Warpspeed

If only it was that easy. All the extra hardware and mods required, plus tuning is going to make that original 2K for a bare turbo look cheap.

Again you are probably right. But if its true, why have the Nissan engineers not lowered either the boost or compression ratio and run correct mixtures ? I suspect that a properly tuned stock engine running on the higher octane fuel available in Japan does not run rich at all. Here in Oz, and after you have modified your engine, the EFI computer detects that something is not quite right, and runs rich. So fair enough, you lean it off, and it goes better. But I also would like to bet that the Australian delivered Skylines (R31, and R32 GTR) do not run rich in standard tune. Anyone know ?

You could be right, but as far as I know correctly functioning EFI systems are never set so rich that you lose large amounts of power. What would be the point in that ? Sometimes if a system detects a fault it may deliberately go super rich to save the engine, for instance a runaway overboost condition, or massive overheating. If a system is hugely over fueled, the extra fuel takes up space that the oxygen would normally occupy, and power decreases. There are really two CORRECT air fuel ratios. Best economy is when all the fuel molecules are burned, every last one of them. There is always some excess oxygen in the exhaust at best economy setting. Best power setting is where all the available oxygen is consumed. There will always be some slight unburned fuel in the exhaust at the best power setting. There is never any economy gain from going excessively weak, or power gain from going excessively rich. That is my understanding of it anyway. If all Skylines are set deliberately rich from the factory to use more fuel and lose power, you have to ask yourself why would they do that ?

If I had a chice between a brand new Garrett, and an old HKS that was probably rooted, and they were the same price ? Silly question really.

The turbo was invented by a Swiss guy called Alfred Buchi around 1910. If you do not believe this, do a Google search and see. The turbo has been around almost as long as the internal combustion engine, it is nothing new. Towards the end of the first world war, a few of the wood and canvas biplanes with ancient radial engines were turbocharged. The reason modern engines have DOHC four valve heads is that this allows very good power while also maintaining economy and emissions. The thinking behind this is that you can have good top end airflow (power) and also use very restrictive valve timing (emissions and economy) together. With four very small light valves, and direct cam actuation the valves can open and close much faster. The valve springs can be lighter, and the valve lift does not need to be so great. All of this is of great benefit to a racing engine, but it also means you can run very restricted valve timing with little or no overlap, and still get good top end airflow. Power is the result of how much air (oxygen) can flow through the engine, then adding enough fuel to burn the available air. There are four ways to get a lot of oxygen into the engine. You can just build a big engine. Your big engine will be powerful because it is big. Or you can make a small engine turn at high speed, and also be efficient at that higher speed. You can supercharge the engine so it works in denser air. Or you can add oxygen directly by combining nitromethane or nitrous oxide to the fuel as an oxygen booster. The power is limited by available oxygen to burn, increasing the fuel further beyond this will not increase power. I doubt if adjusting air fuel ratios are going to improve power, unless the original air fuel setting is very lean. The majic carburettor, or fuel injection chip that doubles your power is BS. More power needs more air, and extra fuel to burn that extra available oxygen. It is as simple as that. The old two valve heads can be made to breathe reasonably well, but you need a very lumpy cam to do it.

Its no good complaining how much the fines cost, or how many points the bastards have given you. It is a bit like spending big dollars on gambling or booze, then complaining how much it is all costing you. If you drive sensibly, and within the law, the cops will just ignore you, just like they ignore 98% of motorists. If you want a racing car, that looks and sounds like a racing car, and you drive it like a racing car on the street, of course the cops are going to pick you out. Simple really.

How about selling the RB25DET, and replacing it with a stock RB26DETT. That would give you a far better basis to begin from.

Yeah, Garret are in the mass produced turbocharger business as a multinational corporation. They do not want to know anything about hot rodding, or do it yourself car modification out in the back shed. What Garrett do is supply very large numbers of turbos to the car and truck manufacturers for their own new vehicle assembly plants. So every turbo they make is for a specific engine of some other manufacturer. So when you buy a GT17, or a GT25 Garrett turbo, it is almost certainly a standard turbo off a Saab, or some Volvo, or Ford product, or who knows what else? Now these standard turbos that are available come with certain combinations of wheel trims and housings, and will probably work fine on your engine, just as they are. But they might also just as easily be off some strange marine diesel application that might work very well, or it might not. So HKS have set themselves up to order vast numbers of Garrett turbos to the HKS specification, whatever that is. So HKS turbos are just really Garrett turbos with the HKS name. So as has already been said, the local turbo shops know what works, and what is required, and can either order in the right Garrett GT turbo, or modify one with Garrett spare parts at a fraction of the cost of a genuine HKS. There is no reason why you could not get a genuine HKS turbo, identify the parts, and modify the closest Garret to be EXACTLY the same.

Bloody hell. You guys are real funny. If the speed limit is 50, and you are going over the limit you deserve what you get. Simple as that You took a chance, and got done. Bad luck. If you were going 45, in a 50 zone, and the copper books you, then you DO have a reason to complain.

Andrew, get onto Google, and find Ray Hall Turbocharging. He has a good web site, with a lot of information, as well as some flow maps you can look at. Also there is a very good book Maximum Boost by Corky Bell, available for around $100, but well worth it.

Garrett spec their turbos at 1 Bar pressure, (pressure ratio = 2) at the 60% efficiency line on the flowmap (which they will not give you). Now flowmaps all tilt to the right to some extent, but the efficiency curves can vary quite a fair bit in shape from wheel trim to wheel trim. Also the compressor housing a/r will effect the flowmap shape as well. Small a/r makes the flowmap tall and skinny, large compressor a/r makes the flow map shorter and fatter. So if Turbo X flows 300BHP at 1 bar boost, it MIGHT flow 340BHP at 2 bar boost, or it might not. There is the opinion around that a Garret turbo is total crap, and an HKS turbo fitted with identical Garret wheels is somehow absolute majic. Yeah maybe. Garret supply HKS with all the rotating assemblies, HKS just make the housings with the HKS name on the outside, and charge twice as much.

If you do that, there could be an up to 236.7% fuel saving. Fuel will flow back from the engine and overflow the fuel tank. This could pose an extreme fire and explosion hazard. Warpspeed takes no responsibility if you blow yourself up.

If you fit a foxtail to your radio antenna, and a pair of fluffy dice to your rear view mirror, and fit the award winning Warpspeed Exhaust Tip, it will reduce fuel consumption by up to 23.67%. This has been proven under strict laboratary conditions, carried out by the nunns at the sacred octane convent. However, you never see these things around these days, because the CIA and the oil companies have a covert plot to eliminate all foxtails and fluffy dice. There have been numerous attempts to kidnap Warpspeed to learn the scientific secrets of the exclusive and world renowned Warpspeed Exhaust Tip. If you PM me, I can supply you with a genuine immitation plastic foxtail, fluffy dice, and included FREE the world acclaimed Warpspeed Exhaust Tip. Just include your credit card number, and I can supply these for $899.00, but hurry stocks are fast running out.

Rb25 and RB26 blocks are machined exactly the same. RB26 crank, rods, and pistons drop straight into an RB25 block. This is a really good mod, if you can find the bits.

Well said sciby. I went to overclockers thinking it was another good car nutter site, but found it was mainly computer oriented. Nothing wrong with that at all, but not what I am interested in looking at in my leisure time these days. By the way, I am a retired electronics hardware engineer. My speciality is switchmode power supply and magnetics design. I have over twenty years of R&D experience, developing new commercial products for industry. So, when I pretended to be terribly distressed by suddenly being surrounded by electronics and computer people, it was totally tongue in cheek I assure you. With regard to the individual you named. On this and other Forums, we are each judged by what we say, and the views we hold, also by courtesy, respect, and manners. If a person behaves like an offensive idiot all the time, that trait becomes his persona. And it soon becomes his permanent identity to other Forum members. Cheers.........

You mean INASNT is an engine ear ? Been to oonaversity ? All those late nights in the adult bookshop must have paid off.

I have quite a few colleagues in the electronics and software games, that are badly afflicted with car disease. By some of the replies on this forum, there would seem to be a lot of computer and electronics professionals that come here to smoke rubber. Yeah man, way to go.

Ah yes.... thats better. Before I somehow landed in the computer section. I found myself totally surrounded by computer geeks and nerds, trapped and unable to escape. It was like some horrible nightmare.

So where is the car section ? Overclockers Australia Forum seems to be about how to clock microprocessors faster, and other computer related hardware and software topics. I looked through a whole lot of threads and that is all that seems to be there.

NO

Are you sure its only two degrees, hardly seems worthwhile. Most other VVT systems that I know of shift things 15 to 20 crankshaft degrees.

For the first time ever...... I have to agree with INASNT......

Yeah, I have noticed the same thing. If the boost is low, and there is no risk of detonation, and you only give it occasional brief squirts, it will be a lot more responsive with the turbo outlet going straight into the throttle body. But if it heat soaks, or you really give it heaps, or you tow trailers up hills, a decent intercooler is an absolute must.

The way I once had it explained to me by a Garrett engineer, many years ago, and it goes something like this: The compressor wheel accelerates the air to high velocity, where the high speed air has high kinetic energy but little actual pressure. The purpose of the scroll is to smoothly decelerate the air, where the kinetic energy turns into static pressure and increased temperature. The air is braked (slowed down). so the cross sectional area of the scroll smoothly increases towards the outlet. The ideal situation is to continue the expansion after the scroll until the desired velocity is achieved to feed the engine plenum, or intcooler. So the turbo exit pipe can be fairly small maybe two inch to match the turbo outlet. This should then ideally increase in diameter to match the cross sectional area of the intercooler. Usually this is not practical for space reasons. The best shape for accelerating or decelerating air is exponential, or shaped like a trumpet. Where the initial increase is gradual, and it then flares out at an ever increasing rate. In fact many well designed intercooler end tanks look exactly like a trumpet flare, but with a rectangular outlet to match the core shape. The whole turbo to intercooler pipe should ideally look like a continuation of this, where the deceleration rate of the air is constant between the turbo and intercooler core. This will give minimum pressure drop, and minimum pipe volume (in theory at least). At the intercooler outlet you want to again match the core flow area to the throttle body size. This might require another exponential pipe of decreasing area. Think in terms of velocity and flow area, and treat the air very gently (happy air). What you do not want is rapid changes in air velocity through the system, (angry air) caused by step changes in pipe size or sudden sharp turns. Again probably imposible to achieve in practice, but worth a try if you have the space and inclination to do it.

Interesting discussion. I have always wondered about the pressure drop across the intake pipework, compared to the pressure drop across the exhaust. Ignoring the slight extra mass due to the addition of fuel, the mass flow should very nearly be the same. But the exhaust temperature will be a lot higher though. Does a foot of intake pipe have the same pressure drop as a foot of exhaust pipe, if the diameters are the same ? The same number of air molecules are going down the pipe per second. The same thing must happen in an intercooler, even though the air shrinks as it gets cooler, the same number of air molecules must come out that go in. So the air will slow down, but surely the denser air will have more drag. So maybe it ballances out, high velocity thin hot air will have the same drag (and pressure drop) as low velocity cool dense air ? ? ?