bd0nalds0n

At the risk of derailing a separate thread where I've chronicled my difficulties with Sharktuning (and I will go back there and fill in the blanks), I just wanted to share all the ground I managed to cover yesterday.

I've had troubles with vastly different readings from my NB and WB 02 sensors mounted in each bank of the X pipe. This made tuning with the Sharktuner difficult and with poor results. I had a bad idle, what sounded like misfires, and a lot of bucking and humping when trying to tune at higher loads.

I reversed the locations of the WB and NB sensor and suddenly I was getting good AFRs from the WB. So that meant the richness was coming from the passenger bank, and confirmed that the thought that one side was running richer than the other was justified.

I have new 42lb injectors and figured at least one was flowing much faster than the others. So I decided to pull the plugs to see if I could see which hole was rich.

I found one spark plug with the prong bent to the point it was touching the electrode. This was the source of misfires, overall bad running and poor idle conditions, and the rich condition on the passenger bank.

Replaced the plugs and voila! The LH was a snap, an absolute snap to tune via the sharktuner. Louie was kind enough to provide an ignition map for a similarly configured car, and I don't get any knocks. None. I'm running a thicker Cometic gasket so I probably have a bit of room to add some advance back in due to the lower CR, because I don't think the goal is to completely eliminate them, just to make sure they're managable by the EZK. Not sure where to begin with that one.

I recharged my laptop then went out for another series of runs last night using the SharkPlotter. What a great companion program! Although my data logging seems to crap out much faster than 8 minutes??

Anyway, after logging and plotting data on the sharkplotter, I was able to more finely tune the fuel map. The car is very, very well behaved at idle and just off-idle. Not sure if it can be improved upon, but I'm going to gather a lot more data points and see if I can't refine it even further. The car runs absolutely fantastic, and so far I've only run it in open loop mode.

In my previous post, I was complaining about how I'd had such good results with the S3 FPR, BEGI bost adjustable FPR, and 30# injectors and that my shartuning efforts had been frustrating.

Once I diagnosed and fixed the problem that was casing the erratic running conditions and readings from the diagnostic equipment, everything moved along quickly and painlessly.

I am absolutely gushing about the simplicity and effectiveness of using these two pieces of technology. I was really getting frustrated and depressed, it's amazing how quickly things can change once you make a critical breakthrough, and sometimes those breakthroughs arise from the simplest of circumstances.

The 928 has been pretty much no-op since last fall. It's nice to have most of the mechanical issues sorted. There are a few interior things to get sorted, then I'll be almost completely dialed in. Victory at last.

jcorenman

Brian,

It is great to hear that you found the problem!

The ST's logging limit is 5000 lines, at 10/sec that would 500 seconds or a bit over 8 min's. If you log at 20/sec then the buffer would fill up in about half that, plus/minus whether the ST2 can keep up with 20 samples/sec, which depends on how many variables you are logging. (If ST can't keep then it just gracefully skips some samples).

Expanding ST's logging buffer is high on John & Niklas' to-do list.

Mrmerlin

glad you found a problem and got it corrected.
Now the fun begins

dprantl

Yes, my car has been running MUCH better since I've been using the ST2 on it. Only problem is the car is making too much power for its own good at the moment. But before I started tuning it, it was in a really bad state of tune. Knock counts were through the roof and the mixture was too lean at low RPM and super rich (like slightly less than 10:1) in the mid/upper range. This just goes to show that you just can't change the top pulley size from 2.75" to 2.25" without changing the tune, bad PO

The only issue I ran into with the ST that took me a while to figure out was that when you are in an autotune WOT session, the ST works only off the base map itself. If you have set any values in the WOT map, for some reason those are ignored during the WOT autotune. I kept getting red 127 cells so I kept increasing the wot map more and more without any effect. So then I tried to do a WOT run without autotune and the car lost all power because the mixture was so rich. I verified this by doing a WOT run in autotune and getting a repeatable 13:1, then 30 seconds later I turned off autotune to do the same run and watched as the AFR went below so far below 10:1 that the car lost power.

Dan
'91 928GT S/C 475hp/460lb.ft

aggravation

Where does one get the "SharkPlotter"? I don't see it on the JDSPorsche web site....
I'm on the verge of tuning my WOT map and it sounds like it might keep me out of the ditch and/or jail since I'll be doing it alone.

Tony

Good job Brian! It sucks when you can chase your tail tyring to find a solution to a problem and it turns out to be so simple at times...yet hard to find!

While one would think that using the sensors in two differnt exhaust streams would be a bad idea, it actually helped you find an issue you probably would have never come across other wise.

jcorenman

Jail bad, ditch worse. http://sharkplotter.com

If you have an ST1 send me a PM or email (support-at-sharkplotter-dot-com) for a registration code.

See this thread also: https://rennlist.com/forums/928-foru...er-thread.html

Cheers, Jim

jcorenman

Dan, good info on autotune and the WOT map, I was surprised but then checked the ST manual and it actually says that
(Paragraph 3 under "AUTOTUNE WOT REMAPPING" in the "Autotune quick-start" section).

But is it necessary (or even desirable) to use the WOT map at all? For NA cars at least, it works quite well to zero out the WOT map and then do all the fuel tuning from the main map. There's nothing special about WOT other than higher loads, and the MAF (assuming it is not max'ed out) measures the load directly. So if you want a richer mixture at higher loads, just increase the fuel for those cells in the main map.

Wouldn't the same be true for SC engines, that all the fuel tuning could be done with the base map? Or am I missing something?

Sharkplotter doesn't provide a way to separately adjust the WOT map either. It could be done but adds another layer of complication.

(P.S. Cross-posted this to the "Official SharkPlotter thread" for general interest and to avoid taking Brian's thread too far off-topic)

Stan.Shaw@Excell.Net

Wow, can't believe I am going to be the first to question why this is not good

dprantl

Well, the WOT map is useful when you are reaching the limits of the injectors. Of course the correct solution is to get larger injectors, but for now I need a short-term solution. I guess I could always fool the LH into thinking it has smaller injectors on the fuel parameters menu...

Dan
'91 928GT S/C 475hp/460lb.ft

IcemanG17

good to hear......I'll be tuning the widow soon, but since its still a stock internal + exhaust motor it doesn't need as much tuning....but I'm sure it will be interesting

jcorenman

Check the injector duty-cycle (one of the logged variables), I think you want to keep it below 80% or so at max load. If that's the case then you don't need larger injectors. But if the map values are reaching +127 then you may need to set a smaller injector size as you said, in order to get more fuel.

jcorenman

All the usual comedians are over in the "delete" thread??

AO

He's something that might be of use to the twin-screw guys in particular and maybe some of the CS guys too.

I am using DR's "Power Boost Module." It's basically a pressure switch that is activated as soon as you hit boost. You splice it into your LH's WOT line. So, whenever you go into boost, it tricks the LH into going into the WOT enrichment mode. For me, it eliminated any and all tip in and drops you into the right fuel range as soon as you hit boost.

Now as for tuning. I found that all I needed to tune was the cruise map and pretty much leave the WOT enrinchment values as they were (they're easy enough to tweak as they're only RPM based).

Just a thought if you're still struggling with transitions into boost (and WOT).

John Speake

Hello Brian
Very pleased to hear you have found the issue with your car, and come to a satisfacory conclusion (or perhaps just the beginning of the quest for the "ideal maps" ?) :-)