compression question

[absolut250]

Hi,
i need to know the standard compression of sgti, standard gsr and how much lower will the compression with say 1.8mm gasket on the gti block.

 

[alvin24]

WAH! 1.8mm on a GTi block... surely not drivable man!! U know stock gasket how much only ar? Its about 0.8mm paper gasket, so when screw on the head that time, the gasket gets slightly compressed to around 0.6 or 0.7mm... u put 1.8mm gasket surely low end can't drive for nuts... engine response will be super-bad!

You trying to shove in turbo kit is it?

Advice for you... leave the gasket alone, drive with 0.4bar.. or 0.5bar if u're really daring. Its really much much more drivable...

1.8mm is too thick man... even for a GSR. I think GSRs that up boost also go up to 1.2mm metal gasket only.

IF you were to really wanna go for lower compression also, i suggest just put in 1.0mm metal gasket... should be more than enuff... that will already kill the drivability at low revs (ie: city driving)... but will probably allow u to boost up to 0.7 bar or so.

Just my 2cents...

 

[saru-kun]

4G93P DOHC cr is 10.5:1
4G93T DOHC cr is 8.5:1 if i'm not mistaken
cheers

 

[beeboy]

so if a set of 9:1 compression ratio forge piston plus a 1.8mm gasket = how much compression?

 

[carcraze]

Guy (sifus),
I'm a bit blur on this compression thingy. I drive a VR4 and to up the bar, I need to thicken my gaskets? And what is;
4G93P DOHC cr is 10.5:1
4G93T DOHC cr is 8.5:1 if i'm not mistaken
Very blur on this topic. Need enlightenment. If I change adjustable pulleys, does it effect anything?

 

[saru-kun]

compression ratio ah...err, how do i go about this...ok..
its; the volume of the combustion chamber when the piston is at BDC (bottom dead centre) to the volume of the combustion chamber when the piston is at TDC; in other words...how much the fuel/air mixture is compressed before the spark plug fires....
damn..i'm no good with words...someone please help correct my sentence construction...
cheers

 

[carcraze]

So what does those ratios mean?

 

[desmond23]

can anyone tell me what is gasket? what is its function? why need to change gasket one?

 

[sycay]

in my stock putra, i hav just replaced my head gasket to the size of 1.5mm metal gasket. this was recommended by the sparepart seller commented it is better and more powerful. in my opinion i didnt think so.

since now, i didnt feel much different in the form of less power of more power, but i did feel that engine runs smooth than b4. The modification i hav done b4 were the additional of fuel regulator, hks air filter element, and adjustable cam pully. after the replacement of the metal gasket, the foremen adjusted the fuel regulator to the maximum point, retuned the cam pully as well. anyway eventually i feel the performance worked well than b4 although the compression ratio should be logically reduced as the 1.5mm metal gasket was inserted.

what happened indeed? one thing was the fuel consumption was obviously increased.

actually, anyone can make some comments here?

 

[delphinium]

i think your fuel consumption increased due to the FPR being set to the fullest. DOnt really know the effect of changing to a thicker gasket. anyone share please?

 

[alvin24]

Originally posted by sycay@Jan 21 2005, 02:33
in my stock putra, i hav just replaced my head gasket to the size of 1.5mm metal gasket. this was recommended by the sparepart seller commented it is better and more powerful. in my opinion i didnt think so.

since now, i didnt feel much different in the form of less power of more power, but i did feel that engine runs smooth than b4. The modification i hav done b4 were the additional of fuel regulator, hks air filter element, and adjustable cam pully. after the replacement of the metal gasket, the foremen adjusted the fuel regulator to the maximum point, retuned the cam pully as well. anyway eventually i feel the performance worked well than b4 although the compression ratio should be logically reduced as the 1.5mm metal gasket was inserted.

what happened indeed? one thing was the fuel consumption was obviously increased.

actually, anyone can make some comments here?

if u dyno... i can almost confirm with u ur hp drops... from 0.8 paper gasket, u insert 1.5 metal gasket... u have any idea how much compression is lost ar? Since u mentioned 'stock putra'... i'm assuming its n/a... everyone goes for higher compression by either skimming the head or changing to thinner metal gaskets.... which fool suggested to you to change 1.5mm gasket lar?!?! (you sure it isn't 0.5mm instead ar?)

Turbo cars lower their compression in order to be able to boost higher... else there will be detonation. By doing so... their low end will be sacrificed for the sake of boosting higher at the high end.

Its going to be costly for u to change back to normal gasket to get back ur normal compression... think the workmanship charges to open up the head itself will be around 450 bucks plus minus... not to mention the purchasing of gaskets again.

I think now 4G91 also can tapau u ler... no need to even compare to other 4G93s.

 

[chanl55]

Bro,

Only 1.5mms available in the market ler, at least in Penang. can't find anyone that sells 1.2 or 1.1s. I was considering the 1.5mm as well...no other choice dude..can't get them to order from KL as well as they said they did a search high and low as well...1.1 or 1.2s not available

 

[tajulsans]

Originally posted by desmond23@Dec 20 2004, 19:01
can anyone tell me what is gasket? what is its function? why need to change gasket one?

gasket is a thin layer of material (metal, paper or combination) placed in between joined area of two parts assembled, that contain fluid either gas or liquid.. function is to fully seal the join to avoid leakage lo.. metal surface might be havin some uneven surface.. ussualy not required to change until it is leaking or the parts is desmentled

 

[alvin24]

Originally posted by chanl55@Jan 22 2005, 16:29
Bro,

Only 1.5mms available in the market ler, at least in Penang. can't find anyone that sells 1.2 or 1.1s. I was considering the 1.5mm as well...no other choice dude..can't get them to order from KL as well as they said they did a search high and low as well...1.1 or 1.2s not available

HAhaha... sure boh? But i still think its dumb to lower the compression of an n/a car... as i said, confirm a 4G91 can tapau a 4G93n/a with 1.5mm gasket man. Its like eating more when u're going on a diet... u'll get the direct opposite effect.

I'm currently using 0.5mm metal gasket... don't see why its difficult to source. I've also tried driving a car that had its compression lowered (but not as badly lowered as changing to 1.5mm gasket)... really really super sluggish. ITs kinda like driving a car with half its displacement!