I think Junk meant this with the diode:

A diode has a constant voltage* drop across it, of about 0.6V-0.7V. By adding a diode from the Alt output into the alternator sense circuit, when the alternator is regulating at 13.5V (after the diode), it will really be putting out 14.1V (before the diode).... 14.1V output - 0.6V = 13.5V. This extra voltage will push more current through your electric fuel pump.

* The diode voltage drop is not dependent on current flow, at least for what we are discussing here. Whereas using a resistor, the voltage "lost" across the resister is dependent on how much current is flowing, which is dependent on the resistor itself, along with the rest of the circuit's resistance.

FYI: I found the radio cuts out at 16V... when the voltage regulator fails high.

 

That is good no DC-DC converter.
The alternator tries to achieve 14.8 volts approx at the Voltage sense terminal (little red wire in the white connector). This wire is tied directly to the output of the alternator (big red wire on back of alternator). If you disconnect the Vsens wire in the white connector AND the battery terminal output red wire. Add new wire from battery output terminal to Vsens terminal with 2 diodes in series with neg at Vsens. The 2 diodes that each have .7 volts drop for a total of 1.4 volts will have 14.8 at Vsens, and have 14.8 + 1.4 = 16.2V at the alternator battery output terminal. Connect your fuel pump to the 16.2V output terminal, connect the orig battery output WIRE to the 14.8 point to power the rest of the vehicle.
Make sure the diodes can handle the alternator output. These diodes are BIG.

Above is how to raise the voltage. Do I recommend doing it? NO.

Problems like these are difficult to solve.

The way I would try to solve it is:
1) Install fuel press gauge viewable in vehicle
2) Buy ebay $13 USB logic analyzer and buffer board to read BOTH the injector BPW signal and the fuel pump voltage.

The buffer board (and voltage divider) is to reduce the fuel pump volts to logic level volts. Also, the injector BPW rings so you need to reduce and clamp using the buffer board. Just a regular OP AMP buffer board will do.

You need the tools above to determine why the failure occurs.
The logic analyzer can be used for lots of other stuff later on.

Even better if you know someone with a portable O'scope. Just connect directly to injector BPW and fuel pump volts. These are expensive, but easier to use.

EDIT: Maybe just get ebay 2 channel $95 USB oscope and some 10x probes. That tool says max input is +/-5V. A 10x probe would allow 50Vpk input. Fine for the fuel pump volts. Not sure on the Injector BPW ringing. Maybe put a 2x atten on the front of the 10x probe for injector BPW.

 

YES
Put the vehicle power on the neg/low side of the diode to give it the orig voltage level, not the higher boosted level.

 

i run my a1000 off my rear mounted battery. i have a relay back there beside the battery that the computer controls, and some #8 wire from the battery to the relay to the pump. battery is grounded to the rear chassis, and the pump is also grounded back there. i have a safety shutoff switch on the negative side of the battery. everything works fine. i went extra large on all my battery cable though (1/0), to keep voltage drop to a minimum.
my alternator is a 100 amp powermaster racing alt.

 

Yes, in the post just before the one I'm quoting now I mentioned the gauge size from the alternator to the back of the battery, as that is no doubt the issue. Had to literally force my buddy Paul to watch the pressure test video (which still isn't posted yet) because he hates third gens, but when he seen it, he underlined it, it is definitely voltage drop, it is not wired correctly at all. Most of the guys were blaming his timing and tune all the way up to that point, Steve is really lucky he didn't blow up his freaking engine. Get to work Steve...

 

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u know u could adjust the batt v vs pw table to compensate for this ,atleast then it wont lean out so bad while testing that u wont risk hurting the engine until u can track down the source of the voltage drop

 

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You were focusing on voltage in that video which is good, but you never said how much boost you were running in that video. The problem seemed to occur close to 20-psi of boost pressure as more fuel volume was needed, not to mention on a prepped track where the load is tremendous because you can hook. How much boost in those runs in that video...?

 

how much fuel was in the tank when you had the 16 afr, and how much fuel was in the tank during your last vid?
also this may have already been mentioned, but im wondering if you have a loose vacuum hose going to the fpr.... maybe there is a boost leak causing the 1:1 raise in pressure getting skewed?

 

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dont give up on it, i know its tempting. i know the math comes out to suggest the factory lines should be good to this point, but maybe they just arent due to misc. kinks and bends? the fuel system that was in my car before i got it was a #8 running up front and the original feed was being used as a return. it was a twin turbo 350 with a tpi intake and i believe it made somewhere around 450 at the wheels. it was later swapped to a miniram.

 

When I was making preliminary tests with mine at that boost level, I found that the air/fuel would lean out similarly because the acceleration enrichment was coming in too late, and the ECM played catch up. Took care of that issue, but then noticed that my boost gauge line was leaking at that level which caused a lower reading on the gauge, but in actuality higher pressure in the cylinder which obviously wasn't tuned for and it would go lean. Took care of that and never had that issue again. The problem with yours seems intermittent. How are your grounds in your wiring, everything secure? How old is that alternator by the way, same once since you started? Might be failing with excessive engine heat...

 

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im jealous that u can actually goto the track this time of year ,

i think the track down at las vegas is still open but thats a haul for me

 

I'm jealous too, we may have to move further south. It's supposed to be -8 tomorrow here in ohio with a good amount of snow!

 

Hey, few questions for you:
1)Where's your engine ground hooked up to? Do you have an extra ground straight off the alternator to your battery?
2)Do you ever see diming of your lights, erratic gauges or the likes when this is happening?
3)I don't think your alternator looks too close to your piping, have you ever tried to get something like a large can and cut it up and stick it on as a heat shield? It looks well wrapped, but at the very least perhaps you should check your alternator windings for signs of overheating. It looks as if they'd be hard to see from the pics up though.
4)Have you tried making a pass somewhere else, and stopping suddenly and parking as if you were at the track? It seems like in a lot of the videos you have you just "accelerate and drive off" versus something like the track which may have you in more of a heat soak situation.
5)do you ever have weird starting issues or have you ever had weird starting issues?
6)do your E-fans kick on during a run?

Few odd questions I know, but the alternator theory is interesting. It's one that would be best measured first though. The reason why I think it's electrical is this. Resistance is something that's temperature dependent. The amount of power dissipated (read:heat) by a resistor is E^2/R where E is the voltage drop and R is the resistance. So lets say we start out with a very simple system, 10A current with 1V drop. Since Ohm's Law dictates that as E=IR we end up with a resistance of 1/10 ohm and a power loss of 1^2/(1/10)=10 watts. After a while this heats up, and gains say 50% so you end up with E=10A*.15 ohm which is a voltage drop of 1.5 volts. We then determine that the power loss is 1.5^2/.15=15W. As you go along more and more this process continues, and eventually you end up where the pump can't sustain its voltage. It's a system that makes its self progressively worse as time goes on.

 

Yeah they released the Midnight of Mayhem schedule and the first event is 24 Jan. They take a small hiatus Dec and Jan

 

I've got a couple of questions not related to your current issue and maybe if I go through all the threads I'd find them but oh well!

What type of display is that you are using for AFR and those 3 others? I haven't seen a round style display like that. I'm assuming that interfaces with your megasquirt? You're still running a MS, right?

Are you running drag radials in that last video of your runs way down in Mexico? You must be, seems to hook pretty well.

And are you still running your 700r4 with Dana's kit? Looks solid!

 

Would be nice to have a 2 channel cheapy oscope logging Injector BPWs and pump voltage during the testing.

 

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Just read through this entire thread. Phew, over an hour! Ha you've been through a lot if troubleshooting lately!
Let me try to recap and let me know if I've screwed any of this up.
So you've still got the fueling issue. And when the fueling issue is not showing it's ugly head, it's still not much faster than the old setup.
With boost numbers in the teens, you're only trapping around 94. Your car is full stock weight plus the turbo stuff.
Your running a 350 with ZZ3 aluminum heads, TPI, and a 224 @.050 114LSA cam.

Just as I got to the last post, I was thinking there was one thing not talked about much - exhaust. What are you running after the turbo? Is that a 3" downpipe and does it go into stock-ish sized exhaust after that?

As a reference, I looked up my old time slips and I was trapping around 96-97mph with 10psi (highest I've ran). I'd say our engines are fairly similar headwise. My cam is quite a bit smaller at 212/222 112LSA, and I'm running lower boost. At 7 psi, it trapped 94.
The big differences I can think of that are obvious are intake manifold and exhaust. We've got the exact same intercooler, and very similar hot side setups. I'm running a performer rpm dual plane and a single 4" exhaust all the way to the bumper with a muffler. Plus my turbo is probably not the best match being from a diesel bus.
I would expect your setup to be crazy at the higher boost levels that you are running.
Are you still running a cat?

 

How do you have the MS wired up for ignition? I have 10* initial, and full ECM control over running (and cranking advance). I have my 'cranking rpm' set to like 300, and 25 degrees cranking advance. There is also a number of settings you can manipulate for enrichment - both while cranking, and key on enrichment.

-- Joe

 

Probably a stupid question, but on the megasquirt, is your injector pwm limiting set to 100%? I'm assuming your injectors are high impedance. On my other car which has a mega squirt I didn't have it set to 100% with the stock injectors on a stock engine and it would lean out no matter how high I set the VE table values.

 

i have mine wired for ecm control even while cranking 10* initial and set my cranking rm to 450 , i dont bump timing till 650 rpm though. though i have a really picky starter for some reason anything more then 14* while cranking will cause hard starts or the starter to grind

 

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Not sure if exhaust is your issue but certainly larger wont hurt

I make 505whp per bank thru a stalled th400 thru 3" pipe and 2 mufflers per side still makes power with each psi increase so while there is backpressure as i can see the pipes being thrown back againsts the hangers, its still overcoming that and making power. If there was a restriction i would have thought boost increases would not gain as much power but it stayed constant at 30-32 hp per psi

If i dump the dp's below motor i expect 60 whp gain at the 1000 hp mark, may be it will be more maybe less. Hard to say but at 450's whp, i can see 20-30 tops. I could be wrong.

 

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I cannot imagine how frustrated you are, your going in circles checking all the right things and come up empty every time!

Excuse me if this has already been done but you have testest so much I cannot remember Have you verified your timing with a timing light, for all different RPMS and boost levels? To do that I took my timing light, hooked it up, and had someone rev up the engine and watch the computer screen, shouting to me what the commanded (table) timing was as I watched with the timing light. This was of course only at low MAP values. For the higher map values I pulled a bunch of fuel so the engine wouldn't die, and hooked a regulated compressed air line to the MAP sensor so I could simulate boost while having someone again rev the engine while I held the timing light.

I later found out my issue was crossed plug wires

Even though your having a fuel pressure issue, it does have good fuel pressure sometimes so there is something else holding you back (power/E.T.wise). You have tripple checked all the mechanicals so I feel like it is a control issue. I'm sure you have checked, but maybe you have table somewhere thats pulling timing or something weird, are you sure it's not in 6 cylinder mode or something? I know it sounds stupid but like I said, I had crossed plug wires for weeks while chasing down all kinds of other "problems" I thought I had

 

Could be a regulator issue that occassionally malfunctions or something weird. Hard to say

But i think a good 2-3 hr flogging on a dyno would be money well spent. Hotlap it to really test the tune, and put some heat into the system.
Monitor temps of everything, verify timing on live running motor, etc. record fuel pressure and voltage at various areas.

Get real data on power vs boost, timing and air fuel. Find what it wants. Then remember to back off 2 deg or so and add 5-8% fuel back in after leaving dyno for correct street tune

 

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I dont think the wastegate opening explains why its not making the big power you'd expect at 18 psi. It still seeing boost and should be making numbers. Only thing wastegate opening explains is lack of boost increase over spring ratio. But most controllers you can almost double spring pressure for boost. Meaning 15 psi gate spring should beable to get near 30. But not always the case. Theres only so much a manifold referenced system can do. Co2 kit is needed for this ultimate control

If bigger gate and more spring dont work then turbine is likely to small or even compressor. A good 350 i would think could use a 72-76 mm

 

Well it's a computer, garbage in = garbage out, I would use a second method to verify just in case, and it's free to check.

What size and AR is your turbine? I had zero issue hitting 21+lbs of boost on a very simlilar engine with a T4 flange, 68mm wheel, .96 AR

 

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Ok i understand that. If you still have backpressure then precision is wrong and it is the turbo

To be honest for mild boost that turbo seems fine but for high boost i would have a much bigger turbine and alittle bigger comp wheel. 70's mm comp wheel and matching turbine wheel imo.

Now restrictive downpipe can lead to higher manifold pressure as well so i would try open exhaust as short as you can disconnect it. I saw 2 psi less boost on same gate springs from single 4" to dual 3" on my car

 

do u know anyone with a turbo with a larger turbine side u could borrow for a couple test runs with

if u were somewhat nearby id lend u a t6 76mm turbo with a t4 to t6 adapter flange , id also lend u my ms unit so u could eliminate ur unit as having something wrong with it

 

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measure the back presure versus boost level first , if its high then its worth the work to test, if its between 1-1 to to 1-1.6/7 it should be fine , but if its in the 1-2.0 or better range id would go threw the hassel of mounting up the 76


anyone who can lend u a ms unit so u can eliminate urs as something goofy going on with it ?

 

I'll ship you my tc76 to test but it's probably cheaper to buy a mp unit lol

 

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Well that's probably a good sign that it's leaner. As someone said before, that's a sign you should be making more power (in theory anyways).

So your boost gauge is connected to the intake tubing before the throttlebody? Is that always how you've had it? And maybe I missed it but what do you mean by having T's in the line? Are they open to leak boost to atmosphere? Any type of manual boost controller?

 

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