Nigel

Yeah, I came across that article yesterday. No great surprise. I figured when I bought this thing that the diaphragm would be the weak link. We'll see how long it lasts. I just wanted something that would last me for a while until I can affort the real deal. Who knows, maybe I can get a few years out of it... Nigel

This has been a big help. Thanks! The more I think about this, and the more I read, I realize that I've been mistaking compressor surge for the BOV leaking. Like I said, this is all new to me, and I'm learning as I go. I'm not going to bother ordering another BOV now, and I'm just going to readjust the one I have. I think I have it set too tight, believing it was leaking. I remember trying to push the piston in with my thumbs when I had it off the car, and it was really difficult unless the adjustment screw was backed almost all the way off. Consequently, it never made sense to me that it could be leaking. So, maybe these knockoff BOV's aren't so bad. Mind you, I didn't buy the cheapest one I could find, but it was still a fraction of the cost of the real deal. If it lasts me a couple of years, I'll be happy. I'm sure I can work around the surge limit in 5th. I'm not very happy that it's happening, but I'm not about to replace the turbo. Now if I could only figure out why it's so slow to build boost... Any ideas on that? Thanks again!!! Nigel

Hmmm... compressor surge? It's a T3/T04 turbo, so it's not stock, but I can't remember the specifics (T04 "b"?), and I can't find the receipt at the moment. I bought it years ago, but up to this point I never ran it at more than 10psi, because I didn't have an intercooler. I never had any issues in the past. I installed an intercooler and the new BOV (I was using a 1G DSM BOV previously) last year, and this past weekend was the first time I actually got to try everything out, so I bumped the boost up to 15psi, and that's when the problems started. It never occured to me that I could get surging at low boost and low rpm, but it makes sense. I tried tightening up the screw on the BOV, and it didn't really seem to help much. I know this turbo always seemed to be really slow at building boost. Back when I was running ~9psi, If I floored it in third gear at say 2500 rpm, I wouldn't hit 9psi until around 37-3800 rpm. So, what does all this tell me? I'm having a hard time differentiating between the sounds that the BOV is making and what could be surging. Is this BOV really the issue, or is my turbo not sized properly? Or do I not have something set up properly? This is new territory for me, so I don't have any experiece to fall back on. I hope I don't end up spending the whole summer trying to sort this out! I didn't get to drive the car at all last year, and I was really looking forward to just enjoying driving it this summer, not spending all my time troubleshooting. Any advice on how to proceed? I guess I could remove the BOV and try boosting in 5th gear again. But if it surges, then what? New turbo? Thanks!!! Nigel

So, I decided to roll the dice and try one of those ebay knockoff Greddy Type RS blow-off valves. I bought it a year ago, but I finally got to try it out this past weekend. Quality wise, it “looks†great, and it came as a complete kit with gasket, 2 metal tee’s and silicone vacuum line. The anodizing looks good, but I’m not sure if the piston is hard anodized. Anyway, performance-wise, it’s a mixed bag. It has no problem holding full boost (15psi) but only up to 4th gear. If I floor it in 5th at 3000 rpm, I can’t boost past 10psi! As soon as I get close to 10psi, the BOV starts fluttering, the boost gauge needle bounces around, and I can’t get anymore boost. So it’s obviously leaking. But why only in 5th gear? Full throttle in 4th at 3000 rpm and I get 15psi no problem, even when I try building boost slowly in 4th (although, maybe not quite as slow as it builds in 5th at that rpm). Now, mind you, if I back off the throttle just a bit in the gears other than 5th, but still making boost, the BOV immediately starts fluttering, and it won’t stop until I completely back off. Adjusting the preload on the diaphragm spring doesn’t seem to make much difference, other than muting the effect somewhat. I don’t really know much about pneumatics, but it appears that the BOV requires a very minor pressure differential between the intake manifold and the intake plumbing where the BOV is located for the BOV to open, even with the diaphragm spring preload set really hard. Does anybody know if this has something to do with ratio of the diaphragm diameter to the piston diameter? But why would I get a pressure differential at full throttle in 5th but not 4th? And why doesn’t the spring preload have much effect? I’m going to order a genuine Greddy BOV, but I’d really like to understand what’s going on here, because I’d hate to spend the extra money only to have the same problem because there’s something else I missed. Any insight would be greatly appreciated. Nigel '73 240ZT

I don't know if you noticed, but you can see the oil cooler in the 5th picture down... Nigel '73 240ZT

Hey Quentin! I'm glad to see it's finally together and running. It looks like Tony did some nice work (as always). I'm looking forward to hearing all about what it's like to drive, and how you like tuning the Microtech. You mentioned in your last e-mail that you had some BOV questions for me. Give me a call... Nigel '73 240ZT

As I recall, that comercial was "banned" due to the display of reckless speed or some such nonsence. I did have the good fortune of actually seeing that comercial aired during the superbowl. I watched the superbowl just for that! Nigel '73 240ZT

I was at Showcars last year and met the owner in person when a friend of mine was looking to have some custom flared front fenders made up. The whole thing turned into a complete disaster. After many months of waiting for the fenders to be made, and several trips to Showcars, my friend finally gave up. The impression I got of the owner is that he's some kind of Christian fundamentalist (religious art everywhere, and a Christian station on the radio - unusual for this neck of the woods), ironicaly with some questionable business ethics. Strangely enough, I don't think he's necessarily dishonest. I think he intends to deliver everything he sells, but if it takes 5 years to do it, or he forgets about the order... well, have "faith." He'll get to it eventually. But I sure as hell would never do business with him unless he already had the part made and I could pick it up in person. Nigel '73 240ZT

I had this problem when I used a fan from a 280ZX Turbo in my 240Z. If you have the wrong one in there (which it sounds like you do), it will put the fan too close to the rad, and it will jam. I discovered the fans come in at least 2 different offsets. I'm not sure which year and model you want though. Nigel

Are you getting 12V on the injector wires at the connector on the ECU ? It's the white nylon plug. Three of the wires going into it are for the injectors (one for every 2 injectors). If you're getting 12V there then the circuit is complete, and the transistors in the ECU aren't switching on for some reason. Where's the ECU? Any chance water could have leaked onto it when the car was washed? Nigel '73 240ZT

My Subaru Legacy Turbo BOV opened at -5inHg. And my 1G Mitsubishi Eclipse BOV opens at -15inHg. So the factory engineers obviously see some benifit to this... Nigel '73 240ZT

I'm just passing on information I read, based on some actual tests, so I'm not pretending to be any kind of authority on this. I'm just sharing what I read. In fact, I think I actually followed a link posted from a topic on this forum. I think that was the point. I suspect that air has some velocity and momentum, so it's going to want to keep traveling towards the end of the core. And like when you blow across the top of a straw, the air is going to be drawn out of the core closest to the inlet, when the velocity is highest. Anyway, if I can find the link I'll post it, but I don't really have any more to add then that. Nigel

Somewhere on-line, I've seen some data that showed that vertical core intercoolers (more short tubes rather than fewer long tubes) with inlet and outlets on the same side were not really superior to any other design. From what I recall, most of the flow is only through something like the 20% of the core that is furthest from the inlet. And apparently, air is actually sucked out of the core closest to the inlet because of the velocity of air moving over it. Idealy, more short tubes are better than fewer long tubes for reasons stated previously, but unless you have a lot of flexibility in your mounting and plumbing options to take proper advantage of that, I wonder if it's really going to make that much of a difference? Nigel '73 240ZT

Hi Nathaust... Thanks for the compliments! The heat shield I bought is held on by two bolts, which attach the center section to the turbine housing. Unfortunately, the center section interferes with the bolts, so you can loosen them but not remove them. In order to remove them, you have to rotate the center section (or conversely, the turbine housing, but it's bolted to the manifold and downpipe, so it's not moving), to a point where the bolts can be removed. This means that all of the bolts have to be loosened which is a major PITA!!! In retrospect, I should have just either slotted the holes in the heat shield, or removed the whole damn turbo! In the end, the center section and turbine housing were in the same orientation. I did reclock the compressor side though. I needed the compressor outlet pointing up at a shallower angle so that the turbo to intercooler piping would run under the intercooler to throttle body piping. Here's a link to a bead roller sold by the Eastwood company with a picture and an explanation of why you do it... http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemID=10882&itemType=PRODUCT&RS=1 $400 for that thing though! And it says you can only do up to a 2" dia. tube, although I don't see why you couldn't do bigger. I've seen one for $100 dollars that doesn't look as pretty but does the same thing. It's still a lot to spend for something that you may only use a few times though. Nigel

How did you hook up the adj. proportioning valve? On '73 and later Z's the stock proportioning valve uses pressure from the front right brake line to modulate pressure to the rear brakes. If you gutted the stock proportioning valve like a lot of people will mistakenly tell you to do (because they assume that it's the same as '70 to '72 Z's), then this could mess things up. Nigel '73 240ZT

If you go to the bottom of this page: http://www.sdsefi.com/fuelmaps.htm you can see the stock values for all three map sensors (you didn't say which you have). They rise at a constant rate, so it's not so much of a curve as it is a straight line. Nigel '73 240ZT

That should be correct... Nigel

Thanks! It's been a hell of a lot of work. The piping is all aluminum. I cut all the pieces and then had our machinist at work weld them together for me. He has his own tig welder at home. I wish we had one at the office! The piping came polished, but it gets scrached up really easily. I've already gone over them once with a buffing wheel on my bench grinder with some rouge polishing compound, but it's going to take some work to make them really sparkle. I was surprised at how easily the aluminum welds polished up though. Nigel

The fitting opposite the adjustment knob should connect to the boost source (intake manifold), and the side fitting goes to the wastegate actuator... Nigel '73 240ZT

Thanks guys!

Well, I know I started this thread two and a half months ago, but I've only been able to put in two actual weekends of work between then and now. I forget if I mentioned it, but I store my Z at my dad's place in the winter which is in another city 400km's away. But I try to plan everything in advance of my visits, and do as much of the fabrication work as I can in the machine shop at the office. Anyway, here's what I've been up to... I got the oil cooler remounted. It's now placed between the intercooler and the rad. The intercooler fits nicely between the brackets. If you look closely, you will notice that the brackets actually offset backwards slightly. I did this so that the oil cooler would not be too close to the intercooler. All I did was notch the tubes on opposite sides, bent them and then welded them up. I got to try out my $60 auto darkening welding helmet for the first time and I can't get over how much easier it makes welding! I wanted to convert over to a 60mm throttle body because my intercooler plumbing is 2.5". But the way I wanted to run the intercooler piping meant that I couldn't use a 1" spacer for the throttle body and keep the mechanical linkage. So this meant converting over to a thottle cable. I picked up a Lokar 36" universal throttle cable and set about figuring out how to install it. I ditched the linkage they supplied for the gas pedal end of the cable and I made a little barrel adapter to use with the linkage on the throttle body, just like the stock setup would have been. This reversed the way Lokar expects you to use the cable, but who says you can't improvise. Unfortunately, I forgot to take a picture of this. The next challenge was figuring out how to support the sleeve of the throttle cable. I thought I would have to attach something to the intake manifold for the throttle body end of the sleeve, but that would have meant waiting till my next trip to work on the car to design something. I had the throttle body with me (From a '92 Nissan AXXESS by the way), so I decided to design a bracket that would attach to it instead. This ended up working out much better: Here it is with the throttle body installed on the engine. Note that the bracket also turned out to be a perfect mount for an intercooler pipe support clamp!: I now had to figure out how to secure the cable sleeve to the firewall. This turned out to be really easy. I just picked up a couple of 5/16" fender washers, and I made some gaskets out a rubber sheet that were the same size as the washers. The fender washers were big enough to cover the hole in the firewall where the original throttle link went through. I put a washer and gasket on each side of the firwall, stuck the throttle sleeve through and installed the nut on the other side. Finally, I had to connect the other end of the cable to the gas pedal. I bent the arm at the end of the gas pedal 180 deg, so it was now facing the back of the car. I drilled out the ball adapter on the end of the arm and attached the end of the Lokar cable to it. I had to bend the arm the other way because there would not have been enough room for the linkage on the end of the Lokar cable: Since my last visit, I've had all of the intake tubes welded up, and I made a really cool flange for the BOV (forgot to take a picture of it too). I borrowed a bead roller from our local Z specialist, Whitehead Performance, and rolled beads on all the pipe ends, so I shouldn't have any problems with boost leaks. I've started the final fit of all the pipes. Unfortunately, I didn't quite leave enough extra material on the pipes for the beads, and my pipes ended up being a little on the short side, but I think everything will work out ok. So, I'm about 85 to 90% there as far as getting the car running. However, our first club drag event is less than 2 weeks away, and I won't be able to work on the car this coming weekend! My plan is to take the Thursday and Friday off before the race on Saturday to try and finish everything off. I have the feeling I'm going to be starting the car Friday night, going for a quick shakedown run and then leave for the track the next morning. That should be quite the adventure... Nigel

The hole is to prevent pressure being trapped between the MBC and the wastegate actuator, holding it open and slowing boost response. If you're experiencing boost spikes, drilling that hole won't help. If anything, it will make it worse. Are you sure the MBC is the problem? What happens if you bypass it? Nigel '73 240ZT

Yeah, I did that too a couple of years ago. Fortunately, just before doing the oil change, I had installed some used injectors and they were sticking, so the car ran like crap. I shut it off right away, and when I got out of the car, I noticed a pool of oil spreading out under the car. Who knows how long it would have taken me to notice otherwise! Now I check the filter for the o-ring every time I remove one. Nigel '73 240Z