MegaSquirt Tuning

[PKD]

Hey all, started to work on Megasquirt tuning. Currently my fuel/air ratio's are way to rich. It would take about 30sec with the garage door to earn you wings. . if you know what I mean. Stopping at a light in traffic could turn you green. My car is a 1976 Datsun 280Z. The engine is a L28 out of a 82 280ZX turbo completely rebuilt with a new turbo. The air/fuel ratio was running in the 16.5 to 18 range at idle(800rpm's) Cough Cough. What level should I be at? I have seen on some U-tube videos that they run between 10 and 13. At the same time, what temp should the engine be running at? 160? 170? 180? We tinkered with it a little, the following screenshot was where we were at when we shut it down for the day. we ended up getting the fuel ration down to 12 to 13. We bottomed it out at 10 when the temp started to go up to 185. We increased the levels and got it back up to 12 to 13 with temp at 176. following pic was screen shot of where we stopped. Also some pic's of under the hood.

Some spec's:  Running a MS3Pro-ECU,  Delphi Fuel Injectors Low Impedance 55lb/hr at 43.5 psi.  Currently running 40psi at fuel regulator,  Turbonetics turbo,  JE flat top pistons with a bore 3.425(86.99mm)

[JSM]

Might want to post on hybridz.org. You probably get some good insight. 

Build looks good. Seems you got most of the hard part sorted. 

[Zed Head]

An AFR of 18 is super lean.  Coughing (unburnt fuel) would only come from a lean misfire.

Your injectors should allow 525 HP.  Doubt that your turbo'ed L6 is going to get there (no offense).  Going too big on the injectors makes controlling idle AFR's difficult, because they squirt too much at the lowest controllable open durations.  You could probably go to a smaller injector and get better tuning control.  The stock 280ZX turbo injectors only flowed 25 lbs/hr (265 cc/min).  Your choice is a bit exuberant.

https://www.rceng.com/technical.aspx

[PKD]

2 minutes ago, Zed Head said:

An AFR of 18 is super lean.  Coughing (unburnt fuel) would only come from a lean misfire.

Your injectors should allow 525 HP.  Doubt that your turbo'ed L6 is going to get there (no offense).  Going too big on the injectors makes controlling idle AFR's difficult, because they squirt too much at the lowest controllable open durations.  You could probably go to a smaller injector and get better tuning control.  The stock 280ZX turbo injectors only flowed 25 lbs/hr (265 cc/min).  Your choice is a bit exuberant.

https://www.rceng.com/technical.aspx

The injectors were from the previous owner who had it built. His idea was to make this a track car. It was a nice attempt but there is a lot of things I would have done different. That said, I have never heard the term "lean misfire". Is the only remedy new injectors? Is there anything I can do with the tune to curtail. I had lowered the idle values and had succeeded in reducing the stink. My main concern is engine temp. What is the right engine temp. I am accustomed to my Fords that run with temp in the 180 to 195 range. What should the L28 be at? I had not played with anything in the higher rpm levels because I didn't detect as much smell from the exhaust, and again the turbo kicks in, which helps any fuel in the exhaust to burn fully, although I don't get any backfire or flames etc. . 

[Zed Head]

180 is normal for the Nissan L6.  Your thermostat and radiator should be the controlling factor there, not your tune.

Some people use exhaust gas temperature as a tuning aid.  But not engine temperature.  Actually, you should be waiting until the engine gets to operating temperature before doing any fine tuning, not watching it go up and down.  

Your injectors are almost 600 cc/min.  That's way high.  Most people shooting for high horsepower with their turbo engines use 440cc/min injectors.  Supra injectors are common.

Makes you wonder if the PO was building a drag strip car.  Have you checked specs on the turbo?  It might be overkill also.  Cam specs?  Compression ratio?  Make sure the engine has a thermostat also.  Race guys like to run without one, but their true purpose is to  heat the engine up, then maintain that temperature.  Could be why your engine temps don't stabilize.  Not uncommon to pop the thermostat cover and find nothing in there.

[PKD]

Zed, it was up to temp when we started. The turbo has one identifier on it. The reference must be a serial number, T-53218. The T is the model series as for the rest, not sure. The previous owner was building a track car to our nearby Roebling Road Raceway. We are not sure about the cam shaft, compression ratio, or thermostat.

[Zed Head]

2 hours ago, PKD said:

We increased the levels and got it back up to 12 to 13 with temp at 176. following pic was screen shot of where we stopped. Also some pic's of under the hood.

Some spec's:  Running a MS3Pro-ECU,  Delphi Fuel Injectors Low Impedance 55lb/hr at 43.5 psi.  Currently running 40psi at fuel regulator,  Turbonetics turbo,  JE flat top pistons with a bore 3.425(86.99mm)

You have some nice parts.  Not really clear what you're adjusting though.  "Increased the levels" could mean almost anything.

Air-fuel ratio is the amount of air over the amount of fuel.  So 15 is leaner than 10.  More air, less fuel for 15 than 10.  

Assuming that the parts are worth saving, you might consider getting some help.  Even the stock turbo engines are prone to detonation.  An L6 built for performance could probably blow itself up much much easier.  You don't know what you have.  It might not even be built for pump gas.

If it was my money and time, I'd figure out as much as I could about what I had.  Measure cylinder pressure, it is a clue about compression ratio.  Look for ID marks on the camshaft.  Figure out what type of turbo you're using.   People blow up the Nissan L6 turbo engines on a regular basis. 

[madkaw]

Like Zed says - you have a nice set up. 

You really need to get as many specifics on your build before putting any power to this engine. Your VE table looks lean at boost , but I'm only NA . 

Injectors are huge and low impedenance I know nothing about tuning . I went with high impedance . 

Whatever you do- go really slow and conservative as not to combust that engine. Timing is critical too.

I would HIRE someone like "Chickenman " to help you reign that in. It would be well worth your money to invest in some help. 

I can help a little since I run MS 3x on my car . 

[PKD]

26 minutes ago, madkaw said:

Like Zed says - you have a nice set up. 

You really need to get as many specifics on your build before putting any power to this engine. Your VE table looks lean at boost , but I'm only NA . 

Injectors are huge and low impedenance I know nothing about tuning . I went with high impedance . 

Whatever you do- go really slow and conservative as not to combust that engine. Timing is critical too.

I would HIRE someone like "Chickenman " to help you reign that in. It would be well worth your money to invest in some help. 

I can help a little since I run MS 3x on my car . 

Thanks Zed and Madkaw, it is a nice set up. It was built by the former owner with track racing in mind. It does really run hard and handles well. The problem has always been the tune. I have only changed a few of the lower idle settings. I haven't touched any of the other ranges(ie boost or cruise ranges). It was more to see how it reacts to the changes. The desire of this post is to get some feedback on how the Megasquirt works with our engines. There are many Miata owners with how to videos on U-tube. That's great and all but those are a completely  different set up then ours. I would like to see and hear some Z info of what our cars do and react to tune variations.  Who is Chickenman?

[madkaw]

I'm not sure there is much difference in tuning procedures between any engines. The principles are the same. Specifically the older engine design of the L motor will not tolerate a bad tune as well as more developed combustion chambers and dual overhead cam set ups. Most issues with these motors are with detonation and HG failures in the latter cylinders. Timing should be kept conservative unless dyno tuning with knock sensor capability .

You should pay the extra fee to have VEAL available to help self tune. The analyzer does a pretty good job of helping dial in VE tables , but nothing for timing. Veal will even help warm up tables.

As mentioned earlier there is a wealth of info on Hybridz . There is a dedicated Mega Squirt forum to search from.

Chickenman is on this site and many others (Richard Boyk), so maybe you could PM him to see if he is available to help you. He is very familiar with tuning EFI and has a wide range of knowledge with aftermarket ECU's. He helped me get a head start on tuning with MS3 and tutored me on tuning in general. He could look at your tune and pretty much tell you what the car was set up for. He could help you get a more street friendly tune.

I'm cutting my teeth with NA , so it's less likely to implode with a mistake. You don't have that option, so I would advise getting help before making adjustments and hoping for the best.

In general, I am happy with my MS. My car runs very well and performs as well as it did with my triple Mikunis. It's a steep learning curve , but well worth the study 

      

[madkaw]

Have any luck?

[Chickenman]

PM sent.  Got a couple of local tunes sorted and can probably help this fellow out.