![]() Secondly, spend some time removing the sharp edges of the remaining squish pad in the combustion chamber and 'lay it back'. Personally I feel the best way to combat this is to do as was already suggested which is to un-shroud the valves which will probably eat into the material of the squish pad, remember, flow around the valve is more important. This creates a hot spot which can be the cause of detonation and other nasty things. This is seen as a good thing, however, the problem occurs when the fuel/air mixture is accelerated past a sharp edge like the edge of a squish pad and this gets worse when there is high rpm, high cylinder pressures, etc. The squish pads create an area of 'quench' which is a point where combustion will not occur. Have a look around here.you should know what to research from there.įirstly, there is not a lot of 'squish' pad in a 4-valve chamber anyway. We will only be touching the Quench pads to deshroud the valves to assist maximum breathing. Look at some Cosworth turbo era heads, champ car heads, look at the amount of quench left on them. We are aiming for a "easy" limited to 650 Kw at all 4 on mildish boost levels with E85 on a RB26/30, both quenches will remain, but will not look like the standard quech zones as made by the factory, both will be modified in shape and remain in place. If i was building 98 low boost, id leave them both there, 98 high power id take out one side, 98 full race id take them both out, by the nature of 98 octane its a bitch when boost starts getting cranked up. No gap, no detonation, quench in, maximum sonic speed pulse of the mixture while maintaining maximum compression (without resorting to one of pistons) Generally speaking the aim is for "around" 40 thou (1mm) Quench to piston deck clearance, this at full song should close to virtually "Zero" clearance with forged rods with ARP fasteners at around the 9K+ RPM mark (also allowing for piston rock at ATDC). ![]() Top engine builders work a little differently, and aim to reduce the piston to squish zone gap down to zero at full song, that is, to have the head and piston "just" kiss at full stretch of all components. Most of ths is due to secondary combustion, that is enough room was left there for combustion to take effect. The biggest negative with squish areas remaining is detonation, everyones seen quish zones with tell tale marks and shits themselves, taking them out. To take both squish zones out you will need a custom piston, theres a mob in the US who CNC the heads and remove the pads and supply specially designed pistons that work to correctly return compression.īut lets throw a spanner in the works and say that a flat top piston would be better for the burn, but wouldnt be good with the squish removed if you want higher compression. There are pros and cons, 98, E85, low boost or high boost?. This is going to be one of those threads again.(not in a bad way though) Comp ratio of something between 9.0-9.5:1 I believe the 8374 is going to be too small for such a large donk) I also believe the Porka 996 911 turbo doesn't have squish pads. I have noticed that JUN also do this too. When I was going through the build of the last head, it was advised that above 800 HP to take both out. The extra space in the chamber is easily sorted by a piston to suit so the disadvantage of the compression ratio dropping becomes a mute point. What i'm after is the best performing combination. It seem's that the pads are there for emissions and fuel economy, two things I couldn't give a toss about. The car definitely drove better from idle to redline than the previous head which had both pads in, throttle response was like a lightswitch. I chose B and I can't say it had a negative affect. I had the option of A) leaving both in, B) Removing the inlet, C) removing both. On my current engine, the head was ported by HKS Japan and combustion chamber CNC work was done by NAPREC Japan. Some guys almost puke at the thought of removing them, others swear by it. I've had a bit of a sniff around both SAU and the UK forum and the opinions are very inconsistant. ![]() I'm after some information about the pro's and con's of retaining/removing the squish pads in RB26 heads. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |