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1157 -> 1216 Forged Piston Question - Raising Compression


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Started ordering parts for my 1157 engine build, shooting for 400+ to the wheel. Have a set of h-beam conrods on order right now, trying to work out which Hayabusa pistons to go with but I'm confused on compression numbers. From what I understand, stock Hayabusa pistons in an 1157/stock crank/stock rod length will net around 8.5:1 compression, which is perfect for boost, but I'm looking to go beyond the capabilities of stock Hayabusa pistons. All forged pistons for the Hayabusa seem to be either high compression (13:1ish) or low compression (8.5:1ish), neither of which would land at an ideal compression for a turbo 1216.

Never built an engine before, I don't understand much about metallurgy or piston design so forgive the amateurish questions:

  1. Am I even on the right track thinking that 8.5:1 Hayabusa pistons in an 1157 would net an insanely low compression ratio, due to the drop in compression ratio with stock Hayabusa 11:1 pistons? IE Stock 11:1 Hayabusa pistons in an 1157 nets ~8.5:1, therefor 8.5:1 Hayabusa pistons in an 1157 would net ~6.5:1? Or am I oversimplifying it?
  2. Between the JE, Wiseco, and Carrillo pistons, which are generally regarded as having the highest power capabilities? Alternatively, which are the best value for the money?
  3. What part of the 1157 could be shaved off to raise compression, assuming I get the 8.5:1 Hayabusa pistons? Alternatively, as I understand there's some head that bolts on to the 1157 that raises compression ratio about 1.5 points due to a smaller chamber, is this correct?

I understand I'll have to mathematically work out what specifically will need to happen with my engine to get my specific build where I want it in terms of compression, I just want to make sure that I'm on the right track before ordering pistons, lest I end up with something completely unusable.

Thanks

Edited by rider384
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9 minutes ago, george 1100 said:

you could get the high comp pistons then play with block spacers

My only worry with that is whether or not the turbo pistons/high comp pistons are different in terms of design - how it spreads the load, how it handles boost (regardless of compression ratio). As I said, I know almost nothing about piston design so I'm hoping someone who's gone down the fully built engine road can chime in. 

4 minutes ago, SiBag said:

I would have thought someone would make forged turbo 1216 pistons for the blandid / gsxr motor. Would make more sense than trying to fit aftermarket pistons from another engine.

Holeshot makes an 11:1 piston kit for the 1157, but that's about it as far as I can tell. It's so little work to fit Hayabusa pistons (bore the cylinder jugs 2mm over) that no one really makes bespoke Bandit pistons. I'm just struggling to find information on how to make the compression difference work. 

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4 hours ago, rider384 said:

Never built an engine before, I don't understand much about metallurgy or piston design so forgive the amateurish questions:

  1. Am I even on the right track thinking that 8.5:1 Hayabusa pistons in an 1157 would net an insanely low compression ratio, due to the drop in compression ratio with stock Hayabusa 11:1 pistons? IE Stock 11:1 Hayabusa pistons in an 1157 nets ~8.5:1, therefor 8.5:1 Hayabusa pistons in an 1157 would net ~6.5:1? Or am I oversimplifying it? NO - That's about right and would allow some insane boost lbs but bit of a slug 'off boost'
  2. Between the JE, Wiseco, and Carrillo pistons, which are generally regarded as having the highest power capabilities? Alternatively, which are the best value for the money? Didn't know Carillo made pistons! Nevermind, The Daddy of Turbo Pistons are MTC and they deffo do a 1216 GSXR / GSF turbo fitment ! BTW the highest power capability piston is the one that doesn't fail - they are all good, it's the tuning that usually isn't ! ! ! There are other manufacturers - often pistons can be repurposed from other uses - I have Cosworth pistons in my Turbo for example!
  3. What part of the 1157 could be shaved off to raise compression, assuming I get the 8.5:1 Hayabusa pistons? Alternatively, as I understand there's some head that bolts on to the 1157 that raises compression ratio about 1.5 points due to a smaller chamber, is this correct? You can't shave metal off to raise compression ! ! ! And your understanding about 'head bolts' is internet bollux! CR is raised by less chamber volume - shave the head or increase piston height.

Answers in RED

3 hours ago, rider384 said:

My only worry with that is whether or not the turbo pistons/high comp pistons are different in terms of design - how it spreads the load, how it handles boost (regardless of compression ratio). As I said, I know almost nothing about piston design so I'm hoping someone who's gone down the fully built engine road can chime in.  A piston for a particular application is just a piston - it will vary only by the CR it gives (using same rotating components) and its weight. A turbo piston may have additional work done to it to suit its application (usually by the engine builder to reduce likelihood of detonation (turbo engine / piston killer) especially required when using stock busa pistons !

Holeshot makes an 11:1 piston kit for the 1157, but that's about it as far as I can tell. It's so little work to fit Hayabusa pistons (bore the cylinder jugs 2mm over) that no one really makes bespoke Bandit pistons. I'm just struggling to find information on how to make the compression difference work. Stop restricting yourself to looking for Blandit parts - they aren't a 'performance bike' so no one will make parts that are unlikely to be purchased - Look for GSXR parts and the world opens up - APE, Orient Express, MTC, MRE, Star Racing - all names in the States that do / used to do much GSXR oil burner tuning stuff!

 

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On some engines the base of the cylinder(s) can be machined. This lowers the cylinder and the head and raises compression. It also moves the valvetrain closer to the crank, so take a good hard look before proceeding (then repeat another few times). As well as mounting bolts on everything that is lowered, move down. But that's probably negligeable.

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2 hours ago, TLRS said:

On some engines the base of the cylinder(s) can be machined. This lowers the cylinder and the head and raises compression. It also moves the valvetrain closer to the crank, so take a good hard look before proceeding (then repeat another few times). As well as mounting bolts on everything that is lowered, move down. But that's probably negligeable.

Why do that as it's easier to deck the top of the barrels - don't have to remove liners either!

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3 hours ago, TLRS said:

On some engines the base of the cylinder(s) can be machined. This lowers the cylinder and the head and raises compression. It also moves the valvetrain closer to the crank, so take a good hard look before proceeding (then repeat another few times). As well as mounting bolts on everything that is lowered, move down. But that's probably negligeable.

Or don't fit the base gasket. 

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Posted (edited)
35 minutes ago, wraith said:

Just a question,

If you're looking for 400+ bhp and just putting a 1216 kit in is going to mean one hell a lot of boost etc, why don't you go for a bigger bore? 

Say 1340 with turbo?

Is it possible to bore the cylinders out that much on a stock B12 block? I remember reading something about a "big block", but from what I can gather the Blandit 1200 engine is the big block. Going bigger would definitely help reach the goal. 

Also, unrelated to that, the B12 block is a 59mm crank, correct?

Edited by rider384
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Thanks for the words everyone, especially Gixer1460!

I ordered up some MTC 1216 10:1 pistons with upgraded tool steel wrist pins, part #MTC-R1216T

Going to do my best to track down some sort of head spacer to drop the compression down to 8.5:1 to be a little safer and find someone to bore out my jugs (heh). 

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13 hours ago, rider384 said:
14 hours ago, rider384 said:

Is it possible to bore the cylinders out that much on a stock B12 block? No, it isn't possible! I remember reading something about a "big block", but from what I can gather the Blandit 1200 engine is the big block. Also, no it isn't. It has slightly bigger diameter liners but is still essentially a 1127 / 1157 block casting. Going bigger would definitely help reach the goal. If you want bigger ie. 1317, 1340 and larger you need a specific 'Gorilla' block that used to be made by APE - these are no longer available and good one's are pretty scarce or you machine up a block out of billet and drop whatever liners you want in - my route with 86mm pistons.

Also, unrelated to that, the B12 block is a 59mm crank, correct? It is, same as GSXR 1127.

I ordered up some MTC 1216 10:1 pistons with upgraded tool steel wrist pins, part #MTC-R1216T

These are good pistons and rather than spacer the block to drop the CR, personally i'd machine the piston crowns (which I believe are flat on these) to add a slight dish. This does two things, first it preserves the squish band which is beneficial for anti detonation and secondly it puts a concentrated mixture right below the ignition source for the best burn. I've done the spacer thing (cos I had 12.5:1 pistons LOL) but it ruins the squish and not good for outright power IMO.

Going to do my best to track down some sort of head spacer to drop the compression down to 8.5:1 to be a little safer and find someone to bore out my jugs (heh). See above

Answers in RED again.

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