454 mag mpi timing
 

While I was tinkering around getting the boat ready for summer (maintenance, fixing some nicks, etc.)
I figured I would check the timing on both engines.

98 454 Mag Mpi new long blocks put in 12' and have 80 hours on them.
Dealer I bought from in Va did the swap.

Both run good, no real issues, it's wasn't built on Wednesday so it runs a lil slow. 65 light, temp in 70s, low humidity wiht just me.
Any load (62-63).

Port engine is at 4 degrees and S is at 8. I've read they are supposed to be at 8 BTDC so what power loss could I be seeing from the P that I am not realizing?? Still idles and runs fine.

Assuming both motors have the same ECM and .bin file the port motor would be 4 degrees behind where it 'should' be. The ECM likely has 8 deg base timing set. Ideally you'd want to see what each motor has set for the base timing in the ECM and then adjust each distributor to that value. To do this you need to set the ECM in base timing mode which removes it from timing control while the distributor is moved and adjusted. This is fairly simple as you either jumper two pins on the DLC or use a scanner tool to electronically do the same thing.

Bottom line is your port motor is likely lazier than the starboard when trailing 4 degrees.

[ATTACH=CONFIG]554241[/ATTACH]

I plan on jumping the pins tomorrow and resetting. Have been doing some researching but was curious how lazy or where the laziness comes in? Wot?

Well, I double checked the P motor and it was steady at 4 BTDC. So I put the paperclip (cut in half) into the A and B slots in that plug and sure as sh!t, that worked. When I cranked her up, she would die if I didn't give her a lil throttle.

Set at 10 degrees to give me a lil advance to see how she runs and moved the S motor from 8 to 10 BTDC also. Both purr like kittens, so I guess I will see how she runs next week end.

You've only done half the work. It is imperative you find out what is programmed in each ECM. You run the risk of running too much advance at higher rpms by setting base timing too high. Base timing is just that. The base physical timing each distributor is mechanically set to. The base timing in the ECM is merely a value programmed in that SHOULD match what you physically set. The ECM assumes what was mechanically set matches the value programmed.

If you have a base timing mechanically set to a value higher than what is programmed you run the risk of too much total advance.

They are both stock, so they "should" be at 8 BTDC? So my thinking is if the ecm is set at 8 and total at 32 (just example) then if I set base physical at 10, then it would really be 10 and 34 total? That was my understanding,, But with that said, I will look for a scan tool to check.

"Should" is the key word. Having base timing too high is not just about the total advance but also the advance everywhere else in the table. I've found midrange MAP regions to be finicky on advance (engine knock sensed) with much less than 32 or 34 degrees of total. For example around 60 kPa and 2600 rpm knock might be sensed with only 26 degrees of timing. If you had base timing set 2 degrees higher and total advance was 28 degrees you might be causing minor havoc in that lower rpm/MAP band but the motor might tolerate 38 degrees of timing at WOT.

Bottom line is its best to match base timing with the value programmed in the ECM. If you want to alter timing get into the MAP/RPM/ADV table and adjust it there.

Set them to 8* base timing. You won't see any gains at 10* anyway.
Not to mention, the knock sensor might just kick in and pull timing back anyway.

Exactly....

Well y'all are no fun.... I guess I will set back to 8 this weekend then! Thanks for input guys!! So I will get to see what gains, if any, I will get from bringing the P back to 8 from 4 BTDC.

I (we) weren't trying to rain on your parade but base timing is basically used for idle control and baseline ignition mapping for the spark table. Any change to base timing affects global timing and often not in ways you'd prefer. With both set to 8 degrees at least you'll have a solid baseline from which to work. If one motor is lazy there may be other issues (throttle rigging?).

Best of luck and let us know. Feedback on success OR failure is important.

This is what the computer is doing at idle to make it idle smooth. this is why the base timing is set in diagnostic mode. Granted this was 502 but 454 is prob doing the same thing.

https://www.youtube.com/watch?v=tgBYh_IFMyU

Yes, part of the spark stabilization built into the TB ignition. It tames down the idle fairly well, even with a healthy cam. That stabilization is removed to fixed tabular values around 1200 rpm (don't remember the exact rpm off hand).

my 1999 mefi 3 "enables" the stabil mode according to engine temp, which is set kind of low so basically it is active all the time. In my opinion factories set things fairly conservative. I bumped up the timing 4 degrees on a trial by just resetting the base timing and it felt noticeably better. Gained 2-3 mph with wot timing set at 34 vs 30 factory. so i reprogrammed the timing tables to get to the same spot at wot and around idle but the mid range i had to retard back to factory because factory was already quite high at around 37 degrees cruising.

However, i do run 91 premium.... always have and always will.... it's not worth a motor from detonation.

I think that's what a lot of people don't realize what the Merc timing tables look like. They tend to be conservative or at least reasonable at WOT / high MAP/ RPM (say greater than 3600 rpm). However, the midrange cruise advance numbers can be quite high. Decel advance is over 40 degrees. So if people start tweaking base timing they can inadvertently send the midrange timing through the roof and hurt the motor.