mrfred

iTrader: (50)

I made it sound as if hacking off that nub was a simple as grabbing a hack saw. Its definitely more complicated than that. Cutting anything off would throw the assembly out of balance, and the issue of when the valves start smashing into things would take some time to figure out. And if it could be done, there's no guarantee of any signficiant gains.

mrfred

iTrader: (50)

I mentioned in the thread I started on the various load variables used by the ECU, but I'll mention here again that MIVEC uses the same load variable used by the stock boost control system. This load variable can track as much as 20 load units below the load used for fuel at high IAT temperatures.

esevo

iTrader: (11)

I understand, I think it would be better if we had one made that was balanced and all... Im sure our major companies in japan have looked at making aftermarket cam gears for the IX for even more adjustability.

MR Turco

iTrader: (16)

very interesting stuff mfred. I personally think what we have available is good enough. There are so many factors into manipulating something like that as fred said that it is probably not worth it in the end.

I have yet to see a company come out with something for the STi which has be using this same technology for years so i doubt we will see anything in the near future.

joedr

iTrader: (27)

Subscribed!

mrfred

iTrader: (50)

At lunch I raised the software upper limit on the MIVEC advance from 28.8 deg to 30 deg. The software limits are two 1D tables found at 0x293A and 0x293C on a USDM Evo IX. They are two-byte values. These can be viewed as uint16 with a scaling of 72-0.6x/32.

The result is that even with values of 30+ deg in the MIVEC table and 30 deg in the software upper limit, the actual MIVEC advance does not exceed 28.8 degrees. See table below. So, I'm very certain now that the true MIVEC upper limit on the Evo is 28.8 degrees. All you people with values of greater than 28.8 deg in your MIVEC table can turn those values down to 28.8. :-(

GTLocke13

iTrader: (1)

From what I read it sounds like the valve controlling oil pressure to the cam gears is on an independent feedback controller. If you set the setpoint at 28.8 it will control the valve so the cam advance is right around the bump stop. Setting it to 30 will most likely force it to try to control to 30, so the control valve will go wide open and use as much oil pressure as it can let through to force the cams against the bump stop. This may reduce flutter on the cam position....? I doubt it'll make any real difference.

This is all speculation, but it would be interesting to compare a 28.8* log vs a 30* log to see if the amount of position variation changes.

dudical26

iTrader: (17)

I really don't get why the Evo uses so many different load variables. I wonder if it makes sense to have the ECU use one load variable for everything. It would certainly make tuning easier.

mrfred

iTrader: (50)

The MIVEC max advance setting can be thought of as the feedback on the hardware limit. Your assessment of what happens when the upper limit is set to 30 is mine as well. Not sure about the flutter. Could be some, but hard to say as some of the variability in the MIVEC logs could just be resolution related. Without some knowledge of the capability of the MIVEC hardware, it worries me to let the valve be held open continously at full advance (normally the valve would close upon reaching 28.8 deg), so I am not willing to leave the upper limit set to 30 deg.

Not sure why you say its speculation. I've logged MIVEC with the upper limit set to 28.8 deg (factory value) and 30 deg. Both plots are in this thread. In both cases, MIVEC did not exceed 28.8 deg.

tephra

iTrader: (6)

I'm just waiting for mrfred to find the mivec link to the timing 1,2,3 decision tree :P then I wont have to do some pretty graphs to prove it :P

GTLocke13

iTrader: (1)

I meant the part about there actually being a difference in how the feedback controller sees an input of 28.8 vs 30. If the output is a 1-5V signal and the scaling is set so that 28.8 in the ECU is 5V then it won't make any difference either way. It was my way of saying that I'm making a WAG.

mrfred

iTrader: (50)

Found out this evening that while 28.8 deg looks for certain to be the upper limit on MIVEC, 0 deg is not the lower limit. I was able to push the MIVEC as far as -1.6 deg by altering the lower limit and adding negative values to the MIVEC table. So, it looks like the total range is around 30-31 deg, with it spanning from around -1.6 deg (logged) to around 28.4 deg (also logged).

Not sure how much value there is to be able to go negative by -1.6 deg. I suppose the place to use it would be at higher rpms.

If you want to see the MIVEC upper lower limits, add the following two entries to your 88590015 xml file:

---
<table name="MIVEC Bounding Minimum" category="Timing" address="293A" type="1D" level="1" scaling="ValveTiming16"/>

<table name="MIVEC Bounding Maximum" category="Timing" address="293C" type="1D" level="1" scaling="ValveTiming16"/>
---

Then add the following entry to your evo9base.xml file (if you're using post 1.29 version of ECUFlash, use "big" instead of "little" endian):

---
<scaling name="ValveTiming16" units="degrees" toexpr="72-x*0.6/32" frexpr="(72-x)*32/0.6" format="%.1f" min="-1.8" max="28.8" inc="0.1" storagetype="uint16" endian="little"/>
---

RazorLab

iTrader: (8)

Interesting, so you had to alter something for the car to actually do -1.6 when you had -1.6 in the table?

mrfred

iTrader: (50)

Yep. See my edited post above. Besides the MIVEC table, there is a bounding upper and lower limit setting in the ROM. No matter what you put in the MIVEC table, the MIVEC will not exceed the bounding limits. And of course there is the physical limitation on the MIVEC range which trumps everything else. :-)

RazorLab

iTrader: (8)

Cool stuff. mrfred for pres!