Can high comp pistons be skimmed to low comp ?
02-09-2009, 12:00 PM
#42
Yes modern vehicles can do it, but not without at least one of the above ECU strategies in place and usually with a more suitable engine geometry.
02-09-2009, 12:24 PM
#43
Dearest Harvey,
Its Kevman from Scotland here, ken... I've got a minted Saph that I want to bang a built engine into and mock Stucos in his joe baxi, ken... So do I need high comp or low comp big man??
CheeRS.
Its Kevman from Scotland here, ken... I've got a minted Saph that I want to bang a built engine into and mock Stucos in his joe baxi, ken... So do I need high comp or low comp big man??
CheeRS.
Just copy and paste the above Kev, should get it sorted for you.
Cheers,
Grant
02-09-2009, 01:32 PM
#44
Or get stucos to write it...
Aye Harvey What's happenin eh? eh?
I was eh gonna eh build ma mate an eh engine eh and i says it wis better eh to use it as it was eh di yi no think eh?
But thon kev cunt says eh no i wint tae use it we a spec a'body kens eh? Ken fit i mean eh?
I think he's a dafty and wint you tae tell him he's a cunt and eh that 4x4 is for gays eh.
Pie Beans and chips it is for tea eh........
Stucos
Aye Harvey What's happenin eh? eh?
I was eh gonna eh build ma mate an eh engine eh and i says it wis better eh to use it as it was eh di yi no think eh?
But thon kev cunt says eh no i wint tae use it we a spec a'body kens eh? Ken fit i mean eh?
I think he's a dafty and wint you tae tell him he's a cunt and eh that 4x4 is for gays eh.
Pie Beans and chips it is for tea eh........
Stucos
02-09-2009, 01:37 PM
#45
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I tend to agree. Kev wants 450bhp from his motor now and for that I dont personally wouldnt be speccing 9.8:1 on pump fuel with an ecu that has no thermal management capabilities or active spark lead.
Yes modern vehicles can do it, but not without at least one of the above ECU strategies in place and usually with a more suitable engine geometry.
Yes modern vehicles can do it, but not without at least one of the above ECU strategies in place and usually with a more suitable engine geometry.
Stu,
what is 'active spark lead'? is this another name for using ion sensing to detect knock and then retard spark accordingly (as per saab trionic system for example)
02-09-2009, 02:32 PM
#47
Or get stucos to write it...
Aye Harvey What's happenin eh? eh?
I was eh gonna eh build ma mate an eh engine eh and i says it wis better eh to use it as it was eh di yi no think eh?
But thon kev cunt says eh no i wint tae use it we a spec a'body kens eh? Ken fit i mean eh?
I think he's a dafty and wint you tae tell him he's a cunt and eh that 4x4 is for gays eh.
Pie Beans and chips it is for tea eh........
Stucos
Aye Harvey What's happenin eh? eh?
I was eh gonna eh build ma mate an eh engine eh and i says it wis better eh to use it as it was eh di yi no think eh?
But thon kev cunt says eh no i wint tae use it we a spec a'body kens eh? Ken fit i mean eh?
I think he's a dafty and wint you tae tell him he's a cunt and eh that 4x4 is for gays eh.
Pie Beans and chips it is for tea eh........
Stucos
The above are utter fucking class gents i proper pissed myself at them.
Called harvey earlier and have to measure head and pistons then call him back.
02-09-2009, 06:44 PM
#48
PassionFord Post Whore!!
The Evo is 8.8-1 and I have run upto 9.5-1 at 600hp on pump fuel and I feel this is about the limit for the evo at that level,
The week link on the cossie is the head gasket more than anything else, the most I have run at high power is 8.7-1 I feel that 9-1 is about the limit on a road engine unless someone wanted me to test the limits
.Mark
02-09-2009, 08:13 PM
#49
maybe after seeing other top tuners saying the same as me you might want to rethink what your saying???everything stu and mark have said me and jimbo have basicaly already said...9.8 comp ratio is to high on a cossie engine,unless you want to be taking it apart alot..cheers danny
02-09-2009, 08:20 PM
#50
maybe after seeing other top tuners saying the same as me you might want to rethink what your saying???everything stu and mark have said me and jimbo have basicaly already said...9.8 comp ratio is to high on a cossie engine,unless you want to be taking it apart alot..cheers danny
you may want to re-read what i quoted pal, you stated that
"a turbo engine with that comp wont do as many miles as a lower comp one"
and your still wrong
a bit of an open ended statement really as there are so many variables to what you have said.
if you would have asked similar questions about differing CR 5 years ago, about using in the 8's never mind the 9's you would have been so worng and your engine would melt all day long. how things change.
if it wasnt for the likes of mark shead, people would still be in the low 7's with poor peaky engines. well done to mark for bringing it to the public domain, that it can be done like we knew already.
Last edited by markk; 02-09-2009 at 08:22 PM.
02-09-2009, 08:27 PM
#51
PassionFord Post Whore!!
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Kev,grant and chop dont think our english friend under stand the slang,chop i cant help my mixed dilect,ken fit i mean min.
chop answer your pm,
cheeRS stu
chop answer your pm,
cheeRS stu
02-09-2009, 08:33 PM
#54
you may want to re-read what i quoted pal, you stated that
"a turbo engine with that comp wont do as many miles as a lower comp one"
and your still wrong
a bit of an open ended statement really as there are so many variables to what you have said.
if you would have asked similar questions about differing CR 5 years ago, about using in the 8's never mind the 9's you would have been so worng and your engine would melt all day long. how things change.
if it wasnt for the likes of mark shead, people would still be in the low 7's with poor peaky engines. well done to mark for bringing it to the public domain, that it can be done like we knew already.
"a turbo engine with that comp wont do as many miles as a lower comp one"
and your still wrong
a bit of an open ended statement really as there are so many variables to what you have said.
if you would have asked similar questions about differing CR 5 years ago, about using in the 8's never mind the 9's you would have been so worng and your engine would melt all day long. how things change.
if it wasnt for the likes of mark shead, people would still be in the low 7's with poor peaky engines. well done to mark for bringing it to the public domain, that it can be done like we knew already.
02-09-2009, 08:40 PM
#57
yeah of course but i bet they are flat tops probably accralites and i bet the head has been skimmed alot...if so just bowl the pistons and it will be fine...iv done this a few times on similar engines...cheers danny
02-09-2009, 08:44 PM
#58
02-09-2009, 08:49 PM
#59
mate you dont no me or what cars iv had...i had 539 bhp at 8.1 cr in 98 so its got nothing to do with the likes of mark shead...my race car runs 8.6 on pump at 602 bhp so im not saying you cant run hc but theres a massive difference between that and 9.8...me and jimbo have said if you want a reliable highish bhp that will last you need to lower the cr...
I think the OP now knows what he wants to do, having spoken to the person who will be doing the work for him
02-09-2009, 08:55 PM
#60
having had a few 'well known' tuners engines apart i have an idea of what some tuners have been doing at certain specs pal
with all due respect mate - your right i dont know you, nor do i need to.
I think the OP now knows what he wants to do, having spoken to the person who will be doing the work for him
with all due respect mate - your right i dont know you, nor do i need to.
I think the OP now knows what he wants to do, having spoken to the person who will be doing the work for him
02-09-2009, 10:33 PM
#67
It Wasnt Me!
The way to go imo is if you want to use that engine, get some pistons that are lower comp to start with and sell those on ebay!
I dont see why lc engines are laggy/less responsive, I'd say that's down to the map/cams/turbo
I dont see why lc engines are laggy/less responsive, I'd say that's down to the map/cams/turbo
02-09-2009, 10:35 PM
#68
Anyone tuning an N/A engine (which is what a turbo engine is while its off boost essentially) will always look to increase the compression ratio as a general rule.
02-09-2009, 11:14 PM
#69
cheers danny
02-09-2009, 11:51 PM
#71
normaly at that cr they use flat tops and sometimes accralite either ones will have 6mm+ so no probs...for al we know like iv already said it could be an engine thats had a highly skimmed head but no matter what its not going to be a set of pistons that cant be machined to get required cr..mind you iv seen pistons on 92mm bores that finish short in the cylinder with heavily skimmed head...didnt like that route and if that was the case id start again...wished i could see some pics with head of cos then id no straight away.cheers danny
03-09-2009, 06:12 PM
#72
It Wasnt Me!
Chip, I believe running as high a comp ratio as you can get away with is the right answer for the application, boost, fuel etc if your on race fuel then higher comp and more ignition is fine, but this is a road car which will prob see 98ron at best, so IMO lower CR is the way to go in this instance..I dont think a low comp engine is any less responsive, look at Rapidcossie's for instance, his was on full boost by something like 3000 or 3500 rpm and it had a v.low CR...also never heard that car detonate once!
b19dfp,...if they are 'race' pistons im sure they will be as light as possible with not a lot of meat on them, machining a piston isnt the right way to do it...if its got a thick crown yea it's an option to machine a dish into them...also you mention why sell the pistons matched to the bores... err well you can get custom pistons made to whatever size/spec you desire
I dont know enough about it really to say right or wrong, only what I've heard/learned from my short experience in these things, but some of the things people come out with are just mental
b19dfp,...if they are 'race' pistons im sure they will be as light as possible with not a lot of meat on them, machining a piston isnt the right way to do it...if its got a thick crown yea it's an option to machine a dish into them...also you mention why sell the pistons matched to the bores... err well you can get custom pistons made to whatever size/spec you desire
I dont know enough about it really to say right or wrong, only what I've heard/learned from my short experience in these things, but some of the things people come out with are just mental
03-09-2009, 07:31 PM
#73
Chip, I believe running as high a comp ratio as you can get away with is the right answer for the application, boost, fuel etc if your on race fuel then higher comp and more ignition is fine, but this is a road car which will prob see 98ron at best, so IMO lower CR is the way to go in this instance..I dont think a low comp engine is any less responsive, look at Rapidcossie's for instance, his was on full boost by something like 3000 or 3500 rpm and it had a v.low CR...also never heard that car detonate once!
b19dfp,...if they are 'race' pistons im sure they will be as light as possible with not a lot of meat on them, machining a piston isnt the right way to do it...if its got a thick crown yea it's an option to machine a dish into them...also you mention why sell the pistons matched to the bores... err well you can get custom pistons made to whatever size/spec you desire
I dont know enough about it really to say right or wrong, only what I've heard/learned from my short experience in these things, but some of the things people come out with are just mental
b19dfp,...if they are 'race' pistons im sure they will be as light as possible with not a lot of meat on them, machining a piston isnt the right way to do it...if its got a thick crown yea it's an option to machine a dish into them...also you mention why sell the pistons matched to the bores... err well you can get custom pistons made to whatever size/spec you desire
I dont know enough about it really to say right or wrong, only what I've heard/learned from my short experience in these things, but some of the things people come out with are just mental
03-09-2009, 07:39 PM
#74
It Wasnt Me!
Ok, you sound like THE MAN when it comes to building engines.....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons uhu....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons
uhu....
03-09-2009, 07:53 PM
#75
Ok, you sound like THE MAN when it comes to building engines.....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons uhu....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons
uhu....
03-09-2009, 07:59 PM
#76
Ok, you sound like THE MAN when it comes to building engines.....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons uhu....
although I dont see why he cant get custom pistons just because the engine has run with the high comp pistons in it?.....whatever you say though as your clearly an expert!
9 out of 10 modified cossie engines with machined pistons
uhu....then there bore the block, but, is it on nikasil liners, is it at its limit of boring ? maybe a hone would do ! theres so many things that come into play, the engine needs stripping, looking at by someone who knows what theyre up to and making a desicion.
03-09-2009, 08:04 PM
#77
It Wasnt Me!
£600 from JE actually
why wouldnt a custom CNC machined piston be exact?
machine work? what...a hone?
The guy asked if pistons can be machined, aye they can...is it right? NO
should he buy low comp,....IMO YES
amount of shite that's posted on here these days is un-real, i'll leave you's to spout amongst yourselfs
03-09-2009, 08:15 PM
#78
would you fancy shelling out another 7,8,900 pound for custom pistons when youve just bought an engine, not to mention nearly all custom pistons arnt going to be exact so will also need machine work done, thats another £100+ so you could be up to a grand,
then there bore the block, but, is it on nikasil liners, is it at its limit of boring ? maybe a hone would do ! theres so many things that come into play, the engine needs stripping, looking at by someone who knows what theyre up to and making a desicion.
then there bore the block, but, is it on nikasil liners, is it at its limit of boring ? maybe a hone would do ! theres so many things that come into play, the engine needs stripping, looking at by someone who knows what theyre up to and making a desicion.
03-09-2009, 08:37 PM
#79
£600 from JE actually
why wouldnt a custom CNC machined piston be exact?
machine work? what...a hone?
The guy asked if pistons can be machined, aye they can...is it right? NO
should he buy low comp,....IMO YES
amount of shite that's posted on here these days is un-real, i'll leave you's to spout amongst yourselfs
why wouldnt a custom CNC machined piston be exact?
machine work? what...a hone?
The guy asked if pistons can be machined, aye they can...is it right? NO
should he buy low comp,....IMO YES
amount of shite that's posted on here these days is un-real, i'll leave you's to spout amongst yourselfs
you order a set of custom pistons, go for it, put them straight in your engine, and watch them hit the head, every time, piston manafacturers will normally make the pistons slightly bigger, you can machine them down, cant put more back on them
every tuner on the forum and in the world most likely machine pistons day in day out,
we order custom sets, but do you take the chance that the company are going to be right ? on a 25k 800odd bhp build ? nope didnt think so,
dont know if you know, but when building engines you leave certain abouts of piston out of the block, 6, 8 , 10 thou for example, the custom pistons arnt going to be within thousands of an inch.
also what if the block is faced and slightly more was taken off the further towards you get to the back of the block,
each piston is going to need a different amount taking off the top to be the same as the others,
but then, when your taking material off the top, your loosing area in that bowl, therefore raising the compression ratio, so now you have to take some material out of the bowl area to compensate for that,
custom pistons, WONT go straight in
jim
hi ya jimbo,u normaly no me as 600 bhp escos but i rememberd my old password so im back to b19 dfp...any way its funny how we are reading from the same page ah??imagine if we couldnt machine pistons???we would have to give up tomo...mind you we could pick up the phone and ring cambridge motor sport and buy some je pistons that could work for any app we ever needed...lol cheers danny
03-09-2009, 08:41 PM
#80
machining pistons is always a cheaper alternative, not always the best alternative, if you are so much the pro b19, then you would recommend the correct custom piston to suit the spec that would not need machining if you have given the correct spec, but then again, you would just get harvey to build it for you from what i can gather on here.