Pnm35 Build Thread

[iamhe77]

Would the first sensor be receiving too much (ECU is expecting gases from 3 cylinders, not 6) while the second sensor is not receiving enough due to the gas flowing around the first sensor?

Might explain the differences in fuelling each bank to compensate?

[PN-Mad]

Here you can see some data- % correction is on the left, and inj pulse on the RHS, in the middle you can see the Volts from the "A/F WB bank 1 and 2"

See how the inj pulse is uneven, and the ECU is factoring in a correction, even though all 4 sensors are reading very similar results?

Thats a fail.... I'll see if I can format it to work here...

Edited February 15, 2012 by PN-Mad

[PN-Mad]

have a look at this screenshot

[scotty nm35]

The ecu is trying to cycle the afr's and expecting the o2 sensor to pick it up for that bank. As you now have the two sensors in the dump it cant differentiate between the signals as they are merged as one. Did you make sense of that? Just switch the o2 feedback off and get a tune, you won't need learning hopefully.

[PN-Mad]

Makes sense- have emailed Mark with it to see if that is a characteristic of the ECU.

[Commsman]

What Scotty said is entirely correct IMO. As everyone knows, in closed loop the ECU cycles the injectors rich/lean & gets feedback from the O2 sensor/s. When it leaned off one bank & read the AFR from that banks' sensor, it was really reading the richer exhaust from the other bank. So it leaned it off a bit more, check - no difference, continue reducing injector pulse width until reaching end of ECU parameter (result is you get a rough idle or whatever).

When you pulled the O2 sensor off & put back again, it just so happened it was the other bank that started leaning off first & the cycle continued as before. Point proven I reckon.

Funny, I recall questioning this layout when I saw the pics (page 3?) because I couldn't see how it could work. But since I'm no engineer (well not an automotive one), I wasn't about to call it a HKS design fail back then. But now I think it is- just a little bit, lol.

Ideally the sensors should be moved so they are sniffing the AFRs in their own bank, but that's probably too hard. Disconnect so never run in closed loop....?

I hope you get it running how you want it Alex. It's looking great nonetheless.

[PN-Mad]

Thanks Leon.

I guess putting a o2 sensor in the drivers bank is possible, but with the size of it I would say it would be terribly restrictive. The pipe really isn't sizeable compared to say the dump pipe. And with the restriction, it wouldn't read right anyway.

What would happen if I spliced one O2 sensor, and connected both the banks to one O2 sensor? Those with sharp theoretical minds- not me at this hour....

Just to put it out there, this problem seems to have been experienced with 350z's- running high flow cats and the like. So I don't know how that works, because they still have bank dependent O2 sensors.

http://my350z.com/forum/tuning/478308-unique-problem-bank-1-overcorrecting-rich.html

Its running open loop for the moment. I hope I can get it closed somehow because there is benefit there- I can feel it in the "drivability"

That said, maybe it could be tuned around it.

[Daleo]

Personally, I think you may have to accept that there's no real way to trim injector duty cycle for each bank with the O2's in the current arrangement.

As Scotty & Leon have said; the ECU is making an adjustment; not seeing the result it wants on the particular O2 sensor that should be showing a change; rather it sees a condition across all four O2's which it doesn't like. It then continues adjusting; trying to get the result it expects, until it actually affects driveability.

There may be a way however; within the UPREV software to change to adjusting both banks of injectors as a unit rather than individually (and reading all 4 O2's as one; as per the VQ25DET). It might be a simple as a line of code. It won't have the pinpoint accuracy of the OEM setup; but ti would still be pretty damn accurate. I can't see another solution; unless you physically move the O2's into their respective manifolds.

[Commsman]

Dale, what you suggested is a good idea. Having read some the posts on 350z forum (& seeing how many people have a similar problem), I'm surprised they haven't been asked this question before.

What would happen if I spliced one O2 sensor, and connected both the banks to one O2 sensor? Those with sharp theoretical minds- not me at this hour....

Just to put it out there, this problem seems to have been experienced with 350z's- running high flow cats and the like. So I don't know how that works, because they still have bank dependent O2 sensors.

http://my350z.com/fo...cting-rich.html

Mmm, I don't think splicing them together would work. Typically in electronics when you double something up you halve something else. Worse case scenario you could blow up that input into the ECU because the impedance or voltage is too far wrong.

It is very confusing Alex. I stand by what I said before (co-located sensors can't differentiate AFR between banks), BUT why do the 350Z's experience a similar problem (albeit not quite the same by my understanding) with O2 sensors located on each bank.

Is there an inherrent ECU logic problem with the 350Z & PNM computers that only manifests itself when moved sufficiently away from stock, ie better exhausts/intakes & def FI?

As you said, it would be really nice to get the closed loop running right. Lots of benefits in fuel consumption & smooth driving to be had. I'll keep reading....

[PN-Mad]

Booked into Unigroup for the 1st March. Told them about the O2 issue.

Have to get the turbo beanie, dump wrap, Pump, injectors and Plugs sorted. See how we go!

[PN-Mad]

Tonight, Jetwreck and I dropped in the Injectors, changed the plugs, and fuel pump. Tune will be on Thursday. In the process I cleaned up the inlet tract- a bit of oil in there, not too much, and some ugly looking black stuff behind the throttle.

What we thought is that we should have a bit of a guessing game as to the power that it'll kick out. To give you the low down- Its a 3.5 litre V6, 10.3:1 compression, 600cc Injectors, HKS GT3037 pushing 0.35BAR or 5PSI, full 3 inch exhaust with HKS Cat. Automatic box. Car will be tuned in RWD.

Jetwreck guessed 223rwkw (right?)

My guess is 235rwkw

Post em up- see whos closest!

On with the Pics-

Down zee hole- for anyone who hasn't see one...

[iamhe77]

hmm, stock plenum with no spacer? ~230 at the rears

With spacer... 245.

Looks like you need rods and a Cosworth plenum

[GoldZilla]

Looking good, Alex! Hopefully the o2 sensor issue can be sorted.

I might try and head across to Unigroup on Thursday to come and have a sticky beak, it's not far from home.

[PN-Mad]

Spacer = more room to fill = more lag and less throttle response.

Trawled the net to find benefits for FI 350z/G35s with the spacers- but could find anything. No doubt beneficial for NA cars- but when air is pressurised, I think the effect would be less pronounced- prove me wrong, I'd love some real info.

Hey Nick- yeah, be good to see you! Drop in if you have time

Edited February 28, 2012 by PN-Mad

[iamhe77]

Did you feel noticeable lag off boost after installing the HKS kit?

Just wonder how much extra air was needed to fill all that piping and intercooler space.

I might be wrong, if there was some lag from filling the extra volume (say 10mm plenum height) it'd be negligible.

I also haven't heard of anyone noticing increased lag after installing a 19mm runner spacer on a VQ25det (closest I could get to increasing the area between the combustion chamber and the TB).

[Jetwreck]

opps.....forgot you are going on a rwd dyno.

I'll give you an extra 13 KW's for that.

so 236RWKW's

[Commsman]

How hot a day will it be? What's the barometric pressure & humidity?

242rwkw.

Lol, says me with such confidence (I've never seen a dyno run in real life). Good luck & I hope you get a nice surprise.

[Commsman]

doubled up.

Edited February 28, 2012 by Commsman

[slippylotion]

Ill pick 212rwkw.

[PN-Mad]

21 to 26 degrees. Cloudy, rain periods with heavy falls possible. Sounds like high humidity, Currenty it's 1014.1and rising.

The runner spacer volume is tiny compared to the spacer that 35s run. I'd take a punt volume wise, that it's be 10 times the volume. Remember, when you snap the throttle shut, the motor has to eat all the extra air in the plenum before it starts making vacuum. It's not a massive thing, but I just don't see the point on a fi motor. The tendency is to make smaller plenums. Yeah, I'd love a cosworth, they are no good for na motors.