4Y compression ratio increase?

[3vilc]

Hi guys, just wondering if anybody has shaved the head on thier 4Y to increase the compression, and if so by how much and what were the results like?
Theoretically at least, higher compression should result in using less fuel at the expense of some low end torque. So from the specs I imagine a standard 4Y is probably quite low compression ratio which is where it gets its torquey but thirsty nature from.
Any ideas?
Just an idea, 2nd hand parts are impossible to find in New Zealand, and at the moment an engine conversion is not an option, so if there are some easy ways to get a bit more from the old girl they would be worth looking at

[Mud Dog]

Don't think it's a good option ... that motor doesn't like higher compression. Perhaps it's because of there being so little 'meat' between the bores, but the gasket will blow through between .... mostly between no 3 and 4 cylinders (hotter end of the motor). There have been some attempts at fitting turbo's but largely these have been unsuccessful ... boost has to be kept low and ignition timing retarded, otherwise you could blow the motor. Also not sure if the standard con-rods / bearings / crank can handle turbo boost. There was some discussion on it here a long time ago .... do a search ( "4Y turbo" ).

Your best option would be to continue looking out for an EFI setup as previously mentioned.

[Cruza]

Gday

On my 4Y Efi conversion re build, I shaved 10thou of the head & block.
Compression was 200psi per cylinder, with a variation of 3psi.
Standard CR for a 4Y is 8:9:1 mine is very near to 10:1.
This is the safe maximum limit for forced induction engines with <10psi boost.
Out side this it is recommended that low compression forged pistons are used.
I also incorporated multi point water meth injection. The reason being they recommend low compression forged pistons is because of the heat that is created with high compressions & forced induction engines. What the high air temperatures create is a lower density air which leads to pre-ignition or knock. Instead of the air/fuel being ignited in the combustion chamber it is combusted before it gets there, hence the water / meth injection. By doing this it also allows you to substantially retard your ignition timing.

I run a Sprintex S5 150 supercharger @ 10psi boost, standard 4Y has 91hp on paper mine is 190hp. http://brianlawson59.blogspot.com.au/" onclick="window.open(this.href);return false;

As far as your con rods go, they will handle approx 5ton per square inch of pressure, so they are fine. Not to mention I have only ever found 1 company that supplied after market con rods for a 4Y engine, they where in the USA and the price was scary, even for me.

I have just spoken with Mr Phil de Wit CEO of Magnecor Competition Ignition Leads in the UK.
He is sending me a set of KV85 Competition leads to try out, they are 8.5mm diameter with 2.5mm conductor (for free). As in our conversation I discussed the lack of HP ignition parts for 3Y & 4Y engines, so he is generating a set for 4YE engines.

I hope this helps you

http://www.magnecor.co.uk/contact.htm" onclick="window.open(this.href);return false;

http://www.magnecor.co.uk/gallery.asp?I ... =DOWNLOADS" onclick="window.open(this.href);return false;

[Cruza]

A point, when re-building a 3Y or 4Y engine the head bolts need to be thrown away and new ones purchased.
Initially torque then down to the required specifications, then undo then and re torque them down. This will stop any gasket bow outs, I might mention here that I used an ACL Mono Torque head gasket, so as to avoid any issues.