# Megasquirt Overboost Protection or Other Issue?



## fakename (Apr 5, 2012)

New turbo, same boost controller set at 12psi but I'm experiencing what I assume is my overboost protection kicking in at WOT. Engine shuts off, rpms drop and car jerks but comes back and continues doing that same thing until I let off. I've done a data log and my MAP reaches a max of 183 kpa but my overboost is set at 209. I've recently replaced the ignition transistor bip373 on my board and have had issues with it's ground so I'm a little concerned that it's not handling my spark in high boost or something along those lines. I'd like to just raise my overboost and see if that changes anything, but I recognize that it's set where it is for a reason. Any thoughts?

Don't know how to post up my data log. Here's a screenshot of one of the spikes though:


----------



## Prof315 (Jan 5, 2009)

did you hit the spacebar during logging to mark the point in the log? if not overboost protection isn't the issue you are losing power completely to ms. also what version ms and firmware are you using? MS1 is known to reset on hard missfires.


----------



## fakename (Apr 5, 2012)

Thanks Prof!

I started up a thread on msextra forums as well and Matt pointed that out to me too about the resets. I'm slowly starting to understand what the data logs are telling me. Also, the SecL restarts counting at each event.

It's MS1 V3. I did just replace a lot of ignition components (plugs, wires, cap, rotor, coil, igbt) and a new turbo, car drives f***in awesome! But now I've got this issue. First time dealing with misfiring so noob questions to follow: Is that something to be tuned out or should I start to test faulty components? Matt suggested checking grounds which I have and they're all solid without corrosion.


----------



## need_a_VR6 (May 19, 1999)

If you get resets, fix that before you start troubleshooting anything else. Take a look at battery voltage right up until the event, is it normal? Go over power and ground wiring with a fine tooth comb. 

Also link the thread on msextra, I didn't see it yesterday.


----------



## fakename (Apr 5, 2012)

Thanks Paul. Here's the link to my msextra thread.

I posted my data log on that thread, if you can take a look for me that'd b sweet. Batt Voltage is a high of 13.2v and then dips right at or right before the events. I'm not on my computer now so I don't have MLViewer in front of me but I think it dips to 12V. Any signs there? Seems like it should be closer to 14v while driving. I had been troubleshooting an ignition problem before and spent a week of cranking, when I took the battery in to get charged they said it was getting old. Maybe it can't hold enough of a charge?


----------



## need_a_VR6 (May 19, 1999)

I agree with Matt, it's a reset. You can try unplugging the alt exciter wire and see if that helps, if so go through all the power connections to the alt and its grounding. Might have to replace the alt as well.


----------



## fakename (Apr 5, 2012)

Alright, I'll try that. There's only one wire going to alt and power cable, so the wire is the exciter? And that sends voltage to my accessories? I guess I don't totally get what the exciter is doing. And the alt grounds through it's mounting right?

Edit: I could delete what I wrote about the exciter wire in hopes that no one would ever have to know but I'll choose to leave it up there as a sign of humility


----------



## fakename (Apr 5, 2012)

Thanks for the suggestion Paul! I just unplugged the exciter wire from my alt and ran a data log. No resets! I still experienced the same jerking but without my dash tach dropping to zero and back and was able to pull a lot harder before it started too (overboost protection?). I maxed at 220 kpa where my overboost is set to 209 (but my aem boost controller is 12 psi?! Wastegate spring is 5psi?!? Weird!). Datalog and current tune are on this thread. Could you take a look at the datalog and let me know what you think?

So, because my alternator exciter wire was disconnected and I didn't experience the resets, I should check my alt. Start with checking power and ground? Then voltage regulator? Then pull my alt?


----------



## need_a_VR6 (May 19, 1999)

On MS1 it's hard to tell for sure from the logs, but you were over 200kpa for sure and fuel was completely cut. It's safe to say that you're hitting the overboost. I would run off just spring pressure to ease into tuning, or figure out your boost controller ASAP. The logs looked pretty lean on that pull, unless you're running other than an LC1/MTXL type wideband.

For the alt, yes it grounds through the case but any paint on it, the block or block brackets can have a negative influence on grounding.


----------



## fakename (Apr 5, 2012)

I'm just using this AEM wideband. Where on the logs are you seeing my mix? I don't have a pull down option for AFR, there's O2 there but I don't know how those values correspond.


----------



## fakename (Apr 5, 2012)

Pulled my alt and had it tested at autozone, it passed so I cleaned all the connections and put it back in. Took a quick log and had a reset on the first pull. I still don't know why I only see a high of 13.5V while I'm driving. Shouldn't that be closer to 14.5? But even still, last night with the exc. wire disconnected and only running 12.5v or so, I didn't have a reset. Battery this morning was at 12.7v which I think means it's still good. Could a passing alternator still cause noise? I expected there to be a voltage regulator mounted to it but it must be internal, is that right? Would that have been part of their test? I'm getting 12v at the exciter wire with the key 'on.'


----------



## fakename (Apr 5, 2012)

New theory: the new high pressure fuel pump I put in might be drawing too much current and adding noise to... something?!? I'm going to relay it which I was telling myself to do initially but thought I'd be able to get away with it. I'll post back in the next few days when I get a chance to do that. But please!!! If you have other suggestions that I can test in the mean time, post them! Thanks.


----------



## need_a_VR6 (May 19, 1999)

If there is no relay, how is it hooked up now?


----------



## fakename (Apr 5, 2012)

Sorry, there is still the stock relay. I would be wiring a second near the pump drawing power directly from the battery. My buddy's idea is that the stock wires aren't sufficient for drawing the required current for the new pump. Does that seem plausible? As I go into boost, the fuel pump draws more current as fuel pressure rises. Aeromotive recommends wiring a separate relay for just this reason saying that their pump flows 3 times as much current as most stock pumps. Figure it's good to have anyway...


----------



## fakename (Apr 5, 2012)

Hey Paul, I'd still like to know where you're seeing my fuel richness in the data logs. I don't see an option to read AFRs. Do I need a registered copy or something?


----------



## need_a_VR6 (May 19, 1999)

You just need to set one of the drop downs to afr/o2.


----------



## fakename (Apr 5, 2012)

Thanks. In the drop down menu I only had an O2 option but didn't know what the numbers meant, max 4.7 min .58? In the Calculated Fields menu there's an option for an AEM gauge. I'm all set now, thanks! I'll post back after I relay my fuel pump in hopes that helps with my resets.


----------



## fakename (Apr 5, 2012)

Update: I relayed my fuel pump and I replaced my alternator. I upgraded from a 90A to a 120A as well. I'm still having resets though...

Matt on the MS forum recommended awhile ago that I ground all my MS grounds to the head instead of the body which is where they are grounded now, and have been grounded for years. Haven't tried this yet, I just don't think that it'll make a difference. *Edit:* Matt's a smart guy and I'm not so I think I'll give it a shot. I was reading this and it makes sense. Maybe the fuel pump is effecting my chassis ground?

So just to recap: ECU resets in boost, when I unplug the exciter wire it doesn't reset, replaced alternator and now I'm back to getting good voltage while driving again but I'm still getting resets under boost.


----------



## need_a_VR6 (May 19, 1999)

I didnt catch the grounds. Definitely move them.


----------



## fakename (Apr 5, 2012)

Well you guys were absolutely right! Moved my grounds to the head and I'm not getting any more resets and my headlights are no longer stalling my engine either! Life is good. Now for that new turbo tune.

So, if I understand this correctly, it could be that sharing the chassis ground with my new fuel pump was adding noise to my ms? and using the engine as a ground only shares it with sensors and whatnot which aren't as noisey? I still wish I knew why pulling my exciter wire would keep it from resetting. If I knew that, I think I could feel completely accomplished, but now I will always feel slightly defeated...

Thanks again Paul for all your help, I really appreciate it :thumbup::beer:

And for those who stumble on this thread who have similar issues, here are some other posts that had ideas I was going to try:

http://www.msextra.com/forums/viewtopic.php?f=4&t=23223
http://www.msextra.com/forums/viewtopic.php?p=149614#149614
http://www.msextra.com/forums/viewtopic.php?f=94&t=23749


----------



## fakename (Apr 5, 2012)

Update for those with similar issues:

Well, I started getting resets again when I would turn on my headlights and when I would go into boost so I soldered the capacitors as suggested in the links above. Test drive and log has shown to be successful with the exception of one random reset but not when I turned on my headlights or when I went into boost (and pulled hard!) but I'll confirm within the next few days.

If this is my last post here, assume that all is well, or that I died but that's unlikely. Hope these caps are as good a mod as everyone says they are, this is my last resort. Thanks again to all those who helped me in this thread.


----------

