Moderator: martauto
Shame i haven't a clue how big a thou' is, metric is the way forward with fine tolerances, mind i'm a mixed up bloke that still likes feet/inches/miles depending whats being measuredTurbo-Brown wrote:Be interested to hear this too actually.
There was that thing in PPC a while back by Dave Vizard which talks about gaining 7bhp for every thou' of squish clearance reduction (I think)
Nothing too fancy/expensive, second hand itemsCan ya get off the shelf forgies for the M30 then, or would you need to spec them yourself?
This is along the lines of what i was thinkingJhonno wrote:better mpg, more tractable engine, maybe 10bhp if mapped to suit
engine will obviously rev up quicker due to lesser rotating mass
yeah this is true-engine will accelerate faster, but how much torque will you lose? I assume lightened pistons would have a similar effect to a lightened flywheel?Jhonno wrote:better mpg, more tractable engine, maybe 10bhp if mapped to suit
engine will obviously rev up quicker due to lesser rotating mass
that is a total misunderstanding.. how much an engines internals and the flywheel weigh has nothing to do with the torque produced. Torque is the force exerted onto the crank from the pistons due to the ignition of the fuel. its a measure of how much force an engine can exert, bhp is how powerful it is ie the rate at which it is able to produce the torque (rpm)320Touring wrote:yeah this is true-engine will accelerate faster, but how much torque will you lose? I assume lightened pistons would have a similar effect to a lightened flywheel?Jhonno wrote:better mpg, more tractable engine, maybe 10bhp if mapped to suit
engine will obviously rev up quicker due to lesser rotating mass
I dont know what you think andy, but i wouldnt want to lose the "ballsout laziness" of the m30
Turbo-Brown wrote:The mass of the rotating components makes no difference to the steady state performance of an engine i.e. up hill.
Imaging we're driving up a perfectly even grade of 1in10 and have been for 5 minutes at 30mph. We won't have to change the throttle opening at all to maintain that speed because we've reached a steady state of load on the engine which is producing enough power to overcome wind resistance and gravity.
Now imagine that we kill the power and coast to a halt (ignoring engine braking) giving rise to a transient condition. The distance we travel without power will be a function of the vehicle mass and the rotating masses and the retarding forces on the vehicle like wind, friction, gravity etc.. If we had a massive flywheel we'd go on for quite some time. With a tiny flywheel, we'd most likely stop in much less time.
Another (more real world) example:
Say we're driving at 30mph on the flat. We'll have say 5% throttle opening to maintain our speed. Now we approach our mythical hill which means to maintain 30mph, we'll need to open the throttle to say 10%. This is where our rotating mass comes into play:
With a light fly etc, we'll need to get on the throttle pretty soon after starting up the hill to avoid losing speed, with a massive heavy fly, we've got a little more time to open the throttle. Once on the hill though, the throttle openings will be exactly the same at 10%.
alex (for I think tat is your name?)Turbo-Brown wrote:The mass of the rotating components makes no difference to the steady state performance of an engine i.e. up hill.
Imaging we're driving up a perfectly even grade of 1in10 and have been for 5 minutes at 30mph. We won't have to change the throttle opening at all to maintain that speed because we've reached a steady state of load on the engine which is producing enough power to overcome wind resistance and gravity.
Now imagine that we kill the power and coast to a halt (ignoring engine braking) giving rise to a transient condition. The distance we travel without power will be a function of the vehicle mass and the rotating masses and the retarding forces on the vehicle like wind, friction, gravity etc.. If we had a massive flywheel we'd go on for quite some time. With a tiny flywheel, we'd most likely stop in much less time.
Another (more real world) example:
Say we're driving at 30mph on the flat. We'll have say 5% throttle opening to maintain our speed. Now we approach our mythical hill which means to maintain 30mph, we'll need to open the throttle to say 10%. This is where our rotating mass comes into play:
With a light fly etc, we'll need to get on the throttle pretty soon after starting up the hill to avoid losing speed, with a massive heavy fly, we've got a little more time to open the throttle. Once on the hill though, the throttle openings will be exactly the same at 10%.
dude, I was the one soundin like a thicko-no offence taken at your post dudeJhonno wrote:no worries dude, thats what tinternet forums are about.. sharing info
didnt mean to sound harsh in my reply if i did, just had my last exam for the yr and was in a rush
Email FTW worth the effort for sure though. Email FTW
Cheers, that make sense.Gunni wrote:a note on ignition advance,
think about it as cylender filling = torque ,
torque = cyl charge temp
cyl charge temp = ignition advance possible before detonation
cylender filling = ignition advance
the more air the less you can advance it, i.e if your at the limit and raise the charge temp(more air or higher compression) you need to back off the ignition advance
if your raising compression I would only back the advance off in the high torque sites, and then move back in after to get optimum advance
your right, when you have a rr or a dyno as I like to call them,Andy335Touring wrote:Cheers, that make sense.Gunni wrote:a note on ignition advance,
think about it as cylender filling = torque ,
torque = cyl charge temp
cyl charge temp = ignition advance possible before detonation
cylender filling = ignition advance
the more air the less you can advance it, i.e if your at the limit and raise the charge temp(more air or higher compression) you need to back off the ignition advance
if your raising compression I would only back the advance off in the high torque sites, and then move back in after to get optimum advance
I think the way they map the ignition if you have acess to a RR is advance the timing until you get max power at the load site your working on, check the fueling as you tweek it and then back it off a tad to give a margin for error for bad fuel ect to stop it pinking.
Shame i've not got a RR to use
Email FTW 
method of CCing is spot on, use the flat surface (clear plastic bit) to prevent meniscus of water. i use sand too to verify on pistons, but you have a nightmare cleaning everything up. i use blue tac as the plastercine stuff. you will def have to check impact on CR and measure CC of all combustion chambers. is it gonna be worth it? how far is the increase in CR going to be mitigated by the increased volume of the C/C? (btw haven't read thread in detail, just last post).Andy335Touring wrote:The engine is supposed to be from a E34 B10, it has the upward pointing oil filter housing which again points to it being from an E34 but it's in no way concluesive.
Well, it wasn't raining when i got home today so i cleaned the block face up and dummy fitted it with an old H/G and a bare scrap e34 head, it doesn't quite get to TDC and locks up
I'm hope fully going to get some pictures of the 'pina head tomorrow to confirm the combustion chamber shape, but it's fairly obvious when you see it in the flesh that it's going to need some shaping. I don't think it will need much taking off at the mo' but i will have to wait and see.
But this brings other problems like measuring what will be the new squish band and taking off the same amount of metal and shape/angle through all six C/Chambers.
So i need to know where to get some suitable putty/plasterseen(sp?) to measure clearances and how much squish clearance should i aim for ?1mm ? 0.75mm ? 0.50mm ?
I also think to do a proper job i will have to measure the CC's of each C/C.
I've read some where that the way to do it is to smear a little grease on the valve seat to help sealing, insert the valves and springs. Cut a square of clear plastic with 4 bolt holes and a small hole to put the water in. Another smear of grease on the cylinder head face and secure it with 4 bolts/nuts and add water with a syringe(sp?) and measure/keep note/grind some more and repeat. Sound's like fun !
So much for getting back on the road by this Sun/Mon
oh yeah, that figures. how much are you talking about increasing the chamber size by? do alpina do the same on their heads? how much clearance are you going to leave between the piston and the chamber on the bits where the piston protrudes?Andy335Touring wrote:I am going to try to copy the 'pina head, although i will be increasing the the head volume slightly the pistons protrude more in to this space so i should still have acheived a C/R of 10.6:1
Blutack seems a little rubbery, if you squeeze or pull it, it want's to pull back to shape a little, not ideal stuff to use i'd have thought ?
