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Easier to be off than most people realize. We've seen plenty of people quote the "19 tooth between cams" and be off in relation to the crank or simply count differently from one person to another.
It seems so! Frankly I recall the job being easier than most people had feared... oh the irony. I'll take off the valve cover, rotate crank until first cam lobes point away from engine and match up to notch. And double check cam marks. If they still look right, I'll post them up just to do another gut check.
Here's to hoping I clearly see a tooth or two off. That would be great.
Easier to be off than most people realize. We've seen plenty of people quote the "19 tooth between cams" and be off in relation to the crank or simply count differently from one person to another.
Finally got around to checking my timing. Unfortunately uneventful. Crack pulley notch at tdc, zip tie in first cylinder to verify piston position. Cam lobes pointed out. Both cam gears line up everywhere. I REALLY wanted to be a tooth off somewhere... but no. All looks good.
Going to recheck base timing. When I set it first last time...I had to rev the car to get a stable timing reading on the pulley... and adjusted the trigger angle accordingly. Going to recheck it now that idle is smooth and stuff.
So tl;dr... mechanical timing is fine.
Tedz, so it CAN'T be a vacuum leak? That makes me feel better ... in that I won't have to add changing the intake manifold gasket into the mix.
Nope, vac leak raises idle rpm. Are you sure the ex cam marks are correct? It will fit on the dowel in the wrong position, Z up IIRC and result is ~40kpa idle vac while seemingly running fine elsewhere.
Honestly, it could be right, and it may be off. Pictures of these things are hard to be sure of due to perspective. The cam marks need to be centered on the ridge. You can get one a little CCW and the other a little CW, be 1 tooth off, but still have the marks be on the ridge slope.
The other thing to be sure of is that the crank pulley marks actually correlate to the notch in the crank cog. These pulleys are known to slip, and the old screwdriver in the spark plug hole trick is only good for probably +/- 10 degrees or so at TDC.
It is important that the proper tensioning sequence be followed, it is documented everywhere.
An extreme head shave can throw cam timing off. Recovery of proper timing requires adjustable cam gears.
If you check all of these boxes, we are probably barking up the wrong tree and need to start looking at a leak down.
Yeah I guess leak down would be the best next step. I thought that cam gear pic was pretty good looking straight on, and it does look centered on that ridge.
The crank pulley was replaced about 10k miles ago... rubber sheared off and the pulley fell off a couple of years ago. So that's not toooo old.
Quick question. I turn the crankshaft clockwise (spark plugs still in) and it obviously gets difficult during the compression strike. SHOULD you hear any noise akin to "air" as you work through the crank rotation? I mean, I know there should be the air release as you get into the exhaust phase. But prior to that?
Alright. Did a few things. I'm working through the cold loop crap - realized I had a few more cells that needed adjusting on the ignition portion, and matched them up with the others at 10degrees. This stabilized the idle and removed most of the oscillation. In lieu of that, I also went back to open loop idle to take the PID out of the equation while I dial things in. Keeping PWM idle duty, fuel, spark, in control and constant and seeing the resultant effects.
Moving those three things around, I was able to get down to idling at ~34kPa - while idling around 850rpm. Spark ended at 18 degrees and AFRs were down to 13.2. If spark was reduced, or AFR's increased (I'm running sequential), the map would go up. If I increased the rpms to ~900-1000rpm, it would drop down below 32.
Overall - starting at ~40kPa...as I increased timing from 10 degrees --> 18, the MAP progressively dropped down to ~36/37.
As I added fuel and dropped the AFRs from 14.5--> 13.2, the MAP dropped further from 36/37 to ~34.
All this considered...is there any reason for me to keep the settings here? Or is it just to have "a nice idle?"
Edit: Actually now I want to get a second timing light just to verify the one I have currently is functioning properly (harbor freight).
Last edited by wherestheboost; 01-31-2019 at 02:06 AM.
34 is much more reasonable, and the other numbers are in the ballpark. The thing about idle is that it actually takes a lot of tuning to get right, a huge percentage of the community doesn't address it properly, and they band aid it with stuff so it doesn't bother them.
Look at your logs... you spend more time at idle, or entering/leaving idle than you do anywhere else. Also think about driving, when do you usually actually notice the quality of a tune? At idle. Idle tuning impacts start-up, it determines the performance on tip in, does the car choke or bog with the headlights, or the fans, or the heater, is it stable across CLT, MAT, ... I could go on.
Get it right in steady-state, because when you move on to more advanced features it will screw you if it isn't.
Holy crap. I've only been having the car sitting during all this time. Finally took it out for a drive to give the battery some juice. What...a...difference. Takeoff, transition to idling, etc etc. Fantastic. I still have things to iron out. And I'm currently back in open loop until I've got all the tables sorted out. It's currently idling higher than I want - just need to adjust that valve down a smidge. It's feels fantastic idling at 1000rpm, ha! (obviously only for now).
I have to question your closed loop initial values if you are running an nb with the nb style iacv. I was under the impression that NB iacv had it's value range from somewhere around 15 to 25 and the na style had its value from 30 to 40 for initial values. Maybe I am wrong but that caught me by surprise.
01-24-2019, 07:32 AM
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. I'm open loop for now anyways. About 27 when fully warm to have it sit around 850rpm.
