For all of you that have CTR pistons in a B18C5...

I know the static CR is around 12.5:1 with CTR pistons in a B18C5. Have any of you found that this is too high for 93 octane gas?

Also, please let us know what cams you are running, where your base ignition timing is at, and what ECU/engine managment.

-kenji

 

It is? I've always been told it's 11.6:1

 

around 12:1 i have them and a mugen head gasket for around 12.5 i get no knocking at wot but never got my car partial throttle tuned so it did have a little at partial throttle. for tuning: stock ecu, vafc, fpr, stock injectors. also from what i understand, my car would knock less if i had larger cams(was using ctrs) because the dynamic cr would go down


[Modified by CWTypeR463, 2:35 PM 11/27/2002]

 

http://www.c-speedracing.com/howto/c.../compcalc.html

^ says 11.75:1 if all you do is replace P73-A0 (USDM B18C5) pistons with PCT (JDM B16B) pistons.

 

You know what is rather odd - that same compression calculator used to read 11.99:1 for the CTR pistons in an ITR. They must have changed something.

 

I have a customer running b18c5 block with 81.25mm CTR pistons, milled ITR head 30 thous and stock headgasket, ARP studs, Toda spec A cams. 93/94 octane with 15 base timing, one of my ECU programs (max 31 med load) and no ping.

Greg

 

But don't you have to change the piston to deck height to .010 instead of the usual .030? If you do that it comes out to almost 12.5:1.

 

I have the CTR pistons and Mugen gasket.

I use 100 octane. I never tried 93 sorry. I did notice knocking at 35deg BTDC, so I dialed it back to 25deg BTDC.

I run your harness and a custom program ECU. The base timing, for tuning, was dialed back to about 18, and the ECU does the rest.

 

I'm going to go with the same setup, CTR pistons and mugen head gasket. Do you get your gas from Chevron? There's only a few places around here that sell anything above 91 Octane, and most of that gas is leaded. There is one Chevron that sells 100 Octane Unleaded, but it's like 5 miles from my house.

 

I got my gas from the Sears Point Raceway. I think there is a Redwood oil in town here thay has it, but I dont know for sure.

Also I would try local (small) airports.

Leaded? I have no cat! (but I still have no use for using leaded) 100 Octane is plenty for me.

 

Is there a limiting factor on what cams you can use if you have CTR pistons in an ITR engine?

ie are there any cams that should be avaioded because of interference problems.

 

Why not go with the p73-00 (JDM ITR) pistons, 2 layer headgasket and have your deck evened out? It would put you at roughtly 11.4:1, which should be safe even on 91 octane.

 

Thats what i did!!

I assume kenjis trying to One Up me!! hehe Hes soo sneaky!!

eric

 

Junglist,

That is what I had intended to do. I just wanted to get some feedback on CTR pistons.

With all of the different engine management systems out now there are more options available when it comes to tuning. Also, with the number of 'bigger' cams available, a higher static CR would not be as big of a concern as it would back in the day.


rainmanEK,

I have a feeling that Project Phantom Sh*tbox will be taking out your white EK at the local autocrosses. Project Phantom Sh*tbox @ PCA events 0WnZ y0u!

-kenji


[Modified by kenji, 5:52 PM 11/27/2002]

 

well im still wondering what the cr is with over bore ctr pistons in a c5 with a mugen head gasket, does anyone know for sure? also i was using ctr cams on 93...im sure larger cams wouldve done wonders

 

what about running the CTR piston in B18c block with B16 head (poor man's itr) and JUN III cams???? will that be too much?

 

if the mugen gasket is worth .4 then its gonna be close to 13.0:1

and to that last guy, if you are using a b18c block and b18c crank, its still the same.
whether its c1 or 5 doesnt matter

 

Kenji...

I dont know if you know my Dyno after my car was tuned, but my timing was put back to 18 because it didnt make more power being so advanced.


Stock top end. 198/136 tq at the wheels.. tuned for 6k and up.

 

damn, no wonder it knocked at partial throttle

 

what kind of setup did you get that out of ??

 

CTR pistons, Mugen Head gasket, JDM 4-1 header, chipped P28 with custom program, 100 octane, resonated short exhaust.

 

I currently have ctr pistons with jun 3 cams. its been running for 4000 miles now without a problem on good ol california 91 octane.

 

"with proper tuning 93octane shouldnt be a problem" or so Ive been told.

 

Kenji,
When I did the calculation it came out to be 12.2 to 1 with a stock head gasket. I would de - bure the crowns of the pistons and clean up the combustion chambers on the head, ( Especially around the valves) With that compression on 93 you will be fine with 17 degs of base timming.
I ran the B20 with Endyn pistons , a welded combusion chamber( Like a GSR) and .010 off the head which put me around 12.8 to 1 and I was fine with 93 and that Youshi computer I had. My base was 16 degs. I made 154 Torque with ITR cams . Compression is good stuff, Not as good as boost, But good stuff.
You could just run 14 to 1 and buy race gas now your making the big bucks "surfing the net"....Ha ....

 

ask jgale about his ~14.7:1 Endyn RW B20 w/crower 402s- 94 octane, hondata tuned by payntech- no knock.