Ultima EFI

Many Ultima builder have asked about how to fit central locking at one time or other. For the benefit of posterity this is a rehashed version of a Pistonheads post on the subject that I wrote...

I wanted to keep the door locks but wanted to avoid scuffing the body with my collection of keys so I fitted central locking. It wasn't easy coming up with a mechanism that worked...it took over a month of weekends and much cussing to come up with something that was reliable. The result is quite simple though as the pics show:



If you wanted to replicate this then I'd recommend fitting the Ultima door locks and getting them working perfectly with the key. Then make an accurate template out of card of the mounting holes for each door in turn. Mount the door lock for the door in it's template before building the mechanism around it.

There are two tricky bits in the design. Getting the right throw on the extra bellcrank that is attached to the lock mechansim is important. To account for the inevitable misalignment of the motor movement I attached a long M3 bolt to the eye in the end of the motor. I then spaced this away from the bellcrank with washers and a nylock holding the stuff together but with a bit of slop.

This design has been working in my car for the last two years and has been perfect. The key is a little stiffer than normal because you have the motor to move as well but I don't see any way of making it better. There is basically no added friction and the locking action is positive but doesn't place much strain on the motor.

For motors, in the UK anyway, I'd recommend Maplin. They sell them for under £10 each!

I've been a user, proponent and occasional contributor to Free Software for the best part of 15 years. Back in 96 I came across the EFI 332 project which was aiming to develop a completely DIY EFI system using the then new(ish) Motorola 68332 microcontroller. Though I didn't have a car to put it in I lurked on the mailing list and picked up a few parts in the group buys that took place from time to time. The project eventually fell by the wayside. Only a couple of folk managed to build enough of the EFI332 system to get it actually running on a real vehicle. Of this select group, two dedicated hackers and engineers, Bruce Bowling and Al Grippo went on to develop a much simpler more easily digestible EFI system.

The simpler DIY system they came up with is called MegaSquirt and is based on a derivative of the Motorola HC11 microcontroller. The MegaSquirt project really took off and is now used on hundreds upon hundreds of vehicles from skidoos to 300+ mph landspeed record bikes. The MegaSquirt system is run as an Open Source style project will all the code and circuit diagrams released for anyone to look at and modify.

So when I got to thinking about putting EFI on the Ultima I was planning it was obvious that it had to be some variant of MegaSquirt rather than an off the shelf system from Holley, Edelbrock, FAST, Electromotive or MoTeC.

I'm planning on attacking the conversion to full EFI in stages to keep life a little simpler and hopefully keep a running car. The stages I'm thinking of are:

• Computer controlled spark - The idea of this is to use a MegaSquirt loaded with MegaSquirt'n'Spark-Extra software to control just the spark timing through the existing distributor. The existing dizzy just has mechanical advance which makes for lousy road manners and economy.


• Basic fuel injection - Once the spark is dialled in it's time to do the full conversion to fuel injection. I have a Holley MPFI manifold on order and will be hooking this up with an Aeromotive fuel pump and regulator and Holley throttle body. This will need a completely updated fuel system as well as lots of new wiring to connect all of the sensors.


• Traction control - Once I'm a bit further down the line I hope to be able to start playing with the extra features in the MSnS-E code. I'm particularly interested in traction control as while I may be running 335/30R18 tyres at the back there's a lot of torque back there...


• MegaSquirt II - Soon Bowling and Grippo hope to release an update to MegaSquirt called MegaSquirt II which has much more CPU power and bring the ability to control Idle Air Control stepper motors like the one in the Holley throttle body. This should make cold starts a lot better and also help get the overall tune a lot better.


• Linear fuel gauge - At the moment most Ultima fuel guages are very non-linear. The tank sensors are linear enough but the tanks themselves are a strange trapezoidal shape which means that after you've gone a few dozen miles a full tank can read 1/4 full. The MS unit has a spare analogue input which I hope to be able to use to read the fuel sender and correct the output to the gauge. This of course assumes that it's still a spare input after I've implemented traction control...


• UltraMegaSquirt - Bit of a pipe dream at the moment. The next version of MegaSquirt is going to be based on a much more capable processor the Freescale ColdFire 5234 (nee Motorola). This should be capable of full sequential injection, support for super accurate control of two wideband oxygen sensors and all sorts of other goodness...may be I'll even end up with full coil-on-plug ignition with ion sensing? Who knows.

Well, that's the plan anyway. Read on to see what really happens...

Hi! The aim of this blog is to attempt to document the process of converting my Chevy V8 engined Ultima GTR kit car from its current Holley carburetted form to having full blown Electronic Fuel Injection(EFI). Along the way I'll probably also be sprinkling in the other mods I make to the car.

First off it's probably worth explaining what an Ultima GTR actually is. Here's a picture of my car at a trackday I did at my local circuit, Knockhill in Scotland, in June 2004:



An Ultima is a mid-engined kit car usually powered by a small block Chevy V8 connected to an inverted Porsche G50 gearbox. The kit is designed and supplied by Ultima Sports based in the Midlands of England. The car is a very high performance "racecar for the road" and currently holds the world record for doing 0 mph - 100 mph - 0 mph in a production road car. The Ultima differs from a lot of other kit car designs in that all of the components are purchased new and many are completely custom designed for the car. This means that the car can be registered in the UK as a brand new road car with a current registration.

My car has a fairly standard spec at the moment. It is fitted with:

• 383 c.i. (6.3 litre) SB Chevy V8 - 456 bhp/504 lbft


• Porsche G50/03 gearbox from a 93 Porsche 964


• Standard 12.7" AP racing discs with 4-pot AP racing calipers


• 335/30/ZR18 rear tyres and 245/35/ZR18 front tyres fitted to custom OZ racing wheels


• Custom adjustable Intrax dampers


• Twin 40 litre foam filled fuel tanks


• RAC MSA spec full rollcage


• 6-point racing harnesses and seats

I originally purchased the engine as a custom Ultima crate engine from American Speed in Illinois. As it was shipped the engine worked great out of the box and it has been nothing but reliable. However I did spec the engine with the intention of converting it from the more usual Holley 4150 double pumped carb to a more modern fuel injected engine. Hopefully this will allow me to pick up better fuel economy and driveability as well as giving me endless excuses for tinkering...