Zmanco

I need to decide on a BOV for my turbo build: L28 with T3/T04E. I'm leaning towards this one: http://www.siliconeintakes.com/product_info.php?cPath=11&products_id=488&osCsid=cb98cae5277702c33d39b9630c062240 I've seen this BOV mentioned in a few threads as being good quality and value. But even siliconintakes says this is difficult to adjust. For those of you who have used it, did you have to change the spring, or were you able to use it as-is? My goals are modest for boost - probably no more than 15 psi. Is this BOV overkill? Should I be looking at a different one?

I was just reading the exhaust section in Maximum Boost and saw his curve on p133 that correlates exhaust pipe diameter to max hp. According to him, 2.5" is good to about 475 hp! That seems rather optimistic compared to the experience on this forum. Any ideas why he is so far off of what others here experience?

I experienced the same issue in my 73 once and it turned out that there is a connector in front of the radiator below the bumper that had come apart just enough to kill the headlights. Everything else worked just fine. Not sure if you'll have that on a Fairlady, but it's worth checking. Warning: it was hard to see as everything had a layer of 30+ year old dust on it.

jeffp, I've done all the calculations and the T3/T04E .50 trim map fits the best. However, none of the maps specify the other specs, such as AR for either side, trim for the turbine, stage of the turbine, etc. I'm a little surprised how much of choosing a turbo remains a black art. BTW, does anyone have a source for Garrett turbos they can recommend? The local place here in CO can't get them with a stage V wheel, and the other place several have recommended, speedshopthagard.com, is out of business. I've found a few via google but hate to spend that kind of money on a site that I know nothing about.

jeffp, thanks for sharing your experiences - that's the kind of feedback I'm looking for. At this point I'm leaning towards a T3/T4OE with stage 5 .63 AR turbine and .50 trim compressor. To recap, my goals are to make power through 6500 rpm and around 275 WHP. The cam is a Schneider turbo grind with the following specs: Intake Duration (gross): 270 Exhaust Duration (gross): 260 Intake Duration (.050”): 230 Exhaust Duration (.050”): 220 Intake Valve Lift*: .460" Exhaust Valve Lift*: .460" Lobe Separation: 114 Question 1: I can't find any discussion about the differences between a stage III and V turbine wheel, but it appears the V is bigger. What trim would your recommend for the turbine? Question 2: From what I've read, it doesn't seem that the AR matters much for the compressor. Still, since I'm going to buy a turbo built to my specs, what should I choose? Thanks in advance!

Here's a summary of how to read the part number for NGK spark plugs. ngkplug.pdf

Thanks John, I suspect you have the TO4B - I understand the diameter is a bit smaller and will fit without a spacer. I currently have a N/A intake manifold that is port matched to my P90 head so was hoping to use that. But I also have a turbo manifold which I believe solves the PCV relocation issue. Once I have the turbo I'll mock it up and decide which one to use.

jgkurz, given I'm planning on the .50 AR, do I still need the spacer? From what I've read here I think I do, but I'd be glad to leave it off if it's not required.

For those of you who went with at T3/T4OE, how thick does the spacer between the manifold and the turbine housing need to be? Would 3/8" allow the compressor to clear?

Thanks everyone for the feedback - this is just what I was hoping for. FYI, the MSA stage II turbo cam is a Schneider cam with the following specs: Intake Duration (gross): 270 Exhaust Duration (gross): 260 Intake Duration (.050”): 230 Exhaust Duration (.050”): 220 Intake Valve Lift*: .460" Exhaust Valve Lift*: .460" Lobe Separation: 114 I'm torn between a stage III and stage IV turbine wheel but am leaning towards the stage III even though it will limit my power at the top end. Remember, my goal is "only" ~275 whp and most of my driving is on the street. I have a 4.11 diff so like turning revs... Now I'm looking for a good place to buy the turbo. I found a shop in AR called G-Pop Shop and spoke with him for a while. I have a near zero miles stock T3 which he recommends building into the hybrid, but that is around $700 (all Garrett parts though). I'm wondering if I should be looking at buying a new Precision Turbo (made by Garrett?) for only a little more and then sell the T3? Either way, any suggestions for where to buy the turbo? I'm in Colorado and would love to buy local if I could. Edit: what do you think about a Turbonetics version of a T3/T4O3?

So for a stage II MSA cam, should I go up on the compressor trim? The charts for the T3/4OE .50 trim fit my goals well (make good torque in the 3500 to 6500 rpm range) and I haven't been able to find one for other trims (such as .57). How would larger trim numbers change the charts? Also, can someone explain what changes with the turbine wheel as the stage number goes up? Is this just another way of measuring the trim of the turbine wheel?

So it sounds like a stage 5 turbine is the way to go with a bigger cam? Anyone else have any experience they can share?

I'm just about ready to buy my turbo and need some advice. Recap: L28et bottom end stock P90 shaved .080", port matched, unshrouded valves, CR = 8.4 MSA Stage II turbo cam I'm currently running a N/A with 10.3 CR and a cam that makes power 3500 - 6500 and my goal is to more or less maintain the same power band, but obviously make more power, around 275 whp. Since I'm running a 4.11 diff with ZX 5 speed, I'm not too worried about making boost at low rpms - I don't have a lot of torque down low right now and I'm fine with that. Based on dozens of threads I've read here along with my own calculations (I'm at 6200 feet) it seems like the T3/T4OE .50 trim is a great choice. http://www.mygen.com/users/dbruce/myz31/TurboMaps/L28ET%20Engine%20Air%20Flow%20and%20Turbo%20Compressor%20Maps.htm However, given I'm using a stage II cam, I'm wondering what the best choice is for the turbine wheel. Should I go with a stage 3 or 5? What are the tradeoffs of each with that cam? From what I've read, it will spool faster with the stage 3, but the stage 5 will breath better at high revs. Is that about right? Also, what is the recommended Trim and A/R for the turbine with my cam? It looks like most people are staying with the stock T3 housing (0.63 A/R?), but I can't tell what Trim they're running.

Here's how I described it in my notes: - install rebuilt '90 Maxima alternator w/90 amp capacity (Autolite #14661) Field wire (green) is connected to the upper/outer connector when the alternator is viewed from the front looking up at it. N (sense) wire (yellow) is connected to the lower/inner connector. My camera was off being repaired when I did this install so I couldn't take pictures. I'm off to India tomorrow but can take pictures when I return if that's helpful. The good news is that you've got a 50/50 chance

Great idea - mine are so scratched and embedded with dirt that it's hard to read the dial. Darrel, do you know the part numbers?

The spacer is too long - I spent a few minutes with the bench grinder to fix that. And yes, the connector is different - I made 2 short wires with appropriate crimped connectors to handle that. So it's not a plug in replacement. But with my 100W high beams and 2 12" fans, the 60A alt was getting hot enough that I could smell it so I had to do something. Sounds like a rebuilt was the right way to go in this case. But if the rest of the alt had been in good condition, sounds like the brushes would have been a good way to go?

90 Maxima is what I used - I suspect other years around that would work as well. Dave - I'll be curious to learn what you find - I've wondered if just replacing brushes was worth it given how much rebuilts have come down in price.

It's more likely to be brushes and IIRC they are pretty cheap so I'd start with that. Or, maybe now is a good time to upgrade especially if you're going to go with e-fans and non-stock higher wattage headlights. Maxima alt is good for 90 amps and is about $100 for a rebuilt. And there are many other options if you want/need more current than that.

I've read here and elsewhere that the factory turbo bolts can safely be reused, but this would suggest that's not the case. Do you know for sure about factory turbo bolts? Also, why can the ARP studs be reused? Aren't they also torque to yield? (Not trying to challenge you, just trying to clear this one up. Thanks!)

Here's another one ... This season I've been watching more motorcycle racing and have to say that the overall entrainment factor is so high - just amazing racing and bravado as well.

Wax, I suspect there are many others like myself who have subscribed to this thread because 1) we know that the stock intake manifold is a performance limiter, 2) are glad to see people like you taking a stab at ways to improve it, and most importantly 3) for many of us, owning our Z is just as much about the journey of experimenting and learning as much as it is about the ending when we have an improved car. Please keep updating us with your progress!

You said the PO rebuilt the engine and head. Are you sure the cam is stock? If it's not and he didn't check the wipe pattern and use the correct lash pads, it's going to sound like a diesel even when you have the lash set perfectly using feeler gauges. A long time ago I bought a head with a reground cam and that was the case. Took me a long time to figure it out given I didn't know what the term "wipe pattern" meant

Hi Jeff, if you don't mind, tell us about the boost control circuit you mentioned. I'm in the process of planning for turbo conversion and have been exploring the best way to control boost without spending a lot of $$$. If it's not a short answer, no need to hijack your own thread

I was studying up on BOVs and they are recommended to be installed before the throttle plate. This makes sense since they are supposed to vent the excess pressure when the throttle is suddenly closed. But I noticed that on the stock turbo engine, the BOV is mounted directly on the intake manifold AFTER the throttle plate. What was Nissan thinking?