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Edge

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Posts posted by Edge

    Turbo Flow And Pressures

    in Forced Induction Performance

    Posted

    yep dicopotato03 - I was talking about the compressor wheel outer edges going supersonic or what ever you want to call it. Are you trying to say it is caused by physical vibration or something - what do you mean by mechanical speed limit? As far as I know it can spin even faster such as mach 2 for example!

    Bigger compressor wheel outer edge can go supersonic faster. Then cavitation (air compression from air being thrown to the outside) effect is lost and you get back flow of the pressurised air through the compressor blades which is obviously really bad.

    Choice depends on balance of speed and wheel sizes for the amount of air required by the engine, and on whether the engine supplies enough exhaust volume at low rpm to spin a larger turbo's turbine.

    Variable cam shaft in the 2.5L helps to give this.

    Some turbo's attempt to prevent compressor surge through the blades by enabling backflow surge to go around the outside of the compression wheel instead of through it.

    I would think you would have more loss from a small turbo going supersonic as you attempt to acheive higher power than it is designed for.

    As for whether compression in the cylinders is increased due to higher manifold psi now that sounds like it could be the case and is a good question, hope someone can help with an answer.

    It would also make sense for more heat to be generated with higher psi.

    However in general a small turbo should spin up producing boost earlier due to smaller exhaust turbine housing taking same initial air volume = more speed and less pressure due to flow dynamics of circular air flow in a smaller housing.

    The idea that a smaller turbo is better thus has its appeal.

    Turbo Flow And Pressures

    in Forced Induction Performance

    Posted

    What car is this for 2.5L or 2.6L ?

    I've been thinking about this question for a while. (re 2.5L)

    This issue seems to be more to do with terminal velocity at the outer edges of the blades as far as I know.

    If the outer edges of the blades hit terminal velocity you will get compressor surge where the air will backflow through the compressor.

    I'd have to assume that you need to find a BALANCE of compressor to turbine ratios. Then consider the total flow you need for the power level you are looking for.

    The ratio of air flow being the most important issue. So size of turbo not as important other than being small enough to run on the exhaust output and big enough to keep flowing enough air at high rpm to give you constant boost at the level you want.

    Bigger blades represent bigger pipes = more flow. More flow capability means more total air supply.

    I would expect the terminal velocity to be hit earlier on big blades so better to run these with lower speed.

    The thing is that this does not necessarily mean lower boost.

    While bigger pipes represents more turbo lag as more volume to boost up.

    Bigger turbines may make boost come on later. But bigger compressors will make boost come on earlier.

    The smaller turbine side is usually better for bringing the boost on earlier and doesn't really restrict exhaust flow as the wastegate gives way once it reaches the correct boost.

    it is however limited to the amount of topside.

    The big power can only be acheived with a bigger compressor flow. And to power the compressor you need more direct exhaust onto the turbine. With a bigger turbine, instead of bypassing the turbine though the wastegate more of the exhaust gas will go directly through the turbine.

    In the end though you simply need the exhaust flow to be enough to bring the turbine up to speed sufficient to run the compressor at the output you require. With 2.5L engine we have enough exhaust flow to run bigger turbine side, and along with it can therefore choose bigger compressor.

    If you don't bother increasing the exhaust valve lift at the top of the rpm range you may find a smaller turbo is better,

    while if you set up your engine cams to flow heaps then go for a bigger lower pressure turbo with more flow.

    Directly answering one of your questions. The lower actuated pressure will occur best on smaller turbine, with larger compressor

    However a larger compressor wheel will hit terminal velocity sooner if you use a smaller turbine, meaning less total flow!

    Regarding the question on strain you asked...relevant is pressure as opposed to flow: The capability of the manifold to hold pressure is up to 20 psi without modifying gaskets as far as I know in a skyline.

    As for the internals, on hearsay conrods may go in first 2 years at power output 250rwkw. While 230rwkw is considered safe for your conrods. Not sure any factors influence this other than purely the power strain.

    Now for my own question...

    What is the advantage if any of 6 blades over 5 on the compressor?

    Which To Buy First Plenum Or Exhaust Manifold?

    in Forced Induction Performance

    Posted

    Spoke to GCG

    They make a .70 A/R HKS exhaust replica

    in either 84T or 90T (which is something like 55mm vs 58mm wheels)

    GCG recommended gt3076 (76mm wheel comp side) 90T turbine side

    comes in either internal or external wastegate

    iw good for 450hp flywheel

    for above that they recommended using manifold with ext wastegate

    I asked and they said - if go 84T then go smaller compressor wheel.

    How do you think this replica would compare to the true HKS exhaust housing

    what does the size of the Trim in the exhaust do to the ability to bring on boost early? Is it that the bigger the exhaust wheel (not A/R) the more boost comes on early? Would choosing the smaller 71mm compressor wheel to go with the 90T exhaust wheel get boost on earlier?

    Which To Buy First Plenum Or Exhaust Manifold?

    in Forced Induction Performance

    Posted

    thanks BHDave and discopotato03

    Have to wonder whether the drop off top end above 6500rpm is due to hitting the max flow on the turbine side with the .63 A/R exhaust. ie. supersonic or just too restrictive?

    If I was to get one of those HKS exhaust manifolds would this give better exhaust flow (have 3" exhaust straight through) to get boost on earlier.

    What about the cams, I gather changing these is to help top end, would this be enough to enable rpm to go to 7000 with the .63 A/R turbine or will I need to get a bigger A/R turbine side.

    I'd surely like to see the results of that Mafia setup.

    Which To Buy First Plenum Or Exhaust Manifold?

    in Forced Induction Performance

    Posted · Edited by Edge

    Which should I buy first - a high mount GCG 300rwkw optimised exhaust manifold or a greddy plenum?

    Is the 274rwkw figure that seems to come up so much, due to restriction of the standard exhaust manifold or the standard plenum?

    As far as I can tell the GT30R turbo with a .63 exhaust A/R is going to top out at 6500rpm?

    I want around 300rwkw and a turbo that will give me power to 7000rpm on R33 series 2

    What happens if I go .80 A/R compression side?

    Does bigger A/R on the compression side mean more boost at lower rpm? Or is this a function of the wheel size on the compression side? (I do mean the intake to the plenum)

    Can someone give me turbo trim specs and A/R for something that makes same or better power curve in the low rpm ie below 3800rpm range as well as around 300rwkw up to 7000rpm. What else do I need to consider to get this low rpm power (torque) along with the power above 6500rpm - header mods?

    edit - did some more reading, seems to be the exhaust manifold would be the more restrictive, but is it around the 274rwkw point?

    ECR33 series 2

    will use an adjustable exhaust cam wheel

    Pwrfc Or Microtech?

    in Forced Induction Performance

    Posted

    What about the ltx12 microtech inbuilt boost controller, who has used this? It would be better than using a bleed valve right?

    I guess the ultimate would be a set wastegate spring, but how do you set up a switch to select high/low boost when using say 16psi wastegate spring, I guess the switch would turn on an electronic boost controller? Or could you set two different springs to switch mechanically on the wastegate?

    Pwrfc Or Microtech?

    in Forced Induction Performance

    Posted

    It sounds like from what has been said that the microtech lt12 has more resolution for injectors and can be tuned for fuel economy well. I may take the microtech tuning course now that I know there is one. The self tuning capability was the reason I bought it in the first place, and the fact laptop software came bundled with it.

    recently I had manual conversion and it was simple load tuned with autobox before conversion to manual as it is now. Has not yet been tuned for manual with flat spots evident, getting over 400-420km/tank running somewhere between 14-18 psi standard turbo variable due to the silly bleed valve.

    I think with a proper tune this could work out with amazing fuel economy.

    MY QUESTIONS

    Is the visible knock sensor on power fc really helpful in tuning the car, or is air/fuel ratio using wideband sensor with the microtech a better way to go?

    Can you tune off boost low throttle for 14.7:1 or even 16:1 fuel ratio using the microtech the same as with power fc as I've been told?

    When the microtech sees 0 boost does the tune utilise rpm to determine assumed air flow?

    Can the microtech self tune?

    What is matrix tune?

    4 Channel Temperature Display

    in Group Buys

    Posted

    Do you have the following in stock ready for my order at this time?

    In car display showing

    2 x air temp (0-250), 1 x oil temp (0-250), 1 x exhaust gas temp (0-1000)

    4 x 0-250 thermocouples (want an extra one)

    1 x 0-1000 thermocouple

    5 x 1/8" Brass Compression glands

    Is It Possible To Disable A Turbo?

    in Forced Induction Performance

    Posted

    yes it does. if you accelerate at half throttle, but still at full boost the throttle body is only half open, so less air is going into the motor than at full throttle. when more air goes in, more fuel is dumped in to keep the AFRs right.

    if i drive round town accelerating hard all the time i use much more fuel than just driving casually round.

    the harder you accelerate, the more fuel goes into the motor. you sound like you think that whether at 25% throttle or 100% throttle the same amount of fuel goes into the motor. that isn't true. sure you may have got up to speed in a shorter time by accelerating hard, but you have put more load on the motor, so more fuel goes in. and generally light load mapping is leaner than heavy load, so not only is there less air going into the motor, but the air/fuel ratio is leaner. so should you get to a point where the amount of air going into the motor is the same, the light load mapping will be putting in less fual that the heavy load mapping.

    Maybe, but are you sure its leaner on light load on this car? Does stoichmetric cut in whenever its off boost or just when idling? I am not asking if the meter is utilised but whether it runs stoichmetric off boost as opposed to idle.

    In any case it is my opinion that you make up for the the richer mixture during 100% acceleration by sitting in higher gear off boost for longer.

    Is It Possible To Disable A Turbo?

    in Forced Induction Performance

    Posted

    supraaah - serious answer is that you will not be boosting at all infact you will have negative boost ie. vacuum. at cruise - which is most of the time so you will be just fine in the fuel economy department.

    Also there is very little increase in fuel consumption and a lot more efficiency to be had from using the turbo when you are accelerating.

    If you are wanting fuel economy what counts is how long you can maintain a cruising speed vs accelerating time. So if you drive in a way that you brake less and therefore don't have to accelerate back up to speed you will get more fuel economy. Accelerating hard onto the freeway will not see you use more fuel! What you will get is better power to weight ratio output from your lighter engine which has a turbo instead of a larger and heavier engine.

    Once you drive it, check out the boost guage, this will show the boost negative or positive. Its definately extremely negative when you are cruising.

    Do try to drive when accelerating with the rpm in the powerband where your engine is most efficient ie.over 2200rpm.

    Don't forget the energy is used to get you up to speed and lost in braking. How hard you accelerate so long as you aren't going to brake for a while especially makes almost no difference to the fuel economy.

    So feel free to use that boost to get you up to speed but try to maintain the speed without having to brake. If that means driving slower to make it through all the lights in the city without braking or coming up to a lower speed so when you do brake you don't lose as much energy from your last acceleration thats the way to go for fuel economy.

    H.i.d. Group Buy Australian Seller

    in Group Buys

    Posted · Edited by Edge

    I mean H4 with HID Low and HID High single chamber version, according to the advertising should be $260 right. If so I'm in on this, still thinking about the difference between K - wish I could find out the colour spectrum being put out by these Xenon lights at 4300K or 6000K, Perhaps you can advise which is better for contrast at night, I haven't found a colour spectrum output graph for Xenon discharge yet.

    OK here is a rambling piece to follow, after reading several sources online such as osram, aerovisions, spectra of xenon gas discharge, xenon-bulbs etc.

    5500K between mercury vapour and metal halide, seems to be the best even mix of xenon, metal halides and mercury etc. for the best daylight simulating light at a guess.

    Daylight simulating triphosphor fluorescent tubes made by osrtam are 6000K. Cool Daylight fluorescent tubes are at 4000K. In terms of depth and colour perception at night the higher frequencies seem better, but from my own testing it seems yellow light allows more simple contrast but less detailed contrast. So in terms of being bright enough to take advantage of colour perception and to gain maximum detail and depth perception the 6000K seems to be the best.

    Likely to be more mercury in the bulbs, meaning more pressure and heat in the bulbs at 6000K, is that a good or bad thing for longer life?

    Why does yellow light cut through rain and fog better than white? Since I have seperate fog lights I can get stronger intensity long(higher frequency) wavelengths of light. Also 6000K is said to have a higher circadian value for keeping you awake. It is also more comforatblet o view this light at high intensities, so I have to wonder whether for the same lumens whether it is more comfortable on the eyes to use 4300K lights at night as when you look further away it will appear less weak at the lower intensity reflections, so this is why yellow light seems to be easier to make out simple contrast but gives less detailed contrast, as the eye is used to more yellow light in low light conditions.

    Toward the blue end of the green spectrum the eyes are more sensitive at night, but we are talking about subjects under illumination and this is why yellow end of the green spectrum is giving more depth.

    Under very low light you will be able to see newspaper better in blue end of the spectrum, but see the black tarmac better with more light toward the yellow end of the green spectrum no matter what. Though to see detail such as read newspapers in low light you will be straining in the yellow end of the green spectrum.

    So it is that if the light is brighter then 6000K is better but if the light is softer then 4000K is better even if considering both are "white light ie. containing all colours".

    In conclusion 4300K is the best choice for more natural illumination for a low brightness scenario. While 6000K is best choice for a high brightness scenario.

    Since someone said these bulbs are really bright the 6000K should be better in terms of being the most comfortable for the largest range of distances and produce less eye strain.

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