Rev limiter M130 2jzgte

[Chad_2jz]

hi guys. So I've notice my rev limiter doesn't "bounce" like a normal limiter, it seems to just hold itself at that rpm instead. Im trying to figure out how to get my limiter to bounce with some ignition cut. I know there's engine speed limit A and B but it doesn't seem to matter if they're set the same or different. Can somebody lead me in the right direction please? Also what should the ignition range and fuel margin be set to? Thanks in advance.

[Stephen Dean]

Hi,

Is there a reason that you want the limiter to add harshness into the engine?

If you want the Engine Speed Limiting to be harse, then reduce your Engine Speed Limit Ignition Range to 0, this will give you 100% Ignition Cut as soon as the Engine Speed hits the Engine Speed Limit that has been set, If you also want to have Fuel Cut Limiting, then set the Engine Speed Limit Fuel Margin and Engine Speed Limit Fuel Range to 0 as well.

What the Range and Margin to is adjust the type and harshness of the Engine Speed Limiing function. If you have the following setup;

Engine Speed Limit set to 7000rpm
Engine Speed Limit Ignition Range 200rpm
Engine Speed Limit Fuel Margin 100rpm
Engine Speed Limit Fuel Range 200rpm

Then what will happen when the engine speed exceeds 7000rpm is that the M1 will start to ramp in the amount of ignition cut applied over a 200rpm range, so if the engine speed gets to 7100rpm, then there will be 50% ignition cut being applied at that engine speed. It will also start to introduce fuel cutting from 7100rpm as the Engine Speed Limit Fuel Margin has been exceeded, and will also ramp this in over a range of 200rpm. If the engine still gets to 7200rpm, the M1 will be applying 100% Ignition Cut and 50% Fuel Cut.

[Juan]

Sorry for bringing back this old post.

What does a 50% igntion cut mean?
Does it means that 1 ignition out of 2 is done?

[Stephen Dean]

Correct, half of the ignition pulses for a given engine cycle will be cut, so a 6 cylinder engine will only fire three times. This is randomised, so you may have fire, fire, cut, fire, cut, cut, fire, cut rather than all of the even or uneven cylinders being dropped.

[Juan]

Correct, half of the ignition pulses for a given engine cycle will be cut, so a 6 cylinder engine will only fire three times. This is randomised, so you may have fire, fire, cut, fire, cut, cut, fire, cut rather than all of the even or uneven cylinders being dropped.

Understood now, thanks for the info.

[Zoto]

Related question but to do with traction engine speed limit fuel margin, and in particular using a negative figure
i.e. having fuel cut come in ahead of ignition cut

In my particular application (2 litre turbo 4 using M130 for the first time) I've read that fuel cut first followed by ignition cut is preferred to reduce unwanted combustion of fuel on exit, and so possible damage to turbo, valves etc due to shock waves.

However my tuner always prefers/uses ignition cut first followed by fuel on the basis when in a situation of traction speed limit (ie under near full load), there is a risk of running lean.

But if the fuel cut is actually stopping firing of the injectors, so similar approach as described in the above post for ignition cut, there is no chance of running lean as there is no fuel at all going into the cylinder.

Can someone please confirm that when fuel cut is applied in the first instance for either rev limiting or traction control there is no chance of running lean as the cut is not a reduction in fuel but a 100% cut to some cylinders.

Thanks (and my first post)

[Stephen Dean]

Hi,

On a port injected engine, you will almost always have a fuel film that has formed on the inlet runner into the cylinder. This fuel film, depending on conditions, can be holding multiple engine cycles worth of fuel. When the injectors are turned off, this fuel film is consumed by the engine on the cycles following the 100% fuel cut happening. This can lead to that cylinder running lean for a number of cycles until either all of the fuel has been consumed out of the fuel film puddle, or it is topped up be the reintroduction of injection. In between the cut starting and the fuel film being fully restored, there is the possibility of the cylinder running lean if ignition is not cut as well.