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Losing boost at high rpm when ebc duty the same

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Losing boost at high rpm when ebc duty the same

 
Old 09-28-2018, 04:08 AM
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Default Losing boost at high rpm when ebc duty is the same

Hi guys,

I am having an issue tuning my boost table.
It seems to take no affect if i ran wastegate or boost controller pressure, at ~3700 rpm my boost is going down gradually.

I can reach ~8 psi (which is what i want) but when i get to that specific rpm it starts to climb down, so i guess there a no boost leaks issues as its able to get to this boost level.
The only thing i can think of is the wastegate rod as it was modified due to clocking the turbo and might have too little resistance, i tried to move it with my hands and it wasn't easy and it seems to have full motion (open and close the door).

I have attached 3 logs with different boost controller duty values and the tune file.

appreciate your help

Thanks
Attached Files
File Type: msl
2018-09-26_22.38.31.msl (321.6 KB, 8 views)
File Type: msl
2018-09-26_23.20.14.msl (217.9 KB, 8 views)
File Type: msl
2018-09-26_23.15.08.msl (370.8 KB, 9 views)
File Type: msq
Tune.msq (262.8 KB, 9 views)

Last edited by rom_nb; 09-28-2018 at 04:23 AM.
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Old 09-28-2018, 05:09 AM
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Where is your boost source for the actuator located? If it is pre-intercooler and you have a pressure drop over the intercooler your manifold pressure will drop with RPM as the restricion increases and the pressure drop increases.

You could just ramp up the boost duty to hold the boost flat though.
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Old 09-28-2018, 05:45 AM
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Don't think about it too much if increasing your duty cycle gets you to your target boost at redline.
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Originally Posted by ninerwfo View Post
The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
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Old 09-28-2018, 06:07 AM
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Originally Posted by Reverant View Post
Don't think about it too much if increasing your duty cycle gets you to your target boost at redline.
I will give it a try but i am a little skeptical as it will require a very fine tune, in 100 duty i will reach boost protection, and in 85 the boost drops, i hope to find the sweet spot where i will be able to keep my boost level and not hitting the over-boost protection.
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Old 09-28-2018, 06:12 AM
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Only increase duty where the boost drops, not before. This is why you have a table and not a single number to enter for all RPMs.
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Originally Posted by ninerwfo View Post
The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
MS Labs: Plug and Play Megasquirt ECUs for ANY 90-05 Miata (NA, NB1, NB2 w/VVT, MSM), including basemaps to get you started ASAP. PM me or email or details.
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Old 09-28-2018, 06:33 AM
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Also, consider running a lower Hz output, it should bring the numbers you need for extra boost down.

Do not do this and then try you 85% map it will just hit boost cut.

Dann
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Old 09-28-2018, 10:01 AM
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I tried basically everything you guys said.
I am tuning this car. Boost even falls off at wastegate pressure to like 4 psi.
It's like the wastegate can't modulate boost pressure.
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Old 09-28-2018, 01:13 PM
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Then you have a very soft spring and/or need to pretention the wastegate.
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Originally Posted by ninerwfo View Post
The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
MS Labs: Plug and Play Megasquirt ECUs for ANY 90-05 Miata (NA, NB1, NB2 w/VVT, MSM), including basemaps to get you started ASAP. PM me or email or details.
For support on MS Labs ECUs: Please email, be sure to include the unit's serial number and include a datalog and your current map.
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Old 09-28-2018, 01:16 PM
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what turbo is it even running
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Old 09-28-2018, 01:36 PM
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Originally Posted by Reverant View Post
Then you have a very soft spring and/or need to pretention the wastegate.
​I tried to move it with my hands and it wasn't easy​​​​​​, any way to tell what is the correct resistance?
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Old 09-28-2018, 01:37 PM
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Originally Posted by 18psi View Post
what turbo is it even running
​sr20 t25​​​​​​
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Old 09-28-2018, 01:38 PM
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you have a leak (could be either boost, exhaust, or both), or a bad wastegate, or a clogged exhaust
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Old 09-28-2018, 02:30 PM
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Originally Posted by 18psi View Post
you have a leak (could be either boost, exhaust, or both), or a bad wastegate, or a clogged exhaust
Even though its holding boost until this rpm? And reaching a much higher boost when the ebc is completly shut?
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Old 09-28-2018, 02:46 PM
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yes. as long as the leak is smaller than the amount of air the turbo is flowing, it will still build boost.
it's also an excellent way to kill a turbo by continuing to run it undiagnosed
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Old 09-28-2018, 07:50 PM
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Get a stronger wastegate. My guess is that the ebc holds it shut, but when it opens up around 8psi it flies open and the exhaust pressure holds it too far to keep boost up.
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