very lean AFR @ +/-3000-3500 rpm [SOLVED]

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RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

very lean AFR @ +/-3000-3500 rpm [SOLVED]

Post by RJBijsterbosch » Thu Aug 17, 2017 8:28 pm

Hello,

I'm Robbert from the Netherlands. I'm new here on the forum and Nistune, but i'm eager to learn more about NIstune and tuning. And i have a very strange problem with my car. Hope that someone on the forum can help me in the right direction. Even my tuners have no idea. Eventhough no bad words about my tuners. Because for them this is also very strange.

As mentioned i have a very lean AFR @ around 3000-3500 rpm. This is @ cruising on the highway around 120KM/H @ the highway so very annoying. If i drive a little bit faster or slower evereything is fine. On WOT there is no problem. This problem occures @ every gear.

It's a skyline r33 gtst with a Z32 Nistune ECU.
The car was first tuned with a almost stock set-up @ 340HP. No problems @ all with the car. this was a few years ago.

Now the car has a Greddy style intake manifold . Because it's easier to bolt on top feed injectors on this intake i asked my tuner which injectors he recommend. He told me to use the Siemens 875cc Deka topfeed injectors. Although i found them very large for my set up. My tuner told me that this was no problem. The injectors have very linear shape. Injectors are new. A Fuellab FPR is used to maintain 3 Bar fuel pressure. A 80mm throttle body is mounted.
Because of the intake and injectors the car is tuned again. After the tune the probem occured.
With this tune the car runs 361HP @ 420Nm on WOT.

My tuner told my that the car was running bad because of the 80mm throttlebody. So i removed the throttle body and placed the Original 63mm throttlebody with a adapter to fit the intake. The problem was still occuring.

Then he tought that the fuel pump was dying (Walbro 255 L/h). On his advise i changed the fuel pump for a better and larger pump. Aeromotive 340 L/h. The problem still occured.

The AFR is very lean @ around 3000-3500 rpm. 18 to 20 AFR.

I have checked the car for vacuum leaks 2 times and i can't find any leaks.

I now have purchased the nistune software myself, to do some datalogging and checking the maps. I also place a Wideband O2 sensor. Innovate MTX-l Plus.
What i found out is when i try to put more fuel in @ the specific load and rpm where the problem is occuring, the AFR still stays lean. Even with the narrowband O2 sensor disabbled the engine is not reponding. Also the STFT is getting sky high @ this point but it has no effect.

If there was still a vacuum leak @ this specific point, you would say that the AFR has to become rich when extra fuel is added.

It looks like the hardware on the car is ok, but i will double check this.

Things i'm planning to do:
Sparkplugs (already replaced)
Exchanging coilpacks
Open the BOV to check for defects
Exchange the CAS sensor

Hope that someone can help me out,

Regards Robbert
Last edited by RJBijsterbosch on Sun Sep 17, 2017 3:38 pm, edited 1 time in total.

RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Fri Aug 18, 2017 1:43 am

I've been driving around today to do some testing.

What i found is that the injector latency is set to 700us in Nistune. But the specs of the injectors show 1.3ms/0.7ms opening/closing time.

At first i changed the latency to 1000us. This worked a little but not enough. Then i changed latency to 1300us. That hits the spot. The engine is now running smooth @ 3000-3500 rpm and is now @ +/- 14.7 - 15.5 AFR

The only thing of course is that @ lower rpm the engine is running very rich. Need to figure out the get that right.

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Torque
Posts: 633
Joined: Wed Jun 16, 2010 10:08 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by Torque » Fri Aug 18, 2017 2:26 am

Hello!
Have you checked that AFR ratios in the map are in line with real world AFR?
(e.g. setting all values in the map to 12AFR (disable closed loop) and then check what the WB indicates?

Also at what TP does the problem occur?
How does you fuel map look like?

The DECAs seem a bit strange for a 4 valves head, but that's just my opinion.

RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Fri Aug 18, 2017 7:03 am

Have you checked that AFR ratios in the map are in line with real world AFR?
(e.g. setting all values in the map to 12AFR (disable closed loop) and then check what the WB indicates? Do you mean AFR auto tuner?
When i look in map view the AFR the wideband is showing is almost/or the same as showed in map view, only @ 3000-3500 rpm it's to lean

What i see in the log, is that al parameters are staying in a flat line. The only thing that is changing is the STFT, it goes from 21% to 0%. And when this happens the injector time also becoming less. And the AFR is becoming lean.

Rpm= 3200 and stays the same.
TP(load)= 4350 and stays the same.
TP(load index)= 17 and stays the same
TPS= 1,20V and stays the same
MAF= 2,96 Volt and stays the same
Inj time= 3,72ms and goes to 3,2ms
STFT= 21% and goes to 0%
WB AFR= 14,7 goes to 17,5

Matt
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Re: very lean AFR @ +/-3000-3500 rpm

Post by Matt » Fri Aug 18, 2017 12:51 pm

Hi Robert. Welcome to the forums. Whilst you have a very concise description of the problems, what we normally are looking for is a copy of the tune and a log file showing the problem to actually make any progress with seeing the cause of the problem

There are many issues which are raised here (and via email) which end up being mechanically related so part of the process is to look at the log file against the tune file and check what is going on

Particularly what I need is a log taken when cruising before/during/after the problem area with wideband input into the software. This way I can look at the following

(a) Your injection time against RPM/TP(load)
(b) Your reported AFRs against RPM/TP (load)
(c) Other factors affecting injection time such as STFT/LTFT fuel trims and O2 sensor

If I see your injection time steady but your AFRs changing then its a mechanical issue. If I see your trims changing then its an ECU related issue

If you can take a log with wideband data and post then we can have a look

Also the 'Estimated AFR' in the fuel map is only an estimate. The ECU does not 'know' actual AFR values, the raw numbers in the fuel map are multipliers to create a final injection pulsewidth.

Latency incrasing may just mask the problem by adding a fixed extra amount of injection pulsewidth (about 0.3ms in your example)

RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Fri Aug 18, 2017 7:31 pm

Hello Matt,

Here are the files. Hope you can use them.

From 2:25 minutes you can see the best what is happening.

I understand what i have done with changing the latency. When the problem occures the injector opening time is falling back 0,6ms because of the STFT is going from 21% to 0%. I have compensated this by adding 0,6ms with latency. The thing that i saw when i adjusted the latency is that the STFT & LTFT were 0% all the time. This is the situation that you want to have. The fuel trims need to be close to 0 to get a good tune. But the Trims are all over the place. So i think i need to get the Fuel trims close to zero and then the problem is solved.

The question is how do i get the trims right? :D Is this mechanical or is it ECU related.

I'm really curious what youre findings are.
Last edited by RJBijsterbosch on Tue Aug 22, 2017 4:52 am, edited 1 time in total.

Torque
Posts: 633
Joined: Wed Jun 16, 2010 10:08 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by Torque » Sun Aug 20, 2017 7:35 am

Hello :)

I had quick look at the log.
I filtered out all the decel fuel cuts and anything below TPS=1V
I also set a filter on anything below 17 AFR.

It seems to me the lean condition is not only at 3200 but all over the place.
Same for TP.

Possibly a mechanical issue, but that's just my guess!
Vacuum leaks are often more pronounced at low rpm ... but your log doesn't go any higher than 3387 rpm so hard to tell





What AFM is in the car?
You mentioned a BOV valve?
What kind of WB are you using?
afrcruise.JPG
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RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Sun Aug 20, 2017 6:49 pm

Hi there, THX for looking into my issue.

I want to say that the tune is not done by myself but by my tuner, i'm not that experienced enough that i want to do this myself (yet)

What AFM is in the car? It's the Original MAF for the R33 GTST Green Sticker
You mentioned a BOV valve? It's a HKS SSQV
What kind of WB are you using? It's a Innovate MTX-L Plus

I understand what you are saying about the engine running lean. This weekend i did some leak checking (again). I have put pressure on the intake piping/manifold and looked for leaking with soapy water. No leakage found. I know that this way of checking is good to find big leaks, but small leaks are hard to find. Maybe i need to do a smoke test also. See if this will help and find leaks that i overlooked.

I was also thinking that it could be the ignition/coilpacks/cas sensor. But this is ruled out/excluded. When i changed the injector latency by 0,6ms, the engine was running smooth (although very rich above and under 3200rpm) @ 3200 rpm and @ 14.7 AFR.

Conserning the BOV. I have checked this weekend if the BOV is leaking @ idle (with brakeclean). No external leaks found. What i did find was a internal leakage.
I had pressure on the intake piping and left the vacuum hose attached to the BOV off. Air was coming out of the vacuum line (steel pipe on BOV). I don't know if this is normal?. I dissassembled the BOV to look for some damage. Everything in the BOV is in it's place. The membrane on the vacuum side looks ok, but it's hard to tell if it's punctured. There is also a nut inside which connects the membrane to the shaft. This nut contains some kind of epoxy and has 4 tiny holes. Don't know excactly if these little holes are used to equalise pressure? Maybe air is leaking through the sealing of the shaft/nut/membrane. And therefore the BOV is not working right?

I don't know exactly if the leakage that i found is intended to be or that it's a defect to the BOV. This is the last day of my vacation and tomorrow i have to work again :mrgreen:. I'm have to go to the workshop, and will fabricate something to take off the BOV and do some testing without the BOV. To see if this helps.

Still under investigation.

Regard,

Robbert
Last edited by RJBijsterbosch on Mon Aug 21, 2017 2:31 am, edited 1 time in total.

Torque
Posts: 633
Joined: Wed Jun 16, 2010 10:08 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by Torque » Sun Aug 20, 2017 9:45 pm

Hello,

I don't know about our BOV setup ... but generally BOVs and MAF systems are contradictory because the BOV vents metered air away from the system.
(It's like an air leak)

This however should create a rich condition, not lean so I presume it's not the problem.

Is your Innovate WB wired as the O2 feed to the ECU, or is it stand alone?

In your bin file I noticed that the latency vs voltage parameter has been changed from the standard value ..
Maybe that's something to double check, I'm not too familiar with that value but I think the general message was to leave it as is.

I'm sure Matt can help here, or if you like set it yourself and do a testdrive.
voltlatency.JPG
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RJBijsterbosch
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Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Mon Aug 21, 2017 2:25 am

Torque wrote:Hello,

I don't know about our BOV setup ... but generally BOVs and MAF systems are contradictory because the BOV vents metered air away from the system. Yes, I know but this is only when closing the throttle
(It's like an air leak)

This however should create a rich condition, not lean so I presume it's not the problem. Exactly

Is your Innovate WB wired as the O2 feed to the ECU, or is it stand alone? It's stand alone.

In your bin file I noticed that the latency vs voltage parameter has been changed from the standard value ..
Maybe that's something to double check, I'm not too familiar with that value but I think the general message was to leave it as is.
I looked inside the Nistune software but i can't find this parameter

I'm sure Matt can help here, or if you like set it yourself and do a testdrive.

voltlatency.JPG
The thing is that i still don't think that unmetered air is coming into the engine. Because this will only happen when @ 0.0/1.0 Bara (-1.0/0.0 Barg).
When i'm driving @ the specific point were the engine is running very bad (around 3200 rpm) the boost pressure is around -0.35 Barg (display on boost controller) when on say 3000 or 3500 rpm the engine is smooth, with almost the same boostpresssure -0.40/-0.30 Barg.

What i'm trying to say is that if there is a leakage, the leakage is always there on not on a specific point. And the data inside the fuel map is not that far away from each other (to compensate for the leakage). And also when the pressure is rising inside the intake to atmospheric pressure, the leakage has to become less.

Correct me if i'm wrong.

But on the other hand we are in the wonderfull world of technical stuff and sometime things work different than we think or expect. :D

Matt
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Re: very lean AFR @ +/-3000-3500 rpm

Post by Matt » Mon Aug 21, 2017 11:12 am

I'm looking at the log playback at the moment. There is about 5 minutes of log to go through and it fluctuates. Some nice areas on cruise mixtures to determine AFRs on cruise as well as several short pulls (runs) usually is what we need to evaluate properly and we don't normally to see idle

Andrew is correct that the tune is lean. I'm seeing around 15:1 AFR on cruise in the short section 1:490.419 (with 4% added fuel FTL trim)


At 2.24.410 trim changes to adding 7% FTL reaching stoich (14.7:1) so you need to increase fueling (K constant) about the same (7%).
RPM=2800, MAF = 2.8V => Injection time = 3.21ms

So the problem area:
At 2.48.215 it is interesting that even at 9% FTL now added that suddently mixtures have done to 17.5:1 (lean)
RPM=3187, MAF = 2.9V => Injection time = 3.14ms

That seems a big drop in your AFRs for only 0.1V of extra airflow (noted injection time is only slightly lower). If you increase fueling at this point to get around 3.21 -3.30ms injection time, what are AFRs then.

Please also check fuel pressure and airleaks... something doesn't seem right
Z32_lean.PNG
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RJBijsterbosch
Posts: 28
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Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Tue Aug 22, 2017 5:05 am

Hello Matt,

Thanks for looking into my issue, and i will try to do the adjustments as you mentioned.

I also will look @ the fuel pressure.

RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Thu Aug 24, 2017 6:09 am

Just to be sure. Performed a smoke test today @ a local workshop to find any leaks in the intake, that i maybe had overlooked.

No leaks found.

The guy who performed the test was a little bit frightend how airtight my car is. Even the screw of the idle control valve was not leaking. that's one of the things thats leaking the most, he said.

So now i'm going to focus on the fuel pressure.

RJBijsterbosch
Posts: 28
Joined: Sat May 20, 2017 1:35 am

Re: very lean AFR @ +/-3000-3500 rpm

Post by RJBijsterbosch » Fri Aug 25, 2017 6:40 pm

I've ckecked the fuel pressure with a pressure transmitter on the FPR.

The fuel pressure looks nice and stable.
2.95 Bar with vacuum hose FPR disconnected @ idle.
2.35 Bar with vacuum hose FPR connected. Vacuum pressure -0.6 Bar. (2.35+ 0.6= 2.95)
2500 RPM : FP 2.56 VP -0.40= 2.96 Bar
3000 RPM : FP 2.55 VP -0.40= 2.95 Bar
3200 RPM : FP 2.77 VP -0.16= 2.93 Bar
3200 RPM : FP 2.90 VP -0.03= 2.93 Bar
3200 RPM : FP 2.80 VP -0.13= 2.93 Bar
3500 RPM : FP 2.71 VP -0.24= 2.95 Bar
4000 RPM : FP 2.51 VP -0.45= 2.96 Bar
WOT : FP 3.75 VP +0.80= 2.95 Bar

Noticing that @ 3200 RPM the engine is unstable, but the fuel pressure is stable @ 2.95 Bar total.

To me the fuel pressure looks OK.

Knowing this, i will try to do adjustmenst to the fuel in NIstune now.

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Re: very lean AFR @ +/-3000-3500 rpm

Post by Matt » Fri Aug 25, 2017 6:43 pm

Watch your injection duty (using Nistune or multimeter) and check if that is increasging inline with your AFRs also

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