[Colin Ryan]

This is such a dope build I want to do something crazy to the z this might be a good idea lol

 

[Kawasaki Brad]

this might be a good idea lol

Let's not get ahead of ourselves. I'm pretty sure this is a bad idea but we'll find out soon enough. Bad decisions make good stories right? Just waiting for things to defrost a bit around here. Could maybe see a vid as early as next week if the weather holds.

 

[Kawasaki Brad]

Just a quick update.
Good news = no damage or catastrophic failure.
Bad news = nothing exciting happened.

Went for a little test today and it was WAY rich. Instantly bottomed out my wideband O2 at 10.0:1 so in reality it was much lower than that. I incrementally added timing until I was +2deg ahead of stock, and concurrently took out -5 -10 -15 -20% fuel. Didn't need fancy electronics to tell it was still way off. Surprised I didn't foul a plug today.

Fuel/Nitrous jet ratios are always tricky but I knew this one was going to be some kinda special. Got it home, pulled the datalog, watched the vid's, and tomorrow we will be going with a .019 Nitrous and .009 fuel jet (previously .015 and .009 respectively). See what that gives us.

 

[Kawasaki Brad]

So in order to get around the 13.5:1 AFR I kept increasing the nitrous jet size since I'm already using the smallest fuel jet available. I ended up at 0.026 N and 0.009 F which is mathematically adding about 16hp at the crank (Yikes)!

It went surprisingly well and I increased the PWM (valve flutter) until it was taking the full hit. Then it completely lost power and started spewing oil from the breather. Originally I thought I burnt a hole in the piston but after disassembly it turns out it was cracked. Looking at the datalog the AFR was perfect all the way through. Not too hot, just too much power for the little guy (and maybe a bit too much timing, I thought I heard a bit of pinging).

New piston and hardware is ordered and I'm going to max the PWM ramp out at 75% but keep the same jetting. Probably be at -5deg (over stock) timing advance. Was at -3deg at the time of failure. Stupid me I was on 95 octane when I have a jug of race gas right beside it. So it will be at 112 octane leaded next time (no frickin way I can pre det that on a 9.6:1 compression ratio!).

I have LOTS of footage that I'm filtering this weekend so will FOR SURE have a vid on the youtube channel this week (I'll post it here too).

Now I know for sure that the stock engine can handle a minimum of +10hp with a proper wet shot of nos and a very minimal ramp (0.25 seconds).

PS: Has anyone found a forged piston for the stock bore yet? I seriously can't find one.

 

[Ls13ater]

I think I might still have a few stock piston at the shop one had 20miles on it when I swapped it for a guy

 

[Kawasaki Brad]

Well. I forgot something really really stupid and it took a friend of mine to point it out.

I didn't over gap the rings which explains the weird fracture. More heat = more expansion and the ring ends smack together. When that gap is gone the ring is forced tighter against the cylinder wall, which in turn quickly creates even more heat and more expansion.

Live and learn I guess. Glad I only forgot it here rather than on my ZX10.

 

[Kawasaki Brad]

 

[Kawasaki Brad]

Update on the rebuild.

Have a new piston, rings, wristpin, circlips in there.
Stock ring gap :
0.0059-0.0118 Top
0.0118-0.0177 Second
Current ring gap:
0.014 Top
0.022 Second
Checked the oil control rings (the two that sandwich the wafer portion) and they were 0.017 out of the package so I gapped those to 0.022 as well.

Other changes:
Straight Fury 108 (Leaded)
Cooler plug (went from the stock 6 to a 7)
Indexed plug to the peak of the dome
PWM valve flutter at 75% (37ms closed for 13ms @ 20hz). No ramp.
Retarding timing by 5 degrees

Will try and test it out this week.

 

[Kawasaki Brad]

Went down to a 0.021 Nitrous jet (from the 0.026). Tried it out on Sat this last weekend and it felt really strong. No pinging, plug looked perfect, but it would get to some very "crispy" high AFR readings right at the button push and then settle out. I didn't push it and waited until I got home to put in a bigger fuel jet.

In an effort to be safe rather than sorry I went from a 0.009 to a 0.012 fuel jet. Figured worst case scenario it would be really rich again and I could always go down to a 0.011 or a 0.010.

Well, today went out for a spin. Hit the gogo juice (peaked at 12.4:1 AFR and then hovered around 11.9/12.0). Sounded really weird and pingy. Let off and headed for home and it seemed to be running fine at cruising speed. Got to a stop sign, it stalled and wouldn't start at which point I noticed oil spewing out of the breather. Thankfully I've learned lessons about this and either stay close to home or bring the trailer. I was within a block of my house at the time.

I'm guessing there is either a hole in the piston, a cracked piston, or both. Dammit! Thought I was playing it safe. Don't understand what happened there since it was much more lean on Saturday with no issues. Wondering if I was on the cusp of failure and did the damage on Saturday with today being the proverbial last straw.

New pistons on order. In too deep and much too close to give up now. Nitrous is a temperamental mistress.
If only I could find a forged piston for the stock bore.

 

[Azlar49]

I applaud your persistence on this. Hopefully you will get it right soon.

 

[Kaw'ee]

Will this be another KawasakiBrad new product mod when you get it dialed in

 

[Kawasaki Brad]

Will this be another KawasakiBrad new product mod when you get it dialed in

Strongly doubt it. I'll share my settings and maps for anyone that is interested in doing their own. But this setup would probably retail for over 1k CAD and that's if you already have a fuel tuner. Doubt many would buy it.

Even in the big bike/car world people seem to go for the cheapest one they can find and then learn all the lessons the hard way (+1 guilty as charged 20 years ago). I think that's why nitrous has such a bad reputation for wrecking stuff. With experience and all the proper equipment it's still hard to get figured out. With a cheap "dry shot" it's impossible.

 

[Kawasaki Brad]

As discussed in the "Timing advance/retard terminology" thread it turns out that I was using some incorrect values for advance vs retard. I'm a little torqued about this at the moment but proves that it's worth some digging when evidence points the opposite direction of advice.

For anyone who is using Dynojet (PowerCommander) the software values for timing are:
-# in degrees spark happens later
+# in degrees spark happens earlier

This seems to be the majority but it is not universal throughout tuning software/hardware brands.

Picked up the new piston yesterday and we'll try this again. (probably next week since my "big bike" track has the season opener on Friday and the weather looks fanfrickintastic).

I'm not even going to change the jets or plug or anything else. I think my problem was 100% timing induced. This time I'll be using -5 degrees making the spark happen 5 degrees later than stock. Vs +5 degrees which made the spark happen 5 degrees sooner than stock and a full 10 degrees before what I was actually trying to accomplish.

Should probably have a couple pistons and head gaskets sitting on the shelf I think. Yeah they're weak, but at least they're cheap.