Charlie's no budget mid engine build: *Codename:BlakBishop*

[wytbishop]

V8's are boring. I've been reading a lot about the Nissans. Now there's a convoluted bunch of engine options. The RB26DETT is the real beast of the tuner world, but it's looooong and there's not obvious/easy way to mount it in the back of a car. I think I've settled on the VG30DETT and inverted Posche G20 trans. The VG is readily available, makes 300hp stock and it's fairly compact. The G50 trans is expensive but small, easy to get and super strong.

My design will be more like a standard car. I don't want to build anything exotic. I have looked at the lowcost forum and this guy...http://www.grabercars.com/ The lowcost is not at all my style and I think the graber guys car is cool but too wannabe exotic looking....and not powerful enough. My car will be a coupe. Shortish wheelbase, wide track, under 2000lbs. and over 400hp.

[Nd4SpdSe]

My truck is a VG, VG33. The VG30 guys seem to like to use our crank, and there's even a hybrid setup to make a VG34 which I would love to do (and supercharged!), but there's many types and hybrids in the VG series, there's plenty of possibilities. Look at J-Beef's 300ZX, he's making over 500hp in his.

There's actually a 3-rotor Delorian, he's using a Porsche trans for it.

There's also the Sr20 in the Pulsar GTiR, it's AWD, but wondering if it's feasible to go FWD on the trans, like the EVO's can do RWD.

There's also a guy that did a KLZE Bug, he's got some decent details posted, I remember info and diagrams on mating the stock trans I believe it was to the ZE. Could look alot at Bugs and Dune buggies, you may find some intersting info on transverse RWD mouting.

Could also look at the Intrepid with the longitudinally mounted FWD V6, lol

[wytbishop]

SO!!! some decisions have been made and the modeling process begins. The engine will be a VG30DETT. This engine was originally made for the 300ZX Twin Turbo both in Japan and the US from 89-96' and is rated at 280-300hp depending on the source you're reading. By all accounts it is capable of 1000hp on the stock bottom end, but I have no intention of going there. I just want to do 400-500hp comfortably. My first choice would be to mount it to a 94 Maxima SE 5speed because it's cheap and it will be quite compact and allow me to mount the engine almost directly over the rear wheels, but I'm not yet totally convinced that the Maxima box can handle that engine and I still need to prove to myself that it will definitely bolt up. Second choice is a Porsche G50 trans. This is a monster gearbox easily capable of handling whatever power I put through it. It also gives me a couple of options for mounting as it can be inverted. So I can mount it behind the engine with the gearbox inverted or in front of the engine with the gearbox upright. Problem is it's very expensive and forces me to mount the engine either in front of or behind the wheels which is not as ideal.

I will use a Miata donor for the hubs, spindles, steering rack and column. There's lots of cool upgrade options for the Miata brakes and suspension parts so that will simplify things and the miata is a nice handline car so it's a good launching point for the suspension.

So let the fun begin. I'll update as I make progress with the design.

Thanks for all your input.

[Flyer]

If the Miata's body is in rust free condition, dibs..you know you can separate the drivetrain/suspension goodies and the body easily, right? >_>

[wytbishop]

It's unlikely that I'll find or want an entire car. And if I did it would most likely be a rusted out piece of crap...but you can have dibs if a miracle should occur.

[ethand]

Wow, I like the sound of this! I so can't wait to hear more progress on this one!! Let me know if this project gets a worklog on here somewhere - I'll be following it!!!
Perhaps you could steal like one small part from an MX3, so it can get a proper WL on here
Also, let me know about a price of a clone shipped to Australia haha

[wytbishop]

I spent most of my time over the Christmas holidays working on design layouts and fabrication research and I have taken a slightly new tangent. Rather than a tubular spaceframe design I have decided to do a carbon fiber semi-monocoque.

The main cockpit will be an assembly of carbon fiber mouldings. The roof, and front and rear bodywork will all be CF as well. The front and rear subframes are still taking shape but I suspect they will be tubular steel. I have done a preliminary design of the cockpit mold so that I could do some basic costing. I now understand why cars like the McLaren and Zonda are so expensive.

Materials to make the plug (which the mold is made from) will be about $500 and it will likely take a few hundred hours to make the plug. About $1000 worth of fibreglass and resin will be required to make the mold and about $5000 worth of CF fabric, resin and honeycombe material will be used on the part itself. So not even considering an hourly rate for my time it will cost about $7k to make just the center section of the car. There is still the roof, dash and front and rear bodies. I estimate that to fabricate the entire chassis and body will cost $25k and take quite a lot of time.

I think i'm in the neighborhood of $45-50k to build this car, so for now I'm focused on the design. I'll figure out where to get the money later. I have modeled some parts and I'm working with a couple of different layout options deciding between mid or rear engine. Engine will still probably be the Nissan VG30DETT and tranny will be Audi 01E 6sp.

The exterior appearance is still very much up in the air. In my mind I would like it to be reminicent of the MX-3 but with a more modern look. I may incorporate MX-3 headlights and taillights or something like that.

I'll post some renderings once I have something that looks good.

[onlytrueromeo]

Or you could stick with the spaceframe, and do this:

http://www.youtube.com/watch?v=OKRSzzSWF6U

I am interested to see your concepts, sounds awesome so far.

[wytbishop]

You know as a matter of fact when this idea first went through my mind that very video did pop into my mind for a second.

but no.

[Nd4SpdSe]

If you're doing CF, why not do an aluminum frame to save more weight?

[Ryan]

at doing carbon fibre. you're right, if not conservative on the costs.

#1 - the cost is PHENOMENAL. I'd assume you're doing pre-prag, and you won't get it cheap, unless you find a VERY generous company who will give you their expired crap. Next, you need someone to donate the use of their curing ovens. A big enough one for whatever parts you plan on making.

#2 - all CF, pre-prag or wet lay, lays like fibreglass, so you need a mould. How will you tackle this? CNC? more money. hand carved? Well, you better be an artist, and have about 6 months of unemployment on your hards.

#3 - you need a core structure, once again, probably donated, although this is probably going to be the cheapest part to buy.

#4 - laying up is a MASSIVE task, and you're on a timeline, you will NOT be able to do it with only one set of hands. It has an open air expiry, too.

#5 - you need a vacuum pump and the special high heat plastic to squeeze the CF into the proper shape, you can't just lay it and leave it like FG.

#6 - more chemicals like release agents and the tack to hold the plastic together...

#7 - IF you get it all done, it will look like crap on the outside (Zonda's is AMAAAAAZING.) and you'll need to body fill/paint it anyway.

I respectfully suggest you ditch the idea.

[marcdh]

To balance that a little...

Aesthetically acceptable CF isn't that hard. I've made a few bits and pieces with my vacuum pump kit. The vacuum plastic/release agents etc are cheap enough. With practice you can get satisfactory results that are on par with the ebay/china CF bonnets for our cars. Where I wouldn't like to take my wet lay up or infusion skills is to something structurally important. CF rad support is the height of my structural DIY CF parts. Resin infusion is a bit of pain to setup but the parts are certainly lighter and stronger, avoiding surface air bubbles is a bit tricky though. Hair dryers help There's videos online of people making kayaks etc with simple enough kits. Mould making is tedious but can be made fairly cheap as there's little point wasting expensive epoxy resin on them and FG is cheap. However that's assuming you have a plug to make the mould, and your mould is going to be rather huge. The tooling gel coat is quite dear though, as is high temp resistant epoxy.

An early stab at CF for a local honda owner:


Looks fine and I could stand on it, but I wouldn't want it for any structural integrity

What's pre-prag anyway?

[wytbishop]

Wow Ryan...it's almost like you think I would not have given this any thought. I should think you would know me better than that.

First and foremost...I am neither on a budget nor a timeline.

1. I will not be using pre-preg because it is expensive and I don't have, or feel like building an autoclave...although I did look into it. Everything will be done wet. I am tentatively planning on 7 layers of 5.7oz and 10.7oz CF with honeycombe in strategic spots between layers 4 and 5. The real strength of the part owes much more to the shape and design than the material, but I'm planning to overkill the monocoque a bit. Modern epoxy and polyester resins are designed to be cured at anywhere from room temperature to 250ºF. Some ask for 310ºF but they are specialty materials. There are numerous exampes of DIY'ers manufacturing and curing parts in a variety of home made "ovens". A space heater and $40 worth of rigid insulation taped together with duct tape to build a 4'x4'x8' box can easily reach 250ºF and stay there for 6 hours.

2. The plugs will be carved by me, by hand from polystyrene foam, then filled with drywall mud, sealed, primed and polished. Yes, I am an artist and yes it will take many months. The molds will be fiberglass...I expect they will have to be ~5/8" thick to support the size of the parts I will be making.

3. Polyurethane honeycombe sandwich material is the least costly part of the construction and I will require less than you think.

4. Layup will require many hands. I am designing the structure to be assembled in pieces and bonded together. Did you know that the Zonda monocoque is constructed of over 200 separately laid up CF pieces? Still yes, I will need help. Luckily...people like me.

5. & 6. Gelcoat, mold wax, PVA release agent, peel ply, absorbant, bagging material, tape, fittings, pump...I know.

7. No...it won't. It will look amazing. Now you're being kind of a jerk with this one. Plug and mold preparation are the determiners of the quality of the finished part and your assumption that I am somehow incapable of doing this well is a little insulting.

As I said I expect to spend $25,000 on the CF structure and body. The monocoque center section and roof/A pillar will be the only structural CF parts. The body, doors, etc. will be much thinner and use far less materials. The reason Pagani or MacLaren would quote $350,000 is that they are considering $100/hr for the 3000 hours of labor and they are using pre-preg and very large expensive equipment. I have the luxury of charging myself a very favorable shop rate and using proven low cost methods to acheive the same result.

The most costly component other than all that, is potentially the transmission. The most common gearbox used to put front engines into rear engine chassis' is a Porsche G50. By the time you source one, pay the core cost and do a bit of work on it to make sure it's sound, it's a $9000-10,000 piece. The alternative, which is less sturdy but still stout enough for my use is an Audi 01E gearbox. Build by the same company, Getrag they are much easier to find and can be had, already cryothreated and reconditioned for $4k-ish.

The running gear will be mostly Miata stuff. The front subframe will, I think, be a modified Flyin Miata V8 tubular piece. I will have to modify it to fit it to the monocoque and support the fuel cell and other components that will be housed in the front of the vehicle, but the miata front control arms, steering rack, etc, will all bolt straight up and at least that way you know you have a strong starting point for a good handling front end. The rear end will be custom. Axels will be custom.

I still think $50k will cover it. Time will tell I suppose.

[wytbishop]

To balance that a little...

Aesthetically acceptable CF isn't that hard. I've made a few bits and pieces with my vacuum pump kit. The vacuum plastic/release agents etc are cheap enough. With practice you can get satisfactory results that are on par with the ebay/china CF bonnets for our cars. Where I wouldn't like to take my wet lay up or infusion skills is to something structurally important. CF rad support is the height of my structural DIY CF parts. Resin infusion is a bit of pain to setup but the parts are certainly lighter and stronger, avoiding surface air bubbles is a bit tricky though. Hair dryers help There's videos online of people making kayaks etc with simple enough kits. Mould making is tedious but can be made fairly cheap as there's little point wasting expensive epoxy resin on them and FG is cheap. However that's assuming you have a plug to make the mould, and your mould is going to be rather huge. The tooling gel coat is quite dear though, as is high temp resistant epoxy.

An early stab at CF for a local honda owner:


Looks fine and I could stand on it, but I wouldn't want it for any structural integrity

What's pre-prag anyway?

Quite right Marc. One of my first purchases will be a small starter kit so I can do a little simple practice making bits of things. I also want to do some stress testing of a few simple parts to determine strengths of things.

Pre-preg is CF fabric that has been pre-impregnated with heat activated resin. It is kept frozen by the manufacturer, but these days with newer resins that are only activated under heated pressure it has a shelf life of around 12 months at room temp. Even though you're not buying your own resin it is quite a bit more expensive than wet layup and can only be properly cured in an autoclave.

[wytbishop]

Changed the topic title.