Warpspeed

That picture is a fake................... Some clown used photoshop or something similar, it cannot possibly work the way it is. What stops the supercharger from blowing air back out through the turbos ? The pipe from the supercharger meets the TWO turbo discharge pipes at a right angle. Why would they do that ? how are the pipes joined (just out of view)? The supercharger rotates backwards. If the engine turns clockwise as viewed from the front, the supercharger would suck not blow. It is mounted upside down, the top rotor should be driven if it is supposed to work. The drive belt is the standard airconditioner compressor drive belt. It would shred in two seconds if it had to drive a real supercharger. The photoshop clown has just replaced the aircon compressor with a picture of a supercharger. This picture has been all over the web, and has sucked in lots of people. Clever eh ! Twincharging is great, I have done it myself, but that picture is still a fake.

Turbo = cheap and easy, lots of compromises though. Supercharging = more difficult and expensive (few kits around) if done properly far better than a turbo though. Now it is said you can get more power with a turbo, and it is probably true if you want to win horsepower heroes. But to get that power you will have minimal power band and bulk lag. So you want a bit more streetable power, yes, but you still have to agonise over which turbine housing you want, the one with the big rush at the top end, or the other one with less lag. Like I said, too many compromises. Engineering yourself a good positive displacement supercharger setup is a lot of work, but you get it all. There is also the myth about the power required to drive the supercharger, and turbos work with free energy. Not true. The back pressure in the exhaust turbine will rob you of just as much power, even more if the turbo is a bad match. When you put on the big a/r exhaust housing to make bulk power, it is the reduction in exhaust back pressure that gives you back the power that was always there in the first place. So turbos do not work on free energy. If its properly set up a supercharger will kill a turbo. But some people expect that fitting a three hundred dollar blower is going to make more power than a good turbo. It will not. A three hundred dollar turbo is not going to get you very far either.

FMIC = front mounted intercooler EBC = electronic boost controller

Yes, Ford Laser 1.6 plugs fit perfectly, I know this for certain. Mazda 323 plugs would be identical. Should be very easy to get as well.

Naaaaaaaaa. The cops have it all wrong. From where they were, they could not possibly have seen the dog that ran out into the road right in front of you. You slammed on the brakes, ................right ?

I bought a set about a year ago for $125. These were flow checked and they were also a FLOW MATCHED SET of six, which is probably worth a few extra dollars.

WTF ?

You are quite right of course, it is just that every time I have done it, the head has been off for a quick valve grind and check of the seats and so on. Sorry about that.

If the inlet valve is closing, and the engine otherwise runs normally, It sounds like the hydraulic lifter may have collapsed. It cannot now maintain internal oil pressure for some reason and pump up to maintain zero cam/follower clearance. If the engine is only running on five cylinders, you might have either a bent valve, which can no longer close, or broken a valve spring (unlikely). GTST cams have 240 degrees duration, and GTR cams have 240 inlet, 236 exhaust duration, but slightly more lift and very slightly more aggressive profiles. What the GTR cams do have though, are long clearance ramps at valve opening and closing to take up mechanical clearance of the GTRs solid lifters. These clearance ramps hold the valves open a minute amount during valve overlap (if you keep hydraulic lifters) giving a lumpy idle. The result is, you will get a distinctive cammy idle that will sound either wonderful, or terrible depending on how you feel about it. The slightly faster opening and closing, and lift, will give you about 2Kw extra power flat out. If you got the cams free and fit them yourself, go ahead. If you bought the cams, and have to pay to have them fitted, you will have spent a lot of money for no performance gain. To do it properly you need to remove the cylinder head and fit the solid lifters which need to be adjusted with shims. This can only be done with the head removed. A very expensive operation to have done, and there will still be no performance gain.

As you already know, wheel offset moves the wheel rims in or out with respect to the plane of the wheel flange and studs. This effects several things but mainly front scrub radius and wheel bearing loads. The most important is scrub radius. When you steer the front wheels there are a couple of ball joints that act like a hinge and allow the wheels to steer. If you draw a line through these two ball joints it will hit a point on the ground somewhere within where the tyre patch contacts the road. The actual point on the ground where the tyre pivots will never be exactly at the centre of the tyre contact patch on the road, also the axis of turning is never exactly vertical either. Now the guys that have designed your front suspension have worked out all the geometry, and the front end alignment settings to give the car good steering feel and handling characteristics. What you want is good self centering, so the car does not wander at high speed, sufficient feedback through the steering wheel when cornering without the steering loading up and becoming too heavy, and ability to handle a flat front tyre or blowout without ripping the steering wheel right out of your hands. Sometimes they decide to change some front suspension parts and they might change the wheel offset to improve the handling or feel after a lot of testing. If you want to fit odd aftermarket wheels just for looks, be prepared for some changes to either the handling or how the steering feels. Changing the wheel offset by huge amounts can also change the stresses on wheel bearings and wheel studs. As these are so heavily over-designed, I doubt if either will ever give trouble, but it is something to think about as well.

Flows 95 cfm over stock eh ! I would like to see that. A bog stock bare head flows about 94 CFM at 28 inches of water, so adding this trick plenum doubles cylinder head airflow. Ha ha ha. Yeah, in your dreams only I am afraid. I bet these clowns do not even posses an airflow bench.

Multiple throttle bodies only give you better throttle response, not more power. If you think about it, when the throttle is fully open it does not really matter where it is located. At full throttle all you want is a big open hole for the air to pour through. It is true that any decent racing engine has multiple throttle bodies as close to the valves as possible, but they are not there for power. Actually the reverse is true. Multiple throttle bodies can never be larger than the intake runner size, but a single throttle body can be as large as you want to make it. If all you want is maximum steady state dyno horsepower, a single large throttle body is the way to go. In Japan The fastest drag racers all chuck the multi throttle bodies, and fit a single large throttle body on their GTRs for that very reason. But suppose you wanted to drive a formula one car around a wet race track on the absolute limit of adhesion. A single throttle body would be undrivable. Ever hear those things revving the engine in the pits? The rate the RPM rises and falls is unreal. No formula one driver would ever want to hear about a sluggish big horsepower single throttle body engine. Now some guys like the sound that six open trumpets make at full throttle, and that is another thing entirely. You only have to figure out a way to run it with a MAP sensor instead of an airflow meter. And how the lack of an aircleaner is going to quickly destroy your engine. But if you want to spend a few thousand to get that great induction sound, and do not really care about the minimal extra power gain, or reduced engine life, then go to it.

Just ask yourself one question. If a slightly larger throttle body is going to give you a 30% power increase, why did Nissan decide to fit a smaller throttle body to deliberately restrict power by so much?

Those ports look the same to me, allowing for the fact that the GTR head has had the valves removed which effects the lighting conditions. Also the viewing angle is different. There is a difference around where the injector sprays, but the actual port and valve sizes are identical. Its an interesting picture to be sure. I have an RB25 head and an RB26 inlet manifold here, and when I find time, intend to make up an adapter plate. Some of the studs line up, and so do the ports, but an adapter plate is still quite a bit of work. This has been done many times before by others and is well worth the trouble.

I think the point here is that the two engines ARE totally different, but all the differences have to do with long term durability under extreme operating (endurance racing) conditions rather than actual power potential. Yes the blocks are different. The difference is the GTR block has different oil pan rails for the 4WD sump, and an additional oil drain hole for the second turbo. There is no reason why an RB25 block would not be just as good, unless you wanted to run 4WD, then you might have a bit of a problem. All the moving parts interchange perfectly, and there is no strength difference. The oil pump has a slightly larger displacement and runs dual springs in the pressure relief valve on the GTR. The only advantage of the larger pump is at idle, when you have a second turbo. A GTR road car may spend a considerable time idling, and the lower oil pressure might cause the oil light to come on if a smaller pump was fitted. At anything above idle, the relief valve will be open, and there will be full oil pressure. I am not sure why the GTR has dual springs in the pressure relief valve, but the only reason I can think of is reliability. The cost of the extra spring is SFA, so if there was a technical reason why it was better, all Skyline engines would probably have dual concentric springs fitted. For flat out racing, a smaller displacement oil pump would work fine. It is only the road cars that really need the big pump ! The GTR water pump has a different impeller, but is otherwise identical. This is to allow higher sustained engine speeds without cavitating the pump. For anything but sustained racing conditions the RB25 pump will work fine, including drag racing. But if you are planning to hold full throttle for over a minute at 9,000RPM plus, the GTR pump is definitely the one to have. I could go on about larger head bolts (10mm/12mm), sodium cooled exhaust valves, and solid tappet camshafts, but you get the general idea. The manifold bolt patterns are very slightly different, but only so you can get a spanner onto the nuts with the two different manifold shapes. The port shapes sizes and locations are identical. The power potential of the RB25 with identical external bolt ons (manifolds + turbos) would be the same. But for long distance endurance racing the RB26 would be going long after the RB25 died. There is no doubt that he RB26 is a far better engine, but if you actually need all that stuff to drive around at less than 100Kmh is doubtful.

Well thats not quite true. If you take just the short block, and replace the crank, rods, and pistons, you would still need to fit the GTR oil pump and water pump which are both different to the RB25 parts. Up top, although the combustion chambers, ports, and valve sizes are the same, and the GTR head has no power advantage. But everything is totally different except maybe the cam drive sprocket on the exhaust cam, and the timing belt and idlers. The RB26 has heavy duty parts throughout, and although a lot of things look the same, and fit, they are actually quite different.

This whole air-filter business is really quite amusing. Normal atmospheric pressure is around 410 inches of water gauge pressure, so if your stock air filter has say 4 inches of water pressure drop at full power, you are seeing (406/410) or 99% atmospheric pressure after the air-filter. So you fit some monstrous expensive aftermarket air filter box or pod, that is advertised as having guaranteed TWICE the airflow of the stock filter. So you fit it, and sure enough there is now only two inches of water pressure drop at full power. There is now 408/410) or 99.5% atmospheric pressure. So expect an 0.5% power gain. A far more important consideration is air temperature. Air density works from absolute temperature (the Kelvin scale). To convert Celsius to Kelvin you add 273. So 27C equals 300K. So for every three degrees of temperature rise, you loose one percent in air density, which equates to roughly one percent power. So your new super air filter has about the same effect on power as lowering the intake air temperature about 1.5 degrees. So use whatever type of air-filter you want, or is convenient, and concentrate on getting the coldest possible inlet air. There are far greater gains to be had that way. But a lot of guys prefer a brightly coloured chrome pod right behind the radiator, because it looks nice when you open the bonnet. On the other hand a stock air-box with partially concealed cold air pickup behind the front bumper, will probably work far better and keep the cops happy as well.

A very great deal depends on the rate of airflow through the plenum. If you think about it, airflow at idle is going to be pretty even with any type of plenum. It is only when air velocity starts to rise to high figures that the air distribution begins to become more uneven. I have heard so many times about this terrible air distribution problem with the stock GTR inlet plenum. I would like to bet that a stock RB26DETT running stock boost and power levels, has a pretty good internal air distribution. If you look inside the plenum there are steps, ribs, and all sorts of strange internal features to break up the airflow to give more even distribution. I bet the Nissan engineers spent quite a bit of time getting this feature exactly right. Now, some guy builds up a 950 horsepower GTR engine, and suddenly the air distribution in the stock plenum is crap. The air velocity is probably something like three times as high as stock, and it just piles up at the back, and sucks all the flow out of the front runners. So he replaces the stock plenum with a Trust super plenum or something similar, and the problem goes away. Some guy with a stock GTR engine pays big dollars for that same plenum, because "it must make big power". It would be a complete waste of money on a stock engine, and make no measurable extra power. The thing to realize is that at near stock power levels you can move the throttle body to the front without any very serious problems arising. But if very high power levels are anticipated, cylinder to cylinder air distribution needs to be taken a bit more seriously. Maybe your engine needs a big dollar plenum, and maybe it does not. But do not expect massive power gains from one on a mild engine.

The point Sydneykid is making, is that the HKS is more efficient at higher boost than the Garrett. Suppose you wanted to make a certain power level, so you gab a particular turbo that was rated at say 400BHP. Now a guy with a 1.5 litre engine is going to have to run pretty high boost to justify that big turbo. Another bloke with a 3.0 litre engine decides to run the same turbo at the same final power level, but he can do that with far less boost. So both engines end up having very similar airflow requirements at very similar power levels, but the little motor runs very high boost, and the bigger engine low boost, to achieve that same power. A particular turbo might be far more suitable for one set of operating conditions than the other.

Hello Sydneykid. What is your approach port matching ? I have done it a couple of times, and have my own method, although it is a fair bit of work. What I do is very carefully make a sheet metal template that just slides onto the manifold studs, and with a die grinder, match the metal template to the head ports. I then transfer the template to the inlet manifold, and remove minimum material from both, so template and manifold match exactly. Then go back and check the head again. Eventually the metal template matches both exactly, so in theory the manifold should then match the head as well with a very smooth transition. I am in the process of rebuilding and upgrading my flow-bench at the moment, and find all this particularly fascinating.

The only difference is the pistons, everything else is identical.

There probably are lots of R33 GTS-4 turbos around, but none from the factory, it is a popular modification as you would expect. There are lots of single turbo GTRs getting around as well, that does not mean it must have been factory option at some time.

Hi Joe, you finally sold it ! I am still looking for a manual R33 GTS-4, but they are very scarce indeed. Not sure about your comment on the GTS-4 drivetrain being not as strong as the GTR drivetrain. There are only two differences the clutch, and the n/a cars have only four stud wheel hubs. If there are any other differences please elaborate, because I have researched this quite thoroughly, and it is exactly why I want a manual car myself.

Not sure what it is, have a look ar the engine number, its down near the alternator. At least that will tell you if its an RB20 or an RB25. The neo looks completely different to what you have there.

I have heard that the N1 block is different and supposed to be somehow "better", but as far as I know all the other RB26 blocks are the same. I believe the same block casting is also used in the RB25 AWD engines used in the R33 GTS-4, and the R34 RB25DET neo used in the Stagea. All these engines use the alloy 4WD sump, and have the special pan rails.