Variable valve timing with FI

[howelll]

I am interested to hear how some of you tuned your variable valve timing when used with forced induction. Also if anyone has data from dyno runs showing differences.

On my bmw m52 single vanos only the intake valve advances 12 degrees when triggered and its only a on/off solenoid with no feedback. My engine is simple when compared to some of the newer systems out there you guys may be using. I am using one of the general pwm outputs to control the solenoid on a map/rpm table. It is triggered on above 1200 rpm and 50 kpa up to 4500 rpm and 135kpa. My thought is to use the increased valve overlap to spool the turbo when exhaust manifold pressures are low then decrease the overlap when both when pressures are up. It would seem to me pressures on the exhaust manifold and turbine wheel would always be higher than what is made on the compressor side, so you would not want any valve overlap to prevent exhaust gas pushing back into the intake manifold. That's my theory but what have any of you found in real world testing?

[pit_celica]

Look at this :

http://forum.miata.net/vb/showthread.php?t=276072

Hope this helps!

Sam

[alan1977]

Howell, i do the same on my m50 however, mine is only controlled via rpm
Can i ask what the thoughts are with triggering it only under load? is it better to have the vanos retarded when cruising? this is on a currently NA only M50
any chance of seeing a screenshot of how you have configured the output, i knwo i got it all wrong setting it up the first time lol

[howelll]

Thanks to pitcelica for sharing that thread, do you know if the ignition and ve where tuned for each mode of valve timing or did they both share the same tables?

This is what i have so far, I have also advanced the same portion of injection angle to match since the valve opens/closes sooner with vanos activated

[pit_celica]

At the beginning of the thread, he said that the ignition table were the same for all the dyno runs.

According to this thread, because you have a on-off VVT, you should be at full retard around idle to stabilize RPM. Then you should be full advance at cruise/mid-RPM, and finnaly you should be fully retard at mid/high RPM. As for boost/load, he said that he didn't see any difference at least up to 10 PSI.

Here's a graph I've seen somewhere that says how to set VVT for RPM/load. There are no numerical value, but you get the idea.



Sam

[howelll]

Yea that's pretty much what i have, the areas with 100's the solenoid is activated and camshafts advanced. I confirmed this a composite tooth log.

Hopefully when i get to a dyno i can get some good data to contribute. As far as vvt being only rpm dependent and not load, i believe that it would also depend on turbo sizing. And it may not even be a practical turbo where it would matter with load.

[alan1977]

thanks Howell and celica
Howell, you are obviously on MS3 i cant configure my Ms2 in quite so much depth!!

Interesting.. ive been playing with my vanos recently, originally i only had the cam advanced 1600-5000 rpm... it felt "wrong"
i thought i had my on offs reveresed so tried it on up to 1600 and on over 5k...
this was also opposite to how it should be... although around 5k felt strong as did low end power

I am now working on cam advanced up to 4800 rpm and this seems like a good setup, i might set it to 800-4800 rpm and see if my idle looks any nicer (idle isnt particualrly rough but had issues pulling away cold this morning, engine bogged when lightly revved)

I dont htink on Ms2 i can set it operational between RPMs and over x load, i guess if i set it to rpm <4800 And map >65 that would do it?
that way i would have the solonoid not active at idle or cruise, only when under load up to 4800? is that a suitable solution? the benefits to the cam retarded at light load is worht while??!??!

[R100RT]

I am interested to hear how some of you tuned your variable valve timing when used with forced induction. Also if anyone has data from dyno runs showing differences.

On my bmw m52 single vanos only the intake valve advances 12 degrees when triggered and its only a on/off solenoid with no feedback. My engine is simple when compared to some of the newer systems out there you guys may be using. I am using one of the general pwm outputs to control the solenoid on a map/rpm table. It is triggered on above 1200 rpm and 50 kpa up to 4500 rpm and 135kpa. My thought is to use the increased valve overlap to spool the turbo when exhaust manifold pressures are low then decrease the overlap when both when pressures are up. It would seem to me pressures on the exhaust manifold and turbine wheel would always be higher than what is made on the compressor side, so you would not want any valve overlap to prevent exhaust gas pushing back into the intake manifold. That's my theory but what have any of you found in real world testing?

I asked this question a while back and didn't get much response. Turbo experts like Hugh McGiness have stated a well matched system should have lower drive pressure (exhaust turbine side) relative to boost pressures developed - but I suspect many installations go so far as to be rather much higher on the exhaust turbine side. You could just add an extra sensor or even manual gauge to measure your readings throughout load development - I did that with a small roll of copper tubing to keep heat from migrating into an analog gauge and found pretty much equal pressure readings up to modest boost levels of 10psi.
Hope that helps your querry.
Lorne.

[howelll]

I am interested to hear how some of you tuned your variable valve timing when used with forced induction. Also if anyone has data from dyno runs showing differences.

On my bmw m52 single vanos only the intake valve advances 12 degrees when triggered and its only a on/off solenoid with no feedback. My engine is simple when compared to some of the newer systems out there you guys may be using. I am using one of the general pwm outputs to control the solenoid on a map/rpm table. It is triggered on above 1200 rpm and 50 kpa up to 4500 rpm and 135kpa. My thought is to use the increased valve overlap to spool the turbo when exhaust manifold pressures are low then decrease the overlap when both when pressures are up. It would seem to me pressures on the exhaust manifold and turbine wheel would always be higher than what is made on the compressor side, so you would not want any valve overlap to prevent exhaust gas pushing back into the intake manifold. That's my theory but what have any of you found in real world testing?

I asked this question a while back and didn't get much response. Turbo experts like Hugh McGiness have stated a well matched system should have lower drive pressure (exhaust turbine side) relative to boost pressures developed - but I suspect many installations go so far as to be rather much higher on the exhaust turbine side. You could just add an extra sensor or even manual gauge to measure your readings throughout load development - I did that with a small roll of copper tubing to keep heat from migrating into an analog gauge and found pretty much equal pressure readings up to modest boost levels of 10psi.
Hope that helps your querry.
Lorne.

Thanks for the great info! I always assumed that pressures on the turbine side would be higher. But if that's the case then valve overlap would be very beneficial as the intake charge would clear the exhaust gasses out of the cylinder very well, more so then scavenging. So what are the specs of your Turbo you did this testing on? I imagine its not a hybrid with a smaller turbine wheel than the compressor like a t3/t4.

[R100RT]

Well, I utilized a Mitsubishi "TD025M-08T" and based suitability more on the application that model is used on (European Mercedes Smart with the 998cc 3 cylinder gas engine which had remarkably similar specs to my old boxer 980 twin). Once the project was well underway I was able to gain a map from the manufacturer, link below.

http://www.msruns.com/download/file.php?id=6191

This is not a fancy unit, regular bearings, wastegate, & quite compact which helps a fared bike.
I do believe it is good for the purposes I set out to achieve (basically "normalize" my bikes performance and leave some room to cut loose if the occasion should provide)
I love my bike, the MS equipment and turbo just make it that much better.
Lorne.