fj1100 vs fj1200 exhaust

[tsak]

Does anybody know if the fj 1200 has more restrictive exhaust than the 1100?
Happy new year to all of us!!!

[Pat Conlon]

I have a set of my oem '84 FJ1100 muffler cans side by side with a set of '92 FJ1200 cans, and the openings appear the same, so I would say they flow the same. I can't see what's going on internally with the baffles. They are heavy critters.
Flow wise, the header tubes and collector boxes are the same.
The '84/85 1100's use a double walled steel header tube, the '86+ FJ1200's use a single wall stainless steel header tube.

Although heavy, the FJ1100/1200 oem exhaust system is quiet and flows pretty well, considering.
The increased power from an aftermarket 4 into 1 header comes at the high end of the RPM range due to superior flow and scavenging of gasses.
(along with saving over 40 lbs of dead weight)

Instead of going to a full header, keep your oem header tubes and collector box and you can get a bump in power if you go with an aftermarket slip on mufflers, and the save weight of the oem mufflers.
Here is a dyno plot showing  Delkevic slip on cans on a FJ
   

[giantkiller]

Wow 5+ HP just from slippons. I wonder if the supertrap slippons I have make any HP. I know that the dual supertrap slippons I have on the 89 sure sound great. I think they sound better than the full 4 into 1 stainless supertrap I have on the 1350.

[tsak]

If this dyno chart (plot?-sorry, for my poor english) is from delkevic i woulld be very sceptistic about those 5 hp...
Pat can you,please, measure the opening of the 1100 and 1200 exhaust?

[Pat Conlon]

24.5 mm diameter for both.

A 5 hp bump is about right for different slip on's I've seen.
Note that the majority of gain happens at the top of the RPM range. Not very noticeable for every day street riding.

[tsak]

Pat, thanks for the measurement!

[gumby302ho]

 I really do love the look of the black chrome stock exhaust on my ITX but it is unbelievably heavy, I did not know how heavy it was until I replaced it with RPM pipe&can. I also loved the sound of the stock exhaust, exhaust systems are tricky and you can never have it both ways unlike some new high end cars where the exhaust stream changes for what kind of selected sport driving mode, 2 strokes have the power valves that help promote power all through the rev range. I dont think the H2 has such an exhaust. My first header was on a 4 1/2 hp Tecumseh that was in my FOX mini bike, It had a nice bend and flange and it was even shiny.Best small engine pipe I have ever seen, my mini got nicked and I did get it back but the pricks took the header.