Dyno questions

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acotrel said:
I'm certain there is still opportunity for improvement. From memory my current needles are 6dp6, the 6 series needles are used in VM round slide Mikuni carbs from 30mm to 38mm choke size. here is the list :
Sounds like you need to put it on a dyno, and give it a big program of trying things out. !!
Great words from John on what he did and how it panned out, BTW.
 

johnm

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acotrel said:
John, what fuel are you using and what are you permitted to use ? I'm sorry if my comments are old-fashioned, however my brother and I have been doing this stuff for a long time without the help of a dyno. I still have a problem relating throttle opening, fuel demand, and gearing for different circuits. I usually base my adjustments on improvements in performance around the three tight bends and short straights at the back of Winton Motor Raceway. If I can get around there really fast, I know I will be OK in races on that circuit even if I lose a bit at the ends of the longer straights.
Firstly I need to repeat that these days I no longer live in NZ and am not racing because I need to pay for my retirement and therefore Im working in challenging places for the money. So everything I reported about is three years old at least.

95 % of the tuning above was done with Amal Concentric Mk 1 carbs using NZ Mobil 8000 pump gas which can be bought at most large Mobil stations in NZ. (97.5 octane RON non leaded with ethanol up to 10 %) for a machine built to NZ pre 63 clubmans rules (NZCMRR)

I read many comments on this and other sites about how ethanol reduces power, causes problems, bad running etc etc.

But I tested Shell No. One race fuel bought in 20 litre drums at a huge price against Mobil 8000 pump gas and no difference whatsoever could be seen on the dyno. So I have been using it for about 8 years. (Remember I only have 10.1 :1 compression ration.

In the last two years we raced we also entered the NZ Senior TT for 500 bikes. In this race the rules allow more modification and I used methanol. All I did was buy the Mk 1 methanol conversion kit. Needles, needle jets, float bowls, float needle etc. Installed a main jet 2.6 times bigger than the petrol one (2.3 is the theoretical size but I wanted a bit of lee way - since your a chemist you will understand the 2.3 ratio. Im a geologist and my chemistry is seriously bad!!!!!). Used a chrome slide. Opened up all the flow lines to get enough fuel delivery. Backed of the ignition and raced it.

First year we got second behind Paul Dobbs and the next year second again behind Andrew Stroud. Converting to methanol was the easiest thing I ever tried !

I have never tested methanol on the dyno. I did not have time. I rode the bike myself for a few laps of Puke. Set the ignition timing using the methods described by Jennings in the papers I listed in another thread and sent the bike out for 15 racing laps of Puke.

Any possibility this could be of use to you?

http://victorylibrary.com/MIK-BT.htm
 
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johnm said:
Ok I just have a normal PW 3 cam and if you go here you will see the Mike Hemmings spec sheet that has been posted by someone whose name I have forgotten - sorry!

Beleive it or not my cam is installed 5 degree retarded. Most (all) engine tuners will advance a cam on a race bike over a street bike- say around 5 degree. On a Norton this can be done by remeshing the timing chain and timing gears. I have not found a reliable vernier yet and either just accept the approximate setting or these days I use one of my collection of about 5 cam sprockets which all have slightly different settings.

Which is along way of saying if your working on a Commando I cant help with advice on cam advance except to repeat what the books say. John

Re; “Believe it or not my cam is installed 5 degree retarded. Most (all) engine tuners will advance a cam on a race bike over a street bike- say around 5 degree. On a Norton this can be done by remeshing the timing chain and timing gears.”

Another way is to either obtain or make one and insert an offset woodruff key. HTH :)
 

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Bernhard said:
Re; “Believe it or not my cam is installed 5 degree retarded. Most (all) engine tuners will advance a cam on a race bike over a street bike- say around 5 degree. On a Norton this can be done by remeshing the timing chain and timing gears.”

Another way is to either obtain or make one and insert an offset woodruff key. HTH :)
Hi Bernard.

On any Norton twin it is not neccesary to make a offset key unless you want to do steps finer than 5 degree.

Simply moving the chain one tooth on the cam sprocket and then remeshing the timing gears back or forward will change the cam timing in 5 degree increments.

This uses all the standard gears and sprockets.

Given the forces which go through the camshaft I do not want want to rely on anything less than the full thickness of the key. I also have a collection of cam sprockets which have slightly different locations for the key and this does the job as well.
 
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I softened the cam sprocket and had two extra keyways broached in at random. The combination of those with changing the chain mesh gives very fine adjustment. I've got an idea where the cam timing should be on a race bike. The table of cam timings in Tuning For Speed for various bikes is useful, if you can remember what the bikes were like. The 1959 AJS 7R was excellent, as was the 350cc Gold Star BSA of that year. (You need to think how those timings were derived). Some people get fanatical when they buy a race cam - the manufacturers' specified timings are usually not critical, slight variations of a few of degrees don't usually change performance much , except for the revs where things happen.
I've never used petrol for racing, only methanol - petrol is too hard on engines. It can thin the oil and kill the oil pressure when motors get too hot. I run standard (9 to 1 ? ) compression, and the methanol still works. The temperature of the intake tract has no relationship to the compression ratio. I've even used it in four stroke motors with comp ratios as low as 7 to one.
Rohan, as far as measuring improvements on a dyno is concerned, I suggest the relationship between the data and on track performance with various throttle openings and gears must still be established. The dyno can only ever be part of the story, ( I recognize it's value as far as that goes). I suggest the fact that there are twelve listed variations in the tapers of No 6 Mikuni needles for different applications supports that opinion. They are divided into three groups depending on use - normal, competition and racing. The same size Mk2 Amal carbs have only three optional needles listed, so what are we talking about ? The needles are interchangeable for 34mm VM Mikuni, and MK2 Amal carbs. Which type do you recommend I should use and what is your tuning procedure ?
 
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Aco, when running methanol on standard 9 or 10:1 compression, what are your ignition timing considerations compared to petrol?
 
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acotrel said:
Which type do you recommend I should use and what is your tuning procedure ?
My approach to this would be to put them on a dyno and find out which suits you best....

I seem to recall reading that there were something like 42,000 possible combination of
jets and needles in a particular model of mik, and there were 8 for a similar size and function amal.

acotrel said:
The 1959 AJS 7R was excellent,
The 7R was an OHC shorter stroke pure race engine, so what works for that and what works in a longstroke ohv engine may not be entirely related ?
At all...

acotrel said:
The temperature of the intake tract has no relationship to the compression ratio.
I'm not sure what the context of this sentence is, it seems to have landed in the middle of a different conversation. ?
But the temperature of the incoming air-fuel has a lot to do with the overall charge density of what you are trying to pack
into the cylinder, so has considerable influence on what the power output is going to be.
Engines on hot days in thin atmospheres make less power, considerably less, than engines on cold days with 'thicker' air.

If you are only running a low compression 850 motor, its no wonder it doesn't have a lot of go ?
 
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Rohan,
'If you are only running a low compression 850 motor, its no wonder it doesn't have a lot of go ?'
It has got plenty of go, however I cannot believe it is possible to fluke the optimum. Methanol properly tuned makes any bike go faster. Our guys used it in the 50s, and when they raced in the UK, they found the Brits bikes on pump petrol were as fast as theirs had been In Australia on methanol. What it means is that our guys bikes at home were poorly tuned but fast enough to win. To get the most out of methanol or petrol, it must be run almost as lean as possible without doing damage. I'm certain there must be opportunity for improvement in using the various Mikuni needles. The variety of tapers is relatively enormous. My bike is fast enough to win already, however why would I not try the alternative needles , if there is potential there ? This stuff about running methanol rich and it still gives good power is true, however over the years there have been some really dumb things done with it. If you get it wrong, the bike will still be almost as fast unless you are way off the mark. The last liitle bit trimmed off makes a fairly big difference , most people don't go there. It is why my brother wins most races that he enters - he is very careful when he jets his bike - it can get expensive very quickly.
I bought the Mk2 Amals with the alcohol kit - as delivered the jets were a joke.

TBolt,
I am using 34 degrees ignition advance with methanol on standard comp. (I usually add about 4 degrees to the spec petrol timing, and tune to it .) And I'm using long velocity stacks on the Mk2 Amals. You don't need high comp to get benefit from methanol, it works on latent heat of vaporization (charge temperature), however it gives you the opportunity to use high compression. I never go there , you need a better ignition system when you get to 14 to one, and it is then common to retard the timing a bit towards the petrol timing .
 
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Rohan, jetting a big four stroke for methanol is extremely different from jetting a two stroke for it. You can get it wrong on a four stroke, and the bike will still run. Two strokes often stop dead. With a two stroke, you can have it near perfect , and it can still seize as you shut the throttle while you are really flying. On a four stroke, it is difficult to damage by leaning off the needle jet, unless the motor fails to run on the main jet because the tip of the needle is obstructing. If the needle jet is too lean, the bike usually becomes a pig to ride, and it is obvious that you've got it wrong.
I agree that you are correct in your concerns about leaning off the carburation, however on a four stroke seizing and burning pistons usually come from main jets being wrong, or changing a muffler for a megaphone without changing the jetting everywhere . For highway riding your mid-throttle jetting might be more important if you habitually drone down long highways at high speed with the throttle half open.
 
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TBolt, If you want to try using methanol here are some settings:

Mains - start with Amal 700, you will probably eventually come down to Amal 670.

Make your own needle jets from brass hex using number drills and size drills'

I started with 0.117 inch, and finished at 0.116 inch when I couldn't get it to cough by lowering the needles. Needles are 6dp6 Mikuni. Slide cutaway is no 3, pilot is the normal Amal for Mk2 s

As supplied the alcohol kit for the commando Mk2 Amal has 0.120 inch needle jets and X and Y needles - ridiculously rich.
 
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acotrel said:
For highway riding your mid-throttle jetting might be more important if you habitually drone down long highways at high speed with the throttle half open.
I don't actually know too many folks (who are still alive) who habitually cruise down the highway WFO.
Not faintly interested in 2 strokes, keep them away from the discussion.

Methanol gives best power with good compression.
You should be looking for at least 12:1 or even 14:1 to take good advantage of it.
Its its antiknock properties at higher compression ratios and its engine cooling properties when run rich in hi-compression engines that make it a racers dream fuel...
As it is now, your bike is less than roadbike Combat spec tune ?
Johnm's 500 could make more hp on the dyno ?
 
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!2 to 1 or 14 to 1 compression ratios would be great, if you could achieve them without a high crown blocking the flame front, and the corresponding increase in piston weight. All the theories are great, however they often lead to an expensive top end motor which can be useless on tight circuits. As I said , after tuning two strokes, jetting a four stroke for methanol is a soda, with a two stroke it is extremely nasty. Perhaps you should extend your areas of experience ?

Rohan, I suggest that if the combat motor was reliable, the 750 commando would have ended up as a much faster bike. Do you think I should move the power band of my bike further up the rev range ,rather than the less expensive fattening up of the mid range and increasing the overall gearing ?
 
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acotrel said:
I suggest that if the combat motor was reliable, the 750 commando would have ended up as a much faster bike. Do you think I should move the power band of my bike further up the rev range ,rather than the less expensive fattening up of the mid range and increasing the overall gearing ?

Giving it more compression should give it more power - everywhere ??
A stock 850 motor was quite a low compression beast.

The Norton proddy racers ran something like 12:1 compression, didn't they.
That was with flat top pistons ??
Its 'just' grinding a mm or 2 off the lower face of the head, and flycutting the pistons to ensure they can't kiss a valve ?

If you reread the threads on bearings, it was evident that the Combat was fitted with inadequately specified bearings.
What was in them was very little different to the early 500 dommies !!!
Once they were specced up to the best available (at the time), no more troubles.
With 20/20 hindsight, they should have done that BEFORE putting them out into the marketplace....

With modern bearings, you don't hear of these Steve Maney big cc engines having combat-like troubles...
 
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Aco, so if you advanced the ignition timing 4 degrees from petrol standard, jetted up to ideal methanol jetting and all else being equal including comp ratio (IN A 4 STROKE);

1) What average increase in HP and torque would you expect?

2) What increase in fuel volume consumed would you expect?

This is beside the obvious benefits of a cooler running engine.
 
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In theory, merely burning methanol instead of petrol produces very little extra power.
Methanol has about half the calorific value of petrol, and you burn (roughly) twice as much.

Where the big increases come from is running much higher compression ratios and stronger cams.
Methanol is much more reluctant to detonate with higher compression, with the added bonus that the engine gets extra cooling (from the latent heat of vapourisation, as the liquid goes to gas) so the extra power doesn't lead to heat problems.

I've run methanol fuels in little aero engines, pumping out 200+ bhp/litre (this was a while ago) , and they can do this day in day out with methanol cooling.
If on petrol, they'd melt ??
There are petrol classes though, don't know much about them ?
 

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TBolt said:
Aco, so if you advanced the ignition timing 4 degrees from petrol standard, jetted up to ideal methanol jetting and all else being equal including comp ratio (IN A 4 STROKE);

1) What average increase in HP and torque would you expect?

Around 5 %

2) What increase in fuel volume consumed would you expect?

2.3 times

This is beside the obvious benefits of a cooler running engine.
I dont agree totally with Rohan. Yes the main benefit of methanol is that it allows you to run higher compression without detonation - say 12 or 14 :1 if you can build the engine. But even without increasing compression the extra volume of methanol consumed does give you some gain in Hp of about 5 %. And hence torque because bhp= torque *rpm/5252.

It also cools the engine and inlet tract so you may get some gain that way as well. (density). On the down side its poisonous.

Races one hour apart on the same day switching pump gas to methanol dropped lap times at Pukekohe from 1 min 11.8 sec to 1 min 11.2 seconds. This improvement was consistant and repeated at three different meetings.


A couple of other things. Im a bit consious that all the above could be seen as bit show offish and I would definilty like to aknowledge the role of the rider Tony McQueen in all this. He's in his mid late 40s now but when young raced and beat Aron Slight in Ozzie production racing (Slight has won Suzuka three times, 13 world super bike wins and finished runner up in World Superbikes twice). Tony also has had good duals with Andrew Stroud who won Daytoan several times on the Britten plus the world Bears championship. He's beaten Chris Swallow within the last three years and Chris took two second places at the Manx last year. So the guy is a good rider. And he can handle a pretty knife edged bike. His own bikes are H2 Kawasakis on methanol and he has exactly the issues described by Acotrel. Sometimes he sets better times on tight tracks with the Dommie at 50 bhp than his H2 with about 90 bhp. Which really gets him unhappy !!!!!!!!!!!!!!!
 
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With the H2s on methanol, it is probably better to only lean off as much as you really need to stay competitive. And that is probably pretty much in the 'safe ' zone. My brother's kawasakis only do short four lap races on speedway. A 750 two stroke triple is bad enough on petrol without the added anxiety and expense of methanol, and I would never go that way on the bitumen. I don't think I would ever try to race an H2 with the standard frame. An H2R is a lot better than the road bike. 90 BHP is not much fun if the bike is tying itself up in knots, and with a converted road bike you usually don't have the necessary gearbox. It is easy to scare yourself shitless with stuff like that, at least a commando is usually sane.
 

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acotrel said:
90 BHP is not much fun if the bike is tying itself up in knots, and with a converted road bike you usually don't have the necessary gearbox. It is easy to scare yourself shitless with stuff like that, at least a commando is usually sane.
Exactly !!! Hence the slower lap times than the Dommie :) Its pretty exciting watching him trying to hold the H2 act together on a street circuit like Wanganui.) Some where on the web are some videos. Ill see if I can track them down. Earlier this year he got his act together and did pretty well at Paeroa on it. But he was with pre 82 bikes as well so ran about 5 th on the road. Like I said he's a pretty fair rider !!
 
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Dyno's of various types are for the more urbanized rich and lazy dudes and has been shown not to relate all that well to actual track performance. Not saying dyno's ain't useful though just taken with a grain of salt to work out more in real use. I won a bet with race engine V8 builder on my van's engine set up more for propane than gasoline CR/spark and cam degree wise. The fuel evaporator was rated to supply up to 360 hp but engine only showed upper 350's, till I paid $250 for another run with the jet boat cam advanced one half of one degree 0.5' and it put out 366 hp for me to collect $50 bet discount and change the attitude of reluctant builder on my off the wall combo. I would of detected this by street run times but way easier to diddle cam outside of van's engine bay. Point being that little bitty changes can make big differences in a hi strained engine set up.

One of my desires is to see what the Big D in Texas at low humid altitudes dyno shows in comparison with Jim's Comstock's dyno high up in dry conditions, but only after down and dirty road tests in rural Arkansas, which has a few 1/4-1/2 mile straights not too far away w/o much on either side to jump at you to crash or ticket and impound. Peel will be set up as her own rolling road dyno, G meter on bars and monitoring temps and O2 wide band.

Explosions occur in two ways, one by deflageration which is below super sonic speed/expansion and two by detonation which is over supersonic barrier, in the hi pressure-temp states in chambers. Tuning to slight detonation makes best power if engine can take it. Water and methanol can be sprayed in to tame detonation while still increasing gasoline pressure-torque amounts burnt but not adding more mass of gasoline that can slow the flame fronts and reduce power out. I'm thinking of dosing some hydrogen preoxide into the spray mix to see if it gives more power w/o blowing up.
 
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