I have searched and found some seemingly related scenarios, but not definitive. I have been working on MAF calibration. The issue is unpredictable AFR's in open loop. In closed loop things are fine, as one would expect with sensor feedback. In open loop I have different scenarios:

Scenario 1: Easing slowly to around 6K-6.5K RPM at which point the car will hesitate and AFR's will shoot up as high as 16-17. 1'st gear is the worst, with subsequent gears getting less pronounced.

Scenario 2: During WOT, or near-WOT, acceleration the car will transition from CL to OL just fine. I have gotten the MAF scale to the point where expected AFR and logged AFR are close, if not right on.

Scenario 3: WOT to redline sometimes will result in sputter, but very rarely.

Here are the previous mods before the problem:

1) MS CAI
2) MS Catback
3) Agency Power midpipe

Here are the mods made just before the problem:

1) Uncapped cleaned and tested stock yellow injectors, scaled in ATR
2) Cleaned and flow tested red injectors, scaled in ATR
3) BHR ignition coils with new plugs and wires
4) Walbro 255 fuel pump
5) ACT 6 puck and Prolite flywheel (I don't expect this to be of consequence, rather listed for completeness)

I have triple checked the injector wiring and the plug wiring. I have played with the MAF scaling. The results are unpredictable. When slowly accelerating AFR's shoot thru the roof around 6500 RPM and the car hesitates and jerks. When accelerating rapidly AFR's seem to match what is expected, for the most part. I even replaced the MAF as part of my troubleshooting. Not quite sure about the rare high RPM >9K sputter yet.

Why the difference in AFR's when slow or fast acceleration?

Thanks,

Jason

 

Why are you running uncapped injectors on a NA engine? Have you tried re-flashing to the stock map? A little knowledge can be dangerous.

 

Also, reflashing stock map will result in very rich condition in OL, since uncapped injector report shows they flow almost twice as much as stock.

 

Uncapped injectors are prep for boost.

 

Bad idea IMO to run them on an NA engine, worry about upgrading injectors when your boosted.

 

Again, uncapped injectors are in prep for boost. Turblown kit is being built. Besides, even boosted applications run at N/A levels when not in boost. Injector capacity should not make a difference when properly tuned.

 

To clarify: The real issue I am after here is why would a slow acel result in lean condition at CL/OL transition, when quick acel results in smooth transition. The sputter at high RPM has been extremely rare, but could be worth mentioning, so I included for completeness.

 

Run at NA levels? What does that mean? A boosted 8 will run like crap on a NA tune even if you are not in boost. Like I said, a little knowledge can be a dangerous thing.

I suggest contacting Kane at www.ppo2performance.com to get a handle on this tuning for you. He will teach/show you what you are missing to get you straightened out.

 

The APV opens at 6250 rpm
This is likely the reason you are getting a lean spike.

Most people compensate for this in the fuel tables.

 

not completely related but still interesting:
http://www.injectordynamics.com/Dril...dDipshits.html

 

Great read, thanks man.
Can't wait to remove my uncapped yellows.
BumblebeeRX8 is making us a super secret fuelling project to replace the fuel pump, rail and injectors

However ... The uncapped or drilled yellows are typically put in the P2 position so I wonder (doubt) if they are ever in a state where they need to operate at a low pulse width.

IIRC that 4 other injectors also firing by the time the P2's are operating, which would reduce the drilled injectors error as they are only 2 of the 6 working injectors.


mmmmmmmm still digesting this

 

Thanks WCS, I will look into that.

 

I appreciate your effort trying to help but you are not understanding what I am saying. I am not suggesting an N/A tune for a boosted 8. What I am saying is a boosted car does not always run in boost. While in vacuum the fueling is similar to that of an N/A tune, but you still need more injector capacity for when you are in boost. The ECU handles this. So my point is that it is fine to run larger injectors on an N/A car, albeit pointless if the car were never to be boosted, but that is what I am working towards. As long as the ECU is aware of the injector capacities and other characteristics it will compensate for the size while not in boost. Make sense?

 

Thanks for this. I haven't completey accepted that the uncapped injectors don't have anything to do with the issue. If nothing else seems to resolve the issue I may just swap them out.

 

Curious, are you saying you can't wait to remove yours because they are causing problems or because of the new solution? If they are causing you problems, what has been your experience?

 

LOL
Slash hahahah dude ... it's easier to read if you use the "+ quote" button in the threads so you don't have to post 4 times over.
Seeing this honestly made me LOL

Yes I can't wait to remove them and implement the new solution.

It seems to all do with latency with these injectors. We'll see what happens.

This is the way I scaled my injectors.
9k is a pretty big head around here so I wouldn't suggest getting in a pissing match.
To each there own.

 

WCS, thanks for the help. You are one of the few people that I see posting helpful advice without being a ***** and I appreciate it :-)

I am using the forum's mobile theme on my phone and unfortunately there is only a quote button, not +quote. I'll just reply without quoting from now on.

As for 9k, I've witnessed plenty of other "big heads" on the forum. If they have something useful to say I listen, the rest I just filter them out :-)

 

ACK!
I hate the mobile theme thing

and Thanks ...

Check RIWWP he's got a lot great stuff.

I reference his New and Potential owners thread all the time ... just for me!
You've prolly seen it but just in case

https://www.rx8club.com/new-member-forum-197/new-potential-owners-start-here-202454/

 

Will do, appreciate it!

To be fair to 9k, I got the impression he was trying to help, but probably not understanding what I was saying. Or maybe it was poor explanation on my part. At any rate, this thread has been helpful for me overall. I had read about the APV's coming on being a cause for lean spikes, but I was struggling with why it would only happen with slow acceleration thru CL/OL transition. Faster acceleration is smooth. I will keep at it.

 

Well ... slow acceleration is the bitch now isn't it ...

Because at "slow" acceleration you calculated load, rpm and afr and maf readings could be .... well whatever

At WOT there tends to be a typical pattern and things you should expect at certain points.
But partial throttle is always harder to tune.
If I was you and I was having problems with that zone I would:

Take the following cruise logs at 10 seconds logs
5000 rpm
5500 rpm
6000 rpm
6500 rpm
7000 rpm

If you are producing the same afr that is being called on those cruise logs, your maf is pretty close to being scaled at those g/s areas

If you're out in this area you need to either adjust the Maf, Fuel VE or Injector Scaling (if you've changed injectors)

 

Good stuff. In my logging attempts to date I have mostly followed the MM collection method for his tuning service. I will try your suggestions.

I tried a quick test to see if APV was part of the problem. I made a copy of my current settings but raised APV open RPMs to 9000. Got same behavior in 6K-6.5K RPM range. I'll keep at it...