Warpspeed

Strewth mate, what the bloody hell are you on about. You some sort of poofta wog foreigner or sumthin, goin on like that. Youse ought to be bloody shot. Flamin drongo. Have another beer cobba.

Yeah, isn't it amazing how may tools come on the forum and expect us all to feel sorry for them. Sounds to me like the copper sized you up pretty well danh. Score.... cops 1 danh 0

Yes, its the same guy. He has in the past been swamped by morons and people begging for compressor flow maps that Garrett will not make public. So he stays hidden these days. Don't blame him either. Hehehe.

MattSR, in reply to your question about compressor cover a/r. The cover is at least as important as the wheel trim in deciding the shape of the compressor flow map. All flow maps lean to the right, and the efficiency islands vary quite a bit in shape depending upon the wheel and housing combination. Small compressor cover a/r will give a flow map that is tall and narrow. The efficiency islands will be stretched out along the tilt of the map. This works really well at high boost with a largish turbo, where the flow line rises at a steep angle through the centre of the tilting flow map. Matching will be pretty critical though, and the wastegate will remain shut right up to almost redline. This sort of matching would be used where the exhaust turbine is very large and you want maximum top end power at relatively high boost levels. (drag racing). A larger a/r cover would produce a flow map that is not as tall, but much wider. The efficiency islands will be rounder, and there will be a much wider flow range between the surge line and the choke region. This works best where you run a small exhaust turbine and arrange for the wastegate to open at lowish engine RPM and hold boost constant up to redline. In this type of matching the flow line on the map will be horizontal, because boost is constant over a fairly wide engine RPM operating range. Also boost will probably be lower for this type of application (street car). I had a long discussion with a Garrett applications engineer (Geoff Lotterman) in the US on this topic, a few years ago. I have no idea, but the fact that HKS are supposed to be better matched for higher boost levels suggests they may be using smaller a/r covers, I don't know this for sure though. The Garrett GT turbos seem to have huge covers, and can be a bastard to fit in some installations. Does anyone know for sure about the comparative a/r of similar trim HKS and Garrett ? It might explain a few things. It may very well be, that a Garrett GT may actually be BETTER than an HKS for a low boost road car ? Wouldn't that be something ! I strongly suspect Garrett have optimised their turbos for mass produced OEM applications, and HKS for all out racing applications. Both are good, but one might be more suitable for YOUR application.

Can you just turn it upside down ? It might mean transferring the TPS onto the other side, and/or other slight modifications, but I have done this successfully myself in the past.

It sure does on a lot of cars. Try measuring the actual voltage across the fuel pump, do not be surprised if it is 11.5v or something on some cars. With the engine running at anything well above idle, there should be about 14.0 to 14.2 volts right at the battery. So you use the original fuel pump wire to operate a relay instead of the pump, and run a pretty big thick wire straight from the main fuse-box to the relay, and then to the pump. This is usually a lot easier than rewiring the original fuel pump circuit. If you can increase the voltage from 11.5v to 14v, that is nearly +22%, and the motor current will also increase 22% at the higher voltage. Pump power goes up about 49% in this example. The difference this can make to pressure and flow has to be seen to be believed. Replacing the stock pump with a monster aftermarket pump will usually increase the pump operating current, so check the voltage at the pump. You may not actually be getting all that extra pump performance you paid for.

Sydneykid is spot on with his comments about the higher pressure requirements of a turbo engine (as usual). But another thought comes to mind. If you leave the stock pump in the tank, and fit an external pump in series (Bosch or Walbro), then the pressure capability is going to be much higher than either pump by itself. So although a Walbro might start to droop in flow at high pressure, it might be well up to the job if mounted externally in addition to the existing pump. What I like to do, is run an airline via a pressure regulator from the workshop compressed air supply to the fuel pressure regulator on the fuel rail. You can then dial up say 20 psi "boost" and fool the fuel system into thinking the boost is actually there. You can then measure the return fuel flow at that "boost" and see how your fuel pump and lines are coping. You can also plot fuel flow versus "boost" and get a pretty good idea of how good the whole fuel system is handling the flow. If you have six 550cc injectors, I would like to see a comfortable margin above 6 x 550cc (3.3 L/min) of fuel flow at maximum boost pressure. This is not difficult to do, and well worth the trouble.

I have a small job, welding a couple of short pipe stubs onto an intercooler tank. No fabrication required, just a straight easy TIG weld job. Where, and about how much ?

The GTST or GTS-4 is obviously heavier, but the drive-line is extremely strong. Buy a Rex and you will destroy clutches and gearboxes faster than you would ever believe possible, if you drive it hard. The Skylines are indestructible, and take some serious mods without becoming unreliable. The GTS-4 gearbox used with the RB20 has different ratios, but is otherwise identical to a GTR box, and is just as strong. Same with the diffs.

Forget about the high intensity LEDs around the numberplate, I have tried it. If you use a night vision viewer you can see how things look at infrared easily. Your numberplate looks like it has Christmas tree lights around it. Quite pretty actually, but you can easily still read the numberplate. I do not understand how tilting the numberplate is going to help. I can easily see a numberplate that is angled 45 degrees away from my line of vision. It certainly does not disappear or become invisible. If I can see it, so can a RADAR or LIDAR.

HPC is going to be the best, money no object solution. Wrapping is not going to look as nice, but if neatly done should work just as well. Do not forget that heat shields are also very effective and low cost where you have very high temperature parts. These should be shiny aluminium or stainless, and reflect most of the infrared radiation back to the source.

Good idea, but heat wrap is made to withstand red hot exhaust temperatures, and your intercooler pipes will look horrible. Also the stuff is not exactly cheap. Go to Clarke Rubber and buy some sponge neoprene sheet, its the stuff wet-suits are made from. It is dull black, and does not look out of place in an engine compartment, and it comes in a wide range of thicknesses. It stretches a fair bit, and with a pair of scissors, some contact adhesive, and a bit of imagination you can do a first class job around those tricky bends. I bought a can of Quick Grip adhesive. Its the stuff you smear on both surfaces and allow to dry, and any showing afterward wipes off with a petrol soaked rag. I have done this a few times and have been completely happy with the results. This stuff is a really good thermal insulator, and its waterproof.

Yes, you usually get a standard printed sheet that gives recommended bore clearance in thou for each inch of bore diameter, and all sorts of other useful information. Can anyone quote figures for different brands of forged pistons ?

There is an interesting forged piston thread on another Forum here: http://www.eng-tips.com/gviewthread.cfm/le...id/71/qid/58034

Thanks for that Phantom.

Hey Sydneykid, sorry for straying off topic. What sort of clearances do modern forged pistons run ? I am really interested in this.

You are right, early complete vaporisation WILL remove heat from the intake charge, and lower induction temperatures. No argument there. Also lower charge temperatures mean more density, and this is extremely important for power production. So I agree. But reducing detonation is a completely different thing to producing power. Detonation is only due to the peak temperature and pressure reached during actual combustion. Provided a certain mass of water is totally turned to vapor (boiled) the specific heat will reduce the final combustion temperature, and combustion will remain controlled. So purely from detonation point of view it does not really matter where the water is introduced, or where along the chain of events it all finally boils off. During combustion it most certainly will all boil because the temperatures are so high.

Yes you are right. The other gasses and fuel do not just disappear, but the nitrogen working fluid is something that fascinated me when I first learned of it. It is also why nitrous oxide works so well, it is mostly nitrogen (N2O). I believe pure oxygen will increase combustion temperatures and can lead you up the dreaded detonation path, so be careful.

Oh, you can still have a lot of fun with cars, but as Clint Eastwood says "A man should know his limitations". I have built lots of motors myself, before and since that expensive little adventure. Yes it was a TC Cortina, nine inch diff, four wheel discs. It even had a Hone planetary two speed overdrive on the diff ! I still have that out in the shed as well. A lot can be done with mostly stock parts, and assembling it yourself, a bit of head work and some cams. The rest is all bolt on externals with a turbo. So it need not be horribly expensive. It is when you get a professional engine builder to start X raying this, shot peening that, special crankshafts and rods, custom pistons, big dollar head work. It all adds up and is probably a total waste of money in a street car. Over the last ten years my priorities have shifted. I now am a total tight arse with cars, and have become more interested in finance and investing. I have yet to reach my first million, but am almost there. That is why I do not have a Skyline yet ! I used to spend every cent I had on cars, but not these days.

What water does is raise the detonation threshold. To understand what this is, you need to understand detonation. What happens with detonation is that the trapped mixture is ignited by the spark and begins to burn in the area immediately around the plug. This burning causes the (mostly)nitrogen in the air to expand from the heat and increase the chamber pressure. Now the burning continues until all the mixture is burned and pressure and temperature reach a maximum, usually at about 20 degrees ATDC. The ignition timing is early enough to always get the maximum at around 20 degrees ATDC. What can happen though, is that the pressure and temperature in the chamber can get high enough to cause not burning but a spontaneous EXPLOSION. The whole lot detonates like a bomb creating a huge shock wave that breaks things. So it is temperature and pressure that causes detonation. So you must lower the temperature and pressure reached DURING ACTUAL COMBUSTION(or use a less detonation prone fuel). One way is to inject water. It does not have to be fully vaporised before it reaches the engine. Even a solid jet of water is going to flash into steam either during the compression stroke, or actual combustion. It is the high latent heat of water that lowers the peak combustion temperature and reduces detonation. Another interesting feature is that the steam expands along with the nitrogen in the air to act as the working fluid that pushes down the piston. So although peak temperatures are much reduced, the pressures are not, and you lose no power by adding water, in fact you gain a bit. A lot of people do not realise that it is the nitrogen in the air that does not burn which actually pushes the piston down. And steam works even better. The reason I suggested fuel injectors is because they can meter in precise small quantities into every cylinder, and the fine spray is going to assist vaporisation. Spraying water into the turbo inlet also works, but like fuel distribution, you have no way of knowing if that water is going to find its way into all cylinders in equal quantity. It will if it is fully vaporised, but it may not be.

Yes Joel, it was a 250 Ford motor de-stroked to 221. It had 7:1 Arias blower pistons, Crower rods, cross-flow head, and a T04 V trim turbo with E flow turbine and 1.0 a/r running 20 psi. The seven thou clearance was what Arias recommended for the bore size (at that time). A brand new block, ultrasonically tested, was bored and honed oversize especially to suit the pistons. This thing had billet steel bearing caps and a steel flywheel with Falcon GT twin plate clutch. The head was fully ported with oversize valves and roller rockers. It ran no head gasket, but had dykes gas filled sealing rings around the bores, and a smear of silicone seal around the water passages. Chrome molly studs were used for head and main caps. I still have the motor actually out in the shed. I could never sell it. It might sound pretty barbaric these days, but in the mid 70's it was a fairly radical motor. Three were built at the same time. One went into a racing hydroplane, one into a sports sedan, but this one was strictly for street. It cost me about twenty grand all up for the motor, when the car itself cost me only three grand brand new off the showroom floor. I had ring sealing problems, and also rapid valve train wear from the radical cam and massive double Crower valve springs. I learned a few things from it though. One was never to be so bloody stupid ever again. When I read about people doing radical things to GTR engines, I just sigh, and think yeah, one day you too will regret all the money wasted on youthful folly. But is was fun though.

Oh that is a nice flat torque curve, you obviously have the tuning spot on. Well done...........

Quite right. At high speed the water is going to be blown all over the engine. But if you are going a million miles per hour, and have a good airstream, you might not actually need the water. Or perhaps you could turn it off at high road speeds, or in the higher gears?

Just as a matter of interest, what piston bore clearances are you guys running ? With my Arias forgies the bores were finished oversize to give seven thou clearance, that was with a turbo Ford six cylinder motor that has a 94 mm bore. It lasted about 30,000 Km and had some serious ring sealing problems. I still have these pistons attached to Crower rods, but no digital camera here unfortunately.