Sydneykid

Cool, thanks

Hi Timd, I used one of those for quite a while, very good cooling. The inlet air temperature drop was very good, much better than many other similarly sized intercoolers I have tested. It did get a bit of pressure drop over 1.1 bar, but it wasn't terrible until about 1.3 bar, then it went verticle. At 1.1 bar it made ~175 rwkw on an RB20. The inlet and outlet are 55 mm, while the standard RB20/25 pipework is 62 mm. So, if you are going to use one, you will need a couple of silicone reducers (2.5" to 2" is the common size). Hope that helps.

Pretty close, did they tell you why 38 mm? The brand of wastegate they suggested, did it have a 40 mm size? No tricks, I am just trying to find out the background info to help my understanding.

My guess is the pump is touching something when driving straight. Where corners are involved, the G forces push the pump away from whatever it is that it is touching. Time to pull it out and tighten up trhe brackets and move it away from whatever it is that it is touching. Hope that helps

Yo BOOSTD, the formula was about empowering you, as the Skyline owner, not about me doing calcs for everyone. Oh OK, but just this once; 280 rwkw = ~450 bhp 450 bhp / 11 = 41 lbs of airflow = 41 mm wastegate Now if you want to run 20 psi, then that's statistically the most likely sized wastegate. I can't say as I've ever seen a 41 mm wastegate, so the choice is 40 mm or 45 mm. For good response, personally I would go with the 40 mm wastegate. The reasons are in the previous posts. Hope that helps

Hi cerealeater, we always fit 2 mufflers to road cars, one around the gearbox (called a resonator by some) and one at the rear. Whether it is a 2.5", 3", 3.5" or 4" system we specify 2 mufflers, this fixes the resonance the annoying at certain rpm's. The power loss (if the mufflers used are efficient) is neglible. It's no good having an extra 20 rwkw if you can't drive the car because of the exhaust noise. Hope that helps

Mega is pretty much spot on, except that you can also buy offset bushes to fix the camber problem. You don't have to buy a complete adjustable arms, plus the bushes cost less. Adjustable arms also usually have spherical joints which are not a good idea on a road car as they wear fast and rattle lots. Hope that helps

Good questions Dr.... Quote: Surely it's not just a matter of open / closed??? Wouldn't the amount the gate has to open be a cruital factor as it will need to flow varying volumes to maintain a set boost level across a certain RPM range?? The wastegate responds to boost pressure. The more boost pressure on the diaphragm and it's spring, the further the valve opens. Ignoring early opening for a minute. If your target boost is 1.5 bar, when it the actual boost gets to 1.51 bar, the valve should open a little tiny bit. Now we all know that doesn't happen, the boost goes up so fast it flies past 1.5 and the valves opens vary fast. If the valve is too big, it lets too much exhaust gas bypass the turbine, boost drops fast and the valve closes. Then boost climbs rapidly again because the valve is closed. Valve opens and the cycle starts again. With the correctly sized wastegate with the exactly same spring rate, the valve will open just as far but it is smaller and so will bypass less exhaust. Thus it may not completely shut again. If it is correctly sized it should not have bypassed way too much exhaust gas, maybe only a little too much. So the valve just moves a little more open and closed to control the boost. Secondly it's a lighter valve (remember a 35 mm valve head is 50% of the weight of a 50 mm valve head) so it has less inertia and can open and close faster. Quote: As for the varying 0,3 bar... could that not be caused due to a poorly setup or inappropriate boost controller? Well that's what I thought, so I replaced the wastegate spring with one of the right rate for the target boost ie; no AVCR. Same result, fluctuating boost. So I used one of the Autospeed boost control systems (they always work for me), still with the right spring rate in the wastegate. Same result. So we changed the turbo to another with a slightly less aggressive compressor. Better, but not much. It was at this stage I suspected the 60 mm wastegate was too big for 230 rwkw. But I couldn't convince the owner, he believed and was continually told by everyone he spoke to, that bigger was always better. So I recommended that the guys put on a smaller wastegate (35 mm) with the original turbo and not tell him. Bingo no boost fluctuations. Oh, and it never lost 1 rwkw from the smaller wastegate, but it picked up a noticeable amount of response. This happened with another car (it had a heap more problems as well) and that's when I started thinking about a formula to pick up ridiculously (small or large) sized wastegates. Save a lot of time and money chasing other stuff.

I’ll try and look at each one separately… “What about turbo efficiency?” Efficiency, is that heat, low boost, high shaft rpm, poor response low airflow etc there are so many ways that a turbo can be inefficient. I don’t know which one to pick for an answer. “Exhaust manifold design/efficiency?” If the exhaust manifold is so restrictive it limits the power output, you would need a smaller wastegate to match that power. This is logical as the manifold is doing some restricting, so a larger (than ideal) wastegate would achieve nothing. “What if the engine is highly tuned to operate at a specific rpm (powerband)?” Thus it would produce more power at that rpm and therefore need a correctly sized wastegate for that power. You have to size the wastegate for the maximum power (airflow) of the engine. Since you have gone to considerable trouble and expense to have a tuned engine, I would assume that you would want to use it in that rpm range all the time. “I'm not sure if you are formulating a generic calculation to determine wastegate sizing or just providing a guide to wastegates based on current data” Both actually. Currently there is no simple formula for determining what size wastegate you use. There seems to be 2 schools of thought, the first being to buy the “biggest” one you can afford. This presumes that bigger is always better, but we know that’s simply not the case with wastegates. Secondly the car owner has no idea, so he has to ask his wastegate supplier. If he is genuine, he will give an answer based on his experience. But what if he isn’t genuine? What if he wants to make the most money he can? Then he will sell the one that makes the most profit for his business. In either case you can get the wrong answer (and the wrong wastegate), the first because his experiences may not match your requirements and in the second because he doesn’t care whether it is right or wrong for you. So what I thought I would do is use my experience, then supplement it with real world data from 30 or so volunteers. This would then enable me to come up with a simple formula that anyone can use to check and see if the advice they are getting from their local supplier is good or bad. Stuff like….. My local supplier tells me I need a 60 mm wastegate for my 200 rwkw Skyline. Why is he telling me something that is obviously wrong? Because it’s on special this month? He has 1 in stock that he hasn’t been able to sell? He only makes $100 profit on a 35 mm wastegate and $250 on a 60 mm one? It’s all about empowerment, so you (the Skyline owner) can sift out the BS. Hope that helps

the theoretical stuff....... 1. The wastegate size is relevant to how much horsepower you are targeting 2. If you want to run high boost, then a smaller wastegate is better than a larger wastegate. The idea being that in order to generate high boost you need most of the exhaust gas going through the turbine, not through the wastegate. 3. If you want to run low boost then a larger wastegate is better than a smaller wastegate. The idea being that in order to keep the boost low you need a lot of the exhaust gas going through the wastegate not through the turbine. But what is high boost? Well for the sake of this discussion I have settled on 1.2 to 1.4 bar (18 to 21 psi) as being the divider, thus 1. 2 bar and under is low and 1.4 bar and above is high. How did I arrive at this number? Well based on the results of the surveys, this seems to be the most common point where the wastegate sizes change from theory 2 to theory 3 (above). The next bit of theory is that it takes 1 lb per minute of airflow to make 11 bhp in a current generation 4 valve engine. This is a pretty well established piece of turbo sizing philosophy. But how do we relate this to wastegate sizing? Well referring to the results of the surveys, it seems a straight 1 to 1 relationship is not too far from the average, so 1 lb of airflow = 1 mm of wastegate diameter. OK R31 Nismoid, let's use your car as a discussion starter..... 300 rwkw = 480 bhp 480 bhp = 44 lbs of airflow = 44 mm wastegate Now if you want to run 20 psi, then that's statistically the right size wastegate. My experience indicates that to get 300 rwkw out of a GT30 you would need to run around 1.5 bar (22psi). So using the draft formula... 44 / 22 X 19 = 38 mm. So based on the 75% success rate of the formula in the samples so far, I would say a 38 mm wastegate would be the go. Hi Steve and Dr Drift, I try Steve's question first............ What I am trying to do with the formula is give a baseline, something to think about. A 75% fit type of thing. At the moment there seems to be a majority of guys wanting external wastegates who don't even know where to start. They have been told for big horsepower you need a big wastegate, which is not necessarily true. They have been told you can't have too big a wastegate, which is definitely not true. They have been told for high boost you need a big wastegate, which again is not necessarily true. In order to do this there is one main assumption, that the turbo is pretty much the optimium size for the target power and boost. If it is totally wrong then whether the wastegate is sized correctly or not is really irrelevant. The turbo / engine mismatch is gunna kill horsepower / response anyway. The other issue is exhaust flow rates through the wastegate, some manufacturers claim very different flow rates for the same size inlet / outlet / valve. Now I haven't tested every wastegate out there, but I have yet to see any difference in popoff valve type wastegates that I have tested. So for this discussion and the formula I have ignored the manufacturers claims. The Turbonetics flap style wastegate is an exception, they flow much better than the same size popoff valve on our flow bench. Ok moving on to the good Dr's question, "So if he's chasing more in the future and had to bear that in mind something like the turbosmart 45mm racegate or similar would be a good option?" Sorry, but more what? Boost or horsepower? It is possible to make more horsepower with less boost ie; with a turbo capable of more airflow. In that case the formula says you would need a larger wastegate. If you wanted more boost (and therefore more horsepower) the same size wastegate may well be OK. You can get to the stage with "more boost" when a smaller wastegate is needed. Interesting discussion??? Try this; More power = more exhaust flow More boost = more exhaust flow through the turbine More boost = maybe the same exhaust though the wastegate, thus same size wastegate Lots more boost = less exhaust flow through the wastegate, thus smaller wastegate Moving onto Steve's question......... More power = more exhaust flow Less boost = less exhaust flow through the turbine More power = more exhaust flow the wastegate, thus larger wastegate required Steve, try the formula on your car "40mm, 1.7bar, 309rwkw" 309 rwkw = 520 bhp = 47 mm 47 mm / 1.7 bar X 1.4 bar = 39 mm So the 40 mm wastegate looks OK. I suggest you have play with the numbers you are thinking about for your car, post them up and we can discus. KamikazeR33, it doesn't matter how many cylinders you have. The logic is that it takes X amount of air and fuel to get X amount of horsepower. So whether the engine has 4, 5, 6, 8, 10 or 12 cylinders to make 500 bhp is irrelevant. The only issue occurs if there is varying efficiency amongst the engines. Since I am limiting this formula to production, DOHC, 4 valve engines, I seen no real big problems in using the same calculations. BTW this is also why RPM is not considered. I need a bit more information on your "hypothetical" to really give a decent fact based answer. I would need to know usual stuff, the BHP, boost and wastegate sizes. In the interim I'll try and answer this one.... Quote: Also, about this "response" of a wastegate. Just say you are "coming on boost" very rapidly (as most larger, aftermarket turbos tend to), wouldn't you think that a wastegate that only needs to travel ~5mm to maintain the desired boost level (i.e. a large gate) as opposed to a smaller wastegate that would need to travel ~10mm to vent the same volume of gas would be able to do this faster, hence be more "responsive"? I concede the smaller one would be able to be more accurate in it's flow limiting, but then again wouldn't an "intelligent" boost controller be able to manipulate these regardless? I am not sure that the travel "distance" of a wastegate is really an issue. Remembering that a 50mm wastegate valve is going to weigh twice as much as a 35 mm one. So there is an inertia issue to be considered. I think that is really the crux of the problem. The diaphram has to move twice as much weight, in and out very rapidly. This has 2 undersirable effects incomparison to a smaller (more correctly) sized wastegate. Firstly the too large a wastegate has to open and close more often, as it has too little exhaust flow when closed and too much exhaust flow when open. This wears the diaphram, due to the requirement for more movements and more weight. Secondly all this opening and closing of the wastegate affects the amount of exhaust flow though the turbine, this leads to fluctuations in the boost control. eg; I have seen a relatively low powered engine, with a very large wastegate, move up and down 0.3 bar in its boost as the boost control circuit struggles to keep up with this open, closed, open, closed requirement. Hope that helps

Have a look at a Shoot Out mode dyno graph, there is a few on the forum, you can see the inputs.

Next car I have on the dyno (doesn't matter how much power) I am going to do a power run in 3rd and then one in 4th and post it. There is not much difference.

Hi Bass, typical anti lag, bad for turbine, exhauts valves, exhaust manifold, dump, cat, lambda sensor, EGT sensor and probably a few more I have forgotten. :headspin:

Time for a reality check, the Gibson RB20DET made 460 bhp for qualifying at 2+ bar, but they turned it down so it would last for the race to 420 bhp (that's ~260 rwkw). Admittedly that's with a circuit race power band, not a dyno queen one. I suspect 291.5 rwhp (215 rwkw) might be closer to the mark. :idea: But I could wrong.

Ooooo! :headspin: RB26 or RB25 manifold? Hi/front or low/rear? $? :wassup:

Hi Jaws, You are no doubt aware that RB25's have hydraulic followers and that you would be limited to ~256 degree cams with ~9.2 mm lift to retain the VVT. This means no change in valve springs is neccessary. If you wanted to run cams with larger lift or longer duration (therebye loosing the VVT) then you need a change to solid followers (as in GTR's). This should be done at the same time as the head is off. It is also worth noting that if you want more than ~9.5 mm lift, some very minor machining of the head (to clear the lobes) is also necessary. As for porting, polishing of combustion chambers and matching combustion chamber volume it is always worthwhile doing while the head is off. Hope that is of some help

Wow that's fantastic! That's the most powerful standard internals RB20DET I have ever heard of. Care to put up the dyno sheet?

The problem with this desiogn is it vents to atmosphere with no filter. :thumbdwn:

Does that that mean if it had less spent on the engine and some spend on decent tyres and suspension then it would have done a 9? :confused:

Don't feel privileged, it happens to all of us you know. :uh-huh:

Hi specialk, we only ever use the 450 bhp spec (Stage 1), personally I believe the 500 bhp spec (Stage 11) runs too close to the surge limit on an RB20/25 for my liking. Re boost, you need to remember that boost is simply a measure of restriction to airflow. It is airlfow itself that makes power, boost is pretty much irrelevant. If you remove the restrictions in your engine, then you can make more power at lower boost levels. Noting thta we never simply bolt a turbo on, we always do other things, stuff like this on our R34GTT; GTR fuel pump (SAU forum) 3.5" exhaust ((from Performance Metalcraft) HKS POD with heat shielding and large CAI (SAU forum and self made) R33 GTR standard intercooler (SAU forum) RB25DET turbo with ball bearing hi flow (by GCG) Split dump and engine pipe combo (from Performance Metalcraft) Hi flow cat (SAU forum) Power FC with boost control kit (Nengun) Tomei Poncams 256 @ 9.2 mm (Nengun) Nismo fuel pressure regulator (Nengun) Tomei Injectors (Nengun) None of the above is any use unless you can get the power down, so; OS Giken twin plate clutch (SAU forum) Plus it has to be reliable; Oil cooler and remote filter (Earls) It has more power EVERYWHERE than standard, so it has awesome average power. It gets driven everyday, does some circuit work and the odd drag strip (11.9@120 mph) and has been for almost 2 years. So, at ~1.4 bar, it doesn't run a lot of boost compared to what I see others running for less power. Hope that answered your questions.

Not for me. :angel: After the new cams go in, I set the CAS position using a timing light. If I then retard the exhaust camshaft, I reset the CAS so the ignition timing is where it was when I tuned it last time. You generally have to play with the static timing a little anyway to achieve the best average power. But you're right, anyone who does it by lining up their marks on the CAS body will have a problem.

Mmmm, :confused: in order for the compressor map to be usefull it has to show the weight of air over time. Otherwise the atmospheric pressure (eg; at altitude) will effect the map. As air becomes less dense, it weighs less and this is directly proportional to the power able to be produced from that amount of air. It is not the volume of air, but its weight that is important. That's why the usual (US) compressor maps are in lbs per minute. To make that map usefull you would have to convert the volume measurement into a calculated weight, say at sea level. That would work OK, as long as that is what they used in arriving at the map in the first place. :headspin:

Kg's per sec maybe? That ends up at ~400 bhp, does that sound right for a TD06-20G?

This is the style of catch can we use. http://www.gcg.com.au/catalogue/Oil%20Filt...tor%20round.jpg It has the 4 fittings; *2 inlets on the side at the top (we run a piece of pipe to the bottom and then cover them with stainless steel wool, inserted via the large air filter fitting.) *1 drain (outlet) at the bottom (we put a tap on this, so we can open it and drain it) *1 filter on the top