain the appropriate AF ratio more fuel is needed to mix with the greater volume of air - that's what the fuel controller does. More air means a need for more fuel or else you'll be running too lean and that is an issue you don't want (high likelihood for damaging the engine - if not inevitable). And since you're having to use more fuel than before, ergo you get less mileage per gallon. The trade-off is that there should be an increase in hp and torque when the fuel controller is tuned to achieve the correct AF ratio.

Others around here can correct me if I've made any errors in my reasoning.

I can't address whether the 3-4-3 settings will provide the correct AF ratio, but there's probably someone around here that is using the same pipes/filter/Fi2000 combination that can share what their settings are.

My personal experience is that my mileage dropped about 3-4 miles per gallon when I added aftermarket pipes, hypercharger and PCIII fuel controller. It was worth it to me considering the gains I saw in hp (+21%) and torque (+13%).
 

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Do you guys think that that should take care of the problem or should we do something else?
Has anyone else had has that problem also?
His gas mileage won't be as good as stock.......'cause that's kind of the whole point. To get more power to the ground, it will take more fuel.

Yes, for starters he should take the advice of the manufacturer...........at least until he finds another rider with the exact setup he has.
 

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Leg Humps The Snap On Tool Man
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He might also be leaning on it harder decreasing the fuel economy.

NMc
 

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Discussion Starter #6
First of all thank you to all of you for answering.

Quantumcat, never really thought of it that way, but you might be right, it does make sense what you are saying. I will mention it to the bf and see what he says.

burnchassis, what do you mean by check the plugs? Being a girl certain things escape me lol ;)

Easyrider, you're right, I'll wait to see if someone else has the same set up.

I will post again later with his thoughts on the new setting that Cobra gave us, maybe it'll help someone else with the same problem.
 

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Burnchassis can correct me if I'm wrong, but I think he's referring to the fact that if the plugs are fouled, the fuel injected into the cylinders may not be combusted fully. This would reduce your mpg and result in exhaust with uncombusted fuel; hence a smell of fuel in the exhaust.

Analyzing the appearance of sparkplugs is a great way of getting an idea of the state of the engine's combustion. The following link provides pictures of plugs in various states of wear/fouling and what the likely causes are.

http://www.classictruckshop.com/clubs/earlyburbs/projects/spark/plugs.htm
 

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Discussion Starter #8
Thanks Quantumcat, very good link. I'll tell him to check it out!!
I am learning so much here!!!!
Thanks guys!
 

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I should point out that if the bike is using platinum or iridium plugs, DO NOT attempt to file the electrode tip as a part of plug maintenance (or so I've been warned by the manufacturers).

I'm not sure why this is, but I'll follow the mfg. recommendations.
 

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Leg Humps The Snap On Tool Man
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Quantum great post all around. Never file or use emery cloth on platinum or iridium or the next unobtainium plugs. They are only plated with such high end metals. If you file away the plating the electrode and ground will vaporize. These metals stand up to more heat and there for more powerfull spark. The base metal underneath is not half as resilient. They also burn hot enough to vaporize carbon build up which is why they are rated for such a long life.

NMc
 

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Thanks for the explanation fear_cartaidh. I always wondered why that was even while adhereing to the mfg. suggestions.
 
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