Pulling Timing in Boost

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Chris28
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Pulling Timing in Boost

Postby Chris28 » Sun Feb 26, 2012 8:54 pm

Like the title states, my engine is pulling practically all it's timing under heavy load, aka while I'm in boost. I datalogged a pull and it went from 40* btdc cruising to 3* in boost, so I'm not making any power at all. It feels like a knock sensor issue, but I'm not getting any fault codes, so maybe it's phantom knock? My first thought was it's a boost leak (which would also explain my idle issues), but a boost leak wouldn't cause the ECU to pull timing. Tomorrow I'm going to check all my ignition components and re-set my base timing, but in the mean time is there anything else that could be giving me these symptoms?


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Re: Pulling Timing in Boost

Postby hannibal » Mon Feb 27, 2012 2:34 pm

Just curious, what are you using for timing management?

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Re: Pulling Timing in Boost

Postby Chris28 » Mon Feb 27, 2012 2:57 pm

EFI Specialist ROM tune. I ran EFI's 370cc/stock mafs tune for over 2 years without a problem, so I don't think it's a problem with the tune itself, just something else telling the ECU to retard the timing.

I thought about the knock sensor earlier, does anyone know exactly why the ECU would throw code 34? I'm not sure if it throws the code when the sensor actually senses knock or when the knock sensor is just malfunctioning. It's possible the knock sensor is loose and causing a bad reading, but at that point I don't know if I would be getting a code for it or not.

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Re: Pulling Timing in Boost

Postby WDRacing » Mon Feb 27, 2012 4:22 pm

I believe it throws a code when it's broken, not when it see's knock. Although I'm only 99% on that one. Things that can mess with timing off the top of my head are vac, knock sensor, iat sensor, water temp sensor.

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Re: Pulling Timing in Boost

Postby Chris28 » Mon Feb 27, 2012 5:13 pm

Well just book leak tested again, turns out the two halves of my intake mani aren't sealing. It's leaking in the back corner next to my egr plate which is why I thought that's what the problem was. I guess I'll start pulling the top half off tomorrow to replace the gasket...any reason why I shouldn't use gray rtv instead of the paper gasket?

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Re: Pulling Timing in Boost

Postby Razi » Mon Feb 27, 2012 5:31 pm

Can't some of the RTV get squeezed into the manifold?
Have fun with the manifold job!

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Re: Pulling Timing in Boost

Postby Chris28 » Mon Feb 27, 2012 6:47 pm

Razi wrote:Can't some of the RTV get squeezed into the manifold?
Have fun with the manifold job!
Yeah some could, I guess I'll just go with the paper gasket and hope it seals. I'll check to see if the two halves are level while I'm at it. Hopefully this is the cause of all my problems, maybe running so rich in boost was causing the ecu to pull timing or something.

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Re: Pulling Timing in Boost

Postby neverlift » Thu Mar 01, 2012 7:23 am

does the timing pick back up after 5000~5500rpms if yes its definitely a knock sensor or wiring related issue! And get ready for about 70 whp on 10psi and I assume more on more boost.:)

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Re: Pulling Timing in Boost

Postby Chris28 » Thu Mar 01, 2012 11:09 am

Haven't watched my timing that high yet so I'm not sure. I fixed the egr leak, now the only vacuum leak I have now is the banjo bolt for my wastegate signal. I have the wastegate line crimped right now just to stop that leak for diagnostics.

Eprom chip being loose is possibly what it was. After re-installing it I hold a steady cold idle at 1500, it's extremely rich at 11.2 afr's though. The idle isn't smooth like it should be, but at least it's not ranging from 1500 to 2000 rpm.

Next step is checking fuel pressure after the pump stops priming. I'm putting a new pressure gauge on after work, if the pressure drops drastically when the pump stops priming it's got to be a leaking/stuck injector. I'll replace the o-rings to see if that fixes it, then I'll test drive it and see what timing does under load. If that doesn't work I'll try replacing the coolant temp sensor, I'm not getting a code for it though so I'm not sure if it's faulty.

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Re: Pulling Timing in Boost

Postby neverlift » Sat Mar 03, 2012 6:41 am

clean the cts and take a look at wiring for it. Thats another 28whp on an na ka..

my fuel pressure drops when the pump stops, always has(since AM afpr install). I've replaced all orings and been on 3 sets of injectors, new lines to and from it all, still pressure drops to 0.

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Re: Pulling Timing in Boost

Postby Chris28 » Sat Mar 03, 2012 9:11 am

Alright, a few developments since I last posted.

I fixed my idle problems and the car runs/drives normally out of boost now. It's still pulling all my timing in boost, there's no power at all. Starting with the basics, is is possible I installed the eprom chips incorrectly? It ran fine when it was NA, but there is a lot more load when boost is involved so something wrong might be apparent only in boost.

If my TPS were bad (it's showing .5v with the throttle closed and goes to about 4v at wot so I think it's fine) could it be causing the ECU to pull timing under heavy load? I replaced the narrowband o2 sensor earlier and I have a new coolant temp sensor to put on it, but I'm not sure if those would tell the ecu to pull timing without first giving a fault code. AFR's are fine throughout the rev range, there's only one area that is running rich and that's under light load situations like maintaining speed while going up a hill. When I do that it runs rich and starts backfiring, I need to actually be accelerating or decelerating in order for it to not run rich. I'll boost leak test again tomorrow, but at this point it's got to be something else seeing as I had a friend sitting in the car watching the timing during a pull and it went to 4* btdc. Could a bad distributor or ignition coil cause the ECU to pull timing like that?

I'll check the coolant temp sensor, I bought a replacement yesterday so I might as well replace it.

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Re: Pulling Timing in Boost

Postby neverlift » Sat Mar 03, 2012 10:24 am

man I can honestly say everything is linked to timing in nissan eccs. Off the top of my head it really sounds like a knock sensor, push it past 5500rpm if timing picks back up thats probably the issue. However , tps has timing control and the cts as well.


IF the chip is in backwards it would fry along with the db.

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Re: Pulling Timing in Boost

Postby Chris28 » Sat Mar 03, 2012 2:27 pm

Alright, I'll datalog a pull and go over 5k to see if timing picks back up. First I need to put a lower psi spring in my wastegate, 15 psi is too much for right now and I can always raise it with a boost controller later.

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Re: Pulling Timing in Boost

Postby Chris28 » Sat Mar 03, 2012 7:55 pm

FIXED! It was a combination of a few things, mainly the distributor. I was using my Consult software check timing, I should have been using a timing light. Turns out I was at 10* btdc, the out of spec TPS was causing the ECU to bump timing up to 20*, and since I was reading timing from the ECU I thought it was at 20*. I used a timing light today and got it to 20* at idle, took it for a drive while datalogging and I'm right at 15* in boost. Makes sense, before I was seeing around 5* under load, so when I advanced the distributor 10* it advanced timing throughout the rev range. It's at 7 psi right now, feels like my t28 setup did at 10 psi. Thanks for the help everyone!

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Re: Pulling Timing in Boost

Postby neverlift » Sun Mar 04, 2012 4:48 pm

ah I see, knock sensor was working perfect then, its was when you went past it in the map. Perfect sense.

timing needs to be set with the tps unplugged or the consult software forcing idle adjustment.


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