Supercharged!

dont drop your C/R down too much if your gonna use a good ECU, cause a good tuner can tune out most pinging
snip ...

sorry..but that was the story 15 years ago....
when we had petrol with a decent octane rating
and if you couldn't find it...you went to the airport...
oh...for avgas..

these days.....
even the Optimaxes and Synergy fuels
can't handle too much in the way of a DECENT compression ratio
even V8 supercar engines have this problem too...

I have tried...and I have tried and tried...
to get modern engines (with ECUs Motecs etc etc) to run
WITHOUT holing pistons or pinging or detonation
on anything more than a max of about 10.5:1

some turbo engines... i couldn't get to run
on more than about 8psi..without the 'rattles'....
not very conducive to making hp!

It seems modern 'alloy' engines are more affected by poor octane ratings of our fuels....
the older cast iron engines (think Falcon and Holden 6) will take more ignition advance and more compression
than anything with alloy in it....(which is most modern engines)

and don't even think about the 'cheap' fuels from Singapore
a standard BA falcon or Vy Holden 6 will sometimes rattle
and our petrol companies and regulators (that is, the government)
couldn't give a shit...

and I know..i have tried and given up...

cheers

Yeah, what with that? Fact: the higher the octane rating, the cleaner the fuel burns. Bikes aside, I consider myself an environmentalist. But governments and and EPA are kidding themselves if they think our modern fuels are good. We use poluting inefficient fuels while the Epa books you $1000 coz your exhaust is a bit loud for other road users.

On the compression ratio, a general, but very effective rule is that for staic compressions of 10:1 you can safely use as low as 100 octane, 9.5:1 /95octane, 11:1 110 octane etc...
The older iron headed engines resist knoking best. This is coz the iron conducts or draws heat awy much more efficiently. But then our clevo is extremly tempirmental and we've emptied the sump out the pipes as a big flame a couple of times now. It is impossible to hear knocking in water when the engine is solid mounted.
On the other hand, there are exceptions. Our 392 will run on a 50/50 mix of Lrp and premium all day. It has a comp of 11:1 The explanation here is that the combustion chambers are huge, dead smoothe and flow at an insane rate. These where cast in 1954 (again, how far have we really come) and have to be seen apart to be appreciated. With a bare head on the bench with no valves in it, you can literally see into the inlet port, across the combustion chamber, and straight out the exhaust port. We are also running pistons with no fly cuts. This all means that heat gets out quicker, and there are no corners or points in the cylinder to get particularly hot and promote detination.

But there is an almost fool proof answer. I'll have to check the ratios, and heat ranges of the plugs required, but you can buy toluline (the base of most additives) straight from Shell. There are three down sides.
1. the stuff will seperate from the fuel if let sitting over night.
2. It can turn to jelly when left in small quantities, ie. carby bowls.
3. fumes are not good.
We solved the first two easily though. We run a small efi pump in each tank drawing from the bottom at one end and returning straight back in at the top at the other end. We run these for about 5min each morning to stir it all up before the engine fires. These are switched off one stirred coz driving stirs it up enough. We also run a tap just below the fuel rail wich is switched off at the end of the day and let the engine epty the bowls. You should have a return line to the tank to make this safe though. We have never had an engine fail using this stuff yet, and it's cheap(ish).
It's a bit of messing around but well worthwhile if you get it right.
Otherwise, you will need to back compression of to as little as 7:1 if you're gonna run real boost. This also means you can get a bigger air fuel charge in as well.
Athough some electronics do have anti knock systems, they only save your engine from self destructing. While they are operating, retarding ignition etc.., they are robbing you of power, big time. Surely the goal is to make reliablbe and predictable power?
Do you home work and do what YOU feel is right and logical. If it doesn't make sense, keep thinking and talking untill you come to an answer that you know is atleat safe for pride and joy.

OK, seeing as this has turned into a big discussion of engines etc. it has reminded me of one of those things I've pondered on a long ride. Do valves have to be round? What would be the implications of changing their shape as far as gas flow/swirl versus getting a good seal?

...and back to the original topic, I was just looking at the Two Wheels magazine webpage and it looks like their latest edition has a story about the blown VTR http://www.twowheels.com.au so it might be worth a look Matty. I reckon if he can get one to fit into a VTR, you could get one into a ZX7R

OK, seeing as this has turned into a big discussion of engines etc. it has reminded me of one of those things I've pondered on a long ride. Do valves have to be round? What would be the implications of changing their shape as far as gas flow/swirl versus getting a good seal?

geez Mick....
guess I go back to Mechanics 101....naaah failed that....
but the topic of Induction Theory...I passed....
so here we go...
no... valves do not have to be round .....
but they are round because of what they sit in....
valves sit in a passage (we know them as ports..)
and a port is normally circular 'O' or sometimes like an '0'
and why?
the most effiecent structure for the movement of gas or liquids
is a cylinder ...because it has the least amount of swept surface area
that the liquid or gas can come into contact with, which results in the least
amount of friction ... so the gas or liquid flows or 'runs' better
(think of pipelines.. when was the last one that you saw which had a square crossection?)
so continuing the theme..
whatever blocks a cylinder...must be also round...
and thus a round valve (in a pipe, on a tap, in an engine port...)
AND...yes there is an AND....you touched on it in your post...
the valve is round because it causes the liquid or gas to run smoother
around it (less in the way of eddies or vortices in the flow...if you want to get technical)
sealing really has NOT got a lot to do with it....you can seal a square valve
(think ships water tight door seals) as well as an engine valve

one other (relatively uncommon) reason for valves being round ....
is that some vehicle manufacturers (especially when unleaded was 1st
introduced) designed engines to rotate the valve..to eliminate hotspots
in the valve..which can lead to 'dieseling' or 'running on'.
you obviously cannot rotate a square valve other than at 90°s each time
whereas a round valve..can creep around at 1° for each movement

me thinks...here endeth the lesson....


cheers

Cheers oh wise Yoda, that's what I was wanting to know

Cheers oh wise Yoda, that's what I was wanting to know

anytime Mick...thats what the forum is for.....
only problem...
is that you will now have to think of sumfing else to ponder about..
on those long rides....

cheers

That's never a problem mate, I've always got something percolating around in there, even if it's just trying to calculate mileage and arrival times in my head...which end up being surprisingly close despite the dodginess of my mental arithmatic

...and Two Wheels looks like their latest edition has a story about the blown VTR..... you could get one into a ZX7R

Shit! now I've gotta go out in this weather. I think it's about to snow!
Thanks, I'll have a squiz. .

...and Two Wheels looks like their latest edition has a story about the blown VTR..... you could get one into a ZX7R

Shit! now I've gotta go out in this weather. I think it's about to snow!
Thanks, I'll have a squiz. .

well
you will live (sometimes) in the coldest place in Vic
EVERYONE knows Ballaarat is always 10° colder than anywhere else..
no wonder its about to snow......what else..sleet? hail?
so yes...
NOW is a good time to go for a ride.....

ballarat is not too bad compared to bendigo.

Yoda

geez Mick....
guess I go back to Mechanics 101....naaah failed that....
but the topic of Induction Theory...I passed....
so here we go...
no... valves do not have to be round .....
but they are round because of what they sit in....
valves sit in a passage (we know them as ports..)
and a port is normally circular 'O' or sometimes like an '0'
and why?

ummmm i agree that there is a possiblity that an oval vavle would work ......same as oval pistons
But (yes there is a but ) i think the main reason would be ease to machine the vavle
machining an oval valve would be a nightmare
isn't that why 4 and 5 valves per cyl came about

..snip...
ummmm i agree that there is a possiblity that an oval vavle would work ......same as oval pistons
But (yes there is a but ) i think the main reason would be ease to machine the vavle
machining an oval valve would be a nightmare
isn't that why 4 and 5 valves per cyl came about

Lucas...
in answer ...no
the problem... the engineers were playing with
concerned... oval shaped PISTONS (one of Mr Hondas pet themes)
especially for racing...with the ol' 2 stroke bikes
(think NSR500 etc)
and yes...the blocks had oval shaped bores (a machinist's nightmare)
but
multivalve engines?
Multivalve engines have been around for yonks....
the 1948(!) XK120 Jaguar had a 4valve per cyl DOHC 6cyl engine....
certainly some of the racing benz's and Ferraris of the early 50's
also had them...
but why?
it comes down to trying to maximise gas flow (inlet or exhaust)
in the internal combustion engine...
it has been well known..that the more air/fuel you can shove in
(think our previous posts on Superchargers/Turbos)
the more power you make..provided you can get the exhaust gases out...
but there is an issue affecting this.
The size of the roof of the combustion chamber in an engine is restricted
why?
because its diameter can't be any bigger than the width of the bore of the cylinder it covers....
(otherwise...you get lots of issues...too many to list here)
and it can't be too far away from the level of the engine block, otherwise the compression ratio will be about 2:1..which is woeful.
so ...
how do we make the holes(the ports) in the roof of the combustion chamber pass as much air/fuel mixture in and as much exhaust gases out, as we can ??
one BIG round valve is tried in a lot of instances...especially with pushrod engines...
but 2 slightly smaller inlet valves open up more of the roof of the combustion chamber then 1 large valve (their total area is more)
and in doing so..
allow more gases in...and more gases out....
and the engine is more effecient and produces more power...
Is more good???
there have been attempts at more valves..for the inlet and the exhaust ports...like 3 a side or even 4 a side
but this causes engineering problems....
how much valve gear can be fitted in to move 8 valves?
Think of the pressure required to start to move them ..off their seats..
how do you fit 4 inlet ports and 4 exhaust ports in a cylinder head and...
still have room to have a sparkplug? (gotta put that somewhere!)
have coooling channels in the head (otherwise you overheat) and
room for the bolts to hold it all down on the block???
so...
the engineers kept playing and found...
4 valve heads (4 valves per cylinder) are good because
you can place the sparkplug where you want for good combustion
you can still bolt the head down and keep it cool and...
4 valves are still efficient...
Yamaha came up with 5 valve heads (2 inlet 3 exhaust ) per cylinder
..a bit more complicated and difficult to design and manufacture
but it does work...
oh
and all these valves are round...coz of the reasons in my previous post!

hth

think that be the end of todays' tute.....

cheers

well
you will live (sometimes) in the coldest place in Vic
EVERYONE knows Ballaarat is always 10° colder than anywhere else..
no wonder its about to snow......what else..sleet? hail?
so yes...
NOW is a good time to go for a ride.....

What else you ask..... well, I'm currently moving all my fresh carbon fibre bits inside in front of the heater coz it won't go off for me
Phark! I'd forgotten how much this shit really stinks, especially inside.

Matt...
CF is MEANT to be cooked in a VENTED oven.....
NOT in front of the heater in ya loungeroom....
shheeeesh

what next????
the gearbox rebuild on the kitchen table....???

hehe

Matt...
CF is MEANT to be cooked in a VENTED oven.....
NOT in front of the heater in ya loungeroom....
shheeeesh

what next????
the gearbox rebuild on the kitchen table....???

hehe

Done that, not a gearbox, but a couple off top ends, and the new undertail. Ah... the joys of vertually living alone.

As for the cf. All depends on the resin used. As long as you use a promoted resin and mix it at 2-3% catalyst, Deracain/vinylester resins don't need an oven. In fact, cooler conditions causes it to take longer to cure which means there's less shrinkage..
People use ovens when they're in a hurry or are after exact flex rates for stuctual stuff like open wheeler tubs and stuff. For exhausts and cosmetics it doesn't matter nearly as much.

Last edited by mattyv74 on Thu Jul 01, 2004 1:39 pm, edited 2 times in total.