sr20det ignition map

hey guys,

I have had a few road tuning sessions and one track day session tuning my redtop sr20det. I am using Nistune to tune with at this point in time.

I have tuned the fuel and ignition safely to suit the the bigger t3t4 style turbo, 550cc injectors and z32afm. The car has the usual bolt ons: 3 inch exhaust,top mount tubular manifold, front mount intercooler, fuel pump. 95 octane fuel...

fuel is 11.4 AFR full WOT, I have included a picture of my ignition map which i need some advice and pointers on how to improve it.

I am only running 9psi at the moment but will be wanting to ramp it up to 16 - 18psi. What sort of values do people normally see with sr20det engines. I have read a few forums with people saying 10 degrees through midrange and increasing to above 14 degress after peak torque is reached. I have been using audio knock headphones, No knock seems to present at all to me with this igniton map.

also the last two columns on the map are for overshoot. car is only reaching 95 on the load scale.

Any help is much appreciated!

I'm always very reluctant to give specific recommendations on ignition timing for a certain engine. There are simply too many variables for me to be able to accurately guide you. For example with my own personal experience, I've tuned more 4G63 Mitsubishi engines than I care to remember, yet even for two 4G63s running essentially identical setups, it's still not always possible to run the same timing map with safety. I may have a starting map that I know to be a good place to start from but I always tune each engine individually on the dyno using knock detection equipment to ensure the timing is optimal.

Saying all of this, I'd say from my own experience that your timing map right now for 9 psi is very conservative. I would try slowly advancing the timing 1-2 degrees at a time and check your results. Obviously this is best done on the dyno so you can monitor torque. On pump gas however you are most likely going to find the engine is knock limited, particularly on 16-18 psi, hence the knock threshold will be your limiting factor for the timing map. Always make sure you keep a margin of a few degrees between your table values and the point where knock occurs.

Thanks Andre,

With sr20det engines are there any trends with there ignition timing values throughout the map? For example i have seen that sr20det maps seem to have a low spot in there maps where peak torque is and once that is reached timing can be advanced more towards red line. Is this something that happens in your experience?

Cheers Thomas

Yes, I would say any engine has the lowest number at highest torque / VE. The ignition numbers should have a similary shape as the volumetric efficienc map of the engine. You can also have a look a the torque curve. Were you have the bigges torque you usually also have the best VE and consequently the lowest ignition number. After that point you can slowly increase ignition timing. You will find that you are very knock limited on the Sr20det and 95octane fuel if you apply high load for some time. I would also monitor exhaust temperatures. In my experience especially the S14, and S15 heads strungels alot with too high EGT's. If you want to use the car for cirquit races I strongly recommend to use a higher octance fuel. E85 works fantastic on this engines and really solves EGT problems!

Besides as more load you have in the map, as more you have to retard the ignition timing. So you can rise and smooth your part throttle timing and a bit.

I've found the exact same as Adrian, as a lot of the SR's I tune are for drifting if I want to keep some of the higher ignition values in the high rev and high load areas I need to run it extremely rich to prevent det occurring once things start to get hot, because of the knock limited nature of pump fuel in this engine ignition tuning is tested on the dyno whilst getting a lot of heat in the engine to ensure it's safe for when it hits the track. This is using UK 98RON fuel

I'll just elaborate slightly on what Adrian mentioned. There are two general trends to the shape of an ignition map and they are consistent regardless of the engine type.

First, as rpm rises we will need to advance the timing as there is less time available for the combustion event to occur while still achieving peak cylinder pressure at the correct point in the cycle.

Secondly as airflow increases we see the timing retard. This is because with a lot of fuel and air tightly packed into the combustion chamber, the combustion occurs faster and hence we don't need as much advance.

So you sort of have two trends working together. This is why you will often see the timing start to climb at WOT before dipping slightly around peak torque (remember that torque = airflow), before climbing again at higher rpm.