I was wondering if anyone had thoughts on what would be a safe compression ratio bump for an untuned B18C1. Obviously I know with a tune I could run a much higher compression ratio, but money is a factor. I'm also aware that there will be minimal gains until some different cams are installed.

 

I ran 11.5:1 on my old gsr and it ran ok on the stock ecu and passed california smog too.

 

I wonder if 93 octane would work with a 11.5 :1 ratio

 

Depends on the timing. In theory it should and for liquid cooled many say 12:1 is the safe limit for 93 octane...

 

How would you be achieving this compression bump?

 

you can run high compression with low octane fuel... its going to suck, but if you cant tune it forget it.. generally you can just pull many degrees of timing to compensate. Although this would be kinda silly to do. Up the compression and lower the fuel quality your back to square one.

 

Need to fix the Cylinder walls in a GSR and it's going to be enough to have to go with new pistons. I was thinking about upping the compression with the pistons, since I will need over sized anyways. I'm considering bumping it up to 11:1, and down the road when I have a little more cash throwing some cams in there to help squeak a little more out of it.

Do you think that adjustable cam gears would be necessary with that small of a increase, or would adjusting the distributor be enough to accommodate the change?

 

Not on a stock computer with stock cams.

 

My last question never got answered...so bump

likwidchz, it is true I would be kind of going backwards, but it would be prep for gains down the road. I also believe that 93 octane would still work with only 11:1.

 

If you go to 11.0:1 on a stock ecu (p72). You should be ok to drive the car around.
I wouldn't go beating on the car until you at least get a chipped ecu with a basemap.

 

87 octane will run on 11.0:1 compression, you just have to pull a load of ignition timing... why would want to do this is beyond me, but the option is on the table

93 octane should work fine I would find someone with a similar setup and see what there total ignition timing values are at wide open throttle and compare it to yours once you are done tuning, higher compression will have higher ignition advance values My h22 is 10.4:1 and it does around 31 degrees, I had heard that the type S 11:1 h22 is around 38 degrees advance.. I can imagine ignition advance has a pretty sharp increase as compression increases.

--Aaron

as for the cam gear question I think getting them wouldn't be a bad thing, however the NEED for them... I do not know.. I think you only NEED cam gears if you tend to deck the block/head and change the clearances. However you can get some hp by retarding the intake and advancing the exhaust valve I think this widens the torque cruve, on an sohc engine with a single cam gear you shift the peak torqe around.... atleast thats my understanding.. feel free to school me if I'm incorrect.

 

Most B series seem to like an advanced intake cam and retarded exhaust cam, at least my setup as well as a few buddies have performed best with those settings. Depends on each motor, supporting mods, and a whole list of other stuff. I was told my cams "should" be put at +2 intake and +1 exhaust.... showed minimal gains so backed off the exhaust to -1* and we had a LONG linear power band. Like I said every motor is different and cam manufacturers give you a round about number...but fine tuning will be needed.

 

I have ran usdm itr 81mm pistons in my b18c1 with for over 20k miles untuned on a gsr ecu with full boltons with WOT afrs in the 14s lol got awesome gas mileage. 5k miles **** tune and 5+ k miles on a pro tune. I would not run cams with out getting them tuned. IMO. Made 170 and 121tq on a hot day.