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Ve numbers high at idle


Gtr_lee

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Hi, Could someone take a look at my tune to see if they can spot something wrong with the set up please.

It's a mk2.5 mx5 turbo that runs 4bar return less system with walbro pump

The Ve at idle is really high and in the 80's which does not seem right. I am using bosch 0280158235 injectors that come with the turbo kit. I found what I thought was good data on them from Finjector - pic attached 

Please ignore the majority of the Ve table, It's not been touched and I have only tried to get it to idle and get afr's ok by revving up to about 3,000rpm. I stopped trying to do anything else until I can figure out why the numbers are so high.

 

Thanks 

 

Injector data for bosch 0280158235.jpeg

MX5 modelled Fuel 25.3.24.pclx

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High VE is certainly a sign that the injector data is incorrect or could be your fuel pressure is low. My interpretation of that injector data is that you need to create a 3d table with the deadtime * differential fuel pressure because of the returnless fuel system. I'm not sure if you should use the 3 bar or 4 bar fuel pressure numbers as a starting point since their correction table is based on a 3 bar scale but you could do trial and error to find what is close to the correct numbers. Check out KORacing's explanation on the process:

 

And your tune seems like a fine starting point. I would 0 the warmup enrichment all together unless you've found you need it by now.

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Thanks for sharing that post, will give that a try this week. 
 

As for the dead time table with differential fuel pressure, do I need a fuel pressure sensor for that to work? As I do not have one installed at the moment. 

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You don’t need a fuel pressure sensor, but having one is more accurate. With your current settings the ECU calculates differential pressure = (base pressure - MGP). For instance, when you saved your tune, it was showing 464 kPa differential fuel pressure since your base is 400kPa, and idle MGP was -64kPa. 

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in injector dead time table, press X to access axis setup, an put differential fuel pressure in the Y axis.

make for example 3 lines with 200 300 and 400 kpa and input the data vs voltage

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Thanks for that dx4picco

I am going to do the test that KOracing shared in the post above later today.

I take it that once I have filled out the 3d deadtime table, I can highlight the whole table and move all deadtimes up and down until I can get more realistic VE numbers? 

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Tried doing the test yesterday and change dead times to try and get afr to track after changing target table. But something doesn’t seem right.

I would change it from Lambda 1 to 0.9 and it would overshoot to 0.82-0.85. So would adjust dead times up and repeat the process. But no matter what I changed the dead times to I couldn’t get it to track.
 

It seems even if I don’t change the dead times at all and get it bang on Lambda 1, change to 0.9 and then back to 1, it will overshoot past Lambda 1 to 1.1-1.2. It’s like it’s constantly changing. 
 

I didn’t have any fuel corrections on at the time so that shouldn’t have affected the test. 
 

Any ideas? 

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Have you verified fuel pressure with a mechanical gauge? And that it maintains 400kPa at idle/revving/driving, etc.?

deadtime-table.png

Here's the injector data you provided translated into a 3D table. I'd actually probably extrapolate those zeros just to make sure you don't get stuck in a weird condition.

INJ Deadtimes.lte

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No I haven’t got a fuel pressure gauge or sensor at the moment. But is on the shopping list. Changing to a return style system with an adjustable regulator might be the way to go in the future. 

I made a 3d table just like you showed above but because I don’t have a pressure sensor it just sat in the 250kpa/14v row the whole time. Ended up going back to a 2d table. 
 

I actually ended up with the value of 1.060 for 400kpa at 14v to get it closer to where it wants to be. 
 

I am in the UK and have not got an Mot or road tax as the car has been off the road for over a year. Which means I can’t drive on the road to test and log at the moment. Should hopefully be on a dyno soon. 

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28 minutes ago, Gtr_lee said:

I made a 3d table just like you showed above but because I don’t have a pressure sensor it just sat in the 250kpa/14v row the whole time. Ended up going back to a 2d table. 
 

I actually ended up with the value of 1.060 for 400kpa at 14v to get it closer to where it wants to be. 
 

I am in the UK and have not got an Mot or road tax as the car has been off the road for over a year. Which means I can’t drive on the road to test and log at the moment. Should hopefully be on a dyno soon. 

Do you have a PC log and tune that you can share?

Differential fuel pressure in modelled mode/returnless is Base Fuel Pressure - MGP. At rest you should have 0 MGP so your deadtime table should pull from the 400kPa row. At idle you'll have maybe -50 MGP so you'd be in the 450kPa row. Under 150kPa of boost you'd have 400 - 150 = 250 kPa differential pressure.

I'm not sure what you mean by "where it wants to be" - if you've entered the injector dead times correctly and the engine runs well, I wouldn't get hung up on the value of some arbitrary numbers.

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The tune is in the first post I made. 
 

I must of made a mistake somewhere then if that is the case. I will redo the deadtime table and check again. 
 

The only reason I looked in to deadtimes in the first place was because the VE numbers are really high at idle and idle afr’s were constantly moving after setting it at lambda 1. 
 

I will see if i can dig out a decent log when I get back home. 

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I was just hoping for a tune with your deadtime changes, maybe something would stick out as far as why it was sitting at an odd value.

If you go Injector Setup > Deadtime Table > 3D Table, you can open the injector dead time table and right click > Import from File and import the file attached to my last post.

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I will load up that dead time table tomorrow and see what happens. Thanks 

In the mean time I have been doing some reading, part of my issue looks like it could be my walbro 255 pump over powering the stock regulator in the tank. A guy on the miata forum was seeing pressures of 80psi at idle and it would fluctuate too. Would explain why my afr’s never stay stable. 
 

Will look in to buying a return style set up with fuel pressure/temp sensor 

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  • 3 months later...

Still not managed to fix this issue yet. I ended up putting my stock fuel pump back in the car, and switching it to traditional mode just to get the car running somewhat ok to pass the MOT and drop it off to my fabricator.

I tried using a deadtime table with differential fuel pressure but still had Ve numbers in the high 70's/low 80's around idle.

But I would still like to get it up and running in modelled mode though

I found some more info on the injectors from the Motec forum. Could someone smart help translate what the numbers mean please. They reference micro litres on the dead time table and I have no clue as to what that means.

If not, I think I will just have to buy a set of ID1050's and be done with these random Ev14's.

 

0 280 158 235 Customer sheet.xlsx

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