8 replies to this topic

[jsp]

just wondering if the bigger bore front pipes make much difference
to a 4rts performance ?

jsp

[sectiononecleaner]

just bought one and have fitted yet, but i beleive they give you bolt on power at bottom end, plus the mitani is lighter and looks good. Try it. £125 i think i paid. I also have bought the silencer to get the full benefit which makes the power really smooth as well as good torque. Give it a try shortly when i get new bike, will post on my thoughts more then. I think your best bet is try it and make your own opinion.

[GII]

Yeah, mate of mine bought a Mitani one, it was great, engine was much sharper off the bottom, I beat him every week 'till he realised and took it off again.

Do you really need more power?

[Woody]

Am I the only one then, who fitted a Mitani front pipe and couldn't tell a scrap of difference in performance? - it was exactly the same as the original pipe.

Fact is I never expected any difference from 2mm increase in diameter, it wasn't bought for performance so I wasn't dissapointed. I bought it purely because I hated the tuppeny ha'penny look of the original front pipe on a £4.5k bike. Has to be the cheapest, ugliest front pipe on any bike I've ever seen.

[hop blip and a jump]

It can't look as bad as the hideous front pipe on the new gasser 4t!!!!

[windlestone]

I can't tell the difference between my standard pipe and my Mitani pipe either.
Blue bits on the mitani pipe look geat though

[Ludde]

Just a little comment: You can get performance benefits from the Mitani pipes IF you remap the PTB. I had both the Mitani pipe and silencer on and thought that it was really good, until I rode a bike that was exactly the same as mine but with the standard exhaust on... The standard bike was sharper on the bottom end, not stronger but it reacted quicker than mine. I messed around with the mapping and got mine better but not really good as it could be.

So I bought the 280kit from Mitani to get more torque from the bottom end, and the bike became worse, really bad. It didn't pick up revs as I wanted, it felt slow and weak So I sent a email to Mitani wondering if they had a map that cure my problem. And they sent me a map that didn't look like the other ones I have. It really transformed the bike, now its really sharp of the bottom end and its torquey. Now I can use 2nd gear even in the tight stuff without working the clutch to much.

I have some ideas about what has changed see if you can use it on the standard bike, I will try to check if I am right tomorrow on my dad bike with everthing standard and a Mitani silencer on. Will let you know what I find out.

Edited by Ludde, 30 November 2007 - 07:10 PM.

[Carl Ekblom]

I think 2nd gear riding really is needed under slippery conditions. I´m looking forward to hear about the findings on Ludvigson Senior´s bike .

I have put the rear restrictor back and I think it improved low end torque slightly. I also have retarded the ignition curve slightly at low revs and at small throttle openings (fuel unchanged). I don´t think this made it stronger at low revs but it made it more tractable in 2nd gear under slippery conditions. I have tried the mild program supplied with PTB but I didn´t like it at all.

Generally speaking, and I would say that this is valid for all four stroke engines, a larger bore exhaust pipe will move the torque curve upwards in the rev range. It has to do with gas speeds which is needed to avoid exhaust gases from changing direction and go back into the cylinder head. Actually, on highly tuned racing engines with big bore pipes I have seen the exhaust gases changing direction and coming out from the carb inlets when the throttle is opened at low revs.

I have read that the 07 cam is different from 05/06. Anyone knowing if this cam will improve 2nd gear riding?

Carl

Edited by Carl Ekblom, 30 November 2007 - 10:12 PM.

[Ludde]

So here is my findings. It looks like when you use a bigger bore exhaust it is better to retard the ignition at low revs. This seems to make the bike breath better and this makes it sharper. Most have something to do with the later ignition giving a higher pressure in the cylinder when the exhaust valves open, thus pushing out the exhausts. I knew that this tuning effect could make a difference, but didn't think it would be this much.

Anyway, the old man like the new map, which is almost the same one I got from Mitani. At low rev it is a bit more calm than before but dad wants it like that. I think the ignition is a little bit too retarded for the standard bike but it works on the 280kit, but then the 280 has higher compression ratio.

A little tip for those who have problem starting their bikes: try advancing the ignition at idle and below by 2 or 3 degrees, seems to make it easier to start