What car would you CREATE?

[Ecky]

Looks like Honda created my dream powertrain. Just read a news article on the Clarity hybrid, comes with a 1.5L Atkinson cycle lean burn i4 paired with an electric motor with 181HP / 232ft-lbs torque and a 17kwh battery. I'd probably downsize the electrical system.

[pete c]

Originally Posted by craysus

One I have been thinking about , but too time poor (And $$$ poor!!) to start on...

Budget Bracket $15001-->$30,000

Purpose of car : sports car

Proposed basis for car : Utilise a 1992-->2002 Mazda Rx7 - this is a lightweight platform, with superb aerodynamics, great handling, and importantly a good sized engine bay..Would require a transmission tunnel modification to fit gearbox of choice, and conversion of the popup lights to fixed units (Kits available on the market for this..in HID)

Engine of choice : Chevrolet Duramax 6.6 from as late a model as budget allows..Turbo of course..boosted slightly to give around 500hp which would make for a fun ride (The FD rx7 has a factory installed 13Brew engine (13B Rotary with twin turbos, intercooler etc), Conversion to LS v8 is a relatively easy thing these days with kits designed to bolt in...modifying from one of these to suit the big diesel should be relatively straightforward...expected weight difference to factory should be less than 200KG extra (440lbs))

Transmission of choice : TR-6070 7 speed manual from a 2014 corvette (0.42 final overdrive) - This is a big box, and would require some tin work to fit into the transmission tunnel..but would have the big torquey diesel ticking over at idle at 60mph ...for highway driving this should deliver outstanding fuel economy.

Drivetrain of choice RWD - Samberg diff conversion kit..replacing rear end with a cobra IRS kit is also possibly worthwhile to handle the torque, and give a broader choice of final gear ratios ..

Modifications required to above : apart from the fitment kit, and small amount of bodywork, the basic car and drivetrain are more than adequate for the task. Multiple 1000hp Rotary and V8 examples exist worlwide showing the chassis is strong enough for a simple 500-600hp diesel conversion. The Big duramax can handle 500-600hp without too many mechanical mods (injectors / pump / ECU), and for normal day to day driving tune could be configured to deliver a lazy 300hp for enhanced fuel economy..then turned up for some playtime on the track..

Expected mileage : - Wild estimate..but based on the corvette getting close to 40mpg with a petrol engine, on a less aerodynamic and heavier package..it would be estimated an easy 50mpg, and potentially with hypermiling driving upwards of 60mpg...from a 500hp sports car...

Expected cost to build: Base car $8000, Selling running gear $-3000, Used Duramax $4000, Transmission $3000, Conversion kit $5000, ECU / Ancilleries - $3000 - so around the $20,000 mark for a car that would return insane fuel economy better than some hybrids..and have 500hp, 10 second 1/4 mile times, and 300kph top speed...OBVIOUSLY if driven like a sports car, fuel economy would be poor however...Additionally, if some of the engine mods I am testing at the moment work as expected, applying them to this engine would result in a 40% further reduction in fuel..so maybe close to 90mpg from a 500hp car for ~$25k....

That excellent handling part of the equation goes to hell with the duramax lump replacing the extremely light weight 13B. I suppose you could beef up the suspension to handle it, but it will never get back to the balance it had with the rotary. I think a better route might be a heavily tweaked tdi motor.

[Fingie]

the RX-7 was designed with almost 50/50 weight ratio.... The duramax could quite surely turn it into a pretty crappy handling one, too front heavy.

[jcp123]

I'm not sure everyone here would appreciate my ideal build...lol

[craysus]

Originally Posted by Fingie

the RX-7 was designed with almost 50/50 weight ratio.... The duramax could quite surely turn it into a pretty crappy handling one, too front heavy.

Yes the FD Rx7 actually had pretty close to 25/25/25/25 weight distribution..

However..you will be surprised to know the 13B-REW (Twin turbo 13B Rotary) is actually an extremely HEAVY setup...
Replacing the 13B-rew with a LS3 actually results in a LIGHTER car...a few KGs only..but lighter nonetheless..and the v8 keeps the weight distribution in almost exactly the same spot as the 13B..

Now I am not stupid enough to believe a duramax is the same weight as an LS3, so obviously the big lump will change it a bit.., so lets do the maths (Roughly!)

LS3 = 211KG / 466lbs
LBZ =379KG / 837lbs

FD RX7 stock weight ~ 1298KG / 2862lbs

Assuming a 50/50 weight balance, and noting the engine is BEHIND the front axle (13B and the v8 both fit behind..infact the v8 has LESS weight infront due to not having some many ancilleries infront of it!)

we will work on 650KG / 2430lbs approx front axle weight based on 50/50 distribution..
As the engine sits behind the axle..lets work on 2/3rds the weight of the engine differential..

Approx 170KG heavier between the engines (13BREW/LS3 --> LBZ)
So if we allowed 2/3rds the weight, it would be 110kg extra on the front, and 60kg extra on the rear..

We also need to allow for the gearbox, which the allison is heavy at around 300lbs..(136KG), which would be DOUBLE the weight of the FD 5 speed box..so we need to add about 60KG in the centre of the car (tranny would put close to 50% of its weight to either axle)

Adding this to the 650KG per axle
Front 790KG
Rear 740KG
Curb Weight 1530KG
Giving 51.6/48.4 weight distribution....not many cars get to that


I hope the LBZ weight figure I got from Wiki is correct...

[niky]

Still not bad... but trust me, you will feel all 179 kilos of that extra weight every time you get to a corner. Not something you can't tune out, but it will still affect the handling.

I wonder if you can move the cooling system to the trunk.

Curiously, why not a V6 diesel? Less weight... better economy... and you still get that nice dollop of torque...

[craysus]

Originally Posted by niky

Still not bad... but trust me, you will feel all 179 kilos of that extra weight every time you get to a corner. Not something you can't tune out, but it will still affect the handling.

I wonder if you can move the cooling system to the trunk.

Curiously, why not a V6 diesel? Less weight... better economy... and you still get that nice dollop of torque...

Agreed, it wont be as nimble as a stock FD...but with some wide arse rubber, and big brakes it will handle very well..With the big bad arse engine in there which could be tuned to well in excess of 1000hp if desired (And still be frugal when OFF boost..), you would have a super nimble sports car (Think better handling than a Z06 vette), more straightline punch capability than a dodge viper, and better fuel economy than a prius...not a bad mix ....
Yes, you could definately put a more efficient smaller diesel in there, with decent torque to maintain the shoot for the stars gearing, but you would instantly lose the straightline speed required to make a race car driver grin properly!

[freebeard]

Agreed, it wont be as nimble as a stock FD...

Alrighty then: http://ecomodder.com/forum/showthrea...ery-26356.html

[cRiPpLe_rOoStEr]

Not sure if a Diesel RX-7 would lead to a fuel-efficiency really comparable to a Prius, but that would be still awesome. BTW what about that Cummins ISV5.0 from the Nissan Titan instead of the Duramax?

[samwichse]

Basically I would make my own Aptera if I could.