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'72 240z RB25DET, no more ITB


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Fabbed up a cold air intake. Been planning it for a while. I cut a little too much out of the fender, but I will add metal before I put the plate covering the hole in the fender well. I wanted to do this before I yank the engine to tidy up the engine bay.

 

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Installed the boost solenoid onto my car. It was pretty straight forward and reminded me of the solenoid used on the ProfecB that I had on my Skyline in Oki. Setup was pretyy simple and was covered on the DIYautotune website. I went the extra step and wired in a 2 pin plug to give it the finished look. I started out at 0% duty and increased by 10%, logging each run. The boost increased logarithmically until I stopped at 55%, where the boost settled in at 12.8psi. I need to tune the fuel and spark to make it a little safer at those boost levels. Seemed pretty responsive and smooth though. The injector duty cycle is getting towards 60% at 10.5afr at 12psi. I would say getting it up to 11.5afr would be better and let me know what the HP is at this boost level and duty cycle. Looking more towards 260-270hp now. now for some pictures.

 

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I installed a z32 MAF . I have been wanting to use MAF for a while and I wired the sensor up when I originally built the harness. All I did last night is put it in and enable it in the programming but not enable MAF fueling. I just needed to make sure it works. I need to fashion a boost leak checker so I can make sure there is no leaks before I start tuning it.

 

I am going to use MAF/MAP load as this is what Nissan uses on most of the ECUs out there. It just uses expected airflow (rpm) devided by actual airflow to calculate load. Its kinda measuring efficiency in the airflow.

 

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I have had some issues with rough starts and rough running and misfires until it was warm. I have suspected some oil consumption issues for a while and I suspected the valve seals. I have read that the valve seals on these engines wear at about this timeframe and leak oil down into open valves while the engine is off. I pulled the head and took it in for a valve job, guides checked, and a mild surface.

 

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I took the opertunity to install my N42 manifold and a KA24 throttle body with a throttle cable. I also am fabbing up an o-ring fuel rail for the RB26 injectors.

 

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The throttle body is 10mm larger than the stock unit so I had to port the manifold.

 

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Here is a comparison of the manifold I had on the engine, which was the non-EGR 280zx version.

 

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Still need to finish up the fuel rail and install a throttle body spacer. The throttle cable still needs work and I have to rotate the throttle wheel to get it to face the correct direction. The Z32 MAF is working great and I have a pretty good tune working with MAF fueling. More to come......

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  • 2 weeks later...

Finished up the fuel lines and hooked up the throttle pedal. I pressure tested the fuel system and checked for leaks. The Aeromotive regulator is set at 43 psi from the last vehicle I had it mounted to, so no adjustment needed. I just need to clean up the wiring and figure out how to get the intake air temp sensor in between the bolts on my throttle cable bracket. Might just leave it off considering its not needed with the MAF. Tomorrow I am going to change the oil and flush the coolant. Then fire it up.

 

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  • 6 months later...

Decided to pull the front end and motor off of the Datsun in the past couple weeks. I am going to smooth out the bay and paint it. I would like to color match it, but I am really not sure what color I want the car in the end. I am just going to paint everything forward of the windshield gloss black. I don't think I will run any type of undercoat in thus car due to its lack of being driven in the rain. And I set the RB25 ITB motor in it just for fun and fitting purposes.

 

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  • 3 months later...

I painted the engine bay recently and dropped the L28ET back in due to me having to leave San Diego, Sad Matthew is Sad. In the process of trying to fit the RB25, I started selling my L28 setup. The coils were the first to sell. Almost had the motor when I figured the RB25 header was going to be too much work to get it to clear everything, so I decided to put the L28 back in. I had to tell the dude that was looking at my motor that I cant sell it. I dropped the L28 back in and reinstalled everything. I was just going to go back to a normal single coil setup with a distributer to give me ease of install, but..............I cant go back to a distributer due to certain pride issues and the lack of proper dwell time at higher RPMs. The stock coil sucks anyway. I decided to go with the famous "Buick" coil swap. I put it in quotes because I have some history working on my Dads Oldsmobile 3.8, which uses that coil, along with about 100,000 other cars of that era. I like it because it has normal blade connections on the bottom that makes it easy to install. That in combination with a standard RB/VG ingnitor pack makes for some hot looking sparks.

 

 

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I also got tire of my ratchet strap battery tie down and fashioned up a center battery hold down. I could have went with the original battery hold down, but it was a poor design that has problems with arcing on the battery terminals. Besides, I don't have a stock size battery anyway.

 

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  • 8 months later...

Long time since updates, so I will split it up in between posts.

 

I had to ship the car from San Diego to my hometown in West Virginia until I got established in my new home. While I was driving across the country, my brother call me and informed me that after my dad picked up my car from the shipper, Dad toasted the clutch. My brother tried to back it out of his driveway and it wouldnt move. The clutch was not up to par with the turbo motor anyway. It was the smaller 225mm (think KA24DE size wink.png). I have been planning the 240mm swap (-SR20DET, RB25DET etc) anyway so this was the excuse. While in hotels in random America on the way to West Virginia I priced an OEM spec Exedy clutch from Amazon and the flywheel from Autozone. All parts purchased for around $215. Me and my brother swapped it out when I was home on leave and then just left it in my Grandma's barn till I could drive it to North Carolina.

 

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Me and the fam doive up to West Virginia to pick up the Z and drive the beast down here, 550 miles haha. The weather wasnt too great and it was cold, but we made it. It was snowing the whole way through West Virginia and I only got about 18mpg.

 

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I quickly washed it and put the front wheel spacers and the air dam back on. I also installed a set of ST sway bars on it, which are 25mm in the front (stock 18mm) and 19mm in the rear (stock none).

 

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I worked on the tune. I had some setting issue with the injector dead time. Whenever the fan kicked on, it pulled the voltage down. This is normally compensated by boosting the dead time, but setting wasnt correct, so it went rich when the fan was on. This caused inconsistent AFRs when the fan was on and off. When I fixed it, I was about halfway through the tune when I decided to ditch the Z32 MAF.

 

I wanted to get rid of the Z32 MAF for a while, old technology isn't good enough for me. Sorry to all the guys who swear by these MAFs, but they are rapidly aging and need some TLC sometimes to keep them working, by the order of cutting them open and freshening up the solder on the connections. The Z33, G35 MAF is on damn near everything now days and they are pretty cheap on eBay, $30. Now granted they cant flow what the Z32 can, ~400hp, but when is an L28ET going to see that? Now this graph I am posting is MAF volts vs error, so hope you all can figure it out. Just kinda blur your eyes to see the general idea of the tune.

 

 

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Z32

 

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Z33

 

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Pics of the rear suspension setup.

 

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Getting ready for powder coating.

 

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Installed the newly powder coated stuff.

 

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Strut tubes welded. Got impatient and welded them up with flux core. I figure with my little 120v welder, that amperage was going to be an issue. With C25, the weld would be much cooler, and I considered C100. Decided to see what inner shield would give me with the full hotness that comes with it.

 

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Here is the struts screwed all the way in with a jack stand set to the exact height of the hub to simulate the wheel sitting on the ground. Keep in mind these are new springs with no settling.

 

 

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Just sitting on the suspension. No gas tank yet, diff and axles are out, and the brakes arent installed yet.

 

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Open R180

 

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Finally got the combo correct with the rear brake upgrade. In the beginning I was only able to pick up a set of '88 Maxima rear calipers and brackets. That year, the Maxima downgraded the size of rotor from 11.4 to 10.2, good for a front heavy FWD but bad for a nearly 50/50 car like the 240z. I have been looking for a way to run Z31 rotors all around since thats what I originally bought for the Modern Motorsport brackets that never came. I found another company that offered the bracket for the Maxima calipers called California Datsun LLC, formerly Datsun Parts LLC. I ordered them but didnt read the fine print, used the older caliper for the 11.2 inch rotor. Anyhow, I had a coworker order me a set of Maxima calipers in exchange for some work and now it is almost complete. Should correct the bias issues with the Toyota calipers and should allow the larger S12W caliper to be balanced with the rear.

 

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Used G2 caliper paint, awesome stuff.

 

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Check out the rust from using cheap air dry VHT paint.

 

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  • 1 month later...

Been a while since I worked on my RB25 ITB project. Back in Japan, I just fabbed up a shelf that the original RB26 throttle assembly sat on. It really took away from the look of the velocity stacks and I wanted something better. When I was in San Diego, I got to work on some old bikes and their multiple carb setups. I figure that I could do something similar on the RB throttle setup. It uses a bolt to adjust the linkage in between the three sets. Just fabbed up on link for now to see the proof of concept. Needs cleaned up and coated. Here you go:

 

Pictures from the fab work:

 

 

Decided to go full throttle quadrant. Just cut it off the stock RB26 throttle linkage. It looks eccentric, starts off at about 30mm radius up to 32mm radius at full throttle. This is before I put the adjuster stop on it.

 

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Here is it completed on the front. I supported the adjusted stop on the wheel side due to how far it was from one side to the other.

 

 

 

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Completed view, just need to fab up a cable stay for the throttle cable.

 

 

 

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Edited by winstonusmc
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  • 2 months later...

A few weeks ago I decided to integrate an Intelligent Power Distribution Module (IPDM) from a G35 into the 240z. I chose the G35 IPDM because I could see how it functions on a running car due to its CAN Bus function. The IPDM runs all power in the engine bay to include headlights, parking lights, electric fans, and windshield wipers over CAN Bus and ECU, Fuel Pump, and engine sensors over conventional relay signal wires. I am using an Arduino to feed the CAN commands to the IPDM and currently have all CAN controlled circuits functional.

 

The IPDM with the Arduino testing circuits

 

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Splicing in the engine bay harness and the fuseable link for the battery

 

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Next I picked up the wiper motor from the same G35 that the IPDM came from. For those who know, the 240z wiper motor can barely move the wipers on a dry windshield. Also, I wanted a motor that would work well on the IPDM.

 

Old vs New, notice the size difference

 

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Armature difference, same length which is the important part

 

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Mount differences

 

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Now a video

 

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Wrapping up this wiring job.......HAHA. The fuse box is mounted and all circuits are tested. The Engine power is all on the fuse box relays now, so no more EFI fuse/relay panel inside. Took out about half of the wiring going through the firewall that deals with power. For some strange reason, the wideband controller got some moisture in it and fried itself. I like the 14point7 stuff, but I think the control board for the O2 shouldnt be in the engine bay. I am going to buy the OEM controller they offer and shove it in the Megasquirt. Also installed some fog lights in the front air dam holes. I got the cheap ones from Walmart, more for just to op check that circuit and make a hard mount extending off the air dam support I fabricated a while ago. I cant stand when people screw fog lights into a plastic bumper and they bounce as they drive. Anyway, on to more pics....

 

Can we play "spot the fuse box"?

 

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Rigid mount and recessed for the factory look

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Edited by winstonusmc
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  • 2 weeks later...

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Uses an arduino mega for the micro controller. It has CAN bus connection. Its standby current draw should be less than 20mA, thats less than the clock that doesnt work. It has 8 Analog in, 2 can support 12v. Those will mostly be used for multiplexed inputs, the 12v will be bat voltage and Ign on switch. It has 10 digital inputs, mostly for ground switches like buttons, door switches, etc. It can drive 8 relays or MOSFETs for turn signals or light relays, going to use one for the idiot buzzer. Got a case lined up for it, hints the extra width to slide into an extruded aluminum case. I tried to make it as generic as possible so this board can be used for multiple applications. Total dimensions with case will be 2" x 4" x 5"

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  • 1 month later...

I have a buddy that wants to buy my engine after he gets his tax return, so the L28ET had to com out.

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So this makes way for the other engine. Before I dropped it in, I pulled the pan and primed the oil pump by hand. Just poured oil into the pickup hole and cranked the engine till it drew it in. Set in on the mounts and bolted it in. Its sitting on stock R32 mounts in a slotted cross member.

 

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I mounted the transmission and bolted the stock 5-speed drive shaft. I just had to slot the bolt holes in the trans cross member to get it to fit. Not sure if this was necessary or due to the cross member being smashed from the "rock sliding" from before I bought it. I am running an R33 71C trans I picked up when I was in Japan. The shifter is in the front of the shifter hole in the tunnel. I bolted up the starter and cranked it to circulate the oil. Threw the intake on to check for clearance, not close to anything. Perfect space for some foam filters. Wish it could move back about two inches. Guess thats what McKinney mounts do, but then my drive shaft wouldn't fit.

 

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