Sydneykid

Easily, but they understeer like cops when you do. PS; By "4wd" I assume you mean 50/50 power distribution.

The theory is the hole bleeds off a very small amount of boost when the airflow is low, so it smoooooths out the transition between no boost and some boost. It is really too small to lower the boost once the turbo is at its max airflow. So if you want a very slightly faster boost then block the hole. But you shouldn't expect a max power increase. Hope that helps:cheers:

Funny thing, that's what the R33 GTST owner, the one that dropped his ceramic in the cat on the way up Mooney Mooney, said. I told him not to go over 10 psi but he said "my car isn't going on any race track". He was man enough to ring up and tell me what happened, his closing words were "you were right". Roll the dice, it's your money

Oh no, the old "BOV's don't do anything" line ............. Why did Nissan fit them? Why did the early turbo engines (someone used the NICS and RB30ET examples) not use them and had recommended turbo servicing at 60,000 ks'? Why do the later Nissan engines have recommended turbo servicing at 120,000 k's? Does anyomne really think that Nissan wasted money on BOV's, fitting something that wasn't necessary? They would have saved millions of dollars over the life of R32/33/34 and S13/14/15 and Stagea and Cefiro and ............you get the drift. Does any out there really believe that comparing race cars with no BOV's and road cars is realistic? Give me a break, we service turbos every 2,000 ks' of racing. Personally I don't want to be doing that on my road car. With a boost gauge plumbed to the comprressor housing you can easily see what happens to the pressure at the compressor when you close the throttle without a BOV, double the set boost limit is not unusual. Does any one really think that that is somehow good for your turbo? Everyone has heard the turbo flutter noise when the throttle is closed and no BOV is fitted and noise = vibration at the tubine blades. Does any one really think that that is somehow good for your turbo? As for slowing the rpm versus reversing the flow. On the engine dyno I have seen large amounts of air flow out of the compressor inlet on throttle close. That air is coming from somwehere and it has to get past the compressor blades to get out. So I have no problem with the thought that the compressor blades stop or turn backwards. Even if they only slow rapidly, does any one really think that that is somehow good for your turbo? Sorry have to stop this post, there is a car on the dyno that needs me......

First let me say that I personally have seen no difference in the power output of the plastic compressor wheel versus the steel. The R34 GTT made 221 rwkw at 13 psi using the standard turbo with the plastic compressor wheel (it had the usual bolt ons, FMIC, split dump, hi flow cat, panel filter, Power FC with Boost Control Kit and an adj exhaust camshaft pulley). That turbo lasted 5 laps at 11 psi until the ceramic in the cat disease killed it. The plastic compressor wheel and the steel shaft were both still in perfect condition by the way. I have seen this happen to multiple RB25 turbos, running ~12psi. Not all on the track, one let go going up a long hill (Mooney Mooney for those in NSW) at 13 psi in 3rd and 4th gear. It had 4 people and some luggage and the driver was "fair up it" (his words). I have also seen one that failed on a long, fast trip (Sydney/Sunshine Coast). So, I NEVER use more than 10 psi with the standard RB25 (all models) turbo. I haven't been able to get 200rwkw out of an RB25 (R33 S1, S2 or R34) using the standard turbo and piggy back controllers. I always need to upgrade the ECU, with a Power FC being the current/long time preference. The reality is I have to compromise when using the standard ecu. The air flow bender might get the A/F ratios pretty close but then ignition timing is too advanced. I can adjust (retard) the static igntion timing, but then the engine feels dead in the commonly used rpm range. So I advance the static timing a bit and back off the bending to get the dynamic ignition timing better. Then the A/F ratios are not so good. As I said it's a compromise, go round in circles, that seems to limit me to a bit less than 200 rwkw. Ditch the standard ecu, the piggy backs and use a Power FC and all that compromising is gone. Hope that is of some help:cheers:

As usual Steve is right, there are better methods than horizontal throttle butterflies. The SuperTourers use barrell throttles so that there is no spindle in the way at WOT. The V8Dinosaur uses slides, again so that there is no spindle in the way at WOT. I do some work on a car that has verticle spindles, they line up with the port divider between the 2 inlet valves. It shows a small gain in power over the horizontal spindles. The current generation of BM's don't even have a throttle as such, they use variable valve lift to control engine power. Barrell throttles are expensive to make. Slides don't work very well on forced induction engines, the pressure on the closed slide makes it very difficult to open them. Changing an RB to verticle spindles would be a nightmare to equalise the flow to each cylinder, it is hard enough on a 4 cylinder. But what design of throttle control device is really secondary to this discussion (which we have had a number of times in numerous threads), the real question is how big and where. The bottom line for me is pretty simple; 1. For a circuit race car, multiple throttle butterflies close to the inlet valves give better response than a single throttle body many litres of airflow away. This is both logical and well proven in the field. Up to the power levels we have used (~650 bhp) there is a noticeable loss of instant throttle response when a single butterfly is used. I have seen the same result on SR's as well as RB's. 2. For a drag car, I would be chasing every single horsepower, so removing the turbulance and restriction of the multiple throttle butterflies would be on my list. But I am not sure where it would rank on that list, there are so many other things that would rank higher. I have seen a number GTR's in Japan run low 9's using the standard throttle bodies and standard plenums. Theo here has run many, many 9's with the standard throttle bodies. So if I was building a 9 second capable car, then there is an argument that says spend my time and money on the other things on the list first. If I was building an 8 second car, then there is really no question, I would have a large plenum and a big single throttle body. And it would feature pretty early on my list. 3. For a road/combo car I see no reason to give up even the slightest amount of throttle response. Personally I hate lethargic engines (or chassis for that matter), they need to respond to my inputs instantly. Probably comes from too many laps around circuits. As Steve said, everybody is entitled to their opinion and that's my 20 cents worth:cheers:

The piston speed of the RB30 piston at 7,500 rpm is slightly lower than the piston speed of the RB25 at 9,000 rpm (ie; 21.25 versus 21.30).

Steve is quite correct, but we have to replace MAP sensors quite often. Especially the cheap aftermarket ones. It is worth noting that a large number of supposedly failed AFM's are in fact simply dirty due to poor airfilter selection, maintenance or over oiling. I believe this is the cause rather than weak AFM's, as I have never replaced an AFM on a Skyline with a standard air filter.

The ARP main bearing stud kit screws straight in, no mods required. If you are using an RB26 head then you have to drill and tap the RB30 block for the larger RB26 head bolts. So drilling and tapping for the even larger ARP head studs is no extra work. But be aware that you can't simply use a hand drill and tap, the studs have to be perfectly parrallel to each other and at 90 degrees to the block surface, otherwise the head will not slip over the studs. Hope that helps:cheers:

RIPS are the only people I know who sell them.

No worries, 400rwkw warms them up pretty quick:cheers:

Take a look at www.fc-datalogit.com then ask any question you might have. I am always reluctant to to replace AFM's (standard Nissan OEM quality) with a MAP sensor (aftermarket quality), "just one more thing that can break". Simply put, there is no more accurate sensor for measuring the actual airflow into an engine than an AFM. A MAP sensor looks at pressure and "guesses" the airflow. I strongly suggest you look at what you are trying to achieve with the car, then look at what other similar cars use to achieve that result. I find this to be a much better approach than looking at specifications of components that I might think suit the application. I use this car (VMax) as an example often, it uses a Power FC and AFM's, makes well over 1,000 bhp and runs 8's at 160 mph. Hope that is of some help.

Hi Mark, I was faced with your situation with my own personal R32 GTST, the old RB20 had done 170,000 k's and the gearbox the same. I seriously looked at an RB25DET (non Neo) engine and gearbox, cost ~$7K. Then I looked closely at what I really wanted, the standard RB25 simply wasn't going to cut the mustard. It needed upgrades to get to where I wanted it (500 bhp), then I added up the cost of those upgrades, ~$8K. The reality was for way less than ~$15K I could build a serious 3.1 litre (RB30 bottom end with an RB26 top end), that would make the power target easily. It is worth pointing out that the RB25DET Neo is not a simple fit into the R32GTST. You need to factor in the costs associated with necessary changes to the wiring harness, ECU, sensors, clutch, tailshaft etc. A couple of examples might help. Firstly, the Neo version of VVT (note that the RB20DET doesn't have ANY VVT) is infinitely variable, not on or off like the early RB25s'. This requires a "Neo" ECU, or if you intend tuning it, an ECU capable of that sort of control. They are not as common (read cheap) as the non Neo Power FC for example. Secondly, the gearbox outut shaft is not the same as the RB20's nor is the gearbox the same length. This means a front tailshaft has to be made using the right yoke. Another, if you ever want to upgrade the cams you have to buy Neo camshafts, they have solid lifters not hydraulic like earleir RB25s'. They are much rarer (read more expensive) in the used market. Moving on to injectors, Neo injectors are not the same as the earlier model's, they are much harder to find upgrades for (read more expensive). Don't get me wrong, I really like the Neo vesion of the RB25DET, it is by far the best. If I had a maximum power target of 225 rwkw (usual exhaust, filter, tune mods), then they are hard to go past. But if your power target is higher than that, then I strongly suggest you add up ALL the costs to get there. Hope that made some sense:cheers:

Hi Chris, I agree with you on the 1JZ versus 2JZ comparison, but there is a 14mm difference in their strokes. This is not a reasonable comparison with the 2.7 mm difference between an RB25 and an RB26. Having dissassembled quite a few, I can say that the RB26's seem to built by Nissan with much tighter tolerances than RB25's and the standard balancing is far superior. In my humble opinion, any smoothness advantage in an RB25 is purely their state of tune, nothing to do with their 2.7 mm shorter stroke. At this point is is worth noting a couple of things. Firstly, there is plenty of evidence to suggest that a square engine (same bore and stroke) is the best compromise between rpm capability and torque development. Secondly, the RB30 has a demonstrably superior stroke/rod length ratio of 1.8 compared to the RB25's 1.6. So not only does the longer stroke give power benefits, the better stroke/rod length ratio accentuates this. As a bonus there is less side loading wear on the pistons, conrods, bores and bearings. Similar to you, I have a liking for high rpm, the 18,000 rpm of an F1 engine is very pleasing to my ear. Have a read of my previous post and then tell me if the $10+K you spend on transmission and top end upgrades to make an 9,000 rpm RB25 effective and reliable wouldn't make an RB31 sound pretty nice. Hell, for the extra money I could get the RB31 to rev to 9,000 rpm and then you would have the best of both worlds. There are many layers to this sort of discussion, the stroke comparison is really only scratching the surface.

If ALL other things are equal, the higher the RPM, the higher the wear rate. It's not a straight line either eg; 8,000 rpm is NOT twice as stressful as 4,000 rpm, more like 20 times in my opinion. But I have no hard numbers on it, I can't say a 7,500 rpm RB30 will last "X" and a 9,000 rpm RB25 will last "Y". What I can say is a 7,000 rpm RB30 (standard internals 475 bhp) will last a long time, we service one that has done over 50,000 k's and 4 1/2 years and it gets USED. The real issue here is cost, for the same power, it is a hell of a lot cheaper to build (and maintain) a 7,500 rpm 3.1 litre than it is to build and maintain a 9,000 rpm 2.5 litre. Of course the 3.1 litre will have better response and higher average power at lower rpm. If you look at using a 9,000 rpm 2.5 litre properly, you really need to considering gearing. The standard gearbox ratios are going to be too widely spaced, it will drop off the power band on upchanges if a close ratio gearbox isn't used. In addition some consideration may be necessary into using a lower final drive ratio (9,000 rpm is 20% higher than 7,500 rpm). This adds substantially to the cost.

Hi George, my cars have Castrol synthetic lubricants everywhere. So in the gearboxes we use Castrol Syntrax 75W-90.

Well if it has something wrong now, it will still have something wrong when the the Wolf goes in.

The idea of a BOV is to prevent the air from reversing direction when the throttle is closed. This has 2 effects; 1. It prevents the compressor being suddenly stopped (or run backwards) when the air rushes back the wrong way. 2. It keeps the air (in the intercooler and pipework) moving in the right direction ie; towards the engine. So it would appear to me that #1 would be satisfied no matter where the BOV is located. But #2 is best satisfied by having the BOV as close to the throttle body as possible. That way none of the air is going the wrong way. This would mean better throttle response when the throttle is re-opened. My 20 cents worth:cheers:

Wo, there's a couple of unrelated occurances. Are there any error codes on the ECU?

Multiple throttle bodies, close to the inlet valves are good for throttle response which is irrelevant on a drag car.

Where are you picking up the trigger signal for the timing light? Timing on a Skyline can be a pain, this is what I do to make sure the signal is pure...... I take the #1 coil right off and lay it on the cam cover. I them stick a piece of insulated wire inside the coil (like it was a spark plug) so it makes contact. I connect the other end of the wire to the spark plug. I loop the sensor from the timing light around the piece of wire. That way you get a nice clean signal from only 1 cylinder, with no delay (light flashes exactly when the plug fires). Hope that helps

Your kidding right, do you reallly believe that 1.35 mm extra crank throw would make an RB25 smoother than an RB26? The resulting 2.7 mm extra stroke is a non event in balancing terms. More likely is the individual tune of the engines you are comparing. Moving on, 9,000 rpm is no problem for the standard crank. But the cylinder head ancilliaries are not as easy (read cheap) to upgrade to handle that sort of rpm as an RB26. Other than the crankshaft, everything that goes up & down or around & around needs to be upgraded. Sure you can do it, what is required is well known, the parts are available, no rocket science there. But why bother? When you can do an RB26 for less cost. Why bother when you can do an RB31DET for similar cost and it will make more power using 7,500 rpm than the RB25DET will using 9,000 rpm, Why bother, when in comparison, it will do very few K's between rebuilds. My 20 cents worth:cheers:

I imported ours, the total cost $16K plus rego and insurance. I used these guys to source the Stagea in Japan, I simply told them colour preference and price range www.prestigemotorsport.com.au Ernie at Skyline Imports did the compliancing. Mac Customs did their stuff And Kiwi Car Carriers delivered it in perfect condition (to Skyline Imprts first, then to my house) DOTARS were a bit slow, even for a Govt Department It was pretty easy really, I would do it again.

In R32 GTST's I prefer the R32 RB25DE top end as it doesn't have VVT. The RB20DET stuff (sensors and manifolds) all basically bolt up, so the R32 GTST wiring harness and ECU work perfectly. Bits from the current set up, I assume you mean RB20DET. Note that the new RB31DET has an RB26 top end. So I used the injectors (S5RX7T), all the sensors, ignitor, coils, alternator, starter, oil cooler, remote oil filter, radiator (PWR), electric fan (Davis Craig), air filter (pipercross POD), heat shield, ambient air feed, Power FC, Commander, gauges (oil pressure & temp plus exhaust gas temp), sump (it already had wings & baffles), intercooler (std R33 GTR), some intercooler pipework, engine mounts, OS Giken twin plate clutch, fan belt, power steering belt, bottom radiator hose (silicone), alternator bracket, power steering pump bracket, throttle cable, fuel pumps, adj fuel pressure regulator (Nismo), adj camshaft pulleys (Jun), plus lots of mounting hardware, nuts, bolts and washers. We also have a Stagea, and I will use some of the (no longer needed) RB20DET bits on it. Like the RB25DET turbo (GCG ball bearing hi flow), split dump (Performance Metalcraft), old intercooler (Group A Supra), some pipework, boost controller (Autospeed) and exhaust (suitably modified). I try not to waste anything that is good/useable. Hope that helps, Happy New Year:cheers:

Hi Mark, simple answer, if you do turbo, power fc, gtr injectors, dump pipe and decent tuning the RB20DET will have a lot more power than a standerd RB25. Plus all those bits can be transferred over to an RB25, all it will need is a bit of further tuning. Hope that helps:cheers: PS; I have never seen an RB20 break an RB20 gearbox, driver abuse and lack of maintenance are the usual causes.