Sean73

525- I had identical symptoms to yours and it turned out to be a faulty CHTS. With an ohm meter, check the values of the CHTS on the CHTS, as well as at the ECU plug, and compare with the specifications in the Haynes manual or FSM. The CHTS may be faulty, or the wiring. What happened with mine, is that it would idle perfect until it warmed up. When it warmed up, I disconnected the CHTS and it would idle perfect again. I believe the O2 sensor must heat up to about ~600 degrees before it supplies a useful signal to the ECU. Then, closed loop mode only takes effect during cruise. With your TPS disconnected, the ECU doesn't know cruise from idle, and that's compounding the problem.

Mike, I am about to try what you've done with a 240SX viscous carrier, 88 SE halfshafts, and the MM CV adapters. (I am waiting on the halfshafts, to see if they'll fit the carrier). Anyways, I am wondering if you checked the contact pattern on the ring & pinion, or if it's unneccessary once you've checked the backlash. Also, do you really need a press to install the bearings? Do you think heating the bearings up a little (or chilling the carrier in the freezer), then tapping them in with a mallet would work? I am really curious if this swap can be done effectively without any special tools. Thanks for the excellent post. Sean 73 240Z, L28ET, T3/T04E, NPR IC, Z31 ECCS

How does this sound for a way to install a 240SX VLSD in a Z R200? 1) Get a low mileage 240SX VLSD differential case or complete diff ass'y off Ebay. $2-$400 2) Get 88 SE halfshafts from Victoria British (rebuilt) $380 3) Swap 240SX diff case into 300ZX R200, re-using the R200 12mm ring and pinion. 4) Get CV companion flange adapters from Modern Motorsports $200 I figure for under $1000, this would make VLSD possible in a 240Z, and get the CVs to go with it. The alternative for me is to pay $500 for a junkyard clutch-type, in questionable condition, and still have to pay the same amount for the CV conversion parts. I'd trust a used VLSD off a late-model 240SX over a used clutch-type off a 16 y.o 300ZX. The only thing I am not sure of, is if the 88 SE halfshafts will match the 240SX diff splines. Anyone know for sure? Sean 73 240Z, L28ET, T3/T04E, NPR IC, Z31 ECCS

525- keep in mind, and I am sure you're aware of this already, that predictions of increased fuel flow from the equations are only valid if you know the baseline flow rate of the injector. Since you're injectors are untested, you have to base your HP prediction on an assumption, which may or may not be valid. The 20 or so junkyard injectors that I have tested, are mostly close to 260cc +/- 10 cc. I think you can attain your goal of 230 RWHP with fuel pressure, but tuning is key. It would be a nice feature if you can get the FMU to kick on at 8-9 psi. I love my in-car narrow-band A/F meter. Even though it's accuracy is not like a wideband, it's senstive enough that I can notice immediate changes in the A/F at WOT, after adjusting fuel or boost. If the lights don't go to the middle of green at WOT, then I know I need a little more fuel at that boost level. My local dyno shops tap the wideband sensor off a secondary port on the downpipe. They send their customers to a muffler shop to have an auxillary O2 port welded on, so they can get an accurate wideband O2. Wideband at the tailpipe is sketchy, from what they tell me.

Looks good to me. How much faith do you have in your fuel rail? Has the rubber & clamps and o-rings ever been replaced? I am in the same boat, but here's my take: If I am going to go to all of the trouble of tuning or fooling the stock ECU into handling the excess fuel at low boost/off boost, then I might as well just "punt" and go for the bigger injectors that can do the job right. Even though the stock fuel rail would probably take the extra pressure, it would certainly exploit a pre-existing weakness sooner rather than later. I don't like the idea of fuel spraying on a glowing hot turbo. Sean 73 240Z; L28ET, T3/T04E, NPR IC, 8 psi, Z31 ECCS 300 miles on rebuild, down already with fried stock clutch.2400 lb RPS clutch going in.

Equation 1 is independant of fuel pressure, it only considers fuel quantity, which is the quantity that matters. Yes, if you increase fuel pressure, you increase flow capacity of the injectors, and you can re-solve equation 1 for the enhanced flow rate , but the gains are not 1:1. For example: The square root of flow is proportional to pressure. Increase fuel pressure 50%: 37 psi x 1.5 = 55 psi Square root of pressure increase = (1.50)^1/2 = 1.225 So, you gain 22.5 % more flow, for a 50% pressure increase. Your 24.7 lb injectors become essentially 30.26 lb injectors, that support 1.225 X 267 = 330 HP That 55 psi is ON TOP OF the boost pressure. Anyone can immediately see that increasing fuel pressure substantially is a compromise with safety. Maybe so, but these are the basic equations for sizing injectors that come straight out of Maximum Boost and other sources, and are known to be credible. Most turbocharging experts do not advocate radically increasing fuel pressure from stock to gain flow. So the statement, "X cc injectors support Y HP", is valid at an assumed stock fuel pressure. If someone is pulling 250+ RWHP out of stock injectors, they are doing one of two things: 1) Increased fuel pressure. 2) BSFC is slightly lower, within an unknown margin of safety that's engine and fuel dependant. With high octane fuel, you can probably get away with a lower BSFC. I suggest again and again and again, to anyone serious about turbocharging, get a copy of Maximum Boost, and you'll have the tools required to solve many problems in turbocharging.

In order to make 270 crank HP at sea level, you need ~10-11 psi in ideal conditions. In reality you didn't have ideal conditions. The lack of intercooler, probably cost at least 15% power loss. The ECU might be capping the duty cycle at 90-95% or your injectors might be faulty. Put it this way: 270 crank HP -15% air density penalty from lack of IC -15% drivertrain loss = 195 HP. Even if my numbers are off, they are in the ball park, and I think your non IC dyno is in the ball park. Adding an IC takes most of the air density penalty away, and I can see that 230 RWHP may be possible with a perfect IC on stock injectors. If the ECU caps duty cycle at 90 or 95%, than this number would be even less. You might say that some of the personal experience out there gets better results. More power is definitely possible out of the stock injectors, it just depends on what the engine's tolerance for leaning is. Fuel is the bottleneck: You will start to lean at 9-10 psi no matter what, because of the injector imposed limit. Anything above that, is a gray area that should not be visited for long periods of time. Sure, some people can run 12+ psi w/ an intercooler on the stock EFI. But I doubt they run 12 psi, at 6500 RPM, in 4th gear, uphill, in 100 degree heat, for longer than 30 seconds.

I have 225/60/16 tires and Panasports with zero offset. The tires did rub on bumps and dips in the road with stock suspension. I switched to Arizona Z car heavy duty springs, and the rubbing ceased. I am sure that if I hit a big enough bump, the tires would still rub.

Just doing some "back of the envelope" calculations, I figure you lose about 15% air density at 10 psi by not using an IC that's atleast 85% efficient. I figured optimistically that your turbo was 75% efficient. With a good IC, you'll gain most of that air density back, but turning down the boost to 8 psi will result in a 9% air loss, and to 7 psi will result in a 14% air loss. So, at 7 psi, you're at a zero power gain/loss, but as a side effect you might have gained a cooler engine that's more detonation resistant. Prefereably, I would address the fuel problem first before pursuing more mods, since fuel is your limiting factor right now. But if you must install the IC, I would set the boost at 6-7 psi, go to the dyno, and see how it behaves. One other thing, is that if you ever plan on doing the Z31 ECCS, now is the time to think about it. Getting rid of the flapper gives you more flexibility in IC and intake plumbing.

Cygnus makes good points. I have my IC installed the same way he does. The air traveling through the IC pipe on it's way back to the TB is not going to pick up much heat. For one, it's traveling a couple hundred feet per second. Number two, there is little surface area in the pipe compared to volume. Third, at high boost, hopefully you'll be going very fast, and underhood temps drop, and there's lot's of fresh air flowing through the engine compartment. I feel that optimizing the placement of the IC as well as the length of pipes and number of bends would should be higher on the priority list., then worrying about the radiator.

I bought one of those $125 Ebay Exedy kits, and like Bastaad525, I had heard some good things about these stock kits at moderate boost levels. It was advertised as the heavy duty PP. I'm guessing that to save costs, they use the same PP for 81-83 ZXT, 84-89 Z31 NA, and 84-87 Z31T, and would default to the heaviest duty PP of those apps. To complicate matters, I am using a 5 speed tranny out of a 720 4x4 truck. The clutch engagement is towards the top of the pedal, which makes me suspicious, that maybe I am not getting fully engagement, thus causing the slippage. Out shopping for slave cylinders, I found that the truck slave cylinder has a shorter rod. Maybe with the shorter rod, I'll move the engagement point to the correct position. Just a theory, I hope it works. If not, I'm going with the Exedy Racing clutch with organic disc, and HD PP.

I've got about 300 miles on my stock Exedy clutch. I've been taking it pretty easy on the clutch, (no hard launches, etc...). Well, I decided to go for it and went for a WOT run. The clutch slipped like crazy at the 2-3 shift at 5000 RPM and 8 psi. Is my clutch ruined? Or do I just need to break it in a little more? 8 psi is not much, but I do have 8.8:1 compression and should be putting out more power than a stock L28ET. I should have known this would happen. It would have been so much easier to install a performance clutch while I had the engine out. I think I'll give this clutch a little time and see if anything else happens. Need to check the clutch hydraulics and see if everything is in order. Any suggestions?

Who told you that the stock fuel system can handle 16 psi? Basic math dictates that the stock injectors at stock fuel pressure are only safe to 12 psi. The ECU probably limits it even more. Most of the guys here running over 12 psi routinely have fuel mods.

You would only see a minor difference in wastegate reponse with an intercooler because of the pressure drop across the intercooler. There are pros and cons of one configuration vs the other. It's covered pretty thoroughly in Maximum Boost.

If the turbo is running red hot, it's still going to run red hot with the wrap. All the wrap does is help heat retention (which aids flow) and reduce underhood temps. It won't reduce turbine temps, and due to the blanketing effect it probably will make the turbine remain hotter for longer after you shut down.

I had a boost leak that sounded like that once. Turned out to be a loose IC hose connection that was leaking/flapping under high boost. Since you've probably already ruled out hoses, your BOV or POV could be malfunctioning. Try turning down the boost 1-2 psi at a time, and see if it goes away.

I can't hear my MSD, or Lincoln Town Car fuel pump at all, probably because it's drowned out by the sound of the engine (installed in the engine bay). My Carter fuel pump (installed at stock location at rear of car), is very loud, but I only notice it at idle. I had some fuel supply problems due to a blocked feed line in the fuel tank. This might have stressed out the MSD. After cleaning the fuel tank, the MSD failed within 50 miles. I also had Bosch fuel pump out of a Porsche 911, that failed in similar circumstances. Fortunately, these pumps failed at idle, and not full boost! My other theory is that engine bay heat is too much for the MSD or Bosch, but it is installed on the passenger side near the frame rail, and it shouldn't get too hot over there. Sean 73 240ZT, L28ET, T3/T04E, NPR IC, Z31 ECCS

In a a standard surge tank configuration, I am running a MSD-2225 EFI inline fuel pump in the engine bay of my 73 240ZT. The pump failed a couple days ago, at the parking lot of Autozone of all places. I went in to Autozone, and I found that a 5.0 Liter 1988 Lincoln town car uses an identical-looking fuel pump, except the Lincoln uses a 1/2" feed, whereas the MSD uses a 3/8" feed. I bought the Lincoln fuel pump, swapped fittings, installed it in the parking lot, and I was on my way. I bet that the MSD fuel pump is borrowed from some OEM application, perhaps the Ford/Lincoln, or something else. If we knew the OEM application, then we could buy spare fuel pumps at the junkyard for $10. Any ideas? I would like to test the flow rate of the Lincoln pump and see how it compares to the MSD. Sean 73 240ZT, L28ET, T3/T04E, NPR IC, Z31 ECCS

As you know, jetting the Webers for a NA application is not trivial, nor is getting the parts. Double that effort for forced induction, and end up with something that runs maybe "almost as good" as EFI. You can probably get $800+ for your carbs on Ebay, which could pay for a brand new T3/T4, or be put towards programmable EFI. The triples do look and sound cool, but not ideal for turbo. If you want to get EFI on the cheap, I recommend the Z31 ECU, MAF and harness. It should be able to boost your 3.0 liter to 8-10 psi on the stock fuel injectors, without any special tuning. Also, the E31 head and cam won't be ideal for a turbo application. Sean 73 240ZT, L28ET, T3/T4, NPR IC, Z31 ECCS

Have you tried this: when the rough running starts, unplug the AFM , and use a voltmeter to look for shorts at each pin. If you find continuity between any of the pins, you have a wiring harness problem. Also, check operation of the TPS (check continuity) and CHTS (verify resistance w/manual) from the ECU side of the harness immediately after the rough running. If you're having to clean connectors every other day, I would suspect that the cleaning of the connections only solves the problem coincidentally, because you have to disturb the wiring somewhat to clean a connector. If you have a short, then sometimes simply moving the wire a bit will fix the problem, until engine vibrations and heat bring the problem right back. I assume your cleaning the connections thoroughly, so it would seem unlikely that a connection could corrode enough in a matter of days to the point of failure. Also, it helps if you can narrow down the problem to a single connector. It's unlikely that all the connectors would go bad simulataneously and require cleaning. Clean one at a time and see what improves the rough running. Once you can isolate the problem, you can splice in a new connector that that location. I had a similar problem with my Z31 ECCS harness. Turned out to be the MAF connector, which also shares a wire with the CHTS. The car suspiciously ran better with the CHTS disconnected. The MAF harness was shorting the CHTS and causing the car to run poorly. When I put in a new MAF connector, the problem disappeared. Sean 73 240ZT, L28ET, T3/T04E, NPR IC, Z31 ECCS

Do you have an A/F gauge? If so, what happens when your cruising at 2500 RPM and no boost? Lights should bounce back and forth indicating closed loop mode. Although you have checked all sensors etc.., when the ECU goes into closed loop mode, you can get some confirmation that it's actually receiving the proper inputs. In addition, I would turn down the boost to near stock levels and see what happens. This will help eliminate a few variables. If the problem goes away at stock boost, then I'd say your pop-off-valve theory is something worth chasing after. Plug that thing and be done with it. Good luck Sean 73 240Z, L28ET, T3/T04E, NPR IC, Z31 ECCS

Do a search and you'll find it's been discussed at length. I am running 8.8:1 flattop pistons in an L28ET. I am breaking in the motor at 8 psi boost and so far no problems at all. The P79 280ZX flattop pistons are very robust, and have the same thickness rings and ringlands as the turbo piston. I am monitoring A/F ratios very carefully, and have the static timing conservatively set at 19 degrees. I use a surge tank to prevent deadly fuel starvation. I figure I can run 10-11 psi intercooled before I start to lean out. Beyond 10 psi, I think I will need programmable EFI, and bigger injectors, and probably a better intercooler, especially in this Arizona heat. Why do you want a smaller turbo? Sean73 73 240Z, L28ET, T3/T04E, NPR IC, Z31 ECCS.

Did you replace the side seals on the rear main cap? Sean 73 240ZT

I doubt it's the intake collapsing. There is only a small amount of vacuum in the intake hose, even under high boost, not enough to collapse the hose. Your problem sounds like a faulty wastegate. Test the wastegate with compressed air and see what happens. I had this happen to me as well. Had identical symptoms as yours. I got a faulty wastegate acuator with my rebuilt t3/t04e. The half throttle richness sounds like a faulty TPS. I wouldn't rule out the AFM either. Sean 73 240Z, L28ET, T3/T04E, NPR IC, Z31 ECCS