Pyro

A small head gasket leak during boost will do that. A little water injection into one cylinder will make it run like that. I have seen that happen on a friends car. Took a while to figure that one out. I'm not saying that is it, just something else to consider. good luck.

I have always heard the magic number was 7psi/1K rpm. I also have a BBC and agree that it needs a bunch of pressure to keep that cam from going flat! After a few cam failures, I now have it idling at 45 psi with tight main a rod bearings (0.0015 -0.0020) and a high volume pump. I haven't had anymore oiling failures for over a year now.

My memory is getting foggy but this might help get a hp number. Well, with the stock turbo and stock cam and 12 psi of boost it dyno'd at 235hp and ran 13.8's at 103 - 104 mph in the 1/4 mile (76 280z with ac, stereo, spare tire, 200lb driver). Then I install a bigger turbo (t04b/t3) and stage 1 turbo cam and ran 13.6 at 108mph with 13 psi of boost. No dyno this time but I did use a G-tech meter at 13 psi of boost using a 2800 lb car weight and got 274hp. But not sure about how accurate those are. Finally I refined my fuel pump system which now more consistantly makes fuel pressure which in turn allows more boost, but I haven't taken it to the drags or dyno since the 108mph run. However, I can say the car feels much quicker with the better fuel system at boost levels between 12 and 15. I would change to an aftermarket ecu but I just can't image it running any better so why change it. I just got lucky with my combo. Trying not to be overally optimistic, I'm guessing at least 110mph in my next trip to the drags which should put the car right at 290 wheel hp with 15 psi of boost. With 85 psi of "net" fuel pressure (100psi-15 psi boost) will make a 19 lb injector (rated at 43 psi) flow like 280cc injector. (85/43)^1/2=1.4, 1.4 x 19lb = 26.7lb, 26.7 x 10.5 = 280cc. And six 280cc injectors at 85 psi of fuel pressure with a bsfc of 0.65 (turbo engine) and a 97% duty cycle will make 335 crank hp. So I'm on the edge.

Get the shorter (48mm vs 52mm) collar from the same 2+2 Z that you get the flywheel from. Or I think victoria british sells them.

Yes, move that pump to the back and as low as possible. The best way to handle the timing with the stock ecu is to just lock the mechanical advance and use the vacuum advance as normal. Then set the timing as high as possible before detonation. 18 degrees is a good starting point for a high compression turbo. The mechanical advance can be locked by welding up the slots in the distributor. Some people have just used silicone to stop the pins moving in the slots. The vacuum advance will shut down during boost so not to worry about that. Since the stock ecu and stock tach work off the distributor, I think you will have problems with the MSD boost timing retard. That is why I think it is best just to lock out the advance. Yes, my car is set up a little crazy. But I bet I got the record for the most HP from the stock NA injectors! Lately I have been running 15 psi of boost, 100 psi of fuel pressure at max boost, 27 degrees total timing, shifting at 6500 with a MSA stage 1 turbo cam and a T04b/t3 turbo. I have to say it is running very strong!

Good job! What kind of fuel pressure are you running at 5 psi of boost? You may need two stock pumps in parrallel to supply enough flow at high pressure. What are you doing for ignition timing retard?

Depends on how much they had to grind off the stock cam. You are talking about a regrind, right? If you go with a little thinner lashpad the lift will be slightly higher but the valve train noise will make it sound like a diesel. A thicker lash pad will move the wipe pattern closer to the valve and reduce the slop at the lashpad/valve interface, therefore making the valvetrain quiet. But lift will be reduced slightly from less of a rocker arm ratio. If you have access to a lathe, get 0.200" lash pad and cut each one to whatever size you need. I get mine from courtesy nissan for 3.00/each. I recently bought a set of 0.200" and used a carbine endmill to sink a 0.020" hole (3/8 diameter) in each of my lashpads which made them 0.180" thick. The countersink hole makes them like the factory lashpads. So, I had to use 0.180" thick lash pads to quiet down the valvetrain of a 0.440" cam. If you don't like a diesel engine sound then get the 0.180" lashpads.

I'm sure there are ideal set-ups for max hp and different ideal set-ups for street perfromance. I'm confident my hybrid turbo has less back pressure and makes a lot more HP than the old stock T3. But I miss the quick spool and low rpm street torque of the high back pressure T3 turbo. However, at the track I would be saying the opposite. Isn't it back pressure that spins up the turbo?

The return line should have only a few psi. 1 or 2 at max for a stock application. And, 1 or 2 psi can leak out. Yes, buy new fuel line and replace it. Use rubber line for fuel injection. If it doesn't say fuel injection on the hose don't use it. You will know you are buying the right stuff when you pay 6.00/foot for it. Any local auto parts store will have it. Get 5/16" hose.

You typically get surge at lower rpms and when the turbo is too big for the engine. A smallish sized turbo shouldn't even get the chance to operate in the surge zone. Look at a turbo map for that turbo and map out the engine rpm and cid to figure out if surge is even a possibility. I think you have some other issues with the BOV.

Sounds like you need more accelerator pump on the carb.

I think you guys aren't considering an important topic on "quenching heads". The high quench head is not less prone to detonate. For example, if you use 38 degrees of timing on a 10:1 cr L28 it will detonate no matter which head that you use (quench or non quench) What quenching does for you is increase the flame travel speed. Allowing a high quench head to use less total ignition timing to make max power. It is not the head that is less detonation prone, it is the lower timing that makes it less pingy. So, a 10:1 cr L28 with a N42 may require 38 total degree of timing were as a MN47 on the same engine may only require 32 degrees. And 6 degree does wonders to reduce ping. So, it is possible to turn down the total ignition timing without losing power. In fact, it must be turned down for max power. I personally wouldn't run 11:1cr L28 on pump gas without a big daddy cam (240+ degrees at 0.050'") even with a MN47.

FYI, The reason the quench design is less prone to detonation is not because it is just quenching. The quenching effective makes the flame travel faster and therefore requires less ignition timing advance to complete the burn. So, less timing prevents detonation without reducing power. But I'm not sure how much less the MN47 requires compared to the Old N42. On small block chevys, the fastburns need about 6 degrees less than the old style heads.

I didn't say that Z's weren't unique. I just said that most Z guys are going to stretch the hell out of every dollar they put in theirs Z's. And most do the work themselves and even do most of the fabrication work. So, there is not a lot of money for the suppliers of aftermarket stuff for old Z's. The aftermarket would rather sell a complete turbo kit for a 350Z for 8K. They know only a very small number of Old Z owners would put a $8K turbo kit on a $2k car. But adding a $8K turbo kit to a $35K car is a different story. And 95% of Z current owners would not own a Z if money was not an issue. The Z is cheap sportcar, so people that buy them most likely aren't super rich. That is the whole point of the car. Sure we have grow to love them but initially the cheap price gets your foot in the door.

I believe you can raise compression or raise boost but not both at the same time without an aftermarket efi system with ignition timing control. 7 to 8 psi (stock boost) will run ok with 8:1 cr but will be tricky to run 12 or 14.

I think I over estimated the expected 1/4 mile mph. I'm thinking you should do 111 or 112 mph with 15 psi and a 2350lb car. That assumes about 250hp. So you are about 5 mph short or about 25 hp. But, of course I could be completely wrong.

Jersey, I think you need to run a T-stat. Below is a write up on the need for a T-stat. I didn't write it, just a copy and paste job for another car forum. The issue with running without a thermostat is two-fold. The first part is that the thermostat provides drag on the water flow. This drag increases the backpressure the water pump and all of the enginesees. This additional pressure, over and above the nominal 15 psistatic pressure the radiator cap sets, raises the boiling point of the coolant. The reason this is important is that it suppresses localized film boiling at hot spots such as around the exhaust port. The transition from nucleatic boiling (bubbles of steam originating from irregularities on the surface) to film boiling (where the hot surface is coated with a film of steam) is called Departure from Nucleatic Boiling or DNB. DNB is very bad, for steam is a very good insulator compared to water. Once DNB occurs, the area under the steam gets hotter because the steam doesn't remove very much heat, adjacent metal which is still wetted heats from conduction. DNB happens there. The process spreads until substantially all the coolant-wetted surfaces are insulated by a film of steam. The engine overheats. In addition, the buildup in steam pressure forces the radiator cap open, bleeding coolant, therefore making the situation worse. The second issue is that of water pump cavitation and surge. If the pump is operated at high RPM with insufficient head pressure (provided by the frictional losses in the coolant passages and the thermostat), there is a great likelihood that the pump will either cavitate (localized boiling and/or degassing on the impeller) or surge (an unstable flow regime). Either phenomena is destructive. Cavitation's collapsing bubbles act like little sand blaster, eroding away impeller material. Surge can do the same thing and in addition, can vibration stress the impeller enough to break it. Many times what looks like corrosion damage to the impeller, especially when the housing is damage-free, is actually cavitation damage. The myth of velocity originated among those unschooled in physics or thermodynamics, I suppose, because a common racer "solution" is to press a fixed restriction into the thermostat housing neck when no thermostat is desired. The conventional (but wrong) wisdom is that the restriction "slows the water" as stated by the previous poster. In reality, all it does is provide some more dynamic pressure in the block by restricting the flow. The exact same result could be accomplished (assuming the water pump doesn't surge or cavitate) with a higher static pressure (cap pressure), assuming the system could withstand it.

No big money in Z/ZX aftermarket. Z/ZX's are cheap sports car owned by money pinchers. That is one of the main reasons we own Z's (cheap). Lets face it, if we had the money we would all own a new Porsche turbo.

Well that was a good time for 9 psi and no IC, then the extra boost and the upgrades should had yielded some really big gains, at least in the mph department. And I don't think atmospheric conditions would be that bad to not see gains in HP from all the upgrades. So, I think you have some problems there (as you already know). I see that you are using ignition control. How much timing are you using? How is the clutch doing? Maybe it is time for a little data logging with a wide band 02. Are you measuring boost on the manifold (after the IC) or on the turbo? Gear ratio changes, or in your case, tire height changes, don't effect the trap speed that much. Gear changes effect et's much more dramatically. In a 2350 lb car (car plus driver) with a L28 and 15 psi of boost, I would expect 115 mph in the 1/4 mile. Could be ignition timing, fuel ratio, clutch slippage, or boost leakage (to name a few). I know that this is a bunch stuff and is no help what-so-ever. But good luck finding the problem.

A friend of mine ran that combo and could boost to 7 psi with the timing locked out at 16 degrees. Made 180 hp at the wheels without an IC. The engine had good throttle responce off and on boost but was always on the edge of detonation (on boost). Plus the 16 degrees of timing plus 10 with the vacuum advance (26 total off boost) made the mpg pretty bad. He later reduced cr to 7.4 and turned up the timing to 26 degrees and the boost to 14 psi and made 260hp. With racing fuel, I'm sure 14 or 15 psi would be possible with a 8.8:1 Z engine. Or maybe a longer duration cam would make the engine less detonation prone. If a high cr turbo setup is used then an aftermarket efi system with ignition timing control should be used.

The stock turbo works great until 14 psi of boost. No need to upgrade the turbo if you just what to add a little more boost. In fact, your car will be slower with a t3/t4 if you run the stock boost due to the slower spool up of the hybrid turbo. Plus the hybrid turbo will require some fabrication to get it into the car and it doesn't seem like you have the means to install it. Therefore, I think you should just have the stock turbo rebuilt and turn the boost up to 10 psi. FYI, there is a huge difference in power from 7 psi to 10 psi. Then install an IC and go up another 2 psi. So, there is a lot more room to grow with the stock turbo. First get the engine installed and working before trying to upgrade. You already have a lot on your plate with school and with the turbo conversion. Don't complicate it with a bigger turbo just yet. Another thing. The stock turbo cam works great with the stock turbo. Adding a hybrid turbo will reduce useable rpm range by 1000 rpm due to the later boost while still being limited to the same maximum rpm (cam dependant). A hybrid turbo really needs a bigger cam to maintain a wide power band. I made that mistake and found I needed to add a bigger cam for the bigger turbo. And in the end, I prefered the stock turbo and stock cam for a street car, go figure. I really miss the tire spinning torque at 2800 rpm's.

In drag racing.......... 100lb is worth about 0.100 seconds. So a 500 lb loss makes the car about 0.500 seconds faster in the 1/4 mile.

The IC will have a pressure drop. So it is important to feed the wastegate pressure directly from the manifold (after the IC). What IC are you using? The hot pipe doesn't need to be that big. Just look at the 1 inch output hole from the turbo and you will see what I mean. 2" hot side pipe is enough for 400 hp. Turbos push a lot better than they pull so a big cool side pipe is more important. In your case a 2" or 2.25" or 2.5" hot pipe will not effect anything. Your turbo is very slow spooling. My old stock T3 was at full boost by 2800 rpm. My new laggy hybrid turbo is at full boost by 3500. Maybe your wastegate is not closing very well or your turbo is sick or the engine tune is off. I didn't notice any difference in spool time when I added my IC. Just a slightly fast car. I use a 2.5" cold pipe and a 2" hot pipe with a spearco IC on my turbo and it runs great.

I like it to dump back into the exhaust system. Lately having been working on a friends turbo Z that has an atmosphere venting wastegate and I don't like it at all. It is makes a loud obnoxious noise under the car that always seems to startle me since I never really know exactly when it will go off. It distracts me from driving and prevents listening for detonation. Plus it sounds like driving a car with stock exhaust manifolds without a muffler (barf). I also have my bypass valve plumbed back into the intake. But I'm not trying to impress anyone.

As far as the distributor goes I think you need to lock the mechanical advance and use the vacuum advance. That is how I do it on my turbo conversion on a na efi system. The vacuum advance will return to "no advance" once boost kicks in so don't worry about that adding timing during boost. The vacuum advance really helps off boost torque and MPG. If you don't lock out the mechanical advanvce in the distributor it will advance with revs. Check that with your timing light. I think you should lock out the advance and set the total timing to about 24 degrees. Or just set the timing with the engine at 4000 rpms to about 28 maximum, all the timing should be in by then. The initial timing would be about 8 degrees with 20 degrees in the distributor's mechanical advance. I can run 28 degrees timing at 10 psi without any problems. But if you run more than 10 psi, less timing will be required. If you plan on running more boost than 10 psi, then lock out the mechanical advance and reduce timing as needed. 15 psi on a stock turbo engine can handle about 23 degrees. And 3 degrees initial would be way to little if you use the stock mechanical advance. So, it is much nicer just to luck out the mechanical advance and set the timing high at idle. FYI, stock turbo timing is 24 degrees at idle. good luck with your project.