zguy36

Your temperature differential you speak of occurs in the engine. Cold air comes in mixed with fuel and ignites. This burns making a hot mixture. The piston moves down and the hot combustion gasses expand and cool. This is the transfer of heat energy to mechanical energy. The more transfer of energy you have, the cooler the exhaust resulting. Shake you head all you want, but maybe put your nose back in that book.

I am getting kinda tired of trying to explain all of this to you guys. It really is a simple concept of balancing energy going in and energy going out. Believe what you want to believe, but I want you to know that you are dead wrong. Heat is not a mear byproduct that is inconsequential. Also, you are wrong in your efficiency. Higher efficiency is not obtained with the highest temperature differential, but with the lowest. Heat=energy. If you expel heat from your exhaust, that is lost energy. If an engine were 100% efficient, the exhaust would be the same temperature as it went in. All the heat energy would be converted to mechanical energy. In the sense of a turbocharged engine, the exhaust temperature is decreased as it travels through the turbo. This is energy transferred from heat energy to mechanical energy. It is not as simple as saying, put your turbo in an oven and watch it spin. Yes, the turbo will not spin in an oven and it is sad that you all think that is equivalent to what I am saying. Heat causes changes in volume, and those changes in volume are causing the turbo to spin. Please read up more on your thermodyamic theory before you post erroneous knowledge on a forum.

On the compressor side, it doesn't matter where you mount your turbo. You are still going to get hot air due to the fact you are compressing air.

Most of the heat in the intake is from compressing the air, not from transfer from the exhaust side. In the exhaust, heat makes the air expand. The more volume you run through your turbo.... blah blah, I've said it all before.

Whoa, it has been a while since I have taken a look at this forum. This post has some serious mud slinging going on! Lots of stuff that I want to address, but isn't valid for this post, so I will bite my tounge! I will make on comment on whoever called me a textbook engineer though. I have done most of my learning by experiementing on my Z, not through my textbooks. The textbooks provide supplement and support to what I have learned through practical experience. Back to topic at hand, or close to it. If you are concerned with building boost sooner, there are ways other than tuning as well. I am currently building a divided T4 flange with a dual scroll actuator. I haven't yet decided which turbo I am going to upgrade to, but that will come when my manifold is finished. My idea (nothing new and taken from many factory applications) is to build an actuated dual scroll setup. Using a dual entry turbo, shut off one side under low boost and open under full boost. I should have numbers for differences in spoolup in about six months. This should allow for a larger turbo to be used without as much increased lag time. It could also be used with a small turbo and have nearly zero lag time. I'll post some pics if you are interested. -jeremy-

I am currently running a medium sized Isuzu NPR intercooler and think it is too big. I am running 15psi on a T3/T4 hyrbid. I regularly drive the car hard for half hour stints on back roads and haven't seen any problems with high intake temps. If I pull over and feel the intercooler core, the hot side is almost too hot to touch and the cold side is ambient. Feeling the core, it is only hot for about two inches across then is back to ambient. Big intercoolers look nice, but aren't always a necessity. -jeremy-

I don't really see the problem with having a hot turbocharger under the hood of your car. With proper placement and shielding, it isn't going to cause harm to anything. The STS system is a good system, for those who cannot seem to fit a turbo under their hood. It is however, a less efficient system. Read my post again on the "how to tune for less lag" post and you can see why. There is a given amount of energy in the fuel you burn given off as heat. If you choose to let that heat out without using it, then that is a energy loss. Read up on that thermodynamics link. It is good stuff. -jeremy-

I think your lag problem has everything to do with your tuning. You said that it runs rich under boost, but how rich is rich? I am assuming you don't have an air/fuel gauge, but that might be something you should consider. I am running a T3/T4 hybrid, which should be worse than yours for lag since it has the same turbine with a larger compressor. My exhaust side is the same as the stock 280Z turbo but yet I build boost a bunch faster than you are talking about. I would check your mixtures and see where you are at. -jeremy-

thehelix112, Sorry for taking over your post. I think it is hard to fully grasp the concepts of your question unless the basics are answered. I'll be the first to admit that I don't know the answers to your question, but do think you should play around with your tuning to find out. You are thinking that retarding your timing to get more boost at low RPM might be useful. I would be inclined to think that the power lost from retarding the timing this much would not outweigh the benifit of the extra boost being built. In answer to your question about ocscilating back and forth, yes and no. If you try to do this, make a good note of what your boost is at full throttle through the RPM. If you retard the timing to build boost higher than normal timing would, then bring the timing back when the boost is built, it will drop back to the normal boost curve with normal timing. So say you get full boost at 3000rpm... you retard the timing so you get full boost at 2500 rpm. If you are still at 2500 rpm and you put your timing back to normal, your boost will drop back to normal as well since it is the retarded timing that is making the boost happen. As I said before, I don't think the benifit of the extra boost would outweigh the lost horsepower due to retarded timing. High boost+retarded timing isn't as good as lower boost+regular timing. It wouldn't be too difficult to map this though for a quick check. Just make your timing curve retarded at low to no boost levels with a high throttle opening. Leave the timing values at their normal settings below 85% throttle opening. This way you won't get bad drivability and can still test out the idea. Let me know how it works. -jeremy-

Bernardd, I did a search for the STS system that everyone keeps talking about. After looking at their website, I have a clearer understanding of what is missing here and to help you all understand. From what I saw, the STS system mounts the turbo at the rear of the car in order to reduce heat fatigue on the turbocharger parts and to also reduce heat in the engine compartment. My first response to this is that heat in the turbo is not that bad if properly handled. They showed a picture of a glowing turbo, and that is bad if you shut the engine down without letting it cool, since it burns the oil inside of the cartridge. If you let it cool properly, there will be no problems with oil burning, and this I assumed you all already know. My replies to what STS says will be in normal text and their words will be in bold. Directly from the website of STS: http://www.ststurbo.com/f_a_q Doesn't heat create the velocity in the exhaust gasses to spool the turbo? No, heat doesn't create velocity. Heat creates volume. If you look at any of the physics laws for gasses, you will find that pressure and volume and heat are related. PV=NRT is a popular one, The V isn't for velocity, it is for Volume. All that is said here is 100% correct. In a given turbocharger system, there is a given amount of mass flowing through the system. When the mass flowing through the system is hot, it occupies a larger volume. Pushing a larger volume through the same size nozzle causes a larger velocity through that nozzle. So, if you are running a given mass of exhaust gas through your turbo, the hotter the mass is, the more volume it has, therefore giving rise to a larger velocity through the given nozzle. The turbine housing is what creates the velocity. The scrolling design that reduces the volume of the exhaust chamber as it scrolls around causes the gasses to have to increase in velocity and pressure to maintain the same flow rate. Also 100% correct. The design of a turbine housing takes a larger diameter and necks it down to a smaller diamter, aka a nozzle. As I said before, if you are running a given mass through the nozzle, you want the largest volume to be occupied (by heating the charge) before it enters the nozzle. Hotter gasses have more volume, thus requiring a higher A/R which in effect means that it starts at say 3" and scrolls down to approximately 1". Lower temperature gasses are denser and have less volume, so they require a lower A/R housing which would start at the same 3" volume, as the turbine housings use standard flanges, and scroll down to say 3/4". Also 100% true Now if you were to reverse the housings in application, the conventional turbo would spool up extremely quick, at say around 1500 rpm but would cause too much backpressure at higher rpms because the higher volume of gas couldn't squeeze through the 3/4" hole without requiring a lot of pressure to force it through. On the reverse side, the remote mounted turbo with its cooler denser gasses, wouldn't spool up till say around 4000 rpms but once spooled up would make efficient power because it doesn't require hardly any backpressure to push the lower volume of gas through the larger 1" hole. Also 100% true. The problem is that this company is trying to sell you their product. They have only given you one side of the story to make their product seem much more apealing. Yes, this rear mounted turbo system will increase performance but it won't do it in the most efficient way. They are not accounting for the energy lost from the exhaust as it cools before it gets to their turbos. Lets start from the basics. The compressor in a turbo requires X amount energy to give you boost. This X amount of energy must come from the turbine in the exhaust flow. All of this energy comes from the expansion of gasses. This happens in the turbo because before the turbine wheel, the gas is very hot (large volume) and pressurized. It enters the turbine housing which is in essence a nozzle restricting the flow. This increases the velocity of the gasses and before it hits the turbine wheel, then expands to a much larger volume (low pressure) after it leaves the wheel. This expansion process increases the volume of the gasses and decreases the temperature. The beauty of a turbine is that it converts this heat energy to kinetic energy. In a conventional system, the air entering the turbo is very hot. Heat is energy, and we must not forget that energy cannot be created or destroyed, but can be wasted. Compared to the STS turbo system, a conventional AR ratio is very large. This means there is less of a restriction in the exhaust. The STS system however, uses a much smaller AR ratio (smaller nozzle). The downside of their system is that all of that heat energy is lost in the piping to the turbo. Remember, that you are burning Y amount of fuel and their is Z amount of energy produced in this process. This burning of fuel creates heat and if you let that heat escape without harnessing it, you are losing potential to use it. To make the turbine spin, there is the a given amount of energy needed. In the conventional system, this energy comes from the heat of the exhaust. If you allows that heat to escape (STS system), then the energy needs to come from somewhere else. This comes from pumping losses in the engine. As the exhaust gas leaves the engine, it is really hot. As it travels towards the rear mounted turbo, it cools down and the pressure drops. To bring this pressure back up, STS uses a smaller AR ratio (small nozzle) to bring the pressure back up. This pressure energy has to come from somewhere and it comes from pumping losses in the engine. On the exhaust stroke of the engine, more energy is required of the pistons to push the exhaust out. Energy is not free, cannot be created or destroyed. It is your choice as to whether or not you want to use what is already given to you. If you have any more questions or need more clarification on something, please ask. -jeremy-

Haha.... you beat me to the punch! I was still typing before I saw what you said. -jeremy-

Clifton, "If you shut your ignition off with your foot in it obviously it will obviously loose spool. Cylinder pressure under load is over 1000 psi. That's alot of volume that is lost. " An engine is a constant displacement pump. If you shut down the ignition, the engine is still turning and therefore still drawing in air and pumping it out the exhaust. Yes, the cylinder pressures do indeed drop, but that is not because of a loss of airflow. Cylinder pressures drop because there is no combustion (heat creation) in the cylinder chamber. Cylinder pressures w/o combustion are ~150-200psi and with combustion ~500-1500psi depending on throttle opening and boost. The only difference is boost comes from the amount of heat that is being ejected through the exhaust. With ignition off, you still are pumping the same amount of air, just the air is cold. You get no boost. With ignition on, you are pumping the same amount of hot air and you get your turbo to spool up. You are correct in that it does take an amount of air to spool the turbo, but that air must also be hot. Remember that work is being done by the turbo and must come from somewhere. The compressor side of compressing the exact same amount of air as is being released through the exhaust side. What goes in must come out. This is not theory, it is the laws of conservation of mass an energy. If it was mearly air velocity driving the turbo, then the same amount of power would be transmitted to the turbine as the compressor would consume to pressurize the intake. That assumed a 100% efficient thermodynamic cycle, which is not the case. The extra energy comes from the temperature difference between the inlet to the turbine and the outlet of the turbine. If you still do not understand, I can reference some thermo equations and diagrams to help. I am at work now and do not have access to my thermo book. (I am a mechanical engineer) Now for the question at hand originally posted here. How to tune for best spool. Since you engine is constant displacement, you cannot really change how much air is being pumped unless you make changes to the engine itself to improve volumentric efficiency. If you are just trying to tune the engine, this is not what you are striving for. If you want the turbo to spool the fastest, tune the engine how you would normally tune. Any changes that would make a turbo spool faster would be outweighed by how poorly your engine runs as the result. For example, anti lag systems. These are great for off throttle, but not what you want during full throttle. Systems that retard timing and richen fuel mixtures to the point of constant backfire will spool the turbo. In this case, you are burning tons of fuel in the exhaust just before the turbo in essence making a jet engine out of it. When this is going on though, the engine is not making power, just building boost. That is the beauty of the system because it builds boost on decel, when you would normally lose boost pressure, then switches back to normal fuel and timing curves when power is required again. Anyway, I hope some of that helps.

Clifton, I must say that your theory on boost could not be any more incorrect. The amount of air flow does indeed create more boost, but it is the heat that is the main driving factor. As the hot exhaust air goes from high pressure (before turbo) to low pressure (after turbo) it is much cooler. This change in energy is what is transfered through the turbine. Simple thermodynamics and turbine theory. A quick way to prove this... take you car up to fourth gear, build full boost. While you foot is still in the throttle (don't let up) reach out and turn your ignition off. Your boost will drastically drop even though your engine is still pumping just as much air as before. The way to tune for fast building boost is the same way to tune for power. Correct air/fuel ratios and proper ignition advance for power is also correct for building boost quickly. These values are dependent on your setup and how much boost you are running. -jeremy-

The advantage of a stud/nut combo is clear over that of a regular bolt. Much of the torque of a bolt is lost due to the friction of turning the entire fastener (more thread surface in block) and therefore less clamping force is translated holding the two pieces together. Both setups are equally strong, just the stud/nut combo clamps the parts tighter together. -jeremy-

Making the nissan emblems for the toyota calipers wasn't too tough. I ground off most of the center fin (not too much, or you'll grind through to the fluid passage) and then cut out the letters from 1/8" aluminum plate with a scroll saw and glue them down with JB weld, then paint. -jeremy-

If you don't like the Z32 calipers but do like the looks, you could do this with your toyota calipers

I feel like an idiot for no thinking of this first before even putting up a post. The problem has nothing to do with the brakes. As I said before, all new parts, nothing broken. The prop. valve is out of the question since only one of the front lines goes through the valve and the line that does go through the valve has too much braking force. Prop valves limit rear pressure anyway. So actual problem Misadjusted coilovers. I didn't notice this problem before since I usually drove with a heavy (250lb) passenger. He evened out the weight distribution. solution Adjust the passenger side coilover to apply more weight on that wheel, until braking is even.

The entire setup is all brand new. I would be able to feel a warped rotor in the pedal (ie, pulsation or steering wheel shimmy) Go out and stomp on your brakes and see if you have this problem as well.

Calipers are all brand new. I had this same problem with the stock setup as well (different calipers, same problem)

I am wondering if anyone else has this problem. Car info is: '73 240z, 280zxt motor toyota front brake upgrade 280zx rear upgrade The passenger side front tire is the first to lock up causing very uneven braking. Is this due to a poor weight distribution in the front of the car. The intake, exhaust, turbo, driver are all on the same side which seems like it would be much heavier than the passenger side and to be causing me this problem. -jeremy-

I saw the 42% duty cycle firsthand. I did not believe it either, so I double checked it on a friends car. He has a haltech and pulled up his duty cycles on the laptop. My meter was right on with the readings the haltech was showing. I have even verified this 42% on a running vehicle, 6500rpm, 12 lbs boost. -jeremy-

I do not think that you would get anything useful out of adding a resistor to the afm circuit. The ecu will only trigger the injectors up to 42% duty cycle, and adding more resistance will not increase the maximum output of the injectors. Leaving the system as it is will provide correct fuel input up to the maximum of 42%. If you want to tweak your afm, you need bigger injectors and tighten the afm. -jeremy-

I put up a post asking about injector firing sequences, but didn't get many replies. The reason I wanted to know the firing sequence of stock injectors is because I had an idea to increase fuel flow with smaller injectors. Yes, I did say smaller. I hooked up my meter to measure duty cycle for the injectors and the duty cycle maxes out at 42% I found this to be quite weak, but that is with a good AFM wide open. I thought that if the injectors fire in two batches, to rewire them so that when a signal is sent out to fire the injectors, that it fires all six instead of only three. This would double the fuel input, since it would be firing twice as often. The stock injectors are 2.2 ohm and higher inpedence injectors would be needed to account for running six injectors on the driver instead of three. For 19# injectors have a much higher impedance and would not overload the driver. I did not find a schematic of the L-jetronic for the turbo 280zx ('83), but every other schematic I found showed that the injectors are fired in groups of two. This could still work with wiring the driver to fire four injectors instead of 2, but diodes would be needed.. Has anyone else thought of this, or tried this? -jeremy-

The reason I wanted to know the firing sequence of stock injectors is because I had an idea to increase fuel flow with smaller injectors. Yes, I did say smaller. I hooked up my meter to measure duty cycle for the injectors and the duty cycle maxes out at 42% I found this to be quite weak, but that is with a good AFM wide open. I thought that if the injectors fire in two batches, to rewire them so that when a signal is sent out to fire the injectors, that it fires all six instead of only three. This would double the fuel input, since it would be firing twice as often. The stock injectors are 2.2 ohm and higher inpedence injectors would be needed to account for running six injectors on the driver instead of three. For 19# injectors have a much higher impedance and would not overload the driver. I did not find a schematic of the L-jetronic for the turbo 280zx ('83), but every other schematic I found showed that the injectors are fired in groups of two. This could still work with wiring the driver to fire four injectors instead of 2, but diodes would be needed.. Has anyone else thought of this, or tried this? -jeremy-