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View Full Version : Bad N75, MBC Override?



Tanzimur
02-20-2014, 06:26 PM
Al rite long story short i have a bad n75 valve 5ibs peak, stage 1 ssp tuning and such i bough this mbc off eBay ball and spring type Voodoo brand not bad at all but there is 2-3ibs of spike i was wondering if i run it parallel with the n75 even though its bad would the manual boost controller be able to overide it?

Seerlah
02-20-2014, 06:34 PM
No. Are you sure you are not running lean?

Tanzimur
02-20-2014, 06:47 PM
Im sure no nothing before my last engine dropped a valve i had one that came with the car it maxed at 3, then i got this one off of a junkyard car and it got up to 5-6 stock and still 5-6 with chipped ecu... car drives idles and everything fine. Yes i know i have to see with vagcom to see any other codes and such but no vag yet lol

Seerlah
02-20-2014, 06:57 PM
Car can drive and idle fine and you still be lean.

Tanzimur
02-20-2014, 06:59 PM
Damn so i should get that checked huh, with a vag com?

Tanzimur
02-20-2014, 07:12 PM
But wouldn't i get spark/ fuel cuts around 6k-7k rpm in full boost or misfires/ fuel lean trim CEL coming on and such if i were actually running lean?

Seerlah
02-20-2014, 07:17 PM
Not necessarily. You need to log your MAF readings for starters.

Tanzimur
02-20-2014, 07:21 PM
Alrite, im assuming i can check the duty of the n75 and maf reading with the VAGCOM lite?

Tanzimur
02-21-2014, 11:09 AM
heres a picture of what all the plugs look like... lean?!?!?! almost?!?!?! got a buddy thats one here coming by with the full vag scan to go through! but what you guys think?

http://i.imgur.com/iThhPcb.jpg

Tanzimur
02-21-2014, 11:11 AM
SUmthn close engough to that???
http://www.wallaceracing.com/Spark_Plug_Readings_Proper_HeatRange2.jpg

Tanzimur
02-21-2014, 03:40 PM
Thnx to martin, i dont know his name on here but seerlah he knows. He came by vag com it all up and only one fault which was the n75 open circuit and that my maf at idle is normal but in 4th gear 2500 to 3500 is at 47 to 58g/s which he thinks can be the problem... can u chime in seerlah just to get a second opinion i never changed the maf just ordred one on ebay.

Turbo Nerd
02-21-2014, 03:51 PM
The MAF won't cause the N75 open circuit code, so I think you have a few problems. He was pulling 3.xx g/s at idle which seems normal.

BaseDrifter
02-21-2014, 03:52 PM
I would start by swapping in a known to be working N75 before replacing the MAF.

Tanzimur
02-21-2014, 04:19 PM
Alrite but what about the 47 to 58 g/s reading we got isnt that bad also?

BaseDrifter
02-21-2014, 04:25 PM
Only if that reading is incorrect. If your N75 is faulty and causing the turbo to run off the WG spring only then I don't think seeing 47g/s is "incorrect", could be wrong though.

Tanzimur
02-21-2014, 04:31 PM
Huh ye thats what im trying to figure out i have stage 1 tune 18psi 2.5 in exhaust cone filter on stock tip bkr7e plugs gapped at .24 so idk at this point ive been running 16- 18 psi with a mbc fr a bit and want to use my n75 but theres the problem any one care to explain the maf numbers? And do those plugs look a little lean to u?

Tanzimur
02-21-2014, 04:37 PM
Lm0812 i read ur post over again and that really does make sense man now to confirm that... anyone?

Seerlah
02-21-2014, 04:53 PM
Your g/s should be roughly 80% of your chp. This needs to be done on a 2nd or 3rd gear WOT pull to redline. Those readings are low. And as already mentioned, the open n75 circuit needs to be addressed. Could very much be an old code from it being disconnected. Should have erased the DTC and seen if it popped back up.

Tanzimur
02-21-2014, 04:56 PM
Ye martin did erase it and it came back on. So the n75 open circuit can be effecting the maf reading? But cant be sure cause its suppose to be done in 3rd not 4th?

Seerlah
02-21-2014, 05:00 PM
Either that n75 is bad or you have a wiring issue. That is first. The n75 won't affect your MAF readings (will of course be different at 5psi and 18+psi). That is just the measurement of your air intake. If the MAF is faulty, it is not measuring it correctly.

Tanzimur
02-21-2014, 05:16 PM
Right 5psi versuses 18psi the readings would clearly be lower then expected?!?!

Seerlah
02-21-2014, 05:34 PM
80% of your CHP. So figure 150chp so your readings should have been around 120 g/s. Running at tuned boost pressure (18psi+) you would expect to see around 160 g/s. Those readings are low.

Tanzimur
02-21-2014, 05:50 PM
Damn alrite makes alooot more senae now thnx fer clearing that up man! Bte up above do thise plugs look a litle lean to u?

Tanzimur
02-21-2014, 06:47 PM
Also if i run 16ibs the way it is would i be running lean?

Tanzimur
02-21-2014, 08:45 PM
BUMP

rockersteady
02-22-2014, 04:21 AM
untill you figure out the n75 problem (Ive fixed em before just by unplug and plug em back in cleaning the contacts a little) then you can run the mbc if you really want. set it for less than the tune calls for 16psi sounds good. only problem with a MBC is you cant regulate boost with part throttle, it will keep boosting up to its setting when a N75 will regulate it

Plugs look fine to me, I dont know why we are discussing running lean here.

DONT run a ebay maf as a general rule, especially if you are chipped. Your old one seems fine to me with that reading. I get 100 + g/sec at 3000 rpm with a good stage 1 tune and that will be nearly 15psi at 3000 rpm. with no boost at 3500 youll be looking at a lot less like it is reading now.

happy days

Tanzimur
02-22-2014, 07:30 AM
Alrite cool thanks for all the info! Answered my questions and ye i picked one up frm wrk at oreilys for cheap discount cardone reman. Thought i would change to change it cause i never have... and on the lean topic i just wanted to be sure i wasnt doing anything that would harm the car.

Tanzimur
02-23-2014, 09:28 AM
So the aftermath car feels great and happy no more sloppy idle or exhaust pop while shifting between gears i take it i was running rich even after new 02 sensor so now i gotta find a local with a wrking n75 and go from there. Also have my ebay cable on the way and thanks to TURBONERD i downloaded the full vagcom software from socals4.com!

Tanzimur
02-23-2014, 09:29 AM
After i installed new MAF btw. On my phone cant edit...

Tanzimur
02-24-2014, 06:29 PM
Hell yes!!! sucesssss!!! I came back home from school around 830pm so im sitting there trying again to get some sort of voltage out of the n75 harness and got nothing so i try to feel around inside the loom and got to the end of the connector so i peel back the rubber surroindig the damn connector and BAM! connector fell into my hands both the wires looked like they were tucked back into the loom stupid previous owner was a complete dumass but got 5v out of the harness tommoro i plan on resoldering it all back!!!!!!!

Seerlah
02-24-2014, 06:42 PM
Don't solder. Use butt connectors.

Tanzimur
02-24-2014, 07:21 PM
Don't solder. Use butt connectors.

Sounds gooooood!