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Old 09-21-2012, 05:03 PM   #1
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Default Strange happenings under (higher) boost

99 MX5, built engine, 9.00:1 pistons, 650cc EV14 injectors, COPs, 4 port water injection, ported head, Factory Mazda 4-2-1 headers, 65mm catless exhaust, Borla, hotside MP62 supercharger, and Reverant edition MSII enhanced ECU.

I used to run about 14 psi on the stock engine.

I got Rev's MSII a while before I built the engine to work the kinks out, so to speak. Everything went well with the MS. (I used to have a 5th injector and all three powercards before then.)

Once I built the engine, lower comp pistons, coupled with extensive head work (+40 CFM per port) naturally yielded less net boost. Power stayed pretty much he same, if not slightly more, due to much improved flow.

So, I decided to up the pulley ratio, for more boost.

I was using a 130/65 mm combo for pulleys. I replaced the crank pulley with a 150 mm one, to get a 2.30 ratio.

My first test drive was epic. 16.5 psi at 6500 rpm, and the car had become seriously fast.

It was at that very point I realized there was a problem. As soon as I exceeded 12-13 psi, Voltage started fluctuating big time. It would hit 12 Volts, and then go up to 18, for no apparent reason. (My Voltage gauge maxes out at 18, so t could be higher)

Such unstable voltage values play havoc with the rest of the car, too. Headlights go off and come back on, the engine starts missing like mad, and the engine obviously loss power...

If I cycle the key, everything returns to normal. Batt Volts read 14.2, car drives nice and smooth, AFRs are nice, till I hit boost.

Once I exceed a magic psi number under boost, the nightmare returns.

* I never had this problem till I replaced pulleys for more boost.
* This problem never happened at 14 psi boost levels before I built the engine.


For the record, I am using an inverter to power the laptop during autotune and logging as I drive. Dimitris was under the impression the inverter could be interfering with TS and causing ECU resets as I drive.

So, I conducted a couple tests today.
No laptop was connected to the MS during any of these tests, so I have no logs.

I took the supercharger belt off and drove the car for about 40 Km, both on the freeway and in city traffic.
The voltage stayed at 13.8 most of the time. It would occasionally go up to 14.1.

I drove the car normally, and revved it up to 6000+ at times. No odd behavior.

Then, I put the SC belt back on.

With the belt on, I again saw 13.8 Volts with normal, off boost driving.

Then, I got on the gas for boost. The car started missing badly, losing power, and the Voltage started fluctuating wildly.
It was bouncing between 12.9 and 18 Volts.

I turned the car off, and then back on again.

This time the Voltage read 14.2. (No more 13.8)

I got on boost again, and the voltage immediately started spiking, and the miss was back big time.

Every time I turned the car off and back on, the voltage would read 14.2.
It would read 14.2 till I got on boost.
As soon as I hit boost, it shoots up to 18...

I honestly do not think this is a laptop related problem, since the laptop was at home during all this.

Has anyone ever experienced any problems like mine?
I did some searching and read about Joe's capacitor woes in an older thread here. Joe was talking about the injectors:

"We're all familiar with the tendency of inductive devices to create a big voltage spike when they are de-energized, right? I mean, that's how ignition coils work. Well, what the heck are fuel injectors, then? They are really big inductive devices, wired in parallel, and connected directly to the MegaSquirt

Think about it- if you want a "hotter" spark out of your coils, you increase the dwell time. Well, how do you get a bigger kickback out of your injectors? Increase the "on" time. And that, for any given RPM, is the primary difference between boost and not-boost. Yes, there is a clamping circuit, but all that power still had to travel through the harness and halfway across the PCA in order to get clamped in the first place. 4000 RPM at 60kPa = ~3ms, but 4000 RPM at 160 kPa = ~9ms. More dwell time!
"

Dimitris does not think this would be the root cause, either..

Again, there was some talk on fuel pump voltage and interference within the MS at one point:

"My MS would get sync loss errors more or less randomly, but much more frequently at high boost (10+ PSI). I tried a thousand different fixes, mostly concentrating on grounding, with no luck.

One day, following a hunch, I rewired the fuel pump so it wasn't powered from the same wire that feeds the Megasquirt. And guess what... for about 3 months now, ZERO sync losses. And that's in spite of my increasing the boost considerably.

My theory is the fuel pump was generating electrical noise that was affecting the Megasquirt ECU. And as boost increases, fuel pressure increases, which causes the pump to draw more power, and my guess is it creates more interference too.
"

According to Dimitris, FP should not cause such symptoms, as well.

I spoke with Dimitris numerous times about this problem. Posting this matter on this forum was his suggestion.

I would very much appreciate if MSII users with similar problems could post their experiences here..
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Old 09-21-2012, 05:19 PM   #2
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TL;DR
You replaced crank pulley? With a smaller one? Isn't that overspinning the alternator? Just guessing.
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Old 09-21-2012, 05:21 PM   #3
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In response to your PM:

The sort of inductive kickback I was describing from the injectors (in the section you quoted from me) has the potential to create all sorts of electronic noise and wreak havoc with delicate sensors, but the kind of symptoms you'd see from this would be things like processor resets, loss of crank sync, noisy analog sensor signals, and so on. By itself, such a phenomenon would never be able to raise up the voltage potential of the vehicle's main power bus by even a few microvolts, much less cause it to jump from 14v to >18v.

Beyond that, I'm afraid I'm at a complete loss. I'm not at all familiar with Rev's custom MS designs, so I have no idea how they are controlling the alternator. If he's generating the alternator field signal in software within the CPU (as opposed to with an analog circuit as done by folks like Abe and JasonC), then my intuitive reaction would be to guess that some piece of data within the CPU is overflowing whenever you exceed some value of (MAP / load / PW / etc) and tripping up the computation which drives the alternator.

But like I said, this is just the most basic, uninformed guess on my part. I am totally clueless as to what's going on between your ECU and your alternator.
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Old 09-21-2012, 05:22 PM   #4
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Quote:
Originally Posted by 18psi View Post
TL;DR
You replaced crank pulley? With a smaller one? Isn't that overspinning the alternator? Just guessing.
His engine has a separate pulley overlay to drive the supercharger which does not affect the alternator, water pump, etc. This is common with MP62 systems.

Beyond that, the voltage output of the alternator is controlled in a closed-loop by sensing the system voltage and adjusting the intensity of the field coil. He could be spinning the alternator at 40,000 RPM and still be able to control the voltage if everything else were working properly.
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Old 09-21-2012, 05:24 PM   #5
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Yes, I replaced the crank pulley, but with a larger one. I took out the 130mm, and installed a 150mm pulley.

And, that pulley is not connected to the alternator, at all.

I also tested the system with the SC belt removed up to about 7000 rpm, and experienced no problems. The problem I described above only happens under high (10+psi) boost.
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Old 09-21-2012, 06:13 PM   #6
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What PSI does your WI pump turn on? Have you tried a run with WI disabled (being mindful of det, of course)?

Also, you might try a run with the alternator belt removed or with the alternator field wire pulled (battery only). That would at least strongly point us at alternator control.
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Old 09-21-2012, 06:29 PM   #7
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Have you reinstalled the old pulley and done 10+psi pulls and is the problem still there?
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Old 09-21-2012, 06:44 PM   #8
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Quote:
Originally Posted by hornetball View Post
Also, you might try a run with the alternator belt removed or with the alternator field wire pulled (battery only). That would at least strongly point us at alternator control.
I can absolutely, 100% guarantee you that if the system voltage is actually jumping from ~14 to >18v, the alternator IS responsible. Nothing else in the entire car can produce enough electrical power to elevate the voltage of the system under load like that.

The question is what's causing the alternator's voltage to jump. And if I were a betting man, I'd say that whatever mechanism inside the ECU is providing the field drive is freaking out.
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Old 09-21-2012, 07:10 PM   #9
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The alternator is controlled by the expansion board. The expansion board on Hakan's car does NOT read boost/vac at all.

The weird thing is that the MS resets in some of the logs Hakan sent me. I have never seen one of my Enhanced MS2s reset so far. I wonder if the expansion board resets as well - that would explain the alternator issue as the board resets, boots, resets again etc.

The reason I asked Hakan to post about this is to see if anyone else is having the same problem. So far no one has contacted me on this issue before, so I want to see if it is an isolated incident or not.
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Old 09-21-2012, 07:36 PM   #10
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Quote:
Originally Posted by Reverant View Post
The alternator is controlled by the expansion board. The expansion board on Hakan's car does NOT read boost/vac at all.
I assumed you were probably producing the alternator field control signal with a microprocessor, just wasn't sure what resources were being shared with what. The fact that it appeared to be related to crossing a certain load threshold made me think overflow, presupposing that you were using the main CPU for this.

But if he's getting processor resets, then all bets are off until that's solved.

I've never used on of your MSes, but I have certainly been in situations where seemingly random processor resets were occurring, and it's always caused by something different. Hell, on my own car I once connected an input pin of the CPU to the same contact of a pressure switch which was also directly driving a relay coil. Every single time I dropped OUT OF boost I got a processor reset. (The switch was looking at pressure in my water-injection line.) I wasn't thinking very clearly when I did that.
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Old 09-21-2012, 08:20 PM   #11
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Quote:
Originally Posted by hornetball View Post
What PSI does your WI pump turn on? Have you tried a run with WI disabled (being mindful of det, of course)?

Also, you might try a run with the alternator belt removed or with the alternator field wire pulled (battery only). That would at least strongly point us at alternator control.
WI comes on at 1 psi or thereabouts, and ramps up to 8 psi. The pump has never created problems with engine management so far.

If I remove the alternator belt, or with the alt out of the equation, there would be no way for me to monitor if there were voltage spikes under boost.
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Old 09-21-2012, 08:22 PM   #12
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Quote:
Originally Posted by shuiend View Post
Have you reinstalled the old pulley and done 10+psi pulls and is the problem still there?
I used to run up to 14 psi with this ECU before I rebuilt the engine, and never had any problems.

The only difference is, I see boost levels I have never seen before with this new pulley (16,5 psi so far).
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Old 09-21-2012, 08:43 PM   #13
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Quote:
Originally Posted by Godless Commie View Post
I used to run up to 14 psi with this ECU before I rebuilt the engine, and never had any problems.

The only difference is, I see boost levels I have never seen before with this new pulley (16,5 psi so far).
Did you ever run 14psi with the ECU and the rebuilt engine? Basically what I am saying is if you switch back to the other pulley that worked fine, does the car still work fine?
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Old 09-21-2012, 08:50 PM   #14
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Quote:
Originally Posted by shuiend View Post
Did you ever run 14psi with the ECU and the rebuilt engine? Basically what I am saying is if you switch back to the other pulley that worked fine, does the car still work fine?
Yes.
I did some 12-13 psi pulls, and it does that voltage spike every time.

I double checked all the grounds, and beefed them up, as well.
The engine ground strap is now a silver coated copper "rope" about as thick as my index finger, for instance.
And, all the other grounds (LC1, ECU, other stuff I can't remember now) run to the back of the cylinder head with 3mm wires, just like before.
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Old 09-21-2012, 08:59 PM   #15
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Just an idea:
I am currently running BKR7Es with the stock 1.1 mm gap.
Could that cause a problem?
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Old 09-21-2012, 09:17 PM   #16
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The answer is simple, at the instant you hit 88mph the flux capacitor overloads your system as you're 1 209 999 400 watts over the stock miata charging capacity, that's why your car shuts down and does the funky thing with the headlights. Also check your blinker fluid, that could also be the problem.
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Old 09-21-2012, 09:55 PM   #17
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Quote:
Originally Posted by triple88a View Post
The answer is simple, at the instant you hit 88mph the flux capacitor overloads your system as you're 1 209 999 400 watts over the stock miata charging capacity, that's why your car shuts down and does the funky thing with the headlights. Also check your blinker fluid, that could also be the problem.
Allrighty there tiger, didn't they tell you not to overdo your glaucoma meds?
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Old 09-22-2012, 12:40 AM   #18
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Glaucoma meds eh? Nope no issues with sight.
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Old 09-22-2012, 11:57 AM   #19
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Would this have anything to do with what I am experiencing guys:

Megasquirt MSEXTRA / MS3EFI • Infrequent Voltage Spikes/Drops, Occasional Engine Cutouts (View topic)

Especially the second post from the last..
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Old 09-22-2012, 06:49 PM   #20
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You know guys, come to think of it, there is a solution to my woes:

I could install an external regulator, modify the dash warning light wiring, and relieve the MS of the alt control duties.

But then again, that would just be curing the symptom rather than the cause itself.

Any ideas?
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