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  #46  
Old 02-10-2003, 09:44 AM
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Quote:
Originally posted by svx_commuter
Yeah that's the baby, the inductor valve. They SM also referes to it as the 'Supercharging Valve". Section 2-7 of the manual has a description of how it improves the volumetric efficiency of the engine, how more air gets into the engine. It's a pretty neat feature on the SVX. I am thinking that it doesn't always do it's thing in the low rpm zone but hey no proof. There isn't any detail on when it opens and closes relative to throttle position. It is very interesting.

Yes it is. I can't remember all the words that "IRIS" entails (Induction Regulating ??? System -- or something like that -- I'll have to look it up). It is a highly tauted feature on the Subaru boxer engines, though.
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  #47  
Old 02-10-2003, 12:11 PM
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Quote:
Originally posted by Aredubjay



Yes it is. I can't remember all the words that "IRIS" entails (Induction Regulating ??? System -- or something like that -- I'll have to look it up). It is a highly tauted feature on the Subaru boxer engines, though.
IRIS stands for 'Inertia Resonance Induction System.' I've attached the page from the R&T Guide explaining the valve. To me, the explanation always sounded a little low on actual information - saying how IRIS is different compared to normal variable-intake systems in operation, but never how it really does what it does.

I never figured that the IRIS valve did a whole hell of a lot. But then, other parts were designed around its use - the intake plenum and dual throttle bodies - so maybe it really does serve more than a marketing function.

I didn't know until reading this thread that the IRIS was vacuum-actuated. Maybe the valve doesn't work on some SVXs, and that's why those cars feel 'sluggish.' Maybe it's an intermittent problem on others, explaining why sometimes the car feels ultra-fast and other times not so much.

I have never given any credence whatsoever to claims that Power Mode did anything but change shift points. Also, I've never accepted anybody's claims that their car sometimes feels like it has more power than other times. But maybe this would explain those claims.

I know that the ECU determines when the IRIS closes or opens, but would it know if the valve didn't open when it should, or was stuck open?
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  #48  
Old 02-10-2003, 12:11 PM
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  #49  
Old 02-10-2003, 12:19 PM
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Quote:
Originally posted by Mr. Pockets


IRIS stands for 'Inertia Resonance Induction System.'

Thanks, Nick. I knew the word "induction" was in there, somewhere.
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  #50  
Old 02-10-2003, 01:31 PM
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Nick that is a great article.
Now all we need is a scan of sec 2-7 from the SM showing the volumetric effeciency verses engine rpm.
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  #51  
Old 02-10-2003, 01:48 PM
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Troubleshooting IRIS

Quote:
Originally posted by Mr. Pockets


IRIS stands for 'Inertia Resonance Induction System.' I've attached the page from the R&T Guide explaining the valve. To me, the explanation always sounded a little low on actual information - saying how IRIS is different compared to normal variable-intake systems in operation, but never how it really does what it does.

I never figured that the IRIS valve did a whole hell of a lot. But then, other parts were designed around its use - the intake plenum and dual throttle bodies - so maybe it really does serve more than a marketing function.

I didn't know until reading this thread that the IRIS was vacuum-actuated. Maybe the valve doesn't work on some SVXs, and that's why those cars feel 'sluggish.' Maybe it's an intermittent problem on others, explaining why sometimes the car feels ultra-fast and other times not so much.

I have never given any credence whatsoever to claims that Power Mode did anything but change shift points. Also, I've never accepted anybody's claims that their car sometimes feels like it has more power than other times. But maybe this would explain those claims.

I know that the ECU determines when the IRIS closes or opens, but would it know if the valve didn't open when it should, or was stuck open?
The IRIS thingy is not vacuum operated, but when it works it affects the intake manifold pressure. It is opened or closed on command from the ECU by a device called the induction solenoid valve.

Good question Pockets as to whether the ECU knows if it is malfunctioning. Presumably it must, but our error codes do not show a fault number for this solenoid. It is possible to check if it is operating properly. The Service manual lists pin 20 on connector B62, and it should read 0 for ON and 13-14V for OFF.

Whether the ECU switches it open or closed is determined by engine speed and fuel injection quantity. However, from the chart in the manual, it would appear it normally is closed at low engine speeds and open at high revs. The point at which it should open for optimal volumetric efficiency is about 4200 RPM.

I have seen posts from people with two cars saying one car goes sweet at high revs, but the other has more pulling power for driving at low revs. Stuck valve or inactive solenoid could explain this all right.

BTW I was not suggesting that the different shift map did anything other than change the shift points. However, in POWER mode you do get more eager access to about 50 hp that is available higher up the rev range. In NORMAL driving on two trannies now, my car shifts up at 000 RPM, never allowing the use of those extra horses without forcing kick-down.

Joe
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  #52  
Old 02-10-2003, 02:49 PM
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Re: Troubleshooting IRIS

Quote:
Originally posted by svxistentialist


The IRIS thingy is not vacuum operated, but when it works it affects the intake manifold pressure. It is opened or closed on command from the ECU by a device called the induction solenoid valve.

Good question Pockets as to whether the ECU knows if it is malfunctioning. Presumably it must, but our error codes do not show a fault number for this solenoid. It is possible to check if it is operating properly. The Service manual lists pin 20 on connector B62, and it should read 0 for ON and 13-14V for OFF.

Whether the ECU switches it open or closed is determined by engine speed and fuel injection quantity. However, from the chart in the manual, it would appear it normally is closed at low engine speeds and open at high revs. The point at which it should open for optimal volumetric efficiency is about 4200 RPM.

I have seen posts from people with two cars saying one car goes sweet at high revs, but the other has more pulling power for driving at low revs. Stuck valve or inactive solenoid could explain this all right.

BTW I was not suggesting that the different shift map did anything other than change the shift points. However, in POWER mode you do get more eager access to about 50 hp that is available higher up the rev range. In NORMAL driving on two trannies now, my car shifts up at 000 RPM, never allowing the use of those extra horses without forcing kick-down.

Joe

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  #53  
Old 02-10-2003, 03:43 PM
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Joe,

Your experience and comments regarding driving the the SVX in respect of gear ratios, the aoto response and power mode are exactly in line with mine.

Driven in D and without the power button activated it is an old man's car.
There is no fun to be had other than with power the power mode button activated and 3 selected. Otherwise as you say, it drives like any other car stuck in overdrive. D is a very tall gear and kills it. However in point of fact it is an overdrive and should be treated as such and should have been marked as such. The sins of poor economy no doubt coloured the thinking.

I have always been critical in respect of throttle response as you are and because of this have recently removed, checked, cleaned and reset the TPS on my car. Although I found little wrong, I think (?) there is an improvement but am not sure until I have another good open road trip. The last one got me a ticket by the way.

Setting the TPS accurately in accordance with the instructions in the manual is not practical and more or less impossible but I have a way of doing this if you are interested.
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  #54  
Old 02-10-2003, 04:54 PM
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INERTIA RESONANCE INDUCTION SYSTEM

This system uses two different inlet systems. An inertia system formed by the long induction tracts, that are kept separate from each other, that gives an increase in manifold pressure. When the IRIS valve opens, the system changes to tuned length short high speed runners that are feed by the two inlet tracts.

I wrote this some time ago.

Subaru uses two inlet tracts separated by a large butterfly valve so that when closed at low RPM there is a smoother flowing 3 branch inlet for each side, inducting 240degs apart, without a plenum in sight.
Because of the long, and increasing diameter of the inlet tract, without any sudden changes in cross sectional volume, the tuned length can now extend right back to the throttle bodies, instead of being terminated at a plenum The shear inertia of the moving charge causes a useful pressure to be present at the cylinder. As one valve closes on a fast moving column of air, the next cylinder opens its inlet valve to take the flow, even though it's piston is stopped at the top of the stroke.
Because the main section of this inertia is developed before the individual cyl branches, this pressure can be passed on from one cyl. to another, thus the induction is assisted not only at the end, but also at the start of the inlet stroke. This is not possible when the low speed tracts end at a plenum chamber.

This is the type of Ram induction that was used successfully by Chrysler in the 60s, to increase the bottom end torque, unfortunately they didn't have a high speed tract to switch to so the top end was lacking. (not that they had much )

At around 4500 RPM the large butterfly valve between the inlet tracts opens, connecting both tracts together, this then forms the large cross sectional volume which terminates the high speed tract at the now formed plenum, that functions as a Helmholts resonator, to allow each cylinder to induct its 550cc of air from the chamber, which is now supplied by two throttle bodies.

What Subaru designers have achieved is a two stage, tuned length, inlet system that spreads the torque from about from 2000 RPM to 5400 RPM, with a very effective ram charging system that operates from just above idle, right up to when the high speed butterfly valve opens to form the plenum. This is where the engine gets it wide spread of torque and strong low speed response from.

Harvey.
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  #55  
Old 02-10-2003, 05:14 PM
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Re: Troubleshooting IRIS

Quote:
Originally posted by svxistentialist

The IRIS thingy is not vacuum operated,
Joe
Ahhh... Joe..... the SM says the solenoid valve opens and closes a vacuum line to the IRIS. So it uses vacuum pressure stored in a reservoir that is controled by an electric solenoid.
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  #56  
Old 02-10-2003, 05:35 PM
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Before everyone gets too wacky over this (is it too late?) the SVX isn't the only car to feature this flap valve. As Alan mentioned the 928 has one, and as far as I can recollect any modern engine with four or more valves per cylinder has one. Harvey gives an excellent explanation on how and why it works.

I believe the original point of this post was why does the engine sometimes seem to jump up and other times it reacts leisurely? There may be a couple of reasons: One, the IRIS valve could be sticky, however I remember my new in '92 car exhibiting the same behavior, at times taking me by surprise. Secondly, and I believe this to be more likely, will take a few words to explain away. One of the easier ways to explain the IRIS is to say that if one were to floor the accelerator from a standstill, the sudden opening of the throttle blades would cause the intake velocity to die off immediately. This is the reason QuadraJets, ThermoQuads, etc. were built with vacuum operated secondaries (for those that are old enough to know what a carburetor is.) The same effect would happen - floor the pedal and the air velocity disappeared, leaving the car in 'air bog' situation until the air velocity came back from the grave.

I'm willing to wager a dollar to a donut most of you will find, that if you pay attention, the engine will romp more reliably when you don't just stab the pedal to the floor. I find it better to go 25-30% throttle until about 3500-4000 rpm , then stand on it quick enough to set the 'power' lamp. I drive a lot of cars in my job and I've found that almost all multi-valve engines perform better this way, it's not just an SVX or Subaru phenomenon.
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  #57  
Old 02-10-2003, 05:51 PM
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Re: Re: Troubleshooting IRIS

Quote:
Originally posted by Aredubjay



<Envisioning Joe balancing manual on lap, trying to type and keep it from falling into the floor -- been there! >
Wot??

Me balance emmanuel on my lap??

My Missus will have a thing or two to say to you, Randy!!

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Old 02-10-2003, 06:04 PM
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Re: Re: Troubleshooting IRIS

Quote:
Originally posted by svx_commuter


Ahhh... Joe..... the SM says the solenoid valve opens and closes a vacuum line to the IRIS. So it uses vacuum pressure stored in a reservoir that is controled by an electric solenoid.
OK, OK, ya got me John.

However, I was responding to Nick saying the butterfly valve was, and I quote, "actuated" by vacuum.

Over here, actuated implies control. So farther up the command chain, the ECU actuated the solenoid, which changed the voltage to open the valve to let in the vacuum to change the butterfly position to improve the charge velocity yadda yadda

It was a lot easier in the old days when our feet did most of the going and stopping, and our hands shuffled it in the general direction of "home"

Joe
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Old 02-10-2003, 06:05 PM
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Quote:
Originally posted by Beav
I find it better to go 25-30% throttle until about 3500-4000 rpm , then stand on it quick enough to set the 'power' lamp.
arrrgh! i don't have a power lamp! i wonder why they did away with it on the later models (or just '97's?) it would be interesting to see when it was in power mode, and what driving conditions would bring it on.
i'll have to rig up my own system - when power mode kicks in, strobes and a revolving police light come on, with a recorded voice of Michael Buffer saying "Let's get ready for Power Mooooooooode!"
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Old 02-10-2003, 06:21 PM
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Quote:
Originally posted by Trevor
Joe,

Your experience and comments regarding driving the the SVX in respect of gear ratios, the aoto response and power mode are exactly in line with mine.

Driven in D and without the power button activated it is an old man's car.
There is no fun to be had other than with power the power mode button activated and 3 selected. Otherwise as you say, it drives like any other car stuck in overdrive. D is a very tall gear and kills it. However in point of fact it is an overdrive and should be treated as such and should have been marked as such. The sins of poor economy no doubt coloured the thinking.

I have always been critical in respect of throttle response as you are and because of this have recently removed, checked, cleaned and reset the TPS on my car. Although I found little wrong, I think (?) there is an improvement but am not sure until I have another good open road trip. The last one got me a ticket by the way.

Setting the TPS accurately in accordance with the instructions in the manual is not practical and more or less impossible but I have a way of doing this if you are interested.
Trevor, we old guys gotta stick together.

Whenever I mention this Top Gear is Like Swimming in Treacle business, there is usually a post or two mentioning that some cars are sluggish or not tuned properly.

Beav's point is a very good one, and in fact, I don't use POWER mode these days because of the restless hunting up and down the box, instead I manually select 3 or 2, and let POWER come in and hold onto it if it wants to.

Probably the box would be OK if it did not have the learning function crap. It does not hold onto low gears long enough with the standard shift map, and it oughta select a lower gear for a dab of the pedal, rather than carpet mashing. The economy people had too much say. This car was designed in the late eighties.

If you buy 230 horses, you should be allowed to ride ALL of them.

Right, Randy, what were you about to say about harims??

Joe
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