Help with LS1 v8 conversion

[hks_kansei]

The bullet roadster is 40+ grand for a reason. I respect those that have built a ls1 mx5 but I could never justify the cost and weight up front.

My understanding is that the weight difference is not that large since the LS is an aluminium block, where the B6/P is iron.


I'm finding it hard to get actual figures, since people seem to only be reporting LS weights with the auto gearbox attached (which isn't really relevant to an MX5 application)

[Dan]

If you want someone else to build it I'd call the MX5 specialists in your area and get their thoughts since they are going to be dictating a lot in the part selection process and be able to give you an estimate on parts/labour. They are probably want to make sure you aren't tyre kicking before they spend too much time making you a quote though.

If you are building it yourself there is a pretty good video guide here which shows you what's involved https://www.youtube.com/watch?v=LAcXtvhqTaY and he has a parts list on his site here http://www.v8mazda.com/parts_list.html

If you aren't building it yourself and it's a road car I'd seriously consider buying a mid-2000's SLK55 AMG (~50k) since you'd get a much better resale value relative to the cost and the car is designed around the 5.5L V8.

[Regie]

The bullet roadster is 40+ grand for a reason. I respect those that have built a ls1 mx5 but I could never justify the cost and weight up front.

LS is 30-40kg heavier than the Na/Nb motors

[bruce]

It has been explained;
Engine capacity is too large for the weight of the MX5. It is a Federal standard, thus no Engineer in Australia will pass it.

Cars like the Bullet are like ICVs, everything has been complied from scratch eg. body, lighting, seating, etc. Bullet is/was a manufacturer.

[speed]

The bullet roadster is 40+ grand for a reason. I respect those that have built a ls1 mx5 but I could never justify the cost and weight up front.

LS is 30-40kg heavier than the Na/Nb motors

I'm surprised. Is that engine to engine or mx5 with air con power steer etc and LS1 without?

[hks_kansei]

The bullet roadster is 40+ grand for a reason. I respect those that have built a ls1 mx5 but I could never justify the cost and weight up front.

LS is 30-40kg heavier than the Na/Nb motors

I'm surprised. Is that engine to engine or mx5 with air con power steer etc and LS1 without?

probably engine to engine.

Mazda B series is iron block, LS is aluminium.

Iron is 7.87 grams per cubic cm
Alu is 2.7 grams per cubic cm

So alu is roughly 2.9 times less dense than iron.


On top of that the LS is a pushrod engine, so you've got only one camshaft (granted with the weight of the rods/rockers etc)

[oztrackdays]

Engine Weight of LS1 is not the issue.

Tremec T-56 is a monster gearbox it's +40 kg in the gearbox.

other Kilo adders

+ Big old 8.8 inch diff
+ Bigger Propshaft
+ Beefier Half Shafts

and the list goes on and on.

If you want a V8 the weight won't be the issue but the number of Mazda parts you can retain is rather low.

[Dan]

I think a V8 for most people is more about the novelty of having a V8 in an MX5.

The logical way to power is a turbo and if you are concerned about weight that is probably the most weight efficient way to go.

A Kswap + turbo is likely the best of both world but $$$...

Sent from my SM-N9005 using Tapatalk

[manga_blue]

All the same, if I wanted big V8 roadster I'd just go out and buy a 2 seater Merc SL500. It would give me a cheaper car that's ready for the road and will hold resale value.

[MrsB]

Unlike most people on here I have done all the structural changes to an mx5 chassis - widening the transmission tunnel - cutting and reinforcing the frame rails etc for a race car and then ran into some political issues and changed tack. You will never get it registered as the capacity to weight is against standards which is why the bullet which is a poorly thought through evil handling lead tipped arrow has a 4l lexus v8 instead of the LS. What people say about weight is correct - they weigh about the same as an mx5 turbo and if you use the FM / v8 Roadsters kit they handle well too. Expect to spend around 40 - 50k in the process.

The flyin miata kit comes with complete instructions and will cost you about 16k freighted without the motor/box and diff.

Cheers

Owen

[hks_kansei]

I do recall there was one road legal LS engines NB in Vic, built by someone Pitts?

But the work he needed to do to get it on the road was pretty intense, basically having to gut the whole car and use a lot of Corvette bits, then register it as an ICV (Individually Constructed Vehicle)

[davekmoore]

Move to Americaland.

[PeterB]

A mate has installed a LS1 and 6-speed into a Series 5 RX7. From memory the engine/gearbox with ancilliaries were around 295 kg.

The total conversion from turbo rotary/5 speed to LS1/6-speed was about a 60kg weight increase, but front rear balance changed little as the heavy gearbox centralised the extra weight and the front intercooler was removed. The weight increase in a MX5 would be more, as the rotary turbo is a heavy setup. The RX7 already had the bigger turbo diff and brakes, which didn't need changing, whereas a MX5 one would need an upgrade.

He used a kit from the states, and although listed as being for a RHD, required a fair bit a fiddling to get it to fit. He did retain the power steer and a/c which complicated things a bit.

Biggest issues were sump clearance (used an imported corvette sump), exhaust fabrication (he did it himself, but was quoted about $5k to build commercially), clutch set-up ( RHS head fouled the clutch master cylinder, so he built a clever bell-crank set-up), radiator/water flow and wiring the GMH computer into the RX7 (stayed standard to pass epa).

I would hate to add up the hours he and his son put into the conversion, but as he had the skills, by building himself it was a very affordable project. He bought a complete wrecked commodore as a donor, which was required for the many little fittings/parts he needed. It would have been a nightmare if he had just bought an engine/gearbox from a wrecker.

Although I am a rotor enthusiast, the RX7 LS1 conversion is magic with endless torque and beautifully balanced to drive. As a heavier car than an MX5, it is engineered and registered and I would love one, but don't have the machining/welding/etc skills to build one.

The Bullet (Lexus v8 supercharged) that Barry Faux ran from Canberra for a few years was never a success, despite endless effort, and I don't think was any quicker than his supercharged 1600 NA6 it replaced.

My view - If you want a V8 Mazda - go RX7, if you want a fast MX5 - go turbo.

[Jeo]

Barry Faux used to have a Bullet? Things you learn.

[93_Clubman]

I do recall there was one road legal LS engines NB in Vic, built by someone Pitts?
But the work he needed to do to get it on the road was pretty intense, basically having to gut the whole car and use a lot of Corvette bits, then register it as an ICV (Individually Constructed Vehicle)

If you want it to be registerable, it's been done in Vic a few years ago, but had to be engineered as an ICV. Specifically John Pitt of Wheelers Hill (Vic) built, engineered & registered a couple of MX5 V8s in Vic:
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