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#16
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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.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 05-11-2006 at 05:36 AM. |
#17
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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 |
#18
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"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#19
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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 |
#20
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__________________
"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#21
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The absolute object is to have fun. Cheers, Trevor.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#22
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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 !
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#23
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Tom,
[For the first time in the years of using this service, (Special thanks to Chris and his helpers) contact has been delayed, but no moans from this part of downunder. As a result this post may be out in respect of time frame.] This in effect a PPS to my previous post, so that you should also read it in conjunction. I appreciate that you started with this thread in the hope of obtaining positive confirmation that you had made a correct decision regarding your cam mods. and therefore make further comments, which I assure you, are the whole truth and NOT BS. A few minutes ago I decided to have a look at the manufacturers figures in print. My immediate reaction was - increase the inlet opening and make inlet and exhaust near equal, which is the classic arrangement. My second thoughts back this up. For the fun of it I have not checked back in the thread, but I have a sneaking suspicion that you altered only the inlet cams and figure of eight was mentioned. The resulting timing is still very mild, but the large valve area has the effect of increasing relative overlap as you will be aware. If we do both happen to think alike, two idiots must make a plus !
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#24
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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
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#25
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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....
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker Last edited by SVXRide; 05-13-2006 at 05:00 AM. |
#26
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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 *<)
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#27
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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 |
#28
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Trevor, to keep you up to date, this is following info on what cams we have been using (Chike and Myself)
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#29
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Valve Timing
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.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 05-14-2006 at 07:30 PM. |
#30
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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 |
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