I've done a whole lot of searches and could not find anything to do with JE 9:1 pistons and what compression ratio it yields. Is it as simple as it looks, being 9:1 or will it be higher on a B18c5.
The reason I ask is I want to know if I get pistons/rods is it worth getting a thicker head gasket?
Can anybody lend some knowledge on this?

Thanks

 

If you buy 9:1 compression pistons for the b18c5 with the stock headgasket it will yield 9:1 compression. dont waste your money on other headgaskets, stay with oem, they are good for up to 500whp. i assume you are going turbo, correct? stay with 9:1, thats the ideal c.r.

 

do you have the build sheet and part # for the pistons... if you do there are a few things you need... the installed deck to compression surface height and the dome volume...

Once you have that you can play with a compression calculator to see what different thickness head gaskets will do for you.

Compression calculator here

 

Thanks for the info guys.

Much appreciated.

 

If the pistons yeild 9:1 in a B18C1, you're looking at appx. 8.8:1 in a B18C5 with stock stroke and headgasket.

But if I were going turbo I'd run at least 10.0:1.

 

Can you explain why you would run such a high compression ratio?
Everything I have read has contradicted this theory in terms of durability and longevity of the B18c5.
Also, with a 9:1 compression ratio, you are able to run higher boost.

 

10.0:1 isn't high.

Lowering compression allows for higher boost to a point, but only at levels much higher than what is typically run on a street car.

Running higher compression improves off-boost throttle response and creates more exhaust pressure, which spools the turbocharger faster. If I were building a turbocharged street motor I would run 10.0~10.5:1 CR.

[e] As long as the engine is tuned correctly, running 10.0~10.5:1 compression with a turbocharger will not cause detonation.


[Modified by MK Ultra, 12:10 PM 1/24/2003]

 

What sort of boost numbers are you looking at for a street car?
I done alot of research and have noticed that between 6-10, depending on your setup, is a reasonable boost number for a stock block.

Does anybody else agree with his 10-10.5 CR theory? Not bashing, just curious.
If that is the case, then why would anybody ever change the head gasket or the pistons to lower CR?

 

Street car, looking at 8~12 lbs.

Lowering compression is a safeguard many have used to compensate for the imprecise tuning you get from piggy-back engine management add-ons that were common with earlier turbocharged Honda motors. Today there is no excuse for that. Hondata's capacity for boost allows for far more precise tuning to suit the needs of a mildly boosted street motor.

 

I do agree that Hondata does provide fantastic methods for tuning a boosted car.
If you were to buy aftermarket pistons for your setup MK Ultra what CR would you get, assuming it would be going on a B18C5? Would a 9.5:1 be better....higher?

From what I've read, the Type R pistons are the weakest component if you are boosting and are the first to go.

 

You're right about the stock pistons being the weak link. A friend of mine just blew up his JRSC'd B18C1 on 9 lbs. with stock pistons. The ring lands broke.

9.5:1 would be slightly better than 9.0:1, but like I said, I'd most likely run about 10 lbs. of boost (conservative) and between 10.0:1 and 10.5:1 compression forged pistons (CR dependant upon what is available).

I am in a growing minority, but I am not the only one who believes in that approach. With the exception of the weak factory pistons, the key to having a long-lasting, well-running turbocharged motor is tuning (regardless of CR). IMO, lowering compression to 9.0:1 is not the way to go. However, it is your motor, and you should do what you feel most comfortable doing.

 

Thanks buddy,
Awesome info!

 

Honestly, 9:1 will be allt he more safer. Boost and high compression isnt the absolute best thing for a daily driven car. There are a handful of guys on the board that do run 10:1 compression, it allows for better response off-boost of course and will provide smoother torque values as well as a little bit more power. But honestly, you can compensate for this by playing with your timing with lower compression. Just know that high compression will allow less of a safe range when you are tuning your motor. HC is more susceptible to detonation, you can combat this with a higher octane gasoline and just hope you never get a bad tank of gas... if so youll most likely melt a piston. It's honestly up to you, you should be safe with 10:1 but youll be safer with 9:1, its your call. Turbo engines are high maintanance, i know from personal experience and i would do any little thing you can do to prolong the life of your motor.


[Modified by GudeH23a, 3:29 PM 1/24/2003]

 

dude that lower compression stuff is just jibba jabba ,.
i dont wanna hear no more dis jibba jabba '
put it this way . . . please these numbers are just theoretical to make a point
let say you haev an r stock comression pushing 8psi or so ,youll prob be pretty damn clsoe to 300 whp
now you lower the compression to 9:1 on that same boost and your prob down to 230 or whatever.
what im saying is i rather have the higher comp and less boost and more power
then lower comp, more boost to et the same power

if i ever lower my compression id roll no less thna 10.1 also. but im thinking of getting 10.6:1 forged internals and kill everyone when the block is all sleeved and what not . . . .i wish more people had the ***** to try it rather thna me being one of the 1st. but fuggit , i love to prove jabba jaws that talk all theoretical bullshit wrong

sorry i was venting , but i hate this lower the compression to save your motor crap becuase no one has any real evidence that thats true just here say

 

That's a good point about the amount of power a lower vs. higher compression ratio will result in.
Does anybody on this board with a T-ITR have any dyno plots to show some evidence here?

 

if you are not going to boost more than 12psi, then 10:1 is fine.
if you want to make 400hp, 9:1 will make it a lot easier

 

How did you prove this wrong? You gave your opinion, your opinion doenst make something true without research and data. As SGT said, if you want to produce a large amount of power then the lower the compression the better. My research and data is the amount of power i put out as well as numerous other board members who have 9:1 compression and put out over 400whp in a daily driver while not suffering detonation issues. Why dont you do me a favor and make a post in the forced induction forum for us and see what kind of answers you get.


[Modified by GudeH23a, 5:09 PM 1/24/2003]