F20C in a 510

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okayfine
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Re: F20C in a 510

Postby okayfine » 16 Sep 2015 19:20

I'm not an engineer, but I've done some 510 fab before. That looks flexy as heck. The stock piece is a complete boxed tube end to end; you've got two frame mounts joined by flat bar with gaps and no bracing. Without the frame ends in a jig you've lost alignment for the front a-arms as well.

No sense in critiquing your welding, since you've said you're not going to be doing the welding. I'd expect your pro welder friend will retack and grind down what you've done, anyway. It doesn't appear that you cleaned off the flat bar's mill scale, so you've got iffy penetration.

Speaking of...if you're going to build a new/different front crossmember anyway, why do it twice with this one? This design isn't going to take mounts for a R&P, and IMO isn't going to do for a crossmember anyway.
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mroverkill
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Re: F20C in a 510

Postby mroverkill » 16 Sep 2015 20:22

Thanks for the criticism, Julian. I really appreciate it as I'm learning as I go with this build.

This is basically just a starting backbone for the crossmember, I pulled the crossmember, chopped the ends off, and reinstalled them on the body. I realize this isn't a jig, but I'm hoping (and relying on my friends' experience) that it will be close enough to retain the a-arm geometry. I then tacked the vertical pieces onto the ends, measured the horizontal length and cut the tube to fit. I then tacked everything together with the intention that it would hold the geometry when I removed it from the car. The plan is to take the piece you see above to another friend who is more experienced with integral member construction than the friend whose shop I am using to have it reinforced and finished. I believe it will be fully boxed from the vertical members to the bottom of the crossmember ends, and from the top of the tube section to the top of the crossmember ends.

As to why I am not simply making what I want the first time: I don't have the money to pay for the welding and fabrication and engineering that would need to go into it to do it correctly, nor do I have access to the tools I would need to do it the way I would like it done. The current location of the engine will allow me to use the stock steering linkage, and the crossmember should be good enough for now once it has been reinforced and actually welded by someone who knows what they're doing instead of Ray Charles with his eyes closed.

My way probably isn't the most correct way to do it, but it's what we have done for our Pike's Peak bastardized 914 with a 935 motor, and that car has more power (especially torque) than mine will ever need to handle (although that chassis is admittedly more rigid and less dependent on the crossmember for stability).

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okayfine
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Re: F20C in a 510

Postby okayfine » 17 Sep 2015 06:26

At a minimum, I'd suggest bolting the crossmember back to the car and ensure it's as straight as possible (those mountings aren't interference fit), then carefully remove it, flip it over, and lag screw it to a big piece of flat wood. Going by the picture, the flat bar stock seems tacked to the crossmember ends only along the top edge. This isn't secure enough to prevent pivoting of the flat bar versus the ends, say, should you lift the crossmember by one end with the other dangling down. Or it getting tossed around in the car between shops. Or getting manhangled at the other shop. Etc.

Otherwise I'd suggest cutting off what you have. Squaring up the cut faces of the frame ends. Plating those over with .125 or so. Then getting a length of 2x2 box or 2x3 box tube and building the connection between the two as needed to clear the engine/pan. This would involve pie-cutting the box tube to mirror the idea/angles you built. Materials cost would be minimal.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

mroverkill
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Re: F20C in a 510

Postby mroverkill » 17 Sep 2015 11:55

Thanks for the suggestions Julian. I squared the crossmember ends to each other (measured the diagonal between bolt holes) and they have stayed within a 32nd since yesterday. I will also be the only one handling the crossmember between shops, so I am not worried about it being handled more roughly than it has. My 'mentor' whose shop space and tools I am using is also rather stubborn and easily upset, so at this point I am going to hope for the best and follow his recommendation. Perhaps I should be more bullheaded about squaring the ends of the crossmember and using box tube, but I figure you have to pick your battles, and potentially pissing off the person whose tools I am using is probably not worth it over what will be a temporary piece.

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okayfine
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Re: F20C in a 510

Postby okayfine » 17 Sep 2015 12:32

The crossmember mounts using a trapezoidal bolt pattern.

IMG_0760.jpg
IMG_0760.jpg (250.89 KiB) Viewed 844 times
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

mroverkill
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Re: F20C in a 510

Postby mroverkill » 17 Sep 2015 14:00

The diagonals of a regular trapezoid should still be equal lengths, no? Perhaps my thinking was incorrect, so feel free to correct me.

I forgot to note when I took the crossmember off the car, but should the outer edge of the crossmember roughly line up with the outer lip of the frame rail for proper A-arm alignment?

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okayfine
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Re: F20C in a 510

Postby okayfine » 17 Sep 2015 14:11

Regular trapezoid diagonals would be equal lengths, but what measurement do you use? You could tweek a trapezoid far from being able to mount it to the frame, but if you tweeked it equally the diagonals would still equal out.

If they're equal and the thing still mounts cleanly, it's fine.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

mroverkill
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Re: F20C in a 510

Postby mroverkill » 17 Sep 2015 14:23

It bolts up easily and the diagonals are within a 32nd. Here's hoping it's good enough.

I do, however, want to make clear to anyone hoping to do this swap in the future that this isn't the right way to fab your crossmember. Hopefully I'll be able to model a part in the next 6 months that will be the right way to fabricate a crossmember.

mroverkill
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Re: F20C in a 510

Postby mroverkill » 02 Oct 2015 09:27

Just a small update this week, I managed to get the stock Honda header to fit into the engine bay, but that led to issues with clearance for the passenger's steering arm. I see two reasonable ways to approach this issue:

1) remove the steering arm, build a jig to maintain the angle and relative position of the pivot points, cut the connecting section out, weld in a custom arm that curves outboard towards the passenger's side of the car to allow more clearance on left turns, reinstall the stock steering gear.

2) convert to rack and pinion.

I am planning to pursue option two for a number of reasons. Firstly the stock recirculating ball system leaves much to be desired, secondly the exhaust is in such close proximity with the idler arm mechanism that I feel the heat would compromise the bushings quite quickly, and lastly machining costs involved would be much less than the cost of an MR2 rack conversion.

I also mounted the stock Honda brake booster and brake pedal assembly using the bottom driver's mounting hole from the stock pedal box as a reference point. One needs to drill for a 6x8mm center to center bolt pattern for the stock Honda mounts as well as cut about 1/4" into the cowl lip for clearance. Another approach would be to build a spacer to adapt the 6x8 pattern to the stock Datsun pattern which would alleviate the need for clearancing the cowl and allow the use of an unmodified steering column brace, but would require an extension to be made for the brake clevis.

Another issue arises with the use of the stock Honda brake booster and master cylinder: the stock clutch master cylinder location will not work. I am working on a solution to the problem and will post as soon as I have it figured out.

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okayfine
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Re: F20C in a 510

Postby okayfine » 02 Oct 2015 09:39

Pictures, man! :lol:
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

mroverkill
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Re: F20C in a 510

Postby mroverkill » 03 Oct 2015 13:44

I will try to grab some on Monday. It is a bit hard to learn how to do everything, do it quickly, and take pictures all at the same time.

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Re: F20C in a 510

Postby mroverkill » 06 Oct 2015 20:03

A rather sad update this time... Due to a combination of a lack of confidence in my own fabrication skills, a disappointment with the number of sacrifices I am having to make due to lacking the correct tools and needing to appease the person I am borrowing shop space from as well as simply not being able to document this build as well as I would really like to see it done I am going to suspend this build thread for a while.

The build will continue, I will see it through to the end. I simply can't juggle learning and documenting and quite honestly don't want the most well documented f20c swap to be one that has many compromises. I will revive the thread in the new year when I will have better tools and more freedoms in fabrication. I am happy to answer any questions about the swap as I have a fair knowledge of the challenges involved and what you need to be looking for in an S2000.

A few parting thoughts: I see very few downsides to this swap. Financially this swap is very affordable, the engine is one of the best four cylinders ever produced and has the potential for gigantic power with forced induction. It is also a very light power plant. There is not any aftermarket support for the swap, but there is not much more fabricating to be done than one would need to do for any SR or KA swap if one were not to buy motor mounts or the like.

If you are interested in the swap and have any questions feel free to shoot me a PM.

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okayfine
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Re: F20C in a 510

Postby okayfine » 07 Oct 2015 05:40

mroverkill wrote:but there is not much more fabricating to be done than one would need to do for any SR or KA swap if one were not to buy motor mounts or the like.


Well, having done KA and SR swaps and having looked at a handful of F20C510s, that's not really true. Just the amount of work to the engine crossmember puts paid to that claim. Nevermind the trans tunnel work, and that's not even talking about the wiring, which is a nightmare compared to the Nissan stuff of the KA/SR era.

I'm not saying this to put your comment down, but to prevent someone else from coming in, reading that, and then thinking that the F20C isn't any harder than a KA or SR swap. The reality is there'd be a heap more F20C510s if that were true.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

mroverkill
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Re: F20C in a 510

Postby mroverkill » 07 Oct 2015 06:21

You're probably correct, Julian. I'm basing my opinion off of reading about two of the swaps and only halfway performing one of them. I should say that the wiring for the F20C is actually not that daunting.

To run the stock ECU (2000-2005 MY) you need the engine harness, ECU, and the interior driver's side dash harness. If you don't want to use the digital dash you only need the 'ECU A' connector and the 'C101' connector from that harness. 3 wires from the C101 connector need Ignition switched +12, one needs constant +12, one needs started switched +12 and there is one ground. Only one wire from the ECU A connector needs to be looped back into the C101 connector (VSS circuit, usually looped through the digital dash). I will provide a complete pinout when I get my engine running.

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Re: F20C in a 510

Postby okayfine » 07 Oct 2015 08:17

There used to be a myth that the F20C swap needed the dash, ignition, and key, else the security wouldn't allow it to function stand-alone. Did that change F20C to F22C?
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson


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