Originally Posted by dannichols1474 (Post 12287279)

Thank you scarceller for the tip above and also about the tuning books by Banish. You gave me the book recommendation on this thread about a year ago, so I already have "Engine Management Advanced Tuning" on my bookshelf and I will be referring to it shortly...

Today, I finally got the car out on the road for a short, 10 mile test drive. The engine definitely needs tuning - I can tell it wants more fuel and more timing. The character of this engine is definitely different from the previous engine, but I am thankful and relieved for it just to be running. Now, I change the oil, stare at the AFR and timing tables and make changes so I can be ready for the next tuning / test drive....

Originally Posted by dannichols1474 (Post 12287387)

Hi Sal (scarceller),

I just sent you a PM with my email.

When I initially converted from CIS to ITB EFI last year, I was running speed density with MAP signal for load sensing and it was working pretty well especially after I got the car dyno tuned and then did additional tweaking to the VE table with auto tune for the conditions the dyno tuner didn't cover.

During the initial engine start up / camshaft break-in, I noticed the MAP signal was in the range of 85-100 kPa between 1500-2000 rpm (and 73 kPa at 1000 rpm idle). So given the apparent weak vacuum signal from the new engine, I converted my tune from speed density to alpha-n so I am now using the TPS signal for load sensing.

Regarding a plenum on top of the ITB's: I know direct air flow mass measurement with a MAF is most accurate, but I'm going after a retro hot rod look and the plenum would spoil the look for me, so no plenum. :)

Originally Posted by mb911 (Post 12287024)

So just one point to circle back on this as I specialized in flat six exhaust for the last 25 years. The reason for poor vacuum signal was/is the header size. Back when Richard Parr owned PMO he called me and asked that I stop selling 1.625 headers to folks with engines smaller than 3.0 and it wasn’t once but multiple times. The PMOs had such a poor vacuum signal with larger primaries the cars ran terrible down low and would idle terribly.


Otherwise carry on looks like you’re doing a nice job.

Originally Posted by dannichols1474 (Post 12289863)

I finally got it thru my thick skull that I need to adopt at least some of what scarceller has been recommending for the control of timing around the idle set point. So, I broke the 1000 rpm column into two columns: 800 rpm and 1300 rpm - both columns have the same timing set points so when the engine is idling at 950-1000 rpm the timing stays rock solid at 14 degrees.
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I also came to the same conclusion with the new engine as I did last year with the CSI to ITB EFI conversion: stop beating my head against the damn wall! So I got in contact with Gary Bains at Bains Tuning and put down a deposit to get on his tuning schedule for the first week of August. I told Gary what I have going on and that I need a tuning job just up to the break-in rpm limit of 5000 rpm.

From experience, I know he will get the tune dialed in and then I will only need to polish the tune with the auto tune program for the driving conditions he doesn't cover in a 2 hour dyno tuning session. To me, it's money well spent.

Then after I complete the break-in period, I will make another dyno appt and let Gary wring out the engine to 7300 rpm.

Like Clint Eastwood in Dirty Harry said: "A man's got to know his limitations..." and I know tuning EFI is one of mine.

Originally Posted by dannichols1474 (Post 12289968)

rwest,

Check out Banish's book, specifically Chp 7 Ignition. At no load / light load the throttle valve(s) is(are) mostly closed so the cylinders are only partially filling with fresh air / fuel charge that is being diluted with exhaust gas which decreases the air / fuel burn rate. The slower burn rate requires more timing advance to ensure peak cylinder pressure occurs just after top dead center.

For my car, the OEM timing spec of 35 +/- 3 degrees at 6000 rpm is with vacuum disconnected. The 47 degrees of advance in the Ignition table represents 37 degrees of advance to account for peak engine speed plus 10 degrees of additional advance to take into account dilution effects of light load under cruise conditions. As load increases with increasing % TPS, the dilution effects go away, the burn rate increases so the additional 10 degrees of timing advance is not required and total timing goes back to just the amount needed relative to engine speed.