John Speake

I recently had a query as to whether someone with a modified 928 engine needed a SMAF due to the power he is making.

This post is to clarify this aspect.

A good rule of thumb is that a SMAF is not required until crank HP reaches around 425HP.

The way to determine it better is to data log a WOT run up to maximum power and monitor "MAF signal%" with the SharkTuner datalogger. It is only when that signal approaches 100% that a SMAF is required for accurate mapping.

If you also data log "MAF voltage" you may see the MAF volts max out at 5.1v at the power rises. This is due to the analog to digital convertor that processes MAF volts in the LH ECU maxing out.

However we have used another measuring circuit in the LH ECU to extend this range up to an effective MAF voltage of 6.1v. It is this 6.1v that represents 100% of "MAF signal %"

I hope this clarifies this topic. I will add an amendment to the USer Manual in due course.

It may possible to use one of Tim Murphy's MAF restrictors in place of the SMAF but I have not evalutated one myself.

AO

John-

One other point worth mentioning is that this is if you have a signle thottle body. In DR's kits, he uses twin throttle bodies, so essentially only 1/2 the airflow is metered.

So using your 425 crank HP number... I shouldn't need a Super MAF until I hit 850 HP!

John Speake

That's true for a setup like DR's of course.....

850HP ! Go for it Andrew

Darien

In case I missed it, the SMAF is still only applicable to later 32V Sharks (S4/GT's), correct??

Shane

Yes it is so I guess you'll be needing one now for your S4...

John Speake

We might be able to do something, but probably the easiest would be to use a Tim Murphy restrictor.

We've been very busy lately....... announcement coming soon...... :-)

6.0-928S

Shark tuner announcement? Say yes......

Hammer

BrianG

Sweet!!!!

Kevin Michael

John how much is a SMAF if I send you a good core ( or two if that makes it even sweeter!)
Kevin

John Speake

If the core is near calibration, then the price is 100USD. If the core needs a rebuild, then 350 +100USD.

Louie928

Hi,
I thought I'd chime in on this SMAF thread with some info I gleaned while tuning Jim Hurtt's '90GT TS engine fitted with a SMAF. I explained the general SC installation on the Twin Screw thread, and will try to keep to the tuning experience here although some of the build details should be explained. The engine has 42 Lb Ford/Bosch gree injectors. I changed the fuel system somewhat by switching to stainless lines and AN fittings. I mounted the fuel pressure regulator to the top of the firewall on the left side for easy access for pressure changes and mounting of a fuel pressure sensor for an inside the car electric fuel pressure gauge. I used an Aeromotive brand fuel pressure regulator from Summit Racing. It has ports for two inlet lines, and one bypass outlet line just like the stock regulator as well as ports for intake manifold pressure and a fuel pressure sensor. I did not use the fuel pressure damper that is mounted near the left rear fuel rail. An AN -6 like goes from the rear of each fuel rail to the input side of the regulator. The output of the regulator goes to the normal fuel return line at the center rear of the firewall. Metric to AN adapter fittings are used where the transition from metric to AN size is required. Those adapters are availabe from British American Transfer, BAT.com. I retained the fuel pressure dampener at the front where the fuel inlet is. I'm not sure if it is actually required, but left it anyway mostly to simplify fuel connections. Jumper the fuel pump relay to run the pump and set the fuel pressure regulator to stock pressure. That would be about 53 psi with the engine not running. With the ST, and proper injector sizing, there is no need to stray away from stock fuel pressure or use a goofy pressure increasing type regulator. In fact, a stock fuel pressure regulator will work fine.

The first thing I did before running the engine was to burn an EZ-K chip with retarded timing so I could tune the LH without the ignition timing being too far advanced for boost. With the ST connected to the EZ-K, and the base map up for the GT, I started at about the 50% load point and reduced all RPMs (the entire load row) by 0.8 degrees. That's two clicks on the single "-" button with the entire row selected. Select the next row down and do the same except this time use 3 clicks for a 1.2 degree retard from normal timing. Go on down to the bottom (100% load) row retarding in increasing steps to have about 9 degrees retard all across for that row. I was striving for a gradual timing retard at above 50% load to end up at 9 degrees retard at full load. This more or less conformed to the rule-of-thumb 1 degree retard fo reach pound of boost theory. It turned out to be pretty close except I should have retarded more than the 9 degrees on the initial EZ chip.

With the retarded timing chip in the EZ, connect the ST to the LH. Load in the base map for a SuperMAF, and configure the ST software for the 42 lb injectors. I left the rev limit as it was, but changed the RPM where fuel injection is changed from once per revolution to once every other revolution to a high RPM that would never be reached. The reasoning behind that is because with the 42 lb injectors and power level I expected, the injector duty cycle wouldn't get so high as to need going to injection every other revolution. Also, without the rear fuel pressure dampener, I didn't want excessively long injector on time. I thought the injector cycle every revolution may keep a more constant fuel pressure. Injector duty cycle never exceeded 75% so this setting is really ok. The 928 warmup map keeps the engine quite rich during warmup so I usually go to that map and lean it out some. You don't need any extra enrichment with engine temp above 20C and reduce the enrichment below that by 10% or so. Go to the WOT map and put zeros in all the cells. The SuperMAF along with the SuperMAF base map provide plenty of capability for fuel even at WOT. I use the base map to tune at part throttle and WOT and would rather do that than to try an compensate in the base map for some enrichment when the WOT switches on. One less variable to deal with when the WOT map is zeros.

Start the engine and surprise, surprise! It runs and runs quite well on the base map and compensations John has engineered in for the 42 lb injectors. I did some Autotune at idle and part throttle. I found it best to manually touch up cells for final settings at idle and low loads. Watch the O2 correction and change throttle and RPM so you pass through a lot of cells. When the O2 correction changes more than a few % quickly look to see what cell it is on and also surrounding cells too. The LH uses values in surrounding cells as well as the cell it is on to determine the pulse width. Sometimes you see adjacent cells with large negative number right next to cells with large positive numbers. The LH may appear to work ok and give an acceptable mixture, but it is likely because it is averaging between widely different cell values. You can usually work the adjacent cell values up/down to achieve a smoother map and achieve more consistent mixture while the RPM/load works its way through the map. At idle, put the car in gear with the brake on and slip the clutch to load the engine and get idle to go to a low RPM as if it is bogging down. Check the mixture and the cells it goes to down in the lower left corner. Change those cells so the mixture doesn’t go too rich or lean when the engine is having trouble keeping a constant idle RPM. Carefully give a tiny bit of throttle as if the idle RPM was a bit too high and check those cells too. Get the cell values worked out for very minimum O2 % correction in the cell group that is diagonal upper right to lower left of the cells used at normal idle. This can take a very long time over several sessions. The end result is worth it.

Next do some actual tuning under load. I use a throttle stop so I can make repeated runs logging the results and be assured I was at the same throttle opening. Log RPM, MAF load, O2 correction, throttle position, mixture, and whatever else you want. At low loads, the LH will be in closed loop unless at RPM above around 4500 and you won’t be able to do much about the mixture. What you can, and should, do is to monitor the O2 correction at various RPM/MAF load values to be sure O2 correction is low. I try to stay to less than 5% correction. Check the map too for any big + or – numbers close together. Try to smooth those out. Advance on to a slightly higher throttle opening and do it all over again. When you get to about ½ throttle, I was getting into boost on Jims car and this is where I had some difficulty. I wanted a slightly richer mixture than what I was getting. I spent a lot of time trying to adjust mixture below about 4500 RPM but ended up being unsuccessful. Above 4500, no problem. The logged data showed O2 correction to be zero and I thought it was in open loop, but finally concluded that somehow the LH was still using some O2 correction to control mixture. You can see some correction happening if you look at the O2 correction on the fuel map page when you are not logging data. The mixture wasn’t horribly leaner than I wanted, but below 4500 RPM, I couldn’t change it much. I think the situation was that with the supercharger, I was into boost and the engine was under load except that the WOT switch had not activated and forced the LH into open loop. I needed an artificial WOT switch to get the LH to go to open loop. I didn’t do anything about it, but came up with a couple ideas that might work. One is to use a pressure switch so that at above about 2 psi boost the switch closes. Wire the switch across the WOT switch wires to the LH. That way whenever there is more than 2 psi boost, the LH will go to open loop. You have the WOT map with zeros so there will be no problem with that extra enrichment fouling up your normal bas map values. Another possibility is to use the LH flappy control output to trigger a relay to substitute for the WOT switch. The ST allows the point of flappy operation to be user settable in both RPM and load and I think that would work fine. I didn’t think of these ideas until I was through tuning and didn’t try them. Again, the mixture is tunable above 4500 RPM at ½ throttle and above so it isn’t a huge deal other than spending a lot of time trying to tune mixture below 4500 when you don’t know that it is near impossible.

Work your way up in throttle opening tuning all the way to the top at whatever load/RPM values you log. The base SuperMAF map was plenty rich at the top end at about 11:1 AFR. I wanted around 13.2 to 13.5 AFR so I leaned it. The max load values were around 165 to 175 while the max load row on the map is 236. Even at 500 rwhp, there is still a lot of load left on the Super MAF tuning map.

When you are done with the LH tuning, burn a chip for the LH and move on over to the EZ-K. You can start with the retarded timing map you used for the retarded timing chip, or you can use the standard base map. The standard base map will be fine for low loads, but be aware that it will have too much advance when boost comes up so no throttle jabs if you start with the normal base map. Do the same mechanical throttle stop tuning on the EZ as you did on the LH. Log RPM, MAF load, Ign advance, knock count and knocks for all 8 cyl. You can log mixture too just to double check the mixture tuning. Set the throttle stop for about 40% and go through a run up to about 4000 RPM. At this low of throttle, it’ll not be of much use to try to go to high RPM. Check for knocks. If none, you could advance timing a little at the logged RPM and load cells, but I’ve noticed on the dyno that there is little to be gained at low loads by advancing the timing beyond the values in the normal base map. Go up 10% in throttle opening. Measure the throttle arm movement from idle to full throttle and see what the total movement is, then you can calculate what each 10% movement is so you know how much to increase the stop. Make another run and check the logged values and knocks. Soon you’ll see knock show up, and you’ll be able to see what cylinders are knocking and at what RPM and load. Retard timing at those cells and do another run. Try to get the total knock count down to 5 or maybe 8 knocks. You’ll see that at each knock, the EZ will retard timing on one, or more cylinders. The retard will gradually step downwards until it is back to zero retard again. The point is that at each knock, you get retarded timing and resultant power loss. There is a balance between having too little advance and no knocks, and too much advance and a lot of knocks and resultant retards. 5 to 8 knocks over a 10 second period seem to be an ok amount. I did this on a dyno and could monitor power as I was setting timing, but you don’t absolutely need the dyno. It is sure safer and quicker though and probably a good investment in time and money to rent one for a few (or a lot of) hours.

On Jim’s engine with the twin screw, I noticed that I’d consistently get cyl #1 and #8 knocking first with #4 and #5 a close second. Thinking about that, I believe the center cylinders can get more fuel because each of the center cylinders have an injector on each side of them. The TS intake is open inside with no runners or channels to keep fuel from one cylinder entirely away from other cylinders. The center cylinders can rob fuel from the end cylinders, but the end cylinders have only one adjacent cyl. The batch fire injectors throw all the fuel in at once, but each cyl gets whatever fuel is in the cloud as its intake valve opens. It’s only a theory. Something is doing it. It would be great to have individual injector pulse width tailoring, but not possible with batch fire. Individual cylinder timing should help too.

I made some changes to the EZ-K configuration using the tools John has provided in the ST on the Parameters page. The stock values for the knock senses timing retard is 3 degrees per knock sense, 10 seconds for recovery. I reduced the retard when knock is detected to 1.5 degrees, and the recovery time to 3 seconds. I felt that the timing retard was too much when a knock was sensed and cost some power. The quicker recovery didn’t keep the retarded timing for so long and that didn’t seem to give me multiple retards after the first, so probably ok. There are more parameters for transient conditions and I changed those a little too. There is retard when the throttle is opened from idle. That would be as if you snapped it open. I reduced that from 5.6 degrees to around 2.5 degrees. You can log knocks, then pop the throttle open for a see how many knocks you get. Increase, or reduce this value so you don’t get knock on throttle opening. Less retard here makes the engine more “snappy” on throttle opening. It’s a good thing. Do the same with the throttle advance under load value. I reduced that a little too, as well as increasing the advance increase rate to about 2 deg per spark. These are all designed to not have knocks under rapid throttle changes so make some changes, experiment a little, and monitor the results.

I noticed that I ran out of EZ load range in the map. John sent me another map set, which took care of the problem. The EZ gets it’s load value from the LH so it required both new maps. I presume John will make those generally available, or have them available upon request.

As a final note, many thinks to John for developing not only the Sharktuner, but also to go another step and have the SuperMAF along with the settings available for increased injector sizes to give us the ability to tune to almost double the stock power output. Even more if you wanted to push more from the 928 than this relatively modest effort. Jim’s car runs extremely smoothly at all RPMs and loads. You’d never know what’s under the hood until pressing on the go pedal. The end result is that he has 502 rwhp (SAE corrected), 400 to 450+ lb ft of very flat torque, whenever he wants at about 9.5 psi boost. The final timing was about 16-17 degrees advance at the top end at full load. I think the stock timing is around 28 to 30 degrees. There are quite a few boosted cars at higher levels than Jim’s and they have not tuned timing apparently depending on the knock sensors and prayer to keep their engine together. The EZ-K has extremely conservative parameters with stock settings so you can stay lucky for a while. This was not an easy thing to do and it took some time. I’m just glad we can do it. I spent more than a week of part days and 23 gals of fuel all on the dyno. Was it worth it? Not an option in my book, sure it was.

Edit to add that I disconnected the WOT switch wire at the EZ plug. All timing tuning above idle is done on the main (cruise) map. Full scale is 100% and I used up to 87 - 90%

Louie

John Speake

Thanks Louie for an excellent description of tuning a twinscrew engine !

Because the t/s generates lots of boost at low rpm, the tuning requirements of the EZK are rather different to those for centrifugal s/c. When we created SMAF maps we did not change the load output signal that is fed to the EZK.

Louie found with a twinscrew that he was hitting 100% load on EZK at about 50% load values on the SMAF map. So Niklas created a special LH map and also a special EZK map. These MUST be used together and are not compatable with the stock LH, SMAF or EZK maps.

These maps are available on request, you can cut and pasted previously mapped SMAF values into the new bin file, then tune the EZK as Louie suggests.

I agree with Louie that the knock system retards in rather large steps, also the recovery time is much too long. These can be usefully modified with the ST.

Many thanks to Niklas for responding quickly with modified files, and to Louie for his insightful analsysis of the problems encountered.

Rick Carter

Thank you for the insight Louie and John. How much of this carries over to the 85/86 32v as we don't have the 87+ maps?

John Speake

Hi Rick
I would say the general principles of tuning are the same when applied to LH2.2/EZ-F.

For serious boost on an 85/86, I would strongly recommend fitting a knock detection system, such as the Knocklite, as Porken has. This will aid safe EZF mapping, and can also be used to automatically add more retard as Ken has outlined.

Rick Carter

Thanks John,
I understand the general principles are the same and have followed the two Ken's posts. My question has more to do with the limitations of the LH2.2 maps and available options.