Z_FromDownUnder

My dad once had a car which had a unique theft prevention system, when the key is put in the ignition, you have to touch a special screw in the dash so a current runs through your body into the key to start it. i fairly shore it was a custom job but something like that would help keep your prised car safe;-)

I've been wanting to get this off my chest for awhile now. Basically, the art of creating a High Revving NA engine is simply put down to a 'race' spec camshaft and nothing else is though of, although there are many factors that contribute to how high your engine will REV. To start with a good quality camshaft will provide the most noticeable increase in possible REV limit. It will allow for more air to enter and allow for exhaust to leave without constriction. This will be the most effective step towards a higher revving engine because it will allow for clean and efficient explosion in the cylinders. Without a better camshaft, the amount of air entering the cylinder will be greatly restricted due to severely shortened time the valve is open for at higher revs. E.G. At 3000rpm the Engine's crankshaft spins 50 time a second or once every 0.02 seconds if the camshaft allows for 20 degrees of inlet valve opening then 20/360 (20 degrees of total 360 revolution) x 0.02 seconds = 0.0011111... seconds the valve will be open (not that long even at relatively low RPM). At the target 8000rpm+ the time the valve will be open for is down to a tiny 0.0004166 seconds with is certain camshaft This shows the extreme decrease in time the gases have to more a high RPM so EVERY DEGREE COUNTS at High RPM. Often these extra degrees that after market camshafts give you will overlap the intake and exhaust valves which is necessary at high RPM but will kill engine efficiency at low RPM, which is why you never chose a 'Race' camshaft for street. The Camshaft is sometimes called the brain of the engine, but if you are looking for high Revs then the brains body needs upgrading. This means redoing the Valvetrain this is because the sort of wear that is experienced at high RPM is a lot higher than that the stock components where spec'd for. There are many things that can be done to the valvetrain for it to work efficiently, but the first thing that should be addressed is those springs, quite a few camshaft manufacturers require a complete replacement of stock springs when the shaft is installed to keep warranty. With new springs, the tendency for the valves to float open will be nullified. Port polishing will reduce restriction posed by rough surface allowing for greater flow. If possible the use of lighter components in the valvetrain will be of benefit as well. So now that the revs have begone to rise, whats next, well unfortunately from now on redesigning is the key word to higher RPM. Don't get too scared yet, this step is probably the least demanding of the redesign stage, it evolves changing the cylinder dimensions, most people will tell you that a 'square' design is best for a revving engine, but this is false. Rather, it is the most efficient because it provides good torque down low (thanks to a high stroke) and good power up top (thanks to Bore), but we are looking for power up top only, the torque down low will only be killed off by inefficient burning thanks to that nice new camshaft (if you when't to the extreme with the camshaft the your idle could just engulf that power with 'race' idles above 1000 rpm!!!). We want the power up top, so your first move should be to overbore (most people would already have done this before this stage), this should provide a nice displacement increase as well. But, and theres a big but, that stroke it becoming a bit of a pain at these RPM, E.G. if you add 1mm to stroke at 8000rpm this equals: 1mm per stroke so 1mm x 8000rpm = 8000mm or 8m of extra travel per cylinder or 48m per minuet in total And you have to remember that for every mm of travel, energy is lost rubbing against the walls of the block So the answer is simple, don't increase or decrease or destroke your engine, but don't go crazy, there will be a stage where the decrease in displacement of cylinder will outweigh the power gains of Higher RPM producing less power. Whilst we are messing with the internals, a custom set of pistons, rings, conrods and crankshaft (if destroking or for extra safety). Conrods are a must with high rpm as they can rip them selfs apart from inertia forces taking down your block, pistons, crankshaft and basically all your work for the last how long. You should get all your parts custom made with reduced mass in mind but never compromise strength. With reduced mass, inertia forces should decrease, allowing for overall safer RPM's. Now this is the big part of redesigning. We are going to take on the Valvetrain again but this time with maximum RPM in mind. Design ideas best for High RPM are as follows A lobe per Valve Camshaft- This nullifies certain rocker arm arrangements, for overall a stronger setup. This involves changing the valve setup to suit. Creating a five valves per cylinder set up- this involves a great deal of redesigning and needs to be started from scratch for best results, this should be used in conjunction with a lobe per valve arrangement Double Overhead Cam- Necessary as with the setups above, you cannot fit 30 lobes on a single camshaft Crank/Camshaft fired Ignition- involves setting the ignition timing to be physically done by a separet lobe on camsaft for very precise timing. After all this (and all that money) you should have a race engine capable of 10,000RPM+ and a truly unique engine:) Have Fun

Thanks mate for the help

Can anyone tell me what this wing is? http://forums.hybridz.org/showthread.php?t=121877 the wing for test 21-23 scroll down for images. Any help would be appreciated. Thanks.

Thanks MAG58 and everyone else for the info i have to say though that the DOHC thing will come second to the redesign of the exhaust ports to suit a RB26TT header so that i whould now have twin turbo (and yes this would be a long/expensive/difficult way to get twin turbo but if you don't take the harder options, what sort of journey it that?) anyway still wondering what the dimension differences between the two head would be?

yes i agree it would be easier and cheaper (maybe) to just stick a RB25 in there. But thats not what i'd want in a Z, its been done before, if this was ever done then there is a certain satisfaction to having built a one of a kind car. but in saying that anyone can take my idea from here and put it into work, that whould also make me happy.

Ok, so i've been thinking about the l28 head(s) and what options there are. i think i've come up with a plan to develop my own head, it will be based on the head of a RB25-26, i want to base it on this because it has DOHC and there are readily available headers suitable for twin-turbo. so to anyone out there who knows the similarities of the l28/RB25 heads and possible problems with this plan please chime in. also this head will be completely built at a custom head shop so everything can be changed eg. valve size. Just thinking about it, im guessing the RB head will be shorter than the L28 because of a smaller block (i dont actually know its smaller just a guess because of smaller displacement.) If this was to go ahead (in the far future) it would be a damn the expense exercise.