Author Topic: For all you 'revheads'  (Read 1692 times)

MartinJG

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For all you 'revheads'
« on: January 25, 2018, 01:09:09 AM »

Ever wondered what is going on under your bonnet.

Then this should interest you.


Sadly, us poorer cousins on 8 pluggers can only wonder what we are missing...
« Last Edit: January 25, 2018, 01:11:07 AM by MartinJG »

culzean

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Re: For all you 'revheads'
« Reply #1 on: January 25, 2018, 09:30:40 AM »

Ever wondered what is going on under your bonnet.

Then this should interest you.


Sadly, us poorer cousins on 8 pluggers can only wonder what we are missing...

The 8 valve twin spark engine is much underrated and IMHO much more suited to Jazz than the i-vtec (have driven both).  The 1.8 vtec in the Civic is great because of extra 500cc.

http://asia.vtec.net/Engines/lseries/index.html   (go back to home page and 'technical articles' for some really good write-ups on Honda engines).

Everyone knows that power is 'the size of the bang x the number of bangs per minute' - petrol engines have a greater rev range than diesels but people still think diesels are somehow 'more powerful' (mainly because of the low down torque) which is IMHO where the 8 valve i-dsi scores over the i-vtec in Jazz because the i-vtec is pants below 3K.

The fact is that diesels have long stroke engines (to get the very high compression ratios) which means larger crank diameter (and larger heavier engines) and more torque, but less revs (piston speed and flame propagation limits).  So as I have said before petrol engines are capable of producing much more 'power' than diesel engines, (look what happens when you put a turbo on a 1 litre petrol engine) but diesels without a turbo are just a slow revving low powered lump.  The gearbox sorts out the torque that you get at the driving wheels.  I have attached PDF of a great article that someone did on Civinfo forum explaining torque and power.

I read somewhere that the 'ideal' capacity per cylinder is about 300cc to 350cc - above that size efficient filling and flame propagation suffer.

[attachment deleted by admin]
« Last Edit: January 25, 2018, 09:40:35 AM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Kenneve

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Re: For all you 'revheads'
« Reply #2 on: January 25, 2018, 10:16:16 AM »
I read somewhere that the 'ideal' capacity per cylinder is about 300cc to 350cc - above that size efficient filling and flame propagation suffer.

I wonder where that puts the 1908 Itala Grand Prix car (Floretta) which had a capacity of 12 litres, 4 cylinders of 3000 cc each!!!
It developed all of 100 Hp at 1800 rpm, a slightly different rev range to the Jazz!!!

MartinJG

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Re: For all you 'revheads'
« Reply #3 on: January 26, 2018, 06:10:19 PM »

Ever wondered what is going on under your bonnet.

Then this should interest you.


Sadly, us poorer cousins on 8 pluggers can only wonder what we are missing...

The 8 valve twin spark engine is much underrated and IMHO much more suited to Jazz than the i-vtec (have driven both).  The 1.8 vtec in the Civic is great because of extra 500cc.

http://asia.vtec.net/Engines/lseries/index.html   (go back to home page and 'technical articles' for some really good write-ups on Honda engines).

Everyone knows that power is 'the size of the bang x the number of bangs per minute' - petrol engines have a greater rev range than diesels but people still think diesels are somehow 'more powerful' (mainly because of the low down torque) which is IMHO where the 8 valve i-dsi scores over the i-vtec in Jazz because the i-vtec is pants below 3K.

The fact is that diesels have long stroke engines (to get the very high compression ratios) which means larger crank diameter (and larger heavier engines) and more torque, but less revs (piston speed and flame propagation limits).  So as I have said before petrol engines are capable of producing much more 'power' than diesel engines, (look what happens when you put a turbo on a 1 litre petrol engine) but diesels without a turbo are just a slow revving low powered lump.  The gearbox sorts out the torque that you get at the driving wheels.  I have attached PDF of a great article that someone did on Civinfo forum explaining torque and power.

I read somewhere that the 'ideal' capacity per cylinder is about 300cc to 350cc - above that size efficient filling and flame propagation suffer.

Interesting article. It does support the view that the iVTEC is better suited to higher revs than the DSI. That said, diesels still have that 'efficiency' card up their sleeve though. Crack the emissions and they are back in business although I cannot ever see them solving the carbon particulates problem in a hurry. Nature of the beast I suppose although I associate one source of smoke as being inefficient burn of fuel. I know it is not quite that simple but there is no question that 'low blow' turbos work very well with compression ignition after allowing for that tell tale puff of turbo lag which is usually the result of a heavy foot.

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