Not hitting boost cut, 18psi, stock computer.

[milkandoj]

THIS IS A BULK NOVEL READ MY 4TH POST TO GET THE GUIST

OK though id ask for some input as this is bothering me.
My boost cut worked before when i got 15psi of boost and now it doesn’t.
After doing some mods to the car i was running gate pressure for a while, decided i would wind to 14psi, hit just over 15 and no cut so i tried more on a cold night to see if i could slap the cut, briefly hit 18psi not cut. Im reading boost from my gizzmo boost controller and sourced from fuel pressure regs source.


This is what’s changed, i blew the 14b up, installed a hybrid small 16g that’s been fitted with a bigger compressor wheel. Ported the hell out of the exhaust side, im not looking at boost creep probs as it sits on 8-9psi when running gate pressure.

Its the computer, the signals its getting, airs being heated too much by turbo, or I have a leak.

Ive had all the intake out and back in the car ect. possibly i have a leak now.
Also did clutch and had gearbox and all off the same time but this has stuff all to do with this.

Also with that put on an evo 3 exhaust manifold and dump pipe and i ported that to.

Ok so my understanding is, the computer measures the amount of air coming in and when it sees what is equivalent to 15psi on a 14b, cut. So why now with a bigger turbo am i running more boost. 15psi on a 20g even is around 600cfm. a 14b is like 400cfm off the top of my head.

The cut worked before when i had the 14b in there and hadnt ripped everything out and back in the car.

 

[milkandoj]

I split posts so it doesnt look like a novel..... some ideas i have...

Either the afm isn’t measuring all the air coming in and I’m running lean.

Or the second hand turbo a heap of shit and heating the air up way too much, im only sucking in so much air but its heating it and pressure is gaining a few more psi than it should.
Its whistles slightly when its on boost , more boost the louder it si but its not that loud and ive heard other turbo’s do it, there is a bit of wear on the blade edges, they are slightly rounded not sharp like a new turbo. but no chips along the blades. Sounds real cool though haha.

Or turbo, which is bigger than a 20 wheel in there isn’t in its efficiency range yet and blowing hot air? i don’t think it'd make this much difference.

Boost leak, as ive had all the intake out and back in. but wouldn’t i hit boost cut earlier like 12psi coz I’m loosing air in the piping between afm and throttle body.
Or is it possible a small leak is causing air to heat up increasing the pressure.

Or the boost gauge on the gizzmo is wrong. But with the manual boost controller in and a hks boost goost gauge i hit over 1 bar then turned it back down when i was turning it up to take the drags. so i think this probably isn’t the boost controller its to do with something after i worked on the car to put the new turbo and had all the intake and all out.

Ideas people?? i want to hurry up and put in my chipped ecu along with the 055 and 510's so i can log and see if its pinging from this. and maybe buy an innovate LC1 air/fuel ratio sniffer and install as i was planning, so i can see what my ratios are.. Im kind of short on cash at the moment so i want to really diagnose this till I can put computer in as I need to do the intake an relocate battery to. Till then im back on 9psi.
Either way i belive i could be runnin lean of blowing hot air in the motor.

 

[milkandoj]

Heres pictures of my plugs, pretty sure we number them 1 left to right 4 if you standing facing the motore from the front.

The colour looks goos but im worryed the whitish tinges on parts of them could be a sign of leaning out?

Plugs are around 5000 kms old and ill change them soon. Cars been back on the road after new turbo and clutch ect for around 2 months, ran gate pressure for around a month and last month i been on 12-13 psi.
I thought also is your running lean sometimes you heard slight popping under full load and boost (like i heard in my mates skyline, told him to look into it have he cooked his motor 3 months later) and i havent heard that.

 

[JAP63]

Hmmmmm lots of info to take in there mate
basically your saying your running more boost on the bigegr turbo and not experiencing cut, right?
I know when i went from a 14B to a small 16g, i hit cut earlier with lower boost, because the s16G flowed more.


The 14B at 16-17 psi would flow around 2200 Karmans
The 16G at around 13 pound would also flow around 2200 Karmans.

The car experienced fuel/boost cut at around 2150-2200 Karmans....so as you can see, your gonna hit the cut earlier on a larger turbo.


Your car isnt MAP sensored, so your "isues" arent to do with whats happening after the compressor, without going too much into it and having a quick guess..

Id say either...
1.AFM not reading True Flow Values.
2. New turbo delivering innsufficient air levels.

 

[milkandoj]

Correct, thats my thinking, i just wrote a novel to say my theories.
Its either the afm isnt reading properly and im running lean.
Or turbo is heating air up.

This oly happened after ive had the car apart for new turbo, exhaust manifold and dump pipe, clutch ect. I do have a leak between head and exhaust manidolf gasket but shouldnt inpact on this.

I dont believe the turbo isnt flowing enought it goes well. even on 12psi i recon it'd pip the 14b at 14. PLus i have drag timeslips to prove my mph is slightly higher with the hybrid 16g at 13-14 psi than the 14b was. So turbo is pushing air, but hot air?

I was racing a rallyart colt he was runnin 15psi with more mods than me, and i 8psi after work, ate him everywhere.

Are our afms's safe to spray with electriucal contact cleaner, i might go nuts with that and see how i go.





How can i test the afm?
I might test the oxy sensor with a multi meter tomorrw, if i get under .8v ill be worryed. off top of my head i bounces around .6v when idleing and cruising to save fuel. Anyone got the scale of volt reading vs air fuel ratio so i can refer to it. Its only a narrrow band but might give an indication as will read stoirch and higher. It runs open loop under power so computer ignores it and takin the plug off wont affect radings right?

 

[CLuTZ]

perhaps getting a dyno power run with AFR check might help

also- do you datalog?

it seems strange that the setup is less efficient, with an obviously more efficient turbo.

 

[JAP63]

I do have a leak between head and exhaust manidolf gasket but shouldnt inpact on this.

Id deffff be fixing that,any air that escapes here and dont get to the turbine wheel aint spinning your turbo, u dont spin your turbo, you dont spin your compressor wheel, dont spin the compressor wheel, you dont flow air

How bad is it?

 

[milkandoj]

lol of course i know i have to replace the gasket.
I will fix it i know it'll rob me of performance. I can just see the carbon thats being sprayed out. over the side of the head.

Tryed measuing the signal form the oxy sensor, somethimes it was giving a signal others not.... ive measured it before and it worked fine. Wanted to see if it was running lean.
bit weird, even when i just measure form the plug and not running a wire into the car, it would give a signal sometimes others not. Ill try with my digital multi meter tomorrow.


I would have thought a check engine light would come up if ecu know of somehting wrong with afm.
came up even when i snapped a plug for wter temp sensor.

So im lookin at the afm? I knoticed a plug was off a sensor on the top of the throttle tonight, put back on, could still wind boost to 16psi???

Thanks for your reply.

 

[JAP63]

So im lookin at the afm? I knoticed a plug was off a sensor on the top of the throttle tonight, put back on, could still wind boost to 16psi???

Thats sounds like it might be the TPS, if this came unplugged, id surely expect a CEL, check the globe aint blown
Heres another tip, even though you can run the higher boost, dont...not till its sorted anyway, like said earlier, get a dyno run with the AFR's sniffed.
Id get all your mods (and leaks) sorted then hit the dyno to see whats happening.

P.s- Kev is a Sicko.

 

[milkandoj]

No i dont log, yet, with my duel board, i got a palm to do it but have to put in my chipped single board to do it. and its chipped, actally i just remembered if i dont put the chip in i dot have to put in the afm and 510's to match. Might do that.
The engine light should work because i got it when i first had the car back on the rd as a plug on the water temp sensor broke and i found the error code for that.




Ill throw in the single board computer, log and see how i go.

 

[to4garret]

I always thought JSpec's boost cut was alot higher than 15psi.

perhaps your old 14B had a boost leak somewhere causing it to cut at 15psi, where as now the leak is fixed.

just a theory.

 

[milkandoj]

Can someone confirm what the boost cut of a pre facelift jspec is?

I honestly dont think this is that case, even if boost cut if say 18psi on the 14b and stock setup.

If i guess the compressor map for this turbo by puttin it somewhere between the map for a TD05 big 16G and a TD06 20G.
At anything above 15psi its starting to show its face and 18psi, its kicking the 14b's ass in flow.
The turbo is a evo1 16g, fitted with a wheel around 53mm or a tad more in inducer and 68 in exducer, so slightly bigger than a 20g wheel and 070 rear end i ported. And compressor wheel is a 7/14 blade.

So it should Flow!
Which could lead to the turbo isnt efficent and heatin air, as its second hand. But the car goes well.

It's xmas eve day so im flat out but ill try take intake off and back on and make sure air isnt gettin in after the afm. Put in my single board ecu and do some logs, i gotta make the cable up tho, so gotta look around magan wrecks for the plug to the ecu diagnostic port. If anyones got some spares let me know.

Thanks people

 

[to4garret]

mmc boys say anywhere between 15-20psi, doesnt seem to be a hard and fast "thats the mark"

 

[JAP63]

Can someone confirm what the boost cut of a pre facelift jspec is?

With 14B, around 14-16 psi.

 

[Aussie Babsy]

The 14B at 16-17 psi would flow around 2200 Karmans
The 16G at around 13 pound would also flow around 2200 Karmans.

when you said tjis did you mean Kilograms, or is Karmans another form of measurement? if it is could you give me a conversion?, I'm trying to get an idea of what the biggest wheel i can run in a TD04-13G without affecting Spool to much, and real flow rates give me an idea on what I'm looking at no the compressor maps.

 

[mattrat]

i think he means hz, afm's read in hz
the vr4 afm is a karman style air meter but it translates that into hz for the ecu to read

 

[JAP63]

i think he means hz, afm's read in hz
the vr4 afm is a karman style air meter but it translates that into hz for the ecu to read

What he said.
Exactly.

 

[Aussie Babsy]

ok, thanks for that
i feel like a noob now lol

 

[JAP63]

On the 14B, i would hit boost cut around 2200-2400 Karmans...this (on my car) translted to about 15-16 pound.
MODS-Catback,no cat,Filter..It would always come in around 5000Rpm, where peak torque was made.


I would suspect that in colder weather with dense air, you may flow 2200 Karmans at lower boost, i noticed this occured when it got colder as the air had become denser, so to speak.

My S16G flowed around 2200 karmans at 13 pound, which shows the larger exducer on the compressor wheel physically pushed more air. A larger, and more efficient turbo should theoretically flow more air at lower pressure. In your case, you should be (from my experiences) getting boost cut somewhere around 1 bar.

This boost cut should be coming in hard and abrupt, and at around 5000Rpm.

 

[youda]

just a thought, did you boost it on a hot/cold day makes a big differance in summer and winter