2014 Breakout. SE heavy breather, v&h big radius duals. Was averaging 46-48 mpg. After installing tman 555 torqster cams and dyno tune I'm now in the 39/40 mpg range . I hadn't given it much thought because I don't really care that much but is it normal to lose 6-8 mpg with that type of cam swap ?

 

I have cams in my breakout with a good tune and I'd be willing to bet I lost some mileage. Honestly I don't care much and tend to be heavy handed anyhow. I have had several smallblock autos that had mouse cams and never had my mileage increase. Why wouldn't our vtwins be the same. More cam, more air, more fuel = less mileage. I'm sure many people will say they added cams, got great power and got better mileage, but I didn't.

 

I'm not sure what I got with the stock cams frankly. With the current ones and after a tune I seem to be averaging around 43mpg on highway or if I'm not going crazy on the throttle (which I'm having a hard time doing).

 

Most likely they're fibbing. More cam=more air & fuel=lower mpg unless there is a corresponding increase in combustion efficiency. Possible, but not likely. IME, it's a moot point as the irresistible urge to twist the wick on the hotter motor makes it impossible to tell. I get 32mpg avg. on my 114 HP 95" build, and wouldn't trade any of those horses for a corresponding increase in mpg. Riding should be, first and foremost, fun IMO.

 

Used to get 44 hwy and 38 street. With cams and big bore, etc, now I get about 42 hwy and 33-34, and that's with me driving very conservative.

 

 

Yep. While there are certainly some gains to be made efficiency wise, the bottom line is that more power = more fuel (not necessarily the other way around though, but I digress...). Now while it's true that you don't have to always USE all the extra power on tap, the fact is that if you didn't want to have more power, you'd have left it alone ;-)

 

My 2010 96" with Andrews 48's gets 40-42 average in normal driving. Goes down slightly with more aggressive driving.

My 2005 88" with Andrews 48's gets 44-46 normal and drops slightly with aggressive driving.

Neither tune is optimized for fuel economy. I'm sure I could do a little better with optimization. A good tune makes a lot of difference...but you have to know/tell the tuner what you are looking for.

 

With a SEHB AC and V&H 2-2 I used to get 37+ to 45ish depending on city/highway and how I beat on it. After cams, compression bumpt and TTS vtuning; Im getting 33-39. Havnt had it tuned on a dyno,just the base map and vtuning.

 

I don't get it. If you're gonna upgrade a cam and possible exhaust and air cleaner all to get more tq/hp, why are you so concerned with MPG. I'm lucky to get 36 mpg if I really baby it. Most people upgrade for power not MPG.....