Exhaust advice needed...

[Adam_Winstone]

Hi all,

It has been a while since I've looked through exhaust graphs to check out performance of some of recent year's offerings and hope that I might benefit from your experience/insight of pros/cons of the new options out there. I'm after a fast road use (perhaps even touring if there is enough low rpm power) pipe, rather than a pipe that can only perform whilst screaming at high rpm.

I'm looking at possible options for a reed 230 motor that is running 125 transfer and 183 exhaust durations (29 degrees of blowdown... please note that I'm after exhaust advice for these timings, rather than any comment on the barrel's porting), which should give an rpm/power peak of approx. 8500 rpm (8-9) so I'd like to find a pipe that services this peak but does not do so by sacrificing too much low rpm power... nor limit rev on too much! OK, I understand that this is looking for the holy grail of pipes and an unrealistic spread of power throughout the entire range, however, better to have high aspirations

Variable ignition timing will claw back some low rpm power and keep things cool at higher rpm but the pipe graphs that I've looked at show the typical delivery of power at one end of the rpm range or the other, with very few doing much of both. Without chopping an exhaust up to introduce a variable tuned length, as shown to work so well by one sprinter in recent years, what are my options?

I've had a quick look at some dyno graphs available online, however, they all tend to lead in direction of specific products, rather than give an objective comparison across the range. Scootering's previous pipe comparisons for Honda 205 and TS1 were fantastic but these are now somewhat out of date, with access to dynos meaning that lots of new pipes have been developed since.

So... what do you know?

Thanks in advance.

Adam

[holty]

hi adam,
is this pipe for your case induction engine, i wonder if a pm fat mamba might give you the torque for touring and the top end power that your after, im going to build my own exhaust for my rotax conversion.

holty

[Adam_Winstone]

Hi Holty,

Thanks for the reply.

Yes, it is for my CI motor, which I am gradually refining my configuration of to suit my purposes. Currently I am running 4.8 with a Fran Race and am very happy with where I am to date but I'm experimenting to make sure that I'm not simply accepting what works and potentially missing out on a better configuration that I might not have tried. Having my initial setup dynoed by Jerome did confirm my suspicions of where I could benefit from various changes so I've since fitted the flowed crank that Sean Brady did some cracking work on, fitted a Mikuni fuel pump to get over the fuel starvation at low fuel levels that I had become aware of, machined a head to up the compression so that the corrected ratio is more appropriate to the slight/mild porting work that I've done. As it stands, the bike is a really nice ride (I know, I hear the 'if it aint broke' comments!) but I'm sure that I could get more power at lower revs from launch, and at the same time I'm pretty sure that it would pull another tooth on the front [a pal of mine took it for a short spin on Tuesday night (club meet) and he said that he was surprised how soon it came on the power].

Looking at the various pipe graphs about, I'm surprised how many people are using 6k peak pipes on TS1s when the standard TS porting wants to make power at higher revs. Obviously, you can change a pipe to get back low rpm or encourage over-rev but that doesn't change a barrel's porting to work in harmony, rather, it introduces a limiting factor to try to get around an issue. Not surprisingly, the best TS1 tunes either lower durations for touring or raise exhaust duration to suit transfers and to allow the motor to reach the higher RPM range, which is a better 'fix' rather than 'bodge' (please note that there is nothing wrong with a standard TS1, far from it! They are superb kits).

Anyway, back to the point... what I'm after is a pipe that has a good spread of power and can do a fair bit of both. I've tried a good range of pipes over the years but have not kept up to date with the rapid exhaust development of recent years. The Fran Supertourer is the last pipe that I bought, which works very well on another of my bikes, but I know that it loses out at the bottom of the range to many of today's road pipes... not that I'm looking for the rev limiter that many road pipes have to be to get their low RPM figures.

Cheers for now and good luck building a pipe, full credit to you. I know how bad my welding is so that's not something that I plan on trying (lol)!

Adam

[holty]

hi adam,
hows about a picture or two of the carb and inlet, just to see how youve done it, im using the readvalve part of an rb barrel to make my rotax into readvalve, im trying to get the reads as close to the crank as poss, theres not much room where the bumpstop fits on the case, and the bumpstop on the frame.

holty

[Adam_Winstone]

Hi Holty,

I can't take much credit for the general layout arrangement as this is based on development work that Ron Moss has done for a crankcase induction version of his Avanti TT3 kit, with me taking that as a starting point and running off with it to have a play about with it (lol). As the layout is Ron's work I'm not really wanting to post it for all to see (that would be up to him), however, PM me your email address and I'm sure that he wouldn't mind me sending you a couple of photos that might help you understand what I've done and where.

Adam