ok im planning on bumping the compression on my 94 gsr with some usdm itr pistons w/ itr conn rods. assuming that the engine would be stock besides these 2 items, would it affect emissions? in other words, would it pass smog with the slightly higher compression? also would there be any clearance issues? i plan on doing some light head work as well but my ultimate goal is to have a lightly modified smog legal engine.

 

you will have a drastic rise in compression, and in turn, a much higher NOx output. however, if your catalytic convertor is working properly, that higher output shouldn't be allowed to make it to the tailpipe.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SecretAgent &raquo;</TD></TR><TR><TD CLASS="quote">you will have a drastic rise in compression</TD></TR></TABLE>

10.0:1 -&gt; 10.6:1 isnt drastic at all.

Unless the motor needs to be torn down anyways for some reason, this may not be worth your time/effort/$$

 

10.84:1 to be exact, there is no clearance issues or any negative effects on emissions.

personally I would go with PR3 pistons and bump it to 11.4:1

 

Actually, the motor would be running leaner with the higher compression if no other changes are done, hence the car should run cleaner.

Interesting side note, to attain ULEV ratings on the new Civic's (D17A), the air-fuel ratio during part-throttle is upwards of 17:1, vs stoich 14.8:1 on ITR ECU's.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by neo_ &raquo;</TD></TR><TR><TD CLASS="quote">Thats freaking lean!</TD></TR></TABLE>

holy crap..that is really lean...maybe that's how they get the ULEV..no damn fuel is getting out...

 

Yes, that is lean, but not really in a bad way. If you think about the "load" that the engine is under at light throttle, there is really no need for a lot of fuel when just barely on the gas. The pressures and heat generated are very managable for that lean of a burn.

When we were tuning our F4i (for FSAE) we did a baseline on the factory map, and under light loads, the factory tune would go as high as 21:1, and then head right to 12.5:1 - 13:1 under full load.

 

so would you say that a jspec itr motor would pass the sniffer portion of a smog test?

 

i know tuning is key with any mod, but lets say i raised compression to 11.8 and put the stock ecu in at the smog shop would i be able to pass? and will 11.8 be ok on 91 oct?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TypeRPaul &raquo;</TD></TR><TR><TD CLASS="quote">i know tuning is key with any mod, but lets say i raised compression to 11.8 and put the stock ecu in at the smog shop would i be able to pass? and will 11.8 be ok on 91 oct?</TD></TR></TABLE>

I think putting the stock ECU in which isn't tuned for your set-up would probably do more harm than good, as you would probably be running too rich/lean in some areas which could **** your smog test results. Not to mention, running 11.8:1 with performance mods on a stock ECU that isn't tuned to 11.8:1 would not be wise as I'm pretty sure you would get substantial detonantion.

I'm sure some of the vets in this forum can add to this...

 

Idle emissions you would probably pass

rolling test would kill you

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TypeRPaul &raquo;</TD></TR><TR><TD CLASS="quote">i know tuning is key with any mod, but lets say i raised compression to 11.8 and put the stock ecu in at the smog shop would i be able to pass? and will 11.8 be ok on 91 oct?</TD></TR></TABLE>

id like to know this as well. TypeRPaul, the setup i was planning on is almost exactly what you have on your sig.

 

I'm at 11.4:1 street & dyno-tuned and NOx is the only one that I actually passed. I failed the HC and CO...

 

ok i know this is pretty dead, sorry to bring it back. since usdm itr pistons raise comp. up just a bit from the gsr, it would just run slightly leaner if using a p72? remember im referring to p73 pistons in a stock (for now) gsr motor. so it shouldnt have any problems with smog?

 

why not just do some 13:1 pistons and call it a day

 

Do not run stock ecus with anything over 11:1 and 91 oct.

Problem is with the timing, especially pass VTEC with P72, it will kill your motor FAST. P72 under VTEC is OK with timing. P73 on the other hand is much beter for this scenario, and above VTEC is actually perfect on timing, but under VTEC is can be touch too much (depending on CR).

Fuel is important, but if you have different cams (than stock) do NOT take any chances you'll lean out and kill the motor. FPR tricks do not work with high CR and aftermarket cams, VAFC does not work either, so do not play with this too much. I have had a B18C1 with aftermarket cams where I needed to bump pressure all the way up and then at 5000 rpm had to lean -18 on VAFC and at 6200 + 22. You get an idea it simply does not work (not to mention what it is doing to your timing)...

Anyway, back to original question, I just had B18C1 with 10.8:1 comp and type R intake cam, pass polution on stock P72 with flying colors.

Nino

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92TypeR &raquo;</TD></TR><TR><TD CLASS="quote">Actually, the motor would be running leaner with the higher compression if no other changes are done, hence the car should run cleaner.

Interesting side note, to attain ULEV ratings on the new Civic's (D17A), the air-fuel ratio during part-throttle is upwards of 17:1, vs stoich 14.8:1 on ITR ECU's.</TD></TR></TABLE>

Is this due to the extra NOx production consuming oxygen and lowering the oxygen sensor reading?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">10.0:1 -&gt; 10.6:1 isnt drastic at all.

Unless the motor needs to be torn down anyways for some reason, this may not be worth your time/effort/$$</TD></TR></TABLE>

higher than 10.6:1.. gsr head is different.

edit: oops, someone already pointed that out...

 

guess my only option would be take off the head and put a couple thick head gaskets on to lower compression?