busa rods/pistons yeah again :-)

[rik1216]

aye up all got all the bits to do the yorkshire ( tight twat ) 1216 this time , im sick of being told differing on the spacer !! piston is shorter lower comp for turbo on standard rods but im running n/a so got the longer gen 1 rods so why are people saying i need a 2 mill ish spacer ? that in my eyes takes away the point in putting longer rods in ? pardon me if this a thick question or has been answered many times before :-)

[clivegto]

18 minutes ago, rik1216 said:

aye up all got all the bits to do the yorkshire ( tight twat ) 1216 this time , im sick of being told differing on the spacer !! piston is shorter lower comp for turbo on standard rods but im running n/a so got the longer gen 1 rods so why are people saying i need a 2 mill ish spacer ? that in my eyes takes away the point in putting longer rods in ? pardon me if this a thick question or has been answered many times before :-)

You need to do a dry build to find out. Have built a few turbo motors with this combo using a spacer plate. Give it a go but think the comp will still be low. There is a thread about this some where, do a search. 

[no class]

the wrist pin to top of piston dimensions vary  when comparing the busa  to the oil cooled 1127/1157 pistons......  the recessed dish on the busa piston adds to the lower comp ratio . the oil cooled 1127/1157 rods are 117mm and the busa 119.5 .....all share the same big and small ends at 41/20 . As Clive stated above , best to dry build and check your measurements.... so even when you achieve “0” deck height and proper .035-.040 squish with the busa combo .... the comp ratio will still be somewhat low compared to the 1127 and slightly lower comp 1157 .

[rik1216]

waiting for the barrels to come back and dry build it is :-)  ( still carnt see the point of a spacer ) surely someone has done this !!!

 

[clivegto]

2 hours ago, rik1216 said:

surely someone has done this !!!

 

Did think about it until I rode a turbo bike. 

[Gixer1460]

You'll need a spacer as with the longer rods the pistons pop out of the barrels - though that would be obvious?

[rik1216]

1 hour ago, Gixer1460 said:

You'll need a spacer as with the longer rods the pistons pop out of the barrels - though that would be obvious?

so why use busa rods why dont i just keep the standard ?

[no class]

busa rods are stronger than std gsf/ gsxr rods.... usualy a choice made by the builder when a turbo or n20 is on the menu .  dropping the pistons on the std rods will net you low 8’s on the comp figures.... not really a performance upgrade if going NA .... 

[no class]

..... you will need either a dot head or skim the std head to bring up the comp ratio .... but even that will just get you in the 9’s .

[rik1216]

1 hour ago, no class said:

busa rods are stronger than std gsf/ gsxr rods.... usualy a choice made by the builder when a turbo or n20 is on the menu .  dropping the pistons on the std rods will net you low 8’s on the comp figures.... not really a performance upgrade if going NA .... 

yeah i get this but the busa  rod is roughly the same difference as the piston difference so should cancel each other out the only reason i see from fitting a spacer with both gen 1 rods and pistons is to drop compression which i dont want :-)

[no class]

the spacer is used to correct the deck height....setting a proper squish (.035-.040) basically the thickness of a cometic mls head gasket ......it is an important to get this right .  there are other variables involved when mix matching rods (longer/ shorter)  piston speed , piston dwell time etc.... do your research .

[rik1216]

so what were saying is the actual shape of the gen 1 piston ( dished ) reduces the compression even when at correct squish ? so if running na the extra cc,s are at cost of compression right :-)

[no class]

correctamoooondo

[rik1216]

and your also saying that correct squish is roughly the thickness of a gasket hmm barrels back and lets see , my calcs should put the piston more or less flush with top of barrells with no spacer so nowhere near 2mm i rekon :-) cheers matey

[no class]

42 minutes ago, rik1216 said:

and your also saying that correct squish is roughly the thickness of a gasket 

a cometic mls head gasket ( gsxr 1216 application) ......yes... other gasket types may vary .... 

Edited March 31, 2020 by no class

[Gixer1460]

Be cautious just using gasket to determine squish. An uncompressed gasket maybe 1mm? but when compressed 0.5mm? but recommended safe squish is about 1mm (allows for rod stretch / avoidance of pre ignition) - some race engine builders go as tight as 0.5mm but really not advisable) So ideally you need the piston to be 0.5mm below deck height and allowing compressed gasket.

Busa piston with dish compared to std. GSXR piston with raised crown makes big difference in CR.

[rik1216]

46 minutes ago, Gixer1460 said:

Be cautious just using gasket to determine squish. An uncompressed gasket maybe 1mm? but when compressed 0.5mm? but recommended safe squish is about 1mm (allows for rod stretch / avoidance of pre ignition) - some race engine builders go as tight as 0.5mm but really not advisable) So ideally you need the piston to be 0.5mm below deck height and allowing compressed gasket.

Busa piston with dish compared to std. GSXR piston with raised crown makes big difference in CR.

cheers guys :-) soooo what im gathering from here is that 1mm squish on a fully built torqued down motor is good ? no problem with valve to piston clearance ? will do a full plasigauge test on a dry motor but im looking 1mm down to max .5 , its not being built to comute to work so just for fun and ive noticed the spacers do come in varieying thickness if needed , getting some good feedback on this much thanks lads :-)

[Duckndive]

Gen 1 Bus Piston on Stock 1127cc Rod  with stock head and cometic MLS gasket = 8.5:1 in round no,s  in my motor 

 

[rik1216]

hmm so thats standard rods with busa pistons ? no other alteration to barrells ,

[rik1216]

if so then the spacer will be needed as the gen 1 rods are longer :-)

[Duckndive]

41 minutes ago, rik1216 said:

hmm so thats standard rods with busa pistons ? no other alteration to barrells ,

as it says yeap block is blandit bored for the bus pistons 

as others have said you need to do a dry build using the components you intend to use

[rik1216]

yeah will do , just confusing people say differing things hmm cheers again chaps got all bits so ill pop in shed and use an old 1216 1127 set of mullered barrels to get a look at this whole spacer issue haha

[Gixer1460]

1 hour ago, rik1216 said:

 soooo what im gathering from here is that 1mm squish on a fully built torqued down motor is good ? no problem with valve to piston clearance ? 

Different question - squish could be fine but still get piston to valve contact - depends on cut outs and valve timing. Plasticine and dry build best way forward.

[rik1216]

yep mate the way forward haha

[XXXSpro]

On 3/31/2020 at 10:20 AM, rik1216 said:

yeah will do , just confusing people say differing things hmm cheers again chaps got all bits so ill pop in shed and use an old 1216 1127 set of mullered barrels to get a look at this whole spacer issue haha

Did you ever finish this build?

Im doing the exact same thing with a dot head and 1100f cams