Hi

A while a go Lorc asked if anyone new how close the valves get to each other. Also I had valve to piston contact when racing. So to check it out I looked into a 3D program.

It's taken me a while but I have manage to sort a 3D program to change the valve timing and valve sizes to check how close they are to the piston and each other. You have to draw a model the same as the turbo engine then import it into the other program.

Check these screen shots out. I have focused on the program first, Then I can sort the finer sizes out. They are not too far from being right but when we have such small clearances to deal with they better be spot on.














I tried to get a vid of it but failed.

Tack1000

Wouldn't valve to piston contact be from valve float at high rpms?

Neat! I checked my valve to piston clearance with plasticene, but you can't do valve-to-valve that way.

Hi

Ok, checked all the dims and some were wrong, as I just put the parts where I could for now, as I said more to learn the program than get the numbers.

But now I have redrawn the lot in the right position.

This is what came out with the cams timed at 105 110 lobe center







You can see ,
the valve to valve is 3.72mm,
the inlet to piston touches a lot, but the program (or I can work out how) stops at zero instead of a minus number.
the exhaust to piston is 0.618mm.
Although the piston would have a cut out for the valves it does not show it here. I could redraw the piston with the cut outs in to give the true gap.

Tack1000

I gather you're a mechanical engineer, there is a lot of criteria to gather to get a true scope on all of this-valve angle,valve length,cam center,crank center, rod length, piston height,deck height,etc.how did you get all these specs.? then incorporate cam angle and lift ,it looks simple in the pics.but I know it's not.very cool

Hi

I have seen somewhere the stroke is not 54mm but some odd number like 54.34mm.
Can anyone confirm this?

KM542, All the data is to hand, you just draw all the parts needed. Some things you can take as read, like the piston is set to only move up and down, the crank only moves in a rotary motion, the valves only move in a direction preset by me (IE 30 degs from 0). The head scratched is working out how the program writers have decided to make their program interact with you.

They don't always live in the real world, well not the world you and I would call real anyway.

Anyway thanks, just trying to spread the word. Normally I don't have the time when I get home cose I am so knackered, The wife still has to work over the Christmas break so that gives me some own time as the Kids are 17 and 18 they have there own lives and language come to that.

Lorc, made a remark about more power to come, I think he is right. So the plan is to do some fairly heavy ground work now so I can be ready for the New Year. My guess is I wont be able to put in so much time actual racing due to the cost and current climate. So when I do I hope this will help, and give me some more GG's

Tack1000

Hi Lorc

What was the gap you got with the plasticene, it would be good to cross-check my results.

I was thinking about cutting #4 barrel in half so I could see and measure the valves and piston. Just not got round to it.

Jeff

I can't remember, it was less than 1mm. I'll check with Mick (Hand) cos I remember checking with him that the amount was ok. Does the program factor in anything for the rod stretching, skimmed barrels etc?

I had to add valve pockets on my 760cc motor cos the pistons were out of a 4 valve CBX engine. If you are short on clearance you can always deepen the pockets, it's not a big issue. You should remove all the sharp edges from the pockets too, helps prevent detonation.

Hi Lorc

At the mo its as drawn, I think it can have a formula that facture stretch in but as I am only just starting with the program that is a little way yet. Does not stop you from adding or removing an amount.

The pistons I use have the pockets it's just the drawing that does not. What i would like to work out is are the pocket in the right place or could they be moved to give a better safety margin.

Jeff

Tack1000:

What software is that that you are simulating this on????

Just remember it is the exshaut valve that is most critical (valve to piston clearance)
why
because the piston is chasing the exshaut valve in the final stroke!