Raise Boost while retaining ECU oversight

[shinzon]

Firstly, I would have posted this in a more appropriate forum, but it seems I can't post elsewhere even though I have been a member of dsmtuners for nearly a year.

I was reading the vfaq page describing how the boost control solenoid functions and I noticed that the ECU was able to close the solenoid if it is detecting excessive knock, thus lowering boost to 7-8 psi and protecting the engine.

Now it seems the usual way to raise the boost level is to completely eliminate the BCS and in its place put a manually controlled bleeder valve. This seems dangerous as you are removing a critical engine protection device. Now I guess it could be argued that you should tune the car so that knocking is minimized, but it would be nice to have a failsafe in case you get a bad tank of gas or something and not realize until you're doing a WOT run. Besides, better to be safe than sorry, right?

It seems to me the best solution would be to modify the stock BSC so that it does not bleed off a set amount of pressure but completely lets it pass through and place it inline before the manual boost controller (so that is flows from Pressure Source > Modified BCS > MBC > Wastegate actuator). This should allow the ECU to still open and close the solenoid normally when it detects knock while allowing the manual boost controller to take care of bleeding off the necessary air to fool the wastegate actuator into opening later when the solenoid is in the normal open position. If its not possible to modify the BCS as necessary you would need to wire in a replacement aftermarket electrically controlled air valve while still fooling the ECU into thinking the BCS is connected so that you avoid a check engine light.

Does anyone have any experience into doing a modification like this? Does someone already sell something which will preform this function? Feel free to poke holes in my idea, its just something I've had rolling around in my head as I thinking about increasing horsepower while still maintaining the overall fault tolerance and reliability that would be in place had the Mitsubishi Engineers designed our cars with the set-ups we're putting on them these days.

 

[95GSXBLUR]

I have not modified my stock BCS, however, If you're running an electronic boost controller, you can set limits to you peak boost, if you exceed that, it will automatically lower boost to an amount that YOU set.

The ECU when is sees knock will pull timing in accordance to the amount of knock you're getting. If you're using the factory ECU as well, you will hit fuel cut if it sees excessive boost/knock/timing retard.

DSMLINK or other tuning devices allow you to tune for the sort. I believe if you have AEM EMS you can use a 3 bar sensor and tune for safety and lower boost that way in conjunction with an EBC.

If you have other warning devices, logger, EGT, Wideband, etc... You don't really need to retain the factory BCS. it'll more than likely just hinder the operation. I think your idea is a good one... just excessive because of the other tuning measures and warning devices out there.

Since you don't have mods in your profile, nor have you posted more than once... this is more than likely the reason that you cannot post anywhere other than the NOOB section regardless of what you actually know.

 

[Quasimondo]

An alternate way to do this would be to use the BCS as a bypass, but this would require using a solenoid that is normally closed, versus the normally open one used in the BCS. In it's normally closed position, boost will be controlled by the MBC. If you encounter an excessive knock situation where reduced timing doesn't help, the solenoid would then be opened, bypassing the MBC and reducing boost to wastegate levels. That way, there's no need to reconfigure the ECU or anything like that.