1985 Series 3 restomod with s5 13BT on LPG, R&P steering

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KYPREO
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1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 3:18 am

Hey guys

I've been meaning to start a build log on here for a while. I maintain a build log on a forum I administer, AusRotary.com, and this will largely mirror what I wrote there.

By way of introduction, I have owned my series 3 RX-7 since 1999. I'm the large owner and have seen through a lot. It was largely standard for many years, with only upgraded suspension, exhaust and an extensively modified standard Nikki carburettor. I managed to get 119rwhp @7800rpm out of the standard 12A, which is truly incredible given it had standard ports. Those tall primary ports on the series 3 really do help once you get the engine breathing properly. A decent diff ratio like 4.44 and you have a fun car to drive.

Unfortunately in around 2005 my trusty old 12A developed a water seal leak after overheating (blocked radiator). Proper rebuilds were not possible back then since we had all just run out of new 12A housings and pretty much all of the second hand ones had severely worn chrome - even the apparently healthy engines. This was just an inherent weakness in 12A housings. Nowadays lots of people are able to machine down and restamp 13B housings as 12A but not back then.

So I bought a halfcut from a JDM series 5 halfcut and set to work transplanting the engine. I kept it in NA form and using an intake manifold adapter, ran the same s3 12A manifold and modified Nikki carb. Since the 13BT has lower compression rotors and the exhaust I fitted was more suited to a bridgeport, this engine made less power than the 12A, but it had a lot more mid-range torque.

In 2008 I moved house and although I updated my address with VicRoads (our local road transport authority in Victoria), the online tool didn't work and I never got my rego renewal reminder. By the time I figured out it was too late and my car was unregistered. I tried to re-register, then picked up the new engine number for the 13B (even though it all looked stock), ran it through the database and saw it was a turbo block, then said I need engineer approval as the engine was rated at 147kw instead of the factory 85kw. :shock:

Basically I was up a creek. Marriage, house, renovations and 3 kids later and the car is still off the road, but I am now in the process of getting it back together.

Here is the ride now:

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And now for what's in store...

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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 3:48 am

The plan:

* full interior and exterior restoration back to factory specs. This is down to factory spec stereo, steering wheel, trim, decals and caution labels, carpet everything. Anything that isn't up to scratch will be replaced with new Mazda parts from the dealer (I've collected heaps of stuff over the years) or if no longer available, restored. I've got a plastic repair expert refinishing all of my faded or scratched plastics back and colour matched to original specs.

* repair rust in the usual spots (hatch drainage area on both sides, rear quarter window bubbling), respray back to factory colour (V3 tender blue) and put some nice pin stripes on like dealers used to do here, then refit all my NOS badges still in their bags with Mazda parts stickers.

* retrofit entire crossmember, steering, struts and hub from a series 5 turbo RX-7. Engine will then be mid-mounted like a FC, not front mounted like an older RX. Rack and pinion steering will be kept power assisted, but instead of the mechanically driven pump, I'm using an electric pump from a Holden Astra (Opel Astra G for those in Europe). This might seem overkill, except I will be running a lot of caster. I'm currently using 5.5 degrees and it's significantly heavier than standard especially with the 17x7 wheels and 205 wide tyres.

* adjustable coilover struts for front and rear supplied by my good friend Adam at ACBron Motorsport

* FD calipers and FD sized front brake rotors (294mm), braided brake lines etc

* Factory s5 turbocharger, mounted on factory manifold (made possible by the steering conversion), but with 3 inch dump pipe and separate wastegate dump pipe. I will probably also highflow the turbo using a T04B or GTX35 spec comp wheel with between 55-60mm inducer.

* Straight LPG induction using Gas Research carburettor, twin B2 converters (modified to run boost), capable of flowing 600hp worth of LPG and 400cfm at the carburettor. This will replace the entire fuel system, including tank and lines etc. The purpose for the LPG conversion is 3-fold:

(1) it's cheap to install and run (50 cents AU per litre compared to $1.20 regular unleaded, let alone high octane or E85), tuning comparatively easier;
(2) high octane. Can run high boost with gas and run much closer to stoichometric with more margin for error;
(3) legal compliance. Australian emissions laws do not apply to vehicles manufactured before 1986 that run on LPG only. So, it's basically a free for all, provided it passes CO concentration test at idle. yay

I've now collected most of the bits I need and car is going in for the steering fabrication in about 2 weeks. sya

I'll post some pics of the bits I've been collecting....

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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 3:54 am

Pretty much as new dash

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restored, rust free seat rails

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Mint factory leather-wrapped steering wheel. Unlike you guys, our higher spec series 3 got a leather wrapped wheel version of the moulded urethane one you got.

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NOS side badges (3 pin, series 3 - they are different from s1/2 which are 2 pin)
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NOS bonnet stay clip. Once again, s3 is different from earlier and later models. Interestingly, like many series 3 parts, it's actually the same as a Miata
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NOS FD rear oil pressure reg - opens at 110psi - NLA in Australia according to Mazda Australia but you can still get these in the US
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NOS FD front reg spring plus shims to match FD rear regulator, Atkins e-shaft bypass pellet
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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 3:58 am

series 5 turbo subframe, steering rack, hubs, sump etc.

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Astra EHPS pump

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FD calipers
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4x114.3 hubs to suit FC stub axles which came off US market series 4 NA models. These allow you to run the same bolt pattern and offset as series 3 but on a s5 strut. Got lucky sourcing these and paid a shit load in shipping from the US.
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That's all for now.

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spirit r
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by spirit r » Wed Mar 23, 2016 4:06 pm

KYPREO wrote:
That's all for now.
Sorry i am unable open your pictures

https://lh3.googleusercontent.com/-oncU ... /image.jpg

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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 10:02 pm

None of them? I don't get it. It works for me even when i cut and paste the image link and open in a different browser. Is it a remote linking policy on this forum?

I can't edit my own posts to alter links either.

Mods?

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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Wed Mar 23, 2016 10:54 pm

If you open the direct URL for the images, can you see them?

eg... http://ausrotary.com/download/file.php?id=50244

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spirit r
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by spirit r » Thu Mar 24, 2016 3:19 pm

KYPREO wrote:If you open the direct URL for the images, can you see them?

eg... http://ausrotary.com/download/file.php?id=50244
I got this picture Sorry.I am not a member of the Australian Forum.
Screenshot_2016-03-24-16-15-23.png
Screenshot_2016-03-24-16-15-23.png (435.82 KiB) Viewed 5233 times

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Hobbawobba
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by Hobbawobba » Thu Mar 24, 2016 4:43 pm

Ahh yep it wasn't working for me either. Then realised I deleted my cookies and wasn't logged in on Ausrotary. Logged in and all is fine now! Time to get reading :D

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KYPREO
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Re: 1985 Series 3 restomod with s5 13BT on LPG, R&P steering

Post by KYPREO » Thu Mar 24, 2016 10:06 pm

Ah i see. I think it's because the photos were originally attached to posts viewable to registered users only. I'll get that fixed up!

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