I'd like to add a few notes for the archives in this thread about my Chinese turbo setup now that I've gotten a wideband O2 meter again and 150 or so miles on the bike. I'll throw more pics and detail in the project thread or copy this; just think this may help being posted here in the boosted thread.
The tune that has been in the bike since it first saw boost was surprisingly close to what I was aiming for. Quick carb setup review:
- Boost compensation: Two 3/8" pitot tubes facing into the incoming air charge (one Teeing to #1/#2 carbs, the other to #3/#4)
- Atmospheric ports were drilled out to 1/8 (I think 1/8", again I'll confirm this in the project thread when I get to my notes). I was half way through doing this when I realized the breech with the fuel over flow ports; *may not be necessary*.
- Additional boost compensation: fuel over flow ports plumbed to the intake manifold
- Idle jets: up one from stock(35) to #40
- Clip position: 78Fs have fixed needles, I added two #10 washers(I think, they're tiny) under the needles to enrichen about one clip position
- Main Jets: 120
- Float height: 14.5mm (stock tolerance)
- Idle fuel screw: 1 1/4 turns out
With a warm motor the idling A/F is around 14:1-14.5:1, this is very close to stoich (14.7:1). May be able to get away with stock slow jets as it didn't really need the choke at all to stay running when started cold. Or a 1/4 in with the fuel screw?. With out boost compensation at idle (
shouldn't impact idle) and with stock #35 slow jets I was seeing ~16:1.
When at cruising speed (1/8-1/4 throttle) at in town speeds 25-35mph and up to low country highway speeds 50-60mph the A/R is sitting again around 14:1, which is good (bit on the rich side maybe).
As you kick it up to around 75-90 and maintain this speed the A/F drops to 11:1. I happened to have a 65mph four lane highway on my way to work and the A/F was pegged at 11:1 while doing aroun 75-85 (think speedo is off a bit, slightly faster than traffic). The speed and or wind resistance creates enough load that I was constantly at around 0.0-0.5 psi of boost; depending on the load to the motor. Easy to build boost quickly at this point. I think either the removal of some boost compensation and or removing the extra needle shim(s) would help to get my cruising (1/4 throttle) high speed A/R back up to 14.7:1.
Twisting the throttle to wide open gives a solid 11.8:1 A/R in any gear or speed. I think this is in the middle range of where things should be, the bike responds very well; no hickups, pops, bucks. Haven't done a plug chop to confirm what the plugs say. From other applications I figure (11.0-11.5:1 is rich/conservative, 11.5-12.0:1 is intermediate, 12.0-12.5 max power tune/getting close to opps too far), I realize this is a very subjective subject, many factors and motors details to consider when figuring this.
"Laggy" isn't the best word to describe the bike but rather the onset of boost. From a stop the bike is very quick on its feet, as if there isn't a turbo installed at all; and may even be quicker than it was stock (maybe less restriction than an air box?). The bike seems to be naturally aspirated with an afterburner. With a big bore kit, bullet proof motor, and 15-20psi I think this turbo could be a real terror.
When you lay into the throttle and get in the upper RPMs the bike starts to pull harder and harder.. to the point where the clutch starts to slip (around 7-8psi area).
To be expected I guess, Barnett clutch springs will be hit up next. However I think the season is almost gone and may be a winter project, 33-35F on the way to work and back two days in a row is making me dress like I'm snowmobiling.