Needing Air

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Even if the gauge is not accurate for actual pressure reading d/t barely deflecting off zero, same gauge can still be trusted to show differences reliability to indicate changes in the direction being sought.
 
Hi rwalker.
A 0 to 0.03 Mpa gauge for the same needle point arc is more discriminating and would place the needle more central to its movement compared to the one I currently own and used. I agree with hobot that the gauge in question shows significant and comparable difference for the items tested. The experiment is now concluded: 'engineering science' requires you replicate the set-up (perhaps with better gauging) to confirm or rebutt my conclusions.
Ta.
 
needing said:
Hi rwalker.
A 0 to 0.03 Mpa gauge for the same needle point arc is more discriminating and would place the needle more central to its movement compared to the one I currently own and used. I agree with hobot that the gauge in question shows significant and comparable difference for the items tested. That experiment is now concluded: 'engineering science' requires you replicate the set-up (perhaps with better gauging) to confirm or rebutt my conclusions.
Ta.
Click to expand...
 
hobot said:
Needing this Dellorto article belongs here for insightful references on stuff to diddle in Amal-ish type carbs.
Just scroll till images stop ya in tracks to read whats going on.
http://www.danskkartingcenter.dk/dellorto_manual.pdf
Click to expand...
Oh hobot.
Now you have gone and done it! Your link contains within 'the missing link'.
Clarity of purpose prevailed (once I closed my dropped jaw). Woohoo.
More to follow: maybe by PM.
Ta.
Edit: parts ordered and now in transit!
 
Hot diggity dog. I did not study the long article but enough I think I know what opened your foaming fluid mind. Youknowwho and I still think you are a jerk but so what this is fun following. No use of this in my factory 72Trixie nor next Peel but do want to put past Peels pisser prime combo togther again so may have incentive as old school modified Norton parts were all she contained. Pisser off because rational part was constantly shocked-angery it had so little control over emotional throttle hand. Also scared the pee out of me at times too.

Btw they do have electronic triggers for paintball air puffs with valve to control the pulse.
 
Youknowwho and me just like to see accurate science quoted.
Keep it straight, no problemo.
Make it up, big problemo

!!
 
Now , what do you make of this :

John Heayley's explanation :
". I understood that by cutting the spray tube you disrupted the normal Bernulli/venturi effect of the spray tube at low throttle openings. That is, it would present a softer signal (difference between atmospheric and manifold vacuum) to the needle jet and air intake around the needle jet. But why do we need to soften the signal one the needle jet/air at low throttle openings?
The answer came from Kevin Cameron. Kevin is considered by some to be a world class 2 stroke tuner. He is a hero among many Canadian snowmobile tuners. He spent years, along with Kawasaki factory engineers devloping their TZ750D race bike.
He explained that a 2 stroke piston-port engine (not rotary port) has a short, but sharp drop in vacuum as the piston opens the intake port. The piston is going up, which creates a vacuum in the motor's crankcase. This vacuum builds until it is released, in what he calls a "pop," when the piston finally opens the intake port. This short, but intensive decrease in vacuum would draw too much fuel from the needle jet if the spray tube was not modified (made less effective). This effect one the spray tube is most apparent at low throttle openings.
Without the aid of on-board computers an engine tuner is stuck witht the fact that his selections must be a compromise. He is trying to get, what some tuners call "flat" carburation. That is the carb delivers the proper mixture from idle to full throttle. There is no radical variations, as presented to 2 stoke tuners with the "pop"
He must do thisto meet rider styles, atmospheric changes, enviromental rules, and any anticipated modifications to the bike. One such change is Norton's use of the stepped spray tube to lean the bike out at low throttle openings to meet EPA requirements. Other times, such as the sloped spray tubes in the T150, to effects on intake manifold pressure caused by exhaust systems." (quote )

I have just read some of this long post regarding spray tubes e.t.c. when I noticed this ;
re; “The answer came from Kevin Cameron. Kevin is considered by some to be a world class 2 stroke tuner. He is a hero among many Canadian snowmobile tuners. He spent years, along with Kawasaki factory engineers devloping their TZ750D race bike.
He explained that a 2 stroke piston-port engine (not rotary port) has a short, but sharp drop in vacuum as the piston opens the intake port. The piston is going up, which creates a vacuum in the motor's crankcase. This vacuum builds until it is released, in what he calls a "pop," when the piston finally opens the intake port. This short, but intensive decrease in vacuum would draw too much fuel from the needle jet if the spray tube was not modified (made less effective). This effect one the spray tube is most apparent at low throttle openings.””

Everybody knows that the TZ750 was a race bike with a full blown engine tune ( OK -it was detuned from the TZ700)
As far as I am aware these bikes didn’t have pilot jets to obtain a tick over-so the question is was Kevin Cameron referring to this particular race engine or standard road bikes in general :?:
 
A day at the dyno doing science in the 21st century.
Phase 1 mods before and after then some phase 2 mods.
Screenshot from the one of the runs shows maximum rpm and speed achieved after the horsepower hump.
The horsepower graph shows a before run with all phase 1 mods onboard compared to the 20 minute later after run with the removal of the airflow channel as the only change. A huge difference (i.e. increase!) at low (around town) speeds as theorised but also with a smaller yet significant top end increase.
The later run for phase 2 (top end mods) also shows promise. More to follow when shop-bought components arrive.
Ta.
 
Very interesting !
Be nice to see some actual hp numbers ?

Only 7969 rpms.
What cam have you got in there....
 
BTW, you didn't happen to give it full throttle at low rpm, and watch how the engine and AF ratio responded.... ?
 
Re: Needing Air and knowing the flow

A little bit more of science stuff...

The top graph is an earlier run to compare to a run yesterday (centre graph).
The bottom graph is how I predicted on 21 July that the run yesterday (05 Aug) should turn out.
The additional blue and white horizontal lines are to clarify scale.
The centre graph shows that improvement is needed with throttle slide 1.5 to 6.5mm open and near wide open.
The plan: replace stepped spray nozzles with flat tops and fit larger main jets.
Ta.
Of course, I could have derived all this from a plug chop or two, not! :D
 
Rohan said:
BTW, you didn't happen to give it full throttle at low rpm, and watch how the engine and AF ratio responded.... ?
Click to expand...


Hi. I'm also interested in the answer to Rohan's question.

I have done numerous runs on a race bike with megaphones.

One of the biggest issues with the dyno is to find an operator who has a brain, mechanical sympathy , some knowledge of the limitations of older technology (ie that the bike fuel and ignition is not computer controlled!!) and will actually listen to what you are asking.

All the operators locally insist on starting a run at low rpm by slamming the throttle wide open and I can never get them to smoothly open up the throttle as you might do on the track accelerating smoothly out of a corner.

I would be very interested in the response of your modifications for the two situations.

Smoothly opening the throttle versus slamming it open.

By the way. Im following this closely and when I return home to NZ will certainly trying these ideas out on the race bike.
 
Hi johnm.
Thanks for the interest.
As you know, each run costs $ so I have focussed on my own test program for my mods.
On page 10, there is a video of the last run in that series and as you can hear (more than see) Tony rolls the throttle on quite smoothly.
I did have the ignition timing set at 30°BTDC but found on the dyno that 32° gave an extra 2 horsepower. Even cold, it still starts fine with my phase 1 mods so I go with that for the time being.
As of today, the main jets are now 260s (were 220) as I only have 200, 220 or 260 in the cupboard. My theory is at 7K+ rpm I would probably want the mix to be richer than leaner. The next series of runs will define the mid flow for that jet. I don't go there much out on the real road so it is really academic. I have a long haul (1000km) ride planned for next week to trial the full suite of phase 1 mods.
I have also changed the spray nozzles for the flat tops and expect the transition from the pin holes to then be leaner because the nozzle lip is now higher a la hobot's assertion and my bench trials with the vacuum cleaner. Personally, I see the variety of spray nozzles available as modern day tuning options. The historic evolution is interesting but moot. If rohan was to specify a test program I would be more than happy to quote (here, we call that putting your money where your mouth is). :D
Ta.
PS: I perceive the 3 phases will provide smooth idle to WOT through all transitions with a rolling throttle. A snap-open throttle on a carby bike can only work if there is a throttle pump. Constant flow at each opening is easy, it is the changes to air speed with opening transitions that make it tricky.
 
2 degree increase in ignition timing giving a 2 BHP increase is worth the thread on its own Needing!

I will be returning to the Dyno to continue my playing around with different exhausts and will certainly try and ensure adequate time and focus to play with ign timing (kinda f***ed that bit up last time).

In the past (as I've mentioned before) I have personally found old Brit bikes (predominantly Triumph and Nourish powered things) to be rather insensitive to relatively small changes in ignition timing. But this is my first such playing with a Norton, so we shall see!
 
Fast Eddie said:
2 degree increase in ignition timing giving a 2 BHP increase is worth the thread on its own Needing!

I will be returning to the Dyno to continue my playing around with different exhausts and will certainly try and ensure adequate time and focus to play with ign timing (kinda f***ed that bit up last time).

In the past (as I've mentioned before) I have personally found old Brit bikes (predominantly Triumph and Nourish powered things) to be rather insensitive to relatively small changes in ignition timing. But this is my first such playing with a Norton, so we shall see!
Click to expand...
Yep, it surprised me. I had expected the movement would be back toward 28°.
Ta.
 
While changing to the flat top spray nozzles I tapered their bore from both ends so that the original ID (for a 2mm length) corresponds with the top of the needle jet (this lip also tapered to a knife edge). Not expecting a discernible difference, just thought a venturi profile couldn't hurt. Dyno booked for next Tuesday.
Ta.
 
The rough'n'ready, not-to-scale, graphic representation i.e. sketch-up of a carby below should explain how the five (5) throttle openings progressively activate the AMAL Mk 1 jetting systems. My throttle slide seal innovation is shown.
Those that get it, do: those that don't, probably never will.
Ta.
 
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