[jasmine]

Hi All,

I'm just wondering if anyone has experimented with finding the best timing setting for a stock-standard J20A Grand Vitara? I'm hoping to maximize the Low-RPM power if that's even possible.

Can it be adjusted with only basic hand tools? I've noticed that the Camshaft Position Sensor on my vehicle could be easily swiveled by loosening the torx bolt.

Also, which way does the Camshaft Position Sensor spin - would it be the same direction as the bottom pulley on the front of the engine?

Thanks heaps in advance for your advice!!!

[Rhinoman]

Drop Fordem a PM, I know that he runs advanced timing on his.

[murcod]

Rhinoman wrote:

Drop Fordem a PM, I know that he runs advanced timing on his.

http://www.suzuki-forums.com/1g-1999-20 ... iming.html

fordem wrote:

The old folk here have a saying that goes like this - don't trouble trouble - in a nutshell, don't go making trouble for yourself.

From the questions you're asking it's clear that you lack the experience & understanding required, and probably the tools & equipment needed to correctly reset the timing at the end of the exercise - you're unlikely to be able to improve on the factory settings, so just leave it.

The ignition timing on most EFI engines (J20 included) is controlled by the ECU, and adjusted as necessary based on operating conditions, the adjustment on the cam position sensor is there to set what is known as the "base" timing - the reference that the computer uses to set the actual timing.

[jasmine]

Thanks Rhinoman Yes, as Murcod mentioned, it seems a person called Fordem has already judged me as "lacking in experience and understanding" based on the information in my post. Sad though, it would have been good to hear how he went with it. I guess I will never know

[Rhinoman]

Fordem wrote:

The engine seems to be set for around 20* BTDC - with the jumper in - and there is around a 5* variation (at idle) if the jumper is removed & reinserted. This is way more than the FSM specifies but is not that unusual here in Guyana, we get only one grade of gasolene - super unleaded - and it is common practice to advance the timing to take advantage of the power available.

http://rhinopower.activeboard.com/t3075 ... 043&page=2

[Gwagensteve]

I'm not sure if J20's are knock sensed or not. If they are, then increasing the base timing will achieve almost nothing - the ECU will already run the car with as much advance as possible. more base timing will only really effect idle and coast conditions.

If they aren't knock sensed, you're on a slippery slope - whilst upping base timing might improve low end torque, it will also increase the likelihood of detonation (pinging or pinking) I have found that small increases in base timing (with a turbo 660 motor) made the car VERY sensitive to fuel quality and ambient temperature - detonation was only ever a flex of the ankle away if it was a hot day or I had less than 98 octane fuel. I'll add this wasn't with a heap of timing in - only a couple of degrees.

Most modern alloy motors run quite hot (to promote good combustion) and there is little room to add much timing.

[Rhinoman]

I've found that most Suzukis will run a little more advance quite happily and then a little more if premium fuel is used. Usually they use the same mapping throughout the world so they can be quite retarded, the handbook will state the octane rating that the ECU is (conservatively) tuned for.
The knock sensors on the earlier models are only used to retard timing from the 'standard' settings they won't advance to optimise the timing for a higher octane fuel.

[droverdave]

Gwagensteve wrote:

I'm not sure if J20's are knock sensed or not. If they are, then increasing the base timing will achieve almost nothing - the ECU will already run the car with as much advance as possible. more base timing will only really effect idle and coast conditions.

Doesnt work like that. Ecus have a base timing map in them, which then takes inputs from sensors and under certain events will retard this timing. So if a knock event occurs (knock sensor voltage above pre determined threshhold), then it will either knock out X degrees of timing across the board, or it will knock out X degrees of timing at that load cell only. As far as i know ecus never run the maximum timing they can, they merely have a pre determined base timing map and then this is retarded on knock events.

So its possible that if you are not at the knock threshhold then you might get a bit of extra go out of the engine (when using higher octane fuel), by spinning the CAS a few degrees.

Problem is, maximum brake torque (MBT) can occur before knock threshhold, so you can get more torque with a more retarded timing for a given load point.

I experienced this with my drover, i cranked up the timing and threw in some 95 octane, it "felt" faster on the street and it wasn't pinging. I jumped on the beech and it was really slow....and the poor engine was laboring. Got to the camp site wound the timing back a fraction, and it went 100% better.

On the other hand my old 4age, I advanced the timing a butt load and ran 98 octane, and it was definitely better.

Different engines respond in different ways.

So yer give it a go, but be aware more advanced timing does not equal more torque. and when you are adjusting via the CAS, you are adjusting timing across the entire ignition map. Being non turbo you arent going to blow it up with a bit of experimentation, just don't make a habit of driving around with it pinging its head off....

[Rhinoman]

droverdave wrote:

Problem is, maximum brake torque (MBT) can occur before knock threshhold, so you can get more torque with a more retarded timing for a given load point.
I experienced this with my drover, i cranked up the timing and threw in some 95 octane, it "felt" faster on the street and it wasn't pinging. I jumped on the beech and it was really slow....and the poor engine was laboring. Got to the camp site wound the timing back a fraction, and it went 100% better.
On the other hand my old 4age, I advanced the timing a butt load and ran 98 octane, and it was definitely better.

Years ago it was more common to optimise the timing, the 'rule of thumb' was to set it so it felt just right and then back it off around 2 degrees. The theory was that an engine always felt better when it was a little over advanced. The old engines that I played with had a thumbwheel adjuster on the distributor.

[jasmine]

Thanks everyone for your responses so far They are all quite interesting and informative reads.
Does anyone know if there are any dangers with NOT plugging in the jumper/service wire?

Somebody had previously drawn a line across the adjuster and the mount with a paint-pen, so I can easily return it to stock. According to what I can see in the manual, twisting the unit towards the driver's side will advance the base timing (seeing as it's connected to the rear end of the cam). I've experimented a little (with the engine switched off) by loosening the torx bolt and twisting the sensor unit toward the passenger side (anticlockwise while looking at the back surface of the engine) to see how it runs with less advance. I was surprised after a test-drive that it actually accelerated quite smoothly from the bottom end and then had a strong surge of power at about 3500 rpm. I haven't tried advancing yet, but it will be interesting to see how that goes too

[Rhinoman]

You can move the cam sensor without using a jumper, the jumper fixes the timing advance so it can be set accurately with a timing light, without the jumper it moves around a fair bit as the ECU continuously adjusts the timing. When you move the sensor remember tat every degree on the sensor is two degrees of change.