Hi guys,

 

What do you reckon on this one, When driving if i put my car say in 3rd while going slow and put my foot down, it starts to build up power but as soon as my turbo gauge hits maximum boost it starts hesitating, popping, and backfiring.

 

It revs fine, then you can watch the turbo gauge build up to it hits the top of the standard gauge,(running 14psi have after market gauge too.)and as soon has it hits full boost the car plays up, But if i rev it normally say hold it in gear its fine, only does it when in a gear where your down low in the revs and try to build up power,

 

Hope that makes sense,

 

Any help appreciated, thank you.

Sounds like you've got an ignition issue and its struggling to spark across the dense mixture - maybe new plugs needed as a first check. Either that or your ECU is hitting the boost cut if its stock.

or a MAF issue

Sounds like you've got an ignition issue and its struggling to spark across the dense mixture - maybe new plugs needed as a first check. Either that or your ECU is hitting the boost cut if its stock.

 

Not seen any active boost cuts on 92 models.

 

Jeff

 

or a MAF issue

 

My thoughts too Tony!

 

Jeff

Not seen any active boost cuts on 92 models.

 

Odd, all the values in the TP limit table are the same on all 8 bit TT Stock codes that I've ever seen @ 128.

Odd, all the values in the TP limit table are the same on all 8 bit TT Stock codes that I've ever seen @ 128.

 

What feed back does it use though?

 

Jeff

TP Calculation is based on MAF voltage corrected for sensor curve then with several mods for throttle enrichment etc. Essentially though its air flow.

TP Calculation is based on MAF voltage corrected for sensor curve then with several mods for throttle enrichment etc. Essentially though its air flow.

 

With no real time manifold boost level then no input exists for acitve boost cut, turn the boost up on a zed with a standard ecu and it will boost to destruction if you let it, no boost cut. seen the results of this in the past.

 

Jeff

With no real time manifold boost level then no input exists for acitve boost cut, turn the boost up on a zed with a standard ecu and it will boost to destruction if you let it, no boost cut. seen the results of this in the past.

Jeff

 

It does exist, its just implemented as an air flow cut not boost but as the table is air flow / rpm based its close enough to the same thing. It definietly works, you can adjust it on the dyno and see the results. Normally set it to 110% of max TP on full boost at each rev break point. On stock its set pretty high. Suspect when people have blown them then there may be other underlying problems or incorrect timing etc. etc. or they have a JWT or similar ECU with the cut removed completely.

Hi Thanks for all the replys,

 

Think it may be my thought, last time i drove it only put a tenner in it and drove it home,

Put more fuel in and seems ok, weird though as its only 2miles home from garage and even a tenner should have gave it around 7litres, unless its doing 2 to the gallon lol,

 

Or the fuel was crap bp ultimate,

 

Cheers again 4replys.

Does a zed MAF sensor use a 'ceramic' tile to measure airflow?, whereby the flow of incoming air drawn over a heated ceramic wafer thin tile cools it and and the amount it is cooled by gives it the airflow volume (hope that makes sense :) )

 

If it is the tile type, as used on v6 vauxhall/opel engines , the tile can become coated with a film of crap, especially with pre-oiled filters and giving it a delicate clean with a cotton bud and electrical contact cleaner can often cure a lot of maf sensor faults :)

Very exciting read this.......... :tt1:

 

Battle of the Zed Gods....... JD and JZW... :scared: :winkiss:

 

Alz. :tooth:

It does exist, its just implemented as an air flow cut not boost but as the table is air flow / rpm based its close enough to the same thing. It definietly works, you can adjust it on the dyno and see the results. Normally set it to 110% of max TP on full boost at each rev break point. On stock its set pretty high. Suspect when people have blown them then there may be other underlying problems or incorrect timing etc. etc. or they have a JWT or similar ECU with the cut removed completely.

 

So as I said no real time boost cut. afm derived cut is prone to variation that cannot be relied on and hence is relegated to a sub level determination, taking into account the standard high setting that was written into the stock map suggests the lack of trust in this method, absolute pressure sensing is the only true descriptive boost cut that works in real world situation with all the variables that can take place and do under the bonnet when on the road, most zed owners will never encounter this as a direct problem one of the many variables is the cause.

 

Jeff

to mere mortals like myself , this is like head scratching rocket science . i wish i knew what you were both (jeff & john) on about . lol

to mere mortals like myself , this is like head scratching rocket science . i wish i knew what you were both (jeff & john) on about . lol

 

Me 2 lol,

 

But my problem didnt go away with the new fuel must have dreamed it.

 

Took it for a drive today and its still their mainly in 5th if i go along around 2000rpm, put my foot to the floor it starts to pick up like normal, you can watch the turbos spool up on the gauge and once the car hits maximum boost 14psi on both gauges it starts playing up by jerking around and you get some big gun shot loud backfires.

 

Changed ptu, and maf, No difference.

 

pulled all coils and plugs had a look to see if i could see anything but gonna have to get some new plugs (have no spares) and then try them with some spare coils i allready have,

 

Gonna check tomorrow for boost leaks and make sure all connections are clean,

 

Other then that im lost, i will just have to boot it around everywhere instead of trying to cruise in 5th lol.

What colour were the plugs when you removed them?

Could be that you might be getting a little over fuelling going on?

What colour were the plugs when you removed them?

Could be that you might be getting a little over fuelling going on?

 

They were black, but running central 20 ecu, so is running a little rich,

But its only just started doing it,

 

before use to pull from 30 mph in 5th, without a problem, now its pop pop bang bang, lol.

So as I said no real time boost cut.

Its still an engine load cut regardless of what sensor its based on. Air flow is a far more fundamental measurement of engine load than boost alone. If you swap the cams on and TBs on a stock VG30DETT then you’re going to see far higher air flow rates at the same boost pressure on a stock engine. In that instance the TP based cut would save the engine, a boost cut would not.

afm derived cut is prone to variation that cannot be relied on and hence is relegated to a sub level determination

Prone to what sort of variation exactly? Other that variations in air temp which are accounted for by the fact it’s a MASS air flow meter its only metering air, it doesn’t see any real turbulence effects unless you fit a bad filter design. At the end of the day, it’s the ECUs primary load sensor, it relied on entirely for the operation of the engine. If it was prone to variation then the engine would not run properly. Its no mistake that every modern production car uses AFM as their load sensor, it’s the only way to get the accuracy required to meet modern emissions standards.

taking into account the standard high setting that was written into the stock map suggests the lack of trust in this method

That’s only an assumption. Its equally valid to assume that the engineers simply chose to implement a load cut strategy that would protect from a wastegate fault or split line which would make Nissan look bad or lead to a warrenty claim (which the TP cut does do) and didn’t worry about people doing unsupported mods. Its also not hard to believe that with the 280bhp ‘gentlemen’s agreement’ in place at the time the 128 TP value is to allow some gentle tweaking - otherwise why have maps upto ~100TP/13psi in the stock ECU. FYI TP=160 is ~18psi on a stock(ish) setup so its well below that. Its very repeatable too, if you hold the load on the dyno you can set it accurately on a custom map.

Do you not think given the effort on the rest of the ECCS system and the lengths they went to (even a fuel temp sensor!!!) that if a MAP sensor was necessary it would have been fitted? The ECU has spare 0-5v inputs and there’s already a MAP sensor there for the boost gauge which could have been used for almost no cost.

absolute pressure sensing is the only true descriptive boost cut that works in real world situation with all the variables that can take place and do under the bonnet when on the road

Sorry, but that’s completely untrue. Any mods that significantly change the VE curve of an engine render a boost based cut meaningless unless the ECU is remapped. An engine running de-restricted intakes, TB’s bigger turbos and a good exhaust would blow long before it hit a 15psi boost cut that was perfectly safe/effective on a stock engine assuming the maps were unchanged, the dynamic CR would be way higher and timing requirements would be for much less advance.

On the emeralds I fit I use alpha-N / MAP load sensing and do use a boost cut but that’s only relevant when the engine setup is completely unchanged. With a MAF based system it will at least sense the extra air flow and cut the ignition.

most zed owners will never encounter this as a direct problem one of the many variables is the cause

To be fair, we’ve kinda gone off piste here and what I’m sure your experiences will back up is that almost all blow-ups just come down to bad modification and / or not sorting the basics out first!

Hi guys, this misfire thing is still driving me mad,

 

Was checking all wiring and 2 wires on fuel pump relay touched where a previous alarm or something has been wired in, which popped my chipped ecu, so had to put standard one back on and remove boost jets, so its running around half a bar (safe mode) for the minute, but its still messing around so guess that rules out a boost cut or blowing out the spark,

 

changed maf with another i had spare,

Plus ptu,

Cas,

 

PLus connections on temperature switch.

 

and even changed tps,

 

Checked ecu socket and all connections under bonnet wiggled everything and everything seems good.

 

I have noticed if i blip the throttle in neutral from tickover to 2100rpm exactly, the second the revs start coming back down i get a big pop like a gun shot from the exhaust,

Any higher or lower when i blip the throttle it wont do it,

 

Have done a compression test and either my compression tester is messing around and it wont go over 152psi or every cylinder is identical, cause they are all on 152psi which i know their ment to be very similar but never tested a car and found them all to be exact.

 

So today advanced the timing to its maximum the cas will let it go and pop in neutral was still their but very slight, So pulled covers off to check cam belt marks, they lined up with cover marks pretty well, so carefully took cambelt off without anything moving and refit the belt using belt marks, but its very hard to tell but looks like it could have been 1 tooth out on the last cam (cas),

 

Still got to fit it all backup tomorrow to know for sure, but what i was thinking if it was out by one tooth wouldnt it be noticable on the compression test and through out the whole rev range not just one point in the revs in neutral and when poodling along say in 5th at slow speeds and then trying to accelerate without dropping back a gear, (my last engine i could be in 5th from about 35mph and it would still pull no problem at all)

 

When its cold i know you shouldnt go mad but if i try to accelerate it just holds back and pops and bangs.

 

Anyone else got any thing they would recomend checking or had anything similar,

any help appreciated. thank you.

Edited December 7, 201114 yr by Terry

sticky injector dumping fuel on boost?

sticky injector dumping fuel on boost?

 

Any ideas how to test them without pulling plenum, never thought of that,

not sure tbh ive always taken them out to get them tested, not sure how well it works but you could try redex thats supposed to clean them but might not stop it sticking open if that is your problem.

 

without changing them i dont know of a way of eliminating them, id eliminate everything else first before shelling out on a new set thogh

Sounds silly but run the engine in the dark!-I had the same symptoms and whilst messing on the drive and my eyes got acustomed to the dark I saw 2 coil packs arcing like mad onto the Plenum!

Mine was great one day,then the next started running rough,under no load it was o.k but under boost it died popped and misfired like hell.

Worth a shot!:chinese:

Sounds silly but run the engine in the dark!-I had the same symptoms and whilst messing on the drive and my eyes got acustomed to the dark I saw 2 coil packs arcing like mad onto the Plenum!

Mine was great one day,then the next started running rough,under no load it was o.k but under boost it died popped and misfired like hell.

Worth a shot!:chinese:

 

Have ago tomorrow, once its all put back together lol, many thanks.

Hi again,

 

Put cambelt back together today and started her up still the same:angry:

 

so pulled the coils out one by one and put a plug in to see if i could see any arching out,

when end of plug is on the engine sparks as normal, but if i face plug in the air and put the plastic shaft bit near metal i do get slight arching but the problem is i can get all 6 coils to do it, either their all broke or its one of them and cause it dont do it all the time its getting hard to find.

 

So dont know where to go from here its either drive it until it gets worse that its easy to find or suffer it.

 

Would a coil make big gun shot type backfires, to me its like its got to be a trigger problem or a break somewhere making coil fire at the wrong time.

But why only when the revs come down from 2100rpm. and in higher gears when driving slow then trying to accelerate without going back gears.

 

Im lost and to be honest im getting sick of the car,

i re shelled it and painted it 3times, its had 3engines 3sets of turbos an auto box and this is the 2nd manual box. clutch after clutch, shocks bushes, you name it its had it and it still wont run right,

i am allways skint cause the car gets nearly every penny i earn spent on it, problem is its like a never ending story i have it painted and it looks great then the engine/turbos or something horrid will go then by the time i sort money out and fix it, it gets a few stone chips supermaket dents, and has im so fussy it needs painting again, in the last year and half i have spent 6000 on paint, could have bought a mint zed for that alone.

i just want it painted so it looks great and everything to run great for just one yr.

Then you see my mates one in london his had a few problems with auto boxes but other then that its never bloody broke.

 

Sorry for going on but gotta say it to someone misses will kill me if she hears me say it has its what she has been saying for years, and i keep saying to her once its done we will be able to drive and enjoy it, Please tell me if i am dreaming or could this actually one day happen,

 

Thank you.

the spark will always follow the easyist route to earth, i doubt there all knackered tbh you'd have to be pretty damn unlucky!!! if they dont arch when they're in place they're prob fine, any smoke on accelaration?