Advice needed, ground up custom car, rear engine

Hello,

I am looking to make a fun weekend car that is safe for other friends and family to drive.  I would like to have my fabricator make a car similar in looks to the Ariel Atom or Asbo 2.  I am trying to figure out the best drivetrain for this set up and we could use some advice. 

We are wanting the vehicle to be rear engine, and most importantly have traction control and electronic stability control for safety.  Want the vehicle to be powerful but not so fast people get hurt(reason for tc an esp).  Any advice?  I was looking at buying a wrecked or older Porsche 911(year 2002 is when they started esp i think) but worried about reliability and cost.  Thanks again!

How would you program ESC for a custom build vehicle?

Keep overall weight and wheel base the same

I here the Ariel Canoe platform is receptive to your intended use. 

Ariel Atom?  Need it to be four seater

ESC can be difficult to get just right, but if you have an older platform it's likely crude enough to work well enough. If you do want to port over ESC from another car, you're probably right in keeping the same basic layout - ie, no FWD drivetrains in the rear.

Do you want rear engine or mid engine? If you want rear engine, you really only have one option and you know what it is. If you want mid engined, there are a few more options. Keep in mind that both mid and rear engined are liable to be fundamentally more in need of ESC than a front engined setup.

My recommendation would be to concentrate less on ESC and more on mechanical grip and good suspension. Also, take a good look at your power levels. A skeletonized car like an Atom tends to be pretty lightweight, and 300+ hp in a sub-2000 lb car is a very, VERY fast little beast. The Exomotive Exocet might actually be a decent choice - it's Atomesque although it is front engined, but more importantly it handles like a light Miata and even the basic stock 128 hp engine is enough power to have a lot of fun. No traction or stability control, just good traction levels and a very fundamentally friendly chassis.

If you want to build from scratch?  Start with the plans from Midlana.com, its a proven design and tends to work well with a large variety of drivetrains.

Then use a high performance FWD vehicle (Focus ST/Fiesta ST, Civic Si, etc) as a donor along with the various Miata bits needed (steering rack, uprights, etc.)  Plenty of reliability in FWD drivetrains, choose the type that you prefer.

The issue you're going to have is that any factory TC/ESP/ABS is going to be based around a heavier vehicle with nowhere near the performance capabilities that most vehicles the size of an Ariel Atom/Lotus Seven/MidLana and will require all of the sensors and control modules from the donor vehicle to work.

Another option would be to buy Exocet chassis, install Miata drivetrains (or an LSx if you need the performance) and spend the money you would have spent on your fabricator on the high end ECU, sensors and computer modelling needed to properly implement TC/ESP/ABS, etc.

BTW, realize that at 1600lbs, you don't need much power to shame many higher end exotics up to 100mph (the aero of open design cars really suck above 100mph, so that will always be a limitation)

Just saw the four seater comment. You're thinking of one of the big sandrails, I think.

Basically I am looking at a street rail that seats four, correct.  

Stefan, I haven't been able to find an aftermarket esc system.  I called racetronics and they said it wouldn't work in my application.  

Rear or mid engine doesn't matter as much.  I just figured with a rear engine I would have more room since it will be a four seater.

Seriously, buy a Porsche 911.

Unless you are dealing with 600 horsepower, you should not be so hot for driver nannies.  No offense, but I've seen far too many Web versions of people demonstrating distaste for custom builds on paid-for cars.  Why bother?  

I think this fits the requirements. Note how the traction control is doing an admirable job of maintaining traction even on a low friction surface. And it would seem to seat 4 comfortably. DIY from off the shelf parts.

Even in wet conditions the traction control keeps the occupants safe

Appreciate the jokes but I need the driver nannies.  Any other ideas on drivetrain?

If you're going to try to maintain factory ESC, you're limited to all the rear-engined cars on the market that came with ESC.  You're right that mid-engined is going to be a packaging problem for a four seater, and I'm not sure you can find a mid-engined car with the wheelbase you need. Heck, with the 911 you even have the option of AWD if you want. I think it's the way to go.

My opinion of driver nannies and high power/weight vehicles is: if you don't trust the driver with the car, don't give them the keys. If the car is inherently unsafe, then fix the fundamental problem. This is not a theoretical keyboard warrior thought process for me, as I deal in building high power/weight vehicles and with journalists. Right now, there are two 500+ hp 2600 hp cars and one 400+ hp 1800 hp car waiting for me to test drive in the shop. They're all built to be easy to manage. If you ask them to do something stupid, they will do it. But they will never surprise you, and that makes them safer than cars that can't be trusted and are saddled with nannies.

If you take ESC out of the equation, then you're basically looking at a modified sand rail. Loads of frame designs there, and the obvious powerplant is a LS mill. Tweak the suspension and rolling stock for pavement use and you're 90% of the way there. You can adapt ABS much more easily than ESC, and that's a worthwhile safety net to have.

Looks like the 911 is the way to go.  I appreciate all in the info guys.  If anyone has anything else to add I will be checking this thread multiple times a day over the next week.  Thanks again!