Dynamic timing

[RustyNissanPrairie]

Does anyone know where the timing marks are on a 2.5NA timing case for dynamic timing?

I've found the TDC mark on the crank pulley and timed it to the factory setting of 13degree BTDC against a raised casting on the timing case which looks like it could be the timing point but there are 2 tapped holes close by that could maybe carry a timing plate/tool?

It was preiously at 6.7 degrees and certainly isnt suffering from 'diesel knock' so its probably correct unless unless else knows different.

[errol209]

Does anyone know where the timing marks are on a 2.5NA timing case for dynamic timing?

I've found the TDC mark on the crank pulley and timed it to the factory setting of 13degree BTDC against a raised casting on the timing case which looks like it could be the timing point but there are 2 tapped holes close by that could maybe carry a timing plate/tool?

It was preiously at 6.7 degrees and certainly isnt suffering from 'diesel knock' so its probably correct unless unless else knows different.

How old is the engine? the WSM shows a cover on the flywheel housing with an EP mark and pointer, but on "early" 2.5NA engines only. Out of interest, and 'cos the WSM only talks about static, what are you timing it against (I've not come accross dynamic timing on a diesel before, I wanna learn!)

[RustyNissanPrairie]

How old is the engine? the WSM shows a cover on the flywheel housing with an EP mark and pointer, but on "early" 2.5NA engines only. Out of interest, and 'cos the WSM only talks about static, what are you timing it against (I've not come accross dynamic timing on a diesel before, I wanna learn!)

My NA is one of the later ones that dosnt have the pointer/cover. The later one has a M12 plug on the rear flywheel housing that you screw a locking pin into when the marks on the cam, & fuel pump pulleys line up (like you do when you change the timing belt), you then undo the fuel injection pump mountings and screw a locking pin into the injection pump side cover. Wiggle the fuel pump around until the locking pin fits into the locating slot inside and lock the pump up again. This is static timing.

Dynamic timing uses a Piezo sensor that clamps to one of the fuel lines between the pump and injector, this detects the minute swelling that takes place on the injection cycle for that fuel line and displays on the readout of my AVL/Dieseltune/Crypton DX875 the engines RPM. The DX875 also has a strobe light, you mark the TDC marking on the crank pulley with a white line, run the engine and aim the strobe light at the pulley. The strobe light has an advance/retard function and displays the Before Top Dead Centre (BTDC) readout (2.5NA's are 13BTDC) on the DX875 and the actual timing angle on the pulley.

The problem is that after further research that LR never made a timing pointer for this later 2.5NA engine, you can see the mounting points for it on the timing case-had they have made one.

If they did it would be a doddle to dynamically time the NA engine-IF you had the kit-which are about £500 for the Sykes Pickavant version-my AVL unit was £80 off Ebay.

Dynamically timing the engine is better than static timing as it accounts for any wear in the timing belt pulleys. Pulley wear=slightly retarded ignition.

A 2.5NA needs setting as accuratly as possble due to them only having 68nhp at the best of times.

[TheHarv]

When I did my 2.5NA recently I set the timing statically with the flywheel + IP pins and then advanced it by ear until it sounded "just a bit too clattery" when cold and "about right" when warmed up

I think the amount of advance you can get away with depends on what cetane fuel you're running - the factory static settings are probably chosen so it will run forever, anywhere in the world, on whatever gnats pee is available. It was also noticeable how before I fixed the h/g no amount of advance made it sound / run / pull any differerent so it's quite sensitive to compression too. So even if you manage to dynamically time it to the factory 13BTDC that may not give you the best performace.

[RustyNissanPrairie]

one problem though with tweaking the IP position is that a small movement in the pump=a big difference in the timing.I've ended up with too far advanced and 'knocking' to too far retarded when turning it back and too 'soft' an engine. Ironically the first small tweak i did gave amazing results-but I got carried away and tweaked it some more and over advanced it. I've never re-found that IP sweet spot since!

It would be easy to dynamically advance it a degree at a time if only LR had made a timing pointer like they do for most other engines!

Good to see that people are out there twiddling with their NA's still, I was under the impression everyone had ripped em out for Discovery 200's!

[errol209]

Ta for the explanation, all now ferpectly clear!

It would be easy to dynamically advance it a degree at a time if only LR had made a timing pointer like they do for most other engines!

Apart from the NA-derived TD ...

Couldn't you make one? You can find TDC with a dial test indicator or bit of stick, and you have a timing mark and mounting points? You'd only need to it once. Then you can let us know the dimensions!

[RustyNissanPrairie]

Cant do TDC with a 12j/NA/19J/TD as they're indirect injection-you cant poke anything on to the piston head