getting the base line

[V8BUG]

What I have: 283 sbc bored 60 over, so a 292
305 heads, so about 9:1 cr
87' tpi with accel 26lbs/hr injectors (I know there big but thats what it came with) Small cap hei distributor

fixed the sensor problem by grounding them directly and not through the relay board.
With all of the sensors function properly, and properly calibrated I went over the wiring. The 5v goes to the hei when there is over 18 psi of oil pressure, so during cranking there is no poer to that lead on the hei.

I went out there this morning (38 F according to both CLT and MAT) and tried to get it running. It cranked hard but finally caught and started to run like mad. Boy it sounded good! Then I realized it was cranking at 2600 rpm! seemed a little fast, but I let it warm up figuring it would slow down when hotter. Around 160 F coolent the ideal would try to drop, but go right back to 2500+. Then I noticed the headers starting to glow red and I turned it off.

I let it cool down for a while and looked at the settings. I have been looking at the settings off someones 83 K5 blazer as a reference. Then I realized my spark advance table was way off, in fact it was a exact copy of my ve table. So I went to try and generate another spark table but it did the same thing. So I plugged in the values off the 83 K5 balzers spark tables.

With the new spark tables, the engine would crank and fire and run for about three seconds and die. So I did as the tuning said and started changing the warm up wizard cranking PW and the after start enrichment, but nothing seemed to help. I started with the K% values and now I am somewhere like 50% AS enrichment

I think both my ve and spark tables are probibly wrong, and most likely other things too.

Heres my msq so far, If someone would be nice enough to take a look and see what they think that would be great!

Any other advice would great!

Matt

[Bernard Fife]

Matt,

An idle that's too high is caused by:

- a vacuum leak (mostly likely), or
- the throttle stops needing to be backed off, or
- posssibly a FIdle valve that too open, and isn't closing - check that it actually goes on/off - to lower the idle speed when warm, and add a restiction in the vacuum line to lower the idle speed while warming up).

An idle the's 'rolling' is a matter of tuning and making the VE table 'flatter'. However, wait until you get the idle speed down to a reasonable level before starting the tuning.

Lance.

[V8BUG]

well the throttle was open, so I adjusted the screw back untill the throttle would close no further.
I need to get a fuel pressure guage tommarow because I really dont know what the pressure is at right now.

I have one other question though: When I put the distributor in I had the line on the crank tab at about 9 deg BTDC. Then I put the dist in and lined up the vr sensor things and locked it down. I set the trigger offset to 9 deg.
Is this right? Should the base timing be at 0 deg?

any help would be great

Matt

[Bernard Fife]

Matt,

9° should be fine. But to check it, use a timing light to verify that the advance in MegaTune equals the advance shown by the timing light.

Lance.

[V8BUG]

I go the engine to run through its warmup and it was idling around 1000rpm.

The next I was going to set the trigger offset with the trigger wizard. The base timing is set at 9 BTDC when I dropped the distributor in, and the light confrims this as it reads about 8-9 deg when idling. the trigger wizard displays a value of 16-17 in the big window.

When the plus botton is pushed the 9 in the small window goes down to zero and the larger number goes up and the idle also increases. The timing light moves slightly toward 10 on the tming tab.

When the minus botton is pushed the engine starts to stumble and dies.

What am I doing wrong? Should I give it more timing in the table? Should I just leave 9 offset and move on tuning?


Matt

[Bernard Fife]

Matt,

9 is what you think the trigger is, and 16/17 is what MegaSquirt/MegaTune thinks the timing is based on the trigger offset AND the spark timing table. So what value the table shows at idle doesn't necessarily correspond to the trigger offset.

Use the + and - buttons in the trigger wizard to get the big window to match what you see on the timing light. Until those agree, the timing is not calibrated.

Don'y be concerned about what you think the trigger offset should be, this process tells you what the trigger offset actually is.

There's lots more here:

http://www.megasquirt.info/megatune.htm#og

Lance.

[V8BUG]

First off I went back and rolled the engine to 10 deg BTDC and set the distributor there. I went back into MT and set the offset to 10. The engine was allready warmed up, but it fired up and idled around 1400rpm

The ign advance gauge showed low 20's, The timing light showed between 8-10 BTDC. even when I reved the engine the timing light hardly changed, no where near what the trigger wants, something around 20.

So I went and changed the offset to 0, it fired up and idled around 2500 with the ign advance of mid to high 20's. The timing light again was still around 8-10 BTDC.

Then I went and changed the trigger offset to 17, it fired up and idle around 1000 with a ign advance of 16-17, but the timing light was still around 8-10.

When I would change the offset the engine characteristics did change so I feel the wiring is correct. Could my timing light by screwed up? The timing light is quite old(non-inductance type) but it still seems to work. Is my timing table off? My timing table is identical to the 83 K5 blazer's under MSII sucsess stories. I just don't get whats wrong.

thanks
Matt

[keithmac]

Can you fill in a table full of 10`s for the spark table and re-check your settings with the light?. Does MS2 have a fixed angle like MS1, seemed the easiest way to check for me.

If you can lock the timing at 10dbtdc at 2k rpm this normally gives a better view of the timing marks than at idle (for me anyway..).