jcsbanks

I'm using an AVC-R but fancy trying the ECU boost control. Reasons are for increased safety as the ECU can pull the boost in fault conditions/excessive knock, stealth appearance etc and just because I want to find out how it works I didn't have the original solenoid pipework as it was removed by the previous owner before they fitted an HKS EVC-V boost controller.

I think I'll plug the AVC-R's solenoid into one of the ECU's twin solenoid plugs.

On my JDM IX ECU (JM8857-08) there are 3 boost target maps, and 6 wastegate maps (plus a 4th and 7th like my 4th ignition map, but I think I can ignore those as they don't seem there on other IXs).

I think the 3 boost target maps mirror the 3 ignition maps which I believe are for low coolant temp, normal use, DTC condition. Changing ignition map 2 changes normal running, so I think changing boost map 2 will do likewise. This boost map is also the one with the highest targets (very similar to USDM JM8859) which makes sense. Adding the 80% boost control load offset gives a target load of about 239% midrange, tapering off at the top - again as USDM. This is actually maxxed out, so I propose to adjust the boost control load offset to 120% to give me a range up to 279% load target.

There seem to be three pairs of maximum wastegate duty cycles. Set 1 again probably mirror low coolant temp boost target - one is flat at 100% and the other has a sculptured curve where the 2nd solenoid isn't flat out. The same values are in set 3 - DTC condition again? Set 2 has both sets at 100% and there are small restrictors in the pneumatic lines to the original twin solenoids which are presumably set to limit the max boost as Mitsi usually seem to do. I'll only use one and try the sort of 65% midrange duty cycle I need to hold 1.65 bar, with the area up to 2750, and the area above 5500 RPM maxxed out to spool up and reduce taper. I think if I leave it at 100% with a 3 port solenoid that it will wildly overboost...

I have a PC based oscilloscope that I might need to rig up to log wastegate duty cycle and boost level to work out how the damn thing works.

Any comments/things to add to the above? Am I on the right lines before I waste a lot of time trying?

Anyone share any experiences of ECU boost control on a IX, especially if they've done it with twin solenoids as on JDM/UK models?

chrisw

iTrader: (2)

interesting... I was looking at my '03 ROM and found something completely different but could follow the same basic algorithm you have laid out.

In the 03 rom, there are 4 boost desired load maps. Maps 1 and 4 are identical, maps 2 and 3 are different from 3000 rpm on up to 7000.

The wastegate duty cycles on all the map entries (4) is 100, like all the maps are disabling some feature on the car.

This is interesting stuff, I would be interested in hearing your results.

jcsbanks

I gather from those that have tuned the VIII that the restrictor sizes govern the maximum effective boost level hence why the maximum is at 100%. Quite an interesting safety method?

Mad_SB

iTrader: (8)

many tuner reflashes will increase the value over 100, mine is at 125 or so. I think this may be more of a cycle timing (cycles per second or something) than a duty cycle percentage.

jcsbanks

Interesting. Puzzled that they bothered to fit two solenoids to the JDM but don't max the first one out then. Think I'll need to measure the duty cycle to find out.

jcsbanks

Here is what I learned from a short drive and a few flashes:

Resistance on DVM of the OEM and AVC-R solenoids is similar. They are virtually plug compatible with a bit of persuasion - no damage to the plugs.

My fuel cut at 285% seems to work My car doesn't det with momentary overboost to 2.1 bar.

The first duty cycle map in my ROM controls the solenoid with the gray plug. Setting max duty cycles to 60% gave similar peak boost to the AVC-R set to 65% - using the same solenoid - the AVC-R one. The load targets and boost load offset didn't work as predicted. I am guessing that the second duty cycle map controls the solenoid with the black plug, but I'll find out tomorrow if there is any difference in control between the two. The only way I got smooth control was with duty cycles set to lower than required to hit boost target. I'll work on getting smooth closed loop control by trying to replicate stock boost with the 3 port AVC-R solenoid first.

Mad_SB

iTrader: (8)

good work man. I see the logic in the mitsu design (at least the us version, single solenoid). By setting the course adjustment with the use of restrictors on the wastegate and solenoid signal line and a solenoid that fails closed you get granular control over a "preset" range of boost and wastegate pressure if the solenoid fails.

I think MailbuJack messed around with using a gm boost solenoid in place of the stock evo unit with his utec a while back, he may have some insight here....

MalibuJack

iTrader: (5)

I also have an AVC-R on my car at the moment, I'll try the same thing on my USDM car. the GM solenoid needs a 1k resistor to more closely match the stock solenoid.

jcsbanks

My car went to the dealer today to get the Mitsubishi branded Cobra alarm fixed as it kept false alarming. They fitted a new alarm control unit and all day haven't been able to start the car since How difficult can it be when it only interrupts two wires?

Anyway, that kills my mapping for today on my day off.

Mad_SB

iTrader: (8)

.. awww man that sucks, that is like taking a day off work to install some new toys, then your wife/girl running off to work and you get half way done and realize you have to go to the parts store......

jcsbanks

Oh well, I did lots of things I had to do instead but didn't want to

More time to play later