Bore area x stroke x number of cylinders
Bore area = Bore x Bore x pi / 4
is this correct?
All you ever wanted to know but were afraid to ask
There's nothing that shouts "Poor Workmanship" more than wrinkles in the Gaffer tape.....
this is making my head hurt 
so....
1 - this would increase cyclinder "capacity" in the full sense of the word not nec the tradition bore x stroke ratio
2 - this would reduce compression ratio
3 - this would mean that the engine runs leaner? - ie more volume but same fuelling..
4 - this may improve power if mapped for it (back to afr thread info)
5 - the compression ration may reduce the power of the explosion and therefore reduce power.
have i got it wrong?
its been a long week
so....
1 - this would increase cyclinder "capacity" in the full sense of the word not nec the tradition bore x stroke ratio
2 - this would reduce compression ratio
3 - this would mean that the engine runs leaner? - ie more volume but same fuelling..
4 - this may improve power if mapped for it (back to afr thread info)
5 - the compression ration may reduce the power of the explosion and therefore reduce power.
have i got it wrong?
its been a long week
1 - I believe so. But this is only from my understanding that seems obvious to me :?
2 - yes
3 - No, same mixture would enter the engine, just a bit more room to fill under boost. There would be a little more 'leftover' burn't gasses, but I think it would be negligable.
4 - I assume there is an optimum. Or I expect the stroke would be made smaller to start with, or all boosted engines would come with big ass stopper head gaskets.
5 - off boost yes, this is a draw back of low compression.
I am not saying that a bigger gasket is better! Just that it appears standard practice to fit a slightly thicker one when the boost is turned up, or when the head has been skimmed. I was advised ot fit one myself. So there must be something in it?
I am quite new to this, and only a diy'er, so if I have it wrong please please please correct me :lol:
2 - yes
3 - No, same mixture would enter the engine, just a bit more room to fill under boost. There would be a little more 'leftover' burn't gasses, but I think it would be negligable.
4 - I assume there is an optimum. Or I expect the stroke would be made smaller to start with, or all boosted engines would come with big ass stopper head gaskets.
5 - off boost yes, this is a draw back of low compression.
I am not saying that a bigger gasket is better! Just that it appears standard practice to fit a slightly thicker one when the boost is turned up, or when the head has been skimmed. I was advised ot fit one myself. So there must be something in it?
I am quite new to this, and only a diy'er, so if I have it wrong please please please correct me :lol:
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'89 ST185 GT4
ONLY 370bhp & 405ft/lb @ fly
12.7s 1/4 @ 109mph in the wet
R.I.P.
These gaskets are a sticking plaster approach to lowering compression, so that you can run higher boost.
They work to a degree but theres a lot in the combustion chamber design thats been developed to reduce the detonation window, by sticking a bigger gap between piston crown and squish bands you can actually increase the chance of detonation.
The cylinder volume is marginally, very marginally, increased, David Vizard's How to build Horse Power vol1 has a section that explains things better than I ever will, but effectively you will have more charge in your cylinders which gives a little more power.
Off boost response may suffer a little, but the lower compression will mean that you can regain a little by advancing the ignition.
They work to a degree but theres a lot in the combustion chamber design thats been developed to reduce the detonation window, by sticking a bigger gap between piston crown and squish bands you can actually increase the chance of detonation.
The cylinder volume is marginally, very marginally, increased, David Vizard's How to build Horse Power vol1 has a section that explains things better than I ever will, but effectively you will have more charge in your cylinders which gives a little more power.
Off boost response may suffer a little, but the lower compression will mean that you can regain a little by advancing the ignition.
This is actually what they are designed for, the deck of my block has been skimmed so that the pistons are now actually proud of the deck (this was done as part of the proceedure to 'square the block' so that each surface is flat and at 90/180 degrees to each other) , consiquently a thicker gasket needs to be used to stop the piston crowns being work hardened on the squish bands. When the head is done we'll be calculating the clearance adding rod stretch and specifying a multilayer gasket from Cometic.TonyB_GT4 wrote:I am not saying that a bigger gasket is better! Just that it appears standard practice to fit a slightly thicker one when the boost is turned up, or when the head has been skimmed. I was advised ot fit one myself. So there must be something in it?