TimZ

ACE1 - Manifold Absolute Pressure Rate Sensitivity None of the enrichments get triggered until the MAP value increases at a rate higher than this setting. ACE4 is how long the variable rate enrichment lasts. So once triggered, you have two different types of enrichment that get added together - a fixed one second enrichment that is currently set to 10%, and a varible enrichment that, as I recall (i.e., double check the manual), starts at your setting (50%) and ramps to zero over the time period you have set (0.5 sec).

No problem -whatever works for you...

It would be helpful if you could supply a TEC3 datalog of this same type of situation (doesn't have to be the same run, but it would be nice if it was). I need to see the map signal and the gama (total fpw in TEC3 speak), along with rpm and maybe the coolant temperatures. In general, I'm suspicious of the pressure rate sensitivity - if it's too low, the enrichments won't get triggered. You can try lowering that value, but it would be best to see what is going on and make a more informed decision instead of guessing.

Thank Pete Paraska - he did the writeup...

If you don't have a TPS, you can still get some acceleration enrichment under these circumstances by using the MAP rate of change enrichment instead - that's one of the reasons it's there for...

That sounds about right... http://home.comcast.net/~pparaska/gagecalibration.htm

As I recall, James put a step in the bushings to help limit the leakage, and the rest is just clearances. Leakage has never seemed to be much of a problem, really. I have it apart right now, and I'm not seeing any burn marks around the bushings or anything.

This was most likely part of the block machining process - the oil galley was created by boring a long hole through the block in a precise location. In order for it to work, the ends of the galley have to be plugged, else the oil would just bleed out either end, as others have stated. The plugs also allow you to clean out the galley during a rebuild. You can't leave them out, though.

That's looking really good, Rob - nice work!

Wierdness with the way the dyno software back-calculated the torque from horsepower and rpm, maybe?

I thought about that too, but the rod ends, while not offering any damping/noise reduction, would still allow some amount of twist, so I don't think you'd run into the normal problem of having hard mounts on one end and soft on the other. You'd probably want to check the geometry to make sure that you don't allow too much twist, though...

It's not really that far off topic, as it pertains to manufacturability of Rob's diff mount/subframe. Manufacturers don't genrerally hold the position of every weld nut/mounting point on the unibody to very rigid specs. This would be very expensive, and it's simply not needed for everything. Things like the suspension pickup points and the headlight mounting system are usually controlled to tight tolerances - the suspension for obvious reasons, and the headlight mounts so that they don't run into certification problems and so the headlights can be aligned quickly at the plant. There are certainly other things that require tight tolerances, but those are the ones that I can remember offhand. Now, let's look at the diff strap mount - if you look closely, the mounts themslves are a couple of tabs that were welded onto the unibody, possibly by hand (I don't know what the manufacturing processes looked like at Nissan in the 70's). The diff strap will still work just fine if that mount is anywhere within an inch of nominal. This was almost certainly not lost on Nissan's engineers when they designed the unibody, and I doubt seriously that they spent much effort on controlling the positioning of these mount points. It probably doesn't really move around by an inch from car to car, but 10cm (sorry for mixing units) wouldn't surprise me a bit - Rob's observation of the slotted holes in the tabs on the strap mounts indicate that they were not counting on the positioning of the weld nuts with respect to each other in the same tab to be repeatable to better than ~3mm. So, I doubt that they did any better of a job of locating those tabs in three dimensions in the unibody itself. Now mind you, I don't have any proof of this for these particular mounting holes, and it's possible that the diff strap mount's close proximity to a suspension mounting point (which are generally well controlled) might help mitigate the problem. It would be a good thing to verify on several different cars - just something that I've suspected for a while, now.

Interesting - I was just thinking about the idea of using rod ends not long before you posted it. It solves very nicely the main problem that I had with the "Tyler" style mount - that being that it works just fine for one-offs, but I don't trust the repeatability of the positioning of the diff strap bolt holes for trying to make a saleable piece. I was just thinking again (always dangerous), and thought of this - what about putting rod-ends in the mounting holes at the front of the diff, a clevis at the appropriate spot on your upper brace, and using two bars (clevis on the bottom, rod end on the top) to locate the front of the diff? You could even put multiple clevis points on the upper brace to accomodate different diffs. ...or now that I think of it, one centrally located pair of clevis might be able to accomodate all of the diffs. Hmmmm...

That's looking really good Rob - very nice work. Might I suggest welding in some appropriate ID tubing for the through-bolts in that piece of square tubing at the top? This will avoid crushing the tubing when you tighten the bolts down. Sorry if that's a repeat - I couldn't remember if we had addressed it alerady...

The main reason is that I didn't need to - my exhaust exits on each side in front of the tires, so I can forego all that mess. Also, the placement of the second hump in your pic would be a bit too far to the right (notice that they are not symetrical) for the for/aft bars to tie in. If you wanted to do something like this with my setup, you could probably just move the second hump inboard, since you no longer need to leave room for the stock front diff mount. Bear in mind that everything is a bit tighter on that side, due to the diff nose's offset, which is about 15mm greater than that of the r200...

I think you picked the wrong piston - you need the L28 early/turbo to include the dish volume. I got more like 9.55:1

It's two heat ranges colder. I'd recommend gapping at .025 to .030". As far as timing, run as much as you can without detonating. Do you have an EGT gauge? When you start needing to retard to stave off detonation, back the timing off until either the detonation goes away or the EGTs get up around 1500 degF, I think that's about as far as you want to go (I usually shoot for mid 1400's)

I agree that all of those pieces should be balanced, just not as a single unit. Zero balance the crank and then zero balance the flywheel/pressure plate separately. This way if/when you get a different clutch, you won't mess up the balance of the engine.

Two things - first, if you are controlling boost with a popoff valve then the engine response will not be any faster - the popoff valve will have the same 'early cracking' issues as a wastegate would. Second, by controlling boost this way (or by turbo sizing as Jason mentioned), you are forcing the compressor to run off the edge of its map, so you will be running the turbo in the most inefficient manner possible (i.e., the intake charge will get really hot, and detonation will be a much bigger problem than it normally would for a given boost pressure)

no - they are dished