Warpspeed

I can see where Sydneykid is coming from on this, but It really would be nice to know where both cams were in the first test, and where they were in the second test. Jay is right about cam belt tension as well. If you really heave down on the tensioner you can easily move both cams a lot more than four degrees. It really was a pointless exercise the way it was done. And no reflection on the workshop involved either. If the customers says dyno my car, than fit that pulley at -4 and dyno it again, that is exactly what was done. Now the result is total confusion. At the very least the locations of both cams should have been measured after the second test so that they could be returned to that figure later on. Was the ignition timing checked before the first run? probably not. Its a bit like stuffing around with ignition timing on the dyno and after many runs saying yep, we picked up some power by advancing it a bit. Later the timing belt has to be replaced, and it is impossible to return the engine to the "good " ignition timing figure because nobody thought to record exactly where it was. Its really no good saying that it does not matter, every time you adjust the timing belt tension it needs ten dyno runs to get it back to being right, because THAT is the only way to know for sure. Well, yes, and no. I would rather use a timing light, and every time I do an oil change, just have a quick look to see it has not moved from where I know is right. As far as the ripples in the power curve go, all sorts of tuning factors such as fuel and spark mapping come into it besides small changes in valve timing, and none of those were touched. The results while unusual, do not surprise me in the least. And yes the factory have changed the valve timing figures quite a bit for different RB engines and different model years. The cams themselves always have the bump exactly at the lobe centre of the first lobe. That is how they are ground on the cam grinding machine. So the difference in factory lobe centre timing is done with the pulleys. So a set of aftermarket pulleys that will fit any RB engine and are set to zero, might do quite different things to different model years of RB20, RB25, RB26 and so on. There is a lot more to it than just fitting a brightly coloured cam pulley and setting it to four degrees retarded, and expecting to pick up 15Kw every time. Time and time again I hear, Yeah and fitting those pulleys will give me an extra 15 to 20Kw, and also I am gunna get a...........

Jeeeeeez, not another one. Grow up, and just pay the damned thing.

Do you mean roofing tape ? It is shiny and comes in a roll and is backed with sticky black mastic. If thats what you mean any good builders hardware shop should have miles of the stuff.

You say that the cam with respect to the crank is not relevant ? Well then what is the point of retarding it then ? Of course it is relevant. The whole purpose of the cam is to open and close the valves at the right times. There are a whole lot of things that can shift the cam timing, especially stretch in the timing belt.

If you have absolutely no idea where each cam is with respect to the crank, how do you know moving it a bit in one direction is ALWAYS going to give a certain result. It seems to me, you need to know where you are, and where you should be, and shift it by as much as you need to get there.

Do you know what the actual exhaust valve opening and closing points were before, and after the four degree change ?

Sydneykid is just expressing what total pipe volumes give good response at various power levels. It is a very useful rule of thumb figure to know. It is just one of many factors to consider.

Cson, funnily enough I had a GTR core up on my flow bench over the weekend. What I measured was 22" water drop at 256CFM. That is about 0.785 Psi at 128Kw (roughly). Pressure drop increases with the square of power and flow, so expect maybe 3.14 psi at 256Kw. I really like Sydneykids approach to pipe volumes as well. The GTR core has rather large end tank volumes, but they are very nice looking end tanks from the aspect of even flow through the cooler tubes. Some of the aftermarket end tanks look rather primitive in comparison.

Factory plenums work fine at factory power levels. Most already have humps, bumps, ridges, and all sorts of strange internal shapes to give good air distribution. Trouble begins when you start trying to force twice or three times as much air through a stock plenum. The air velocities become extremely high, and you are going to get uneven air distribution. It is a bit unfair to say a stock part is crap because it starts to show some problems at extreme operating conditions for which it was never designed. Most people have no idea how high the air velocities actually get in a plenum. Try sticking your head out of a jet aircraft at several hundred Kmh, to get a feel for what high velocity air can do. Expecting air at those sorts of speed to go around narrow right angle turns is asking rather a lot.

It is interesting, forging and casting are manufacturing processes, and have absolutely nothing to do with what alloy they are made from. There are various grades of aluminium used in pistons, the main difference being the silicon content. Low silicon content means soft, expands more with heat, and they deform before they break. They will take a lot of punishment, but require more running clearance. High silicon is a harder material, and expands less, always used in cast stock pistons because you can run very tight clearances. Only problem is they are brittle and can snap ring lands at the first sign of serious detonation. Forged pistons are sometimes available in alternative material. The big clue is the recommended running clearance. Another clue is the piston weight. Do your research and know what you are buying.

Getting in is dead easy. A brick, as has already been said, or a BIG screwdriver into the lock barrel. Then a big twist with massive hairy tattooed arms, will easily spring open the lock, and completely stuff your door skin as well. Forget about keeping anyone out, it is just not possible. But there are lots of sneaky ways to prevent anyone from starting the engine, especially if the very loud alarm is going absolutely nuts. A tracking device is a good idea as well. Whatever you do, don't put those stupid stickers on the window that says "protected by thief stopper alarm model XYZ" You need layered protection. A big ugly steering wheel lock that can be seen, a good alarm/immobiliser, PLUS something extra, like a secret fuel pump or airflow meter isolation switch that you have fitted yourself, and a tracker if possible. There are lots of ways to hide a switch. One way is to use a factory switch on the dash that is already there right under the thief's nose. Another way is a magnetic reed switch glued behind a piece of plastic somewhere. Only YOU know EXACTLY where to stick the magnet to operate the completely hidden from view switch. Do not try hiding the switch under the seat or dashboard, the thief will feel around under there and find it in two seconds. I have had one car stolen from my driveway. Never again. In the old west, they used to hang horse thieves. Bloody good idea.

This is always a very good thing to do with any major pump upgrade. Power for the stock pump will come via the ignition switch, and at least one relay, and other assorted crap. These circuits have other loads as well as just the pump, so the voltage drop at the back of the car might be a lot more than you expect. Rewiring the whole lot is not a practical option. Sydneykid has the right idea (as always !). Use the original pump power wire to energise a pump power relay located at the back near the pump. Then run a really big fat cable right back to the main fuse-box. The variable pump speed feature will then not work, and you might end up with a noisy pump, but perhaps not if you take special care in mounting it. But even if you do nothing else, check the voltage right at the pump, it makes a vast difference to pump performance. Another thing you can do that might not appeal to everyone, is to fit a second pump in series with the stock pump, and leave the stock pump as it is. The second pump relieves the in tank pump of just about all back-pressure, and it will then flow far more, getting twice the flow this way is not unexpected. The second pump can be in the engine compartment, and hang by its rubber hoses, so there will be no extra noise. Also there are more volts at this end of the car if you use a pump relay as described above. You can even see and get to the damned thing as well. I am not suggesting this is any better, just different. It certainly works, is easier to do, and it is something else to think about.

Yes I agree, the cams themselves are pretty precise, and probably so are the gears and crank key. The problem is only with the belt. If the belt is slightly longer on the tight side because it has stretched, and you take up the slack with the adjuster, then both cam pulleys will have rotated very slightly anticlockwise with respect to the crank. As far as the timing marks go, you can only really fit the belt one whole tooth out, and the error is pretty obvious. But what if it is just a fraction of a tooth out ? The timing marks will still look o/k. Would you actually notice 2mm ? Not sure, but I think the cam pulleys have 48 teeth. that is 720/48= 15 degrees per tooth. 2mm of belt stretch (with an 8mm pitch belt) is one quarter tooth, or 3.75 degrees. 2mm belt stretch is not a lot between crank and exhaust cam over almost half the whole belt length, on a high mileage belt. Sure, the belt will be a bit loose, but tightening it back up could shift both cams by nearly 4 degrees. If you really heave on the adjuster, you can actually see the damned things move ! I kid you not. I am probably being a bit of an old woman about this, but people here are going to a fair bit of trouble and expense to do the 4 degree exhaust cam tweak, expecting to pick up measurable power. If the cams are maybe four (?) degrees out to begin with, the results may not always be quite as expected.

cannot really add much to what has already been said, but......... The easy way to turn the engine over to exact TDC, or anywhere else, is to put it into fifth gear and roll the whole car backwards or forwards. Slop in the drivetrain allows you to bounce the engine. Try it, you will see what I mean. When it's there, put on the handbrake. Easy. If you have an auto, bad luck. Another thing, fair enough you can retard it four degrees, but how do you know that the starting position was correct ? Also belt tension and belt stretch just by itself can shift it nearly that far. Think about it, if the belt has stretched, and you tension in the belt a bit on the slack side, both cams retard by however much the belt has stretched. only a couple of mm is actually a fair way. One whole turn being 720 degrees. To do it properly you need a dial indicator and degree wheel, and find out exactly where each cam is, and where it should be. It's a lot of work, and a pain in the arse, but its the only way to know for sure.

My figures are based on injector flow at that power for correct air fuel ratio, with zero fuel returned to the tank absolutely flat out. This might not be a good idea, but it is the theoretical absolute maximum limit for the whole fuel system and pump. A fuel pump supplier might not feel entirely comfortable with this though, and specify the pump at a power level that allows 10% fuel return or some safe margin as a design centre figure. These days they could get sued and be liable, if a particular pump falls a wee bit short of any published specification. So there is going to be a gap between a safe design figure, and absolute possible maximum.

Sure, there is no substitute for doing it for real on a dyno. But if you know your injector sizes and pump flow are o/k before you put it on the rollers, it is one less thing to worry about on the day. It is pretty easy to test all this at home, and fix the fuel system in your own (free) time.

Your best bet is to actually measure fuel pump flow in the car. It takes into account ALL the factors. Things like voltage at the pump, pressure drop across fuel lines and filter, and so on. Do the test and you will know for sure what you actually have. Disconnect the fuel return line after the regulator on the fuel rail, and extend the line into a clean plastic bucket or something similar. Remove the rubber hose between the top of the fuel pressure regulator and the plenum, and feed in some compressed air at whatever boost pressure you plan to run into the top of the regulator. If you have a compressed air supply airline and a spray painting regulator you are set. If you do not, you might be able to do something really clever with the spare tyre and a bit of hose, and a pressure gauge (maybe?). Anyway, the idea is to fool the regulator on the fuel rail into thinking there is actually full boost pressure in the plenum. Start the engine and run at a fast idle so the alternator light goes out. The fuel pump will have a higher voltage than with the engine not running. Using a graduated cheapy plastic hardware shop measuring jug, measure the fuel flow from the return line with a stopwatch. Convert this to cc's per minute. Divide cc's per minute by 5.6 to get horsepower. So, two litres/minute, is 2000/5.6 = 357 BHP for example The fuel pump will be working at its normal working voltage, against a back pressure of around 38psi + boost pressure. You can see how good your fuel pump actually is, not what you think it might be. It is also easy to check on how much improvement an upgrade actually gives you as well.

Yeah that says it all. The GTiR is a light weight crude rough ugly little road rocket, great fun. The GTR is a far better more solid and sophisticated road car in a completely different class. If you are 20 get the GTiR. If you are closer to 35 the GTR probably has far more appeal.

Exactly right. Another alternative is to rebuild your existing 4WD RB25DE block with the RB25DET pistons, or better still RB26 pistons, and add all the external bolt on turbo bits. There will be a cost saving, the motor will be fresh, and you get to keep the same engine number.

The really rich anywhere can do pretty much as they wish. Not a lot of people over there can afford to buy or run any sort of car. Anyone here in Australia can just go out and order a brand new Lamborghini Diabolo from the local dealer, easy. There are no rules laws, or government regulations or red tape prohibiting you from doing it. No bribes to pay to officials either. Australia is a wonderful lucky country, everyone and anyone can own a fully imported brand new Lamborghini anytime they want.

This is actually quite an amusing thread. "I want a sequential shift coz its quick" don't want to use the clutch either. I want to be able to change gears really fast so I can drag race. Why not fit an automatic transmission then ? Autos are for wankers that cannot drive properly. But I am prepared to spend really BIG dollars to have a manual box that shifts like an auto. Hehehe, its a strange world isn't it.

Yeah, the car has to completely clear a 100mm high block when it is rolled over it without the driver. I have seen them use a 100mm high L shaped piece of metal. If it falls over, when the car is rolled over it, you fail. Its a good test because there can be no argument about 99mm versus 101mm, it either falls over or it does not.

Yeah, the car must be able to be rolled over the top of a 100mm high block anywhere over the full width of the car. I have seen them use an L shaped piece of metal to test this. Nothing must touch, if the metal L falls over, you fail. so you need at least 101+ mm clearance everywhere. I know this is right in Vic, and probably so everywhere else these days.

Put a twin cam head on it.

Strewth mate, what the bloody hell you goin on about. You some sort of poofta wog foreigner or sumthin. Youse ougt to be bloody shot, sayin stuff like that.