Maddiedog's 170cc PCX

[gia]

Or this one from the PCX150 : 16450-KZY-701 ?

[sendler2112]

If your stock injector is not maxing out (inj duty cycle less than 90% at full load), you can keep using it. But, in theory, the engine capacity is 36% more now, so you need about 36% more fuel.
Your EFI system is now fighting to keep the same AFR, in other words ECU tells to injector to throw more fuel in the engine, and, the injector could me maxed out.

Actually, the injector doesn't have to max out for the added displacement to be running lean. The stock fuel computer only has a certain amount of global fuel trim that can be applied. And this is based solely on the feedback from the O2 sensor since there is no air mass sensor in this simple EFI system. It computes air mass only by inference from a map based on the Manifold Absolute Pressure, Intake Air Temp, And Throttle Position. Installing a big bore kit will undoubtedly take the mixture right off the map lean. Not because the injector is maxed out necessarily, but because the correction program is maxed out. Installing an injector with a 36% greater flow rate would put the mixture right back in the middle of the maps. Until you change the cam. Which changes the rpm at which certain amounts of air is flowing. The only way to correct this and really get the mixture dialed in at all rpm's is with a good wide band fuel mixture logger and a fuel mapper like the Bazzaz. Which would probably have enough range to correct the mixture even with the stock injector.

[gia]

It rides fine with the stock injector. The only problem i have is that the idle speed is to low. It stop the engine 7/10 when i turn off the gas trothle. I can't find where i can correct it to turn higher RPM on the idle speed.

[sendler2112]

It rides fine with the stock injector. The only problem i have is that the idle speed is to low. It stop the engine 7/10 when i turn off the gas trothle. I can't find where i can correct it to turn higher RPM on the idle speed.

That is because you are way off the map and it is now running very lean. The adaptation that is built in to the stock ecu barely has enough range to properly correct for an exhaust which makes about an 8% improvement in power on these bikes. It is not even close to making up for a 36% increase in displacement.

[gia]

It schould than be fine when i change the injector, or not?

[sendler2112]

It would only be correct again if the injector had exactly 38% percent higher flow calibration to match up with the increased displacement. Major engine mods like these require a wide band dyno session to really get the most out of them without causing new problems.

[maddiedog]

Wow, it's been awhile. My PCX is still going strong. It's definitely broken in now, but is no chainsaw like PCXDemon's. The kit is at around 3k miles now.

I need to add a tach and do some tuning, I think my variator is holding me back now. I'm unsure though. I really should drop in the cam, it will definitely make a difference and I already have it sitting in my garage, but I feel like if I do decide to drop in the cam, I really need to get some sort of fuel controller to make sure I don't run lean... Talk about opening a can of worms...

Anyways, I finally got around to finishing the two howtos that went with my build, so you can repeat what I've done (and maybe even do it better if you're willing to spend extra on the ficon, exhaust, and intake). Here is the finally completed how-to for the big bore kit, and here is the how-to for the upgraded gearing. I hope all of you on this subforum find them helpful.

[Pcxdemon]

Deff go for it Maddie, cam will pep it up quite nicely. You don't have a big tb so you will have absolutley no dramas running 170 with only bigger injector. I ran mine including 31mm tb and pod on top of it with only an injector and per my afr meter it was within acceptable specs.
No need to remove head for the job, get the piston/crank aligned to their markers,pull the water pump out, release the chain tensioner,undo the cam chain sprocket and pull it out while using piece of wire holding the chain down. Then pull the cam out and slide in takegawa one, with or without decomp ( I got no drama not using one), adjust the valve clearance and put back together in order..piece of cake!

[iceman]

maddiedog / Pcxdemon - you both amaze me - the mechanical things you two get involved with, so far ahead of what I could do - my limit is about oil, spark plug and air filter and so far I have not done any of those, but the time is fast approaching (about 4100 miles on the clock)

[relic]

Performance
hey mad dog I live next door to a Subaru rally racing team
these guys do anything to get performance out small displacement motors
just don't do too fast
cause it will hurt

[Valiant]

Deff go for it Maddie, cam will pep it up quite nicely. You don't have a big tb so you will have absolutley no dramas running 170 with only bigger injector. I ran mine including 31mm tb and pod on top of it with only an injector and per my afr meter it was within acceptable specs.
No need to remove head for the job, get the piston/crank aligned to their markers,pull the water pump out, release the chain tensioner,undo the cam chain sprocket and pull it out while using piece of wire holding the chain down. Then pull the cam out and slide in takegawa one, with or without decomp ( I got no drama not using one), adjust the valve clearance and put back together in order..piece of cake!

No drama, but isn't it sort of like trying to breathe through a straw?

Now I'm not sure if the TB on a 125 is any more narrow than a TB on a 150, but you have to figure a jump from 125 to 170 is pretty big.