I WANT TO BUY AN HMF EXHAUST WITH QUEIT CORE FOR MY 700EFI AND HAVE A FEW QUESTIONS. IS ANYONE RUNNING THIS COMBINATION, HOW MUCH POWER GAIN SHOULD I EXPECT AN HOW MUCH LOUDER IS THE HMF WITH THE QUEIT CORE THAN THE STOCK MUFFLER? ALSO. WHEN YOU INSTALL THE HMF ON AN EFI WILL THE FUEL INJECTION SYSTEM COMPENSATE THE FUEL OR WILL ANOTHER COMMAND MODULE HAVE TO BE INSTALLED? THE DEALER SAID THAT IT SHOULD RUN FINE WITH THE EXHAUST AND QUEIT CORE AND NOT REQUIRE THE MODULE BUT ADDED IT WOULD BENEFIT MORE IF IT WERE INSTALLED.
WHAT ARE YOUR THOUGHTS , DO YOU THINK WITHOUT THE MODULE IT WILL STILL RUN SMOOTH AND HAVE ADDITIONAL POWER. THANKS FOR ANY COMMENTS OR SUGGESTIONS.

500 AUTO 06 (SOLD)
700EFI 07

 

Extra power- yeah, it will give you a bit more snap, don't expect anything life changing.

EFI- The computer will do everything it needs to compensate for the extra airflow.

Loud- yeah, you will NOT be mistaken for having a stock exhaust with the HMF. It's got some added decibels.

Module- not required for the exhaust, still nice to have.

 

The pcm will do all it can but it is limmited in what it can do. the efi system on the cats do not have an O2 sensor in the exhaust to adjust the a/f ratio. what i've heard is that the quad will run fine but there is a chance that the exhaust will be too hot and you run the chance of burning out your silencer quickly without the modual. and if its true that you can burn up the silencer i would think that the exhaust valves are not far behind.

jsut like rejetting a carb when you add exhaust you probably should use the modual but its not required.

let me know how evrything works for you. i plan on doing the same to my 700 when i get the cash.

 

Question: If the stock module can't adjust a/f without a co2 sensor, why would an aftermarket one make any difference?

The stock module does indeed adjust a/f, thats what EFI does, that's the point. That's why you can ride it in the mountains without rejetting. You'll be fine with the stock module and aftermarket pipe.

 

what i said about the silencer burnig out is just what ive heard

the way efi works on quads is the pcm looks at throtle angle and has a set ammount of fuel for that angle called a fuel map. it adjust the fuel map to coolant temp, air temp and air density (ellevation) it has no feedback for exhaust, it dosent know if the a/f ratio is correctit just assumes that it is. if you and an exhaust system (or cam's, bigbore, intake...) the ratio wont be right and the pcm will have no idea. since the modual can adjust for increased airflow (air density) its not as imporetant as rejetting, but it sould be done.

thats where the after market modual comes into play, you download fuel maps for different modifications you do into the modual and it knows what a/f ratio to use, just like rejetting a carb for a pipe you should have a new fuel map.

if your really looking to get performance out of your quad the best bang for your buck is the modual anyway.

if you really want an in depth explination into the working of a fuel injection system and how the differnt modifications will affect it i would be happy to do so just let me know.