Jump to content

Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse

- - - - -

stupid turbo fuel cut idea

  • Please log in to reply
7 replies to this topic

#1 oddcomp


    Subaru Master

  • Members
  • 1,763 posts
  • longview ,wa

Posted 23 November 2003 - 10:45 AM

anyone thought of using a small cheap air pressure regulator on the line that runs to the boost sensor
that sends a signal to the ecu to cut fuel at a certain psi ?

just a guess if you used a air pressure regulator that starts to vent about 1/2 or 1 psi before the fuel cut is activated then the ecu would never know that its in what
it considers a overboost state
run the dumped pressure into the turbo inlet
although i suppose with that small amount of air being automatically bled off it might not be enough to mess up the maf sensor
who knows

just a silly idea

#2 Nug


    Lurker/off-topic poster

  • Members
  • 1,968 posts
  • West Point, VA

Posted 23 November 2003 - 11:25 AM

The honda boys use a one way check valve from a fish tank aeriator. When there is a positive pressure at the maf, it blocks the pressure and the maf stays stady-state. You know what I'm talking about. I just woke up, and I can't think straight.

#3 oddcomp


    Subaru Master

  • Members
  • 1,763 posts
  • longview ,wa

Posted 23 November 2003 - 11:28 AM

i know what you mean yeah
i was just thinking the regulator
would let it function normally until it got to just before fuel cut and dump the excess pressure out of the line to the sensor
seems like it would work better than a check valve is all

#4 WJM



  • Members
  • 7,828 posts

Posted 23 November 2003 - 11:44 AM

I know that on 85/86 with the flapper MAFs, you can unplug the overboost sensor and run as much boost as you want.

On the 'hotwire' MAFs, 87 and up, there overboost is built into the ECU. It receives the signla from the MAF about how muc air is entering, and about the 9psi mark the signal from the MAF becomes a cetin level, and the ECU starts timer, and at the end of that, fuel cut.

I may be wrong, but thats what Ive heard. I know that...hmmmm. I just tohught of something. Too bad the RX is not here, id try it. It seems like the waste gate plumbing is more complex than 85/86 cars. Hmmmm, re route the stuff. do soemthing. *rambling*

#5 oddcomp


    Subaru Master

  • Members
  • 1,763 posts
  • longview ,wa

Posted 23 November 2003 - 10:01 PM

i thought on 87 and up it still had the double vacum sensors one for the dash light and one runs to the ecu to signal boost and how much
and in turn the ecu decides based on the voltage provided from the boost sensor when we are at fuel cut levels ....
or so i thought since my 87 maf'd turbo has the double boost pods
i really need some fsm info on how the ecu reads sensor data to come up with a better idea
anyone got a section on the ecu and turbo sensors they can scan and email?
for 87 and up maf and 87 down flapper systems?
eventually i will just ditch the maf and use my programmable fuel injection controller
but that won't be until i get the wife a minivan and i can have the wagon

#6 rallyruss


    Subaru Master

  • Members
  • 1,653 posts
  • San Jose CA

Posted 24 November 2003 - 12:20 AM

there was a link to the FSM for a 89 ea82 and more up here a while back. I thought junkie was going to add it to the repair manuel?
any way it had a breif description of the operation of the boost control system and I think it did say that the sensor controled fuel cut. could be wrong ( dam short term memory)
hope that link is still around It was verry usefull.

#7 calebz


    Andys Coupe killed my cat

  • Administrator
  • 7,547 posts
  • Tacoma

Posted 24 November 2003 - 01:02 AM

my 87 maf'd turbo has the double boost pods

Thats interesting.. my 87 only has one.. and my 88 only had one as well..and my 88 FSM only shows one. is your 87 an early build? does it have the hotwire or vane style MAF?

#8 oddcomp


    Subaru Master

  • Members
  • 1,763 posts
  • longview ,wa

Posted 24 November 2003 - 09:47 AM

ok now that i feel exceptionally stupid this morning i looked again
mine has one pod and a small box under neath that one and a few vac lines
one runs from the compressor side to the box then to the wastegate

wich according to one of my manuals is what does the fuel cut at x amount of psi

i still think a simple air pressure regulator set to bleed off at a certain psi below the fuel cut would still allow the ecu to add more fuel under boost but not cut the fuel

that was my whole worry with the fish tank bleeder valve type of setup is not letting the ecu get enough signal to open the injectors more

i was thinking of a 86 rx with a vane and 2 pods oops lol
by the way on that car the wastegate line runs right off the compressor fitting

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users