Dear John,
To be able to tune your engine correctly, it is
imperative that 0 degree in your ignition table really corresponds with piston TDC. Make sure that is the case by all means, even if you have to mechanically determine that crank pulley notch is right.
I don't think there is anything wrong with your boost or dyno results . If half of engine was running with misaligned cam and ignition was 8 degrees lower than what you believe is used then your results are quite understandable.
Regarding ignition table, I believe that there are gentlemen here that have mapped their ignition on similar setup and they will probably chime in soon. (just remember that you have to tweak those curves at low revs as your engine can provide full boost at low revs which turbocharged engine cannot due to turbo being "detached" from crank)
Few words of advice: start with low advance and work your way upward on the dyno. You don't need as much advance with twin plugs as with single plug.
"Choppy" table with 36 degree (!) "real world" advance (where 0 degree is really 0 degree) sounds a bit high to me and might result in knock/shattered piston rings if "tested" on dyno on full boost. So start low & safe and work upwards. Further, you don't need much advance on idle. 5 degree or so will be fine.
Usually, you set your advance nice and low at idle RPM (for example 5 degree at 900 RPM) and then you hike it up just underneath the idle in order to "fight" against the engine trying to drop lower than so.
Personally, I would start by determining the max advance I feel safe running at full throttle, then map the full throttle run. After that, you can hunt for more efficiency by raising the advance on half-load cells and try to improve driveability and MPG.
So yes, I believe you have to zero the ignition map and start all over again as your old map worked against 8 deg. retard and (from what you said) doesn't quite make sense. But whatever you do, make sure 0 deg is 0 deg and that you start tuning with sensible amount of advance so you don't knock the engine in pieces the first pull you do. And yes, your AFR table might need rework as well as it was presumably done against misaligned engine/ignition.
Regards,
Goran
Quote:
Originally Posted by JohnJL
Goran,
Your remarks are insightful as always. the 456 cam was out by 0.5MM. the 123 was spot on.
We only have 2 hose clamps, on the intake to the IC. They are tight. The intercooler exhaust side to the intake manifold uses Mark Hargett's QDC. They are supposed to be good to 100 psi. We dont have a smoke machine handy to check.
You are also right that the TDC mark on the crank was wrong...8 degrees retarded.
The spark map I have now is all over the page. I am up for putting in time to develop it but would be very glad for some guidance on starting points...for guys running 10-15lbs boost, where are you setting idle timing, when do you start ramoing up timing, and where/what is your max advance?
My map now starts at about 12 degrees at idle and progresses to 22 degrees. However it has lots of funny points like 36 degrees at high rpm/low load. And 10 degrees at high rpm and 220 kpa.
A cut/past graphical image of someone's map would be very highly appreciated!
Thanks again Goran, Tim, Mike, Jonathan and everyone!
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