Sharktuning experience
 

Hi fellow Rennlisters

I thought I would post my experience (ongoing) of getting to grips with Shark Tuning as I work my way through the process. It might help those thinking about using the useful tool / process or indeed people who are currently using it.

I won't go into a lot of background on the actual product, you can simply visit John Speake's web site JDS Porsche to find out all about the tool. Simple to say that the tool allows you to re-programme the fuel and ignition management maps to alter them to better suit a modified 928.

I went down this route for my S4 as I was changing or modifying cams, headers, inlet manifold, injectors (30 lb design 3) and exhaust so had a heavy requirement to modify the maps.

As my S4 was non cat I needed not only the Shark tuner hardware and software but also a suitable place in the exhaust system to stick the WBO2 sensor. The standard S4 non cat exhaust system did not have anywhere to mount the WB02 sensor however the X pipe I added has a bung right at the cross over which is handy as it captures both cylinder banks.

Having followed the fitting instructions and sourced a windows laptop (at the time my Apple would need a windows emulator to run it) I initially played around with getting to know the screens and functionality. I had not at first changed to the 30lb injectors - those came later.

To describe a little about what this "playing about" entails, basically you have the laptop plugged into the ST via a USB cable and the ST is plugged into the diagnostic port in the car which in turn is connected to the ECUs. The additional exhaust probe is also connected to the ST sending data back to it on how the engine is burning. A neat set up which plays in real time on the laptop as you drive along. You even get a audible ping for knock events which helps you understand exactly where and when a knock occurred. Following the instructions is straight forward and you can immediately change the maps between S4, GT and GTS which are all available as a starting point with the ST.

It took a little time to get to know the screens and read through the instructions which included the principles of what the LH and EZK are doing in relation to the visual maps.

I was able to drive around and record knocks and check the health of my engine. At this point the engine was in standard form except for the x-pipe. With the more or less standard engine I did note that I recorded knocks but these were occasional and in the stage that I would come to learn as 'transitional' stage.

Before I did much more shark tuning the engine received a big upgrade - this was going to test my ability with the shark tuner - thankfully there is always help available from John and Jim not to mention experience from Rennlisters.

The engine received Colins cams (needed change of valve springs), 928 Motorsport headers which I had ceramic coated to Le Mans spec by Camcoat after converting them to work on a RHD car, modified inlet manifold with 30lb injectors and GB oil filler baffle to help control oil in the intake.

The initial challenge with these changes was to change the setting to use the 30lb injectors. Thankfully these are straight forward in the fuel parameters tab in the ST. A few clicks and the engine management system in the car is ready to fire up on completely different injectors which are way ahead of the old style 19lb single pintle injectors.These injectors are the 4 hole narrow plastic body injectors which are more modern. Although only a few clicks are required the ST is doing some clever work to run these injectors.

So how's it coming? You getting it dialed in?

Having only a mechanical fuel injection system in my 928 (79 with K-Jet), I'm curious how the newer EFI 928s manage fuel trim and whether they separate the 2 banks of the V8 (like the flat 6 in my 997 does).

If so, doesn't only monitoring the exhaust at the X-pipe provide you an average where you could have 1 bank running rich and the other lean and everything would look fine according to the readouts from the wideband O2 gauge? If the 928 can't individually manage both banks then this makes sense and is probably as good as one can do, but I was curious.

Thanks.

The system is batch fired so all cylinders get the same fuel even though the air flow varies slightly from runner to runner rev band to rev band so whether it reads from one bank of 4 cylinders or there is a common measurement point really makes little difference to the big picture. I cannot think of any scenario where one bank would be getting ore fuel than the other bank. Having the ability to measure both banks would a plus but not a necessity. Needless to say there is always a scatter of AFR values in any given cell and Sharkplotter calculates the std deviation [scatter] of the results in that cell. Typical std distribution was about 0.4 so I take the point of view that if the SD is greater than that something would not be right. One of the strengths of ST2 is that it is easy to log data and keep it on file so that later runs can be compared.

Fred, thanks a lot for the information and for expanding my knowledge of the 928 :cheers:

I would strongly urge you to install a factory fit Bosch O2 sensor, and then force the system to use the O2 adaption map. It is much better than using the factory CO pot which is used by non cat cars.

Colin,

To date I have only used the ST2 and wideband occasionally and then remove after use. What I try to do is set the CO pot to the null point and then set the idle AFR to 14 as I understand that gives the correct CO value. Interestingly the local police carry out an annual check on older vehicles that includes an exhaust emissions check. I was looking forward to them checking my exhaust last renewal- they took one look at the car and passed it after checking the brakes!

If I understand you note correctly what you are suggesting is to use the WB02 to simulate the NBO2 so that there is a system of dynamic correction all the time. In my case I do not use the WOT maps and instead tune the cruise map high load cells instead- a legacy from when my full throttle switch contact was not working.when I first started using ST2. Opinion on doing this seems mixed. If Marti adopts this it will be interesting to learn what his experience is like.

Fred,

No I am absolutely NOT recommending using the simulated Narrowband O2 sensor signal from the wideband. You MUST install a factory fit bosch O2 sensor and use that for the signal.
Using the WBO2 sensor for a simulated NB signal to the LH will cause all sorts of havoc!

Thanks for that- you recommend using a narrow band sensor and scrap the CO pot approach.

Interesting read. I'm on my way down to Greg Browns in a few hours...for a lesson in Shark tunning. I'm having a breathing issue upon deceleration to the point where the engine will stall. These big motors are heavy breathers and we need to remap or come up with a solution on how to avoid this. It just needs more air.

Continuing on from where I left off..

After changing the setting in the ST to use the 30lb injectors my engine fired up on the first 'hot' crank - I had cranked it without ignition on to build up oil pressure after the cams were changed and to let the cam belt settle to ensure accurate cam timing.

After my engine changes I had to trace an erratic idle which I concluded was due to small air leaks, the throttle not being completely shut (although the TPS was registering idle) and the air filter not being fitted possibly causing uneven airflow across the MAF and the POT idle adjustment being set rich.

The ST has a function called 'Auto tune' which offers live tuning of the fuel map, the ST will adjust the map while just driving the car about. I experimented with this feature for some timing performing a few different drives to see what adjustment it made. I found the function very useful for tuning the cells while the car was at idle, this function helped stabilise the idle on my car.

I was following the principle of tuning the fuel maps (there are multiple maps) first and then move onto advancing the ignition. In order to perform more advanced tuning of the fuel maps it is necessary to use the Shark Plotter function. The Shark Plotter function is a separate programme that you load data into which has been recorded by the ST. Once in the Shark Plotter there are a number of features you can use to customise or auto adjust the fuel maps. There is lots of adjustments that you can make in this programme and it is clearly a step above the 'Auto tune' function which can be considered a basic level of tuning.

The principle is that you record data in the ST which has a data logging function which records a number of parameters including the AFR (air fuel ratio), you can record multiple data logging runs (each recording run is limited to about 8 mins) to build up a more complete picture of your engine running conditions. Those files are saved as txt files. When you save the LH and EZK maps these are saved as bin files.

The Shark Plotter must have both maps loaded into it so it understands what the base maps are that you are using. Then you load in the data logging runs which 'populate' the maps with data. This is then where you see colours appearing in the screen showing the AFR across the maps.

There is standard function in the SP which allows you to auto adjust the fuel map based on the data you have collected, you are also at liberty to manually adjust the map as you see fit. You can see while using this function that it is clearly advantageous to collect multiple data runs to build up a fuller picture of the engine conditions.

In the SP you simply click on the 'auto adjust' and instantly you have you new optimised map.

I had a little difficulty with the next part which Jim helped me out with, that was to get the map from the SP into the ST. I didn't realise that you had to copy and paste the map while the laptop was plugged into the ST and the ignition was switched on, basically it does this in the 'live environment'.

My map received adjustments all over the place but critically was adjusting lean conditions in the 2000 - 2400 area, I was also getting some knocks in this area which I hoped would clean up once the new map was installed.

After uploading the new map I went out doing more data logging and again repeating the cycle of analysing the data in the SP, this time the map was much cleaner and the knocks were gone with the exception of some very low rev, low load knocks which I am attributing to transitional conditions - I will look to see what I can do about these.

Now I could have repeated the logging / adjusting cycle a few times to ensure the fuelling was tweets a little more but I was keen to have a go at adjusting the ignition maps and see how that went. I could also continue to monitor the fuel while playing with the ignition.

So I moved onto playing with the ignition. I took the standard map and stuck 3 degrees on the cruise map from 1200 up to 4800 range from pretty much low load to high load. I went out and tried that setting and did not record any knocks but did notice that the engine was feeling more responsive.

That pretty much takes you up to where I have reached.

Having read instructions and seem some discussion on ST I am expecting knocks will appear around the 3500 - 4200 range if I keep advancing the ignition. I might also expect to add more timing before and after that rev band (being a peak torque band) and only a moderate amount of advance across the peak power band. I have read that as much as 6 degrees can be added before the band which is were I am going next as well as continuing to look at fuelling. I will get a few screen shots along the way and feedback how it goes / feels

In short, never use a WB to feed your car that wants a NB02 sensor.

Its just not the same.

The car runs off the NB, you capture data to adjust the ECU from the WB, thats it.

Idle is tricky. Certainly air leaks, mis-adjusted mechanical stops and flaky idle valves are issues, but the fuel map is a big part of the equation also. There are two separate closed-loop systems working here, and they do interact. The LH idle loop monitors RPM (and the idle switch) to control the ISV valve: If the RPM is low, then increase the ISV airflow, and if the RPM is high then decrease the ISV. Of course the ISV itself doesn't respond instantly to the LH signal, and the engine doesn't respond instantly to airflow changes. So the timing is important-- how far the LH opens the ISV, and how long to wait before starting to close it again. Bosch has carefully tuned the LH for stock motors, but there are few adjustments for idle- it is all "baked into" the firmware.

The second loop is fuel (sometimes called the O2-loop): With a NBO2 sensor, and once warmed up, the LH is also adjusting fuel in response to the NBO2 sensor reading (Sharktuner's "O2-adjust" display). If the NBO2 sensor says "lean" then the lH adds fuel, and vice versa. So the AFR continually cycles a few points either side of the 14.7 "stoich" value. And of course this variation in fueling effects idle speed-- the engine is happiest at around 13:1 AFR, and close to stalling at 15:1).

So you've got these two loops-- idle and fuel-- both messing around with the idle speed, one by changing airflow trying to hold a steady RPM, the other by diddling the fuel up and down trying to mess up the steady RPM. Now add a third variable: A "lumpy" fuel map. As the idle RPM and airflow change, the fueling moves from cell to cell in the fuel map. You can see this with Sharktuner, as the cursor moves around a bit on the fuel map at idle. And if the idle is unstable, then it moves farther around the map. If any of those cells are set too rich or too lean, then that aggravates the stability problem. For example, if the fuel NBO2 sensor says "rich" and the lH reduces fuel, this will drop the RPM a bit. If this moves into a map cell that is itself too lean, then the fuel reduces further and the RPM drops even more. The idle loop then panics and opens the ISV a bunch, moving the fuel back into cells with more fuel which increases RPM further.

So for a stable idle it is important that the fuel map be "flat", not literally the same value but with the cells adjusted for a 14.7:1 AFR. Oh yeah, there is also a delay from engine to NBO2 (and wideband) sensors because the gas flow is very low at idle, and the pipes (especially for modified engines) are large, which means a half-second or so delay. Trying to adjust the fuel map with the idle and fuel loops both active is mostly futile.

Sharktuner provides an option to disable the fueling loop (O2-disable on the fuel-param page), do that for sure. (And disable CO-pot). And there is also a disable option for the idle loop, and manual ISV adjust-- use this to move the engine RPMs up and down around the normal idle range, and adjust the fuel map cells in the idle range for a nice even 14.7:1. (And be sure the wideband is air-cal'ed so that it reads correctly).

Another trick is to copy the block of cells that include the idle area fro the stock map (e.g. below 1200, and below 165 load). Copy that block of cells into your tuned map. Then idle the car and if the AFR is not correct, then adjust that block of cells together, not individually. The values may not be correct but Bosch got the "flatness" right.
Alternately use the stock fuel map as a "reference", and manually adjust the idle of your fuel map to mimic the relative values (higher or lower as needed).

Here is a stock map shown in Sharkplotter, with the general idle area selected. (The red dots are very lean, which is fuel-cutoff on overrun). Notice how the cell values vary smoothly, no individual cells which are much different than their neighbors.

https://cimg6.ibsrv.net/gimg/rennlis...9beaeb3a64.png

Here's a stock fuel map shown in SP (no log data), with the O2-adjust limits outlined and shaded gray:

https://cimg6.ibsrv.net/gimg/rennlis...62ba009800.png

Within that shaded area the O2-loop (fuel loop) is active, and the LH is running closed-loop and adjusting the fueling to stoich (14.7:1) per the NBo2 sensor. The real-time adjustment is the "O2-adjust" value shown in Sharktuner, and the long-term average is saved as an "O2-adaptation" value. (Two values, actually). For example, if the real-time O2-adjust is moving around between say +6 and +14% (i.e. adding an average of 10% more fuel), then the O2-adaptation values will gradually change to +10% and the real-time O2-adjust will then be moving between -4% and +4%. As the MAF ages over time then it tends to read less airflow, and the O2-adaptation value will trend more positive, to the max of +20%.

Outside that shaded area the O2/fuel loop is shut off (i.e. the LH is running open-loop), with the fueling determined by the map values alone (plus O2-adaptation).

Now here's a plot from our '88s4 with the NBo2 active-area adjusted. I don't particularly want the LH runing closed-loop and 14.7:1 AFR at high loads and low RPM, so I adjusted the limits with Sharktuner to cut it off at load 165 and let it run open-loop for loads above that.

https://cimg5.ibsrv.net/gimg/rennlis...2b5b194de4.png

The large dots in Sharkplotter are open-loop, the small dots are closed-loop. As you can see the boundary is not perfect, there are some timing delays in LH when things are changing fast. But generally, "inside the box" the LH running closed-loop and continuously adjusting the fueling.