TimZ

In general, this will reduce any oversteer tendency, not just power-on. The stiffer rear springs in this case should help, but overall that sounds like an understeer combination.

Mat73GNZ has it right. In order to prevent bucking when traversing bumps, the rear needs to be stiffer than the front (i.e., higher natural frequency). So in effect, when you drive over a bump, the front of the car rises more slowly than the rear. Ideally, the entire car rises from the bump at the same time, instead of the front pitching up and then the rear (bucking). If the rear rises first the effect is much less annoying. The spread in spring rates (actually it's the spread in natural frequencies, but John stipulated a 50/50 weight distribution so it works out the same in this case) determines the threshold speed below which bucking will occur. The larger the spread, the lower the speed.

I'm not convinced that it's really effective, but I would imagine the reason for increasing the intake duration is the same as always - to move the torque peak higher in the rpm range. It's just a balancing act to keep the exhaust reversion to a minimum, and try to move the torque peak to a higher rpm.

My favorite part is the silver-painted plywood wing.

Okay, perhaps I was reading more into the original post than I should have, but staying with cast pistons implies "on a budget", which implies not being able to afford the kinds of things required to run 23-25 psi without detonation on pump gas. Also, the questions being asked led me to believe that the experience level was low. Nothing wrong with that - everybody is inexperienced to start off. But inexperience generally leads to some mistakes being made on the way to gaining experience. The margin for error at those boost levels with the stock cast pistons is pretty thin. Yes, if you never detonate, they probably won't break, but I seriously doubt that a first-timer is going to have much luck avoiding detonation on his way to 11 second quarter mile times. When you consider the time, money and trouble required to pull the motor and replace a set of broken cast pistons just once, the forged ones don't look so expensive. I'll stick with my recommendation, thank you very much.

This is true for supercharged engines (which I would guess that Crane is more used to supplying cams for), but in most streetable turbocharged applications, the exhaust manifold pressure is higher than the intake manifold pressure. Reversion is the problem with long overlap periods and turbos, not blow-through.

Reliably? I doubt that. Is there anybody here that is truly running that kind of boost on cast pistons that is still on their first set? Personally, I wouldn't recommend running much more than 12psi on the stock cast pistons.

Ferarri does it because it make more power, not because it's cheaper. As already mentioned, the even firing pulses per bank make it easier to make efficient headers.

No, it wouldn't. The amount of fuel/air in the combustion chamber is dependent on the swept volume of the cylinder and the manifold pressure, not the combustion chamber volume. It just doesn't get compressed as much with the larger chamber. (John - I'm guessing that you misread the original statement)

Once again, this could have been due to any number of factors. It could have been as simple as the shape of the dome, and the way it matched the shape of the combustion chamber. Turbo cars do not run domed pistons. At least mine doesn't. My guess is that the 'detonation-proof-ness' factor came simply from the lower compression afforded by the larger chamber volume. One additional thing, just to muddy the waters further, is that the closed chamber design also leaves the edge of the chamber exposed, since it is smaller than the bore size, where the open chamber does not. Sharp edges are bad for detonation.

Man - I tried to warn you guys, but you just couldn't leave it alone... So, if I could recap - after 30-some posts (this time around), we have definitively proven beyond the shadow of a doubt that a highly modified P- or N- series head might, in certain circumstances, make more power than a highly modified N- or P- series head, when installed on the exact same, or possibly a completly different, engine. About this there can be no question. Wow. We are a font of knowledge. I do have one thing new to add/ask - what exactly is the "theory" behind the N42 being more detonation-prone? I run a mildly modified N42 on my car, and this has not been an issue for me.

Oh Jeez. Here we go ... Do a search on this subject - I don't want to go into this again, unless some new info comes up...

Stopped counting a long, long time ago. Sorry.

If you are talking about the limitations of the cast pistons, then I agree. However, my gut feeling is that the cast turbo pistons aren't really much better. Ring lands are still the weak link. As far as the block itself, I'm running an N42 block and head (ported head, and forged pistons, of course), and have had no block-related problems, FWIW. Ditto on the intercooler.

Heh Heh Heh...Good luck with that...

This is the way to go for driveshaft bolts. (Pete never half-asses anything ) Grade 8 bolts are designed for strength in tension, and as I recall, aren't the best thing to use for shear. Actually, I seem to recall Grade 5 being stronger in shear than Grade 8, but I'd have to confirm that. If you don't like the idea of the Mil Spec pieces, why not just call Courtesy Nissan, and get the actual driveshaft bolts, nuts and washers? They are shear-type bolts, and are designed for the application. BTW, the bolts in the driveshaft flange are in single shear, not double shear. Single shear is more stressful on the fastener.

Yes, I know people have put calculators out there to generate numbers for this, but they are not based on sound theory, given the physics of the Otto cycle (this is the thermodynamic principle that your 4-stroke engine is based on). The calculator that you linked to is flawed in this respect, and also in the fact that it does not consider RPM at all. Probably useful for calculating cylinder pressure at cranking so that you know what your compression gauge should read during a compression check, but not very useful for much else, IMHO. ...Can you tell this is a pet peeve of mine?

Sorry James, but it isn't dynamic compression ratio, either. Dynamic compression ratio only deals with the effect that the valve timing/intake tuning/etc has on the engine's ability to fill the cylinder at a given rpm (i.e, volumetric efficiency, which also is independent of boost, no matter what people might say). For instance, a long overlap cam will generally give low dynamic compression at low rpm, because there is time for the fuel/air charge to leak back out before the intake valve closes. Therefore, the effective volume at low rpm is less at the beginning of the compression stroke, which results in a lower dynamic CR. At high rpm, there is no time for this to happen, so the dynamic compression is higher. Strictly speaking, compression ratio specifically deals with the efficiency of the combustion cycle, and can only add so much. Static CR is defined as the volume at the bottom of the stroke divided by the volume at the top of the stroke. Dynamic CR is the effective volume at the beginning of the compression stroke divided by the volume at the top. The difference between Dynamic and Static CR is that Dynamic CR changes with RPM, and Static does not. Boost pressure will not change these relationships. Boost pressure deals with the amount of fuel/air that is combusted. Nathan has it correct - the detonation problem is due to the tempurature rise during the compression stroke. The temperature at the end of the compression stroke depends on two things - the temperature of the fuel/air charge at the beginning of the stroke, and the compression ratio. Basically, the temp rise due to CR is added to the starting temp. If the end temperature is high enough to ignite the fuel/air charge, then detonation occurs Hopefully it's becoming clear that the turbo effects the starting temperature only. If you have a very efficient intercooler, you can do a pretty effective job of controlling this (at least to a far greater extent that you can with cr). Sorry to launch a big diatribe on this - seems like I'm making this post about once every year or so...

I think it comes down (as always) to what your intended use is. There is absolutely nothing wrong with using Nitrous for drag racing at the track. In fact, it makes perfect sense there. On the street, legality issues aside, it might still be acceptable, but less so, as you might not always have it when you need it. Also, it's only useful for drag racing on the street. If you autocross or roadrace, it is illegal in every class I know of (somebody correct me if I'm wrong), and is pretty much useless, anyway. In a roadrace, it won't last long enough, and in either case, it will make throttle modulation pretty difficult. Finesse is generally more important than sheer power for these choices.

What was the reasoning behind using alcohol?

Electromotive quit supporting MAF sensors on the TEC2 for some reason at their "PAFZ" PROM level. As far as I can tell, they have not added it back in for the TEC3. I don't know why, but if I had to guess, I'd say people were having too many problems getting the MAF systems to work right, and E-motive got tired of supporting it. But that's just conjecture on my part. Blkmgk pretty much summed up what I was going to say about the MAF vs. speed density. Really, I've not heard too many good things about using MAF setups on turbo motors - too many complexities in getting the MAF to read reliably, and also possible latency issues, depending on where the sensor is plumbed. Not to mention the well-known problems of vacuum leaks and improperly routed BOVs wreaking havok with your mixture. The market didn't go the other way because it was harder. Also, the MAF setup that the TEC2 used still had a lookup table, and it worked exactly like the speed density - you still had to calibrate it. Assuming you had the hardware working properly, I'd have to guess that the MAF setup was less sensitive to smallish changes, though (like cam timing, for instance).

Find someplace local that does powdercoating, and ask what they use. I know that they can do this, just don't remember what chemicals they use.

...And then the dealer asked him why there was a HOOK HAND attached to the passenger door handle!!!! He was later killed for flashing his headlights at an oncoming car to signal that their headlights were off (well-known gang initiation ritual urban legend)

Yes, water injection has been known to be effective for years. This is all well and good at the track, and it's perfectly acceptable to use it there. On the street, you'd best pray that you don't run out of water. That race gas will start looking pretty cheap about then... This is the biggest reason that you don't see water injection on more applications - it's not a robust system, and it's failure modes are pretty catastrophic. Period. A couple of other points... Water has a much higher specific heat than alcohol, which means that the alcohol actually reduces the amount of heat gets taken out of the system. As was mentioned, the alcohol is generally required to keep the water from freezing. Now I've seen some claims about the water-alcohol mix making more power, too. This I don't have a good explanation for, although there are many variables that could be responsible for this. Assuming that the engine had proper fuel delivery and a stoich or richer mixture to begin with, there should not be any oxygen left over to burn the alcohol, so it should not give an increase in power over pure water. If the mixture was lean to begin with, then this might explain the power increase with alcohol added. Sorry guys, but this particular case smells like a crutch to me - and a dangerous one at that.

This brings up a good point - my personal feeling is that most head gasket problems are due to improper head torquing and installation problems, rather than the gasket being weak. Lockjaw's post pretty much supports this notion. You should be using at a minimum the turbo head bolts (preferably ARP studs), torqued in the proper sequence to the manufacturer's recommended setting, and only after the engine has been sitting overnight (stone cold). Also, I always re-torque after heat-cycling the engine when the gasket is new. I generally do this three or four times. When I retorque, I always back off the fastener about a quarter turn before re-tightening.