Links

Looking very.. very.. nice..

SII factory central locking key looks totally different.. has 2 x buttons on it.. unlock.. and lock..

Oh awesome.. Cheers Richard.. wasn't aware of that.. might book one in after some of the guys decide when they want to go!.. Cheers Links

Interesting read here: http://forums.evolutionm.net/archive/index.php/t-141362.html Alright, I found this searching on the internet and found it to be very understanding even for a noob breaking his cherry with tuning...ohh and its not for our car so dont follow the numbers given. By the way.... we have short term, long term if anyone didnt know: The following is a guide to tuning your car with a SAFC, AFC, VPC, AFR, etc. It starts with basic techniques and proceeds to moderately advanced ideas. Enjoy! STEP 1: Setting up the car and the SAFC. Before we begin the guide on how to tune with a SAFC, you must make sure the car is set up correctly to do so. Make sure all the fuel components are in good condition, and make sure you have no boost or vacuum leaks. Also, if you have a 255 lph or larger fuel pump with no adjustable regulator, then either get a new reg or don't try to use the fuel trim techniques outlined below. Second of all, setting up the SAFC. At this point, I will assume that you have it wired in properly, if you do not, there are plenty of directions in the VFAQ. Also, may I suggest that you DO NOT do the "blue wire mod", it has been proven to degenerate the O2 sensor's signal. In the Th-Point section of the SAFC, set the low trigger at 30%, and the high trigger around 80-85%. In the NePoint section, set them to: 1k, 2k, 3k, 4k, 4.5k, 5k, 6k, and 7k,. Now, you want to use baseline corrections for fuel injectors. If you have 450's, leave both tables at zero. If you have 550's, put them around -10%. If you have 660's, usually around -18% would be a fine starting point. If you have a hacked MAS, then you will want to use about 5% MORE than these values. The next section will cover fuel trims, and how to set the low throttle table. STEP 2: Fuel trims and low throttle Before proceeding past this point, you MUST have a logger of some sort!! Once you have the SAFC all set up, you should first start by setting the low throttle points, using the fuel trims. Doing this will require a basic knowledge of fuel trims, so I have outlined them below: The ECU is, in essence, just a big set of spreadsheets (also known as "fuel maps"). It takes input from the MAS (in the form of Hz, temperature, and barometeric pressure) and comes up with a final value that represents the amount of air entering the engine. It also looks at the engine's RPM. With the RPM and an airflow value in mind, the ECU will look to the fuel tables, and find the amount of fuel it should inject into the motor. Then the O2 sensor comes into play. The O2 sensor tells the ECU what the a/f mixture looks like, if it is rich, lean, or right in the middle (stoich.). If the O2 sensor says that the mixture is lean, then the ECU will add a bit more fuel on top of what the tables tell it, until the O2 values get close to stoich. If it has to do this for a certain period of time, it will take note of that in the fuel trims. Example: You are pulling in 30Hz of air at 800 rpm (idle). The ECU looks this up, and decides to inject 2.1 ms of fuel. However, the O2 sensor decides this is not enough. The ECU bumps this up to 2.2 ms, 2.3 ms, and finally 2.4 ms, when the O2 finally says that is perfect. If this keeps happening over a period of time, the ECU will increase the Long Term Fuel Trim to 114%, since 2.4 is 14% more than 2.1. It will, from then on, add 14% more fuel whenever it is in the range of that Fuel trim. 1g: 1g's have 4 fuel trims. The low trim is for idle and low rpm cruise conditions. The middle trim is for medium cruse rpm's (1500-2500ish) and the high fuel trim is for 2500+ rpm. The O2 trim is constantly changing with the O2 sensor, and it is what will cause the Long term fuel trims to change. The approximate airflow ranges for the three trims are: Low: 0-125 Hz Mid: 100-175Hz Hi: 175+ Hz 2g: 2g's only have 2 fuel trims, a long term fuel trim (LTFT) and a short term fuel trim (STFT). The STFT varies with the O2 sensor, an the LTFT goes for every rpm range. Since the STFT directly effects the LTFT, then you can just add the two together, and tune from there. For example, if the LTFT is +20%, and the STFT is -5%, you are at approximately +15%. You can also do this addition trick on a 1g with a TMO/Pocketlogger type setup. Whew, that was exciting, but I think I covered it all. Now, on to the tuning. Set up your logger to display RPM, Airflow, and all the fuel trims your car has. Start the car and let it fully warm up. Leave it at idle, and we will begin to tune the low throttle table in the SAFC. Now, look at the low fuel trim (2g's only have the LTFT). If it is positive, add a few percent on the SAFC at the 1000 rpm point. This is not an exact science, but usually for about every 3-5% on the logger, you need 1% on the SAFC. After adding or subtracting a few percent, let the car idle for a few minutes, and watch the fuel trims change. This may take a while, especially in a 1g, so just wait. When this is done, free rev to 1500 rpm and hold it there. Do the same thing, it will probably still be on the low fuel trim. Continue to do this at 2k, and 3k rpm. After you are done and are fairly confident they are close, take the car for a drive and see if they change. Try to get the fuel trims close to 100%, plus or minus 10% Keep in mind that in a 1g, a perfect fuel trim is 100%, but in a 2g it's 0%.. That means that in a 2g, if the fuel trim is negative, you have to lean it out a bit, and if it's positive, you have to richen it up. Once they are within 5 or 10%, and they have stayed that way for a drive, you can carry the numbers across up to 7k rpm. So, if you have +5% at 3k and 4k rpm, use +5% at 4.5k, 5k, 6k, and 7k. Then, you will also want to use +5% on your high throttle table, all the way across, until we begin to tune it in the next issue. STEP 3: Hi Throttle At this point, I will assume that you have your fuel trims leveled out near 100%, and that they have stayed like that for several days of driving. Also, this assumes that you have used the same correction factor that you used for the higher rpm's of the low table, all the way across the high table. Also, make sure that you have no bad phantom knock, and that your base timing is set correctly to 5 degrees (on a 1g). Now, it's time to do some real tuning. First, set up the logger. You want to make sure to log RPM, knock (if you can), timing advance, and airflow, and not many more. Now, go make a pull. It is best if you can make one in third (or fourth) gear, but if you really have to do second, that might be ok to start. Make sure to go WIDE OPEN from 3k rpm to well above 6k. Also, make sure you have your boost set where you want it, it is actually easier to tune if you set it a few psi BELOW where you want it. Now, save the log, and bring it up. Look at the 3k rpm portion of the graph, at knock and timing. Now you have to decide if, at 3000 rpm, you are rich, lean, or just right. If you are too rich, your O2 values will probably be pretty high (over 1.00v in a 2g, and over .95v in a 1g, approximately) and you will have no knock (although you can have rich knock, but we'll come back to that), and decent timing advance. If you are too lean, then you will have less timing advance, and knock. On a 1g, you want to tune for no knock, end of story. On a 2g, you want to tune for timing advance. You want to keep the timing advance graph on the logger above, say, 15-16 degrees, and you want it to be nice and smooth. So, with that information, decide if the 3000 rpm point is rich, lean, or just right. Then, add or subtract just a couple % of correction, depending on your findings. You want to only do a few percent at a time. Then move on to the 4k rpm point, and do the same thing, looking at the logger. Proceed with this up to 7k, and then make another pull with the logger to see the effects of your changes. This will get easier as you get more experienced, but it's not really that difficult. Tuning: Advanced So, you have mastered the art of getting your fuel trims right at 100%, and you can make nice WOT pulls with no knock and/or good timing advance? You've basically learned all that you need to know to have a car that runs well, but there is a little more to learn if you want run "really really well." This is where you will most benefit not just from my information, but from talking to other members of this board as well. I also ask that guys who have lots of tuning experience (you know who you are) add their input here as well. Timing vs. Airflow Now, while the ECU has tables for the amount of fuel it needs to inject, it also has table for how much timing advance it should give you, and tables for how much it should advance timing depending on knock. For 0-3 counds of knock, the ECU will advance timing. For 4-7 or so counts, it will leave timing where it is, and anything over 7 will result in the ECU bringing the timing down in an attempt to control the detonation. While 2g guys cannot view this knock sum on a logger, it is there, you just have to guess what it is by the behavior of the timing curve. Now, the timing tables in the ECU, just like the fuel maps, are indexed by airflow and rpm. With a SAFC, this has an added effect. Since a SAFC intercepts that signal from the MAS to the ECU and modifies it, it can change the amount of airflow that the ECU "sees." If you have to correct your SAFC into the positive range, than the ECU will see more airflow Hz than the MAF is outputting, and could change the timing map you are following. The problem with this is, higher airflow levels get less timing advance for safety, and lower airflow levels get more timing advance, because the ECU thinks you are pulling in less air. By leaning out the SAFC (big injectors, more fuel pressure, race gas) you decrease the amount of airflow that the ECU sees, and therefore you usually will get a bit more timing advance for power. This all assumes you have no knock, and also keep in mind that more timing advance will have an engine a higher propensity to knock. I have heard of 1g guys with 660 cc/min injectors getting timing advanced as much as 28+ degrees at WOT, because you hve to pull the SAFC correction factors down a lot due to the fact that 660's are 47% bigger than the stock 450's. Fuel Cut Another issue involving the amount of airflow the ECU sees, and the correction factors of the SAFC, is fuel cut. For those of you who do not know, the ECU has a program that tells it to cut fuel when the airflow exceeds a certain amount. Now, this is with the final calculated airflow, not just the Hz signal, which means that temperature and barometeric pressure will effect fuel cut as well. If you are to install, say, 550 cc/min injectors, you will be able to pull the correction factors within the SAFC down about 10%, perhaps more. This means that the ECU will see about 10% less airflow under a given amount of boost than it would have with the stock setup, which makes it much less likely for you to get fuel cut. Obviously from that - by using bigger injectors you can therefore give yourself some leeway on the boost cut.. also - maybe read this: http://www.roadraceengineering.com/newafc.htm Sorry for the extra crap in there.. however it may help someone searching on how to tune SAFC. but also may help you stan with your problem?? possibly.. possibly not..

Abo Bob.. do you know when one for SAU might be happening.. missed the boat on these, thought there might be one in march.. obviously not..

Looking great guys.. like the new choice of styles, couple of new little things.. great job..

SXC180.. please elaborate.. always good to hear both sides.. or maybe your not allowed to say bad things.. only good things

get someone to check in nissan fast.. than ring nissan spare parts and find out what they are..

http://www.carsales.com.au/pls/carsales/...rch_distance=25 http://www.carsales.com.au/pls/carsales/...rch_distance=25 both of those have airbags..

now stop talking in your own threads and go buy it already..

http://www.skylinesaustralia.com/forums/in...howtopic=106193

http://www.skylinesaustralia.com/forums/in...howtopic=106193 do a search..

http://www.skylinesaustralia.com/forums/in...ic=104810&st=20

Congrats welcome to the club..

I think it's got ABS.. you can buy me a drink too if you want.. lol sounds like a good car..

not worth rechipping if it's a SII.. buy an apexi or emanage..

From the sounds of it you probably made 10kw+.. not too bad.. would be interesting to put in a power fc now and see how it goes.. you running a bleed valve? pity you didn't dyno it before..

pity the fool sittin in the back lol.. but apart from that - nice car.. not quite my style, but nice.. will be interested to see what you've done with the motor..

http://www.turbofast.com.au/ another great site with some small apps for calculating different turbo theory's..

http://www.dsm.org/archives/1997/06/19970620.txt/28.html The story so far: We have determined what a turbo is, how the exhaust turbine functions (and what affects its performance) what the inlet compressor is (and what affects its performance) and hinted a little at what selecting a turbo requires. Today: Intercoolers and Wastegates and BOV's - Oh My! So, yesterday we left off with high pressure air leaving the compressoroutlet. Unfortunately, physics has worked against us this time, and theact of doing work to our inlet air to compress it has raised itstemperature. This is bad. Not only are we reducing density, we're increasing the possibility ofthe great bugaboo - detonation. Remember, the onset of detonation isusually the limiting factor on the amount of power a given engine canproduce, and that increased intake temperature (as measured at theintake valve) increases the chance of detonation. So we have to cool the air back down again, without losing any pressure. That's the job of the intercooler, basically a "air radiator" placed inthe flow stream between the turbo compressor outlet and the intakemanifold. There's really not much else to say about them, except: 1) The more you can cool the air flow, the better. This _normally_ meansthe bigger the intercooler, the better. (There are some smaller coolersthat are better designed than the lower-end "big" coolers though, sosize does not necessesarily indicate effectiveness. 2) The cooler must be placed in a location where ambient air can flowthrough it. This means that your cooler must have an intake path and an_exhaust_ path. Mounting a cooler flush against a plate does no good! 3) There's always a pressure drop across a cooler. How much depends onthe cooler design. Wastegates A turbo is a positive-feedback device. The more boost you make, the moreexhaust you make, which makes more exhaust, which makes more boost...in a vicious circle. So we have to have some way of limiting boost. What we _really_ want is a way of keeping the turbine operating at aconstant speed (see yesterday's post) so that we can maximise thecompressor efficiancy - remember that turbines like to run at a singlespeed. However, as measuring turbo RPM is not practical, and as boostlevel is directly related to turbo speed, keeping the boost constant isthe wastegate's job. The wastegate is just a valve that opens when we have exceeded ourdesired boost level, and allows exhaust to flow around the turbine,instead of through it. This lowers the pressure differential across theturbine, less work is done, and the turbo slows down. The only "gotcha" with the wastegate is that it must be able to flowenough gas to let the turbo slow down. If it can't, then you get "boostcreep" where boost levels slowly grow as the car remains under boost.Bad. BOV Everybody likes BOV's because of the nifty sneeze sound they make.However, a BOV is an evil device. It's taking your precious boost andventing it to someplace else. Bad! Unfortunatly, it's a necessary evil, and we have to live with it. Here'swhy:You're under boost, the turbo is fully spooled, and life is good - thenyou shift. That means your foot comes off the gas - and the throttleplate slams shut. Suddenly, instead of flowing in a continuous streamthrough the engine, the intake air smacks into the closed throttleplate. The turbo, which is still spinning and producing boost because ifit's rotational inertia keeps producing pressure, and the intake stream,caught in between a rock and a hard place, jumps in pressure. In fact,you get a high-pressure shockwave that travels from the throttle plateback to the compressor vanes, that once it gets there, is a little likepoking a stick into the spokes of a bike wheel. The repeated shock is hard on the compressor vanes and the shaftbearings, and in any case acts like a brake, slowing the turbo, andrequiring it to be spooled up again. The BOV sits in between the turbo and the throttle plate, and if itdetects the shockwave created by a shift, vents it elsewhere - either toatmosphere, or back to the inlet side of the turbo. So, we lost boost pressure, but we kept the turbo spooled... tough tosay without a dyno if that was a fair trade on a race vehicle. On astreet vehicle, it was definately a good idea, becuase we spared ourexpensive turbo a mechanical shock. That's it for today. Monday: Summing up. DG http://www.dsm.org/archives/1997/06/19970623.txt/4.html But if increasing the pressure of the gases at the turbo inlet (exhaust manifold) will>produce more work, then why is everyone boring out their exhaust manifolds? According>to your post, would this not lower the pressure differential and therefore decrease>the heat and energy transferred to the turbine wheel? Does this mean boring is counter>productive and we should only be polishing it to smooth out flow? Well, that depends. If the exhaust manifold is not flow-limited, then yes, increasing thediameter of the manifold runners is counter productive. If the manifold is flow limited, then increasing the diameter of themanifold runners may do you some (or a lot) of good. The pressure may bea little lower, but now you've got more gas available at the inlet toexpand and do work with. "But you didn't say anything about the amount of gas in your other post"Yeah, I know. It's tough to summarize a mildly complex topic and hit_all_ the points. Part of the problem is that pressures in the system are all very timedependant. That gas coming out of the turbo outlet isn't a steadysource, like a hose, it's a pulse. The pressure at any point in thesystem varies with time, and it's difficult to "nail down" systemperformance in absolute terms. After copping out like that though, let's examine a flow limitedmanifold runner. The pressure in it is higher than in a runner that iscapable of flowing exactly the amount of gas produced, but it won't beable to sustain that pressure as it gets bled off through the turbine,and not enough gas can flow up to the inlet to replace it. Pressurewill drop to the sustainable point - lower than the ideal case. Enlargethe ideal case though, and you've gained nothing - unless you canincrease the production of gas to the point where you're back at idealagain. >What about people who wrap up there downpipes to keep heat in and the exhaust gases>hotter after the turbo. The hotter gases travel faster right, and that decreases>pressure (good)? Or, the higher retained heat keeps the gases hot and the pressure>stays higher and that would lower the pressure differential (bad)? Heh, welcome to the real world. Both are legit ways of examining the problem, and either scenario ispossible, depending on the flow capacity of the exhaust system. If it iscapable of flowing the exhaust, then the retained heat will serve toincrease the velocity, lower the pressure seen at the outlet, increasepressure differential, and increase power. If, however, the systemcannot flow the gas produced, then the retined heat only serves toincrease the pressure seen by the outlet, decrease the pressuredifferential, and reduce power. Theory is a wonderful thing. It lets you gain an understanding of what'sgoing on, allows you to ask meaningful questions, and leads you to trythings in an intelligent manner. Ultimately though, when you starttalking about _specific applications_, there's no substitute for tryingit out and testing it. "will boring out my exhaust manifold make more power?" Well, calculatehow much exhaust gas you should be producing at redline at your desiredboost level, and then put your manifold on a flow bench. Are you flowingenough? What's the current pressure at the turbine inlet? What was itwhen you tried a bored-out manifold? (Here's the kicker) What happenedwhen you put the changed engine on the dyno? Crew chiefs in F1, IndyCar, NASCAR - all these guys have forgotten moretheory than I'll _ever_ know, and they still end up trying stuff out onthe dyno. But trying stuff _without_ knowing the theory is just blindguessing, putting monkeys on the typewriters and hoping for Shakespere. Hope this helps,DG http://www.dsm.org/archives/1997/06/19970623.txt/51.html > Thanks Dennis for your posts. It's great to have someone who has a> background in this stuff share their knowledge. Thanks. For the record though, I don't work in engineering here, I'm anIS weenie. (An IS weenie that's been racing for quite a while, but an ISweenie nevertheless) > I've have a question about forced induction vs. NA. With forced> induction, you have to lower the compression ratio to prevent> preignition. Doesn't that lead to lower thermodynamic efficiency> (when not under full boost, ie, most driving) vs a NA engine, since> the combustion temperatures are lower with the lower compression? In> other words, aren't NA engines more efficient for passenger cars than> forced induction engines? Or does better thermodynamic> efficiency not always translate into better MPG? Wow, ask a simple one, why don't ya?I don't think I'm qualified to give you a _definative_ answer on thisone, but I'll take a stab at it. Firstly, forced induction engines lower the mechanical compression ratioto prevent _detonation_ not preignition. No, I'm not being picky,they're 2 different things, preignition being a premature ignition ofthe mixture due to a hotspot (normally glowing carbon deposits on anexcessively dirty combustion chamber). Preignition is fairly benign assuch things go, detonation can slag your engine. But yes, that lower mechanical compression ratio does reduce the amountof power produced per cubic centimeter of displacement when not runningunder boost, and you're right, most daily operation is not under boostconditions. So that would mean that the NA engine should be moreefficient. However...If I remember correctly, the extra compression didn't make all _that_much difference on its own - 10-15 HP on a Pontiac 6.6l moving up apoint or so. The real benefit that all those 60's muscle motors got outof the extra compression was the ability to run bigger/longer cams. (Ascam duration and lift increases, you need more compression to make useof it, at least on big V8's) Secondly, the turbo motor is much more efficient under boost - and whenyou are under boost, you're accellerating hard and burning more fuel, sothe turbo gains efficiency when it's needed most - so it may make moredifference to overall efficiency. I guess the easiest way to tell is to check the EPA MPG ratings for theFWD 2.0 Turbo Talon and the FWD 2.0 NT Talon, and see how they compare. How's that?DG

I just found this site that I think might help explain some things on how turbo's work.. http://www.dsm.org/menu.epl?item=246 I'll post the articles up: http://www.dsm.org/archives/1997/06/19970617.txt/20.html After a series of discussions on IRC, I've been asked to post a description of my understanding on How Turbos Work to the digest - so here goes: How Turbos Work (or: The Closest Thing to a Free Lunch) Before we start, we have to take a second to review a little grade 10 physics - The Ideal Gas Law. In short, gas temperature, pressure, and volume are all related. Compress a gas (reduce the volume) and pressure and temperature goes up. Let it expand, and temperature and pressure go down. Increase the temperature, and the pressure goes up (in an enclosed space) or the volume goes up (it expands). Finally, gases want to flow from a high pressure area to a low pressure area, and the greater the difference, the bigger the push. (Pop a baloon, little bang. Pop a welding O2 cylinder, big bang) OK, a 4 stroke engine produces work by expanding a gas in a confined space where the high pressures created can push against a piston. Furthermore, that gas is heated by the process of creating it (unlike a steam engine) so you get even higher pressures - and more power. Unfortunately, most of that heat (which is the same as energy) is dumped overboard in the exhaust before we get any chance to use it. It's just not in the cylinder long enough to transfer all that heat into mechanical energy, and it's not practical to make cylinders "tall" enough to extract every last bit of work from that hot expanding gas. So, what can we do about it? well, we can point the tailpipes out the back to try and get some thrust - except that aside from some very rare circumstances, the gas volume isn't high enough to get any worthwhile push. (A few older IndyCars actually created a couple of pounds of thrust from their exhausts, but that's not enough to be really useful) OK, how about sticking some sort of auxillary engine in the exhaust flow? Steam engines did this for years... Enter the turbocharger, a turbine fed by exhaust gasses, connected to a compressor via a shaft that compresses intake air into the engine. More air in the cylinder means more fuel can be burnt per power stroke, more burnt fuel means more hot gas, more hot gas means more power - and more boost too. This is the closest thing to a free lunch you'll find in engineering, because you're taking heat (energy) that would otherwise be wasted and getting usable work out of it, with almost no tradeoffs. You gain a little complexity, and added manufacturing costs, but there is no real performance hit from adding a turbo. "But doesn't the turbo increase exhaust backpressure?" Under boost conditions, no. Here's why: when the exhaust valve opens, the pressure inside the cylinder is much much higher than the pressure at the turbo inlet. That cylinder pressure "blows down" very quickly, but we're on the exhaust stroke - the cylinder volume is decreasing very rapidly, and from the Ideal Gas Law, that tends to keep the cylinder pressure higher than the turbo inlet pressure. Finally, when the exhaust stroke is nearly done, and the pressures are nearly equal, the intake valve opens, the intake pressure (we're under boost here!) "blows down" into the cylinder, and presto! we have a higher cylinder pressure again. (I'll discuss backpressure - I _hate_ that term, it's misleading - in greater detail in a later post) That's enough bandwidth for today. Tomorrow: what goes on at the turbine, and how to make it work better. DG http://www.dsm.org/archives/1997/06/19970618.txt/28.html Allright, yesterday we determined that a turbo was a device that could be used to get useful work out of otherwise wasted energy, to day we'll discuss how that happens in more detail. It is a common misconception that the exhaust turbine half of a turbo is driven purely by the kinetic energy of the exhaust smacking into it (like holding a kid's tow pinwheel behind your tailpipe) While the kinetic energy of the exhaust flow does contribute to the work performed by the turbo, the vast majority of the energy transfered comes from a different source. Keep in mind the relationship between heat, volume, and pressure when we talk about gasses. High heat, high pressure, and low volume are all high energy states, low heat, low pressure, and large volumes are low energy states. So our exhaust pulse exits the cylinder at high temperature and high pressure. It gets merged with other exhaust pulses, and enters the turbine inlet - a very small space. At this point, we have very high pressure and very high heat, so our gas has a very high energy level. As it passes through the diffuser and into the turbine housing, it moves from a small space into a large one. Accordingly, it expands, cools, slows down, and dumps all that energy - into the turbine that we've so cleverly positioned in tho housing so that as the gas expands, it pushes against the turbine blades, causing it to rotate. Presto! We've just recovered some energy from the heat of the exhaust, that otherwise would have been lost. This is a measureable effect: Stick an EGT upstream and downstream of the turbo, and you see a tremendous difference in temperature. So, in real world terms, what does this tell us? All else being equal, _The amount of work that can be done across an exhaust turbine is determined by the pressure differential at the inlet and outlet_ (in english, raise the turbo inlet pressure, lower the outlet pressure, or both, and you make more power) Pressure is heat, heat is pressure. Raising the inlet pressure is possible, but tough. Lowering the outlet pressure is easy - just bolt on a bigger, free flowing exhaust. I've seen a couple of posts from people who added aftermarket exhausts, who report "my turbo spools up faster now" Well, that's because by lowering the outlet pressure, you increased the pressure differential, and now the exhaust gas can expand more, and do more work. That increased work pushes harder on your turbo, and it spools up faster. You should also see less boost drop at redline, because if an exhaust system is flow-limited, once you pass the flow limit of the system, any additional gasses you try and force through it only raise the outlet pressure. Higher outlet pressure, lower pressure differential, less work, less boost. [note that the compressor side comes into play here too - that's another post DG] That covers Turbine Theory. Tomorrow - the Compressor Side. DG http://www.dsm.org/archives/1997/06/19970619.txt/21.html Having covered what a turbo is, and how the exhaust turbine works, we now turn our attention to the compressor side of the turbo. (If you thought yesterday's post was a little verbose, just wait 'till you see this one If you can extract work from an expanding gas via a turbine, then it stands to reason that you can compress a gas by driving the turbine shaft with a power source. In other words, the compressor side is just the turbine side driven backwards. The exact same physical lays apply, just now in reverse: we take a low pressure, low temperature gas, do work on it with the compressor vanes, and get a high pressure, high temperature gas at the outlet. That temperature increase is unfortunate, and will cause us problems later on - and we''l come back to it in a bit. While the turbine and compressor sides of the turbo are essentially the same, they are _not_ mirror images of each other, and the reason why is due to the chemistry of combustion. A given volume of air will burn an exact amount of fuel, in a ratio of air:fuel about 14:1. The volume of exhaust produced is much greater than the volume of the air used to create it, and the resulting exhaust pressure is much higher than the boost pressure will ever be, so the wheel and housing designs are completely different. Which leads us to turbine/compressor design. Turbines are wonderful devices. They are light, and _very_ efficient, but they also tend to suffer from a limited RPM range. That is, a turbine/compressor is very efficient at a certain RPM/flow capacity, but if you vary the shaft RPM very much, the efficiency drops. Run too fast, and the turbine blades cavitate and (aerodynamically) stall, and flow drops. Run too slow, and the blades aren't getting enough "bite", and flow drops. Here's an example. The M1A1 Abrams tank weighs about 55 tons, most of it in armour. (Steel and depleted uranium) It has a gas turbine engine that produces 1800HP at the wheels... er, tracks, which is enough power to move that beast at about 70 MPH. The turbine is amazingly small, and while I don't remember exactly how much it weighs, it seems to me that it's on the order of 300-500lbs. Compared to the weight of the rest of the tank, the engine might as well not be there! However, the design of the turbine was optimised for WOT operation. At WOT, the turbine gets better gas milage than an equivelent diesel at the same power point, but at idle, the turbine efficiancy drops, to the point where gas milage (per minute of operation) is **lower** at idle than it is at WOT! Turbines are fantasic powerplants for vehicles that can run at a constant RPM all day - like tanks, boats, airplanes, IndyCars, etc. For vehicles that need to be run at different engine speeds, they don't work so well. (although if somebody invents a good infinately-variable-ratio transmission, look out!) So, getting back to turbochargers, what does this mean? Well, a turbo is really a single speed device. We're only producing enough exhaust to generate boost at WOT, and we have boost-limiting devices to keep the turbo running at a constant speed (once it gets there) so, if we know how much boost we want to produce at WOT, and we know how much air we are consuming at WOT and full boost, then we can select a turbo (really, we're selecting a compressor wheel and housing combo) to maximise the turbine efficiency at that flow point. Well what does _that_ get us? A smaller turbo. That is better, because the smaller the turbo, the less rotational inertia you have to overcome, and the faster the turbo accelerates to it's WOT speed (and the associated boost level) The time delay between opening the throttle and the production of full boost is commonly referred to as "turbo lag" and is the single most hated "feature" of turbos. Ever wonder why the turbo on the 2G is so small? It's been exactly matched to the air consumption of the engine for the driving style of Joe Public - who rarely, if ever, exceeds 4500RPM. Reducing lag has another important side effect though. If you have a datalogger, and plot the boost curve of your vehicle, the area under that curve determines your transitional power band. Do a litle calculus, and you find that increasing that area - even without increasing the peak boost point - increases the torque available to accelerate the car by a large amount. One of these days, one of our tuner guys is going to get a flow bench, and a dyno, and work out the air consumption of his motor at a certain boost point, and select a compressor wheel and housing combo that maximises efficiency at that point (describing how is beyond the scope of this post - in a nutshell, you compare pressure maps) and go really, really fast. If the tranny stays together. Tomorrow: Wastegates and Intercoolers and BOV's - Oh My! DG

yeah I think Busky2k & BHDave have a good point.. http://www.gnttype.org/techarea/turbo/turboflow.html some interesting reading/maths... lol it's all about how much air flow there is.. don't forget the more boost, the more positive air being pushed into the engine, the more air, more boost, so quicker a turbo spools up.. I think the speed is probably exponantial as well.. in fact this whole page has some great stuff http://www.gnttype.org/techarea/turbo/turbopage.html

The higher the load, the more fuel being injected to match the air flow, the more airflow, the more exhaust gas.. the faster the turbo spools up..

rip off - they took the nismo stickers off the bonnet and the boot

Think he was saying he wholesales them for 45k than they are about 55k retail..