Portmap

[andy bush]

Anyone got a port map for the 1-s, or a link to one ?

just seeing how they compare to other strokers i got......maybe some extra ponies by seeing what they use.......

cheers

Andy

[mj43]

Andy

try this http://myweb.tiscali.co.uk/teamsparrow/kr1stune2.htm

MJ

[andy bush]

Cheers Mark,
a very good read it was too..........


Andy

[dirk]

hi,

not a portmap from the S but one from the KR1; RGV (i think the first RGV) and TZR (2MA)



regards
Dirk

[KR-1R]

... thanks DIRK have been looking for that magazine comparison picture for ever (my Cousin had the issue and never got a copy for me)

...the Sparrow link lead me to KNIFE EDGING mod...

I dont believe knife edging the bottom of the tranfers port does any good at all - BAD MOVE

ask yopurself why aeroplane wings are tapered on the trailing edge and round at the front - smooth flow

this is like the air flow into the cylinder is from the bottom of the cases around the dividers and into the cyclinder

IF YOU KNIFE EDGE THE PORTS the flow becomes disrupted

TRY HOLDING A STANDARD BARRELL UPSIDE DOWN UNDER a FLOWING TAP
- YOU GET QUITE A CLEAN FLOW THAT SLINGSHOTS INTO THE BORE

now do it with a KNIFE EDGED modded barrel and the water strikes the sharpened edge and goes all over the place - NOT EVENLY SPLITTING/distributing between each tranfer duct.



my opinion is the could make a motor unpredictable in its power delivery - it may not affect power on a fully W.O.T. (dyno test) but delivery under normal conditions where transient throttle openings and and abrupt load changes might affect acceleration in fuel CHARGE.

It is the last thing I would try on a motor after ever other porting trick has been performed and not before a dyno test had been done to prove the other mods first.

It was considered a trick in motocross about 20 years ago - and then dropped like hot cakes?

comment?

[the-elf]

The flow within the crankcase is turbulant in any case mainly due to the pumping effect of the crack flying around and the piston pumping the gas so there isn't any smoth flow to worry about in the first instance. The mod has been proved on a standard engine in a before and after state on a dyno.

[mj43]

....
I dont believe knife edging the bottom of the tranfers port does any good at all - BAD MOVE

ask yopurself why aeroplane wings are tapered on the trailing edge and round at the front - smooth flow....

Not going to agree or disagree - but I will say whereas I am not trying to design an aerofoil to provide lift, I do have a problem keeping my barrels down

[TwoStroke Institute]

KR-1R you are in fact 100% correct, bulk flow is never fast enough to benefit from knife edging. I ditched knife edging after stern lecture from your national treasure in 2t tuning W****Y who does the exact same thing with the water.

[corky]

this has been talked about a few times on this forum in the past and if i remember correctly the outcome was that a turbulent airflow is better as it keep the fuel/air/oil mixed to allow for a better/more even burn in the combustion chamber.
4t tuners inc F1 boys when gas flowing heads go for rough surfaces and have built in parts to cause a small degree of turbulance to keep the fuel/air mixed.

as we know gas flowing is a very complex area and for all applications they should be treated separatly, as mj says aerofoil sections are different than cylinder porting in there requirements and objectives,,,

anyway this is a bit deep for me at the moment as i am on a lads holiday in pattaya thailand....

say no more........

[TwoStroke Institute]

Air flow in transfer ports is the same as air flow anywhere else. I have seen Aprilia RSW, TM and Pavesi Kart cylinders all of which have over 50HP per 125cc cylinder, none have knife edged dividing fins from the factory.Trust me this (like case stuffing) is very old hat.

[mick abbey]

Air flow in transfer ports is the same as air flow anywhere else. I have seen Aprilia RSW, TM and Pavesi Kart cylinders all of which have over 50HP per 125cc cylinder, none have knife edged dividing fins from the factory.Trust me this (like case stuffing) is very old hat.

This is true You get a better flow by rounding of the wall between the transfer ports ( you don't have sharp edges on an plane wing it wouldent fly)

Mick

[mj43]

Other than a few, most base their two stroke tuning on folk lore.

Lift the exhaust port, raise crankcase compression, knife edge the transfers are all favourites. What works and doesn't on a KR takes time to find out.

Best I have seen out off a KR is 32hp per cylinder which is way short of the 50hp + claimed by some engines. However, that comparison is subject to differences in dynos and you need to look further than just hp.

The KR is a production engine built to a price. The ignition was designed to protect the manufacturer from warranty claims and as such is the main limiter to making hp - it limits the rev ceiling. So what you can do with a KR (without spending mega bucks) must be within limits placed by the manufacturer. Change the rev ceiling you will need to change expansions porting etc.

Having said that you can get very good power out of a KR using stock ignition. As a direct comparison on the same dyno no 250 has got anywhere near my engines at the same rpm, i.e. in terms of BMEP (a measure of engine efficiency) the KR engine knocks the spots off the RGV, TZ, TZR, h***a NSR and RS. Not saying it makes more power, all the above machines rev between 1000 and 2500 rpm further and do ultimately make more peak power.

On the same dyno the h***a RS250 made 72hp v my best at 64hp. The h***a torque figure was nearly 2ftlb less than the KR but it revved to nearly 12,500 rpm whereas the KR peaked at 10600. The RS doesn't pass the KR power curve until the KR starts dropping off around 11,000 rpm.

I have yet to see an RGV curve on the same dyno beat the KR. I think the best RGV (not seen the curve) made a hp more but at nearly 12,000 rpm and the torque figure was about 4ftlb down on the KR.

I will post the pictures of barrels out the 64hp engine at the weekend they are a little different to those shown

[TwoStroke Institute]

True MJ BUT the RS h***a/Yamaha TZ weigh 100kg, got big fat tyres, fully adjustable suspension,stiff chassis etc etc etc.Not many bikes(maybe 500cc 2T mxers) will highlight ones short comings as a rider, as fast as a GP 250.

[mj43]

Ok 64hp barrels note the differences - sorry about the photo I am no photographer. The piccy of the previous barrel is about 4 to 5 year old tuning. This piccy is tuning at least two years old - no knife edge web is much thinner than stock. No piccies of the current barrels yet (may be in a year or two) but they are an evolution further.



This is a comparison of a KR (above barrels) against a healthy h***a RS250.


The h***a ability to rev a further 2000 rpm is its strength. All the h***a rider needs to do is put a bigger back sprocket on the back and for the same speed he will gain an extra 20% drive. Basically he is accelerating in 3rd gear while I am in 5th - so though the KR is a more efficient engine higher BMEP the h***a is a better race engine (albeit much more highly stressed because of the extra revs).

Now if I can get the KR to rev like a h***a - look out KTM

[ScottaKR]

Now if I can get the KR to rev like a h***a - look out KTM

Have you thought about switching over to a Zeeltronic setup to release those extra rpm, or would the bottom end not cope with the strain?