Electronic Feedback (active) Boost Controller -- have a cheap prototype need input

[Darth Fiero]

Have a friend in the Fiero community who builds involved electronic circuits. The last project he helped put together was an OBDII flight recorder that plugs directly onto the OBDII scan tool port that Rental Car Agency's can use to monitor the use of their vehicles.

Anyway I approached this person with a proposal. I have been looking for a good electronic boost controller for some time. The only ones I have found which were any good cost $300.00+. So I asked him if he could build a stand-alone, simple circuit that would work in conjunction with a 2- or 3-bar map sensor and activate/deactive the wastegate solenoid. He came up with the following design:

It is a 2.5"long x2.5"wide x1" thick box with an adjustment knob and simple boost scale. This device only needs 12v power and ground and sends out a 5v ref signal to a 2 or 3 bar map sensor and accepts the incomming signal. It has a switching ground output for the boost solenoid. It can be reconfigured to work with either a 2 or 3 bar map sensor by flipping some jumpers on the inside of the unit. What it is supposed to do is turn off the boost solenoid (limit boost) whenever the boost read by the MAP sensor exceeds the boost setting on the unit. The boost setting has unlimited adjustibility 0-14psi using a 2-bar map sensor, and 0-29psi using a 3-bar map sensor. After the boost drops below the set value the unit will re-energize the boost solenoid to increase boost. In theory it should maintain a preset boost level without much fluctuation in boost pressure.

This is a simple on/off controller. It can switch very quickly so there should not be any surge. If there is, I can have him redesign the output circuit from on/off to variable PWM or D/C. I have yet to test this design and see how well it works because winter hit before I got it in the mail.

The question I am asking the TB community is: if this device works, would you be willing to pay $100 for it? Understand I am NOT selling these, but I would just like to gauge interest at this time and find out how many people would be interested in something like this. If this unit works for me then I will suggest to my friend that he market them to the TB community, if there is enough interest. Furthermore, are their any other features or suggestions you would like to see in a unit like this?

 

[scottyb]

Everyone has different needs because of their setup, so you'll likely get a load of suggestions.

The main reason I went with a BSTC is because I needed to control spike on my stock turbo/stall. I did this by setting my turn-on trigger very high (~85% throttle). Did the job perfectly. Your on-off setup would not help me in this regard. You'll need to do something as you've suggested to pulse the solenoid before max boost - maybe a staged setup with dip switches.

Many here will want a 3rd gear scaling. I don't use it, but many probably would.

 

[Drac0nic]

The actual design shouldn't be too bad, I'm eventually gonna do mine when I get some more experience with PIC micros. Use a rotary encoder, a PIC have an LCD/7 segment display then use an ADC off of the MAP sensor (unless you're designing it for an existing 2 or 3 bar MAP, use a different (read:cheaper) sensor) If you want to I'll give some design points and links to help out with your design, yours for the asking.

 

[Razor]

There are limitations to the stock WG bleeder, hence the need for a bigger valve. Then there is the ability to control the rate of progression so tire spin can be controlled. And then the need to setup when you want the solenoid to start cracking open(grainger valve) electronically.

Then have the ability to run high or low boost.

Personally I like the Greddy Profec B spec II. The only thing I dont like is I cant incorporate 3rd gear scaling. The rest of the piece is the cats meow. has a 4 bar MAP built in, boost recall, scaling, overboost reduction, etc.... and for the 300.00 the bells and whistles have been figured. While 100.00 is attractive, you add the MAP, the HD solenoid.. your over 200 and no where near the features.

The BSTC will adjust your boost accordingly, tho there is no ref feedback. But has the 3rd gear scaling.

For something simple.. neato

 

[salvageV6]

Incorporate a Motorola MPX4250AP for about $20 and you have a 3+ bar MAP that is designed for automotive use for a reasonable cost.

Potting and the connector are extra.

Hopefully the feedback loop has runaway protection and can be reasonably well tuned etc.

I like the BSTC due to it's simplicity and don't have any spike or overboost conditions with it. Spoolup code is great in the unit as well.

 

[Razor]

Originally posted by salvageV6
Incorporate a Motorola MPX4250AP for about $20 and you have a 3+ bar MAP that is designed for automotive use for a reasonable cost.

Hummm... interesting.. so how is it you get a 3 bar reading from a 2.5 bar sensor


.. gotta keep ya in-line

 

[Drac0nic]

Originally posted by Razor
Hummm... interesting.. so how is it you get a 3 bar reading from a 2.5 bar sensor


.. gotta keep ya in-line

Yeah, I was wondering similar. They DO however make one that's good for 44 or 45 PSI I think, it's not too much more expensive and Digi-key carries em. Major hitch here being that you'd lose resolution, then again even a basic PIC ADC has 10 bit resolution if I'm not mistaken so it'd work out.

 

[salvageV6]

You can use any of the line you want plenty of styles to suit all applications I would think you'd want to include the 3+ bar guys like the stockers going for broke and the TSM guys.

The price is right.

36 psi. is plenty for me.

 

[salvageV6]

Since it is a pressure transducer capable of reading 36 psi. it will have 3+ bar resolution assuming you can ignore atmospheric pressure which in a boost controller would be a reasonable assumption. Minimum voltage output at 0 psi. or atmospheric.

3 bar map reads 30psi. actual boost I assume.

2 bar map reads 15psi. or so actual boost.

This device should resolve more pressure and certainly more than most use, but not all I guess.

 

[Razor]

So salvagev6, is the Motorola MPX4250AP a 2.5 bar sensor or a 3.5 bar sensor??? Or what is it.

I see a crab doing the left and right Its ok to admit you made a mistake..your old enough..





Ok.. so which is this majical sensor that reads 36 PSI and has an easily accessible pressure port so a hose can be attached to it?


Such a shame they dont make that MPX4250AP package in a higher pressure unit...

Ohh well.. back to the GM piece..

 

[salvageV6]

A GM 3 bar MAP sensor can sense 30 psi. boost pressure, allegedly, never owned one myself got that off the internet.

The motorola can sense 36psi. boost pressure.

Tried to make that clear for you.

The mistake was semantics only trying to compare it to the GM units.

IF the GM 3 bar unit can sense 44 psi. it would be a better choice in some applications not sure if it can.

Got the 15 psi. MPX5100 sensor working as an alky. switch at 11 psi. boost for my car. Also have some nice LED outputs for 5, 10, and 15 psi. boost.

Don't know if you call it a 1 bar or 2 bar MAP I call it a 15 psi. sensor.

That would be above atmosphere of course.

Spec.s are available online, go read them, you can keep the GM $$$$$ MAP after all it's your money.

Has a nice hose port right on it, same type as Eric Marshall had on his DPS unit. It fits about an 8mm hose I used silicone ricer hose, I think the SMC hose will work fine on it.

Fish tank hose whatever you got after all it's DIY cheap and easy and accurate too.

Was only a suggestion should the controller need an accurate 36 psi. pressure reading approx. .2 to 5 volts output.

Or any controller for that matter.

Edited within the 10 minute time limit for your enjoyment.

 

[salvageV6]

The "magical" one is MPX4250GP.

And yes it has a port for a hose.

 

[Drac0nic]

Originally posted by salvageV6
A GM 3 bar MAP sensor can sense 30 psi. boost pressure, allegedly, never owned one myself got that off the internet.

The motorola can sense 36psi. boost pressure.

Tried to make that clear for you.

The mistake was semantics only trying to compare it to the GM units.

IF the GM 3 bar unit can sense 44 psi. it would be a better choice in some applications not sure if it can.

Got the 15 psi. MPX5100 sensor working as an alky. switch at 11 psi. boost for my car. Also have some nice LED outputs for 5, 10, and 15 psi. boost.

Don't know if you call it a 1 bar or 2 bar MAP I call it a 15 psi. sensor.

That would be above atmosphere of course.

Spec.s are available online, go read them, you can keep the GM $$$$$ MAP after all it's your money.

Has a nice hose port right on it, same type as Eric Marshall had on his DPS unit. It fits about an 8mm hose I used silicone ricer hose, I think the SMC hose will work fine on it.

Fish tank hose whatever you got after all it's DIY cheap and easy and accurate too.

Was only a suggestion should the controller need an accurate 36 psi. pressure reading approx. .2 to 5 volts output.

Or any controller for that matter.

Edited within the 10 minute time limit for your enjoyment.

You're forgetting one thing, it's *absolute* pressure. It sees vacuum as well as boost, hence a 3 bar MAP will go down 1 ATM vacuum roughly, then up to 2 of boost roughly.

http://www.freescale.com/files/sensors/doc/data_sheet/MPXY8021A.pdf
check this bad boy out, rated to 92 PSI absolute pressure
For those not in the loop, Freescale=old motorola semiconductor division..

 

[Razor]

The point is bad information gets put out..some one catches it, and the poster instead of saying "My bad, I made a mistake".. keeps rambling about bla bla bla.

The MPX4250 will only read to 22.5 PSI. Look at the sheet..its at 4.8 maxed out at 22.5. Whether you can blow 30000 PSI on its nipple.. doesnt matter. The boost run on the GN's will typically exceed the 22.5 that sensor will read. So it is not appropriate for our cars for anything that would need tracking past 22.5 PSI.

The GM 3 bar reads to 29.4 PSI to get technical. That is why its known as a 30 PSI sensor. Once it reaches 29.4 no further increase in signal.

Open mouth, insert foot... In this case the keyboard did you in.

On another note,

Drac0nic, see the issue I see with the other various sensors that can read higher is their packaging. There is no way to readily attach a hose to its nipple on any sensor above the MPX4250 which is about as useful as tits on a bull.

Unless I made a mistake in reading the lit, I cant see an easy way except for some sort of moulding/encasing/etc.. to get a solid connection so pressure can be applied to its orfice.

 

[Drac0nic]

Originally posted by Razor


On another note,

Drac0nic, see the issue I see with the other various sensors that can read higher is their packaging. There is no way to readily attach a hose to its nipple on any sensor above the MPX4250 which is about as useful as tits on a bull.

Unless I made a mistake in reading the lit, I cant see an easy way except for some sort of moulding/encasing/etc.. to get a solid connection so pressure can be applied to its orfice.

Yes, an encasement would be required but those are about $10 each from Motorola in quantities of 1,000 or greater. What's a 3 bar? I believe even you sell them for around 70 bucks. I would probably end up making it so that there would be the nipple coming out of a block of epoxy or similar. For a mass produced product there's significant cost savings to be had. A small board and a box with the connector would be a good idea, my only concern would be that it'd be too big for the restrictive line to have decent response.
But honstely, the 3 bar GM has advantages. Keyly that a *lot* of people already have them, (for your alky controller for instance, or ME/R) and they're proven to work well out of the box. If someone built a harness piece that'd tap into the MAP sensor it'd make install a lot simpler too.

 

[Drac0nic]

Originally posted by Drac0nic
Yes, an encasement would be required but those are about $10 each from Motorola in quantities of 1,000 or greater. What's a 3 bar? I believe even you sell them for around 70 bucks. I would probably end up making it so that there would be the nipple coming out of a block of epoxy or similar. For a mass produced product there's significant cost savings to be had. A small board and a box with the connector would be a good idea, my only concern would be that it'd be too big for the restrictive line to pressurize in response and in turn not have decent response.
But honstely, the 3 bar GM has advantages. Keyly that a *lot* of people already have them, (for your alky controller for instance, or ME/R) and they're proven to work well out of the box. If someone built a harness piece that'd tap into the MAP sensor it'd make install a lot simpler too.

 

[salvageV6]

Since when do you need vacuum readings to make a boost controller? You remember the topic don't you?

Okay you can remove your foot from your orifice as well.

Mistake was corrected in the proper part number required for the MPX4250 family.

Perhaps I should have used your qualification if I read the data sheets properly LOL.

The 4250GP will work fine with a port and have better BOOST resolution than a 3 Bar map which really doesn't read 3 bars boost now does it?

As far as rambling it's called posting relevant information.

I am confident anyone building a boost controller could pick out the right $20 part to use from the lit.

Absolute pressure is not really relevant for a boost controller in MHO, nor for a boost gauge either.

Not sure why you need to sense vacuum on an alky. controller either, I don't intend to use it for that for sure on mine.

A couple of charts have 3 bar listed as 44psi. so I guess the GM falls a bit short in that regard.

Semantics, absolute vs. gauge.

 

[Razor]

Talk bout missing a few cards in the deck.

Ok... show me a 20.00 sensor that reads at least 30 PSI pressure and has an easily attachable port... come on.. There is a 36 PSI one but the nipple is too small to be used with a simple hose.

Gosh i'm sure glad my boost controller reads to 42.5 PSI(4 Bar) so it can adjust.

Then here you go saying a OEM part is too expensive( A whopping 50 dollars on GMpartsdirect.com), yet will spend 1000+ on a mismatched turbo




Now to serious thought,
Drac0nic, altho a few bucks more, the 3 bar from GM is plug-n-play on the Buick. Connector is already there on the passenger inner fender and requires no mods typically. So while its a few dollars more, the sensor has been proven almost bullet proof. That's worth the extra 30.00 in my book. 20 dollar sensor is never 20.. becuase it still needs encasing, plugs, hoses, shipping, handling, and fabrication. And reality the GN is capable of running upwards of 25+ PSI. On doing large volume.. yes there is savings initially. Tho in the long run.. dont know. Would suck if the encasing came apart for whatever reason at 28 PSI boost.. and you'd tell the customer.. I was trying to save you 20 bucks.. sorry bout the motor..how bout another free sensor.

I like the resolution on the GM piece for the Buick apps. Few are running past the 30 PSI range anyways. And the packing/reliability is already figured. There is a 5 bar made by one of the Jap companies suppossedly very accurate. I have a shop that installs the AEM and specifically uses the 5 bar. Reason is the sensor is always the same. And once they load a program from one vehicle to another the same results are predictable. That is a flaw in the GM 3 bar. There is always a little variance. I hope this note is useful in the boost controller design talked about on this thread. So a zero reference would be nice so it autozero's to atmoshere.

For my purposes, the ME-r, boost guages, etc.. its very predictable.

Back to square one

 

[Drac0nic]

Originally posted by Razor
Tho in the long run.. dont know. Would suck if the encasing came apart for whatever reason at 28 PSI boost.. and you'd tell the customer.. I was trying to save you 20 bucks.. sorry bout the motor..how bout another free sensor.

the "D" variety he mentioned is not an absolute pressure sensor, but just a pressure sensor so it really will show boost rather then a vacuum boost split. It will see about 36 PSI of boost.

http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250D.pdf

Ye olde data sheet.

For the Buicks, it'd make sense to use the 3 bar, if you read my post through you'd see I made that point. My point being is that the appeal would probably fall over a larger group if you didn't cater to one sector in particular. The other thing being is that calibration to a different MAP sensor is not exactly the biggest of task, you take a different batch of ranges from the ADC and you use them as your set points in a table of your microcontroller. You make it sound like you'd have to redo all the code or something. It's not exactly a big bloody deal or anything.

 

[salvageV6]

Both my cars use the DPS prototypes from Eric Marshall that has the same type sensor and plastic package, the hose fits fine as I previously posted. I think it's a simple hose connection, 4mm on the bench with no clamp or zip tie at 15 psi.

In the car I zip tie it to run TSM level boost.

You can superglue or tie wrap it on like in the SMC kit instructions.

Here's a link to a good 4mm hose supplier, nice people and they guarantee HP improvement with the right color so you know they have a sense of humor. Good silicone bump adapters and other hoses as well, probably got the link from tech. here anyway.

http://www.roadraceengineering.com/hoseandclamps.htm

I think Pep Boys, NAPA, Autozone, etc. just might have a T fitting or adapter that will work from 3/16", 1/4" whatever you want to use off the car to the nipple size.

Overpressure spec. is a bit higher than 28psi. LOL, go read the specs. they are out there.

I've calibrated the one in Erics prototype with the little plastic case and nipple at 30 psi. several times, it's also accurate to within 1/4 psi. from my reference Omega gauge when using the relay switched outputs for triggering things like alky. stages or peak boost led lights so you don't have to watch the gauge while racing, it's easier to see the bright led's on the display I made also rather than the gauge.

Those type sensors are out there and being used daily and have been for years. Yup real world results no need to tell customers anything, I'd also check with Motorola for OEM projects since they may actually be used in autos. you know one of the design applications.

I believe Wagon has one on his car as well to run some alky. triggers never heard him complain of the hose connections or reliability of the unit. Been on his car a long time too.

Easy to do for a DIY project or new design.

Damm thought the gooroos could design around a SIMPLE 4-5mm hose. LOL

That works out to .2 inches give or take a bit, no BARS in that conversion.

Might be missing a few cards but the Ace of Spades up the sleeve always wins.

Remember more boost range than a 3 bar GM MAP, 36psi.

And if you don't like the part you don't have to use it, after all it's for DIY no SALES PITCH here, just some design info. and real world results, you may spend your money where you wish like stocking up on head gaskets.