much to rich under soft acceleration - Z32AFM on SR20DET

Benne · Post by **Benne** » Thu Jun 11, 2009 11:37 pm

hi there,

I swapped to the Z32 AFM on my 2001 Silvia.
It wasn´t a problem, choosed Z32 from AFM Menu, K-Const raised from 27550 to 47500. All was fine, car idled around 15.0 AFR, full throttle around 10.5 AFR.
But under soft accelaration, when engine speeds ~ 3500 rpm or a bit higher it is immediatly also around 10.2. to 10.6... why??
Fuel map says, it should be 12-13 AFR.

Using Nistune 0.9.6b

sorry for bad english!

greetz,
Benne

Benne · Post by **Benne** » Fri Jun 12, 2009 12:12 am

I compared the MAF Translation of stock AFM with Z32 AFM.

Thougt they were much more different...

Matt · Post by **Matt** » Fri Jun 12, 2009 1:21 am

the injection multiplier (k constant) adjustment which gets made as a result of airflow differences between the two is fairly large, the VQ map is just a calibration curve, but on the Z32 actually represents a larger airflow scale (as % of total airflow)

Benne · Post by **Benne** » Fri Jun 12, 2009 1:36 am

ok, thanx Matt.

So there must be another reason why the car is running to rich under soft accelaration...

PL · Post by PL » Fri Jun 12, 2009 12:11 pm

You're probably suffering from reversion. Z32 AFM's are noted for it. It's all do do with disturbances in the airflow at low load/idle. And it can cause some very wierd (and varying) symptoms. I've seen it mostly on engine conversions where the AFM is placed too close to the turbo. One car would hardly even run (V rich) at idle and low load but was fine at full load. Changed the plumbing between AFM and turbo and it ran perfectly.

Things to check are that the AFM is as far as possible from the turbo and that all piping is smooth, with a lack of sharp bends and abrupt changes in diameter. Ideally you'll also have a "bellmouth" where the AFM goes into the air filter too.

Also make sure you have a recirculating BOV fitted. Make sure that the fitting where the air returns to turbo is angled towards turbo (ie: away from AFM).

PL

Benne · Post by **Benne** » Fri Jun 12, 2009 6:34 pm

I installed the Apex Performance Conversion Pipe:

with the Apexi Filter Head:

Thougt it should work fine

The stock recirculating BOV is also still fitted, not an open BOV.

PL · Post by PL » Fri Jun 12, 2009 7:20 pm

I'm not keen on that bend straight out of the AFM but it should be OK.

I've had another thought though. You've only changed AFM yes? Standard injectors?? If this is so then your K constant will be very large. So unless the load scales have been adjusted, your ECU will be accessing the load columns over on the right as soon as boost comes up. Watch the maptrace as the car comes on boost. If it slams straight across to the last column then you'll need to adjust the load scales.

There's information in the Tuning Basics document that covers this. It's very easy to do.

English : http://www.plmsdevelopments.com/files/n ... basics.pdf

German : http://www.nistune.com/german_docs/niss ... german.pdf

Hope this helps.

PL

Benne · Post by **Benne** » Fri Jun 12, 2009 7:56 pm

Yes, I´ve only changed the AFM, injectors are stock (480cc I think).
K-constant is 47500.
Load scales have not been adjusted yet.
Looks like thats not necessary cause there´s only 0.9 bar of boost.
But I´ll check again today.

Thanks!!

Benne · Post by **Benne** » Fri Jun 12, 2009 11:33 pm

Back from the Autobahn...

Load scales fit.

And I´ve found my mistake...

Last week I only adjusted the K-constant by unchecking the O2-tip in the menu DTC Flags.

Now I have done it by marking the cells and pressing "O" for disabling the O2 Feedback.... Car idled around 12.5 AFR

Adjusted K-CONST to 41750 brought idle to around 14.5 and sweet 12-5 to 13 AFR under soft accelartion, wot is 10.7 to 11.0
Now its like it has to be.

What I´ve learned:
Reading the manual carefully is advantageous

Matt · Post by **Matt** » Sat Jun 13, 2009 1:48 am

'DTC flags' is for turning off reporting of particular Diagnostic Terminal Codes

You should be using 'feedback switch' and then 'O2 sensor' this should have the same effect as disabling all the O2 feedback in the map

if you monitor O2 feedback guage then you will see it change when feedback is enabled

Benne · Post by **Benne** » Sat Jun 13, 2009 6:30 pm

Of course feedback switch! That´s what I meant.
It doesn´t work...

I had to work with disabling the O2 feedback in the fuel map.
That works.

Matt · Post by **Matt** » Sat Jun 13, 2009 11:49 pm

hmmmm interesting. it should work.... I'll check it out

Benne · Post by **Benne** » Fri Jul 10, 2009 10:54 pm

I found a second reason why the mixture was getting to rich.

The engine gets much to hot!
S14 do have a thicker radiator (25mm, my S15 has a 15mm) and there´s an electric fan between radiator an viscous fan.
My S15 has only the viscous type.

I had 133-137°C water temp logged by Nistune on the Hockenheim Racetrack 2 weeks ago!

Is there a table that shows how much ECU injects more when water temp is above 100°C?

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