Sydneykid

There is a movement ratio and a leverage ratio to be considered, hence 8 / 2 (movement ratio) = 4 / 2 (leverage ratio) = 2 Cheers Gary

I would add that unused fuel eg; when the throttle is closed, is returned to the tank. Which in our case means the fuel has been around the hot engine bay and picked up heat on its travels. When the car has a huge fueling system to cope with its demands at full power, the fuel can do several laps of the engine bay just idling at a set of traffic lights. This is why Skylines standard have ECU controlled voltages to the fuel pump, when the engine demands are low the ECU limits the voltage eg; 9 volts instead of 12 volts, which means the pump pumps less fuel. This is particularly important for E85 users as ethanol has a lower vaporisation temperature than petrol. This is what causes the more frequent stalling and acceleration hesitation during and after pit stops for the V8Supercars. Cheers Gary

In order to understand what a particular spring rate means to ride (what you feel) and handling (what the tyre feels) you need to know the movement raito and the leverage ratio of the spring to the wheel. In Z33, V35 and M35 they are both around 1.1 for the front and 2.0 for the rear. This means a 12 kg/mm front spring rate = an effective rate of 10 kg/mm And a 8 kg/mm rear spring rate = an effective rate of 2 kg/mm As a rule of thumb, nice ride and good handling, requires an effective spring rate balance that is close to the weight distribution. So a weight distribition of 60% front and 40% rear should have corresponding spring rate spread. It's pretty obvious that 10 and 2 kg/mm are not really suitable effective spring rates for a car with 60/40 weight distribution. If 12 kg/mm (10 + 2 = 12) is a suitable total rate, then the distribution would be far superior at 7/5. (ie; 7 / 12 = 58%). The car would both handle and ride better with that combination. Generally speaking in a front engine, RWD car, I would specify slightly higher front spring bias, so around 7.5/4.5 (63/37) would be where I would start. Dampers do not affect how the spring holds up the car's weight and how it absorbs impacts. Changing the damper rate makes no difference to how much the spring compresses under load. What damper rates can do is change the timing, more damping = a longer time for the load to take effect. That can be bump (compression) or rebound (extension). Simplistically, when a car hits a bump the spring compresses to abosorb that impact, a damper with a high bump (compression) rate will slow down how long the spring takes to absorb the bump. Too much bump damping means there isn't enough time for the spring to deflect, the bump is thus not absorbed and the impact is passed into the chassis and hence you. Conversely excessive rebound (extension) damping mean the recoil of spring after it absorbs the impact is delayed. In some cases that means the next bump is hit before the spring returns to it's full height and is therefore unable to absorb the next impact. Cheers Gary

2mm extra stroke = 1mm extra piston rise. So they might be OK depending on where the rings are located in the RB25 pistons and how thick their piston crown is. Machining 1 mm of the piston crown is no big deal for most forged pistons. Cheers Gary

GUESSES ! I'm not guessing, I've tested it, on a car and on the flow bench. I know from that testing that until you get to 45 lbs of air per minute (that's enough for 500 bhp) the standard RB25 throttle body poses no restriction. Cheers Gary

9 years, 10 in couple of months 1 bar of boost 6500 rpm limit 300 rwkw Cheers Gary

Wheel bearings themselves are not normally a problem, I can't say as I have replaced a wheel bearing in an R32/33/34 ever. But they do require adjustment and regular greasing, especially when you get them super hot at a track day, even high temp wheel bearing grease breaks down eventually. A regular (road car) mechanic may not have experience with the sorts of braking temperatures you are subjecting your wheel bearings to. I wouldn't buy Nissan branded parts eg, wheel bearings, ball joints, rack ends, tie rods etc, they are all made by subcontractors anyway. Ball joints, tie rod ends etc are all 555 brand in Nissan boxes and the 555 brand will cost half or less. Wheel bearings from memory are NKN, same story applies. Cheers Gary

Too simplistic, there are lots of times when there is positive pressure inside the cold air box when the car isn't idling. For example, what happens at 275 kph when I back off the throttle. not close it, just lift a little, for say the kink into the chase at Bathurst? Or the turn 1 at Oran Park? Or turn 1 at Eastern Creek? It still has boost so it can't vent via the one way valve and there is positive pressure inside the cold air box, so is it feeding positive pressure into the sump? No blow by, just a lot of oil pumped into the head that can't return to the sump making it's way out the cam cover breathers and into the catch can? Long left handcorners with high G forces such as Read Park to MacPhillamy at Bathurst? The oil is trapped on the RHS of the head by the G forces? Or up Mouintain Straight and through the Cutting, where the oil is forced to the rear of the cylinder head by the climb? I don't know about yours, but my car spends lots of time not idling and not on full throttle, about half in fact. Plus it spends most of it's time with high G forces, lateral and/or longitudinal pushing the oil around? Add those influences into your thinking and I bet the answers are no longer the same. Cheers Gary

The problem with the standard PCV valve is that they don't like a lot of boost, too much over 1 bar and they leak. You would need a decent aftermarket one way valve as there isn't a PCV vlave that is have seen which will handle lots of boost. The RB25's ones are plastic. Where doe the separated oil go? Fill up the catch can, leaving the sump short on oil? What happens when you have positive pressure inside the cold air box? Cheers Gary

It looks to me like they are using the vacuum take off (on top of the throttle bodies) for the brake booster, which is what I do on the R32. It replaces the PCV valve, which isn't used anymore. The alloy cylinder on the RHS strut tower looks to ba an oil/air separator, the air then flow from it into the large catch can near the RHS head light. Any oil collected in the separator could be returned to the sump via a fitting on the RHS of the block/ sump or by the dip stick tube.. Which is what I do on the R33. Cheers Gary

The grab and shake methods work for me, then a final check with a dial gauge. Jack it up, support on stands (as always), then lay on the ground and get your hands dirty, wiggle stuff, feel for lost motion and free play, listen for knocking noises, use a the old "screw driver up to the ear" microphone to get into where your head won't fit. Specifically; Inspect / test the lower ball joints for wear? Jack it up, grab the uppper lower halves of the wheel, one half in each hand and try to rock it, any motion (free play) will be easily felt. Plus you can usually hear the knocking. Inspect / test the wheel bearings for wear? Same, just grab the front and rear halves of the wheel, you will feel any free play and most times you can hear the grong grong grong of a stuffed a wheel bearing Remove rotors and inspect the rear of the hat / hub for good prep. Clean it with brake clean and a rag, maybe give it slight scuff with emmery paper. Once they are clean, check the hub run out with a dial guage, then bolt the rotor on and check the run out of it. Do the same "grab and shake test" for tie rod ends. I would also suggest a rotate test for the CV joints, grab the shaft and rotate, feeling for free play and tight spots, plus listen for noises. Don't underestimate the braking area ripples at Sandown, especially if you aren't feeling it elsewhere. Cheers Gary

Hey Dunk, is it true that the Commondoors don't have to run the class control tyre (Kumhoo) while everyone else does? Cheers Gary

My first guess would be wheel bearings, but don't rule out the rotors. Not necessarily warped, but I've seen lots of cars with badly fitted hat to hub because of poor surface preparation. For example if the hub is not perfectly clean when new hat/rotor is fitted then the rotor runs out of true. That pushes the outer and inner pistons in oscilation, cancelling out each other as far as fluid movement is concerned, so you don't feel a lot through the pedal. BTW the beaking areas at Sandown are quite ripply so it may pay to test the shudder elsewhere on the circuit. Cheers Gary

I have run over 320 rwkw through a standard RB25DET throttle body with no measureable boost difference before and after the throttle body. Unless you are looking at higher power outputs than that, the standard throttle body is not a restriction, so changing it or enlarging it will make zero difference, waste of time, money and effort. Cheers Gary

Last time i sent a pair of swaybars to the US the air freight cost was over $A400, door to door. So you would be better of buying a pair from the Whiteline US agent or your local outlet. There are now 50 or so outlets in the US for Whiteline. http://www.whiteline.com.au/dealer_REGION....scription=North America&type=state&region= Cheers Gary

Front or rear? Diameter? Cheers Gary

The T66 is a better match for the injector size, especially if you want to run it on E85. The cam selection is then much easier, with one complication, I didn't see larger exhaust valves on you list of mods and RB's have a missmatch between inlet and exhaust valve sizes ie; the exhaust valves are too small. Even a small (and cheap) upgrade by 0.5 mm makes a noticeable difference. If you stick with the standard valve sizes then I recommend using a slightly longer duration exhaust camshaft. Sure it's a band aid, but it's effective and a no cost option. All of the cams I would be looking at will require head relief, solid lifters and changes to suitable valves and valve springs anyway, so I would do the exhaust valve size upgrade at the same time for zero extra cost. The T66 is going to give you good boost at 4,000 rpm and will taper off a little at 7,000 rpm running Pump 98. Running E85 will extend that by 500 rpm due to the oxygen content. So what you are looking for is an inlet camshaft duration that works from 4,000 rpm to 7,500 rpm. I always go for the highest lift I can find at the target duration, keeping in mind the useable rpm range. Personally I have a soft spot for Jun cams, they have worked for me everytime, so the choice is between the 264 & 9.7 mm and 272 & 10.5 mm, personally I would go for the 272's & 10.5mm. There is higher lift available in 272 degrees but for road use it will be very doughy under 4,000 rpm with more than 10.5 mm of lift. If you prefer HKS then their equivalent is 272 & 10.2 mm. That would give you some headroom if you decide to use the GT45 with some bigger injectors, but realisically you are already going to have serious traction problems with the T66 at around 650 bhp on E85, you could stretch that to around 700 bhp with some more fuel pressure. In comparison the GT45 would be unuseable on the street. You may also want to think about driveline durability, the T66 is pushing it and the extra torque from the GT45 will break most things in the drive train. Cheers Gary

Add me to the Paul and Rob list. I've posted it up eleventy billion times, run engine for 20 minutes, until it is nice and evenly warmed up to operating termperature and change the oil filter. Then drive to Bathurst, have breakfast with the guys to let the engine cool a bit and then drive back, that's around 450 k's. What I don't see on the list above is the next step which is "check the leak down". That will tell you if the rings are beded in, the bearings were run in by the time you got it out of the driveway. If the leak down test is OK, then drop the mineral oil, change the filter again, fill 'er up with synthetic and off for the final tune. This pussy footing around for thousands of k's achieves nothing. Cheers Gary

Where are you measuring the boost? I always have at least 2 places for measuring boost, one at the compressor outlet and one past the throttle body/ies. That way I can tell if there is any boost drop due to restriction in the inlet ie; the pressure at the compressor outlet exceeeds the pressure at the engine by more than a couple of psi. If they are both the same (the boost drops the same) then there is either an air leak or the turbo has run out of airflow. Cheers Gary

I assume the pictures are taken from the rear of the tyre and the slow down lap wasn't all that slow. As Showza posted above skin temperature isn't always a good indicator, you need to get below the surface to get a true view. That said, it's a place to start the thinking. The LHS tyres look pretty good, reasonably even. The RHS tyres shows too much camber, as you would expect from a clockwise circuit. The LHS front maybe needs a little more pressure, maybe 1 lb Both of the RHS tyres need more pressure, maybe 2 lbs. At Wannaroo we always run less camber on the RHS than the LHS in an attempt to get more of the load onto the inside tyres. Share the traction around for cornering. Plus it helps under brakes with less camber on the inside tyre. As well as staggered camber we also run staggered tyre pressure (as I mentioned above). Gotta go, Eastern Creek this weekend and I have lots of cars running. Cheers Gary

20 cents worth of short comments; RB20 standard oil pumps flow a lot less than RB26 oil pumps. Oil pressure is measured in the block at the main oil gallery, which is below the flow restrictors. Hence oil pressure has no relevance as to how much oil is in the head. The big advantage of dry sumps that we see for horsepower is the removal of oil flying around in the crankcase, the crank spins much freer as a result. So when considering the advantage of partial vacuum in the sump, the further lack of flying oil is more important than the partial vacuum (ie; less air) on its own. Piston rings (eg; top and 2nd ring) seal better with pressure on their upper surface, having a partial vacuum in the sump (ie; below the rings) effectively increases the pressure above them. The need for pressure to push the ring against the bore is why we don't use a gapless ring in the top, only in the 2nd ring. Oil control rings don't need external pressure, they have sufficient internal spring tension. Cheers Gary

When GTR's have a fair amount of caster that can be a problem, pulls the wheel forward and obviously the drive shafts go wth them. Cheers Gary

The GVM (Gross Vehicle Mass) includes the full compliment of passengers. fuel and luggage. It used for determining the most the car will weigh for things like the tyre loading. Cheers Gary

When I am chosing camshafts the first thing I do is figure out what rpm range I am going to need the camshafts to work in. One of things that determines the rpm range is the size of turbo. Next I check to see that the rest of the package aligns with the turbo. This is where I run into problems with your selection. That's a 1000 bhp turbo with injectors that are only good for around 800 bhp on petrol and 650 bhp on E85. So either your turbo selection is too big, meaning that you will have a ship load more lag then is necessary for the power output. Or your injector selection is too small. Either way I can't make a camshaft suggestion with such a missmatch in components. Cheers Gary

That's OK, it's your choice after all. You are fully entilted to choose to look uber cool rather than go fast. Heck, take the springs and shocks out all together, whack a bit of 4 x 2 in there instead, you can get it even lower then, no need for suspension travel Just don't brag about how powerfull your car is because it wheelspins all over the place, when the truth is it has no traction because looks are more important to you than going fast. BTW, why have bothered building a big power engine when you can't use it? Hey, it's a free country, other than the taxes, the police, the inspection nazis in SA, speed cameras, toll roads..............maybe it's not all that free when you think about it. Cheers Gary