Jump to content

Welcome to the brand new 205GTIDrivers.com website! We hope you'll enjoy it! Read the full notice here.

  • Welcome to 205GTIDrivers.com!

    Hello dear visitor! Feel free to browse but we invite you to register completely free of charge in order to enjoy the full functionality of the website.

B1ack_Mi16

[project] Project 205 Xu13j4

Recommended Posts

B1ack_Mi16

What dynamic compression should one aim for by the way?

Share this post


Link to post
Share on other sites
B1ack_Mi16
Posted (edited)

Using this calculator (http://blackartdynamics.com/Compression/EngineCompression.php) it seem to give 11.61:1 static and 8.92:1 dynamic using 0.1mm lift CAM durations and 106 centreline on the intake and 108 on the exhaust, 0.8mm gasket.

11.38:1 and 8.75:1 with 1.0mm gasket...

Edited by B1ack_Mi16

Share this post


Link to post
Share on other sites
petert

Sweet, I'd go with the 1.0mm gasket, unless you can improve the valve-piston clearances otherwise.

Share this post


Link to post
Share on other sites
welshpug

thats not right either, nsfw!!

Share this post


Link to post
Share on other sites
petert

Whoops.

Share this post


Link to post
Share on other sites
B1ack_Mi16

So I started measuring some valve-lift this evening. 

 

Just a simplified calculation this far, as I believe the additional valve clearance when the piston moves 1mm down the bore, will be more than 1mm, due to the valve sitting at an angle. But that I'll have to think more about later as the brain is saying stop now :)

 

This is what I found, only did the exhaust cam, and measured it the wrong way but numbers should be valid as long as the cam is symmetric.

 

pOtGuOm.jpg

 

Identified the peak angle of the cam and then measured the valve lift in steps relative to that.

Seem like the clearance for the exhaust valve is at it's worst at 9 degrees ATDC, but still in reality more than 2.5mm clearance for the exhaust.

 

R1wxoep.png?1

  • Thanks 1

Share this post


Link to post
Share on other sites
petert

Good work, use the sine rule to work out difference in 1mm

Share this post


Link to post
Share on other sites
B1ack_Mi16

Yes should be quite straight forward, what angles do inlets and exhausts sit at respectively? (I could of course measure it but maybe it is common knowledge :))

Share this post


Link to post
Share on other sites
SRDT

It should be 49,5° (49°30') for both.

Share this post


Link to post
Share on other sites
petert

I make it 64º inlet and 66º exhaust.

Share this post


Link to post
Share on other sites
SRDT

My bad, it's 49.5° between inlet and exhaust.

Share this post


Link to post
Share on other sites
B1ack_Mi16

Ok, from vertical line I measured like 27 deg for the inlet and 22.5 deg for the exhaust. That match 49.5 deg between the valves at least.

 

Compared to Peters values it converts to 63 deg for inlet and 67.5 deg for exhaust so pretty close.

Share this post


Link to post
Share on other sites
SRDT

Looking at some FIA homologation form we have the XU10J4 specs: 25.5° between intake valve and vertical and 24° for exhaust. Bdw 49.5° between valves is just like the 205 turbo 16.

Share this post


Link to post
Share on other sites
B1ack_Mi16

Ok, well I think my numbers were quite correct, but I suppose XU9J4 should be the same as XU10J4 anyway,

 

Only bad news regarding the inlet valve clearance. With 1mm gasket and 106 deg timing.. about 0.75mm clearance valve to piston. 
About 1mm clearance with 108 deg timing.

xqsKFYI.png

Share this post


Link to post
Share on other sites
petert
Posted (edited)

You really to be at 1.5mm  minimum on the inlet. Thus you need to mill the piston regardless. Did you allow for valve lash in your calculations? Nice graph!

 

 

edit: I guess you must have, if you did it as per the pic, with the head upside down, assembled.

Edited by petert

Share this post


Link to post
Share on other sites
B1ack_Mi16

I simply just left the valve clearances as they were, but I corrected all the lift values by the difference between specced max lift and measured maximum valve lift, this might possibly be a little bit wrong especially for low lifts maybe?

 

I need to re-measure the inlet clearance I think, I really don't like the idea of fiddling with the pistons at all. Maybe I shall slap some low lift T16 camshafts in it just to be sure it doesn't hit -_-

Share this post


Link to post
Share on other sites
petert

Don't be shy, just find someone with a fly cutter. You only need to cut 1mm from the inlets. Make a jig yourself and it won't cost you much. Set up time is where the money goes. The finished engine will be so much better.

 

In regards to the valve lash, you only need to worry about that if dropping a valve onto a piston, as I do. As yours is all assembled, the lash has been taken up as normal.

Share this post


Link to post
Share on other sites
B1ack_Mi16

Really can't be arsed dismantling the bottom end. Maybe I just need to stay with the old 1.3mm gasket after all and put it back as it was. 
I don't have time for more troubles :) The main goal is to get it not to leak oil anyway.

Share this post


Link to post
Share on other sites
B1ack_Mi16

So.. lots of work later.. 

 

Well, I did go at it with a rotary burr... not something one would do normally, but I though I'd try it.

Pistons might get weak around the first ring land after the change, but that would have happened with proper machining anyway so worst case the pistons are going bust... but that I'll not know before giving it some revs.

 

Cyl 1 in progress 

VfOfQAD.jpg

 

Cyl 1 & 4 done.

 

XEEfJCW.jpg

 

Cyl 2 & 3 in progress

 

1E0n5tF.jpg

 

After this modification the clearance at TDC is in the range 6.3mm +- 0.1mm.

 

Now I need to measure up the new valve pocket volumes.

And I'll probably ask for a 0.9mm head gasket if that is a possibility from the manufacturer.

 

Edited by B1ack_Mi16

Share this post


Link to post
Share on other sites
B1ack_Mi16

Also picked up the valve spring shims today.

2mm thick so at least the inlet valve springs are now installed height 37mm, I think the exhausts might end up at 38mm if I remember correctly, but that will probably be sufficient as it worked as a charm as it was before without any shims too.

 

AgkPiVQ.jpg

 

 

Share this post


Link to post
Share on other sites
B1ack_Mi16

Also I have re-measured everything regarding piston pocket volumes this evening.

Piston is also protruding the deck by 0.05mm so adding all these factors together give a final compression ratio of 11.5:1 with a 1mm thick headgasket.

 

That is fairly perfect I think.

 

Updated valve to piston clearance chart shows now just below 2mm clearance as minimum for the inlets when set at 106 degrees.

 

Q06q03h.jpg

Share this post


Link to post
Share on other sites
B1ack_Mi16

Dismantling the head a bit more, all valves out now. Seem like there are some a bit too deep scratches from the dowels just in the area of headgasket sealing so guess I have to have it surfaced too before it can go back on. :(

 

uWyUl0h.jpg

 

VpwlqKt.jpg

 

ME8P96x.jpg

Share this post


Link to post
Share on other sites
petert

Great work. I wouldn't stress over the scratches. Just smear some 1211 over the area and bolt it down.

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×