F7R turbo, what compression ratio do I need?

Spoke to the engineers today who are doing my engine and I chatted to them about getting my pistons skimmed 1.9mm to lower the compression for the turbo.

They said it doesn't work like that because there are too many variables inside an engine which contribute to the compression i.e. headgasket thickness and head depth etc..., what they did ask for is a compression ratio I would like the engine to be and they'll work out from there how much the pistons need to be skimmed.

So what compression ratio everyone else running in their F7 turbo's, what works best and what differences are there?

Cheers :agree:

8:5:1 for low boost up to 1.5 bar
8:0:1 for running over 1.5 bar and cazy boost:smokin:

Sounds like they take it too serious for this particular build.

1.9mm out of the dish will give a bit more than 9:1, low enough for plenty of boost!

I skimmend mine flat top to keep the crown as thick as possible.
Only after i had my engine back together 'steer from the rear' came with 320bhp on skimmed pistons the same as you want. (On 95octane he was reaching te knock limit)

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Originally Posted by turbo ted

8:5:1 for low boost up to 1.5 bar
8:0:1 for running over 1.5 bar and cazy boost:smokin:

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Whats the max bhp for both of these?

If I went for 8:5:1 and wanted more it means engines out again, so is 8:0:1 safer to start with? I'm looking for 250bhp max at the moment.

There no simple answer as to which cr to run for how much hp.

250 can probably even be done on stock cr. 9:1 is low enough for 300 anyway so will do 250 all day.

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Originally Posted by Tutuur

Sounds like they take it too serious for this particular build.

1.9mm out of the dish will give a bit more than 9:1, low enough for plenty of boost!

I skimmend mine flat top to keep the crown as thick as possible.
Only after i had my engine back together 'steer from the rear' came with 320bhp on skimmed pistons the same as you want. (On 95octane he was reaching te knock limit)

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Really serious :), the engine is also getting fully rebuilt and race balanced, and a slight bit off the flywheel. The engineer said the key to a good reliable engine is having it balanced throughout and said that can give you up to 20bhp alone on some engines, plus with it balanced you get more out of every other mod you do from there on i.e. cams, map, turbo etc...

He's been building engines for 50 years :eek:

He is completely right but the question is can you justify the cost?

If you're going to take it that serious get a set of forged rods+pistons and it'll be 500+bhp capable.

My build was just a low budget but reliable turbo build with the goal of 320bhp or so.

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Originally Posted by Tutuur

He is completely right but the question is can you justify the cost?

If you're going to take it that serious get a set of forged rods+pistons and it'll be 500+bhp capable.

My build was just a low budget but reliable turbo build with the goal of 320bhp or so.

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I thought about going forged but I can't afford it within my timescale, the balancing is only costing £150 so it's not to bad, and i've got 2 months to pay for all my engine getting done (half paid already)

Still need a turbo, downpipe, exhaust, ECU, wiring, intercooler and big brakes all within 6 months. My 19 is pretty much ready to have the engine put in. F7p has been removed, subframe has been off and cleaned/painted and the engine bay is gleaming. Well ahead of schedule :agree:

I have alot of stuff you're looking for but can't let them go atm...

Are you going standalone or renix with chip?

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Originally Posted by Tutuur

I have alot of stuff you're looking for but can't let them go atm...

Are you going standalone or renix with chip?

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What have you got?

Going standalone adaptronic ECU.

Downpipe, pistons, turbocharger, injectors (but you need high impedance for Adaptronic)
Have a chipped renix ecu atm for 10psi and aprox 250bhp but need ot to drive the car till i have standalone

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Originally Posted by Tutuur

Downpipe, pistons, turbocharger, injectors (but you need high impedance for Adaptronic)
Have a chipped renix ecu atm for 10psi and aprox 250bhp but need ot to drive the car till i have standalone

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Is this all in your 9 turbo? Sounds like a bit of a beast. I have a ph2 9 turbo in my collection :agree:

Yes mate, it goes well :)

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Originally Posted by Tutuur

Yes mate, it goes well :)

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Wolf in sheeps clothing ;)

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Originally Posted by Tutuur

Downpipe, pistons, turbocharger, injectors (but you need high impedance for Adaptronic)
Have a chipped renix ecu atm for 10psi and aprox 250bhp but need ot to drive the car till i have standalone

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No, Adaptronic works with any injectors, low or high :)