boost question

91scoobiesubie · Post by **91scoobiesubie** » Sat Jul 19, 2003 8:19 pm

would 10 psi be allright stock if so how do i do it?

georryan · Post by **georryan** » Sat Jul 19, 2003 8:26 pm

Some have done it without consequence, but most wouldn't recomend it without an intercooler. You'll need a boost controller to raise your boost, though.

-Ryan

check out www.legacycentral.org

Lots of good info and also check out the search engine on this bbs, there is lots of discussion the topic. You'll probably find more info through searching than you would by asking the question because of all the talk so far on the topic.

morgie · Post by **morgie** » Sat Jul 19, 2003 10:01 pm

i run 12-13-14psi daily (depends on temperature) without intercooler since one month, and before that i was 12psi since about 10 months.

As far as i know, car is still running

But, little note : Running 14psi dont seems to increase engine HP at all compared to 12psi... probably because of intake air temp. / timing. i'll seee with the Intercooler.

legacy92ej22t · Post by **legacy92ej22t** » Sat Jul 19, 2003 10:18 pm

Before you mess with your boost at all you'll need a boost gauge,then worry about a boost controller.I'd get an intercooler first too just to be safe

91White-T · Post by **91White-T** » Sun Jul 20, 2003 12:03 am

Just pull the hose off the wastegate and enjoy!
(Just kidding, please don't really do this)

91scoobiesubie · Post by **91scoobiesubie** » Sun Jul 20, 2003 2:17 am

i already have the gauge what kinda boost controler do you guys recommend and how do i hook it up

legacy92ej22t · Post by **legacy92ej22t** » Sun Jul 20, 2003 5:50 am

http://www.boostcontroller.com/index.php

The Hallman mbc's are nice and reasonable.It will come with directions on how to install

vrg3 · Post by **vrg3** » Sun Jul 20, 2003 6:17 am

I say don't increase boost until you've done something to warrant it (most likely intercooling, but can also be improving exhaust flow or something else that reduces underhood temperatures). The stock boost setting was chosen by Subaru engineers to match up with the stock configuration and provide a good safety margin and ensure longevity.

Redline Dreamz · Post by **Redline Dreamz** » Tue Jul 29, 2003 3:39 pm

morgie wrote:i run 12-13-14psi daily (depends on temperature) without intercooler since one month, and before that i was 12psi since about 10 months.

As far as i know, car is still running

But, little note : Running 14psi dont seems to increase engine HP at all compared to 12psi... probably because of intake air temp. / timing. i'll seee with the Intercooler.

Hook a SAFC up to that thing and check your counts of knock.... bet its hittin close to triple digits there bud

I wanna know how you dont hit fuel cut.... FrmRgz2rchz car has hit that a few times at 12-15psi with the TD05 in it.

An intercooler is a good idea to have with double digit boost. Even a cheap Saab900 side mount can be fited in as a top mount on a EJ22, which is what FrmRgz2rchz is doing. He can run 10-12psi on 92 octane and be fine as long as the air temp stays below 90

morgie · Post by **morgie** » Tue Jul 29, 2003 4:06 pm

Redline : yup i'm awaire of that, that's why i run 11-12psi . How do you manage to read knock sensor if you dont have a SFAC ? can it be done with a multi-meter ? (in "Count" mode or something) .. .

for the FCD, have a look at my Poor man FCD : viewtopic.php?t=1505

I have an Audi 5000 intercooler, end-tanks will be customized to fit in MAX a month. this IC is big and will probably do the job well..

I inserted a electronic house thermometer in the intake tubing (just in front of the Throttle body). At 120km/h cruising, i was getting 55-60°C (131-140°F) , and WOT, the thermometer Max-out at 70°C and it dont takes a lot of time to reach that limit, so i estimate 80-90°C intake temps... pretty hot. (176 to 196°F)

Am i stupid or crazy or dumb or ignorant or unaware of danger ? maybe a combination of all of that

JasonGrahn · Post by **JasonGrahn** » Tue Jul 29, 2003 4:28 pm

I'm surprised this thread got this long without someone calling out the search function of this BBS as well as the search functions that take care of the REST of the world.

This has been covered.

Please know that I know that I am perceived as an ass. But please also refer to another post where you asked a question that had already been covered: viewtopic.php?t=1690&highlight=

So far as I see, his question was answered on the 2nd post.

Redline Dreamz · Post by **Redline Dreamz** » Tue Jul 29, 2003 5:40 pm

morgie wrote:Redline : yup i'm awaire of that, that's why i run 11-12psi . How do you manage to read knock sensor if you dont have a SFAC ? can it be done with a multi-meter ? (in "Count" mode or something) .. .

I inserted a electronic house thermometer in the intake tubing (just in front of the Throttle body). At 120km/h cruising, i was getting 55-60°C (131-140°F) , and WOT, the thermometer Max-out at 70°C and it dont takes a lot of time to reach that limit, so i estimate 80-90°C intake temps... pretty hot. (176 to 196°F)

Am i stupid or crazy or dumb or ignorant or unaware of danger ? maybe a combination of all of that

Honestly, that is a question i dont know the answer to man... im sure you could read it with a multimeter, but i wouldnt know what to look for. If you have a Chiltons or a Haynes manual for you car im sure it says in there somewhere what normal output voltage should be and the whole range of voltages you may see.

As for your air intake temps....

i think your all of those words you listed as well as LUCKY. However, as long as your using high enough octane fuel you should theoreticaly be ok from detonation. My personal suggestion is *in a very redneck voice* "Eh man, back er down!" Just lay off the boost a bit till you can snag an IC from somewhere.

Post by **Legacy777** » Tue Jul 29, 2003 6:19 pm

A S-AFC will not read knock counts. I think an S-AFCII will, but it's quite a bit more.

Plus it's not really a count. The knock sensor is a simple peizo-electric sensor. The crystal changes resistance, and the output voltage from the ECU will change, when it get's it back, it interprets that change in voltage for knock, and will adjust timing and the lot.

I've watched the knock sensor on my select monitor and for the most part, it will read zero under normal driving. There were a couple times I'd get a slight change in the knock sensor readings, and that was at a certain throttle, which seemed weird....more like a resonance causing the knock sensor to tweak out....

vrg3 · Post by **vrg3** » Tue Jul 29, 2003 6:53 pm

It doesn't actually change its resistance; the piezo element produces a small voltage when it's vibrated. I have heard of people hooking up audio amplifiers to knock sensors and then listening to the engine through headphones.

It would be interesting to see how the knock count differs between N/A and turbocharged Legacies.

Post by **Legacy777** » Tue Jul 29, 2003 11:20 pm

that's right.....I knew it did something with voltage

Redline Dreamz · Post by **Redline Dreamz** » Wed Jul 30, 2003 4:06 pm

yea its kinda the opposite of a quartz watch. The quartz in a watch resonates at 38,864 times /second when 3V+ is applied to it. I think the exact opposite happens with the knock sensor.... the # of resonations changes and causes the voltage to rise or drop....

Thats probably the best educated guess i could make.

vrg3 · Post by **vrg3** » Wed Jul 30, 2003 5:05 pm

Well, since we're discussing this trivia anyway... :)

I don't believe it is a resonance phenomenon. I don't think quartz is piezoelectric. The knock sensor has some other kind of crystal in it which is piezoelectric. Basically, when the crystal is deformed, it causes a small electromotive force. (The reverse is also true -- if you wanted you could play music through a knock sensor by running the output of an amplifier into it.) So as the engine vibrates, it pushes the crystal in and out ever so slightly, resulting in a small AC signal. When detonation occurs, the crystal gets pushed much more, so the amplitude of the AC signal increases.

I would guess that the ECU just thresholds this signal and if it exceeds a certain limit it calls it "knock." The limit is probably fixed although I suppose it could be dynamically chosen based on the amplitude of the signal at idle when starting up.

I really want to hook an earphone up to my knock sensor now. I'm really curious.

morgie · Post by **morgie** » Thu Jul 31, 2003 12:41 am

VRG3 : take a look at those articles...

DIY knock detection: fifteen dollars and fifteen minutes - cheap, easy and very effective!
http://www.autospeed.com/A_0353/cms/article.html

this one is an evolution of the previous.. but i dont have access.
http://www.autospeed.com/A_1353/cms/article.html

vrg3 · Post by **vrg3** » Thu Jul 31, 2003 12:51 am

Yeah, that's a lot like I was thinking of, Morgie, except that I was just gonna use the stock knock sensor instead of the microphone. The only issue would be not loading the sensor too much. I was thinking an audio frequency op amp set up as a voltage follower would take care of it.

Actually I'm thinking of setting it up to play the signal from the knock sensor through my stereo. That would be cool. You'd hear the engine through the speakers as well as directly. :)

Autospeed has a lot of cool little DIY articles.

Redline Dreamz · Post by **Redline Dreamz** » Thu Jul 31, 2003 5:01 am

SWEET!!!! i learned something new today

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boost question

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