Adam Ligon wrote:
Man you can't leave it like that. Put the long version here
You asked...
What a week. I don't think I've ever fussed this much over a damn car before, but I *think* it's all come together at the 11th hour.
Background:
Old Crane ignition has a rev limter problem, being stuck at 6500 rpm (too low). Broke down and ordered a new Crane ignition. None of the wiring is the same 6 years newer, so I had to re-wire a bunch of stuff. Car fired fine, revved (no load) Ok to 7000 rpm. Easy fix? Nope. On the road I couldn't get it over 3500 rpm, it would just stutter and buck and backfire. Checked a bunch of things (different coil, different distributer, etc), and only retarding the base ignition timing to about 0 degrees fixed the problem (but it still wasn't quite right).
That brings us to yesterday (posted from a different mailing list):
Good news?
After yet another fit of changing distributers and setting timing, the car was running acceptable yesterday at lunch time. Still had base timing at about zero, still could hear (but not feel) the 3500 rpm stumble.
I still wasn't satisfied with the performance of this new ignition relative to the old one, so I called Crane (should have done it sooner). By the way, for the most part, Crane technical support KICKS ASS. The tech was a bit gruff, but after hearing my "problems" he INSISTED that I had the magnetic trigger wires crossed, and switching them would solve all my problems. I explained that I'd tried switching them and the car wouldn't even run. He told me to try harder to make it run.
I figured I had to prove him wrong (or right) one way or another, so in the parking lot of the dyno shop, we switched the trigger wires and fussed with the dizzy until the car fired and ran. Set the base timing to 8 degrees and revved it in neutral. It pulled to 7000 rpm with nary a stumble. Sure enough, all this time, it was the trigger wires. What a kick in the butt! I ended up moving the distributer a tooth to make it run right, so this was no small change. At this point, without even a test drive, I pulled it onto the dyno rollers.
BAD NEWS.
First pull was miserable. I've never had a pull take so long (due to poor power). It came in at about 110 hp and 112 ft-lbs to the wheels. I was crushed.
BUT: Air fuel was WAY off. I was a linear 10:1 A-F across the board. I was already on my leanest main jet (140) so all I could do is change the air jet. I went as big as I had, increasing from a 190 to a 210. This fixed the upper RPM air fuel (bringing it to about 13-13.5:1), but it was still horrible down low. It also didn't make any big power gains, just smoothed out the curve a bit.
Next up, we looked for ways to get more air. I pulled off the "pretty" filter screens that I like so much (and look so cool). Next pass was "impressive." I went from 110 hp up to 128 hp, there were some torque gains as well, now up to 117 ft-lbs (still miserable for a 2.5 liter motor).
That was my best pull 128/117. HP is up slightly over the old engine, torque is down, and the area under the curve is horrible. The old engine made 100+ ft-lbs from 2000 rpm to 6000 rpm, this engine had a torque curve that followed the power curve, starting low, rising slowly to a peak at about 4500 rpm (not even breaking 100 ft-lbs until 3000-3500 rpm). Once up there it held pretty well.
I'm sure yall can imagine my disappointment.
Good news?
After Aaron did his dyno runs, we headed out. The first thing I noticed was how AWFUL the car was off the line. The dyno didn't lie, the car was GUTLESS. It would almost stall at 2000 rpm. This was NOT how it had run with the switched trigger wires! I'll run them backwards rather than have this horrible power. It was also backfiring out the intake every 1/8 mile or so (very frequently). We got back to my place and hooked up the timing light. Previously the timing would run lightnig fast up to about 35-40 degrees of advance (starting from zero), it hit this mark by 3500 rpm.
With a base timing of 8 degrees, the car was barely making 25-30 degrees total, and it wasn't getting there until nearly 4500 rpm (torque peak, go figure). I let Aarontest drive it, and he agreed, the car sucked. It *couldn't* launch, there wasn't any power to do it.
I decided we needed more timing....
I moved the base from 8 degrees to 12 degrees, and we drove it again. WOW, that's all I can say, 4 degrees of timing made a tremendous difference. It felt great, it was now easy to light up the tires. My butt dyno isn't lying, and neither is Aaron's. I won't guess how much power that 4 degrees of timing made, but it's significant. I have no idea if the *peak* nubers changed or not, but the area under the curve certainly did.
I finally settled on 15 degrees static, which makes for 40 degrees total advance, and there isn't a stumble in the power band.
So, with the big race weekend tomorrow and Sunday, the car actually is running right. I did waste $60 on a dyno session, but that's life (at least I've got A-F numbers).
I'll be ordering some new carb jets and trying again. The engine wants more air, and seems to have the cam to handle it, so I'm also going to get bigger main venturi's (39mm up from the current 34). In the next few weeks I'll go back to the dyno and try to get it tuned better (now that I know how critical the timing is).
That should end this week's episodes of "The Days of Scott's Life."
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Hopefully, next week's pulls with the new piggyback will show some nice gains over the intake/exhaust combo. I guess Toyota does it right from the factory, for I only gained 6 whp and 3.5 wheel torque over my stock pulls 
