VVT ideas and testers

Testing and development of Megasquirt 3

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jsmcortina
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Re: VVT ideas and testers

Post by jsmcortina »

Ah... the problem was PT6 rather than VVT4. I believe I've found the problem and fixed it.

I'll email some test code shortly.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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hassmaschine
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Re: VVT ideas and testers

Post by hassmaschine »

would it be possible to have a VVT setting for cranking? I was digging through docs on the S54, BMW is setting the cam timing specifically for easier starting. As it is now, I don't see a way to do that with MS3.
muythaibxr
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Re: VVT ideas and testers

Post by muythaibxr »

Sure it'd be possible, but I'm not 100% sure that there's enough oil pressure to actually make the cam move very fast at crank. It seems to me that by the time the cam is in position, the engine would be started already.

Ken
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
hassmaschine
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Re: VVT ideas and testers

Post by hassmaschine »

Maybe. The vanos unit might hold enough pressure after shut down, or perhaps they're moving to the cranking position another way. Are all vvt systems oil pressure based?

They're doing it somehow, in any case.
jsmcortina
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Re: VVT ideas and testers

Post by jsmcortina »

hassmaschine wrote: Are all vvt systems oil pressure based?
To my knowledge yes.

Maybe these engines have great oil pumps? Certainly my Rover V8 (which is known for having poor oil pump) starts before there's any real oil pressure.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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prof315
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Re: VVT ideas and testers

Post by prof315 »

hassmaschine wrote:Maybe. The vanos unit might hold enough pressure after shut down, or perhaps they're moving to the cranking position another way. Are all vvt systems oil pressure based?

They're doing it somehow, in any case.

For sure VANOS uses oil pressure as do all of the VVT systems I have worked on (bmw, toyota, honda, nissan, VW, GM, hyundai/kia off the top of my head )

Are you sure that the no oil pressure/rest position isn't just optimised for starting? That's how I would do it but of course I'm not a german engineer :lol: .
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AbatelliCristian
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Re: VVT ideas and testers

Post by AbatelliCristian »

I think is necessary activate vvt controll few second after start because the oil press is low and when I start the engine I listen a metal noise. If I disable vvt system the noise there is not....
hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

Regarding cam position at crank, they are in their starting position without oil pressure. It takes oil pressure to advance the intake/retard the exhaust.
hassmaschine
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Re: VVT ideas and testers

Post by hassmaschine »

prof315 wrote:Are you sure that the no oil pressure/rest position isn't just optimised for starting? That's how I would do it but of course I'm not a german engineer :lol: .
I don't know. The S54 is still a bit of a black box to most people. But, that would make sense.
hoveringuy wrote:Regarding cam position at crank, they are in their starting position without oil pressure. It takes oil pressure to advance the intake/retard the exhaust.
so no oil pressure = cranking position. The doc I read just made it sound like they were physically moving the cams to cranking position.

I think the idea of a delay for VVT is a good idea, until the engine builds up pressure. nobody likes rattly engine noises at 5am.. :D
hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

hassmaschine wrote:I think the idea of a delay for VVT is a good idea, until the engine builds up pressure. nobody likes rattly engine noises at 5am.. :D
I now have dual-variable VANOS running on my Megaquirt3! (sortoff...) It's actually running on my VANOS controller but the motor is running MS3...

Anyway, temperature regulates the VANOS deployment. I implemented it with a signal from Nitrous 1 that's active when (CLT>100F) and (fuel load>40) This is similar to the VANOS signal on the M50-series engine that were simply on-off. Motor wouldn't run worth a dime if intake was advanced at low temps.

On a warm start you wouldn't nail the throttle before oil pressure built-up, anyway.
AbatelliCristian
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Re: VVT ideas and testers

Post by AbatelliCristian »

the idea of a delay for VVT is a very very good idea....
Other Idea:
Is possible calibrate the neutre duty for a single solenoid? I have the differents from left and right.
AbatelliCristian
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Re: VVT ideas and testers

Post by AbatelliCristian »

Hi,
James I have tested your code. Is ok. Chanel 4 work.
Thanks
hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

I made the jump from my dedicated VANOS controller to Megasquirt control of my intake cam yesterday. (BMW M54 engine, Alpha 11 code). Works fine so far, need to reduce frequnency from 99Hz and I found that Hold Duty is ineffective. Hold Duty for me is about 72% which is quite a bit higher than what it is on my dedicated circuit.

Anyone have a "known good" PID for this?
jsmcortina
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Re: VVT ideas and testers

Post by jsmcortina »

Why not use the current code?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

jsmcortina wrote:Why not use the current code?

James
Baby steps. Want to make sure Alpha 11 works ok before I jump to the current Alpha. I'm looking forward to CRC new serial, but what else is different in VVT besides 2JZ support?
hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

In converting from my standalone VVT controller to Megasquirt, I noticed that the duty cycle required to hold position is significantly higher. Since this should be a mechanical constant of the solenoid I looked a little closer. My standalone controller drives the solenoid through a MOSFET and a Schottky flyback diode tied to +12volts, the signal is clean. The megasquirt signal confirms the 72% duty cycle but also shows a signifcant amount of noise when the MOSFET is open and also voltage near 40volts (I'm using a 10x probe)

My controller runs at 225Hz, I had Megasquirt at 75Hz. Also tried other frequencies but it didn't change anything.

What's going on here?
jsmcortina
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Re: VVT ideas and testers

Post by jsmcortina »

Have you installed the diode to S12 as discussed in this topic (or perhaps another VVT one) ?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

jsmcortina wrote:Have you installed the diode to S12 as discussed in this topic (or perhaps another VVT one) ?

James
On my list for tonight. What is the current state-of-the-art.... run an additional diode to S12 or just tie D1c to S12?

I will post a pic of the new scope trace, of course.
y8s
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Re: VVT ideas and testers

Post by y8s »

no diode necessary, just connect the cathode of one of the expander flyback circuit diodes to S12.

Right side of the D1, D2, D3, D4 in the top of the picture below. You'll know it is right because of the continuity between all of those cathodes (and you can see the traces).

Matt

Image

and reference:
Image
hoveringuy
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Re: VVT ideas and testers

Post by hoveringuy »

y8s wrote:no diode necessary, just connect the cathode of one of the expander flyback circuit diodes to S12.
Matt
That's what I'm planning, although I'll replace the 1N004s with Schottky diodes. I have found those more effective in my other flyback circuits.
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