Web moped2.org




Date: Sat, 07 Oct 2000 19:18:58
Subject: Re: Info on Tomos & Columbia
From: Mike _____
Reply to author   Post followup (list members only)   Back to index   Subscribe to the mailing list   Unsubscribe from the list  

i don't think the govenor on the cdi is 8000 because i have seen very
expensive tachometers redline at about 9500 RPM stock on a flat road. i have
gotten my 2000 targa up to 43 down a hill ( a very very steep hill). and
this guy even says, 98 sprint, 40-43. the numbers don't lie. and all these
speedometers aren't wrong.

>From: Marko
>Reply-To: moped@topica.com
>To: moped@topica.com
>Subject: Re: Info on Tomos & Columbia
>Date: Sat, 07 Oct 2000 14:43:52 -0700
> >Before we go any further, I would just like to say that *officially
>speaking* Tomos A5 moped engines were designed specifically to be
>"tuning-proof". They are governed by the intake and exhaust system, thermal
>unit, ignition system and final transmission.
> >Now, theory is the only objective means of estabilishing the facts here..
>Calculated maximum speed at 8000 RPM limit for a Tomos with 13.3426 2nd
>speed total transmission ratio and a tire diameter of 548 mm is exactly 62
>km/h (38.75 mph), wether you like it or not.
> >You have to realize that the CDI in fact HAS to have an RPM limiter of some
>kind to pass the "Tampering Test" obligatory for homologation of the engine
>on the US and most other markets.
> >There is a possibility that your speed measurement isn't 100% correct, and
>in regards to the statements the dealer has made, they can be considered
>false (even provided he has a <1995 moped). Again, the theory shows that an
>engine of a moped with such aerodynamic properties as a Tomos A35 would
>have
>to develop power exceeding 4 kW (5.4 HP) to achieve this speed, which is
>BTW
>at approx. 10500 RPM. Unfortunatelly, even though the 70 cc cylinder has
>bigger cross-sectional area of the ports as the stock cylinder, the power
>is
>limited by means of the cross-sectional area of the two crankcase transfer
>port openings (again, the "Tampering Test" compliance..).There is also an
>additional awkwardness of the 70 cc cylinder- it lacks the third T transfer
>port due to the non-reed valve design, additionally lowering the transfer
>port cross-sectional area.
>The engine simply cannot pump so much propellant through these two port
>openings to achieve 4 kW output, even though it has longer port opening
>timings after the tune-up.
> >Think of it this way- Imagine two halls (presenting the volume under and
>over the piston), connected to one another by three hallways (presenting
>the
>three stock transfer ports). Each hall also has a massive wooden entrance
>(presenting the intake and exhaust port).
>Imagine 100 people walking through these two rooms (presenting the "stock"
>propellant flow dynamics at 6500 RPM). They go into the first room through
>the massive door, divide to three groups, go through the three hallways and
>exit through the massive door in the second room.
>Now imagine 275 people walking through these two rooms approx. 60% faster
>(presenting the "tuned" propellant flow dynamics at 10500 RPM). Of course
>you'll need to modify some stuff.. So you demolish the two wooden doors and
>build bigger ones. You demolish two hallways and build wider ones, but
>leaving the entries into the hallways unchanged. You also ruin the third
>hallway in the process, don't ask me why :-). You even enlarge the second
>room..
>And here they go, the crowd rushing through the awsome entrance and.. Oops,
>they're stuck at the two hallway entries. End of story.
> > >i don't think your right, because i know many people that have gotten
>their
> >tomos with the new CDI to go 40 plus, i am one of them. i have even
>talked
> >to a dealer who got a true 50 out of his with the stock cdi and a 70cc
>kit.
> >It is only implemented as a governor, but yes, it is also a "seizure proof"
>feature if you like. The speed improvement depends on your intake/exhaust
>tuned lenght and cylinder porting, but mostly depends on the resonance
>range
>of the intake/exhaust system. For anything over 8000, the intake manifold
>is
>way too long as it was designed to provide low end torque rather than high
>rev power (Tampering Test, yadda, yadda,..).
> > >Yeah I would also like to agree that you don't need to have a different
>CDI
> >to go above 38mph. I have a 98 Sprint with Bi-turbo and it will go 40-43
>mph
> >on flat ground. However, I do have a question about the CDI RPM limiter.
>Is
> >this limiter part of the governing system for the us market like the
>s-shaped
> >stock exhuast was or it it just there to prevent the rider from harming
>his
> >bike. If I replaced it could i expect any speed improvement leaving my
>bike
> >the way it is?
> >list.


Share information about yourself, create your own public profile at
http://profiles.msn.com.

Reply to author   Post followup (list members only)   Back to index   Subscribe to the mailing list   Unsubscribe from the list  



Forums at Moped2.org Privacy policy
Moped2.org Home My other sites

Home   Contact
Wikipedia Affiliate Button