The Tuning Talk Thread - Forced Induction EFI & JZ Tuning.

[JZA70 R]

ok so does anyone know some pro's and con's to having a large portion of your off boost fuel map set to command high air fuel ratio's? (leaner than stoich) (15.0 - 17.0) ?

Most people have those kind of AFR's commanded for cruise only, where as im experimenting with a wider area for eg idle and high rpm / high vacuum...

In theory theres no chance of burning anything out because theres no load on the motor, ive read that once past stoich, going leaner the flame just gets cooler. So as long as the engine runs smooth I should be ok. I hope. haha

[1JZ-Rolla]

What are you aiming to do, win an economy run?

[JZA70 R]

im just experimenting mate. having a play and trying to learn. but economy is always nice. im even thinking of the smaller things here like sparkplug life. (good when running coppers)

[JustCallMeOrlando]

I had mine running quite lean on cruise. The biggest problem with running them leaner is the production of some nasty gasses. This is only really possible if a wideband O2 sensor is running the show. I set the Adaptronic up like this.

[thechuckster]

problems could be:
-increased potential for detonation at higher cruise rpms?
-you'll have to rethink timing strategies to cope with the higher AFRs?
-acceleration strategies... how much timing do you dial in if you're unsure of the response time to increased fuel supply (e.g. for when you attempt to overtake)?
-knock sensing - does your ecu (hardware and firmware) use it?


on the plus side ... with a decent ECU and wideband O2, you should be able to go closed loop for much of the map (e.g. right into low boost territory) and log it for further analysis. If you can combine that logging with 3D accelerometer data, then you'll get some basic data on power output for use in improving timing strategies

[gixer]

I have used Autronic for years, also calmaker/haltec/microtech...what ever
using engine/chassis dyno, both eddy current types
Autronic wideband, exhaust gas temp probes, knock sensor, tuning to MTBT
Tuning from blank maps, unless calmaker
Really no secrets, but locking ecu is good at stopping people from getting in and having a fuck around.
Tuning timing I use MTBT with the exhaust temp probes to check exhaust temp after finding optimal, use knock sensors, but generally MTBT don't get anywhere near detonation.

[Mazman]

The other week, i have learned that timing can drift as the revs rise!
I didnt know this until i was asked what values i had in my haltech ecu for timing drift ( on my ecu its called advanced trigger angle ).
So as you rev, your timing starts dropping off, and was told can be anywhere even to 10deg retarding!

I would like to know more about this and how one can fix/check this ( i was told hold timing light and watch while car under load and rev'd ).
Any other ecu's have this feature? and what value's do you have?

[JZA70 R]

You could ask your tuner if he can explain its function better, and or if he has tuned the car with it turned on. Im not sure what the purpose of it would be if the haltech uses a standard timing map.

If you have your laptop hooked up you can monitor live timing via that, and do some logs to see what your timing is doing. You can see if ATA is effecting your timing by comparing logged timing to whats set in your timing map...

[thechuckster]

timing drift? huh?

the trigger angle is the difference between TDC and when (during the crank rotation) the trigger sensor sends a signal - this should not change - timing for spark advance and injector firing depends on that trigger occurring at a consistent point in crank-shaft rotation time regardless of rpm.

As for changing the timing over the rev range - well, isn't that why you have a spark map (or maps) that change ignition timing depending on load and rpm?

[Mazman]

I was saying the same thing when i heard about this... uhhh?

But here are a few quotes i got from people telling me about it:

Have someone hold a timing light on your crank pulley during a run(lock your timing at 14 degrees). Make sure you are not getting timing creep(or retard). Let me know what you find.

After viewing the ignition setup there are a couple things that don't seem correct and also they did not set up the sensors to compensate for timing drift/retard or 'Pickup Delay Compensation' in AEM terms. . The way it's set up presently it will have timing retard as rpm increases. Still waiting to hear from him.

Presently after looking at your map the timing should be retarding as rpm increases because there's no compensation for the trigger delay. On your ignition setup it was not done.

they only checked the timing at idle and did not increase the rpm's to verify for timing drift.

Again, make sure there is no timing creep

Again, this is nothing to do with the ignition map that you input the numbers, thats all done, but there is a advance setup in the ignition software where you add separate values on top of the normal ignition mapping youve done, wich as ive learned is for situations such as timing drift/retard... im new to this and thats why i was asking, as ive never heard of this before, but sure enough i checked my software and there is that option in it, wich is not enabled on mine.
I have look at others maps and they have it enabled with some values added to it.

My normal ignition goes from high 30's coming down to about 15deg at max torque ( ~5000rpm) then i have it going up to about 18deg at max revs.


Some of these guys are haltech tuners in the USA.

[thechuckster]

if the trigger angle is changing as revs change, then there is an issue with the trigger wheel or sensor.

If a VR sensor has been wired up backwards, then about 1/4 into the rev range, the zero-crossing point tends to shift backwards. An optical sensor is always based on the leading edge of the trigger wheel, likewise a Hall-Effect sensor will trigger as the magnet passes over the top of the sensor.

The only way it might change is if it's a dizzi-based pickup and the mechanical/vacuum advance has been foolishly left in place, or they're using the outer section of a harmonic balancer as the trigger wheel and the fluid or rubber connection between the inner/outer parts is failing and allowing slippage.

Using the ECU to try and fudge over poor trigger data seems stupid and lazy.

[The Real Roadrunner]

It does happen but normally only on an engine which runs the CAS off one of the cams, it shouldn't affect a JZ series engine unless the ECU relies on the cam sensor as its home signal.

4A's, 3S's and 7M's do suffer from this problem.

[Mazman]

the engine i and the others that gave me the comments are talking about IS the jz engine, 2jzgte to be precise, and yes relying on the cam sensor for its home signal.

[The Real Roadrunner]

It should be relying on the crank sensor for the home signal and the cam sensor should be used purely as a sync signal (ie tdc no1)

Why would it rely on a signal that only happens every 720* rather than the one that happens every 30* or 10* for a vvti engine? seems weird but then again i have my own issues with haltech aswell, they do serve as a handy wheelchock though.

If its reading from the crank reliably the only reason why it could possibly retard itself is the ECU not being up to the task or the rate of change value in the ecu is incorrect. try it with a decent ecu like a PFC, Autronic or similar and i can tell you for a fact it wont happen.

cheers
linden

[thechuckster]

if the cam/sync signal varies by as much 15 degrees as Mazman's quote suggest, then you'd have to be really concerned about how much stretch/slop is in the timing belt and whether the tensioner is correctly placed.

fwiw: some ECU's (the early generation MSEFI's included) have issues with calculating or predicting rpms at low rpms (e.g. during cranking and with low-count trigger wheels) and ECUs using simpler crack rotation prediction algorithms are prone to excessive changes in rpm calculation during acceleration periods or from poor/dropped trigger signals.