TimZ

Holy Crap - and I thought my gt42 was big:shock: ...and it spins BACKWARDS! maybe you could mount it with the compressor inlet facing the firewall and pull air from the cowl.

I don't think that crank position is going to be enough. If your engine (what engine was it again, all I remember seeing was that it was a v6) ever came with sequential fuell injection/ignition, you might be able to find a cam angle sensor for it.

Yes, that's right - you'll need some sort of cam position sensor so that you can tell whether you are on compression or exhaust at #1tdc. For my L6, I went out and got a stock electronic distributor and modified it for this purpose. Basically, I eliminated the vacuum and mechanical advance mechanisms, and ground off 5 of the six trigger teeth, leaving just the one for #1.

Okay - better packaging makes sense. I really didn't mean to make that big a deal out of it - I was just concerned that it sounded like maybe you were going to a lot of work for a performance gain that wouldn't materialize in the way you expected. Phantom pointed out that you will get better failure modes, and also, you will probably get a bit stronger spark since you don't have to pull it through two spark gaps. The dwell time advantage just won't be there unless you implement the sequencer that you spoke of.

I should clarify this - I meant to say that this would not have an advantage over the 3 coil waste spark setup. Sorry if I offended anybody - should have worded it better.

No - that was my point. He said he was still setting up the 6 coils in waste spark, which means they will still be firing at the same rate as three coils (every 360 degrees), there will just be twice as many of them (coils, that is). I understand why you would want to go to coil per plug, but this setup would not reap any of the advantages.

I guess the way I read that was that he was going from 3 coils in waste spark to six coils, but also in waste spark. So, even though there is now 1 coil per cylinder, each of them still fires once every 360 deg of crank rotation, so there would be no advantage in dwell time, wiring, EMI or packaging. That's why I said I must be missing something.

I must be missing something - what is the advantage to doing this?

I completely agree. One question though - 81 lb-ft with ARP Moly? Yikes, that sounds high - ARP's recommendation with the head studs for my Z was somewhere around 50 lb-ft with moly. Were these bolts or studs? ARP seems to have modified their specs a few times, so it wouldn't surprise me that much, but ususally the spec is based on the size of the stud - maybe the DSM is 12mm? If these were bolts (you did _say_ bolts, after all) then that probably makes more sense, but it still sounds high with moly - probably equivalent to ~100 lb-ft with engine oil.

All true, but whether a wheel fits or not doesn't really tell you anything about the resulting bearing loads. If you change the offset, you've changed the distribution of the loads between the inner and outer bearings.

I think you misunderstood. Offset doesn't tell you anything about fitment on a particular vehicle without width, but it tells you exactly where the center of force from the contact patch (and hence the resulting bearing loads) is. You don't need to know the width for this - in fact, it doesn't really matter. All that stuff about whether the spokes are curved, etc are red herrings. That stuff can effect the caliper clearance, but the offset is the offset, and that is just the distance from the wheel centerline to the mounting face.

True - sort of. Actually, it's not the backspacing per se, but the amount that the backspacing differs from stock. Generally speaking, the inner and outer bearings are designed and sized to handle loads resulting from a given center of force from the contact patch. If you change the offset (offset is a better way to talk about this) appreciably, you can dramatically change the forces that the bearings see.

Although I like the idea of getting the intake up and away from the exhaust heat, I see two problems here, if you plan on using those runners... first, the manifold is backwards second, I think that those runners would put the manifold way too high - the whole thing would stick through the hood. Of course the simple solution would be to sh1tcan those runners and make your own, but they would have to be pretty much straight, instead of the cool u-bends in the pics.

Before I make anybody mad, I did not intend for this to imply that Dr. Hunt was plagerizing - it was clear to me that he included that as a reference. What I did mean to imply was that seeing this same definition in so many different places kind of made me wonder about it's validity - did anybody see Steven Colbert editing Wikipedia to help out the elephant population?

Tony - I actually started to make that exact same post regarding VE of the engine not changing while under boost, and I completely agree with you. Unfortunately, when I looked around the 'net for supporting material, all I found was the same definition that Dr. Hunt posted - actually, that exact definition is posted word for word on about 20 different websites - not sure who posted it first, but there sure is a lot of plagerism going on out there. I decided to let it go, since it wasn't germaine to the conversation. But now that you mention it... It all depends on where you want to draw your system boundaries. The Wikipedia (et al) definition draws it around the entire engine/supercharger. However, I've never been convinced that this is a useful thing to do. You need to consider how you might use the measurement of VE. For instance, if you are trying to create a fuel map for your EFI system, it makes much more sense to think of the VE of the engine seperately from the turbo. The VE of the engine itself is pretty well understood, and is repeatable (i.e., at X manifold pressure and Y RPM, the VE is Z - correct for temperature, and I know how much fuel to put in). If you try to lump the turbo/intercooler into this, it becomes very messy very quickly, to the point that it is no longer useable. On the boost compression thing, I would still take issue where you mentioned that in your example the "total compression ratio is 14:1" - it isn't. Don't give in so easily. For the purposes of this conversation, "compression ratio" refers to the compression ratio of the thermodynamic cycle (in this case, the Otto cycle). The compression resulting from the turbo/superchager is not part of this cycle, and can only influence it's initial conditions (i.e., the starting temperature), not the cycle itself. This is fundamentally why the "boost compression" idea doesn't work. Actually, now that I'm thinking about it, it's also a pretty good argument for keeping it out of the VE calculations, too.

Ditto.

Agreed - I get so sick of seeing the "Boost Compression" myth perpetuated in various web calculators. All they are doing is multiplying your CR by the boost ratio - which gives a number that has no grounding in the underlying physics. Boost pressure has an effect on your tendency to detonate, but not in the way that this implies. Your CR dictates the temperature increase that occurs during the compression cycle (among other things). Basically, the temperature delta is directly proportional to the end cylinder volume divided by the starting cylinder volume. This number doesn't change when you run boost. The boost pressure affects the temperature at the beginning of the cycle, not the temperature delta. Since the name of the game is to keep the final temperature from exceeding the point where the air/fuel mix ignites itself, you can see how each can contribute to your tendency to detonate, but they aren't equivalent - there is no "equivalent CR" that corresponds to your boost pressure - this simply has no real meaning. Sorry for the rant - pet peeve. Anyway, what you should take away from this is that it's very valuable to keep your manifold air temps as low as possible, as you were initially guessing (i.e., high quality intercooler, more efficient turbo, etc. will all help)

Do a search on TEP before you spend money with them...

I need to rebuild my booster - I'd prefer to keep the current shell, as I had it powdercoated recently. I've seen a post that referred to a writeup with pics, but I'll be damned if I can find it (plus I need to get back to work now ) Anybody know where to get a rebuild kit for a 78 vacuum booster?

I'm pretty sure they are not the same. As I recall the n/a pump has a pressure relief valve that limits its output pressure to ~50-55psi. The turbo pump has a higher pressure relief point - ~65psi as I recall.

Are you positive that those numbers are at the valve? Wouldn't that result in a cam to rocker clearance of 0.004"I/0.0053"E ? (assuming a 1.5 rocker ratio) Not saying it's wrong, but it does sound pretty darned tight...

Agreed. As others have mentioned the AN side will seal itself. However, you should be sure to use some sort of lubricant on the AN threads to keep the aluminum from galling. I generally use 3-in-1 oil, others use a few drops of motor oil - just be sure you use something suitable for aluminum.

Actually, I'm pretty sure they do.