Yamaha Rhino Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hi All..2nd post here. I'm getting to know my new to me 2009 700 EFI sport edition. Using it for some basic work around the farm in moderately cold weather so far, so really light loads, and probably not even close to getting up to normal coolant temps. It starts and runs great, which is one of the nice advantages of EFI over carbureted engines. It does seem to be running a bit "fat" in the traditional sense in that it seems to be running pretty rich given the heavy fuel smell of the exhaust. In fact, I can still smell it on my clothes 30 minute later and my eyes are irritated. I have a new spark plug on the way and plan to clean the air filter when I change the oil this weekend as well as run some injector cleaner through it.

It had 1/4 tank of fuel when I bought it, and topped it off with fresh 93 octane gas. Anything else I need to check? The engine runs fine, no misfire or hesitation, just the clear rich smell to the exhaust. With my limited engine experience that is usually an air fuel ratio (air filter or fuel injector) or combustion issue (spark plug).
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
Thanks Todd...didn't realize the 93 would make that kind of difference. I generally run 93 octane in my mower and weed eater and other engines so just went with that for consistency. It has the factory split folding front windscreen and roof, but no back panel. I'm sure that creates a bit of a way to trap some exhaust as well.
 

·
Vendor
Joined
·
3,485 Posts
Thanks Todd...didn't realize the 93 would make that kind of difference. I generally run 93 octane in my mower and weed eater and other engines so just went with that for consistency. It has the factory split folding front windscreen and roof, but no back panel. I'm sure that creates a bit of a way to trap some exhaust as well.
You should stop in those things too, just spending money and getting less performance. Higher octane is a slower burning fuel but a higher BTU output due to more hydrocarbons. The purpose of it is like in a high compression engine, it speeds up the combustion but with 87 that burns so fast it will detonate, so you put slower burning fuel in to get the peak power pulse where it should be which is around 15 degrees top dead center. So running high octane in something that does not require it is actually less performance and runs richer.

The half windshield does form a vacuum and bring exhaust smell to the front.

Stock tip on the exhaust?
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5
You should stop in those things too, just spending money and getting less performance. Higher octane is a slower burning fuel but a higher BTU output due to more hydrocarbons. The purpose of it is like in a high compression engine, it speeds up the combustion but with 87 that burns so fast it will detonate, so you put slower burning fuel in to get the peak power pulse where it should be which is around 15 degrees top dead center. So running high octane in something that does not require it is actually less performance and runs richer.

The half windshield does form a vacuum and bring exhaust smell to the front.

Stock tip on the exhaust?

Yep, stock tip on the exhaust. The new plug and filter are in, so I'll go ahead and do those (will keep the old air filter for a spare), as well as an oil change.

My engine background is in diesels and I did a lot of performance and emissions work early in my career for a major manufacturer. Odor and eye irritation is usually from un-burned or incompletely burned hydrocarbons and incomplete combustion. Most often that was due to either wet stacking (not enough temp to actually have auto ignition, so fuel is boiled and pushed out into the exhaust as a wet vapor), or extremely late end of combustion.

So, what you are saying absolutely makes sense, but I didn't realize that within that narrow octane range that it made enough difference in the combustion rate to swing from normal stochiometric to a perceived rich condition where there isn't enough air to combust all the fuel, so you get the unburned hydrocarbons that have the odor and the irritant traits. I've typically gone with the higher octane for my mowers and such since usually that is within the ethanol limits of those engines, and assumed that the added knock resistance of the higher octane only helped the situation.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #6
Did basic maintenance on it today, oil and filter change, replaced the plug, and put in a new air filter. It definitely doesn't smell as rich now. I'll see if I can load a picture of the old plug, but pretty heavy light brown build up on the electrode, and the end of the threads were wet. Once I run out this tank of fuel I'll drop back a bit on the octane. Is there an ethanol limit for these engines?
 
1 - 8 of 8 Posts
Top