Losing battery voltage at higher rpm

[mell00510]

72, ka24de turbo, car is breaking up at higher rpm. I have been diagnosising w/ my fsm and different software. Long story short this has become one of the last possible suspects... I truly have gone thru procedures and have multiple parts to compare different values on the bench. Here is a small snap shot of me data logging, going up a slight hill at full throttle-
1st is time, entry #, rpm, temp (c), battery voltage, and tps 4.1 volt (which IMO is a little low, but was told from pretty solid source 4v will tell ecu WOT...) letting off at 5300rpm because it doesn't feel right and wideband is reading 10.2, again little rich for me....

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[finn]

Do you have an S13 ecu? No codes? Voltage increases with speed so interesting to have that issue

[510rob]

Could you define "breaking up" a bit more concisely?

What is the heat range of the plugs and what are their gaps currently set to?

If you take the battery out and give it a 100% charge, then put it back in and run the car for a few quick pulls with that 100% charge, does that cure the problem?

Only a few things can alter the electrical system's operating voltage: the total electrical load on the system, the battery's present state of charge, and the voltage regulator in the alternator, which is also somewhat of a consequent of the particular/peculiar wiring of each swap/installation.

[mell00510]

-I run an s13 ecu, the only code I can pull is a code 14 (vss) after 35 key cycles it appears.
-The breaking up, engine noise after about 5200rpm, I would say lack of spark... it breaks up like a poorly timed engine, would be best way to describe it. I've pushed it hard enough to run out the fuel system and this feels a little different. I run a heat level 6 and gap plugs to .28, this was a great combo for 10,000+ miles. and all of the ignition pieces other then the distributor and coil have been replaced. I put the battery on the charger this am so i will go do a few pulls this evening. The electrical system has been completely replaced and updated w/ highend/quality products. (Stinger brand from head to toe including the battery, wire, and even terminals) Thx Finn and Rob! And Rob I'm still writing ya in on the 2016 ballot!

[bertvorgon]

I hope you meant .028, because .280 would be an issue.... I run .028 on my 10:1 and 16 PSI boost, all good to 8,000 RPM

[mell00510]

HAHAHAHA! Yes Bert is correct .028! 1/4" gap would probably be a problem
I usually run around 18-20psi, and car ran beautiful for years. After a long weekend at the track she hasn't been quite right

[510rob]

A few comments...

• KA24DE turbo
• car is breaking up at higher rpm
• letting off at 5300rpm because it doesn't feel right and wideband is reading 10.2, again little rich for me
• The breaking up, engine noise after about 5200rpm, I would say lack of spark...
• it breaks up like a poorly timed engine, would be best way to describe it.
• I run a heat level 6 and gap plugs to 0.028", this was a great combo for 10,000+ miles.
• all of the ignition pieces other then the distributor and coil have been replaced.
• The electrical system has been completely replaced and updated w/ highend/quality products.
• I usually run around 18-20psi, and car ran beautiful for years.
• After a long weekend at the track she hasn't been quite right

(foreshadowing - did you happen to change the plugs after the track day, or are you still using the ones that had the shit kicked out of them all day long?)

You say that it feels like a lack of spark and like a poorly timed engine. You are describing what sounds to me like an ignition issue, but you are chasing an electrical issue.

I think your #6 plugs are too hot to run for a track day; sustained high load = sustained high temps within the combustion space = sustained thermal loading of all parts exposed to combustion. You may have caused a "plug-related issue" at that track day, by overheating one or more of the spark plugs, which can cause fracturing/cracking of their ceramic housings...

A basic KA24DE normally puts out 150ish HP and uses #5 plugs.

You are putting 18-20psi through your KA24DE, which probably gets you up around the 250HP-300HP range, but you are using #6 plugs that are only one heat range colder.

Spark plug heat range is bounded by two simple criteria. They have to stay hotter than the self-cleaning temp, and lower than the pre-ignition temp. The happy valley is about 500-950°C (temps according to Denso). The caveat about the heat range is that once the plugs go over the pre-ignition temp, guess what happens to ignition timing - it goes out the window and then you beat the shit out of the ring lands and the bearings. But also, if the ceramic bodies become overheated, the ceramic can start to fail. I don't imagine that the combo of high temps and exposure to pressure spikes caused by pre-ignition is a very helpful mix either. Thermally stressed parts can sometimes seem to work ok when not being stressed, but can then exhibit wonky phantom issues when re-exposed to thermal stress.

ref - http://www.globaldenso.com/en/products/ ... f/P038.pdf

Based on all of that and in the interest of thorough troubleshooting, I would suggest that you try a [known-to-be-good] set of spark plugs - if you have the ones that came out of the stock engine (and that engine ran ok), then pop those in for a run around the block. A few quick pulls with this change will quickly reveal whether or not your set of "track day plugs" are introducing your wonky timing issues...

I hope Keith will chime in with some of his experiences related to [plug heat range and boost levels] versus [event duration], etc...

I'd say run at least #7 or #8 plugs at a track day, just for the track day, then swap your regular #6 plugs in for the rest of the driving shenanigans.

ref - http://www.ngksparkplugs.com/techinfo/s ... berkey.pdf

What I'd really like to see are pictures of the 4 track day plugs, with enough light to see right to their bases. Also, get an illuminated 10x viewer and look at the tips for small shiny balls of aluminum to see if it is ever getting lean and in-chamber combustion temps are getting much over the melty 1400°F threshold.

I'm rambling - this post is too long. I'm probably wrong anyway.

[bertvorgon]

No Rambling, I did not notice the "6" heat range.

I would for track days at least have an 8 if available. Not sure of your compression of course, but I see well into 1,300+f when fully on it, and have been to 1,600 at times. The plug would be beyond nuclear with a 6 in there.

Rob is right, that plug is likely glass down the side.

[mell00510]

I have replaced the plugs, the cap , rotor, and wires. I can try and snap a shot of the plugs although they have been out of the engine for sometime and i've noticed in the past that used plugs pulled from an engine slowly discolor/rust. I agree that it sounds like an ignition problem but I can't find any issues w/ it. My timing looks correct, coil tested good (not much testing to do there), and everything looks correct on my data logging so not real sure. I'll be honest- the voltage drop is the only thing I see happening

I see your point and the voltage is a long shot, but it's all I got! Thanks again guys appreciate the help

[mell00510]

And as far as hp... Your guess is probably accurate w/ how it's running, when running correct these were my results

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[bertvorgon]

This is one of my plugs after high speed running. This plug is one heat range too hot, at least for me, as it is just starting to glaze. NO little silver balls though, so that is good!

I really do try to tailor my plugs to what I am doing, as old fashioned as that may be. Racing requires a relatively cold plug, specifically so it is not an initiator of detonation. That is a lot of boost, what fuel are you running?

And for what it is worth, I run a "9" when I ran track days, and I run a "9" if we are going to be canyon carving on our long highway trips.

Just for giggles, and I know this is due to the Avgas being a lot cleaner, here is a pic of my tail pipe after a run.

Just some thoughts at any rate.

[510rob]

I have replaced the plugs, the cap , rotor, and wires. I can try and snap a shot of the plugs although they have been out of the engine for sometime and i've noticed in the past that used plugs pulled from an engine slowly discolor/rust. I agree that it sounds like an ignition problem but I can't find any issues w/ it. My timing looks correct, coil tested good (not much testing to do there), and everything looks correct on my data logging so not real sure. I'll be honest- the voltage drop is the only thing I see happening

I see your point and the voltage is a long shot, but it's all I got! Thanks again guys appreciate the help

Hey, does that mean your car has the mythical "400WHP daily, yo!" rating? That's a crazy amount of HP! I assume you don't have stock internals.

Problems like this are the worst! I can see why you are wanting to confirm the change in voltage...

So even after replacing all of the ignition parts you still get no love.

When you say the timing looks good, does that mean you confirmed it with a timing light, or does that mean the computer settings are the numbers they should be? I don't really know how the timing could have gone out of wack, but I'm just being pedantically consistent.

How did you test the coil? Did you use a megger to check its high voltage insulation properties, or a standard ohmmeter to confirm its DC ratings, or both?

Can I say it on your behalf? "F%&K!!!!!!!!!!!"

Out of curiosity, what is the longest period of time that you have ever sustained full throttle operation on boost? Was that this weekend? What kind of fuel do you normally run? What fuel did you run at the track day?

Because it sounds like you rewired the car's primary power system, where did you attach the alternator's voltage reference line? Is that connection still good and secure? (shooting in the dark at this point).

[mell00510]

It was built as a street car and was tuned on 91 pump. The few track visits and Saturday night fun I might throw a few gallons of 108 on top for the extra heat, keep the detonation away a little longer, and who doesn't love that smell?!?

The timing has been verified in 4 ways, 2 timing lights (mine being the preferred, w/ timing adjusted on gun and finding tdc, per fsm- unplug tps, blahblahblah), through the software I use on my laptop, and I also stopped by the nissan dealer and had a buddy check it w/ the consultII. He also set my air idle !bonus!

The coil got tested per fsm- which isn't much-visual, and ohm test. Also checked wiring to ecu, why not?!? I would need an oscilloscope, which I can't seem to find anyone w/ one... And I work at a local dealer, and have family that owns an auto repair business. So a $60 coil is quickly becoming a no brainer, but hate to throw parts at it!

At an open track day I ran the car for about a half mile, wot, through 5th gear to about 6000rpm. Recorded speed on GPS speedo- 143mph (The car we barely beat said his speedo was pegged at 155) and take that for what it's worth, I'm not here to flap, just want to give as much info as possible.

The alternator has a 4ga lead off the output to the trunk, I also ran the 12ga wire from the plug to the alternator output, the the smaller (16/18ga) wire goes to an exciter/light in the dash. Which seems good, lights up when ignition is on engine off. The output lead is clean and tight. All grounds have also been pulled, cleaned, and checked for resistance.
The help is great!! Thank you, I miss my beast

[510rob]

1/2 mile at 143mph would be about 12.5 seconds. that is sufficient to develop a LOT of energy in the engine; remember that 1 HP = 746 Watts, so if you have 400 HP, then you are processing almost 300 kilowatts of energy, for roughly 12.5 seconds...

I'm stumped. When I get stumped by a problem like yours, I get out some paper and a pen and write out a matrix of variables that I suspect it could be, then try to systematically look for combinations I haven't tried exploring or that I might have missed. Sometimes the answer is some strange combination of variables that you skipped and it then jumps off the page at you.

I'm sure I sound like a huge skeptic now, but remember that just because a part is "brand new" does not ensure that the part works; new means new and unless you have tested that part, it is likely just an untested part (unless you paid a premium to have someone, or something, somewhere, at some level, test it for you). My experience has taught me that "new" merely means "another variable", and is not a 100% guarantee of any success in troubleshooting...

I don't suppose there is any way that it could be mechanically related? What kind of rods do you have in the motor? Have you done a compression test on the motor? If it was pre-igniting because of really hot plugs, there may be some residual issue inside the mechanical assembly.

Again, I am rambling, and again I am probably wrong.

[mell00510]

I have done a compression test, and found numbers were a little low for my liking so I pulled manifolds and performed a leakdown test on all the cylinders and found my exhaust valves weren't seating completely, assuming heat. So I pulled out the other 5 heads I have in stock. Gave them all a good once over, picked the nicest, had it pressure checked and shaved. Went to my buddies shop (works in the dyno room for amsoil, very smart, very picky/precise) we lapped in valves and he gave the head a quick massage in the ports, then took back to machine shop for a bath and then we reassembled it. Did another compression test and numbers seem good now 155 on 3 lungs, and 158 on the other one. The cylinder walls seemed clean, actually a little xhatch left! As far as the parts in the lower end they should be good to 6-700hp. I will have my friend grab me an oil analysis kit, then we can see what kinds of metals and such are ending up in the oil. I would drop the pan but nissan and their F*%#ing lack of offering an oil pan gasket really makes it a pain in the ass! I usually put the engine on an engine stand before ever attempting to take one off! Bastards! I will keep you guys posted thanks for the insight!
Here is a quick clip of me beating her-
http://youtu.be/PiwOQHQiusM