My New Toy, 1974 RB26 Powered 260Z

6682 Views 100 Replies 13 Participants Last post by 240Z TwinTurbo, 2 d ago

240Z TwinTurbo

Discussion Starter · 6 mo ago

9

Got a new toy from the same friend that sold me his 2009 GTR. I'll be posting some updates about the progress of the car, but it is a very clean and restored 260Z from about 20 years ago with no rust. Paint is still in great shape, although it needs a paint correction. Engine is forged rods and pistons with a set of cams and tuned with an old school Electromotive TechGT. Car dynoed [email protected] on 93 pump, but running less boost now due to traction issues due to the tires also being 20 years old. Car was retrofitted with RaceLogic traction control and even has AC. More details to come, but for now some pics!

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gtrbillet

· #61 · 2 mo ago

hunter said:
No normal fully trained GTR tech could undertake this project. Admirations plus....

I doubt there are any "trained GT-R techs" who's knowledge, skill and experience come close to that of 240zTwinturbo's. Across many platforms. He daily's a self-built, self-tuned 650 horse mitsubishi evo no less.

Just check out some of his DIY posts.

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240Z TwinTurbo

Discussion Starter · #62 · 2 mo ago

3

gtrbillet said:
I doubt there are any "trained GT-R techs" who's knowledge, skill and experience come close to that of 240zTwinturbo's. Across many platforms. He daily's a self-built, self-tuned 650 horse mitsubishi evo no less.

Just check out some of his DIY posts.

[email protected] on 93 pump gas and 36psi boost on a 2.15L

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240Z TwinTurbo

Discussion Starter · #63 · 2 mo ago

5

Got a lot going on with the 260Z and haven't been as good about posting pics and updates, but have a few today. Just got the lower valve cover back from Greggs Customs and applied the silicone bead, which has to dry overnight.

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Gregg also finished integrating the 60-2 trigger wheel onto the ATI damper.

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I only slid the damper on part ways since it is a press fit, but wanted to verify the magnetic pickup would clear all the belts. Definitely need to fabricate something to keep the wire from hitting the belts.

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240Z TwinTurbo

Discussion Starter · #64 · 2 mo ago

5

Finally got the lower valve cover installed so I could torque the crankshaft bolt. I modified the other end of a 3ft. piece of flat iron that was configured for the EVO crankshaft. This was enough leverage to easily tighter the crank bolt with my torque wrench.

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Next step was to bolt the pulley with trigger wheel to the damper, but now that I think of it I forgot to threadlock the trigger wheel.

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Finally, I completed the wiring for the crank trigger and also made a mount for the wire so it would not rub against the belts. Not a bad mount considering I made it in my garage with hand tools.

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240Z TwinTurbo

Discussion Starter · #65 · 2 mo ago

4

I upgraded the wideband to the LSU Advanced through 14point7 vs the older LC1 from Innovate using the LSU 4.2. I would have kept the LC1, but the connectors used to program the LC1 0-5V analog output were cut and the baseline curve for the LC1 didn't match the values in the Tech. Basically, I had no way to verify if the AFR being sent to the Tech was accurate.

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An issue with the RB26 and their original 6x throttle bodies is a lack of access to fittings post TB. There are two main tubes that reference actual manifold pressure, but they are both used for IAC. One is a conventional IAC that uses a duty cycle to control a solenoid to control air bypass necessary to stabilize idle The other was something I had not seen before. When the car is cold the valve is open bleeding air around the throttle bodies causing an increase in RPM, which is how it managed cold start. When the car started and the unit heated up it slowly restricted flow until the flow was eventually stopped. This was hooked up in the car unplugged so it was a full time air bypass.

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I ended up ditching that setup so I could use the intake manifold port to access a vacuum log so I could hook up all of my sensors and other boost referenced controls. Similar to a setup I have on my EVO, one of those ports uses a micro valve that lets me bleed air around the throttle bodies similar to a BISS screw in the EVO world. Anyway, it gives me exactly the number of ports I need, but will require that I retune the throttle stops and IAC in the Tech.

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joshuaho96

· #66 · 2 mo ago

There is a port on the back of the balance tube used to drive the OEM boost gauge that will work for a MAP sensor. The front of the balance tube has a port for the fuel pressure regulator as setup from the factory. If you want additional common vacuum sources the brake and clutch booster pipes before the vacuum check valves will work too but any failure there will cause you to lose vacuum assistance. There is a wastegate pipe on the factory piping that goes around the back of the engine as well as the atmospheric vent tube to raise boost pressure over spring setting. There is also a pre-turbo boost source dedicated to boost control in the factory setup. I recommend referencing the OEM vacuum diagram to see how it all works if you intend to keep the factory ITBs. Adjusting the throttle stops is not recommended as an idle control strategy, you can delete the cold start valve but you then need a more powerful AAC valve than what you get from the factory which has limited bypass air capability.

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kholdstare

· #67 · 2 mo ago

i suggest to spend a dedicated port for the fpr.

240Z TwinTurbo

Discussion Starter · #68 · 2 mo ago

joshuaho96 said:
There is a port on the back of the balance tube used to drive the OEM boost gauge that will work for a MAP sensor. The front of the balance tube has a port for the fuel pressure regulator as setup from the factory. If you want additional common vacuum sources the brake and clutch booster pipes before the vacuum check valves will work too but any failure there will cause you to lose vacuum assistance. There is a wastegate pipe on the factory piping that goes around the back of the engine as well as the atmospheric vent tube to raise boost pressure over spring setting. There is also a pre-turbo boost source dedicated to boost control in the factory setup. I recommend referencing the OEM vacuum diagram to see how it all works if you intend to keep the factory ITBs. Adjusting the throttle stops is not recommended as an idle control strategy, you can delete the cold start valve but you then need a more powerful AAC valve than what you get from the factory which has limited bypass air capability.

I appreciate your input and all the OEM tubing was stripped from the setup so I just have the balance tube with front and rear ports and the two 1/2" metal hose barbs off the balance tubes for the factory IAC controls. The port on the back of the balance tune is currently driving the vacuum referenced climate control systems through a one-way check valve. The back of the balance tube also has a large fitting driving the brake boost. The front fitting on the balance tube is driving the BOV and there is a another fitting off the #1 throttle plate, but it is on the plenum side when throttle is fully closed. Therefore, the two 1/2" metal hose barbs are the only source for intake manifold pressure and the rear one is used for the IAC valve leaving just the front hose barb, which I attached to a vacuum plenum. The whole point of the vacuum plenum is to act as an extension of the balance tube, which is why it is so big.

The micro valve (BISS in picture) bypasses about the same (maybe slightly less) as the cold start valve so I am hoping idle will be close with the micro valve fully open. The current tune utilizes 65% duty cycle on the IAC solenoid with cold start valve fully open (no power), which ideally should be lower (~5%) so just gonna have to see what happens when I hook it pack up. If I need more bypass I have the -8 ORB off the other side of the vacuum plenum where I can simply run a larger bypass valve.

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240Z TwinTurbo

Discussion Starter · #69 · 2 mo ago

kholdstare said:
i suggest to spend a dedicated port for the fpr.

There is a dedicated port off the vacuum plenum, but in theory I can run it from the back of the balance tube and relocate the climate control vacuum line to the vacuum plenum.

joshuaho96

· #70 · 2 mo ago

240Z TwinTurbo said:
I appreciate your input and all the OEM tubing was stripped from the setup so I just have the balance tube with front and rear ports and the two 1/2" metal hose barbs off the balance tubes for the factory IAC controls. The port on the back of the balance tune is currently driving the vacuum referenced climate control systems through a one-way check valve. The back of the balance tube also has a large fitting driving the brake boost. The front fitting on the balance tube is driving the BOV and there is a another fitting off the #1 throttle plate, but it is on the plenum side when throttle is fully closed. Therefore, the two 1/2" metal hose barbs are the only source for intake manifold pressure and the rear one is used for the IAC valve leaving just the front hose barb, which I attached to a vacuum plenum. The whole point of the vacuum plenum is to act as an extension of the balance tube, which is why it is so big.

The micro valve (BISS in picture) bypasses about the same (maybe slightly less) as the cold start valve so I am hoping idle will be close with the micro valve fully open. The current tune utilizes 65% duty cycle on the IAC solenoid with cold start valve fully open (no power), which ideally should be lower (~5%) so just gonna have to see what happens when I hook it pack up. If I need more bypass I have the -8 ORB off the other side of the vacuum plenum where I can simply run a larger bypass valve.

The fitting on the number 1 throttle body you're referencing is for the charcoal canister hence why it is not designed to pull vacuum at idle. It's meant to only provide weak vacuum at part throttle. The two half inch barbs are tied together on the factory setup to create a common vacuum chamber for all cylinders. I'm not sure if it's ok to use those two separately so I recommend verifying that each hose barb is common to all cylinders. If you want photos to see what everything physically looks like let me know.

240Z TwinTurbo

Discussion Starter · #71 · 2 mo ago

joshuaho96 said:
The fitting on the number 1 throttle body you're referencing is for the charcoal canister hence why it is not designed to pull vacuum at idle. It's meant to only provide weak vacuum at part throttle. The two half inch barbs are tied together on the factory setup to create a common vacuum chamber for all cylinders. I'm not sure if it's ok to use those two separately so I recommend verifying that each hose barb is common to all cylinders. If you want photos to see what everything physically looks like let me know.

Based on how it was setup when the car was purchased, the IAC and Cold Start valve where plumbed separately to each of the 1/2" hose barbs and it had no affect on idle stability. So the rear 1/2" barb was hooked to the IAC and then to the plenum and the front 1/2" barb was hooked to the cold start valve and then to the plenum. This was obviously not the stock configuration, but how it was modified to work with the aftermarket ECM.

My setup is not changing this, but simply ditching the unpowered cold start valve (just a metered leak) with another metered leak (BISS valve). There would be no reason for the balance tube not to be common to all cylinders since it connects to each set of throttle body's with an oring seal. There would have to be a physical wall in the balance tube for it not to connect all cylinders, but easy enough to validate this and report back.

240Z TwinTurbo

Discussion Starter · #72 · 2 mo ago

5

Thought I would post a picture of the customer IAC setup done by the previous owner. It's pretty simple with the IAC taking air from the plenum and dumping it into the intake manifold through the rear 1/2" hose barb. You can see that I added two 1/4" push lock connectors, which will be the supply for the new double bleeder setup. I ordered some straight adapters today since the 90deg won't be ideal and those will arrive Friday.

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I didn't like having the BISS attached to the vacuum plenum since it displaces air to the intake manifold. Additionally, the single bleeder valve was questionable in terms of it flowing as much as the OEM cold start valve when unplugged. Therefore, I removed the balance tube and drilled/tapped two 1/8" NPT holes to mount 2 bleeder valves directly to the balance tube. I also verified the balance tube is just one open piece referencing all 6 ports. I also decided to run the FPR off the back of the balance tube and will run the MAP sensor off the front of the balance tube, which means the BOV and Climate Control will be moved to the vacuum log.

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droptopp

· #73 · 2 mo ago

Great picture next to the EVO. My buddy kept his 260 from high school and just passed it over to his son before he passed a few years ago.

Lots of great memories shoe horning 5 people in it with feet dangling over the bumper.

240Z TwinTurbo

Discussion Starter · #74 · 2 mo ago

2

Thanks and I need a picture next to the GTR, which will make it look even smaller. I remember we used to fit 4 people in my 240Z and we were all 200+lbs.

Below was my first 240Z purchased in 1994, which was also turbocharged. I remember buying the Electromotive Tech II back in 1998 and had no idea how to tune EFI so it was trial by fire. That is back when having a wideband was not common so you tuned with a narrowband O2 typically balls rich and watched the knock sensor. Even though the car only ran [email protected], it was so much fun to drive with instant boost.

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240Z TwinTurbo

Discussion Starter · #75 · 2 mo ago

9

I want to point out this is not the first RB26 powered 260Z I've built. I did a custom setup for a buddy of mine in 2004, which included custom oil pan, 321SS twinturbo headers, custom downpipes, custom radiator, custom intercooler with piping, custom intake manifold with velocity stacks, custom coolant distributions, custom wastegate actuator brackets, etc. Essentially, I fabricated all the crap that made the engine produce HP.

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droptopp

· #76 · 2 mo ago

Had to zoom in to see that second turbo on the red onetucked in there - must be a fan favorite at cars and coffee.

240Z TwinTurbo

Discussion Starter · #77 · 2 mo ago

9

Spent the weekend trying to figure out how to install the 3 center gauges using the Lunar Loox kit I purchased. It has a nice bezel to interface with the dash, but the mount doesn't keep the gauge in place so it you push on the front of the gauge it easily pops out the back and with the dash fully installed you have no way to push it back in. The problem is the mount is a long lever arm made of plastic so it acts like a spring, but with not enough force to pop the gauge back in place.

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In the picture below you can see how the gauge pops out and leaves a gap between the bezel and the dash.

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This is where the fun began, which was designing a bracket that would allow me to provide pressure to the back of the gauge to keep it from popping out.

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And there you have it, as snug as a bug in a rug!

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gtrbillet

· #78 · 2 mo ago

Nice solution

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Wicked

· #79 · 2 mo ago

240Z TwinTurbo said:
Spent the weekend trying to figure out how to install the 3 center gauges using the Lunar Loox kit I purchased. It has a nice bezel to interface with the dash, but the mount doesn't keep the gauge in place so it you push on the front of the gauge it easily pops out the back and with the dash fully installed you have no way to push it back in. The problem is the mount is a long lever arm made of plastic so it acts like a spring, but with not enough force to pop the gauge back in place.

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In the picture below you can see how the gauge pops out and leaves a gap between the bezel and the dash.

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This is where the fun began, which was designing a bracket that would allow me to provide pressure to the back of the gauge to keep it from popping out.

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And there you have it, as snug as a bug in a rug!

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Genius!!

240Z TwinTurbo

Discussion Starter · #80 · 1 mo ago

5

Made progress on the two 4.5" gauges and installed the tach. Had to hack up the stock housing to work with the aftermarket mounting kit, but works like a champ. I'll try to get some better pics when they are all installed because there is too much glare coming from the garage door windows.

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I changed up the turbo to intercooler pipe and added an additional IAT since I had extra GPI on the Tech. Had to grind off the wrinkle finish to weld on the bung and then repaint with black wrinkle paint.

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Last think was to make a custom tube for the turbo inlet PCV. I will ultimately put a can on both the turbo and intake PCV, but for now I just want to get it back together and running.

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