Need some professional advice on cams

[Trevor]

Originally Posted by oab_au

I would like to continue to show why, the way we go after power has changed, with the introduction of four valve engines. It will explain why the things that we used, to modify a two valve, and what most hot-up books have taught us to do, no longer are the way.

When we worked a two valve, we used the biggest inlet valve that we could fit in the head. The biggest lift that the valve gear could operate, and the most duration that would allow the engine to start and idle. To assist cylinder filling we used the energy in the inertia of the inlet and exhaust gas. At the end of the inlet stroke, we relied on the inertia of the incoming gas to keep it flowing into the cylinder even though the piston is rising, forcing more gas into the cylinder. We used the inertia of the exhaust gas to create a vacuum in the cylinder, so the inlet gas would be sucked into the cylinder, when the inlet valve open, on valve overlap. To get the engine to operate at high rpms, long duration's were used, inlet valves opened at 60* before TDC, and the exhaust didn't close till after 50* after TDC, valve overlaps in the 100* to 140* were used. Even with all this, it was difficult to get the engine to produce power over 6000 rpm, and still have it with a useable low rpm torque.

The reason for this was in the type of energy we used to perform the cylinder filling. The gas inertia was too slow to allow the filling as the rpm increased. With the coming of the four valve, there was no need for the long duration's, and high valve lifts, as the four valves provided the breathing to run into the 6 to 7000 rpms, without the need for it. As we sort more HP at the higher rpms, we had to use a faster energy source to assist cylinder filling. Sonic pressure waves took the place of the gas inertia. We use a tuned length, resonate inlet tract, that develops negative pressures in the cylinder to draw more gas in.
Instead of a vacuum to start the inlet flowing at valve overlap. We use the sonic pressure waves developed in the exhaust pipe to develop a negative pressure in the cylinders combustion chamber, to deliver an intense start to the sonic pressure wave that will travel the tuned inlet tract, to produce the negative inlet pressures, that will fill the cylinder.

The change from inertia energy, to sonic pressure, has allowed us to rev the engine as hard as we like, as instead of the energy decreasing as the rpm rises, the sonic pressures become more intense as the speed rises. This changes the way we build exhaust systems, as they are the providers of cylinder filling. It is more important to create an intense start to the inlet pressure wave, than to use valve over lap to draw the air in.

This is why the modern four valve engine is so different to the older two valve, in its tuning, but that is progress, and we have got to move with it or fall behind.

Edit P.S. The basic principle will be known to most and is very straight forward. A charge egnites in the cylinder and exits during the exhaust stroke as a lump of exhaust gas. It has weight and travelling down the exhaust pipe at speed results in a following low pressure wave. By having the inlet valve lopen before gthe exhaust valv e closes

Harvey.

I see that Harvey claims that there are differences in principle in regard to cylinder filling in respect of two and four valve engines and that this has to do with a strange change from "inertia" to more modern and sophisticated "sonic pressure waves". The claim is apparently, that the law of physics relies on valve numbers not valve area and that there is no reatonship between "sonic pressure Waves" and "inertia".
Differences which in modern times must be taken to account, when considering normal atmospheric induction, involve fuel injection and electronic engine management, not the BASICS of valve timing.

Those who do properly understand in a practical sense, think along the lines of simple "slugs of gas" regardless of the frequency/sound or speed of motion, even though this may not impress your "automotive engineer". The verbose text, once again designed to impress, may elude some but BS is clear to me.

I am concerned that one member has already been confused towards thinking that a different principle applies regarding valve timing, in respect of a pushrod engine and a twin cam four valve engine, or whatever. There is no difference, there has simply been improvements in the mechanics and as a result efficiency. What is more, not much is truly new in poppet valve engine design. Production methods have made possible what was previously too expenxsive.

Amplification and confirmation of the alleged facts, so blatantly stated, would make interesting reading.

Edit P.S.

The basic principle involved is quite straight forward and will be known to many. In very simple terms, when a charge in a cylinder is fired and exhausts as a lump of gas, it has weight and inertia. As it travels down the exhaust pipe a patch of low pressure is created behind it. The inlet valve is opened before the exhaust valve closes and this low pressure assists in "sucking" in the next charge. A similar action is carried through to the inlet tract, so that this also becomes part of the pipe which contains lumps of moving air or gas. The complete system becomes the subject of TUNING.

The distance between the pulses of gas results in pressure waves at a frequency directly related to engine RPM. These waves are most certainly "sonic" and there sound is music to many ears! Flat four, V6, V8, all obviously have their own song. There are other aspects involved as will be appreciated, e.g. expansion of the gas as it cools.

It does not take much brain power to relate the associated factors involved, e.g. obstructions in the form of passages and valves; valve timing; inlet tract length; exhaust design; number of cylinders; engine speed; etc; etc. Modifications can be made in many areas to alter the fundamental characteristics of the engine, with both positive and negative outcomes. These basic fundamentals have not changed over time, as has been claimed.

I have not gone to the trouble of compiling this extra hopefully simple explanation, in order to impress, but rather to prevent some from becoming confused by that previously posted.

[TomsSVX]

Since there has been great discussion and confusion as to what the best profile would be, I am going to stick with what is tried and true. I know from personal experience that the profile used in my old car was the cause of a significant gain. N/A with a standard transmission AWHP is about 170-180. Mods such as the stage 2v5 ECU included. Now the owner of my old car decided not to replace the stage2 ECU and is using a SAFCII which is a fuel controller. With this said, he dynoed my car at 191AWHP which is the most powerful EG33 to be dynoed to date. Even a standalone in an EG33 converted RS powered out only 185. Now if he had reinstalled the stage 2 software in my old car and dynoed it I am confident that he would have pulled 200+. Ths being said, I will be sticking with my old cam profile for the intake cams alone. I know it works and thats all I need to know. Harvey dropped the ball on answering my last Q so I will stick to what I know with no more dependencies

Tom

[Chiketkd]

Originally Posted by TomsSVX

Since there has been great discussion and confusion as to what the best profile would be, I am going to stick with what is tried and true. I know from personal experience that the profile used in my old car was the cause of a significant gain. N/A with a standard transmission AWHP is about 170-180. Mods such as the stage 2v5 ECU included. Now the owner of my old car decided not to replace the stage2 ECU and is using a SAFCII which is a fuel controller. With this said, he dynoed my car at 191AWHP which is the most powerful EG33 to be dynoed to date. Even a standalone in an EG33 converted RS powered out only 185. Now if he had reinstalled the stage 2 software in my old car and dynoed it I am confident that he would have pulled 200+. Ths being said, I will be sticking with my old cam profile for the intake cams alone. I know it works and thats all I need to know. Harvey dropped the ball on answering my last Q so I will stick to what I know with no more dependencies

Tom

That cam profile is definitely tried and true. My former 4EAT SVX dyno'd at 165awhp before the cams, and Myxalplyx dyno'd it at 175awhp w/o engine management.

[TomsSVX]

I never realize that there was close to a 20 WHP difference with a standard and auto trans. although I am sure your engine was much stronger than my j-yard motor I had in it. With the stage 2 and other mods I will probobly dyno the 6mt after the new cam install. I may even crack a single bottled run if I did indeed work out the kinks with the system

Tom

[Chiketkd]

Originally Posted by TomsSVX

I never realize that there was close to a 20 WHP difference with a standard and auto trans. although I am sure your engine was much stronger than my j-yard motor I had in it. With the stage 2 and other mods I will probobly dyno the 6mt after the new cam install. I may even crack a single bottled run if I did indeed work out the kinks with the system

Tom

Correct. The auto has at least a 30% drivetrain loss (could be even higher), while the 5mt is closer to 25%. As you start piling on 'effective' mods, those drivetrain losses really start to take their toll.

[Trevor]

Originally Posted by TomsSVX

Since there has been great discussion and confusion as to what the best profile would be, I am going to stick with what is tried and true. I know from personal experience that the profile used in my old car was the cause of a significant gain. N/A with a standard transmission AWHP is about 170-180. Mods such as the stage 2v5 ECU included. Now the owner of my old car decided not to replace the stage2 ECU and is using a SAFCII which is a fuel controller. With this said, he dynoed my car at 191AWHP which is the most powerful EG33 to be dynoed to date. Even a standalone in an EG33 converted RS powered out only 185. Now if he had reinstalled the stage 2 software in my old car and dynoed it I am confident that he would have pulled 200+. Ths being said, I will be sticking with my old cam profile for the intake cams alone. I know it works and thats all I need to know. Harvey dropped the ball on answering my last Q so I will stick to what I know with no more dependencies

Tom

Tom, you are dead right in sticking to and basing things on that which you know. When making mods to a production engine, estimate as best you can, test your decided option, learn from the result and move on from there. In other words, as you well know, it is all pretty much educated hit and miss. You show that you are making wise decissions.

The absolute object is to have fun. Cheers, Trevor.

[Trevor]

Originally Posted by TomsSVX

I have been thinking about what we can do with our cams. This thread is for those of you who know more about the technical points about them.

As of now we are able to weld and grind our intake cams to 8mm of lift with 240 degrees of duration. Stockers are 7mm of lift with 236 degrees of duration. Now this gives us a nice noticable improvement in power without sacrificing any drivability on the street.

I, however am looking to do something a little more radical with my next set. Since Delta Cams has provided me with a good price on cams I don't want to go anywhere else, but they are limited to pre-set profiles. That being said, lets talk about what else we can do.

I did a little research and I found that the most vital parts of designing a camshaft is the overlap... Increase the overlap and you will increase your upper rpm power but lose down low and have a "rougher" idle. This is what I am looking to do but not so far that it cannot be driven normally. Now say we stick with the 240 degrees of duration, what if we were to offset the cam teeth a little? I mean each cam sprocket contains 50 teeth which means each tooth is worth 7.2 degrees.

Oh, almost forgot. The exhaust cam profile is 8mm of lift with 244 degrees of duration.

With this information, what configuration would be optimal for a person looking to increase their high end power on a stock block?

Thanks for your help and please limit comments an questions to ones that are well educated

Tom

Tom, it is apparant that you know exactly where you are going and where you have come from.

Overlap is the important ingrediant. By grinding only the back of a cam, as an economically viable mod., lift is increased but the important factor is the associated extension of the opening time. Good to see that you have built up your cams with hard welding

There is no point in increasing the lift beyond a point whereby the open area of the valve exceeds the port area. A high lift increases mechanical stresses in a big way and involves further problems relative to valve bounce. Calculate the port area - OA area less the obstruction of the valve stem. The open valve effective area - The overall side surface area of a cylinder comprising diameter as above and hight as per valve lift.

You are not, on a basis of time and cost, able to experiment to the extent necessary to obtain an absolutely proven outcome, but with applied common sense you can be VERY close. Look up as many valve timing figures as you can, particularly performance related. In the back of your mind store all the characteristics and requirements of the cars involved. Compare, think, make a decission and when it gives results, as it will, rejoice with satisfaction, knowing you did it your way.

Believe me, alleged high tech. advice will not do more for you !

[Trevor]

Tom,

[For the first time in the years of using this service, (Special thanks to Chris and his helpers) contact has been delayed, but no moans from this part of downunder. As a result this post may be out in respect of time frame.]

This in effect a PPS to my previous post, so that you should also read it in conjunction. I appreciate that you started with this thread in the hope of obtaining positive confirmation that you had made a correct decision regarding your cam mods. and therefore make further comments, which I assure you, are the whole truth and NOT BS.

A few minutes ago I decided to have a look at the manufacturers figures in print. My immediate reaction was - increase the inlet opening and make inlet and exhaust near equal, which is the classic arrangement. My second thoughts back this up. For the fun of it I have not checked back in the thread, but I have a sneaking suspicion that you altered only the inlet cams and figure of eight was mentioned.

The resulting timing is still very mild, but the large valve area has the effect of increasing relative overlap as you will be aware. If we do both happen to think alike, two idiots must make a plus !

[SVXRide]

Trevor,
I've been talking with Tom and others on the Network about the cams in our engines, and it seems like we've arrived at the following:

1. The "welded&ground" intakes giving us 240 deg and 8mm lift do increase mid and upper rpm performance at the expense of a little low end (really not an issue with MT or 4.11/4.44 AT)

2. Looking for an "improved" profile for our exhaust cams has been a futile effort to date

3. Using our stock exhaust cam profile for "welded&ground" intakes is still open to discussion (i.e. additional 4 degress and I believe the ramps might be different than the profile Delta Cams is using for the 240 deg/8mm mod)

Thoughts?

-Bill

[SVXRide]

Originally Posted by TomsSVX

Since there has been great discussion and confusion as to what the best profile would be, I am going to stick with what is tried and true. I know from personal experience that the profile used in my old car was the cause of a significant gain. N/A with a standard transmission AWHP is about 170-180. Mods such as the stage 2v5 ECU included. Now the owner of my old car decided not to replace the stage2 ECU and is using a SAFCII which is a fuel controller. With this said, he dynoed my car at 191AWHP which is the most powerful EG33 to be dynoed to date. Even a standalone in an EG33 converted RS powered out only 185. Now if he had reinstalled the stage 2 software in my old car and dynoed it I am confident that he would have pulled 200+. Ths being said, I will be sticking with my old cam profile for the intake cams alone. I know it works and thats all I need to know. Harvey dropped the ball on answering my last Q so I will stick to what I know with no more dependencies

Tom

Tom,
Did you take a close look at the dyno plot for your old car? The AFR looks weirdly "flat" - it looks like it stays around 13.5:1 throughout the pull (never goes below 12:1)?
-Bill
p.s. then again, it may be another piece of info indicating that the EG33 really doesn't like to go as rich as what normal "tuning knowledge" would otherwise have us believe....

[Trevor]

Originally Posted by SVXRide

Trevor,
I've been talking with Tom and others on the Network about the cams in our engines, and it seems like we've arrived at the following:

1. The "welded&ground" intakes giving us 240 deg and 8mm lift do increase mid and upper rpm performance at the expense of a little low end (really not an issue with MT or 4.11/4.44 AT)

2. Looking for an "improved" profile for our exhaust cams has been a futile effort to date

3. Using our stock exhaust cam profile for "welded&ground" intakes is still open to discussion (i.e. additional 4 degress and I believe the ramps might be different than the profile Delta Cams is using for the 240 deg/8mm mod)

Thoughts?

-Bill

Bill, some more thoughts to add to my previous brain children. More importantly, simply to mix with yours and your associates ideas.

Please advise the BTDC and ABDC figures so that I know where the inlet opening period sits in relation to TDC and I will set loose another storm.

Cam grinders can or can not be a good source of knowlege. Some are simply expert machinists. Others take a keen interest and sift results after getting feedback from customers. But at the risk of labouring a point, beware of the BS artist!

Best of luck with the project, Trevor *<)

[TomsSVX]

Sorry I haven't really been around the past couple days, had many things taking up my time and mostly work. I have a full 14hr day ahead of me but I have this week off. Trevor, there is a ton more info on the cams we selected in a thread Chiketkd had started. It was a quick how-to for a mild N/A build. He has all the specs for the cams in there. If I can find my data sheet from my last set I will post it. Sorry for the delay, just super busy

Tom

[TomsSVX]

Trevor, to keep you up to date, this is following info on what cams we have been using (Chike and Myself)

Originally Posted by Chiketkd

Stage 3:

The idea for upgrading the intake camshafts has been tossed around on this site for years. The specs I used were the brainchild of oab_au who based his theory off of the stock specs Wawazat measured a few years ago. Oab_au had helped his son modify his Z motor (which used similar internals to the EG33).

The stock specs are as follows:

Intake Cams: 7.0mm lift, 236 degrees duration
Exhaust Cams: 8.0mm lift, 244 degrees duration

I picked up a set of stock intake cams from TomsSVX around the end of summer and began exchanging PM's with Harvey...

Stock Cams


The ideal intake cam specs Harvey recommended for a 4EAT SVX are as follows:

8.0mm of lift, 240 degrees of duration

From here, I began speaking with several different camshaft grinders including Webcamshafts and Ram Performance. However, all roads led to www.deltacam.com in Tacoma, WA. Their sales guy Scott was very helpful and going back-n-forth with him and Harvey we settled on the following specs for the weld-n-grind on the intake cams (their machine wasn't set-up to do 240 degrees of duration):

8.0mm of lift, 247 degrees duration w/ the entire profile retarded by 7 degrees

The cost was $150.00 per cam excl/ shipping:

Modified Cams


SubaFreak and TomsSVX were very gracious to lend their assistance in the installation of these modifed cams, and on Saturday, November 5th I drove up to NJ to do the install.

We decided to pull my engine, even though it wasn't necessary, as it would give us extra working room on this install:





The valve covers were pulled, and while I replaced the seals, TomsSVX and SubaFreak installed the performance intake cams:



The Ride & Drive
As lift was increased by 1.0mm, there's more power throughout the rev band w/o a noticeable reduction in low-end power despite the slight increase in duration. My stall speed is still 2,500rpms and launches are still quick but w/o the excessive wheelspin and axle hop I experienced before (i.e. only slightly less torque down low).

As the rpms rise, the power comes on with a rush between 3,500-4,000rpms and from there it's a really quick blast to redline!

I can't say how much extra power these cams make as the stock MAF is maxed out between 240-250hp (per Mychailo's extensive testing with his wide-band and MAF voltage reader). I would make a conservative estimate of between 10-15hp, but to fully realize the performance potential of this upgrade the ECUTune Stage 2v5 w/ the Z32 MAF is a necessity!

-Chike

Tom

[Trevor]

As you I am sure appreciate, the thread is now so convoluted that I have had to more or less start from scratch in regard to my comments.

The stock specifications shown in the Subaru Manuals I have show :-

INTAKE - Opening 2* Before Top Dead Centre. Closing 54* After Bottom Dead Centre. Therefore duration, (not specified), = 236*)

EXHAUST - Opening 55* BBDC., Closing 9* ATDC. (Duration = 244*)

PATTERN in my language :- 54 - 2 - 9 - 55,

The overlap is therefore a very mild 11*

I have never seen valve timing expressed simply as an opening duration and can not see how this can indicate the true picture, A most important factor relates to where the timing sits in relation to piston travel expressed as TDC and BDC.

If the question had been originally been put to me, I would have said on a conservative basis, go for a mild say :- 55 - 9 - 9 - 55, as this requires altering only the inlet cams. This means an inlet duration of 244*. Harvey suggested 240*. which I would say would not have been worth the effort. Most important is that he does not specify a relationship with TDC.

It would appear that you have the inlet retarded by 7* which appears strange to me, although I agree that it is more usual to have more overlap on the exhaust side, particularly in respect of normal production engines. Possibly your idea also takes into account forced induction. Your advice in this regard could assist our discussion.

I gather from memory recorded back in the thread, that this 7* was achieved by shifting the camshaft gear engagement. If so it could be possible to revert to what I suggest by way of an experiment. Pleased that it is not me doing the hard yacker!!

My experience relates to more than one car I have altered for motor racing, but as I have pointed out before, your decisions have to be based on intuition. You are not able to experiment much, having cost in mind. I am simply putting forward my ideas for you to include within your thinking. In this connection, check my arithmetics.

Edit P.S. Taking into account the figures you have quoted, it would appear to me, that you are experimenting with what must be the most cost effective method of improving performance, relative to sporting requirements. Your efforts will I hope, be appreciated by others.

[TomsSVX]

So my initial thoughts about using our exhaust profiles may have been dead on. I was thinking of just using the same profile as the exhaust on the intakes. Leaving us with exactly what you are recommending. I will call Scott this week at Delta and make sure he still has the exhaust profile fom the cams Bill sent him. I will also see what kind of price we are looking at as it seemed every time I called, the price went up

Tom