Compression Ratio

[Drifter27_04]

Can anyone tell me there thoughts on the matter.

I have purchased wiseco 8.2-1 ratio +20 pistons for my rebuild. I have had a few friends asked if I was going to do anything to my head to make the difference. I am running the B16G as of now with the motor until first of next year sometime than will be upgrading to a larger turbo. Would this pistons hurt me with the 16g now and what should I look towards to with this setup and would this ratio not be better for larger turbo setup like as in a 20g, 50-1, or 60-1

 

[iwantawd]

im not sure what you are saying, you have a stock 7.8:1 CR so raising it to 8.2:1 will only do good things for you.

 

[Drifter27_04]

I guess what I am trying to say is......whats the difference going to make with a 8.2 CR than a 8.8 CR Wiseco +20 bore piston? Some said that I should have went with the 8.8 with the B16g. Why are they saying this and what negative things do I need to know about running the B16g with the 8.2 CR. Isn't a lower CR betty for a turbo car. PLease forgive me if this still does not makes any sense as this is my first rebuild and new to the DSM world still. WTF

 

[loweperf]

I guess what I am trying to say is......whats the difference going to make with a 8.2 CR than a 8.8 CR Wiseco +20 bore piston? Some said that I should have went with the 8.8 with the B16g. Why are they saying this and what negative things do I need to know about running the B16g with the 8.2 CR. Isn't a lower CR betty for a turbo car. PLease forgive me if this still does not makes any sense as this is my first rebuild and new to the DSM world still. WTF

You probably won't know the difference in 8.2 to 8.8. Rule of thumb is the more compression you run the more power you will produce. A small hemi shaped combustion chamber,aluminum head,small bore,centrally located spark plug as on a DSM will tolerate about 11.1 CR on pump gas. Now add a turbo and you will want to lower the CR because more boost- lower CR will give more power than the higher CR with less boost. It's a trade off. More compression will give it more power before the turbo spools up but if you keep the CR down you can crank up the boost!

 

[Drifter27_04]

You probably won't know the difference in 8.2 to 8.8. Rule of thumb is the more compression you run the more power you will produce. A small hemi shaped combustion chamber,aluminum head,small bore,centrally located spark plug as on a DSM will tolerate about 11.1 CR on pump gas. Now add a turbo and you will want to lower the CR because more boost- lower CR will give more power than the higher CR with less boost. It's a trade off. More compression will give it more power before the turbo spools up but if you keep the CR down you can crank up the boost!

Yes it is making more since to me now but still blurry to me. I am wanting to run 25-30psi eventually when I upgrade to a larger turbo. Thanks man.

 

[loweperf]

You can depending on the octane. I run 9.2 CR with 30+ psi and 20 degrees timing with no knock,but that's with 114 race gas.

 

[Drifter27_04]

You can depending on the octane. I run 9.2 CR with 30+ psi and 20 degrees timing with no knock,but that's with 114 race gas.

So when upgrading to a larger turbo its only helping me for later down the road with the lower CR.

What is the stock CR....7.8? If this is correct this means that I have increased the time of spool up for my 16g and also means running 20-25psi will be no problem with everyday driving on 93 octane.

I also plan adding a small shot of NOS a year or so down the road....will the low CR help there as well?

Again thanks for all the shared knowledge.

 

[loweperf]

I wouldn't say running 25 psi on pump is not a problem. It probably won't happen, but you will be able to run more boost on pump than someone with say 9.0 CR. Nitrous and a lower CR is about the same. The more CR you can run the more power the engine will make. The trick is to run as much as possible on the octane you have. Given a high CR or more boost I'd choose more boost anytime. Also remember that boost does not make power-airflow does. Put 1/2" diameter valves in your head or weld up the ports and boost pressure goes up,but it does nothing to get air into the engine. That's why a 16g at 20 psi doesn't make as much power as say my T-66 at 15 psi.

 

[Drifter27_04]

I wouldn't say running 25 psi on pump is not a problem. It probably won't happen, but you will be able to run more boost on pump than someone with say 9.0 CR. Nitrous and a lower CR is about the same. The more CR you can run the more power the engine will make. The trick is to run as much as possible on the octane you have. Given a high CR or more boost I'd choose more boost anytime. Also remember that boost does not make power-airflow does. Put 1/2" diameter valves in your head or weld up the ports and boost pressure goes up,but it does nothing to get air into the engine. That's why a 16g at 20 psi doesn't make as much power as say my T-66 at 15 psi.

Running the 8.2 CR will I have a hard time to achive say 450whp? Check my mods out and let me know your thoughts on what numbers I could possibly be looking at just for what I have and some thoughts that you may recommend.

 

[iwantawd]

my thoughts are that someone of your level could greatly benefit from 2 books, maximum boost by corky bell and forced induction performance tuning by a. graham bell. you'll never come close to your power goal if you dont understand how an engine works.

 

[Drifter27_04]

my thoughts are that someone of your level could greatly benefit from 2 books, maximum boost by corky bell and forced induction performance tuning by a. graham bell. you'll never come close to your power goal if you dont understand how an engine works.

I know how an engine works and things of that nature, not a beginner in motors just not familer with the 4cyl turbo motors. I will be honest I had a decision of getting a Mustang and building it (as I am familer with)or a Talon (not much knowledge on it). I believe I had made the right decision. But to answer my question will I be able to see 450whp in the future with the mods I have now with little extras of course?

 

[Injected]

Your on the right track. You've set a goal (450whp) and now you have to figure out how to get there. 450 on a B16G isn't really that realistic (there's another thread and they all were in the 280-320 range). You'll need a turbo that is more efficient in the range that you are talking about running on 93 octane (low to mid 20 psi). I'm not about to suggest a turbo for you, you'll hear everyone else give their own input on which they think is the best turbo. I suggest looking at compressor maps, dyno sheets, etc. for information.

The compression ratio tradeoff goes like this: Let's assume you have a naturally aspirated engine, you could handle 11:1 compression without fear of the pressure generated during the compression stroke creating detonation. Remember as you compress air, it gets hotter. If you pressurize the air that is in the cylinder (i.e. super or turbo charging), then you will definitely detonate. Nothing kills a turbo engine faster than severe detonation, except driving like an asshat. So let's say that you lower it to say 10:1 (arbitrary). You could probably get away with up to 10 psi without the risk of pressure generated detonation. 9:1 20 psi. You are now close to your range and I'd say that 8.8:1 on a mild tune and 24 psi could get you to your goal, but you will have to spend the time and the money tuning. I hope this is the answer you were looking for. Why is it I still only have 10 rep points? they're such a rip. !

 

[Drifter27_04]

Your on the right track. You've set a goal (450whp) and now you have to figure out how to get there. 450 on a B16G isn't really that realistic (there's another thread and they all were in the 280-320 range). You'll need a turbo that is more efficient in the range that you are talking about running on 93 octane (low to mid 20 psi). I'm not about to suggest a turbo for you, you'll hear everyone else give their own input on which they think is the best turbo. I suggest looking at compressor maps, dyno sheets, etc. for information.

The compression ratio tradeoff goes like this: Let's assume you have a naturally aspirated engine, you could handle 11:1 compression without fear of the pressure generated during the compression stroke creating detonation. Remember as you compress air, it gets hotter. If you pressurize the air that is in the cylinder (i.e. super or turbo charging), then you will definitely detonate. Nothing kills a turbo engine faster than severe detonation, except driving like an asshat. So let's say that you lower it to say 10:1 (arbitrary). You could probably get away with up to 10 psi without the risk of pressure generated detonation. 9:1 20 psi. You are now close to your range and I'd say that 8.8:1 on a mild tune and 24 psi could get you to your goal, but you will have to spend the time and the money tuning. I hope this is the answer you were looking for. Why is it I still only have 10 rep points? they're such a rip. !

Thanks Injected for the info!

I tend to break the motor in more so with the b16g for awhile afterwards and fully aware of the limitations of the HP it can produce. I have been looking into the 20G or FP but as you mention I have been looking around and still not for sure. I do have one thing in mind is that I will want something to be a straight bolt on turbo with what I have.

As you can see that my CR is 8.2:1, so from what I have been told and read up on is that I will be able to crank the boost way up when I upgrade the turbo w/o detation earlier than have a higher CR piston. Being that stock is 7.8:1 the 8.2:1 will help in spool up some than stock would as well and still give me all the top end I maybe looking for.

 

[iwantawd]

who is doing the tuning? i also think you should still pick up one or both of those books, just cause you think you know how a NA v8 works doesnt mean anything about these engines, its not like CR is new just to 4cyl engines.

btw youre going to need to upgrade that clutch.

 

[Drifter27_04]

what are you doing as far as fuel mods go, you couldnt turn up your turbo now let alone a bigger one and who is doing the tuning?

After I get things put togather I will install a aeromotive FPR. FFWD has recently produce there on setup and I thought about looking into buying it b/c the so call hassel free job to install it and also I will than install larger Fuel Injectors.

There is a local guy I know that will tune the car for me until I have everthing bolted on and than I will have the car dynoed. Any other questions that you have that brings any concerns please ask. Forgive me as my profile is not fully filled out with what I have in mind of building.