Engine tuning

AndyW

AndyW

Hero member
G'Day folks: I thought it might be best to start a new thread on which we can discuss the merit of different engine tuning techniques and approaches and further deliberate (if necessary) Clem's engine's demise.. the original bearpit of a thread can be left to the bears :D

After I holed a piston in a 1070 Mini Cooper S on the M1 many moons ago I rebuilt the (modified) motor and took the car for Dyno tuning. I'd set the ignition up with a strobe and balanced the carbs with a primitive though effective vacuum gauge. Carb needles were as recommended by Dave Vizard's Mini Tuning Bible: plug colour looked ok throughout normal driving conditions. Tickover wasn't brill..

Compression was around 12:1 (Longman big valve / ported head)
544 Half Race (rally?) cam
twin 1 1/2 SU carbs.

Guy on the dyno said the mixture was WAY too weak.. took the needles out and filed them away to almost nothing... He wasn't interested to see the timing marks for the ignition.. simply slackened off the distributor (having checked points gap etc) and, at high tickover (2000 rpm) from a fully retarded position simply rotated the distributor to advance the spark until the revs stopped climbing. He then backed it a little to see (or hear) that the revs fell a little and then returned it to the beginning of the peak rev point and tightened the distributor into position. He told me at the time that he was tuning the ignition to suit the fuel. The Dyno result was one of the best they'd seen for a while. Difference on the road was amazing.. much more tractable and as if someone had fitted a turbo too.. Oddly enough the fuel economy improved too (from 16mpg to almost 20 :o)

The dyno operator was Harry Ratcliffe.. probably the best Dyno tuner in the North of England in the 60s thru 80s... Ever since then I've tuned my engines the same way and haven't holed a piston since..

So.. I'm wondering if modern (crappy) fuels require a more retarded ignition setting than the rotor scribe marks on our bikes would indicate. My T160 (still in the UK) was designed for 5* fuel and runs horribly on unleaded at the standard timing settings.. I've backed off the ignition a tad and it runs fine if a little down on absolute power and top speed. same goes for my 850 Guzzi..

Anyone else tune their ignitions by ear?

 
I sort of do Andy but not the way you do it.

I don't strictly believe the timing marks but they are my starting point. I listen for pinging of course. If I do get a batch of fuel that creates an issue I just use more revs and leave it in a lower gear for longer. The faster piston speeds mean a faster venturi velocity.

I do ensure the ignition advance is working within it's parameters. Pinging on an old Guzzi 850 may mean the advance springs are tired. (one of the usual suspects.)

I also check the annealing line on the plug's earth strap. That also tells a story.

Rarely do I change much on just one piece of information as I don't have the luxury of a dyno set up. Once I decide to alter the static timing then that is the new standard. I just reset it to that every service from then on unless I notice an issue.

Just remember that if you can hear pinging due to timing it is way too advanced. Take it back till it stops and then a bit more. It can also be a sign of too hot a plug, too lean a mixture or too much compression for the grade of fuel.

I have a similar attitude but just go about it slightly differently.

Cheers

Rod
 
Shades of my youth.

I was schooled by one A Jackson of legendary Abbot Racing fame, best head man
in UK. Built FF ford motors, hot rods (Duffy Collard etc etc etc) and any race engine
he could lay his hands on. Combustion chamber volumes were almost scientific but
carbs and ignition all done by ear.

Back in the 70s and 80s I made more than a few bob balancing E Type carbs. and my
TR4A had the sweetest motor around..........ah those were the days, no proper job,
no home but lots of travel and sometimes a pocket full of cash.

PS tool of the day was a length of garden hose.

Thats it off to ebay to buy an old Ford with a crossflow :D :D :D :D :D :D
 
I tuned the ignition on my Le Mans 850 the best way.

Threw the 2kg lump of shit called a distributor into the bin and fitted a Sasche - runs a frikking treat.

But then again, I am not a mechanic.
 
Davo said:
I tuned the ignition on my Le Mans 850 the best way.

Threw the 2kg lump of shit called a distributor into the bin and fitted a Sasche - runs a frikking treat.

But then again, I am not a mechanic.
Click to expand...

Off Thread!!!!!!!!!!

I personally know of one LM II owner who lost his bike due to a wasted spark backfire. It ignited the K&N filters and the bike burned to the ground.  :o

I understand the difference between a single and 2 point pick up system.

If you are happy with your modification then I'm glad. Personally I think that an ignition system that runs just almost every car and only has a spark near the top of a compression stroke makes sense. I also don't have an issue with changing springs in a distrubutor every 3 decades or so.

Back to Topic:

I learned a lot about combustion when I was trained to blow things up in the Army. I understand different explosives/mixtures have a different VOD (Velocity of Detonation) and this affects what occurs. Its not that dissimilar to dual plugging older bikes depending on design.

As I wrote earlier, I don't hold the timing marks as gospel. Fuels have changed that much that they cannot be expected to be perfectly correct any more.

A lot too depends on what fuel you use. Higher RON ratings can cope with higher compression ratios but calorifically they are about the same. Good EFI systems can adjust but the sort of stuff you get in the bike just doesn't, O2 sensor and all!

I run 91 in the Alpino as it has a 8.5:1 ratio. It is a happy little beast with that but I don't advance the timing past the marks.

The burn inhibitors they use in higher RON fuels are an easy way to test a bike. If you think its running to advanced put in a higher RON and see how it goes. If you think its too retarded then  drop the number. When I was riding around the USA 2 years ago on a SP1000 the highest RON fuel that was available was 91.  :o You could buy down to 83.

Just my take on fixing, maintaining and riding 30 year old technology without a paranoia issue.  ;)

Rod, not going to Guzzi heaven and it looks like I'll need to ride the outside track of the Laverda enclosure too.  8) Lets not get into how the Morini faithfull see me either.  :o
 
Dizzies dont need springs, only time you need retard is for slow running. Whack it full advance
and lock it up, self tapper used to work fine :D :D :D :D :D
 
Lucky I don't run K&Ns then. As I said, not a mechanic so I hate playing with points and timing marks. Set the Sasche once and just ride it. Also trying to get the weight down as much as possible.
 
andychain said:
Dizzies dont need springs, only time you need retard is for slow running. Whack it full advance
and lock it up, self tapper used to work fine :D :D :D :D :D
Click to expand...

I'm with Andy....but I'm not a mechanic.

I do however build race motors for a (poorish) living...and over yea, these many years, I've always preferred to do the final ignition timing settings on track. It helps if you can get good feedback from a rider - it was of course much easier when I was doing the testing myself...But a good experienced ear and careful plug readings work pretty good too.
 
if the fueling is on the money and if one has access to a dyno
a run is done to find peak torque rpm
then the engine is held at that rpm and the timing adjusted
until additional advance fails to increase power reading
then the ign is backed two or three degrees
as a bonus fuel economy improves

now, if this amount of advance causes detonation issues
it can be too much compression or inefficient combustion
or a combination of both

morizzi's analogy is a good one
different fuel qualities will have an effect on combustion
and therefore require different ign timing
here, one cannot reasonable expect that the fuel you get one day at the pump
will be of the same composition as the last time one fueled up
now our best timing found on the dyno won't necessarily work for each time we fill up
and its really hard to hear the onset of "knocking" under load with something like a true jota
so we have to rely on some stds, based on experience (and local available fuels), for our bikes
this is where known to work curves, from the selection in the DMC or sachse, are used

in the old days a single ign point was used but  wasted a lot of fuel at any engine speed
away from where this single point was ideal

with modern engine mgt systems one may well find 40 degrees plus timing at low speed/high vacuum
but you can't do this with just springs or a single selectable curve based on rpm
but when you add a manifold vacuum source, as cape has done to his ignitech, you get a 3 dimensional map
where timing is adjusted based on rpm and engine vacuum for greater efficiency
more power and increased fuel economy

andy, i'd bet your old mini was one hooligan ride  :)
 
but when you add a manifold vacuum source, as cape has done to his ignitech, you get a 3 dimensional map
where timing is adjusted based on rpm and engine vacuum for greater efficiency
more power and increased fuel economy


I would love to see a dino curve of Capes work,the increase of fuel consumption is a very impressive given but more power would push his work to where there would be an orderly Que to do it.
]
 
Hello Lads,
                  Much of this thread top has been covered over the last 10 years or more,  as applied to the Laverda motors.  The premise that cylinder fuel  load and ignition timing are interactive is true as. For instance a retarded spark looks rich on a plug read,  a high value advance looks lean.  At some point you hold one or the other fixed, ( cylinder load or ignition timing ) and vary the other for best motor operation.  For many the choice is a simple one.  Set the ignition curve to a best fit for the motor in question. Vary the fuelling to obtain best performance.

  The notion of advance the ignition until it ( the motor ) blows and then back it off a couple of degree's is a discredited school of thought.    32DBTDC for safe easy motor operation,  some Laverda triples will take 36-38DBTDC for noticeable road power delivery.  The IIS Laverda curves were developed on 120 and  180 motors, on the road up and down hills,  the 180 more tolerant than the RGS 120.  Took test rider and myself years to sort best fit curves,  not convinced other ignitions are based on same long road testing,  resulting in best of fit curve.

  Relax,  be kind to your motors,  whats a few HP to endangering your motors,  for a not obvious few hp difference on usual road riding.  Like taking granny for a ride on a R1 whats the point?

  Regards to all,  John
 
Had 2 crazy motors, one rusty Anglia van with a 1000 Cosy Screamer under the bonnet
and an Escort van with a hot Mexico lump. Great fun with loads of axle tramp.

Shit where have those fun days gone?

:( :( :( :( :(
 
On the track (stage rallies) the car was slow and hopeless (mb that was me!): on the road it was a monster.. no power below 4 1/2 thou so had to give the traffic in front of me a 50 yard start else I'd burn the clutch or run into them.. in contraflows (40mph) on the motorway I'd have to use 2nd to keep the revs up and the radiator cool... hopeless.

Years later a mate gave me an old mini he'd inherited from his father's estate and hadn't used for 5 yrs..  full of petrol though took awhile to get going but when it did.. oh my.. went like shit off a shovel. Bog standard mini 1000 too... he was still racing 'bikes back then and used to tip out his unused fuel into the parked up mini: it was full of AvGas.. That was the moment I realised how much money I'd spent trying to make Minis go fast in my youth..

Andy's right.. life back then was a right old laugh... where did we go wrong?
 
OK, so usual on the Laverda is 32?, maybe 36-38?... but it depends on the CR also, don?t it?
If the Ign.Timing is too late, esp. with bad Fuel, the engine starts to knocking if the CR goes up to 10:1, on the other Hand, if it fires to early you risk to burn a hole in the piston...
I wonder what differend curves make sense with digi ign.?
 
jotacorsa said:
if the fueling is on the money and if one has access to a dyno
a run is done to find peak torque rpm
then the engine is held at that rpm and the timing adjusted
until additional advance fails to increase power reading
then the ign is backed two or three degrees
as a bonus fuel economy improves
(and then if you want to be rally on the money, you re-check the fueling and if altered, re-check the timing again after that. Ad infinitum until happy) JM

now, if this amount of advance causes detonation issues
it can be too much compression or inefficient combustion
or a combination of both.

morizzi's analogy is a good one
different fuel qualities will have an effect on combustion
and therefore require different ign timing
here, one cannot reasonable expect that the fuel you get one day at the pump
will be of the same composition as the last time one fueled up
now our best timing found on the dyno won't necessarily work for each time we fill up
and its really hard to hear the onset of "knocking" under load with something like a true jota
so we have to rely on some stds, based on experience (and local available fuels), for our bikes
this is where known to work curves, from the selection in the DMC or sachse, are used

in the old days a single ign point was used but  wasted a lot of fuel at any engine speed
away from where this single point was ideal

with modern engine mgt systems one may well find 40 degrees plus timing at low speed/high vacuum
but you can't do this with just springs or a single selectable curve based on rpm
but when you add a manifold vacuum source, as cape has done to his ignitech, you get a 3 dimensional map
where timing is adjusted based on rpm and engine vacuum for greater efficiency
more power and increased fuel economy

andy, i'd bet your old mini was one hooligan ride  :)
Click to expand...

Spot on!
Only way to set an engine up 100%  99.9% correct is to set all parameters "Under Load" we have easy access nowadays so no excuse for skipping this!  your engine needs a massively different fuel and ignition setting when under load as compared to just revved up in the workshop. This is not to say that someone doing it that way would not get it right, or a lot better than someones initial guess or factory settings used on a newly "improved" bike but it's unlikely they would "optimise" it in the way you can on a dyno or rolling road.

Julian
 
PS.
Yes life was great back then, but I for one didn't have any money to spend on said life!  Had as much fun but had to settle for less than I wanted.  Still do and always will to an extent but life is a lot easier nowadays  ;)  and toys more plentiful!  :D

Julian
 
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