Megasquirt Boostcontroler
 

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not unless you have MS-II

I have one fairly specific grievance with the design concept of the MS's EBC system in general, and this applies to all of the units.

The MAP sensor is after the throttle body.

What this means is that in any situation where you are using part-throttle to modulate boost, the wastegate will remain completely shut, with the turbo attempting to make ∞ PSI against the throttle plate.

This can, in theory, be avoided by the use of TPS-controlled EBC targets, though in reality, how many of us are willing to put in the amount of dyno time that it would take to properly tune that system?

I was myself thinking of controlling boost this way. If this isn't the best, what is?

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What's wrong with a plain-ole MBC?

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Needlessly excessive. Most of us, myself included, are running ball-and-spring style controllers. Mine's a TurboXS BC-HPBC, which gives me stable boost with maybe 0.5 PSI of onset overshoot. And I'd wager that I spent more money than was necessary here.

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Ball-n-spring here, no complaints. It's a helluva lot more reliable than the MS's boost control was.

i do in fact have MS2, so hopefully it works out well for me...we'll see in a couple months

I've been running tps based boost control on my unit for a while...not sure what's the big deal on tuning.

Currently I use my MBC to control full boost and the solenoid is run in parallel, when I want to run wastegate I can depower the solenoid which bypasses the MBC and the wastegate opens early. If I only still want wastegate boost at 50% throttle I keep my DC% set to 0% below 50% TPS. It works well and took about 5 minutes to setup my table outside of the car to get it right...

As far as MS's closed loop boost goes, people having problems with it should talk to wes kiser in the msextra forum about how to plumb their solenoids for better response, and about tuning.

He's got my MS3 closed-loop boost control working REALLY well. (It's slightly different from ms2's boost control in that the "P" term will now respond to target changes, results in needing to retune the PID parameters, but looking at his datalogs, it's worth the time).

Ken

I'd be very curious to see that. Don't tempt me with MS-III stuff, I just got MS-II working. :-P

One possible alternative: MBC set a few PSI above target in the IC piping, just ahead of the throttle plate (trust me, a few extra PSI yields some great throttle response, without the loss of boost at the top end associated with taking the signal pre-intercooler housing) in parallel with an EBC in the manifold.

Differing boost targets would be awesome, I wouldn't poo-poo it as quickly as our Esteemed Moderator has, but will admit it would take some work (less, I think, than tuning the map without it, actually?)

Anyway, the parallel idea is probable one of the better ways to go, though I'm not sure how much havoc it would play with any PID routines looking for a response and getting none.

Ken, can you comment on this, or perhaps suggest some limits you could put on to help this function well?

I heard ms-iii is cool...

I say its worth it if you get it tuned properly. Mine was fine but i found out i had a boost leak while tuning when i got home...so i fixed and it spiked over 21lbs...so i just went out and bought a Forge MBC. This may be a dumb question but could i route a vac line all the way inside by the dash and put my mbc beside or under the dash and run the other vac line back to the turbo? Would that fuck up the boost settings?

When the CPU isn't fried :P

It's a bit after the horse has bolted, but FWIW I installed a cap on my MSII and it stopped me revving above 5k so I took it off. I don't see why you should need it either, just build the 2nd Opto circuit and be done with it.

if the CPU wasn't fried :fawk:

Ha ha great news Brain :)

My previous statement still stands tho, dump the cap and build a 2nd opto circuit.

yeah well, maybe after it's repaired... :cry:

Sorry I thought your previous statement meant it wasn't broken! :(

no, I was saying if it weren't brokenz, i'd probably go build the second hall circuit.

Why is your car always borken? :-P Don't feel bad, I'm building a new motor because I'm just... suspicious about mine. And because I like horsepowerz.

Forge, wow, fancy. I'm a big fan of the Cheap. Just ask any girl I take out. :-) That said, much better than running the lines in the cab, which will give you overshoot and poor control.... Run a long cable into the cab, the kind you can twist, like a speed cable. I've heard of people do this and they are happy about it.

Another option, JoeP does this - he puts a couple solenoids in the cab with an MBC each, and energizes one or the other depending what boost he wants.

Personally, I just tune for high boost and alter boost with the throttle.

LMAO. Well Forge was the cheapest one if you can believe that, buddy owns a performance store. I think it was 80$...meh. To much work to do all that. Il just keep her at 30lbs, just try to keep my foot light ;). I like my EBC but she went all fucky last year i will try to fix her at the dyno this year if not il just the forge, alot easier to operate but you just have to turn it up or down and usually when you have the boost down is when some tool wants to race.

my car isnt, my 3 day old MS-III CPU is.

interesting read on the boost controller likes/dislikes. I need to learn more about MS

Oh, the ones you build from McMaster parts are like $15-30 depending if you throw a light weight ball in there, etc.

30 psi is quite a bit! But yeah, control it with the foot, or a single solenoid and two MBC's. Won't cost a hell of a lot.

You could also go the "calibrated leak" route - then your solenoid can be much smaller. Put a small orfice (0.020"?) on a T with a solenoid, and that leak will let the wastegate respond slower and give more boost.

If you are auto-x or tracking I'd say controlling boost with your foot can be interesting. My datalogs show me doing most of a good auto-x run with small spikes to 100 % TPS and much of the acceleration during runs is around 60 % TPS with 10-11 PSI in 2nd gear. So anything above 50% basically = full boost.

It's a testament to what a bad driver I am, but I find turbo lag the only way to get traction in an autocross. :-)

Have you gotten the hardware back together yet so I can load the bootloader for you?

Also, based on your post on the msextra forum, it seems like you're having better luck with the PID boost control on ms2.

Ken