Cr = 11.5:1

[driversdomainuk 8]

Hi

 

As my bottom end is well on its way to being fully rebuilt and whilst the engine is in bits I have decided to increase the CR to 11.5:1 whilst the head is off, in preparation for my 288 degree Catcam (saves time and money you see )

 

I know it is not ideal increasing the CR before fitting the cam. However, to compensate I am going to retard the timing slightly until it goes in.

 

I would like to know, Are there any other precautions I should focus on to ensure I dont bugger the engine in this interim time...? what about fuel..? will the engine feel/run much differently..?

 

thanks

[Dazza 4]

Ok is this a single cam ? 1.9 gti ?

How are you intending to R/C ,,,skimming the head or forged piston's ?

Before you fit a 288 cat cam is there a greater valve lift with these and have you inquired as to tollerences form TDC and valve head ? ideally you want to make sure there's 1-1.5 mm clearance imo as to build in a safe margin of BANG clatter at higher rev's ..

Dazza

Edited October 26, 2006 by Dazza

[driversdomainuk 8]

"Ok is this a single cam ? 1.9 gti ?"

 

 

Hi

 

Yes it is the genuine and original 1.9 205 GTI engine - the way things should be, if its an 8v its still a "205 GTI" in my book not saying the 16v is bad, I just like to know I running the engine the original car was designed to use and became great with.

 

enough of my bollox! I digress

 

I am getting the full kit with the cam including the pulley and retainers/springs so I would imagine this will sort any problems out....However, it is the time in between I will need to be careful about!

 

In reply to your question - I am having the head skimmed to increase CR

 

cheers

Edited October 27, 2006 by driversdomainuk

[Dazza 4]

My advice would be ,speak to your supplier and check the tollerences requires at TDC to Valve head on both Exhaust and Inlets , Check the origional head depth (Haynes manual) or supplier will know this in mm , then you can do some calcs to atchieve your C/R and Tollerences .At some point there is a max you can achieve as there must remain a tollerence and then if your going mad there will be Pocketting the piston's issue's but you can loose C/R s by doing this if your not careful .

Interesting stuff but you do need to raise the C/R to maximise your gain's the cam alone isnt enough .

If your getting to 11.5 or even 12's thats seriously in the ball park !!!!!!!!!! but volitile !!!!!!!!!....

All the best Dazza

[petert 587]

My advice would be ,speak to your supplier and check the tollerences requires at TDC to Valve head on both Exhaust and Inlets , Check the origional head depth (Haynes manual) or supplier will know this in mm , then you can do some calcs to atchieve your C/R and Tollerences .At some point there is a max you can achieve as there must remain a tollerence and then if your going mad there will be Pocketting the piston's issue's but you can loose C/R s by doing this if your not careful .

 

What for? It's an 8V. The valves will never hit the piston unless the belt breaks. Getting the CR in the 11 to 11.5 range will be excellent. I set 11.5 as the max. limit for std. pistons however. I hope you've got a mappable ECU, otherwise you'll have problems with too much advance down low.

[Dazza 4]

Pete forgive me ,i was just up when i wrote my post and got side tracked with my Mi16 advice given to me from my engineer ......iam sure youll forgive me .....

Thanks guy's dazza

[petert 587]

Hmmm... that's strange. There was a response from Puma here not so long ago...........

[cybernck 402 1 Cars]

yes, but it was removed due to complaints from users.