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inline
03-08-2001, 06:07 PM
I found a company that will make performance camshafts for the SVX. Does anyone have any idea what effect this would have on HP, if any? I am guessing the engine would have to come out to change them.


Chris

Rev Hard
03-18-2001, 04:20 PM
effect on the HP numbers depends on the lift and duration of the new cams. The thing to remember here is you may get to a point where the engine idles kindof rough on the street due to a large lift/ Long duration. You may or may not like this.....

Also the cams could be changed while it was in the car i would believe. you dont have to pull the motor to get the valve covers of due you?

And one more. are these NEW cores the cams would be made on? If not i dont think i would be as interested. Re-grinds require the change of cam timing. And i have heard mixed reviews of hardwelds...

OH, do you have a price on the cams?

PAUL!

inline
03-18-2001, 05:16 PM
You can check out the companies' web site here:
www.paeco.com (really weak site, you can e-mail them)

Not sure if they are new cores or not.
Price should be around $230 per cam.


Chris

Myxalplyx
06-08-2002, 03:27 PM
Originally posted by inline
You can check out the companies' web site here:
www.paeco.com (really weak site, you can e-mail them)

Not sure if they are new cores or not.
Price should be around $230 per cam.


Chris

All this time an no-one has had their cams regrounded or done up from Paeco Industries?

SVXMAN2001
06-11-2002, 09:32 PM
I just received a catalog of everything paeco does for all imports, it is a pretty thorough magazine. Definately worth considering, but be willing to pay big bucks

huck369
06-12-2002, 05:46 AM
Originally posted by inline
You can check out the companies' web site here:
www.paeco.com (really weak site, you can e-mail them)

Not sure if they are new cores or not.
Price should be around $230 per cam.


Chris

$230 per cam?
Since there are four cams in the SVX that totals $920 :eek:
To much for me, that's about what I spent on my 5-Speed conversion:confused:

Motorsport-SVX
06-13-2002, 11:59 PM
if engineered wrong you can lose hp too.......
and would you do intake or exhaust cams..?
reground cams arent all that great of quaility anyways...
Its a nice thought but if not designed perfectly, even possibly with a computer dyno, too much risk for the $........IMO

cdigerlando
06-14-2002, 11:34 AM
I agree with Dayle. Most people I talk to regarding cams regret doing it. It is expensive and make the car unreliable. Even on cars such as the Mustang, cams can be problematic. You would think that these problems would be worked out on one of the most common high performance engines in America. I would need to have a really reputable company that works with subaru engines do the work before I would trust them.

Motorsport-SVX
06-14-2002, 11:58 AM
Chuck, actually I had a Motorsport E303 cam in my Stang and it ran real well, with Mustangs its really important that the car has mass air conversion if not euipped so from the factory on EFI cars. But true also, there are some stories of some others with the same set up that for some reason didnt run as well...choppy or erratic idle etc. Usually caused by vaccum leaks or whatever
caused after install.

solarsvx
06-14-2002, 12:42 PM
i would have to agree on every one else upgrded cams on imports dont work well unles u have a vtec wich i seen them help. as for a svx doing cams,, no way ,, theres 4 of those bastereds LOL and 2nd imagine puting them in gesshh,, to get what 5 hp if lucky and huge headaches.. most people upgrade cams as alost chance to get power,

i know for a fact cams for a dsm does nothing they sell bullfrog 264 cams for 400 set of 2. my freind chad had actually lost power with this set up he ended up puting the factory cams back in , not to mention it idle like a beat up ford, huge lobes

just my 02


james
92 subaru svx

oab_au
06-15-2002, 06:55 PM
The stock timings are; inlet opens 2*BTDC closes 54*ABDC, 236* duration,. lobe center 116*ATDC, 11.5mm lift.

Exhaust opens 55*BBDC closes 9*ATDC, 244*duration, lobe center 67*ABDC , 11.8mm lift.

This engine is is very efficient as is. Increasing the duration more that it is, will interfere with the inlet and exhaust tract resonance. This engine is designed to have one valve open on each side at a time, more that 240*has two valves open together.

Longer exhaust timing would need a change in exhaust headers, to stop the interference between cylinders.

Longer inlet timing, would interfere with the inlet ram charge effect, that provides the torque at low revs.

More valve lift would give more torque through the range. Though 11.5mm for a 4 valve engine is close to maximum, may be 1mm more?.

Retarding the inlet lobe center, would move the torque curve, further up the rev range. Though too many other things are set to chime in at the standard torque curve eg. inlet and exhaust track tuned length, gear box change points, fuel and ign. maps.

It would be hard to improve the efficiency of this engine, it has already been done. The way to go is to increase the intake air density, eg nitrous, supercharging.

Harvey. ;)

cdigerlando
06-16-2002, 12:34 AM
Good post. Very informative. I bet the car could be maximized to a forced induction application, but the research to go into it and do it right would be painstaking and expensive. Besides, the way the engine is designed stock it has great torque througth the rev range already. Thats why the use them for airplane engines. I will check with Rebello and see what they recommend, since they modify the engine for airplanes

Trevor
06-16-2002, 01:02 AM
Thanks Hervey, excellent info.

The timing is quite mild and I wonder what effect the variable set up has on this when it comes into play. Furthermore having no information on it I have not a clue regarding its workings.

cdigerlando
06-16-2002, 01:32 PM
What variable setup?

oab_au
06-16-2002, 06:56 PM
Yes the valve timing does seem mild, when compared to a two valve engine.
A Ducati Desmo two valve engine with a cylinder capacity of 550cc (same bore & stroke as the Svx), used timings of, Inlet opens 63*BTDC closed 83* ABDC, 326* duration
Exhaust opens 80* BBDC closed 58*ATDC, 318* duration
13mm lift, 121*overlap!!!!! :eek:

The later 4 valve Ducati have a timing very close to the Svx's. Though you have to go to the SP(sport production) versions to get the 11.5mm lift.

The 4 valve set up has much less restriction to the 2 valve. There is less lag between the maximum piston speed and the maximum air speed. The valves don't have to open as early to get the air flowing. More of the compression stroke is used for compression. More for the exhaust stroke is used for power.

Variable valve timing, usually means using a scroll spline between the camshaft and the drive gear, moved by a piston to rotate the cam. This allows the camshaft to be moved, in relation to the drive gear, to retard the inlet timing, as the rpm rises. Sometimes the exhaust cam is also moved as rpm rises. In this case the exhaust timing is advanced.

The idea of variable timing is to match the fully open position of the inlet valve to the maximum air speed.
If we look at the way the inlet works. As the piston starts to move down on the inlet stroke it accelerates from stopped at the top to maximum speed at about 83*ATDC. So if we have the valve fully open at this point, we will get maximum air flow into the cylinder.

This will work at low speed but as the engine speed increases, the air flow starts to lag behind the piston due to the restriction the valves. So we usually set the lobe center(when the inlet valve is fully open) to the rpm that we want maximum torque, 116*ATDC on our engine.
In other words this is where the air speed, is at it's maximum, at this rpm. If it suits this speed it cannot match at other speeds. It would be better to come back to about 100* at lower speeds.
This is the reason for variable valve timing to try to match the maximum air speed to the variable engine speeds.

I don't know how Subaru is doing it, but it would be along these lines.

Hard to explain without waving arms about. :D
Harvey.

cdigerlando
06-16-2002, 07:27 PM
Thanks for the timing lesson. It sounds like the Ducati is a good engine to compare to the SVX, although I wonder which engine is more efficient. I also wonder how a turbocharger or a supercharger would effect the intake air speed. I'm sure the dual resonation that occurs with the Iris system would also effect the degree of air lag that would occur. These effects could not be compared to the SVX, since I'm sure the inake geometry is significantly different. Thanks again.

oab_au
06-16-2002, 08:27 PM
Originally posted by cdigerlando
Thanks for the timing lesson. It sounds like the Ducati is a good engine to compare to the SVX, although I wonder which engine is more efficient. I also wonder how a turbocharger or a supercharger would effect the intake air speed. I'm sure the dual resonation that occurs with the Iris system would also effect the degree of air lag that would occur. These effects could not be compared to the SVX, since I'm sure the inake geometry is significantly different. Thanks again.

Hi Chuck, Yes the Ducati is THE motor. Desmodromic valve gear. gives great control over the valves, no more tangled valves on a over rev down shift. As to which is the most efficient? may be the Svx, but the Duck will rev to 12k to make more hp. Look how the V Twins blow the 4cylinder bikes off in the World Super Bikes.

Blowing the Svx won't worry the engine design. Everything will act the same, it's just using a more dense air pressure. Torque increases in step with boost pressure, 7lbs will give a 50% increase in torque, 14.7lbs 100% increase.

Harvey :)

mohrds
06-16-2002, 09:50 PM
Harvey,

I've been following along and I have a question:

How does the IRIS get affected by pressurizing the intake? In order to help a turbo/supercharged engine, would a new intake that is all plenums, no IRIS be better?

I am for the moment not including any discussion on fuel delivery, spark, or computer control being affected. Just curious about the intake for now. There has been good discussion on the these other aspects in the past.

Doug

cdigerlando
06-16-2002, 10:04 PM
Originally posted by mohrds
Harvey,

I've been following along and I have a question:

How does the IRIS get affected by pressurizing the intake? In order to help a turbo/supercharged engine, would a new intake that is all plenums, no IRIS be better?

I am for the moment not including any discussion on fuel delivery, spark, or computer control being affected. Just curious about the intake for now. There has been good discussion on the these other aspects in the past.

Doug

Good question. I have a turbo, and I was thinking of disabling the iris. I just don't think it will do that much for the engine under positive pressure. I could be wrong though. It is really over my head.

Trevor
06-17-2002, 05:29 AM
Thanks again Harvey,

I am fully conversant with the principals involved in valve timing and inlet and exhaust design having done a lot of work on my own racing specials. I am interested in the way variable inlet timing is achieved in the SVX engine and the degree of advance this provides. The valve timing up in the rev. range will be quite different from the static figures which even with a large valve area would mean a drop in performance above 5,000 RPM.

You have not mentioned one of the major factors involved in valve timing i.e. the fact that overlap causes exhausting gases to create a depression on the inlet side thus assisting charging. Air (mixture) flow is not solely dependent on piston movement. Gas momentum has considerable effect.

The figures you quote for an exotic motorcycle sure are pretty wild and I bet there is no usable torque at all below 4000 RPM or more likely 6000. My little 1267 c.c. 1971 Subaru FF1 has quite severe timing but is remarkably tractable at low revs. but really comes on song at about 4500. Valve bounce starts at 7300 and is not a bad crude rev. limiter!

Figures are. 40-76, 76-40. The even timing is classic stuff. It is a special production sports model, the standard timing being, 24-64, 70-18.

You have made this an interesting thread.

oab_au
06-18-2002, 08:09 PM
This is becoming more involved, but I'll push on.

Firstly the IRIS will operate the same blown or not. In Chucks case it will provide the bottom end torque that the turbo lacks. The manifolding won't cause restrictions or problems when on boost. It will still work the same. Don't take it off or it will die in the ass at less than 3000 rpm.

No Doug, the IRIS works just the same up in the mountains as down at the coast. Blowing it is just going down lower than the coast to a much higher air pressure. Every thing works the same only more air pressure means more torque.

Yes Trevor, valve overlap died with pollution control, too dirty in the hydrocarbons. Though Subaru found a way of replacing it with the Inertia Resonate Inlet System. I wrote about it before under " Svx inlet design" may have been on Yahoo.

The exhaust is still used to assist the negative pressure, at the end of the the exhaust stroke. But the Inertia of the inlet air flow produces a positive pressure at the opening of the inlet valve to start the flow into the cylinder, even though the piston is stopped at the top of the stroke.

The principals of the IRIS are contained in the fact that the two harves of the engine are separated, so that the 3 cylinders on one side induct every 240 *, thats why it is important to keep the duration of the intake opening down to 240*.

As the No.1 cylinder accelerates the air flow down the long track, the kinetic energy developed, wants to keep the flow going. When the first cylinder starts to close it's inlet valve on this energy, the pressure at the valve end of the manifold will rise to above atmospheric. When this valve closes the next valve opens to a high pressure that starts flowing into that cylinder. This way the inlet air flow is not stopped at the.end of one induction then started by the next it is a constant flow.

As the engine speed increases above 3000, the flow starts to lag behind. Thats when the butterfly valve between the two inlet tracks opens. The system then changes to a resonate system. The branched area of inlet manifold, with the butterfly valve open now forms a plenum chamber that terminates the tuned pressure wave, at that point. So that we now have a short, tuned length track, of about 14" that will resonate at about 4500.

Harvey.
p.s. gota stop now. I run on solar, wind power, It's winter now not much sun, so not much computer time. :)

wawazat??
06-18-2002, 09:34 PM
Originally posted by oab_au

Hard to explain without waving arms about. :D
Harvey.

Maybe this can keep your system powered up Harvey ;) :D :D :D

If so I want a photo! Gotta be hard to type though!

Todd

Trevor
06-19-2002, 02:39 AM
Thanks for expending all that energy both personal and electrical. I hope that both are not difficult too recharge! Much appreciated.

Is the system exclusive to Subaru or do others with boxer engines or a V configeration use the same or a simillar arrangement ? If it is as good as it would appear exclusive rights would be of very real commercial advantage.

May the wind blow and the sun shine upon you. Trevor.

oab_au
06-19-2002, 07:02 PM
Originally posted by Trevor
Thanks for expending all that energy both personal and electrical. I hope that both are not difficult too recharge! Much appreciated.

Is the system exclusive to Subaru or do others with boxer engines or a V configeration use the same or a simillar arrangement ? If it is as good as it would appear exclusive rights would be of very real commercial advantage.

May the wind blow and the sun shine upon you. Trevor.

I built up my power system, that has run OK for 15 years. Now there is a 3 year old grand kid who thinks TV is the main stay of life.:rolleyes:

The IRIS is not a new idea, though no one has used it so effectively as Subaru has. Chrysler used a form of it in the early 70s on the slant six and V8s. long inlet track, on the V8s the four barrel carbs mounted over the opposite head. They called it "Ram charging". It only added positive pressure to the end of the inlet phase.

To my knowledge Subaru is the only one to have it add positive pressure to the start and end of the inlet phase. You could only do it to a 3, 6, 12, cylinder engine. As the inlet has to be arranged to have one inlet valve closing as the next opens.

Subaru has designed this engine to operate as two 3 cylinder units. One cylinder inducting every 240*. so with the inlet duration being 236*, one valve is closed for 4* before the next valve opens.
This short closing phase causes the rise in pressure in the inlet track, from the inertia of the air flow, to produce a positive pressure of about 4 to 5 PSI .
When the next inlet valve opens this pressurised air flows in like it was supercharged to the tune of 4 to 5 PSI. It's inlet phase accelerating the flow for the next cylinder.

The inertia track extends from the inlet valve, back to the mass air flow sensor. This long, large dia. pipe contains the large volume of air that produces the FREE energy.

There is also another inlet phase, that starts at about 2000rpm. When the longer tuned length of the inlet, from the valve to the end of the throttle body, starts to resonate to produce a positive pressure in the cylinder. This continues till the butterfly valve opens, to change the track to the short, high speed track
at about 3200? rpm.

The 4 cylinder engine would need a inlet duration of 360* to have the same system. They just have the long track, to pressurise the end of the inlet phase.


I just love the way this car was designed, like no other. The engineers must have a ball. :)

Harvey.

Templar
06-19-2002, 10:48 PM
Hey Harvey,

I am here to start another fight. No, Just kidding.

Actually, I am very impresses with your knowledge of the valvetrain workings. I even have a question for you, though it may be covered elsewhere, it is very late here and I am too tired to look for it. I was just wondering if Subaru had the insight to use the IRIS system on the new EZ30 engine?

oab_au
06-20-2002, 06:29 PM
Originally posted by Templar
Hey Harvey,

I am here to start another fight. No, Just kidding.

Actually, I am very impresses with your knowledge of the valve train workings. I even have a question for you, though it may be covered elsewhere, it is very late here and I am too tired to look for it. I was just wondering if Subaru had the insight to use the IRIS system on the new EZ30 engine?

EZ30? I guess that is the new 3 liter 6. No I don't think so. I don't believe they will use it on any other engine. Mainly because they will never build another car like the SVX.

This car was designed from a clean sheet. Designed as an integral unit, every section to function together as a whole.

It was to be a 'no compromise Grand Tourer'. As such it has a very high overall gear ratio, 2.45:1 to enable it to cruse at 135 MPH at 4500 RPM, peak torque revs.

What other car does 50 MPH in first gear?. Because of this gearing, they realised that at the low engine speeds, that it would be driven, eg. 1500 RPM at 45 MPH in DRIVE, it would lack torque in this area. So they designed the IRIS to incress the torque at these RPMs. As you can see it is a very long inlet track, and would be hard to accommodate in a smaller engine compartment.

Though the main reason would be that, every other car that they build, is geared lower, with an overall ratio of 3.5 or lower.
With this lower ratio there is more torque available at lower RPMs, so the IRIS is not needed.

As Huck, Brian, Dayle and others have found out, 4.11:1 final drive ratio, transforms the 'off the line performance of the car. Though if it is to be given the big stick, I would go for the auto fitted with 4.11 final drive ratios. It will handle more torque than the normal 5 speeds that are available, without going to an Australian Hollinger dog box. $$$$$$$$$

All the best Kent ;) .
Harvey.