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Monster Miata - Down Under!

Old 03-19-2018, 10:07 PM
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Cool. Thanks for the explanation. Looks similar to another brace I saw posted here. I like your xmember braces too. I did the hole through the passenger side floor, but I like your version better.
Glad that my build helped you. I had a long thread here somewhere where I asked questions along the way. Lots of good info there provided by the great folks here.
Can’t wait to get mine out of storage. We’re suffering through the last little bit of winter here.
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Old 03-21-2018, 09:33 PM
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Hi Brad,

Here are some better shots of the brace...I got it up on a hoist

C

ost is $9200
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Old 03-21-2018, 11:11 PM
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Thanks for the pics. I’m planning on making a heat shield for the slave, so maybe I’ll try this too.
I’ll be chatting with you when I build my next motor (possibly next year). You seem to be pretty smart about the 5.0.
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Old 03-22-2018, 12:18 AM
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Originally Posted by MX-Brad View Post
Thanks for the pics. I’m planning on making a heat shield for the slave, so maybe I’ll try this too.
I’ll be chatting with you when I build my next motor (possibly next year). You seem to be pretty smart about the 5.0.
Sure thing, I have built heaps of them in my time. They are a good engine, they just need good cam, heads and intake. Happy to help you put together an engine plan..

In addition I have engine modelling software (dynomation). I can even spin one up with the combo you are thinking and see what it will do in the simulation. On my engine it predicted 340Hp at the wheels..I made 335hp with a bit of wheelspin...so 340Hp is bang on the money
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Old 03-22-2018, 09:23 AM
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The more I look at your pictures the more impressed I become with your build.
Little details like the Mazda emblem on the valve covers just show that you spent that last little bit of time and trouble to make it as perfect as possible.

With your transmission & rear end gearing & tire size what speed are you getting at redline in each gear and what rpm are you getting at highway cruising speed?
Since I am debating and planning my next Miata swap with one consideration being to use a different transmission it is of interest to me. Will definitely staying with an LS engine but the transmission and differential you are utilizing is a possibility.
Speaking of engines, what were your reasons for going with the engine you chose?
Presumably thing are different in the land down under but I do know that the Holden V8 engine is an LS so they are available but for all I know they could be a big cost premium.
Here in the USA the LS based engine is super inexpensive and available due to the wide range of vehicles using them.
Pretty close to half the pickup trucks on the road are General Motors products with LS derived engines under the hood.
Sure wish we had the Ute here cause I would have one of those instead of a hotrod Miata.

Something else that I have been wondering is if you have any plan to keep your intake air cooler than the under hood temperature?
As best I can tell from the picture your air filter is just open to the rest of the engine bay.
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Old 03-22-2018, 09:02 PM
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Hi BG,

Thanks for the kind words. I did try my hardest to make everything as OEM standard and looking as possible. I did not want it to be better than OEM, just factory level detail and quality. It is pretty hard to make everything perfect when you are on a limited budget, but there are many things that can be done to make things look "OEM clean and neat". That is what i did essentially. I made sure I used as much of the factory stuff as possible, grommets, brackets, cables, connectors etc. It makes a difference when you add everything up. The Mazda logos on the rocker covers were not hard to do...but were a little tedious as they are Trickflow cast rocker covers. They are embossed with a the Trickflow logo from factory and I had to grind it all off (very messy, cast alloy went everywhere!). I then used metal reinforced fibreglass to make a small flat mounting platform for the Mazda Symbol as the surface is not flat there and the logo therefore wont stick. After i made the little flat area and sanded them back a little, I covered them with black VHT Wrinkle paint.

I am pretty happy wit the outcome, it fools a lot of people who look under the hood, as they cant really tell what engine it really is (Perfect!)

As I drive the car everyday it is not worth the extra effort or expense to make it look better than OEM. Plus the OEM look appeals to almost everyone, its a universal kind of presentation that works.

So I am very happy that you like the outcome and I really appreciate the kind words of support...

As far as the gear ratios, Diff ratio, Tyre Size and RPM goes the table is as follows:



On the Highway I am getting about 2000 rpm at 70MPH. This is a really nice cruising speed for the engine provided that the camshaft is matched. My cam is just on the start of its power ramp at this RPM which makes it feel crisp for overtaking as you squeeze on the throttle to pass other cars. There is no need to change gear, the full torque of the engine is there from about 2500 rpm to 5000 rpm so you just squeeze the throttle and ride the torque wave.

The reason for me going with a Ford 5.0L is four fold. First, I love Fords, enough said there!. Secondly, I know these engines very well and can build them with my eyes closed, so I built this one. Thirdly I had the full Trickflow top end available to me form another identical engine that I sold (so heads, Intake, TB etc), so its cost. Fourth is the most important reason, Legislation. The engine size of the Ford engine makes it possible for this conversion to be legal in Australia (only just!). Maximum engine size allowed in this vehicle is 5.5L, thereby removing many other engine options (i.e LS).

LS engines in Australia are plentiful and priced well. If I had a choice I would get an LS engine without question, its newer in design and lighter. Plus it would have been cheaper to get one with low miles than build the new Ford engine. However the fitment of the Ford engine is easier (no tunnel mods...which are a big no no if you need the car to be legal) and they afford you more room in the engine bay. Australia is in many ways quite draconian with its laws around vehicle modifications so things like modifying tunnels and inadequate clearance are frowned upon. Things have improved but it is still a minefield for the uninitiated. Most people give up as they do not know how to approach things, something as simple as not putting wiring through a grommet or having adequate clearance in some places can invalidate a car from being legally registered.

As a Mechanical engineer, I worked for the car companies (GM, Ford, Toyota) as a steering and suspension designer, I know what the registration authorities will look out for as I have gone through the legislation carefully for each and every modification that I have made. It is a long, convoluted and in many parts of legislation it is unreasonable and lacking any kind of physics in its approach. This is very frustrating as if you want to do something ever so slightly outside the exact legislation the process can be too hard. In the USA you are all quite lucky not to have this sort of Nanny State antics making your project a painful experience

So that's why I settled for the little ol' Ford 5.0L, it is also easy to fit, quite cheap, reasonably reliable and readily available. Also servicing is a DIY breeze...With a decent set of heads, cam and intake they can be made to deliver power. However the one thing that hurts them is the cast iron block it is heavier than the alloy block LS engines. There are Ford Alloy blocks available (Dart, Ford Racing) but they cost a lot of money and if I was richer, then yes I would get one for my builds...it only weighs 85lbs !

And yes the Australian "Ute" is a great variant, it drives like a normal car but gives you the versatility of a small pick up truck. Check out the Holden HSV variants for some good reading!! They are very popular here in the modified car seen, some are supercharged, turbocharged..its an Australian culture thing! As Australian as a Koala!

Yes you are very observant and have spotted my exposed air filter (yuk!) !! I am in the process of making an Airbox/Shroud to stop the hot air from hitting it. I will also try and get a cold duct into the airbox shroud from somewhere. There is not a lot of room in there and as such I am still developing that solution. I initially tried to get a mustang cobra air filter pod box but I wasn't able get it to fit..it was too big. The air temp is something that needs to be addressed, as the engine is high comp it needs to stay as cool as possible. I might measure the temperature at the air filter there one day to see what it is and I will then remeasure it with the airbox in place to see if it has made a good deal of difference. So far I have not had any detrimental performance or engine behaviour with the expose pod, BUT best practice dictates a sealed airbox for smooth airflow entry to the maf for accurate readings.

Cheers

I will post up some pics once I get the airbox thing sorted out.
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Old 03-23-2018, 09:34 AM
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Thanks for the response.
All of your discussion points make sense.
Here in the US the small pickup V8 Chevy engines are 4.8 & 5.3 so they would ne usable within your size restrictions.
The 5.3 can even be gotten with an aluminum block from some Cadillac SUV's.
I even know of one guy who destroked a 5.7 to get an engine that revs like an exotic.
Don't know his redline but based on the sound it must be somewhere above 8000 rpm.

You have lots of restrictions that don't make sense but hopefully they are consistent within Australia.
Here in the US each state has different restrictions with California being one of the worst.
I am lucky being in Oklahoma because the state does not even know or care that I have done a swap.
For insurance and registration purposes it is still a slow little 4 cylinder.

For the cold air intake you might take a look at the Yellow Submarine LS build.
Originally he routed his intake so that the air cleaner is in the area in front of the front fender where the fog lights would normally go.
The bonus is that you get consistent cool air because the opening in the front that used to house the fog light works very well.
He notched the very front of his box frame to get clearance for the round tube but when I was considering doing it my idea was to fabricate a rectangular duct that would flow a decent amount of air and lay right against the box frame on the driver's side without the need to do any trimming.
https://www.v8miata.net/general-moto...ar-2911/page9/


As a variation on that you could probably work up a duct to feed cool air into a box located inside the engine compartment but it seems to me that would be doing double work over simply figuring out a direct duct configuration.
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Old 04-22-2018, 06:46 PM
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Hi John, I take you got the weight over 1100kgs to engineer the motor as per the VSB14 rules?
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Old 12-17-2018, 12:29 AM
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Originally Posted by kaboose View Post
Hi John, I take you got the weight over 1100kgs to engineer the motor as per the VSB14 rules?
Hi Kaboose,

Yes I did. I finalised all the engineering this month. it was a 14 month journey but I am 100% legal on every front !!
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Old 12-17-2018, 10:57 PM
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Nice!! I'm hoping to do a NC 6.0 LS at some stage down the track so its good to hear an mx5 has been engineered without going the ICV route.
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Old 12-17-2018, 11:13 PM
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Hi Kaboose,

The Tare weight listed for the NC Series is somewhere between 1062kg-1101kg according to Redbook. If you wanted to do a 6.0L LS the Tare mass would need to be 1200kg in order for it to be compliant. Unfortunately I think that this is too far away from the mark to be signed off as a 6.0L. The 5.3L LS could be an option for you and they can be made to make decent power too..
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Old 12-18-2018, 12:51 AM
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I've got an online brochure here for a series 3 NC and the heaviest listed weight is 1179kg, still not 1200kg so I'd have to talk to VASS engineer to see if options or anything can tip it over 1200 or not.
Congrats on the build too, looks great!!
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Old 12-18-2018, 05:46 AM
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Hi Kaboose,

Just make sure that you are referencing the TARE weight and NOT the KERB weight. Heaviest NC TARE weight i could find was 1140kg. Multiplied by 5 gets you a maximum engine cc value of 5700cc. So a 5.7l LS engine will be ok, provided everything else in vsb14 is compliant and legal.

I hope you can get it over the line. It's a fun thing once its legal and running .I love mine..😁😎👍
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Old 12-18-2018, 09:42 AM
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Good Lord, never really appreciated how lucky we are in the States. Great conversation on being legal down Under.

Good Luck,
RonR
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Old 01-10-2019, 11:05 PM
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Originally Posted by 5.0MX5 View Post
Good Lord, never really appreciated how lucky we are in the States. Great conversation on being legal down Under.

Good Luck,
RonR
Hi Ron,

You have no idea how draconian the Australian laws can be. there is a reason for this in that they want to ensure that the cars that are modified are safe for people to drive...i.e. stop, steer, don't pollute, not noisy, too low, pose a fire hazard, dangerous in a collision etc.

It is a good system...but it is utterly unforgiving to anyone who is uninitiated with it.

Some of the stories that the certifiers told me about were quite hair raising i.e. cars attempting legal compliance with horrid brakes that locked the rears first, rubber fuel lines that run right next to exhaust systems, etc etc. So the safety net needs to be there for those cases.

I am happy to have done it the right way in the end...but boy o boy they do NOT make it easy, even for me and I knew what to expect. A sample…

1) Full Emissions test (not easy to pass with a modified engine)
2) Full Brake and manoeuvrability test
3) Full Noise Test
4) Full Chassis Torsional Rigidity Test
5) Complete modifications listing and approvals needed from brakes to grommets for wiring
6) Finite Element analysis report for chassis structure (yep..bet you never guessed that one!)

The list goes on...I get bad memories just thinking about it haha

Overall I got through without too much drama in the end but that was because I had done 14 months of research and provided a massive report to the certifier with everything that he needed to issue the authorities with.

The USA does not have this level of governance...but I think a happy medium point would satisfy both ends of the equation.

It is all over now and I am just happy that my dream to drive a V8 MX5 is now my daily reality!

Cheers
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Old 01-11-2019, 01:08 AM
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Until your next v8 conversion
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Old 01-12-2019, 04:05 PM
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Originally Posted by kaboose View Post
Until your next v8 conversion
Which will be an LS3 V8 Porsche Boxster
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Old 01-12-2019, 07:19 PM
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Nice!! I can hear the purists now though
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