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So I found a true Nissan TPS at the JY and it is so much more accurate !  Don’t even know what model it came off of, but it works. Didn’t need to preload it or anything 

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^ basically yes,  ( There are other constants involved that have to be taken into account. But those are constants ).  Tuner Studio adds a large " Fudge " factor on the Rich side so it will be safe for Newbies. Consider Req_Fuel and the Calculated VE tables as a very rough starting point.

 

I find it's really annoying that they do that. It's a common complaint with Tuner studio. 

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But in reality, the TS Req_Fuel calculation is not accurate. Neither are the TS VE Tables. They are rough approximations... very rough approximations. That is the problem. The Req-Fuel calculations are a good 25% higher than other PW calculators estimate. This is covered in the advanced forums many times over. 

 

MS and TS even admit to this if you search hard enough. 

 

I find it's really annoying that they do that. It's a common complaint with Tuner studio. 

 

I've never heard this before.

 

Which advanced forums? Can you provide a link?

 

I've searched and read the MSextra site religiously for the past 8 years and have never seen any mention of these issues.

 

The Req_Fuel algorithm that TS uses is here: http://www.megamanual.com/v22manual/mfuel.htm

I don't see any "fudge factor". What do the other PW calculators use?

 

One thing I do know is that if you want to get a good VE table, it is critical that you have a good understanding of your injectors. You must have the correct deadtimes and voltage correction as well as the correct flow rate. (If you have exceptionally large injectors, you will need to calculate the small pw correction curve as well.) This requires testing your actual injectors with your injector drivers. That's why TS and MS provide the test modes. https://www.youtube.com/watch?v=lJgi8l-2XG4

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Just because you've never heard it before doesn't mean it isn't true. The information is out there.  MS Forums if you dig deep enough,  and Forums like HP Academy, and EFI University.

 

You don't see any " Fudge Factor " because it's built into the software code algorithims. MS admits this themselves if you look deep enough.  I posted the PW calculator from HalTec in another thread. PW calculators have been around for decades and there are lots of accurate ones to be found online. 

 

The fact is that Req_Fuel is just a Table Multiplier and not a very accurate one is well documented. Search harder. The calculations it comes up with are not accurate. It is a very rough calculation. 

 

Sorry but I've had too many days where I've been up past 3:00 AM in the morning dealing with ECU and Desktop computer repairs. . I don't have time to search for you, nor go back over 200+ pages of browser history. Not being a smart ass, I'm just tired. And I just had my beloved Cat die this weekend. 

 

Garbage in Garbage out is what I've always stated. But when you input the correct values and you get garbage out then that is a problem. 

 

Here is a screenshots of a proper PW Calculator which calculates minimum and maximum PW's and is VERY accurate. Following that is MS Req_Fuel calculator ( which is just another name for a Master PW calculator ) . Where are the input fields for Air Temps and MAP values. 

 

Below is the Master PW Calculation for a Tune I just made for a member and which is working fine. This is an accurate calculation.

 

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TS Req Fuel calculator picture below comes up with 12ms which is way to high of a requirement. That throws the VE Table calculations off. And this is done on purpose. To provide a " Fudge Factor " and make it safe. That is one of the design factors of TS. Well known and documented.

 

The following entries are for the same engine as above. Haltech  Master PW = 8.42ms . TS Req-Fuel ( Master PW ) = 12.0ms. Over 25% too high . That is what is called a ROUGH calculation. 

 

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Going to bed. To tired to discuss any further... 

Edited by Chickenman
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BTW, MS and TS are fine for what they are. A learning tool. And the price point is good. But it's a DIY experimental science project. For what it is... " an inexpensive assemble it yourself, piece of kit to learn EFI.... it's pretty good. 

 

But its; simply not in the class of Motec, Adaptronics, Autronics Haltech, AEM Infinity and other high end systems. Nor should it be compared to them. That's not it's design criteria...  

Edited by Chickenman
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Just because you've never heard it before doesn't mean it isn't true.

Agreed. This is why I asked for sources.

 

 

 

The information is out there.  MS Forums if you dig deep enough,  and Forums like HP Academy, and EFI University.
Search harder

I've searched pretty hard and have found no confirmation of a "fudge factor" or any other claims of inaccuracy in the PW calculation, intentional or otherwise, in the calculations.

 

 

 

You don't see any " Fudge Factor " because it's built into the software code algorithims. MS admits this themselves if you look deep enough.  I posted the PW calculator from HalTec in another thread. PW calculators have been around for decades and there are lots of accurate ones to be found online
In my experience, Megasquirt algorithms perform "as advertised." That is, they produce results in accordance with their documentation. There are no hidden "fudge factors" to protect users from their naivety or inexperience. An overly rich condition can damage an engine just as an overly lean.
 
I think I see the disconnect. The PW generator example you give is calculating PWs for running engine conditions. Megasquirt uses the ideal gas law to do that. (The spreadsheet you show may use the ideal gas law as well, but the formulas are hidden and password protected, so I can't easily tell.)
 
The TunerStudio Req_Fuel generator calculates the PW (time) required to deliver a quantity of fuel to produce a stoichiometric mixture in one cylinder' volume of air at a standard atmospheric condition (1000kPa @ ~70degF IIRC).   This number is then adjusted by the megasquirt algorithm based on the amount of air the tune tells it is going into the engine (expressed as VE, or the percentage of a perfectly filled cylinder under standard conditions - looked up from the VE table) and the ideal gas law which adjusts for temperature and pressure. Again, no fudge factors, just science. 
 

 

BTW, MS and TS are fine for what they are. A learning tool. And the price point is good. But it's a DIY experimental science project.

I might agree with you somewhat on a MS1, but this thread is about MS3, which while relatively inexpensive, is quite capable.

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Waiting for my battery to charge up so I can try and fire this up. Well actually a couple of other things , but very close!!

 

Fuel vent question. Thinking about using original flow guide valve on inner fender . Why can't I attach C side to the piping on my CAI? There's actually a hose connector in front of the butterfly on the 240sx TB .

My understanding of the valve function is that it only opens to tank when there is pressure coming from tank side, it doesn't allow vacuum directly to tank.

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post-1083-0-06872100-1495218492_thumb.jpg

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So Richard and I had a session on team viewer which was quite cool. Using this media he could walk me thru the tuner studio settings and make changes as needed. The required fuel did turn out to be much less than MS software came up with, I don't know enough to argue one way or another , but I know the tune 'chickenman' help me put together ran pretty well . Good enough that I drove it the next day to C&C with no issues-first drive EFI!.

Getting this baseline will really help me get a performance tune done quicker. I actually went out yesterday and drove and tuned, and drove and tuned, and I didn't get any gas on me at all-LOL.

Power level is actually pretty damn strong, but my wideband was acting up a little. I did bump up the timing a bit Richard ;)

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So Richard and I had a session on team viewer which was quite cool. Using this media he could walk me thru the tuner studio settings and make changes as needed. The required fuel did turn out to be much less than MS software came up with, I don't know enough to argue one way or another , but I know the tune 'chickenman' help me put together ran pretty well . Good enough that I drove it the next day to C&C with no issues-first drive EFI!.

Getting this baseline will really help me get a performance tune done quicker. I actually went out yesterday and drove and tuned, and drove and tuned, and I didn't get any gas on me at all-LOL.

Power level is actually pretty damn strong, but my wideband was acting up a little. I did bump up the timing a bit Richard  ;)

Timing bump by you is OK.  I always go a bit conservative. Last hand in the Cookie Jar... LOL  :P

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  • 2 weeks later...

So I've had more time to play-but not enough ever-really!  The car ran, runs, decent and this last week was more about me experimenting to see how bad I could f@ck up Richards tune. Thankfully files can be saved and is saving my ass anyway. I believe my biggest issue was getting the VE tables tuned in based on Richard's tune. I couldn't get rich enough AFR's at WOT once I got into the power band. Nothing wrong except trying to figure out how much fuel the VE tables needed to have.

I tried the auto-tune VE analyzer, which actually worked well for everything midrange on down, but wouldn't fix my WOT lean issue. I was beginning to doubt my choice of injectors being that I used a stock Bosch replacement for the 1.8 turbo-which has a very wide spray pattern which might have been impeding flow by hitting the walls too much. In the end, it was a matter of really bumping the numbers in the VE up quite a bit-then I found the power button !!!!!!!!

Now I can dial in WOT AFR to precision -very nice. Something that took a lot more work and trial an error with Mikunis. I would say that the motor runs just as strong as with my 40's.

Look mom, no gas on my hands  .      

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Yeah, as we've discussed privately,  the TS VE tables are not all that accurate.  Gets even worse with modified engines. They tend to be too rich on the low end and too Lean on the Top end.  

 

The calculated VE tables all seem to Peak at around 4,000 then the values taper off. This simulates the top end drop off in VE that most stock engines experience. Unfortunately this does not take into consideration any modifications for improved performance which can extend the peak VE range. It also does not take into consideration more modern technologies such as VVT.. Basic problem is that the Tuner Studio VE Calculator is not all that refined. 

 

I've just done a couple of Tunes where I've taken the max VE values ( usually around 4K ) and extended those values to the end of the RPM range. This seems to be much more realistic strategy for modern engines. Unfortunately Auto Tune cannot do WOT tuning. It's too slow. 

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One of the really handy items that some stand alone ECU's  use is a Trim Pot. A simple 10K Ohm Linear pot that can change Fueling or Timing temporarily with a quick twist of the knob. A percentage shows up in a box to tell you how much you are adding or subtracting in Real Time. Makes dialing in WOT AFR's much faster. Also Start-up enrichment's, WUE and even idle values. 

 

Would be nice is MS incorporated that feature. 

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One of the really handy items that some stand alone ECU's  use is a Trim Pot. A simple 10K Ohm Linear pot that can change Fueling or Timing temporarily with a quick twist of the knob. A percentage shows up in a box to tell you how much you are adding or subtracting in Real Time. Makes dialing in WOT AFR's much faster. Also Start-up enrichment's, WUE and even idle values. 

 

Would be nice is MS incorporated that feature. 

You can use the table blending to change the fueling or timing in real time, although it is not intended to be used as a tuning tool.

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  • 2 weeks later...

So far so good on my fuel tank vent set up. I haven't experienced any fuel smells so far . I knew it would be less getting away from the Mikuni open Float bowls, but wasn't sure about pressure build up in the gas tank. Eventually I would like to put a charcoal canister in line for storage for when the car sits for longer periods and the venting fuel has no where to go because the engine isn't running to suck the fumes out.

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  • 1 month later...

So after getting some highway miles in I think I will have to deal with heat soak issue now. I had a hard start the other day after a 50 mile trip. I know I have to do certain things for sure.

Heat shield- I'm not running one. I have ceramic coated headers which do pretty well , but need to make shield

IAT Sensor - GM style sitting on top of intake . I think I will try a plastic adapter first before I try and change position . For some reason when I opened up the hole where the cold start injector was I opened it up all the way to 1/2" NPT.

GM sensor is 3/8" NPT , so presently I run a brass adapter. I think I will run a plastic adapter so that the sensor is not touching the intake. I will see how that turns out.

Highway AFRs were spot on 15 and the engine hummed along beautifully . MPG seems pretty good and hope to have solid numbers after a long trip.

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