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240Z EgoBoost by Boben


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My car is a -72 240Z which I bought as a project that the previous owner had started several years ago. When I first got the car it was on bare metal. I will first try to list all of the relevant progress that the previous owner had already done:

- complete tear down of the car

- Stripping all the surfaces on bare metal, partially by sand blasting and the rest by other more gentle methods

- Rost damage repair here and there

- Reinforcement welding of the body seams

- Replacement of the original longitudinal sheet metal beams with profile

- Mitsubishi EVO Tein adjustable coilovers to the front

- Front camber plates

- Arizona Z-car type lower control arms machined from steel

- Spare tire well removed

- Fuel fill hatch removed


With all this work already done it was a good starting point for me. Here is a list of all the work I have planned for the car:

- GTR-32 rear subframe assembly

- Mitsubishi EVO Tein adjustable coilover suspension to the rear

- 5x114.3 front hubs as the rears will be converted to 5x114.3 with the subframe implementation

- GTR-32 brakes on all corners

- bolt-on partial roll cage

- 15 Gallon aluminum fuel cell installation

- Body widening with a totally different approach

- BMW M60/M62 V8 hybrid engine which will be supercharged

- Magnuson M90 supercharger

- Lighter flywheel

- Getrag 420G 6-speed manual transmission from an E39 BMW M5

- MS3 fully sequential engine management

- BMW E46 M-Sport seats (brown leather)

- Restoration of the interior


As I have already had the car for awhile, some of the action points are already done. For example the GTR-32 rear axle already sits at it's place. I'll be posting some pics of the work done on that shortly.


Some of you have probably seen the body widening progress which I've documented over at the "Body kits and paint" section. Here is a link to the thread:



Here is a picture of the car before it was dismantled and in the status as it first came to me:



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I started my work with the Z by customizing the rear axle area to accept the GTR-32 subframe. The idea was to install the subframe in the height that would preserve the original control arm alingment and geometry. Basically this meant some serious cutting of the original sheet metal body and fabricating totally new mounting spots. The attached pictures are from various stages of the work. The modification is pretty much done now, requiring only some finishing touches here and there.












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After the rear axle mod I put some serious effort on the widening of the body. As already mentioned, the progress of that work can be found here:



With the sheet metal work related to the body widening pretty much done and the car still conveniently hanging on the rotisserie upside down, I figured it was time to fabricate the fuel cell mounts. The fuel cell is an aluminum 15 Gallon unit. The cell can be installed from underneath the car and the main idea was to preserve the stock floor level of the trunk, but obviously without the spare tire well. In this kind of installation the cell sits quite low, but the GTR subframe is still more near the ground and guards the cell if something were to hit the car from underneath.

I still need to get some suitable rubber inserts between the straps. I already found suitable rubber webbings to go between the cell and the metal frame.

The straps are bolted on to M8 distance nuts which are welded to the cell frame. In the front, the straps are firmly torqued against the frame, but in the rear there is a gap between the strap and the frame purposely left to enable tightening to desired tension of the straps. Once set to the desired tension, the bolts are locked in their place with a nut. Some might be thinking, why go through all that trouble, but I made the installation like this, because I didn't want any bolt heads sticking on my rear compartment floor.

I thought there was plenty of room for the fuel cell, but the reality is that there is no extra space. At first I almost forgot the hicas system of the GTR rear axle, but luckily remembered to check the clearance. The hicas will be substituted with conventional control arms, but if the hydraulic cylinder fits, there will be no trouble installing a hicas delete.


Here are some pics of the fabrication process:











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Finished up some welds from the interior side around the front fixing points of the GTR subframe. Then I assembled a mock-up engine with the transmission to test fit. The first idea was to use the oil pan found from 5-series BMW sedan, but unfortunately the cross member is just not going to clear. I replaced the oil pan with a part found from the BMW X5. The problem with the X5 oil pan is the height. When the engine is in place, the oil pan hangs lower than the cross member. Also, the X5 oil pan does not quite clear the cross member either. I need to assemble the mock-up a little further to really understand all the clearance issues. 






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  • 5 weeks later...

While I am waiting on my engine mount bushings to arrive, I decided to start installing the BMW seats. The seats are from an E46 3-series. They are sport seats with adequate side support for my application (Mostly street driving with occasional tracing), but boy are they heavy! I need to weight them so I can keep track of the total vehicle mass with all these modifications. Anyway, luckily the V8 will provide some decent power to move these seats.

The PO had already removed the stock seat mounts which would have been useless anyway. The BMW seats require to be mounted as low as possible to allow for adequate head clearance. In fact I needed to cut the floor a bit to get the seat leveled as the BMW original seat rails are bolted directly to the floor (with some reinforcements obviously). As of now, the floor is modified to get the seat in position. I still need to make the actual fixing points for the rails.






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How much headroom are you losing with the seats. I was thinking of using S2000 seats but those are really nice.

I really wouldn't know since the PO removed the original seat rail fixtures from the floor. I do have the original Z seats with rails, but the original mounting height information is missing. If somebody could make a measurement from the center of the seat to the ceiling we would have something to compare. The BMW seats are height adjustable, but I have them at the very lowest position in the pictures. I will measure the distance to the ceiling next time I go work on the car. At least for me the head clearance is adequate and I am not even hitting my head to the door frame when tilting my head and I am just shy of 6 feet.

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This is amazing, love the body work and attention to detail! Can't wait to see what other tricks and mods you have planned. Keep up the good work it is inspiring to see something outside of the normal american v8 hybrid.

Edited by 1969honda
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How much headroom are you losing with the seats. I was thinking of using S2000 seats but those are really nice.

The distance to the ceiling is 92 cm with the seat at the lowest position. As you might gather, the ceiling trim is missing from my measurement. Can anybody tell me what the stock distance might be?

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  • 1 year later...
  • 2 weeks later...

I cannot believe it has been over a year since my last update! Well, I have been too occupied with other stuff and the Z has gotten way too little attention.

I did however make some progress. I guess I could start by introducing my exhaust design, which unfortunately only exists as a 3D model for the moment.

The idea is to make 180 degree exhaust headers where the cylinders with opposite phase are routed to a common collector. Actually my design is a 4-1 collector so I guess it could be called 90 degree headers since an exhaust pulse is introduced to a single collector once every 90 degrees of the engine cycle. Two primaries have to be routed to the other side from each side and brought to the collector to realize the headers and the lenghts of the primaries have to be of certain length to tune for a resonance at a certain RPM. Equal lenght is quite hard and in my opinion not even the smartest move for a street car. I tuned the lenght of the primaries to get the best performance at the vicinity of the maximum torque point of the engine which is going to be around 4500 RPM. All of the primaries are within 7 inches in lenght. The slight difference in lenght will smooth the torque curve of the engine. Getting the primaries from one side to the other is obviously not trivial but luckily in the original placement of the engine in an E39 500-series BMW, the x-member is in the middle of the oil pan. In the Z, the engine is located behind the X-member so I can route the primaries in the "valley" underneath the oil pan - Lucky me! (I still need to make some modification to the oil pan, but it all should be doable.


Here are some shots from the 3D:





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When I designed and built the headers for my car, I contemplated making 180 degree under the pan headers like you are doing.  In the end, I decided that the added complexity wasn't worth the effort.


One thing I found necessary was to angle the collectors inboard so that the exhaust pipes converge toward the center of the car. 








Edited by 74_5.0L_Z
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@74_5.0L_Z, your exhaust pipe work looks fantastic. It does look tight also.

I've measured the engine bay and the engine up to the point where my head hurts, but I have yet to check the clearance for the collector. Based on your photo, it definitely needs to be double checked.

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  • 1 month later...

I decided to redo my engine mounts since the passenger side bushing was standing in the way of the AC-compressor. I was able to make full use of the original aluminum engine mounts without any modification. The bushing are from an E34 5-series BMW. The newer E39 model bushing was too big in diameter so this will do.












Now there is nice clearance for the compressor all around.



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After redoing my engine mounts, I noticed that my transmission was sitting a little low, well actually quite alot. The lowest part of the bell housing was sitting 50mm below the longitudinal frame rails. Unfortunately the transmission can only be lifted up 30mm without needing to cut through the transmission tunnel, so this is what I was aming for. I might need to fabricate an aluminum base plate for the oilpan and bell housing just to be safe. The minimum legal ground clearance in Finland is 80mm so I am still good for adjusting the ride height to 100mm measured from the longitudinal frame rails. I hope the car won't seem too high with those numbers.








The whole assembly seems quite rigid. I have to admit it was quite daunting to flip the car sideways on the rotisserie.





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