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Discussion Starter · #1 ·
I am in the process of finishing up a turbo mkv R32 build (HPA 7670 with a custom front mount intercooler). During this whole process, lowering the compression ratio is necessary while adding any type of boost to the motor to run the car safely and there is some misinformation I am trying to sort through regarding head spacers/ spacer gaskets for my build. So, HPA sent me a 5mm head spacer (the spacer is 5mm, not including the thickness of 2 head gaskets required to seal the head with the spacer. Each gasket's compressed thickness is supposedly .065") and this is supposed to lower the compression to 7:1, which I suspected was way too low for my power goal of being 400-500 awhp. Fred at united motorsport confirmed this being too low as well, and said the timing would be whacky while trying to tune this thing, and not to install it. Any ways, I found a company called SPA that sells a 3.65mm spacer head gasket thats supposed to lower the compression to 8.5:1. Here's the kicker: MK4 and Mk5 R32's have different compression ratio's, mk4's being 11.25:1 and mk5's being 10.85:1. So SPA, or any of these companies selling head spacers or spacer gaskets do not list the specified compression reduction for mk4 and mk5 models. Does anybody know the calculations to figuring these compression ratio's out specifically? And what is the difference between mk4 and mk5 r32's difference in CR (pistons possibly?). The biggest issue Im having is if SPA advertised their 3.65mm headgasket for an mk4 engine (11.25:1CR) bringing it down to 8.5:1, this means me using that gasket on my 10.85:1 CR mk5 engine is resulting in an even lower CR than 8.5:1, and Im not sure if I want it that low. Any knowledge on this subject is appreciated!
 

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Mk5 Golf R32 , black 3 door 2006
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As I am sure you know, to do the calculation you need the head chamber volume, the piston crown volume ( -ve or +ve ) , crown distance to deck height at tdc , Bore and stroke , gasket thickness and diameter .In my experience , quoted head chamber volume and actual measured volume can be significantly different . Others on here may well have done this upgrade and have the data at their fingertips, Lucifer I guess for one . Mind you, if you have the head off , and have a burette , and a depth gauge , you can measure all you need. If not , as you say, you need the data .
 

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Discussion Starter · #3 ·
As I am sure you know, to do the calculation you need the head chamber volume, the piston crown volume ( -ve or +ve ) , crown distance to deck height at tdc , Bore and stroke , gasket thickness and diameter .In my experience , quoted head chamber volume and actual measured volume can be significantly different . Others on here may well have done this upgrade and have the data at their fingertips, Lucifer I guess for one . Mind you, if you have the head off , and have a burette , and a depth gauge , you can measure all you need. If not , as you say, you need the data .
Yes, I do understand what youre saying, but I was looking for a calculation that gives me a good idea of what I have, for example; If a 3.65mm head gasket gives you 8.5:1 on an original 11.25:1 engine than a 3.65mm gasket will give you 8.1:1 on an engine that was originally 10.8:1..... Which I believe is what I got after screwing around last night. It may be wrong, but ideally like you said, I was hoping someone who has the data at their fingertips would comment and tell me lol. I believe this data should be somewhere for when an R32 owner wants to add some sort of FI to their car and wants to get an accurate idea of which spacer, or head gasket is going to give them for a CR. In fact this helps the tuner out as well, and can save an owner time and money by not having to swap a too large of headspacer out for a smaller one to accommodate the tuner (true story, a guy dm'd me telling me how the shop couldnt get the guys car to run correctly because HPA sent him a 7:1 headspacer and they ended up having to install a smaller one). Thank you for the input anway.
 
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