Boosted 172 help

[Radugns]

Hello,
I'm building and engine for my 172 Clio. I will want to run at around 280-300hp to keep stock gearbox/driveshafts. The setup will be:

172 engine block, bored to 83mm pistons
PEC/Wossner combo 9:1 CR for megane
Helix clutch
197 head
g28r turbo
172 cams
197 solenoid with 172 dephaser

Head gasket? Here is my problem. The CR of 9:1 is for using it with megane 225 cylinder head and not 197 head. From pictures, the combustion chamber on the 197 head seems to be bigger than 225 head. In theory, if I will use it with Megane head gasket, the CR will drop by about 0.6:1. Should I go for Clio (thinner, 0.65mm) head gasket and keep the 197 head?

I want to use the 197 head because it has been skimmed, new guides, stem seals and supertech valves.

Thanks a lot
Radu

 

[bloke]

Stock gasket will be fine. I'd still be inclined to run a phase 2 head though.

 

[Radugns]

Stock gasket will be fine. I'd still be inclined to run a phase 2 head though.

So for using the 197 head a stock 0.65mm will result a CR at around low 9:1?
For using the ph2 head I need to run thicker gasket, right? As combustion chamber looks similar. Is there a good reason for running a ph2 one?
Thanks a lot

 

[bloke]

unless you are chasing silly power the standard head is more than good enough. seen a couple of head conversions and they've not tensioned up properly, not saying this is always the case though.

personally for the power you want i'd go with stock head and gasket, deck the block and go for 10:1 cr. will give you something nice and responsive. without checking chamber volume and running it through a cr calculator i'd say with a 197 head and stock gasket you'd probably be a lot closer to 8:1. stock cams, r****d the inlet and advance the exhaust a bit to reduce overlap as well could see you with a nice set up.

will ask my lad to measure chamber volume on a 197 tomorrow, we've got one to do next month low boost on stock internals.

 

[Radugns]

I understand now. If this will be the case I will just use the stock head. The CR will drop with around 1.2:1 compared to stock ph2. The problem is the difference between 225 head and 197. I will wait for the answer. Thank you!

 

[JamesBryan]

Anyone ever done a high comp boosted setup?

Guessing you'd need good/race fuel for it to work reliably.

 

[bloke]

my lads twiglet was high ish comp and we're doing a 197 on stock internals next month, probably run a 14t on it.

 

[Radugns]

The 172 combustion chamber is almost like 225. And the 197 drops the CR with about 0.7:1 (almost like a thicker head gasket (Megane one) compared to thinner head gasket (Clio 172 one) ). So with the amount of skimming I should be able to be very close to 9:1 with thinner head gasket, 197 head and wossner megane pistons.

 

[incy-spider]

This may help you, a little chart from when I was working out comp ratios in my 182 using MEG 3 RS 265 pistons and rods, ended up using the stock gasket and it’s lovely! 9:1

I went from a low boost setup with stock internals using the ED kit to then the Megane internals and maxed out the setup at 282bhp and didn’t notice much response differences, maybe a tad laggy but this is being dealt with by my new turbo [emoji106][emoji106]


Sent from my iPhone using Tapatalk

 

[Radugns]

View attachment 1440783

This may help you, a little chart from when I was working out comp ratios in my 182 using MEG 3 RS 265 pistons and rods, ended up using the stock gasket and it’s lovely! 9:1

I went from a low boost setup with stock internals using the ED kit to then the Megane internals and maxed out the setup at 282bhp and didn’t notice much response differences, maybe a tad laggy but this is being dealt with by my new turbo [emoji106][emoji106]


Sent from my iPhone using Tapatalk

When you have time please upload a better pic. Thanks a lot! This will help me!