Activa boost - A detailed explanation

MikeT · Post by **MikeT** » 22 Jul 2008, 15:38

Gareth, seeing as your boost is controlled by the ECU in stock form and to utilise a controller you need to bypass the ECU...

How does that effect the ECU - ie. would it log a fault or try to make corrections on an assumed fault with the controller?

XantiaMan · Post by **XantiaMan** » 22 Jul 2008, 16:09

MikeT wrote:Gareth, seeing as your boost is controlled by the ECU in stock form and to utilise a controller you need to bypass the ECU...

How does that effect the ECU - ie. would it log a fault or try to make corrections on an assumed fault with the controller?

The ECU is mapped according to boost/load if the boost controller is disabled but still plugged in, it will still actuate the BMV but the map sensor in the ECU will know how much boost the engine is running at any one point and will set the timing based on load/boost.

No fault code as the ECU thinks everything is normal!

The BMV will be opening and shutting trying to regulate the boost as normal but the important part of the ECU that being the ignition timing and fuelling will still be operational and blissfully unaware that any changes have been made.

handyman · Post by **handyman** » 23 Jul 2008, 10:04

Hello Gareth, really good write up for all us Activa nuts. Very useful information. Shall be tweaking one of mine shortly to see how differently it goes. Thanks.

Handyman, IKBA

Gnerk · Post by **Gnerk** » 07 Aug 2008, 19:45

You know guys, I always regretted not buying a Xant 2L T petrol back in 2002. I went out one Sunday afternoon to escape SWMBO and my (then) new born

and took myself off to a garage advertising a said Xant and a Mondy V6.

Garage was shut, so went to another advertising a Scoobt Legacy 2L T. That was open and...well, the short version is I bought it (after getting SWMBO and newborn to check it out

The Subaru was pretty nippy and reliable, but I always regretted not getting the Xant cos I would look at GSF part prices and wish Jap cars had a similar service.

To be fair, tho, the Subaru never, ever let me down in 3 years of ownership. I'd probably have it still now if fuel prices stayed at 75p a litre and the seats had been more comfy.

Good write up on the turbo BTW. V Interesting, even tho I have left my petrol heads days behind. If octane rating is an issue, it might be worth considering a petrol extender such as toluene (pay the tax

). Tolly has a RON of ca. 120 and is significantly denser than petrol (i.e. more fuel per litre). As a result, F1 teams used to run toluene in the 1980's in 1.5L turbo cars with restricted fuel tank capacities.

Not sure if octane is basically pro-rated or not? i.e. Does 40L of 95 RON RUG + 10L of 120 RON toluene = 100 RON fuel? Anyone know...????

XantiaMan · Post by **XantiaMan** » 07 Aug 2008, 20:18

Toluene, great stuff for cleaning spray guns but it is pretty harsh on rubber seals!

After resetting the ECU it pinks less now anyway and i've been using 95 octane only, it will still pink if really pushed but at 5-8ppl litre cheaper, isnt worth usingnsuper yet.

I've used Millers octane booster in the past and found it excellent, TBH i would only use it for track days or Santa Pod, which should hopefully be coming up before the end of the year.

Gnerk · Post by **Gnerk** » 07 Aug 2008, 20:30

Re: tolly. Put nitrile rubber seals in?

XantiaMan · Post by **XantiaMan** » 07 Aug 2008, 20:42

Gnerk wrote:Re: tolly. Put nitrile rubber seals in?

Viton are just as good

Not worth the effort as you can get fuel to 103 octane (Vpower) and
Milllers CVL Turbo (up to 4 octane points) for very litte effort. 99-100 octane is enough IMO.