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Advanced Tuning Concepts

General Tuning Discussion

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So i have been out looking for a different Crank/Cam for my RB. I have tuned alot of RB's and SR's and they easy for me to setup except for when you want to do something custom work like changing to a different Cam/Crank setup which they do not come with info on how to set them up and say talk to your tuner. Well i am the tuner an i do not have the full knowledge on this topic. So how does one get very knowledgeable on this topic and with other sensors that maybe of a custom type?

I've had plenty of experience on all sorts of different triggering methods - particularly with respect to the RB engine.

The stock 360 deg optical sensor in the RB/SR is terrible, particularly if you modify the cams as this can result in some strange resonance in the sensor which causes a lot of triggering problems.

In the past we have made a replacement trigger disc that goes in the stock Nissan CAS and uses 24 reference or engine speed slots, and a single synchronisation slot. This gives better resolution to the ECU and works well in stock or mildly modified engines. For high rpm use or with very large cams though, this still won't give great results.

For the best results I recommend a crank trigger system with the engine rpm/engine speed signal coming from a dedicated crank wheel. There are more options here for wheels and sensors than I can mention. My personal favourite is a 24 tooth wheel with a hall sensor pickup. This gives a clean square wave input that will be easy for the ECU to read. On top of this you need an input from the cam to tell the ECU which cylinder is firing. This just needs to be a single input to the ECU.

I'm sure I've probably given you more questions than answers so let me know what else you need to know. It would be helpful to know what ECU you are using too.

Yes the trigger wheel replacements is all I have experience with but that's pretty much a plug in play setup but when you change the cam wheel and add a crank trigger you will need to modify this in the ecu. How do you calibrate this in a ecu. For example I have aem ecu but with the aem wheel you just pick the wheel an it does everything for you but if I wanted to use a different wheel with aem I would not know where to start to calibrating this in the ecu. How does one learn this secret tricks??

It's not really anything particularly secret. You're right that it is a little advanced and I know many people struggle with it. I can't give specifics about the AEM as right now we are only beginning our own learning with the Infinity ECU. In general though you will have two trigger inputs -A reference or engine speed sensor, and a synchronisation sensor. the key is to define to the ECU what type of sensor is connected (broadly this is going to be either a Hall or Reluctor/Magnetic sensor), and then to tell it what trigger pattern to expect.

Most ECUs will have a range of preconfigured trigger setups to suit common or popular engines. They will also usually give you the option to choose a custom trigger system and this is what you would need to use if you are modifying the factory trigger inputs. The example I gave might be referred to as multi tooth for example.

We do plan to produce an advanced triggering course but it will be a little way off.

yes that's about the extent of my knowledge of trigger systems. i would like to know in a course how to determine is a sensor falling edge/ rising edge, how to setup filtering from scratch, just in general how to get a one off trigger setup going without the reconfigured triggers (if a certain type of ecu doesn't have it as an option, you can just get to work on it manually) to me it wouldn't matter to much on what ecu its demonstrated on b/c i can just adapt with other software. Also in this course could you go over coil Dwell in depth? i understand the concept behind it but i want to master this kind of stuff which to me will set me apart from a average tuner and a great tuner. But that will be a great lesson at least for me.

what other advance courses can you think of besides Trigger points?

Well the course we are planning will deal in depth with pretty much everything you have just mentioned so i guess it will be ideal for you. As I said, it is a little way off though sorry.

As for dwell, this isn't usually something we as tuners characterise ourselves. It's a little like trying to develop your own deadtime data for a set of injectors. While yes, it is possible to do, it isn't something you will be doing regularly. Many ECU manufacturers have done the hard work for us and have dwell tables to suit many of the popular coils to make our lives easy.

One can find the dwell time by starting very low, then increasing it until the engine runs cleanly. A dwell time which is too high can damage coils.

Actually just varying the dwell as you describe isn't going to be 100% accurate Dynodom. If the dwell time is too short there won't be sufficient time for the coil to charge and hence you may end up with a misfire. If your engine isn't producing high cylinder pressures though, or you have much more spark energy than you actually need to achieve clean ignition of the fuel/air charge, it's still possible to under-dwell your coil using the technique you describe.

In most applications you will find that the engine will run cleanly over a wide range of dwell times. This means you can easily end up having the coil under charged or over charged without ever knowing (unless you actually damage the coil).

The correct way to test the dwell is with an oscilloscope. Check the article here: http://www.extraefi.co.uk/dwell.htm

Andre. thanks for sharing your info. When I said to increase dwell time until the engine runs cleanly, I was actually implying that if the charge time is too short, the spark energy might / will be insufficient, hence there might be misfires. If there are no misfires with under-dwell, then there should be no ill effects whatsoever, correct ?

Under dwelling the coils will never damage them, so in that respect no, there is no ill effect. Even though you may not be suffering a misfire, reduced spark energy may still negatively impact on the burn and hence affect your power and torque. It depends how far out of the ball park you are though. In general it isn't something to lose sleep over but it's important to understand what dwell time is and how it can effect the coil (by both under charging and over charging).

For most of the common coils fitted to Japanese engines that I'm familiar with, dwell values around 3 ms at 14 volts are pretty typical. That isn't a blanket rule of course but this is the sort of dwell time you are likely to see.

i know i had to turn my dwell down in order to get a stable timing through out the rev im some where around 1.2 ms. i also wonder if it could be my cams are very aggressive 290/280 10.8 lift. i have the okada coil packs which says 2 ms max but i can not get it to 2 ms are timing jumps like crazy .7- 1.2 ms is best i can do. i am on AEM V1 i am looking for new ecu but i cant find an ecu that is not almost the same. they not like they use to be where they were very different in options

Cams have nothing to do with fluctuating ignition timing. Reading your post sounds as if you could have the inductive crank sensor wired in with reversed polarity.

Furthermore, dwell time changes cannot change ignition timing, in fact this would be fatal, Dwell defines the time to "charge" coils. Once charged, they "wait" for the ECU to release the stored energy at a predefined point, your timing table. I know this is not a scientific description of what is happening but I hope that it is logic and simple to understand. Andre, please correct me if I am off course here.

i have the stock cam sensor setup with stock wheel in it. i had the AEM replacement wheel but for some reason i could not get it to work, it would not hold timing thru the revs and AEM could not figure it out either, so i bought another CAS and set it back to stock sensor and i had to take out dwell to get it to hold the timing all the way thru the revs.

I am not certain if I understand correctly. You describe a cam sensor, but for ignition timing, the crank sensor is the gouverning one. Cam sensors are used to synchronise the ignition / injection sequence and to feedback camshaft angle for variable cam adjustments in closed loop.

The RB engines use the Cam sensor for positioning. if you would want a crank angle you would have make one up are buy an aftermarket kit to do so. for the older nissans the cam/crank sensor is in the CAS.

Oops, I just lost face here and learned something. Apologies.

Regardless of that, I trust that what I have said about dwell versus timing drift still holds true.

Looking forward for Andre's reply.