mx5cartalk.com

Hi guys,

At this stage i'm fitting a MBC and thought it might be good to add some information which directly relates to tuning in general and the drawbacks of MBCs. It's not mentioned/summarised well in the searches I've done specifically relating to MX5s and it may also explain some of the issues had in terms of boost spiking/fluctuation when you are at the same stage as me (and why you needed to get rid of the stock boost control solenoid).

The best article I have found is:
http://blog.perrinperformance.com/boost ... explained/ and
http://blogperrinperformance.com/boost- ... ed-part-2/

In short, the boost solenoid does not operate in a simple fashion ie long time spans of open/closed. It is part of the wider control rationale programmed into the stock ECU and is likely quite comprehensive/complex. It operates in conjunction with other systems (fuel, ignition etc) to maintain driveability and boost levels.
The main drawback of an MBC is that it stuffs up some of the control loop functions - ie Tune details including fuel mapping, gear/speed/pedal position ('3D') based boost mapping, idle speed mapping....

As an example, your aftermarket ECU (and the stock ECU) will modify boost delivery based on ambient temperatures/humidity, throttle position etc to deliver a consistent and desirable amount of power and drivability. As mentioned in the article you don't necessarily want full boost (power spike) to arrive at mid throttle position in a sudden fashion - it'll behave like an RS500 escort and be 'unsettling' to drive.
Putting in an MBC is likely to cause issues such as this and have an inherent inability to cater to situational factors so you'll have different boost levels on different days/situations.
Those 'tune details' mentioned are where you sort the wheat from the chaff in terms of good and bad tuners. Note that Mazda engineers are unlikely to be stupid and have disproportionate resources to be able to fine tune these things which may go some way to explaining why aftermarket tuners struggle to replicate drivability etc.

Note; this is also why you have to take the solenoid out of the equation when you add the MBC. The MBC doesn't simply add a couple of PSI to the wastegate actuator pressure when you have the solenoid in place. It will in an initial short spike, but then the solenoid (etc) will try to compensate for the boost spike and bring it back into check (by the ECU increasing it's frequency signal).

I do wonder if you could curb the feed signal to the ECU by 3 PSI or whatever and match it to a 3 PSI MBC increase to the wastegate and increase boost with nominally factory driveability..... but I digress.

Thought i'd share a good article. Basically, the MBC/EBC is a bandaid solution for a spike in power and is probably not the best for drivability. It is cheap fun, but certainly not a substitute for an ECU upgrade/re-tune.

Certainly the above is true.

Aftermarket ECUs with the right options can achieve better than the OEM chooses to achieve, probably mostly due to budget and emissions and intentionally making lower priced models perform noticeably lower than higher priced models (MX5 SE/SP vs RX7, XR6 Turbo VS XR8 etc).

The vast majority of the cars I send out are reportedly better than OEM in pretty well every way right down to emissions and economy and especially driveability/smoothness.

Dann

Regarding the Standard Boost control solenoid and MBC setup. I just did this recently as well.
I also had trouble finding good information on this for a SE/Mazdaspeed searching through Google and Forums. I relied more on pictures of engine bays.
The best bit of information I did find is apparently you get a fault code if you unplug the Solenoid.
I left mine plugged in and its still bolted to the Cam cover. Probably should try unplugging it to see if I do get a fault code.
I blocked the input port to the solenoid and left the output port connected to the air intake pipe.
I got rid of the factory T-Piece between the Throttle body port and Wastegate and replaced all the hose with 2 new pieces with the MBC in the middle of it in an accessible location.

Please someone do tell if this is set up all wrong on a SE for a MBC.

It does spike initially by about 0.5PSI so I set it at just under 10PSI to avoid hitting the 11PSI fuel cut.
I was expecting this from the general information I read about MBC's but for $50 for the controller, a bit of hose and plumbing what can one expect.
I do get the initial spike in power when this happens but I am more than happy to have it as I much prefer the quicker response going from no throttle to throttle. That is where the car was garbage before changing this.
I have had no issues running it with this setup on road or track.

As a side note I was only making about 6.75PSI before putting the MBC in. I gather Wastegate Actuator Springs lose tension overtime as it should be 7.5PSI???

NitroDann wrote:Certainly the above is true.

Aftermarket ECUs with the right options can achieve better than the OEM chooses to achieve, probably mostly due to budget and emissions and intentionally making lower priced models perform noticeably lower than higher priced models (MX5 SE/SP vs RX7, XR6 Turbo VS XR8 etc).

The vast majority of the cars I send out are reportedly better than OEM in pretty well every way right down to emissions and economy and especially driveability/smoothness.

Dann

Hey Dann,

Everyone on this forum definitely endorses your work. Like I said, the difference between good and bad tuners is in the detail.
Interesting that most of the information around just doesn't cover the drawbacks of MBC or really answer 'why' you are doing one thing or another.

What preferences do you have for ECU on an SE? I've used Motec and Haltech in the past on different cars - the latter seemed to offer more comprehensive options.
[PM me a rough price if you can - I've absorbed a heap of cash preparing/entering Targa High Country this year so i'll be leaving the ECU/injectors until after Christmas. All other supporting mods are in and I understand you're within easy driving distance of Canberra]

Cheers,

Rob

Luke wrote:Regarding the Standard Boost control solenoid and MBC setup. I just did this recently as well.
I also had trouble finding good information on this for a SE/Mazdaspeed searching through Google and Forums. I relied more on pictures of engine bays.
The best bit of information I did find is apparently you get a fault code if you unplug the Solenoid.
I left mine plugged in and its still bolted to the Cam cover. Probably should try unplugging it to see if I do get a fault code.
I blocked the input port to the solenoid and left the output port connected to the air intake pipe.
I got rid of the factory T-Piece between the Throttle body port and Wastegate and replaced all the hose with 2 new pieces with the MBC in the middle of it in an accessible location.

Please someone do tell if this is set up all wrong on a SE for a MBC.

It does spike initially by about 0.5PSI so I set it at just under 10PSI to avoid hitting the 11PSI fuel cut.
I was expecting this from the general information I read about MBC's but for $50 for the controller, a bit of hose and plumbing what can one expect.
I do get the initial spike in power when this happens but I am more than happy to have it as I much prefer the quicker response going from no throttle to throttle. That is where the car was garbage before changing this.
I have had no issues running it with this setup on road or track.

As a side note I was only making about 6.75PSI before putting the MBC in. I gather Wastegate Actuator Springs lose tension overtime as it should be 7.5PSI???

Hey Luke,

Leave the solenoid as you have it. You will get a fault code if you remove it (unless you put in a resistor).
0.5PSI boost spike is probably not an issue. There are a number of reasons why this would occur, but it is minor enough that it probably isn't worth chasing if you're not hitting boost cut in any conditions.

Springs don't really lose tension over time (without delving into it, spring rates and permissible deflection is set within the elastic region of the material from which they are made). More likely the diaphragm or actuator arm get tired/dirty, but I wouldn't worry about that with the setup you have. It could completely be fine and your boost gauge is not 100% accurate.
If it's generating boost smoothly and holding it then all is well.

Rob

You can get rid of the oem ebc solenoid by placing a 47ohm 0.5watt resistor across the electrical plug.

Take a look down this page on my thread and shows what to do...http://mx5cartalk.com/forum/viewtopic.php?f=57&t=69985&start=30

You may want to read this as well regarding leaving the solenoid in place ... http://www.mazda-speed.com/forum2/index.php/topic,21020.0.html

Apparently, once on an aftermarket ECU you can use the stock wiring to control a MAC valve solenoid for EBC. Which is cool. You retain the stock wiring, no harness change just ensure the plumbing of the vacuum lines are sorted and enable the ECU to control boost (there may be more steps in there regards to tuning etc).

ManiacLachy wrote:Apparently, once on an aftermarket ECU you can use the stock wiring to control a MAC valve solenoid for EBC. Which is cool. You retain the stock wiring, no harness change just ensure the plumbing of the vacuum lines are sorted and enable the ECU to control boost (there may be more steps in there regards to tuning etc).

No doubt that it would be possible/neat. If you go to an aftermarket ECU (and more boost) i'd suggest you may need to go to a new boost solenoid - Dann would know from experience whether the stock one is capable of delivering appropriate frequency response and flow to control boost at higher levels.