81 replies to this topic

[TheHood]

  Hi Winstar. I was thinking along those lines. I was also thinking of a 12:1 CR. Anybody else out their interested? 

I could possibly be interested. I was planning in using Z22YH pistons and rods for my rebuild but if there's a benefit in using something with a higher CR I could be talked into it...price dependant of course

You can get 12:1 CR with the yh rods and pistons by using a thinner head gasket, so to make aftermarket pistons / rods worthwhile they're going to need to be lighter, stronger or preferably both.

[vocky]

wiseco make 11:1 CR pistons to order, they have all the info required

 

Karo at www.allecotec.com sells them

[smiley]

wiseco make 11:1 CR pistons to order, they have all the info required

 

 

 

Not 4032 though right?

[yaaan]

You can get 12:1 CR with the yh rods and pistons by using a thinner head gasket, so to make aftermarket pistons / rods worthwhile they're going to need to be lighter, stronger or preferably both.

Interesting. Maybe I'll give this a go. Is there a specific size/thickness of gasket? Are there downsides to having a higher CR?

[speedster]

Are there downsides to having a higher CR?

 

From an engine perspective additional heat is probably the biggest downside. 

[yaaan]

Are there downsides to having a higher CR?  

From an engine perspective additional heat is probably the biggest downside. 

Would this be significant with an increased CR from 11 to 12? Would a 9% increase in CR result in a 9% increase in heat or is it not that simple? I guess this can always be compensated for with some extra venting.

[Arno]

 

Are there downsides to having a higher CR?

 

 

Knock/detonation tends to happen sooner when running a high(er) compression engine.

 

Depending on the cams, piston shape and combustion chamber profile it may mean that you either need to run/map the engine at 98RON or better fuel (limiting availablitly), or you need to reduce ignition advance to run 95RON and losing power if it's knock advance-limited before peak power is reached.

 

Hard to say exactly beforehand, although the rule of thumb usually is that wilder cams allow for a higher static compression as they 'lose' dynamic compression because of valve overlap (aka. they leak intake charge to the exhaust   )

 

Of course you could go mad and run only E85 and build a 14:1 or more compression engine

 

Bye, Arno.

[alanoo]

Try Wossner

 

They used to have Z22SE pistons in their catalogue but removed them like 3 years ago... Still they would most certainly have all the specs to do them again 

[slindborg]

Higher compression ratios on petrol engined applications can lead to higher combustion temperatures which can spank pistons harder than intended

[speedster]

Yes indeedy! 

The amount of additional heat depends on a number of factors, how the engine is breathing, what cams your using, fuel, the piston design, etc. For example an engine with smooth polished pistons runs cooler than one with non-polished pistons. A cool, smooth piston will transmit minimum heat to the incoming fuel air mix even after combustion deposits have turned pistons black. Venting is good but the main issue is how much heat is resident in the combustion chambers and are you approaching detonation/knock danger zone at any point. IMO the trick will be determining what cams to utilize in a high compression Z22SE engine when running with ITbs and pump fuel. 

 

 

[TheHood]

I've got a Webcon kit to go on my ~11.5:1CR engine that's running fairly short duration cams but this thread has got me thinking about how concerned I should be with the lack of knock detection on the Webcon ECU. I guess I'll find out when I CBA to fit it :-D

[vocky]

webcon checked for knock when they did the latest batch of maps for the 5 tooth trigger wheel

[yaaan]

So could 12:1 be made to work with Z22YH pistons and stage 3 comp cams? And would it make much difference, or would it just create extra unnecessary complications?

[TheHood]

IRC the head gasket for the LSJ engine is the one you're after. As to if it's a good idea there's only one way to find out :-D

[vocky]

So could 12:1 be made to work with Z22YH pistons and stage 3 comp cams? And would it make much difference, or would it just create extra unnecessary complications?

I choose 11.5:1 CR for my new engine just to be on the safe side

[yaaan]

IRC the head gasket for the LSJ engine is the one you're after. As to if it's a good idea there's only one way to find out :-D

Might be worth experimenting then. What's the worst that can happen?

[TheHood]

 

IRC the head gasket for the LSJ engine is the one you're after.

As to if it's a good idea there's only one way to find out :-D

Might be worth experimenting then. What's the worst that can happen?

 

 You buy a job lot of Millers EcoMax octane booster. I e-mailed the manufacturer a few years ago to clarify if their product added 0.1 octane like some of the rivals or 1 whole octane number and they replied saying the latter. It's actually not that bad value compared to some of the others as you only need 1ml / L, so with my "on it" mileage I only managed to get through 1 bottle in about 12 months!

 

More seriously THIS calculator should give you rough idea, although it makes no allowance for RPM or volumetric efficiency. Wikipedia gives L61 (z22se) bore of 3.4", stroke 3.72", rod length 5.55" sorry don't know your cam duration - maybe someone can jump in?

[speedster]

With 280* cams I got

 

 

[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]Static compression ratio of 12:1.[/color]
[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]Effective stroke is 2.49 inches.[/color]
[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]Your dynamic compression ratio is 8.36:1 .[/color]
[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]Your dynamic cranking pressure is 168.29 PSI.[/color]
[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.36 :1.[/color]
[color=rgb(0,0,0);font-family:'Times New Roman';font-size:medium;]V/P (Volume to Pressure Index) is 46[/color]

 

 

though I am not sure if 280 is the correct value for Inlet Valve Closes ABDC

 

Be great if it was

Edited by speedster, 13 July 2013 - 01:46 PM.

[yaaan]

 You buy a job lot of Millers EcoMax octane booster.

Would your everyday super unleaded/ shell vpower/98/99ron not be sufficient then, or would it just be a case of sucking it and see, and adding octane booster if necessary? I'm quite tempted to give it a go as a bit if an experiment, especially if I can fairly easily revert back to a more conventional 11:1 (barring any catastrophic failures in the process).

[TheHood]

With 280* cams I got
 

 [color=rgb(0,0,0);]Static compression ratio of 12:1.[/color]
[color=rgb(0,0,0);]Effective stroke is 2.49 inches.[/color]
[color=rgb(0,0,0);]Your dynamic compression ratio is 8.36:1 .[/color]
[color=rgb(0,0,0);]Your dynamic cranking pressure is 168.29 PSI.[/color]
[color=rgb(0,0,0);]Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.36 :1.[/color]
[color=rgb(0,0,0);]V/P (Volume to Pressure Index) is 46[/color]
 

 
though I am not sure if 280 is the correct value for Inlet Valve Closes ABDC
 
Be great if it was

That doesn't look right to me. Most of the inlet valve closing figures I've seen are much lower values than that. I've read about cam timing several times but I'm just too thick for it to stay in my head :-D

Yaan - I'd be using 99 RON and getting it on a rolling road capable of detecting knock before really spanking it for piece of mind if nothing else.