RB26 Tomei oil restrictors

[joshuaho96]

1 minute ago, Murray_Calavera said:

@joshuaho96 

Its getting to the point where buying your own dyno might be the cheaper option for you in the long run lol

My grand plan is to start by blindly replicating the stock ECU map, then going from there. Hopefully it dramatically reduces the amount of dyno time required.

[GTSBoy]

An arduino based controller could do all that you ask of it Josh. The accumulator could quite reasonably be located any number of places. I myself wouldn't have any problem with the idea of it being in the boot. There's space, and there's plenty of protection for the lines, and more protection can be added.

[joshuaho96]

38 minutes ago, GTSBoy said:

An arduino based controller could do all that you ask of it Josh. The accumulator could quite reasonably be located any number of places. I myself wouldn't have any problem with the idea of it being in the boot. There's space, and there's plenty of protection for the lines, and more protection can be added.

This is true, but the list of things that I would need to repeat this for is long enough that I may as well use the E2500 I already bought. VCAM, PWM fuel pump control of a brushless pump, and flex fuel are things I really want to do. I plan on seeing if I can survive without an accusump first using just oil pressure sensing + hard fuel cut if it drops out, then add accusump + associated headache if I'm constantly running into engine protection for my particular operating conditions.

[MBS206]

2 hours ago, joshuaho96 said:

This is true, but the list of things that I would need to repeat this for is long enough that I may as well use the E2500 I already bought. VCAM, PWM fuel pump control of a brushless pump, and flex fuel are things I really want to do. I plan on seeing if I can survive without an accusump first using just oil pressure sensing + hard fuel cut if it drops out, then add accusump + associated headache if I'm constantly running into engine protection for my particular operating conditions.

Your issue with pressure sensing, is time delay.

Sensors take time. The ECU takes time to cut.

The engine takes time to spin down.

All that time = bearing damage possible or actually done.

 

The accusump being a mechanical system however, reacts very very quickly.

 

It's the one thing you pickup very quickly I  control systems. Mechanical systems typically react wayyyy quicker... On something like oil starvation, it's best to protect yourself in first line of defence against damage with something like accusump than ECU cuts.

 

ECU cuts = last line of defence...

[Murray_Calavera]

48 minutes ago, MBS206 said:

Your issue with pressure sensing, is time delay.

Sensors take time. The ECU takes time to cut.

The engine takes time to spin down.

All that time = bearing damage possible or actually done.

 

The accusump being a mechanical system however, reacts very very quickly.

 

It's the one thing you pickup very quickly I  control systems. Mechanical systems typically react wayyyy quicker... On something like oil starvation, it's best to protect yourself in first line of defence against damage with something like accusump than ECU cuts.

 

ECU cuts = last line of defence...

Josh's Haltech 2500 samples the oil pressure sensor at 50hz, I wouldn't call that slow. The engine protection activation time will be set by Josh, so he can set it to whatever he thinks is appropriate.

I 100% agree with the essence of what you are saying though, and I would advocate for both the accusump and engine protection, I just wanted to add some numbers to the 'sensors take time' bit. 

[MBS206]

2 minutes ago, Murray_Calavera said:

Josh's Haltech 2500 samples the oil pressure sensor at 50hz, I wouldn't call that slow. The engine protection activation time will be set by Josh, so he can set it to whatever he thinks is appropriate.

I 100% agree with the essence of what you are saying though, and I would advocate for both the accusump and engine protection, I just wanted to add some numbers to the 'sensors take time' bit. 

At 50hz sampling, at 7,500RPM, your engine will rotate over two times between samples.

 

Now when you get the data sheet from the sensor, read the sensor delays.

By the time you've lost oil pressure, your engine has rotated a few times around before the ECU cuts power.

Now it has cut power. GREAT!

Except on power cut, you're still in gear, the cars still moving, that engine is still spinning.

Give it another 500ms at absolute best for you to punch the clutch in. That's another 62 rotations.

It's still going to take over another half a second at minimum because of momentum for the engine to stop.

So if you've got ninja like reflexes and will punch the clutch immediately on power cut (chances are, you won't hit it that quickly as you won't be ready for it), then your engine has "only" spun at minimum 130 times with a lack of oil pressure...

 

Or an accusump means it spins 0 times with no oil pressure...

 

[Ben C34]

Yeah nah mate.

You set up the ecu to open the acusump valve to do its thing during certain conditions, so the ecu isn't making the actual decision, the accusump is..

 

You are just blocking the accusump  operation where you know you don't want it to operate. .

 

 

For example. Valve closed up to 3000 rpm then open. So if oil pressure drops above 3000 rpm accusmp to the rescue. You don't set it so the ecu opens the valve when required . ( even though that wouldn't be as bad as you make it out to be)

[joshuaho96]

9 hours ago, MBS206 said:

At 50hz sampling, at 7,500RPM, your engine will rotate over two times between samples.

 

Now when you get the data sheet from the sensor, read the sensor delays.

By the time you've lost oil pressure, your engine has rotated a few times around before the ECU cuts power.

Now it has cut power. GREAT!

Except on power cut, you're still in gear, the cars still moving, that engine is still spinning.

Give it another 500ms at absolute best for you to punch the clutch in. That's another 62 rotations.

It's still going to take over another half a second at minimum because of momentum for the engine to stop.

So if you've got ninja like reflexes and will punch the clutch immediately on power cut (chances are, you won't hit it that quickly as you won't be ready for it), then your engine has "only" spun at minimum 130 times with a lack of oil pressure...

 

Or an accusump means it spins 0 times with no oil pressure...

 

The idea is to shut off fuel injection before you hit 0 or even some lower theoretical safe value. The moment the sensor detects oil pressure is just lower than expected for the current RPM which could be induced by either the pickup sucking air or excessive oil temperatures thinning things out too much I would want to set a hard fuel cut back to the bare minimum rpm needed to limp to safety like 2500-3000 rpm. With the accusump in place nothing really changes. Oil pressure flatlines after a certain RPM for the most part so the valve can safely be kept open and at high RPM you aren’t waiting on the ECU to see the fall in oil pressure to act. It would just be shut below say 3000 RPM to keep the reservoir full unless it sees oil pressure falling below what normal operation would show. Even factoring the slew rate of the sensor and sampling latency of the ECU I really doubt you’d see the engine fully lose oil pressure before engine protection kicks in. And once it does the violence of hard fuel cut should be enough to get me to stop pushing the car which could be letting off on the brakes/accel/lateral g which would probably also help resolve the situation. And if it happens more than once in a blue moon the answer is to fix the issues causing it as you have pointed out, not just to continue band-aiding the problem with sensors and ECU workarounds.