Mid engine homebuilt supercar (Gruppe B meets Group 5 meets Grassroots)

In reply to bentwrench :

Sprint cars are pushing out 800hp+ using Winters 10" QC rearends.

The modern version of TransAm racers are pushing out 600hp+ using similar versions.

The ring can't be flipped on a Winters QC, the pinion nose has a bearing support that is asymmetrical, it would interfere with the ring being placed on the opposite side. Winters does make a reverse cut ring & pinion though.

The PPG gearbox is 6+R.

It was designed for drift cars, and many of those are making 500+lb/ft of torque, N/A, turbo and supercharged.

I can't give a torque number, but I can tell you that those rearends are very stout and there are many, many options, from IRS bells, lockers, LSD, helical cut QC gears, reverse cut ring & pinions, etc.

In reply to Gingerbeardman :

Yep BUT 18,5 is   Un Atainable,    and several Dirt Tracks Close and I have a Super T 10 Pretty sure there's a Bent Q C  Around, Heck I Have to check this out now . Could be the Answer to the Answer, Stick it in the back of the C4 Add Boat Big Block Stir and stand Back.

Gingerbeardman said:

In reply to GTXVette :

You mean like this?

https://www.ppgearbox.com/product-page/quickchange-transaxle

$18,500

That's all kinds of neat. 

In reply to GTXVette :

T10/Muncie/Saginaw has an 83mm shaft spacing. (3.26772)

10" quick change rears have a 3.5" shaft spacing. 

You know what else has 3.5" shaft spacing? G-force 5-speed, Liberty 5/6/7 speed, Richmond 5 and 6 speed.

Mark Williams company has all the couplers you'd need to mate up the different spline combos.

It's doable, but it's not quite as straightforward as people seem to think. Unless you already have a lathe and a mill at home and a ton of hands-on experience with machining shafts, splines and gears, you'll soon learn how expensive custom is and how important runout, parallelism, and true (square) is when DIY'ing a transmission or transaxle.

I used to dream about doing it all myself, but I realized I'd be money, time and energy ahead to simply start a savings account and let the pros do the work.

I almost chuckle when I hear people complain about how "expensive" mid engine transaxles are...as if a $3500 T56/T6060, a $1500 flywheel/clutch, a $3000 rearend, a $1000 driveshaft, and $1000 for 2 axles for an IRS aren't. 

The cheapest DIY transaxle would be a traditional 4 speed with a 27 spline output mated to a C5/C6 Corvette diff with an adaptor plate to mate them together. It pushes the diff about 15" from the back of the block, but it's almost exactly as long as the old Corvair transaxle was when used with a SBC.

In reply to GTXVette :

This IS the cheapest DIY transaxle you'll ever build:

You need a transmission with a 27 spline output for C5 and non Z06 C6 diffs.

You need a transmission with a 30 spline output for C6 Z06 and C7 diffs. 

30 spline is traditionally a Dodge output count, 31 is Ford, 32 is Chevy.

For whatever reason, Chevy didn't go with a bigger output shaft diameter, which would open up the options for DIY'ers.

Of course, you can wire EDM the splines out of the pinion gear on the C5/C6/C7 diffs, but the only company I'm aware of that already has a known good file is G-Force. And they only go 27 to 30 spline. It might be possible to talk them into doing a 27 to 32 spline wirecut.

In reply to Gingerbeardman :

That may be cheap, but like a Crown Corvair, it moves the engine too far forward.

pres589 (djronnebaum) said:

The idea with the Fiero was that a lot of the basics are handled; you have an HVAC system, windows, wipers, etc etc "boring" stuff that takes time to sort out and do to make the car complete.  It seems to generally fit the bill described in the first posts of the thread.  There's still a lot to do but I think it's more of the stuff that the OP would consider good challenges; sorting the suspension, brakes, hubs, powerplant etc etc.  And Lancia Stratos-like flares done right on a late Fiero, with a warmed LS for soundtrack?  Come on.  Why not shave a year or two off of the timeline by starting with something already started?

 

To each his own of course, and I'm not capable of building much of anything, so take this all with a grain of salt.

This is my thinking, cut the front and rear off a fiero and build my own car from the tub

In reply to TurnerX19 :

Yes and no. It's 15" from back of block to centerline of diff. A 26" diameter wheel is 13" from center of wheel to tire edge. Cheat the axle angle a smidge, and the front of the tire is close to back of block.

Saleen S7 uses a 13" deep bellhousing attached to an RBT 6-speed (ZF based transaxle...like in DeTomaso Panteras and Mangustas, BMW M1, Maserati Bora, GT40, etc).

The Crown Corvair has plenty of room available, it's packaging dependent. Corvair=108" wheelbase. The problem is where the windshield base is fixed and the rear wheelhouse is fixed. If it were more cabin forward like most modern mid engine cars, it wouldn't be a problem at all.

That's the big problem with repurposing or reusing an existing platform. If you change what needs to be adjusted to make things work, it's a lot of work, and it'll look wonky unless you have a designer's flair.

If you build from scratch, TO PURPOSE, you can arrange furniture to suit your needs.

There is a cost to using available components...you're stuck with the dimensions they were designed with. As with all compromises, you pick and choose what you can live with.

In reply to TommyWants :

I think it's an awesome idea and not a bad platform to start with.

For ME, it's got too many compromises.

Even using available components: e.g.; Corvette or Solstice suspension, 4, V6 or V8 engine of your choice, transaxle of your choice ZF, Porsche, Audi, Subaru, brake packages, etc...

The front and rear subframes can be as involved or as simplistic as you're comfortable with.

So now you need a body...because the stock and aftermarket Fiero components won't fit the stretched wheelbase if you go longitudinal rather than transversal...and you CAN modify those components. It's not that composite work is impossible. Will YOU be able to design, sculpt, tweak, modify the body panels into something that YOU enjoy looking at? Because it's A LOT of work if you think it's ugly.

Or, god forbid, you choose a rebody...any number of kit car bodies that were designed for Fieros...are they what YOU want?

And if you want to modify the greenhouse (the glass) you're at a point where you might as well have started from scratch due to the amount of work involved...whether it's chopping, transplanting a different windshield, new door glass, etc.

Every platform has it's inherent designed-in flaws. Yes you can modify them. And there is nothing wrong with that.

But it is not a scratch build. It's modifying an existing car.

Do I think it could be cool? Yeah, I do.

Would I be interested in reading and watching that build? HELL YES!

Will I be doing that? Not unless my plans for my build go seriously awry or I am forced to use a much smaller budget than what I've currently saved for.

Which could happen. Life has a way of making fools of men and their plans.

TommyWants said: 

This is my thinking, cut the front and rear off a fiero and build my own car from the tub

Late 80s I remember seeing a kit done that way....I just can't remember the name.  They had 4 or 5 kits the were can am type race replicas and then the 1 fiero based more street worthy and a bit less expensive.  That's about all o remember other than it was a sbc in the pics and at the time I thought it looked decent.

In reply to Gingerbeardman :

I get your point about the Corvair's windshield position, but more to my idea is that 100" is a long wheelbase, already 8"shorter than the 'Vair. I do daily drive a transverse mid engine, and it is enough for my personal circumstance. I am very fond of the Ultimas I have seen, and they could not utilize the long bell housing. I do not have the responsibility or restraint to drive a car of the performance you propose except on the track  So I enjoy your project vicariously. I also have service time on a Mclaren M8, and several F5000 cars, so I get the dynamic. 

For the budget being discussed a twin turbo flat 6 and transaxle from a turbo 911 could be used.  You can flip it if you want it mid engined.  Porsche did it for the Cayman / Boxster so it’s all available.  

Turbo 911s can make insane power too.  

Envision a modern interpretation of a race 935 for the street....  or your own homebrew yellowbird. 

" The Red Beard Project " ,

           This thread DID start as His Own Build And a Budget Wasn't in the mix So he may well afford Porsche Parts, But I Have learned A Lot So Far, and want to Know more.

mke said:

TommyWants said: 

This is my thinking, cut the front and rear off a fiero and build my own car from the tub

Late 80s I remember seeing a kit done that way....I just can't remember the name.  They had 4 or 5 kits the were can am type race replicas and then the 1 fiero based more street worthy and a bit less expensive.  That's about all o remember other than it was a sbc in the pics and at the time I thought it looked decent.

Marauder br-x

Not sure if it's been brought up but would the 01e audi trans from the B5 S4's work? They hold pretty good power in built S4's and I'd imagine being converted to 2wd would put much less stress on them vs. awd. The B5 chassis are starting to get pretty old so it's not too hard to find parts from blown up cars for reasonably cheap. I know there's at least a few adapter plates that people have used to mate them to LS's.

+1 for if you use 180* headers

edizzle89 said:

+1 for if you use 180* headers

They look kind of cool but I don't think I've ever seen a dyno sheet showing they work as more conventional options....the primaries get way too long from what i understand.

Ford has/had? a flat crank in one of the recent mustang engines, 350GT?  with that engine standard headers are 180 headers but no similar LS options I don't think.  With a flat crank engine you also get to separate the intake and airboxes to create helmholtz chambers like all the sport bikes use so there is more HP available there too...not the an LS can't produce plenty of hp for a 2400ish lbs car.

In reply to Gingerbeardman :

You could end up with a very interesting build here. I'll just post up a few things I've learned from my own scratch build. Stuff to think about if you haven't already. 

-It's not easy to make a car in a pleasing shape. The profile, the proportions, the silhouette, very easily look 'off'. This element of design is, I believe, the greatest challenge in a scratch build. It's also super important. Perhaps the most important thing about a car, to someone who loves cars. 

-Plan to build it twice. The first version probably won't be right. 

There is a great build on 914World with a Cayenne twin turbo v8 running a flipped Porsche 6spd.  Adapter plate is 3/4-1" if I remember right.  I do not know the lengths but he did put up Dims of the transmission.  Plan is 1000hp-ish.

http://www.914world.com/bbs2/index.php?showtopic=206097

So GBM , I See In The Pics W/ The Manual trans and c6 ish rear Has In 3 Pics 3 different Adpter plates .... So Any Body Have One Laying Around . also The Length of Parts You Mentioned Seemed off a bit so I went outside and Pulled Some Numbers,

 My Super T-10 Has A case Legnth From Face To Face of 10 inches and an output shaft with 32 splines, same as a turbo 400  My Bell Housing is Basic GM At 6.5 Inches, Add Adpter Plate And Rear Housing And With A BB Chevy  I Am looking at 55 inches .

 That Intrudes Pretty far Into The Seating Area, So What To Do.

 I Had Planned On Shortening The W B A Few Inches anyhow But If I also Pick up the Body And Put It Forward On The Frame  I Have 22 inches to the back of the body that can become wheel wells and it would move the cowl forward for a seat or two, that would mean I could Shorten The Looong Nose On A  C 4 And That many inches puts the front wheels right in front of the Current Firewall Which Is Gone Anyway, 

Really Going To Need The Diff Right Behind The Clutch, Gearbox Aft Of The Diff

In reply to TurnerX19 :

100" is long relative to 80", but F1 and LMP are all over 115" and they're damn fast on the straights and thru the curves!

I've owned a handful of mid engine cars, from budget to exotic, and they've all had their draws and drawbacks.

First mid engine was a 1984 lime green X1/9 with black split stripes. Loved that car...most likely started my actual love affair with the mid engine platform, rather than the ubiquitous posters of the Countach, F40 and Vector that hung on my walls during my late single-digit years and through my teenage years.

Next came a 1986 Fiero GT with a 2.8L V6 and 4 speed auto. The slushbox was the only real letdown with that car.

Following that was a 1993 Toyota MR2 (non-turbo) hardtop (no sunroof) with 5 speed! That car REALLY impressed me. I'm 6'3" with looong legs and that car had plenty of room. Did not hurt that it was decently zippy and looked more expensive than it was!

Then came a tired 914-6 that came as a stripped rolling chassis and a storage shed full of parts. After a quick 6 month rebuild, I tore around town and base until the itch came to unload it. I never really fell in love with the car. As dumb as it sounds, it was like dating an ugly chick who's fun in bed. I just couldn't get past the looks. And sadly I sold it too soon for too little. That car now trades for $45-65K!

I thought I had finally made it when I purchased a wrecked 1986 308 GTB! Sadly that car not only nickled and dimed me to death ($5k here, $10k there...) but once it was brought back to proper condition, my buddy's wife's 2005 Nissan Maxima out-accelerated, out-handled, out-ran and got twice as good gas mileage!!! Now I know why they say to never meet your heroes.

I missed out on a BMW M1 before they started selling for what they are actually worth, but I did purchase a Maserati Bora. I broke even after I sold that one, less than a year after I bought it.

The one car that I have kept since purchase is my 1979 Pantera. Ergonomics are terrible (for me and most people who aren't 5'6" with arms like a forward for a college ball team and legs like a female gymnast), the 351 Cleveland is relatively affordable to maintain, but also MUCH more expensive to repair, hop up or rebuild now than they were back in the day. I had the ZF transaxle rebuilt and a new CWP installed (stock was 4.22, new one is 3.55) and that REALLY opened my eyes to how expensive transaxles can be...a refresh (new gaskets/seals, new bearings, new synchro rings, and new CWP) cost $6500 in 2007. ZF Boxes in poor repair often sell for that on eBay...with rebuilds topping $10k PLUS cost of purchase.

My purest thrill isn't outright speed (if it were, I'd build a Bonneville car) but rather carving the multitude of mountain and canyon roads that surround me. I have over 500 miles of tight, twisty roads that start at 5200 ft above sea level and climb to 8-9000 ft elevation, all within 30-60 minutes from my house. If I'm willing to drive another 4-6 hours, I have another 1000 miles of similar roads available. 

In reply to AnthonyGS :

I have a healthy budget, but unless I buy a wrecked 911, that's a much more expensive proposition than you realize. And while I can appreciate Porsches for what they are, I've never really been a big fan of the watercooled flat sixes. Aircooled sixes SOUND better, even if you can make more power with the watercooled sixes.

As to Cayman/Boxster, only the 986 models used a transaxle that was based on the 911's. 987 and 981 chassis Boxster/Cayman use an Audi based transaxle.

I LOVE the Ruf Yellowbird! Too bad the Cayman wasn't available back then...the Ruf CTR3 just looks wonky with the way the sloping hatch and widened hips collide at the back.

A Ruf/Singer inspired 914 would be one helluva car and build. That would get a star in my Favorites bar on my laptop!

MY build is basically MY interpretation of an American alternative to Ferrari/Lancia Gruppe B offerings, with some Group 5 flair, on a Grassroots level. Yes, I have a bigger budget than most, but it's not unlimited funds, or a pro-build...it's ME in MY garage, using MY tools, MY skills and MY abilities. I'll end up with whatever I'm capable of building. And since I plan on keeping this for the rest of my life, it might (most likely WILL) get a series of refreshes, updates and improvements as I go along. Hopefully there will still be forums like this in the future, so I can share those with other folks too.

In reply to Gingerbeardman :

I hear, respect and like your plans.  I was just putting out ideas.  I have long plans for my 996 but its expensive.  I also have ideas for my 986 too.  And if anyone finds a 99 996 with factory aero and cheap, I need it.  I also need a cheap 97-99 2.5L Boxster.

In reply to GTXVette :

I hope I haven't discouraged you from doing a more "budget" build, as I think it IS doable, depending on luck, timing, available funds, platform, engine, suspension, and transaxle choice.

The 996 Porsche gearbox is relatively affordable, as they go for $3-5k on eBay all the time. They can have 2nd gear issues (most WILL develop this problem, as miles pile on) but there ARE fixes available. They need to be inverted, which mostly involves removing the vent in the top, sealing it, installing a new vent hole and vent in the bottom (now top, because inverted) and adjusting fill height and volume for oil (LESS).

Problem 1, those repairs often cost as much in labor and parts as the box purchase price. Problem 2, the gear ratios are wrong for an LS, 351W, Hemi, etc. unless you don't mind 1st gear as a granny gear, and cruising at 2700rpm in 6th gear at 65mph. The Coyote V8 actually has similar ratios in the Mustang, so it "should" be a better fit in that regard. Problem 3, the adapter plate, flywheel and clutch run around $1.5-2K.

The 997 Porsche gearbox (last of the 6 speed 911 boxes) also have 2nd gear issues, fixes are available, same issues listed above also apply. There is an aftermarket R&P from Albins in 3.00 ratio that makes the gear ratios much more V8 friendly.

Boxster S and Cayman S transaxles are the most affordable options with SLIGHTLY better ratios, but same synchro issues, same fixes available, same labor/part costs. However, there are Audi diesel OD gears available that are a direct swap that offer FANTASTIC cruise rpms, .53 and .56 ratios in 6th gear give you a sub-2000rpm cruise at 70mph with an LS V8.

If you're handy, can follow factory manual procedures to a T, not afraid to tear into a gearbox, and willing to do the work yourself, these can be a good option for the home-builder. There are vendors who sell OEM parts and rebuild services. It's all up to how much you're willing to spend and/or do yourself.

Non S transaxles are basically 4-cylinder Audi boxes. No parts are available and they aren't high-torque supporting. Basically "disposable" though cheap enough.

In reply to edizzle89 :

The Audi 01E is probably the most affordable and best geared transaxle available to the home builder.

Scott at Advanced Automotion sells rebuilt FWD 01E's for under $3k with stock differentials and with LSD for $3.5k, with optional diesel ratios for 3rd through 6 that fit the RPM range of LS engines.

First gear is pretty low...redline in an LS will have you at 38mph before the shift.

Interestingly enough, the center distance (distance between shaft centers) on the O1E is 77mm...same as the ZF transaxle. The crown wheel is only about 7.25" though, and has a hypoid offset, rather than centered like older Porsche and the ZF boxes.

The big cost with the 01E is the adapter plate, custom flywheel and Audi specific clutches. $1.5-2K from the usual suspects.

In reply to mke :

I have to admit, 180* OR 8:1 headers for me, are ALL about the sound, no other reason!

Interestingly enough, Ford sells the flat-plane crank and the special cams (different firing order) for the Voodoo engine, but not in a crate motor. It IS possible to build your own GT350 engine using factory parts, but you can't buy the specific ECU...so there would be the need to use an aftermarket ECU to make it work.

https://www.fordracingparts.com/part/M-6303-M52

For me, I'm all about bang-for-the-buck...a Coyote V8 built to similar specs to an LS will cost 150-175%. For me it would just be for the revs and the sound...I'm okay with sacrificing those wants for some substantial financial savings!

I'm aiming for 900kg...I'd be happy with 2500lbs! So far with the parts I've chosen to use, and some estimations based on known weights of other components, I'm going to be just over 950kg. Considering I'm not willing to go for exotic materials, I'm ok with that.