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I have compared the original ROMs from the S14-SR20DET (European Version, 75F10) and the S14a-SR20DET (Europe Version too, 82F08) and I am surprised that the IGN-Maps are different and some differences in the Fuel-Map too!

Does anyone knows why Nissan has changed the IGN-Maps so much?
The engine from the S14 and the S14a are the same (except some minor changes e.g. the boost sensor and the EGR from the S14).

Here you see the differences:

Off topic but was it only the Euro S14's (SR20DET's) that had EGR's?

BlueRB240 wrote:Off topic but was it only the Euro S14's (SR20DET's) that had EGR's?

I only know that the S14 in Europe has had the EGR and the facelifted S14a not.

Nissan seem to tweak their maps from time to time. Often they'll start off with quite good maps and as the model progresses they pull back timing and add fuel. I can only guess that they do this as a response to problems with vehicles detonating due to inferior fuels etc.

I live in Australia so often what we see here are less aggressive maps compared to JDM because it's quite hot here and we don't have the same octane levels in our fuels as they have available in Japan.

On S14/S15 the boost is programmable so you may find that boost levels are different, so the IGN/fuel maps will be adjusted for this. The JDM vs Australian S15's do this. The JDM version runs more boost.

PL

I have asked around a little bit and it seems that the difference will be issued by the EGR! The S14 with EGR has "sharper" timings in the lower area of the map bacause the exhaust gases that re-enters the engine allows this.

The funny thing is: I am driving the S14-Map (the lower area) on a S14a for years without problems (Horsham ECU-Upgrade Stage 1).
The S14a has no EGR. The EGR is replaced by 2 catalytic converters (compared to 1 on the S14).
On my S14a the 2 catalytic converters are replaced by 1 100 cell metal catalytic converter.

That makes sense. I've never checked where the EGR is active. I'm not surprised that it's not causing a problem as the factory timing tends to be very conservative anyway.

The S14 certainly runs better (read more agressive) ign maps than S14a. I just compared 69F00 to 82F08 and the early one has up to 6 degrees extra in the midrange/full load area!

This would probably be better for a standard car that's just had the boost increased a little (12 to 14psi) but the S14a maps would be better for 16psi+. Although by then you'd be getting serious with bigger turbo/AFM and injectors anyway - and a proper custom tune.

PL