Ignition timing, Difference between loop and direct to coil

[Andy-p]

I have a c35 S1 rb25det manaul laurel, running an apexi fc and few small mods boost controller, fmic, cat back and air filter.

During the map time on the dyno, results where very low.  The tuner was expecting figures closer to the 290 range and instead it came around 236.  Since then compression, engine timing and many many other things have been checked and all came out correct. 

The only thing that is puzzling me is that the base timing is set to be 15 degrees.   This was done from the loop wire at the back of the car.  This shows at 15.  Then checking the white centre wire into the coil on no.1 still shows 15.  But through reading where many people have suggested the ht lead directly onto the sparkplug tactic for accuracy, there is then about a 5-7 degree difference in ignition timing???

It seems as though a lot of people get the same result either way, so people swear by each method.  but with this amount of deviation between the 2 it could be a cause of low power.  Compression is fine, standard AFM is almost maxed out, it does not lean out so fuel is there, compression is correct, 7 heat range iridium plugs, they are aftermarket coil packs from in japan...

 

Any help or information about why this occurs, or any other ideas would be brilliant as i've got a long way to go with this car but i need the base to be correct.

 

Thankyou 

[KiwiRS4T]

I think it is accepted that wire on coil is more accurate.

[Dose Pipe Sutututu]

If the car isn't taking timing and the base timing is correct try dropping your cat completely and running it on the dyno without it, ie dump pump to down pipe to atmosphere 

Could be a restrictive cat or cat back exhaust or both. 

Also just re reading are you running the stock dump and down pipe? 

(I'm assuming you're referring to wheel HP not kW) 

[Andy-p]

Yeah exhaust is standard except for back basically...was wondering about exhaust being an issue. 

Just unsure as to why there is such a difference between the two ignition timing readings. And if people are tuning from the direct to spark plug method then they could well be putting +5 advance on from the 'nissan approved' loop wire?. As the delay in the coil charge time must be in there calculations for ignition timing.  Has anyone else taken readings from the both methods? 

Car sounds and runs healthy with a decent amount of pull in the torque band But just missing the expected power

[Dose Pipe Sutututu]

Upgrade the dump/downpipe with a large bell mouth one and a high flow cat. 

You'll be less knock limited and you'll make more power. 

[KiwiRS4T]

6 hours ago, KiwiRS4T said:

I think it is accepted that wire on coil is more accurate.

or to be more specific wire between coil and plug.

[Andy-p]

Yeah but why is there such a difference between the two? Though the loop wire gives a constant reading. Hear some people the loop jusr flashes all over the place or something. I'm just getting 5 degree difference after the coilpack? 

[GTSBoy]

Good quality timing light is half the battle.

[Andy-p]

Yeah very good timing light reads the signals clearly and consistently! 

[Andy-p]

Or has anyone got a picture of a spec 1 loop wire/colours or wiring diagram? Because one wire in a loop at the back of the engine is pink with a black stripe? Chrz 

[KiwiRS4T]

6 hours ago, Andy-p said:

Or has anyone got a picture of a spec 1 loop wire/colours or wiring diagram? Because one wire in a loop at the back of the engine is pink with a black stripe? Chrz 

Don't worry about that measure between coil and plug.

[Andy-p]

But why? I can understand if they give the same values, but if they are different then surely it needs to the correct nissan way otherwise it will be incorrectly set by a few degrees? I get that people get all sorts of pulses though the loop wire, but mine reads accurately?. The extended loop wire I'm using my even be the wrong wire which is why I'm getting very different readings. Even if someone knows ecu pin numbers or something for that loop wire so I can confirm/find it? Chrz