I am building a B16B in my 99 hatchback and I need to know if it's gonna be worth me spending the extra 450 to go up one full point of compression. I have searched and I can't find crap. The motor is not daily driven, and I have talked with my tuner and he has tuned 12.5 compression motors to max hp at 15 degrees advanced timing. My motor setup is this.....

Stock type r TB/IM
RC 310's
255 fuel pump
H-data s100
RM M22x
RM valvetrain
stock type r head/valves
DTR header
J's test pipe into Spoon exhaust

This is BEFORE I dump pistons in it. As is right now I'm at 11.1, but Jeff from IB is tryin to sell me some pistons that will get me to 12.1. My only issue with them is that they are a 9.3cc dome and I am concerned with the flame travel. Assuming the motor reaches MAYBE 5k per year, is that extra point of compression gonna give me that much? Thankyou for any help or advice, later fellas

 

It all depends on what your goals with the motor are. If its a daily driver and you dont plan to race that often, then the 11:1 is good enough. You dont need that 1 point in compression.

If you are trying to go max HP possible and that extra 10-20 possible HP, then yes its a good idea to go 12:1

When we do an engine build consultation, we always look at the type of driving the customer does, goals for the car(short term and long term), complimenting parts you already have and of course budget.
Each person is not the same and you have to figure out what is best for you.

 

I don't drive my car hard, and of course I want the maximum power out of it as possible. I'm hoping to run deep 13's or high 12's on this build, the car is somewhat lightened and it's on slicks. If it will give me another 10hp to the ground I'll do it, just didn't know if it would give me that much or not.

 

those cams will work alot better with that extra point of compression.

 

The going with more compression is for you. like eddicut said, it'll work better with more compression.

 

power grows exponential with high compression in a natural aspirated setup. if you'll go with aftermarket pistons conside bigger bore as well ...

you can always go with 12:1 and still have conservative timing, you can also do longer rod length setup (slower piston speed which won't outrun flamefront as fast) ... I use the Endyn rollerwaves with timing as high as 31 at WOT/full load on pump gas for the small displacement motors ... with very good results.

the larger bored 2 liter setups don;t need as much timing.

Greg

 

run the higher compression.....i have around 12.6-7:1 comp ratio with itr intake and gsr ex cam which means high cylinder pressures due to like no overlap...i run on good old cali 91 octane with my base timing at about 14btdc with this timing map...runs like raped ape...no ping or problems yet

 

Wow thanks for your help guys!

 

What did you tune your 12.6-7:1 motor with? Curious cause I too am going nuts with compression and am trying to avoid dropping the bills for an E.M.S. all I have is a uni-chip.

 

Match the compression to the octane you will be running and go from there.

 

How would I go about doing that?

 

I dont want to start a controversy here, but in my opinion, 11-11.5:1 is right where you want to be on 91 octane gas with good tuning FOR A STREET MOTOR. You'll get better results most of the time using this compression. Even with big lift cams that 'love compression', this is a good range. With higher compression youll probably be able to put out some higher peak numbers with big cams, but the area under the curve might not be so great due to the inability to play with the timing as much. Just my .02.

 

I agree with you, I'm just trying to extract as much power out of this as possible. I'm at a disadvantage with being a .6 liter motor, but that what I wanted...something different. If the extra point of compression is only going to give me a few more hp up top, then I think I might just stick with what I have and put some flat valves in or something. Will the Omni or Supertech valves flow as well as the type r's, would it be worth it to have them worked over by Portflow?

 

compression + headwork makes power for all motor

11:1 is ***** compression for all motor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2k.civic.si &raquo;</TD></TR><TR><TD CLASS="quote">run the higher compression.....i have around 12.6-7:1 comp ratio with itr intake and gsr ex cam which means high cylinder pressures due to like no overlap...i run on good old cali 91 octane with my base timing at about 14btdc with this timing map...runs like raped ape...no ping or problems yet

</TD></TR></TABLE>

have u dynoed this yet?

 

11:1 is hardly '*****' compression. Certainly not for 91 octane. Hence the comment telling him to match the compression to the octane. You will detonate on 12:1 compression, even if you dont hear it.

 

its all about the tune when you decide to mess with compression.......

 

This is true, but have you ever heard high RPM full load, WOT detonation?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LsVtec92Hatch &raquo;</TD></TR><TR><TD CLASS="quote">11:1 is hardly '*****' compression. Certainly not for 91 octane. Hence the comment telling him to match the compression to the octane. You will detonate on 12:1 compression, even if you dont hear it. </TD></TR></TABLE>

I don't really agree with that. Dynamic compression is far more important to consider for octane tolerance than static compression. The cam choice can drastically affect dynamic comp.

That being said, I do think that 11:1 will be good for this combo. Its enough to get power out of the M22's and you can get more aggressive with the timing, as was mentioned before.

 

So I might as well just keep the pistons in it for now then from the way it sounds. I think I might do some valves just for ***** and giggles, but I don't plan on running this same setup next season, so I think I might just keep the stock pistons for now. Thanks again fellas!

 

If you are unsure of where you want to go with this setup, you should keep the pistons you have now. That way you won't be buying stuff twice.

Personally, I would save my money for head work.

 

Very good point about dynamic compression rochester. You can make a 11.:1 compression engine breathe like a 12:1 with proper cam choice, timing, and fuel delivery. And you avoid the detonation and possible piston/valve contact.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LsVtec92Hatch &raquo;</TD></TR><TR><TD CLASS="quote"> You can make a 11.:1 compression engine breathe like a 12:1 with proper cam choice</TD></TR></TABLE>

Would the m22's do that for me? What determines if a camshaft will make more compression?

 

Cams with higher duration lower dynamic compression. Its because the intake valve closes sometime after BDC. Since there can be no compression until the intake valve is closed, more duration will reduce compression.

 

That makes sense..so I guess a 288 duration camshaft will lower it then huh??