wardy18 33 1 Cars Posted October 10, 2007 Hi all As everyone is bein so helpful i thought i come to you for more answers, followin on from the Head Gasket Topic, i would like to know how to go about increasing the CR on the 8v 1900?! My engine is currently in bits gettin ready for next years hillclimbs and so what better chance to sort everthing out, it will be running 45 DCOE's and Mild Rally Catcam, the pistons are either 83mm or 83.5 mm (the engine was rebuilt before i acquired so need to check what was fitted), i will get the spec on the cam later as i know the valve lift has something to do with working out the CR you can achieve But how do i measure the head to know how much to take off and what CR should i go for and how do i work it all out?! hoep you can help, tahnx in advance Simon Share this post Link to post Share on other sites
DamirGTI 345 Posted October 10, 2007 (edited) Hi ! Me thinks that fitting different (flat top) pistons is better solution for raising CR than go for a heavy head skim (in the end if you don't like the end result of that modification you can always remove them and fit back the standard pistons ..) You can expect gain of around 11.1 (or as high as 12.3 ..) CR when using 1.6 pistons (they have just slightly dished area ..) in 1.9 engine , but the most easier way is to find set of 1.9 DFZ pistons , they are exactly the same size and crown shape as the ones inside 1.6 engines , but the easier bit is that you don't need to replace conrods as they are the same length as the ones on 1.9 D6B dished pistons .... if you chose 1.6 pistons you will need to press out 1.6 conrods and press in 1.9 conrods which is a bit hard job and one of the pistons can be damaged during this pressing out pressing in - it's much easier to find good set of 1.9 DFZ pistons and you just need to clean them , fit new piston rings fit the inside the engine and job is done I have this 1.9 DFZ pistons fitted in my 1.9 D6B engine and it works just fine there was no problems except ignition timing (you will need regraph your dizzy to suit this CR or go for mappable ignition ..) , anyway the engine now has great torque all over the rev range it feels much stronger than before i like this ! Together with your current specs - webers and rally cam , this raising CR modification will be like cherry on the cake (but if i where you i will reconsider a bit of head porting and 3angle valve seats etc. with all this mods this could be very nice combination in the end ) Cheers ! Damir Edited October 10, 2007 by DamirGTI Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 10, 2007 Hi ! Me thinks that fitting different (flat top) pistons is better solution for raising CR than go for a heavy head skim (in the end if you don't like the end result of that modification you can always remove them and fit back the standard pistons ..) You can expect gain of around 11.1 (or as high as 12.3 ..) CR when using 1.6 pistons (they have just slightly dished area ..) in 1.9 engine , but the most easier way is to find set of 1.9 DFZ pistons , they are exactly the same size and crown shape as the ones inside 1.6 engines , but the easier bit is that you don't need to replace conrods as they are the same length as the ones on 1.9 D6B dished pistons .... if you chose 1.6 pistons you will need to press out 1.6 conrods and press in 1.9 conrods which is a bit hard job and one of the pistons can be damaged during this pressing out pressing in - it's much easier to find good set of 1.9 DFZ pistons and you just need to clean them , fit new piston rings fit the inside the engine and job is done I have this 1.9 DFZ pistons fitted in my 1.9 D6B engine and it works just fine there was no problems except ignition timing (you will need regraph your dizzy to suit this CR or go for mappable ignition ..) , anyway the engine now has great torque all over the rev range it feels much stronger than before i like this ! Together with your current specs - webers and rally cam , this raising CR modification will be like cherry on the cake (but if i where you i will reconsider a bit of head porting and 3angle valve seats etc. with all this mods this could be very nice combination in the end ) Cheers ! Damir hi mate thanx for the reply fittin new pistons sounds like far too much hard work, i thought it was easier to work out how much you could take from the head, they are brand new pistons and liners fitted already so im kinda reluctant to remove them and have to sourse some others what the methods for findin out how much can be skimmed from the head?! the year after this head will become a BV head but will retain the same cam so im happy in skimming the head really, i havent yet looked into 3 angle seats, i think that'll also come along with the BV head conversion thanx for the info Simon Share this post Link to post Share on other sites
brianthemagical 1 Posted October 11, 2007 best thing to do is go off the dynamic compression ratio, try google. Share this post Link to post Share on other sites
DamirGTI 345 Posted October 11, 2007 (edited) hi mate thanx for the reply fittin new pistons sounds like far too much hard work, i thought it was easier to work out how much you could take from the head, they are brand new pistons and liners fitted already so im kinda reluctant to remove them and have to sourse some others what the methods for findin out how much can be skimmed from the head?! the year after this head will become a BV head but will retain the same cam so im happy in skimming the head really, i havent yet looked into 3 angle seats, i think that'll also come along with the BV head conversion thanx for the info Simon Hello ! I really don't know how much you need to skim the head in order to achieve desired CR But if you wish i can scan you one page from the OE Peugeot workshop manual regarding how to measure the head ? Cheers ! Damir Edited October 11, 2007 by DamirGTI Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 11, 2007 Hello ! I really don't know how much you need to skim the head in order to achieve desired CR But if you wish i can scan you one page from the OE Peugeot workshop manual regarding how to measure the head ? Cheers ! Damir yeh that would be useful mate thanx alot Share this post Link to post Share on other sites
DamirGTI 345 Posted October 12, 2007 Hello ! No probs mate : http://s27.photobucket.com/albums/c151/Pie...rrent=19l8v.jpg Cheers ! Damir Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 16, 2007 thanx for the page mate, very useful, are the figures on that page the same for the XU9 head as with the XU10 head stated?! think i may have got the wrong end go the stick, whats the main way to increase the compression ratio?!! thats the main question is it, skimming the head, or fitting different different pistons and leaving the head skim alone thanx again Share this post Link to post Share on other sites
brianthemagical 1 Posted October 17, 2007 head skim or thiner gasket is the most. if you start messin around with pistons you can alter the flame propergation and swirl designed into the combustion chamber, thus possibly affecting (adversly) the performance. unless you know what you are doing/understand why they would work. you also need to try and use the dynamic compression ratio, which takes into acount the cam and opening of valves, unless you are given a figure from the cam manufacturer. Share this post Link to post Share on other sites
DamirGTI 345 Posted October 17, 2007 Hello ! Yes it's the same value for XU9 and XU10 heads .. As said , you can raise the CR with head skimming (i don't like heavy head skimming ..) , milling the block (this is good solution if you can find someone who will do this job properly..) or by fitting different pistons (which is better and easier solution me thinks.. + you can remove them if you don't like achieved CR ) and as long as you don't use high top pistons you will not have problems with the flame travel , ignition , combustion process etc. - use either flat top pistons or the best piston design is dished piston (lightly dished..) especially for this engine .. Also the piston crown shape must be the mirror image of the outline of the combustion chamber , which means that piston crown must have squish surface which exactly matches the cylinder head squish area . This is why i was recommend you 1.9 DFZ pistons as because they are same crown shape , same size , same squish surface as the pistons in 1.9 D6B or DKZ engine , but this DFZ pistons have smaller dish then D6B or DKZ pistons and fitting them inside D6B or DKZ engine you will gain around 11.1 - 12.3 CR ! Cheers ! Damir Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 17, 2007 i must say id like to steer away from changin pistons as the ones in teh engine i am building are brand new and plus next year id like to convert the engine to a 2000cc or 2100cc and so would be changin the pistons then anyway, if it wasnt for those id definitely go down the same route as Damir as he seems to have a good set up goin for him!! with the page that Damir scanned for me i am now able to measure how much the head has been skimmed so far and then contact the company from which im buyin the cam and ask whats the optimum head skim i can go to, like piper on their website say that if you fit the BP270 cam you should take off 0.28" as a head skim, so hopefully as im going for a Catcam they will be able to tell me what i can take off then simply measure it, see how close it is to the figures on the page from Damir and go from there to work out how much more to take off to get it to optimum and also somethin i havent touched on yet, what size head gasket to use with that head skim and cam!! fingures crossed they have these figures!! thanx for your help oh actually one more thing, whats milling the block?! Share this post Link to post Share on other sites
DamirGTI 345 Posted October 17, 2007 Hi ! Sure i agree with you , if the pistons are brand new item it will be shame to pull them out now and fit some reused . As for milling/skimming the block - well it's the same thing as skimming the head , milling/skimming the block surface all around up where goes the head gasket (the cylinder liners must be also skimmed together with block surface..) , understand ? However you must find a good "milling man" for this job Cheers ! Damir Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 17, 2007 Hi ! Sure i agree with you , if the pistons are brand new item it will be shame to pull them out now and fit some reused . As for milling/skimming the block - well it's the same thing as skimming the head , milling/skimming the block surface all around up where goes the head gasket (the cylinder liners must be also skimmed together with block surface..) , understand ? However you must find a good "milling man" for this job Cheers ! Damir ah ok thought it must have been somethin like that, we havent really got any good people that could do that in Guernsey so ill stick to teh head skim for now i think thanx for the advice anyway mate Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 30, 2007 Thought i'd let you know my findings, i spoke to Matt from Catcams yesterday (very helpful bloke) who advised that on a standard head with standard pistons your safe to take 60 thou (0.06") of the head via skim which will take the CR to 10.8 - 10.9, any more than this on standard pistons and ull loose reliability very very fast. Share this post Link to post Share on other sites
DamirGTI 345 Posted October 30, 2007 Hi ! Nice one ! thanks for info mate , it's always good when people report back with results Regards ! Damir Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 31, 2007 Ah damn it, have a hit a wall I have been told today that the standard figure for the head height as you gave me on that page for the XU10 wont be the same as the XU9 head. I really need to find this distance before i do anything, surely this has been looked into before as im not the first to skim a head to increase the CR, PLEASE HELP!! Share this post Link to post Share on other sites
DamirGTI 345 Posted October 31, 2007 Hi ! Well , no it's not same for XU9 and XU10 head.. For XU10 head says - maximum grinding dimensions = 0.2 mm , and this isn't from the Haynes book this is from OE Peugeot service book .. Regards Damir Share this post Link to post Share on other sites
Anthony 1,003 Posted October 31, 2007 For XU10 head says - maximum grinding dimensions = 0.2 mm , and this isn't from the Haynes book this is from OE Peugeot service book .. Careful how you interpret that - you can of course skim much more than that off an XU10 head (you need to skim off something like 1mm when fitting to an XU9 block for example), but the compression ratio will go up you'll need to alter things like ignition timing accordingly. The 0.2mm is the figure Peugeot will have come up with that they're happy that everything will run fine without alteration, and I'd imagine that 0.2mm is probably specified as needing to use a repair headgasket that's thicker than standard with as well. Share this post Link to post Share on other sites
DamirGTI 345 Posted October 31, 2007 (edited) Sure , i agree but this are just the figures from the Peugeot book : http://s27.photobucket.com/albums/c151/Pie...rrent=19l8v.jpg Regards Damir Edited October 31, 2007 by DamirGTI Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted October 31, 2007 so what exactly are the implications of taking a big skim off a head, ie detonation?! what will happen as i wanna take about 0.06 of my hillclimb pug for next year as thats what ive been told is the maximum for a XU9 head and block on standard pistons and liners which will up the CR to 10.9?! Share this post Link to post Share on other sites
