Bell's Banter 2021

[Paul D]

There's a lot more to understanding compression ratios than simple bore x stroke, as has been said.

Combustion chamber volume has to be known and factored in, but also, if you want to know the actual CR at cranking speeds, compared to the theoretical one, then cam timing also has to be factored in.

For example, if your inlet valve closes at, say, 70 degrees ABDC, then at cranking speeds, where the engine is turning slowly, you're not compressing anything (much) prior to that point. So you would then need to calculate how far up the bore the piston has travelled by that point, then subtract that figure from the actual stroke to find the effective stroke (for compression ratio purposes) at cranking speeds. Using that figure for the stroke in your calculations will give you a better idea of your actual CR at cranking speeds.

Wilder cams designed to deliver power at higher revs will, naturally, produce a lower (shorter) effective stroke at cranking, and therefore a correspondingly lower CR.

So from this, you can see that, with wild cams, and even with a high theoretical CR, your actual CR for starting may not be so high - may even be lower than the standard engine with standard cam.

So why, then, are high compression engines slow to turn over when cold starting you may ask? Well, as has been mentioned, it's more likely to be related to advanced ignition timing than compression ratios: tuned engines generally run more advance than standard engines, so at cranking speeds the spark is arriving effectively a little too early for what the engine wants at cranking speeds, and this early spark (and so early combustion) slows the piston travel as it approaches the top of the cylinder.

If you want to know for sure, then simply crank your engine with the ignition disconnected - if it spins faster than with the ignition on, then it's advanced timing that's slowing it down.

[VIVA GT]

This is all fascinating stuff guys, thank you & keep it coming

[Lancsbreaker]

Trying to remember last time I had to think about points, condensers and ignition timing...... I'd better do a crash-course retraining before I start on my Imp-based Husky My diesels don't seem to have these issues

[Gerard C]

Good "points" Paul. Thats why on Yank tanks they have a separate switch for the ignition. If they hadn't, very difficult to start with a fix advance timing settled at c 39°.

[S griffin]

Really enjoying the info from these stories. Interesting about the Yank tanks, not being able to start the car due to the temperatures makes sense

[Gerard C]

What we call a… hot topic!

[GORDON STREETER]

I think we ruined a couple of heads trying to find the optimum CR for my engines, the thing is that the combustion chamber shape makes an awful lot of difference to what you can get away with and you have to strike a compromise with ignition timing.
If you look into engine specs you will find that the most efficient petrol engines like hemi head designs don't run as much ignition advance as "conventional" ones like the old Ford Kent/ BMC heads. The old A series BMC engines in road trim were not the best at out and out performance and would take loads of advance without "pinking", and would still drive almost the same.
Modern multi valved engines with computer controlled fuel/ignition/valve timing are a whole new ball game though.

[Gerard C]

Fully agreed. We learned on the hard way that any TR engine and may be MG B can't achieve great figures at the dyno if you dont reshape the combustion chambers.
Yes again there are huge dissimilarities between engines, even though they have the same cylindre capacity, when it comes to set the ignition advance.
Another detail not to neglect is if you have, or not, double ignition. A good example is the old Porsche 2.0 litre found under the bonnet of the Carrera 6 too. More or less the same. But the Carrera one has two plugs by head which makes an important difference in terms of pistons head shape and SCR ratio too.

[Tel 911S]

And to go on a bit from what Gordon said about head design .
Combustion chamber shape can make a big difference in the power produced by making the flame spread more evenly through the fuel/air mix & also allowing a more optimum spark timing .

Taking that to the extreme , Fiat/Lancia had a Group B engine with the 4 valve head with an inlet & an exhaust each side .[ Unlike a normal one which has inlets one side & exhausts the other .]
The idea was that the 2 inlets at 180 degrees to each other would create a large " Swirl " effect in the combustion chamber & give a much better performance .
These engines are quite rare & not many people have seen one .

[Tel 911S]

Originally Posted by Tel 911S

And to go on a bit from what Gordon said about head design .
Combustion chamber shape can make a big difference in the power produced by making the flame spread more evenly through the fuel/air mix & also allowing a more optimum spark timing .

Taking that to the extreme , Fiat/Lancia had a Group B engine with the 4 valve head with an inlet & an exhaust each side .[ Unlike a normal one which has inlets one side & exhausts the other .]
The idea was that the 2 inlets at 180 degrees to each other would create a large " Swirl " effect in the combustion chamber & give a much better performance .
These engines are quite rare & not many people have seen one .

By some miracle I have managed to find a picture of one .
Plumbers nightmare with exhausts out from both sides of the engine

[Gerard C]

Thanks for the pic!
The Italian had really good ideas, I suspect Ferrari giving help or advice to Lancia. I used to drive a Delta S4, compressed and turbocharged engine, what a wonderful car it is.

[VIVA GT]

Originally Posted by Tel 911S

By some miracle I have managed to find a picture of one .
Plumbers nightmare with exhausts out from both sides of the engine

I was going to say that engine m ust have been a plumbing nightmare. Looking at the (small) picture the whole thing looks highly complicated and therefore so typical of the way things were going in Group B!

[Gerard C]

I wouldn't say the picture is small but the engine is…*Imagine the heat in the engine compartment.

[Gerard C]

Dont want to spoil the calendar thread just to say that when PA has to delay or, worse, cancel any event its really bad news. Those are very serious people standing always close to the governing body. As to ACO, just oblige to get rid of fifty people, I couldn't imagine that this will happen one day. Very serious people too, big money involved and close to the gov' too. I'm not sure they can stand another year of 24 H or LMC without spectators without any financial issue. Between nightmare and tragedy.

[Peter Mallett]

I agree Gerard, I don't expect many organisations will be able to stand another year of this.

[grantp]

Governments will take the opportunity to clear the decks for faster adoption of "Green" solutions. Motorsport is an easy target. Those enthusiasts that can afford it at the most costly levels may well be involved with running businesses that have to be seen to be "going green" so perhaps will not complain too much in public.

At the Pro end of the market the manufacturers are already heading rapidly along a road map that abandons traditional fossil power as quickly as possible. It seems that even America is on that track.

Also, unless huge investments are made soon in charging infrastructure, the "lockdown" mindset will be useful to re-train people to stay at home once they have bought their new EV because it is not safe to go out from a "health" Point of View rather than because they will not be able to go far without spending hours waiting for a charger to become available.

The blame for lack of use of an expensive investment can thus be placed squarely at the door of whatever rapidly mutating diseases take over from those we have been living alongside in the fossil era.

[S griffin]

We'll see what the government do, they have to be seen doing the right thing. Hopefully though motorsport can sort out the green issues themselves. There have been plenty of alternate fuels that are already in existence like biofuel, so just need to look into those more

Thing is motorsport is heading in the right direction with regards to reducing it's carbon footprint. The progress it has made in the last 10-15 years has been gradual, but it's getting there.

The problem is the unfortunate lockdowns have also reduced carbon emissions and now more people might be working at home for longer and keep emissions down after all this is over. And with electric cars on the rise, I expect to see more company cars run on electric in time. You have to say this lockdown has helped make people realise they can reduce their carbon footprint. You wouldn't have thought so, but it has

[Mike Harte]

What Johnson cannot afford (he is basically the government (or is it Carrie Symonds? ) - everybody else has to follow his lead) is to open up the country too early and then have to re-introduce another tranche of tightening of the rules if the infection rates go up again.

One only has to look at the Isle of Man. They opened up just a few weeks ago, but now they are going back into some form of lockdown as it is going pear-shape now.

[crmalcolm]

Originally Posted by Mike Harte

What Johnson cannot afford (he is basically the government (or is it Carrie Symonds? ) - everybody else has to follow his lead) is to open up the country too early and then have to re-introduce another tranche of tightening of the rules if the infection rates go up again.

One only has to look at the Isle of Man. They opened up just a few weeks ago, but now they are going back into some form of lockdown as it is going pear-shape now.

I might have missed something - but wasn't there talk a few weeks ago that lifting of the restrictions would be data-led?

IMHO, that is absolutely the right thing to do - but now I'm hearing it is all date-orientated in the roadmap?

[Tel 911S]

Originally Posted by S griffin

We'll see what the government do, they have to be seen doing the right thing. Hopefully though motorsport can sort out the green issues themselves. There have been plenty of alternate fuels that are already in existence like biofuel, so just need to look into those more

Thing is motorsport is heading in the right direction with regards to reducing it's carbon footprint. The progress it has made in the last 10-15 years has been gradual, but it's getting there.

The problem is the unfortunate lockdowns have also reduced carbon emissions and now more people might be working at home for longer and keep emissions down after all this is over. And with electric cars on the rise, I expect to see more company cars run on electric in time. You have to say this lockdown has helped make people realise they can reduce their carbon footprint. You wouldn't have thought so, but it has

The reduction of flights , transport & road traffic during lockdown has had no effect whatsoever on the amount of CO2 in the atmosphere , which has continued its slight rise through the year , proving that the vast majority of it comes from natural causes & the human contribution is so small as to be insignificant .
Also the amount of other emissions has not changed because traffic is only a very small part of the totals . https://airqualitynews.com/2020/09/0...n-in-scotland/

But in Germany ,https://notrickszone.com/2020/12/25/...had-no-impact/,
when a Transport minister did an online broadcast saying that a ban on diesels in cities was no longer being considered because the lockdown proved that they were not the cause of air pollution , his news report was removed & hidden in under 1 day because the Greens do not want people to know the truth.

[John Elwin]

Originally Posted by Tel 911S

The reduction of flights , transport & road traffic during lockdown has had no effect whatsoever on the amount of CO2 in the atmosphere , which has continued its slight rise through the year , proving that the vast majority of it comes from natural causes & the human contribution is so small as to be insignificant .
Also the amount of other emissions has not changed because traffic is only a very small part of the totals . https://airqualitynews.com/2020/09/0...n-in-scotland/

But in Germany ,https://notrickszone.com/2020/12/25/...had-no-impact/,
when a Transport minister did an online broadcast saying that a ban on diesels in cities was no longer being considered because the lockdown proved that they were not the cause of air pollution , his news report was removed & hidden in under 1 day because the Greens do not want people to know the truth.

We've had 20km/h speed limit reductions imposed on us temporarily this morning in this area because of a supposed reduction in air quality. This is being blamed on Saharan sand, wood burners & traffic so speed reduction won't make much difference to that lot!

[Mike Harte]

Originally Posted by crmalcolm

I might have missed something - but wasn't there talk a few weeks ago that lifting of the restrictions would be data-led?

IMHO, that is absolutely the right thing to do - but now I'm hearing it is all date-orientated in the roadmap?

That is what they keep telling us, but the reality is that it is Boris' poll rating that drives everything, up until the moment that he is forced to drastic action.

You only have to listen carefully to statements put out or explanations given during press briefings that the "experts" are very measured in just how much they actually agree with the decisions. I honestly believe that on most occasions that they would have wished to have moved earlier, and possibly more severely.

[VIVA GT]

All of the above makes me realise just how much mis-information is being fed to (or pushed) at us. But despite all of that, a lot of people are taking it all in without question...

[Tel 911S]

Originally Posted by John Elwin

We've had 20km/h speed limit reductions imposed on us temporarily this morning in this area because of a supposed reduction in air quality. This is being blamed on Saharan sand, wood burners & traffic so speed reduction won't make much difference to that lot!

Official UK Government data shows that over the last 50 years air quality has improved by 75% . https://www.gov.uk/government/statis...air-pollutants
Possibly a large amount of that is reduction of coal fires . But vehicles have cleaned up by huge amounts so that in most cases the air going into the engine is actually not as clean as the air coming out of the exhaust .

But of course the facts are not convenient for politicians looking for excuses to increase taxes on everybody , and motorists are the easiest target .

[S griffin]

I just wish people stuck to reliable sources and realised that some things on the internet should be taken with a pinch of salt. It’s no good falling for misinformation