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A couple people have asked about this. First of all, I ain't promising anything. Just thinking out loud. My C5 doesn't have forced induction and probably never will, and I'm not sure I want to invest a lot of hard work in something I can't use myself, but, this is an interesting idea. And even if I don't do it myself, maybe we can pave the way for someone else who can do software and actually has forced induction.
Some questions for those of you who want this...
What kind of transmission do you have?
Do you want this for drag racing?
If it only worked from a roll, would that be good enough?
Do you have any idea yet which PCM output you'd want to repurpose for boost control?
Does the boost control solenoid duty need to vary by RPM?
Where is the vehicle speed sensor on your car?
If the vehicle speed sensor is on a front wheel, and if the PCM needs to deduce the current gear from the ratio of wheel speed to engine speed, that's not going to work well if the rear tires are spinning. That could be a problem for drag racing with a manual transmission.
We could do something creative like assuming first gear after the car is stopped, and assuming one higher gear each time the clutch is pressed, until/unless the car spends a couple seconds with a wheel-speed : engine-speed ratio that matches one of the gear ratios... But I'm not super optimistic about that kind of thing working reliably.
If you want this for an automatic, then it's a little easier because the PCM already knows the current gear. But on the other hand, we can't hijack any of the AT outputs to drive the boost control solenoid.
This sounds hard. But if anyone has already put some thought into how this could work, and has come up with a plan that might work, I'd like to hear it.
transmission solenoid shift output from pcm or pressure manifold switch data from the trans back to the pcm
yes but all I need is a clean signal i can output to my EBC
there are two VSS. one on the input shaft and one on the output. I can also easily add VSS via an ABS tone wheel on the front or rear wheels
Joe's method of having a relay logic circuit works well, but if it could be as simple as an analog out signal that really opens it up to the less tech savvy folks like myself
transmission solenoid shift output from pcm or pressure manifold switch data from the trans back to the pcm
yes but all I need is a clean signal i can output to my EBC
there are two VSS. one on the input shaft and one on the output. I can also easily add VSS via an ABS tone wheel on the front or rear wheels
Joe's method of having a relay logic circuit works well, but if it could be as simple as an analog out signal that really opens it up to the less tech savvy folks like myself
Use the wires for the solenoids going to the PCM. They have 12v power going to the PCM when off and are grounded when activated.
For an 80e, one solenoid is only activated for 1st and 4th gear. Wire a dual stage controller in like a turbo smart or Ebay brand that's meant to operate between 2 different settings with a toggle switch, and use the wire between the 1st/4th solenoid to operate the ground on the boost controller.
You'll get a separate, lower boost setting for 1st and 4th and higher boost for 2nd and 3rd.
I think a spark based 2-step would be an easier first step. The best option we have right now is modifying coarse idle tables that don't allow much resolution when adjusting it.
Doing this over the data bus would be the simplest approach IMO. You could do a PWM output signal, something similar to the relay method or anything really. Just use pids to get gear information and anything else you may want to be calculated into things(spark knock?) and set a min RPM to start and maximum RPM/rate allowable per gear. You could even set it up to cut the boost on shifts if you wanted.
I'm pretty sure you can also add or pull timing with mode AE commands at any RPM and while in gear so you could also alter the spark curve if you wanted with out needing to get into the pcm's calibration data.
When I mentioned Arduino earlier I was thinking of something completely standalone, but I really like your idea of reading data from the PCM. If the Arduino is constantly getting current gear, throttle, and RPM, that could probably work really well. And it could drive the boost control solenoid directly. And we can iterate on the software for the Arduino a lot faster than we can iterate on hacked PCM software. Because if there's a bug, it only ruins your boost control.
Depending on the frequency needed something like this might work. This uses a dedicated VPW transceiver over SPI that is slaved to an Uno so the main loop doesn't have to deal with any blocking code from bit banging the data bus. It has 2 N-Channel fets that can handle several amps with out a heatsink, not sure how much current a boot controller takes but I'm sure it's no where near what these things are rated for. They could also be swapped out to P-channel fets with a couple of simple changes depending on what signal type you needed.
Ok let me start out by saying I don't have anything with forced induction nor do I have access to anything with forced induction.My only real experience with anything using boost has been repairing it in stock application's.
So I recently saw a low cost boost controller that was being developed for the Sloppy Mechanics group on facebook, I watched ever one of the videos about its design, bench testing, dyno testing and street testing and the entire time I sat there in disbelief thinking there was something about this I just wasn't understanding because it was so simple of a device. In the case of what I was looking at it was just a OLED screen, a single dial and a PWM output signal. You set a turned the dial to what ever % value you wanted and that's what it ran the solenoid at the entire time.
So what am I missing here.....is that's really as it? Is there no advantage by having some sort of ramp or mapped table it would follow?
What purpose/reason would "per gear" boost control serve? To keep the boost level low until your into the longer gears where the rpms will stay up for longer periods of time?
Would min/max RPM to allow boost be useful?
Would using something like TPS% to boost% be useful?
What about boost control based on ethanol level on flex equipped OS's?
I've never tried it at higher RPM but I know you can pull spark on the P01/P59 using AE control pids in park and at low speed(at least in swaps). If the PCM didn't lock out the PID control by speed or RPM then even spark control by boost pressure and RPM could be possible.
How much do people normally spend on an electric boost controller? Does anyone make a OBD II boost controller?
Just as NSFW has said, I do not have anything that use's boost and I don't expect to need anything like this for my own use in the near future.....so I'm looking for input and suggestions from people that would have a use for something like this. Give me your wish list of what a "perfect" boost controller would offer. And don't just tell me you'd like to do it with the PCM, NSFW has already made it clear what that would take and that's outside of what I'm asking here.
I'm not promising anything but I am looking to gauge the amount of interest in something like this and see what "features" a perfect controller would need to have.
I'm guessing that's probably just a very early version, where the goal is basically just to prove that the components basically work.
Subaru's factory boost control system is the only one that I'm intimately familiar with. It's mostly based on two tables...
There's a table that determines target boost based on RPM and throttle axes.
There's a table that determines PWM duty cycle based on RPM and throttle axes.
There is also a feedback loop to adjust the duty cycle based on the difference between current boost and actual boost.
There are also bunch of other little details, but that gives you a pretty good idea of how it works.
For a street can with enough power, it would be nice to have sets of tables (at least target boost and PWM DC) for each gear, so that regardless of what gear you're in, you could stomp full throttle, and have only as much power as your tires can keep up with.
Not that wheelspin is an issue for very many Subarus... Between AWD and 2.5 liters, it's more of an aspiration than a problem.
Those are kind of annoying on their own because you can slowly build full boost at 1/3 to 1/2 throttle, which makes the throttle response feel really weird.
I have a Hallman in parallel with the electronic boost control system in my Subaru. The electronics fix the part-throttle-full-boost problem, and the manual controller lets me pick whatever boost level I want (provided it's less than what the ECU is set for) so I can hit different parts of the fuel and timing tables for data logging. It's the best of both worlds.
people simply dont know what they're missing. there's a huge hole in the boost control market in between manual controllers and bloated unusable crap like my eboost 2
I used that sloppy controller. and it works pretty good if you have a very complimentary combo (turbo/cam/converter) and an ideal gate orientation. I took my SBE over 1000 wheel with it.
but it can't control spikes, output any safety features or do really anything but control duty cycle. it's basically a remote MBC.
imo the best ebc will be one that can be used by the novice to intermediate guys.
boost by gear is very valuable because yes, you can run more power as wheel speed comes up and you dont overpower the tires.
DC % vs rpm vs throttle angle I can't comment on since honestly a turbo LS makes so much power it's insane. you'd need wheel speed vs vehicle speed to keep from killing yourself
and that is getting into a very very fancy controller
people simply dont know what they're missing. there's a huge hole in the boost control market in between manual controllers and bloated unusable crap like my eboost 2
I used that sloppy controller. and it works pretty good if you have a very complimentary combo (turbo/cam/converter) and an ideal gate orientation. I took my SBE over 1000 wheel with it.
but it can't control spikes, output any safety features or do really anything but control duty cycle. it's basically a remote MBC.
imo the best ebc will be one that can be used by the novice to intermediate guys.
boost by gear is very valuable because yes, you can run more power as wheel speed comes up and you dont overpower the tires.
DC % vs rpm vs throttle angle I can't comment on since honestly a turbo LS makes so much power it's insane. you'd need wheel speed vs vehicle speed to keep from killing yourself
and that is getting into a very very fancy controller
01-13-2019, 02:13 AM
PCM hack for per gear boost control 
Just thinking out loud. My C5 doesn't have forced induction and probably never will, and I'm not sure I want to invest a lot of hard work in something I can't use myself, but, this is an interesting idea. And even if I don't do it myself, maybe we can pave the way for someone else who can do software and actually has forced induction.
haha awesome.