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(Post Link) post #1 of 10 Old 19-01-15 Thread Starter
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Strange duration maps on original JTD 8V 85kW ECU EDC15C7

Hi to all!

I have tuned my car's ECU myself and everything looks OK; nice power gain, no errors...but, I'm confused with original values in duration map.
The problem is that for values greater than 60mm3 of fuel, values are no more linear for same rail pressure. There is even "inversion", where for 70mm3 of fuel there is greater injection time for fuel pressure of 1400 bar than of 1350 bar. And with all logic, it should be vice versa.
Original duration map looks like this:
Original duration map
In stock ECU software, there is minimum of 300bar pressure and max of 1350bar. Also, there is max 60mm3 of fuel injected...so that strange values are not used. But, when remapping and requesting more fuel, also requesting more rail pressure...this stock values seems not to be good. If I put this at graph, it can be seen that there is break about at 65mm3 where curves for rail pressure rapidly raises:
Original duration graph

It can be seen that line for 1350bar and 1600bar are more or less linear and OK, but others are raising rapidly after 60, 65mm3.

So, when doing linear extrapolation of last two columns (like everybody suggests when increasing axes for maps), map that allows 80mm3 of fuel looks like this:
Duration map with extrapolation

And in graph, it looks like this:
Duration graph with extrapolation

It seems preety messy and wrong to me.

If I do some math and visualisation correction of graph, I end with this kind of map:
Modified duration map

and graph:
Modified duration graph

And that looks OK to me. So, my question is...why is stock map looks that strange?
If I look to duration maps of other cars...there are allways nice linear curves. But this and other JTD 8V engine...a total mess.

So what would you suggest to go with; linear extrapolated map of last two columns with that strange values or map with modified values to match linearization and have a nice linear curves?
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Think about what affects the flow in the injector. And see my post with figures from lab measurement - https://www.alfaowner.com/Forum/tunin...ml#post9341569 (slightly modded injectors thought, but the high end throughput is still comparable).

Last edited by yan.ko; 30-01-15 at 17:21.
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(Post Link) post #3 of 10 Old 19-01-15 Thread Starter
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Thanks!
Nice info there. So, it seems that after 60mm3 stock injectors are no more linear, maybe fuel pressure drops a little...so that could be reason for raising duration? However, still not convinced that for same amount of fuel - talking about 70mm3 column - @1400bar it needs more duration than @1350 bar. And than @1600 again duration drops; also, why are values @1350 and @1600bar almoust linear and @1400 not?
It looks like there is some restriction @1400 bar which dissapears with few bar less or more...strange to me.
However, in my current remap, I used linear extrapolation of values 65 to 70, and my max IQ is 75mm3 @1450bar which is about 955uS of duration. I'm wondering if this duration and pressure is around 75mm3 like I requested, or is more than 75.
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Alfa 159 2.4jtdm

I noticed same thing few years ago, and when using interpolation for higher iq's (100+mm) car turns off due to rail pressure deviation, but if I make new value for 70mm duration by interpolating values before, and then interpolating for higher IQ its seems ok
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(Post Link) post #5 of 10 Old 27-01-15 Thread Starter
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So, if I do some corrections and approximations, can this values be OK in duration map for 115HP JTD 1.9 ?
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No
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(Post Link) post #7 of 10 Old 28-01-15 Thread Starter
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Quote:
Originally Posted by yan.ko View Post
No
So you suggesting to keep stock values for 70mm3?
If yes, how can be possible that for 70mm3 and 1400bar there is greater duration than for 1350bar and same quantity? Does not make a common sense...moreover because for 1600bar there is value that matches linear curve...so for 1400bar and 70mm3 there should be value around 850 - 855 to match lines between 1350bar and 1600bar.
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if you had looked on my table in <code> tags in my linked post, you would have known that for iq of 90mm3 119 injector needs to be energized for approximately:

1220us @ 1400bar
1150us @ 1500bar
1090us @ 1600bar
1050us @ 1700bar
1010us @ 1800bar

More to see there.

Last edited by yan.ko; 30-01-15 at 17:21.
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(Post Link) post #9 of 10 Old 12-02-15 Thread Starter
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Quote:
Originally Posted by yan.ko View Post
if you had looked on my table in <code> tags in my linked post, you would have known that for iq of 90mm3 119 injector needs to be energized for approximately:

1220us @ 1400bar
1150us @ 1500bar
1090us @ 1600bar
1050us @ 1700bar
1010us @ 1800bar

More to see there.
OK, that can be true for 90mm3...but if you look at your values you can see that duration is lowering with pressure for same amount of fuel. And that is correct. But in stock duration map for 70mm3 there is wrong value for 1400 bar:

70 mm3:

1127 uS @ 1000 bar
978 uS @ 1200 bar
948 uS @ 1300 bar
871 uS @ 1350 bar
897 uS @ 1400 bar !!?
795 uS @ 1600 bar

So this 897 uS @ 1400 bar can not be true if 871 uS is enough for same amount of fuel @ 1350 bar.
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Hello yan.ko and the other experts, do all JTD engines use mm3 for injection quantity?
My car is a Alfa 156 2.4JTD 10V 150HP CF3 engine with ecu 0281010741

I ask because this would explain some strange values in my smoke map because I didn't convert mm3 in mg/Stroke (factor 0,84)
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