Extra exhaust - more or less?

[FJTillDeath]

Okay I was searching through the gallery and found that you can out twi exhausts on the FJ. My question now is how will it benefit the FJ? or will it benefit at all? i keep getting different answers so I decided to turn here. would having 2 exhausts add to or decrease the power in the FJ? eould it increase or decrease the speed in the FJ? will it sound better or worse (obviously good pipes are in the equation) and lastly would it use more fuel or stay the same to run? Then in addition just an extra question how many exhausts could you fit on an FJ? reaaly keen to see what answers i get also while I am at it what exhaust systems would be the best? In South Africa we only have 3 readily available exhausts being AirAge, Cowley and K&N (to my knowledge of exhausts available) but overall what would the best be?

[Harvy]

Okay I was searching through the gallery and found that you can out twi exhausts on the FJ. My question now is how will it benefit the FJ? or will it benefit at all? i keep getting different answers so I decided to turn here. would having 2 exhausts add to or decrease the power in the FJ? eould it increase or decrease the speed in the FJ? will it sound better or worse (obviously good pipes are in the equation) and lastly would it use more fuel or stay the same to run? Then in addition just an extra question how many exhausts could you fit on an FJ? reaaly keen to see what answers i get also while I am at it what exhaust systems would be the best? In South Africa we only have 3 readily available exhausts being AirAge, Cowley and K&N (to my knowledge of exhausts available) but overall what would the best be?

Mate, all year FJs had two exhausts OEM. If you have a single exhaust, it is an aftermarket item.
In general, the OEM exhaust system was more restrictive in the stock collector box and the exhaust cans. Aftermarket headers are required for most single cans (tho there is one that uses the stock header pipes I have seen on eBay in the UK......one of our members has this system that I know of).
In general, the more restrictive OEM system produced better power at low revs, however, this can be accommodated for with a four into 1 system with appropriate re-jetting.
A  4-1 system will in general produce more power, as it allows the exhaust gasses to flow more freely.
I suppose you could graft something like an old Honda4 CB750 set of pipes to the FJ if you wanted to, but I doubt it would produce any benefits, and would just increase the weight of an already heavy bike. Most of us modifiers are trying to decrease weight, not raise it.
Without engine work, I doubt that you would see greater speeds, as the engine will still only spin up to the same RPM. A change of gearing will produce better acceleration if lower gearing is used (at the expense of higher rpm for a given speed) or higher speed for given rpm if higher gearing is used.
There are many gear ratios available, and each generation of FJ used a slightly different gear set. I have been using 18 tooth front and 38 tooth rear sprockets for several years now, which is about as high a gear ratio available, thus reducing engine revs. If you want her to really get off the line quickly, you could use as low as 17/48 or something like that.

Harvy

[flips]

Okay I was searching through the gallery and found that you can out twi exhausts on the FJ. My question now is how will it benefit the FJ? or will it benefit at all? i keep getting different answers so I decided to turn here. would having 2 exhausts add to or decrease the power in the FJ? eould it increase or decrease the speed in the FJ? will it sound better or worse (obviously good pipes are in the equation) and lastly would it use more fuel or stay the same to run? Then in addition just an extra question how many exhausts could you fit on an FJ? reaaly keen to see what answers i get also while I am at it what exhaust systems would be the best? In South Africa we only have 3 readily available exhausts being AirAge, Cowley and K&N (to my knowledge of exhausts available) but overall what would the best be?

Hi FJt!llD3@th
ditto what Harvey said....
I changed mine from the stock system to a vance & hines 4-1 system (not the best system but one I could afford) and at the same time put a k&n air filter in the stock airbox with extra holes in it!,(I think the consensus on this site is the uni pod filters are better) and a dynojet jet kit(I think the general consensus on this site is the factory pro jet kits are much better!..they call the dynojet kit dynojunk!lol).I'm not sure which had the most effect but the combined effect was very noticeable.A very slight loss of power at low revs..under 2500rpm....2500rpm-5500rpm....good increase in power, 5500rpm up to redline...excellent increase in power!.The new exhaust is a good deal lighter.Here is a good site with lots of good info...
http://www.fjmods.btinternet.co.uk/Exhaust.htm
You might also want to think about ignition advance....
http://www.fjowners.com/index.php?topic=4292.msg37847#msg37847

Ride safe and cheers!
Jeff P

[andyb]

The dual exhaust doesn't necessarily reduce power nor increase low rpm power, but typically you're talking about an OEM system with slipons... the pipe size is the culprit.  Definitely adds weight, and allows you a lot more muffler area to get things quieter.

Now, if you were handy with a welder and had some Inconel tubing and some carbon cannisters laying around, you could do something spectacular....

Normal gearsets available range all the way down to 15/52 that I've found, but you'd have to be half mad to run that as the top speed would be under 110mph!  Front sprocket for the FJ is shared with the R1, and the rear is common to the YZF600R, that increases the available sizes off the shelf.  At some unknown rear size you'd have to modify the chainguard for clearance, and I'd guess that a 19t front would run into clearance issues as well.  Too small in the front can also lay the chain on the front of the swingarm a little hard and cause some wear difficulties there.  The more typical gearing range is a 16, 17, or 18t front with a 38-42 rear.  That's a plenty broad spread.

If you're racing it or really want some punch from it, remember that shifting takes time and the gains aren't quite linear.  The big air-cooled mill is happy pulling a little longer gears than you might think.  Stock's a hard compromise to beat for many people, but it depends on the riding you do.

[FJTillDeath]

So many option so many options!! really makes me wish I had more than 1 FJ to test all this on. To be honest i only really use my bike to ride to work and back everyday but when I get a chance i like to open up and hit the highway and travel to one of the nearby cities and back. genreally about an hour or 2 but i have never taken the bike more than 150km/h yet i still wanna get used to the speeds as my previous bike top spped was only 145km/h.