280z L28 ignition timing.

[Andre]

Hey all,

What is the base ignition timing on the L28 engine just want to check mine over since all the Hastle with the alternator mess up by the previous owner I think its worth me checking this over too as the engine sounds and feels a little rough .
Seems to judder and feel rough in lowish speeds in third and fourth and lumpy in places so I'm thinking the car is firering a little wrong.

I've looked up on the internet but not coming across any solid answers so hopefully you guys can help out yet again.

 

[AliK]

I'm far from an expert, but my 260z is set to 10 degrees BTDC and I've read people putting L28s at 12 to 15 as well. That was on SA / Aus forums so it may be to do with their fuel grade etc but what I've read says 10 degrees is a safe starting point.

My 260 runs lovely at 10 degrees.



Ali K

 

[Andre]

Thanks Ali K it's gotta be worth trying it around 12-15 just waiting for my mate with his timing gun to see what it's at.

 

[AliK]

Pleasure! Worth doing, and he ignition system on these cars is pretty simple. Mine was running seriously rough with little power to pull off with but ok once it was revving. Turns out it was set to 0 BTDC even after Fourways had "tuned" it for me. I was pretty unimpressed, but easy to fix with a timing light and a spanner. Before I corrected it only advance I was getting was the vacuum advance!!!

The other thing to consider is how much vacuum advance you get when the revs go up, so do the timing at idle, then raise the revs to say 3k rpm and look at the timing again, it'll be something like 30 degrees ish and if you have a decent timing gun it should allow you to set it at a lower starting point so that you can still use the scale on the pulley. Don't advance the timing at idle too much beyond 12-15 as when the revs go up and the vac advance comes in you'll be igniting the fuel far too early and may cause other issues like pre-ignition, which sounds like valve noise.

Finally the other two things that had the biggest effect on smoothing my engine were 1. an internally regulated alternator (my volt dial was always bouncing around so the spark was obviously at a different voltage each time it fired) and 2. balancing the carbs. The latter makes a huge difference. If you don't have an air flow meter, just take the air cleaner off and listen to the hiss from either carb, you'd be surprised how good your hearing can be and how easy it is to determine / set to within say 80%-90%; if one is breathing more than the other.

Good luck with it and keep us posted on your progress.



Ali K

 

[jonbills]

When your mate is there with his timing gun, you want it set at about 35 degrees "all in" (which is to say the peak it gets to, which will happen somewhere around 3000 rpm I expect).

 

[Andre]

Hmmm Interesting on the above comments , the car was running at 0 degrees from what we could make out so it's now set at 15 degrees , still not 100 % smooth but alot smoother than it was .
The vacum advanced hose and the one next to it were both split and leaking so that was one of the biggest issues but now it's got me thinking that I still may have a leak somewhere in the system .

The comment about the alternator gets me thinking a little as I've had to do the wire modification to run a internal regulated alternator over the external one and I know the needle has jumped a little on the battery gauge but testing everything with a volt meter has always read that everything is fine there.


Snow on the groun here so havnt been able to take the car out and try it on the open road.

 

[Andre]

Ali k what did you do with your alternator problem? Not saying I've got one anymore just curious if you just changed your alternator in the end of it was a dodgy wire maybe.

 

[morbias]

What fuelling setup do you have on your engine? Injection or carbs, and type of carbs has a bearing on what initial timing should be, and of course the type of distributor you have fitted is most important as there are several different models which have different advance curves.

If you have triple sidedrafts or an intake manifold where vacuum advance is only pulled by one cylinder then you may as well disconnect and plug the vacuum advance altogether.

 

[Andre]

It's a 280z so fuel injection .changing the spark plugs next just to see if its something as simple as them .

 

[AliK]

Andre,

I had an externally regulated alternator and at anything under 3k Rpm my volt meter danced between 14v and 10v. I wasn't sure if it was the Alt or the reg but I wanted the beefier alternator anyway so I just swapped it out for a new internally regulated 280zx one with a lazy man's plug that does the equivalent of your wiring mod.

Before swapping out the alt I put a 2Farad capacitor across the battery terminals and it smoothed the voltage + engine note so I was pretty sure a decent alt and internal regulator would do it.

With the new alt the volt gauge sits squarely on 14.7v at idle and anything over, it drops to about 13v with headlights on but stays solid. AND my head lights got brighter

Enjoy the snow! When you take the car out next you'll love the difference! But you'll find the exhaust a little quieter as the fuel will now be burning in the cyls as opposed to your exhaust pipe

Jonbills and Morbias are bang on with their advice!

And great question, what carbs are you running?



Ali K

 

[Andre]

I've done all the battery test from the alternator right through the fusable link wire and back to the battery, the beefier alternator is all ways gonna perform better that's why I went along with it over the external unit.

I'm running fuel injection and a panel filter in my air box so no carbs for me

 

[Mr.F]

Check that the vacuum advance can is still working and holding vac.
Spark plugs should be 1.1mm gap for electronic ignition. NGK preferred - others are known to cause problems.

 

[Andre]

Is the vac can really that important Mike? Was planning on tidying the engine bay up and removing that at some point and working around the hoses it is working for.

Ill gap the plugs belted fitting them .

 

[Mr.F]

The vacuum advance improves low rpm drivability. If you suffer from low rpm / off idle stumble it is alikely culprit.i'm talking about the device on the distributor, not any emissions devices you may have.

 

[Farmer42]

..................and of course the type of distributor you have fitted is most important as there are several different models which have different advance curves.

As Morbias has mentioned, depending on the type of distributor you have, you may also want to take a look at the points and condenser. These would also make an engine run rough and would also mess up the timing. Eventually it will die on you - probably in the middle of nowhere.

If you do have the mechanical points- based dizzy, you might want to think about changing to an electronic ignition system.

 

[racer]

I run 34 Deg total advance on the race car which is generally seen as the optimum.
No vacuum advance though so, you need to rev it to 4K when setting.
If your running a 2.8 in a Zed you probably don’t need it with the extra torque available imo.

 

[Andre]

Changed the plugs today , the ones removed were pretty damp and sooty so gapped the new ones as mike recomended and it's still the same .

Found a video on YouTube of what mine is actually doing too

http://m.youtube.com/watch?v=C5Eb2OcIRQc

Literally a double to what the video is doing , running that little lumpy and backfire in the manifold.

Any ideas?

 

[jonbills]

Have you fixed the vacuum advance hose yet? it'll not run right around idle without it.
if you have fixed it, I'd be looking at the mixture - lack of pick up and backfiring would indicate a lean mixture - so perhaps the MAF, perhaps an air leak after the MAF, perhaps a blocked fuel filter.
or something else

 

[Andre]

Sorted the split vacuum pipes from the advanced cannister to the side of the radiator,the car idles fine it's just the initial running of the car that's the issue and the backfire that is bugging me.
Gonna change all the vac hoses as there all hard and loot brittle now .

From what I've read the distrubuter is electronic on the 280z and looks in good order inside the cap along with the rotor arm .

Guess next things on the list are leads and fuel filter and then go from there.

 

[jonbills]

To check for an air leak, you could get some Easystart (or other volatile flammable spray) and spray it at the places where there might be an air leak - if the engine picks up, you've found the spot.
Alternatively, if it catches fire, it's nothing to do with me