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Exhaust Back Pressure

S

Smartleynz

Tuned and Synch'ed
Joined
Oct 1, 2014
Messages
92
Location
Taranaki New Zealand
Do Guzzi engines run better or worse with or without exhaust back pressure? My esteemed HOG owning mates reckon I should run Straight pipes "works on our Harleys". My thought is that Guzzis like a bit of back pressure? but I really don't know.
 
It depends on a lot of things. Some motors need more back pressure to run better than others do. Part of it is cam timing and over lap. HD engines tend to have very little valve over lap in their cams. So they can run better with less exhaust back pressure. Forced induction motors also do better with less exhaust back pressure.
The older 2 valve per cylinder Guzzi motors (and the old 4 valve motors) tend to do well with less back pressure. The newer 8 valve CARC engines seem to need more back pressure as they likely have more over lap. I don't know about the latest 1400 Guzzi lumps, but I assume they are in the same ball park as the 8 valve motors and like some back pressure. But, you know what happens when you assume.
 
Smartleynz said:
Do Guzzi engines run better or worse with or without exhaust back pressure? My esteemed HOG owning mates reckon I should run Straight pipes "works on our Harleys". My thought is that Guzzis like a bit of back pressure? but I really don't know.
Click to expand...

It also doesn't "work on our Harleys". :)
 
Smartleynz said:
Do Guzzi engines run better or worse with or without exhaust back pressure? My esteemed HOG owning mates reckon I should run Straight pipes "works on our Harleys". My thought is that Guzzis like a bit of back pressure? but I really don't know.
Click to expand...

Ok, I will admit that since we dont know the cam profiles on the 1400, a direct comparison to a HD can't be made. That said, on my 1400, there is a quite noticeable difference when running with the baffles in on the Mistral exhaust VS running with the baffles out. Without is noticeably more "peppy" in the middle of the range...2500 - 5500 rpm. Idle speeds and smoothness seem unaffected either way.
Mine runs the stainless Mistrals behind Todd's (GuzziTech) full fueling mod system.
Also, Todd makes and sells several different muffler brands and sets for the 1400. If they, generally speaking, made the engine run worse, how many would he sell...?
YMMV
Kirk
 
Compare the blue line (stock) and green line (GT-Rx® Mufflers, and opened air box lid with GT fueling kit) and note the increase in torque and power. It could be argued that perhaps the GT-Rx® Exhaust provides more back pressure, but my ears are not agreeing with that thinking.

Upload 2016 11 28 8 47 52

BTW, the gold lines are the addition of the full GT fueling kit. Go for it!
 
The Harley guys are running open drag pipes which offer terrible performance (unless you're drag racing).
 
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