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Boost controller advice needed

913 Views 11 Replies 0 Participants Last post by  LeeLegend
I read several posts about the boost controller for the EVO.
I have some questions
-How does it work exactly ? Alter the boost level on any desired level?
How does it do that ,does it keep the wastegate closed longer and more then standard?Or does it do it through the ECU unit?
Does the ECU know that you run more boost so will it give more fuel so the car does not run lean?
What brand is a good one for the EVO (EVO6 RS2)
Can you expect more HP from this ,or is it just a nice gizmo ?
Any info is appreciated.
Bye chris
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The boost controller will use a solenoid to bleed off vacuum before it gets to the wastegate so it stays closed allowing boost to build up. and use its internal gadgetry to work out boost levels. the best is the HKS it uses a stepper motor instead of solenoid and is the most accurate.
the ECU will not compensate for the extra boost so u may well start 2 run lean. keep boost levels at around 1.1 bar sustained max while stilll using standard will get a bhp increase and using a boost controller will help u 2 avoid fuel cuts rather than just removing the grommet. with an exhaust and filter upgrade you should get a good power gain.

Hope this helps

i am having the blitz sbc-id fitted on tuesday next week, so will let you know how it goes....

Does the ECU know that you run more boost so will it give more fuel so the car does not run lean? - Yes of course. But fuel cut will happen at a certain Karman value (around 1700Hz), that is around 1,2 - 1,3 bars.
What brand is a good one for the EVO (EVO6 RS2)? HKS/Blitz/........? - I use an Apex'i AVC-R. It is supposed to be the best one. Read about it on
Can you expect more HP from this ,or is it just a nice gizmo ? - You will get approx 340 bhp with 1,4 bars boost.
Are you sure about the ECU adding more fuel because you've increased the boost using a controller?
AFAIK most boost controllers work by bleeding off pressure to the solenoid so that the ECU 'sees' a lower than normal level of boost and this is how they avoid the fuel cut problem. In this case, the ECU won't see the extra boost and therefore won't increase the fuelling. The best way to increase the boost and fuelling (without going for a programmable ECU) is to get a seperate fuel computer and boost controller and then you can be certain that everything is OK.

But anyone can correct me if I'm wrong


If the ECU didnt supply the extra fuel/air for the extra boost generated by
a boost controller then id be selling a lot of pistons/rods !!!!!

The problem you need to worry about is running more boost than the injectors
can supply fuel for or causing detonation.

Seems like the safe limit is 1.25 for stock ECU's.

OK then, I'll correct myself coz I'm talking ######## for a change :)
The boost reading that is taken by the ECU for fuelling etc is independant of the boost control solenoid feed and so it will compensate for the extra boost until it hits the overboost / fuel cut limit.


you are mixing it up with the Fuel cut defender. That is the thing that lowers the boost level seen by the ECU. This makes the engine run lean and can make it blow depending on how lean it gets.
That is correct.

You need to be ULTRA carefull when fitting fuel cut defencers to evo's;
infact id go as far as to say dont bother .
The boost reading that is taken by the ECU for fuelling etc

The ecu doesn't actually take any measurement of the boost pressure.
The Evo uses a mass air flow meter method to calculate air flow and fuel input.
It calculates the correct fuel input based on the air flow measured through the air meter (karmann vortex type) and the engine rpm. (plus mods for throttle angle, acceleration enrichment, engine water temperature, atmospheric air pressure, atmospheric air temperature etc)
At no time is boost pressure measured.

Other cars such as Cossies use a speed density algorithm to calculate air flow and fuel input.
By measuring boost pressure (MAP - manifold absolute pressure), boost air temperature and engine rpm the ecu calculates the density of the charge air. Knowing this and the speed of the engine the air mass flow input is easily calculated and the fuel injected accordingly.

The Evo is easy to tune as it automatically corrects for more air as it measures exactly how much is entering the engine - thus any mods such as air filter/exhaust/cams/gas flowing/more boost will not upset the fuelling until the standard injectors run out of capacity. The only thing that isn't corrected well is the ignition timing - knock sensor circuit corrects to some extent but for big boost some additional ignition timing control is essential.

With MAP sensor type ECUs if anything in the engine is changed such as air filter/exhaust/cams/gas flowing that affects the air flow characteristics of the engine the ecu cannot compensate for this increased air flow. It does not measure the air flow – only calculates the known air flow for the engine as mapped on the dyno. Improve the breathing at a particular rpm point – eg. gas flowing and the engine cannot measure this increase mass flow of air. Hence the importance of remapping/rechipping this type of ecu when modifations are made to the engine.

Boost controller will not erase fuel cut other than stopping the boost level at a particular rpm (the air mass flow) being too high for the ecu's preset parameters.

Fuel cut is there to prevent the fuel system being run beyond it's maximum.
There are cheats you can use to get around this - higher base fuel pressure/big pump/Apex S'AFC is one.
Big injectors/S'afc or HKS VPC is another.
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I knew how it was measured it was just that I was in bed last night thinking about what I had written (sad I know) and then suddenly realised I'd wrote the wrong thing down and so jumped out of bed, rushed to the computer and corrected myself as quick as poss without having chance to write the full method down.
As for my original post on the thread, I think I was just having a blonde moment ;)


no one was listening any was a typical fox talking ###### moment.....:)

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