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 Post subject: increase target boost past 24.75psi
PostPosted: Tue Jul 20, 2010 1:41 am 
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Any chance a dev will be able to take a look and see how easy/hard it is to increase the max target boost value from 24.75psi (maybe to 30psi)?

This would be greatly beneficial to those who have upgraded their MAP sensor and want to still use the oem EBCS system to target higher than 24.75psi.

I'm sure Bill responded to a question like this a while back saying it was possible - however since his time is now consumed at his new place of employment, I was hoping someone else might be able to do this.

Any thoughts?

cheers,
Leslie

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Current Car: 2002 ADM WRX STi
Current Engine: EJ207
Current Mods: X-Force 3" TBE Exhaust, GCG "bolt-on" GT3076R, APS 3" Hard Turbo Inlet, Short Ram Pod, RomRaider/ECUFlash Tune
Current Power: 248kw@wheels (332whp)


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Thu Jul 22, 2010 8:39 pm 
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Bump.

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Current Car: 2002 ADM WRX STi
Current Engine: EJ207
Current Mods: X-Force 3" TBE Exhaust, GCG "bolt-on" GT3076R, APS 3" Hard Turbo Inlet, Short Ram Pod, RomRaider/ECUFlash Tune
Current Power: 248kw@wheels (332whp)


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Thu Jul 22, 2010 11:07 pm 
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This is the 'scaling' that your target boost table uses - the conversions between what RomRaider displays (the "to" expression) and what the ECU actually uses (the "from" expression).

<scaling name="BoostTarget(psirelativesealevel)" units="Boost Target (psi relative sea level)" toexpr="(x*.15469416)-14.6959452" frexpr="(x+14.6959452)/.15469416" format="%.2f" min="-14.70" max="24.75" inc=".08" storagetype="uint8" endian="big" />

Target boost is stored in the ECU as an 8-bit unsigned value, so the valid range is 0-255.

Plugging 24.75 into the "from" expression:
(24.75 + 14.69) / .15469 = 254.9 = basically 255.

So, this is essentially the same problem as the 300 g/s MAF limit, the ECU just can't comprehend larger numbers.

You could probably work around it in the same way as the MAF limit though, by tweaking the MAP sensor scaling and cutting the boost targets and limits in half.

For bonus points, you could double the ".15469" value in the expressions in the table definition, and RomRaider would then display the proper values (you could do the same kind of thing to get RR to display true values for half-MAFed tunes, too).

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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Fri Jul 23, 2010 1:28 am 
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NSFW wrote:
Target boost is stored in the ECU as an 8-bit unsigned value, so the valid range is 0-255.

Plugging 24.75 into the "from" expression:
(24.75 + 14.69) / .15469 = 254.9 = basically 255.

So, this is essentially the same problem as the 300 g/s MAF limit, the ECU just can't comprehend larger numbers.

You could probably work around it in the same way as the MAF limit though, by tweaking the MAP sensor scaling and cutting the boost targets and limits in half.

Cheers for the reply :)

I just checked my ROM, and there is no MAP scaling listed? There is only MAP sensor multiplier and MAP sensor offset (4 of each - A,B,C,D).

I don't want to make a mistake (my GT30 is capable of killing my engine pretty quick from an overboost), so I want to ensure what I am about to do is the correct way to do it.

From what I can see, I would have to:
  1. Halve MAP multiplier values A,B,C,D. Change from 0.6855 to 0.3427. This should then halve the value that the ECU is interpreting from the MAP sensor V
  2. Halve Target Boost cell values

Is that all I would have to adjust?

Also, if I left the WGDC tables alone, would I be correct to assume that regardless of the above changes, and regardless of what RR Logger displays for manifold relative pressure, the actual boost being run would not change since WGDC has not changed?

NSFW wrote:
For bonus points, you could double the ".15469" value in the expressions in the table definition, and RomRaider would then display the proper values

So if I do what I listed above (halve map sensor multiplier) and then double the ".15469" value in the expressions in the table definition in the RR logger def file, it would show actual current manifold relative pressure (ie. the same as my boost gauge)? If so, that would be awesome :)

NSFW wrote:
(you could do the same kind of thing to get RR to display true values for half-MAFed tunes, too).

So if I multiplied all load values by 0.75 for my 300g/s mod, I'd divide the value in the expressions in the table definition and in the logger it'll show me the correct load? I will be trying this tonight :)

Leslie

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Current Car: 2002 ADM WRX STi
Current Engine: EJ207
Current Mods: X-Force 3" TBE Exhaust, GCG "bolt-on" GT3076R, APS 3" Hard Turbo Inlet, Short Ram Pod, RomRaider/ECUFlash Tune
Current Power: 248kw@wheels (332whp)


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Fri Jul 23, 2010 2:05 am 
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It wouldn't hurt to get some input from other people before you go tweaking your MAP scaling. I think this will work, but someone else might see something that I'm overlooking.

Just to be clear, there are three different changes we're talking about...
1) Making the logger show the correct values for MAF and Load.
2) Tricking the ECU into working with boost > 24.75psi.
3) Making the tables show up with the correct values.

For the logger part, just tweaking the equations in logger.xml should cause the logger to show the true values. You can do that without opening up the ROM, in fact that's probably the best way to get started with all of this, since the worst you could do it produce a log with incorrect values in it (which you have been doing for quite a while anyway, right? ;) ).

For the workaround to the boost limit... I'm afraid that if I give you detailed instructions I'll get something wrong. But I think you have a good handle on the math. I'm not sure how the MAP sensor scaling works on the 16-bit ECU. With 32-bit ECUs it's just an offset and multiplier, and come to think of it I'm not sure what's the appropriate change to make to the offset if you halve the multiplier. See below for an idea to test this safely, though.

For making the boost tables show the right values, first tweak the formula in your ROM definition so that RR shows 2x the current values. Then tweak the formula that causes it to write the correct values into the ROM when you change things. Actually I would recommend using EcuFlash for these - the definition file is easier to edit, and EcuFlash can load a ROM much more quickly than RomRaider can. Keep the RomRaider def as-is, and use it to verify that the expected values (half what you enter in EcuFlash) show up in the ROM when you save it in EcuFlash and open it in RR.

To test the MAP sensor changes, unplug your boost control solenoid, or route the compressor nipple directly to the wastegate actuator. Set your boost targets at wastegate boost, and verify that the logger (with modified logger.xml) shows the 0psi when the engine is off, shows actual wastegate boost psi when you do a WOT pull, and shows the same vacuum as usual when you idle. If it does all of those correctly, then you did it right. Post up your changes, and we'll brainstorm on the fix.

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Please don't send me tuning questions via PM - use the forums instead. Thanks!


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Tue Sep 28, 2010 6:36 pm 
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Joined: Tue Oct 30, 2007 9:10 pm
Posts: 33
Location: California
I did this on my 02 WRX......

Im not at home....but all i did was change the offset (IIRC) to make the MAP sensor read 5.25 psi low

That way when it was at 24.75 psi...it would actually be 30....it made the math easy. And for the rest of the target boost values i just basically knew i was 5 psi higher all the time.

The logger didnt read correctly.....but i could still use the target boost, turbo dynamics and fuel cut.


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Thu Sep 30, 2010 7:47 am 
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Joined: Fri Dec 08, 2006 2:15 am
Posts: 12
The problem is the MAP-sensor. It doesn't read more. It operates from 0V to 5V.

Changing the MAP-sensor to a bigger one, and rescaling the MAP-parameters should work.


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Tue May 10, 2016 11:19 am 
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Joined: Sat Jan 12, 2013 3:58 pm
Posts: 126
^ I need to run 24-25 psig on my car, i got a map sensor on the way. Is this all i need to do? Or do i have to trick the ecu that it is reading less boost?


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 Post subject: Re: increase target boost past 24.75psi
PostPosted: Tue May 10, 2016 2:41 pm 
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Joined: Thu Aug 03, 2006 10:40 am
Posts: 1911
JMlegacy wrote:
^ I need to run 24-25 psig on my car, i got a map sensor on the way. Is this all i need to do? Or do i have to trick the ecu that it is reading less boost?


what rom are you running on?


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