Rb25 And 26 Squish Pad Removal And Cr

[Chris Wilson]

RB25 and RB26 squish pad removal adds a LOT of extra volume to the combustion chamber, yet when I see this recommended or suggested I never see any mention of how the compression ratio is brought back up to a sensible level. Off the shelf pistons seem to be used and a 0.9 mm head gasket is as thin as any I have come upon. So what CR are people getting with a full squish pad removal, and how are they achieving a figure close to stock? I am not asking as to why the practice is recommended or discouraged on the vasis of combustion, I am purely interested in how a sensible CR is achieved once they are both gone Thanks.

[proengines]

Endyne make a piston to suit the heads they do with the pads removed.

[bigmikespec]

Yeah they get a compression of 9.0 (static) or thereabouts with their roller wave pistons... could a company like CP custom make pistons to suit a modified combustion chamber with squish pads removed?

[SimonR32]

Endyne make a piston to suit the heads they do with the pads removed.

my question is are they any good?!?

[GTScotT]

someone want to go a little further into detail? could be a very usefull thread if how removing squish pads effects CR was added in somewhere.

IE the squish pad is X and removing makes the head sit closer/further to/from the block thus giving higher/lower CR.

as people like me would like to know more about the little terms they have heard without making new pointless threads.

Thanks!

[T04GTR]

seems to be only used on full tilt motors. ie massive boost and high rpm. ie said motors arnt required to have "as much" torque down low (ie big turbos) so the lower comp whatever it may be, is not at the front of the line in the engines purpose.

hope that sheds some light. ie: street. no pad removal,street/race, exhaust removed, full race, both removed.

would be a nice trick on a rb30 using 25 pistons and asociated block decking having a full tilt head still with 9 or so comp.

[Beer Baron]

seems to be only used on full tilt motors. ie massive boost and high rpm. ie said motors arnt required to have "as much" torque down low (ie big turbos) so the lower comp whatever it may be, is not at the front of the line in the engines purpose.

hope that sheds some light. ie: street. no pad removal,street/race, exhaust removed, full race, both removed.

would be a nice trick on a rb30 using 25 pistons and asociated block decking having a full tilt head still with 9 or so comp.

exactly the same as my experience. the guys that do both sides and full tilt heads are not worried about the loss of static CR as they are making up for it with big timing numbers and LOTS of BOOST. so the short answer is they just live with the lower static CR as the other benefits they get is what they are after. and the rule of thumb is the same as what I've seen/used too. street = standard, street/race exhaust side gone. full race both sides gone.

apparently the endyne stuff is kick ass. I would like to try one of their heads and roller wave piston set-ups one day....

[PM-R33]

Yeah similar stuff that i researched into when i got my head done. For a street car don't remove them, big HP car not worried with low down power loss, do it.

[Lukas 33]

I wonder.......does rob (R.I.P.S) remove his pads in his high hp cars?

[T04GTR]

id imagine so.

[T04GTR]

but when it come to engine combustion chamber/cam set up, its all abit of a black art in this country, only japan and usa seem to be openly sharing there r and d on the net..

[Lukas 33]

but when it come to engine combustion chamber/cam set up, its all abit of a black art in this country, only japan and usa seem to be openly sharing there r and d on the net..

Yeh I agree with you there. Sucks but I guess that is what they need to do to stay ahead of the game. Not like they can patent it haha

[Beer Baron]

but when it come to engine combustion chamber/cam set up, its all abit of a black art in this country, only japan and usa seem to be openly sharing there r and d on the net..

it's the same with everything. especially the USA. they love to share their developments etc on the net, and people can easily learn from it. here in aus people keep stuff much closer to their chest as they don't want competitors learning all their secrets.

[Swiper the Fox]

it's the same with everything. especially the USA. they love to share their developments etc on the net, and people can easily learn from it. here in aus people keep stuff much closer to their chest as they don't want competitors learning all their secrets.

not me...i tell all...thats what this place is all about.

some food for thought...lowering the static comp allows more charge to enter the combustion chamber. The more charge the bigger the bang.

It works well in our own engines....remember a boosted engine the cylinder pressure is multiplyed than would otherwise be seen if it was atmo as the air is being rammed in and not pulled in under vacuum.

Edited January 14, 2010 by DiRTgarage

[MrStabby]

not me...i tell all...thats what this place is all about.

some food for thought...lowering the static comp allows more charge to enter the combustion chamber.

How does that work? I would have thought the effect of static CR would be negligible on cylinder filling as the piston wont be anywhere near TDC when the inlet valve is open - right?

[Rezlo]

There is no real doubt that street = stock, race = exhaust removed, full race = both

When in the US we did this to a few high HP mitsubishi's, but each time we used a custom piston design for open camber usage.

What effect do you think using the regular style RB piston which is clearly been design for quench pads has on maintaining the correct swirl and fire path?

Yes a correct setup will be a lot less likely to detonate due to the open chamber, but in the real world where the 2jz can make 1000hp+ on the stock quench padded head (near identical in design to the RB) is it somthing that is really worth while unless the vehicle is a fully dedicated race car that really is pushing the limit? I know I wouldnt bother

[Beer Baron]

not me...i tell all...thats what this place is all about.

yeah agree on that point. and yeah there are still lots of good smart guys in aus who share stuff too. but just in general aus workshops play things much closer to the chest and don't want to give away hard earned knowledge/tricks etc. which is fair enough. it seems in the US their desire to show how smart they are overtakes the desire to keeps things secret! which is good.