Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 4/4 Sigma Throttle Bodies?

I must make a little correction about the Omex ECU.
A so called "piggyback" ECU is one that sits between the original ECU and modifies the input and/or output signal in some way to change the fuelling. Typically it might fool the system into providing a richer mixture at certain rev ranges and/or throttle openings to increase the power beyond that which is available using the factory map that has been developed to minimise polution.

The Omex ECU is a complete fuel injection and ignition control unit in its own right. For convenience sake the original Morgan ECU is left in place to control the instruments. You could actually remove the Ford/Morgan ECU and the car would still run but you would have to find another way to drive the instruments and some of the instruments would probably require recalibration if they were connected directly to the sensors.

Craig...a few observations on the Sigma mods:

Throttle bodies on a standard Sigma gives about 150 bhp....at a cost of about £3500 +....glorious sound but most performance is at top end of rev range..not great for everyday use.

Some people found the noise tiresome after the novelty wore off !!!

Each engine is different and hard to estimate bhp...I would put yours at 137.6 bhp !!!!...joking !!!!..who knows without rolling road test.

I waited for 6000 miles run on my 4/4 before I did anything..gives engine time to settle down and for driver to get used to the car.

I then had the remap...£250..BIG noticeable difference in terms of acceleration right thro the rev band,mid range torque and even mpg driven sensibly.

The standard manifold is crude and strangles the engine as I'm sure you know..the Librands tuned manifold with the sports exhaust was another step in the right direction.

Changed the sound of the car to a deep pleasing boom with pops and bangs if required.

In many ways a much nicer sportier sound than my +4 Supersports.

KN filter with homemade cold induction system also helped..as we all know the engines thrive on cold forced air.

Suspension changes followed to take advantage of increased power and torque:adjustable shocks,panhard rod,brake reaction bars (cheap and effective way of tightening up front end)

Tyre choice is important..the oe contis were not great as a sporty option.

Beyond these mods different cams are available but where do you draw the line and at what point do you change the car for a bigger engine model ??

The choice is yours !!!!!

Interesting replies guys!

Lots of food for thought... at the wrong time of year!

Many thanks. :>)

Thanks for the info Kev, I’ve done the Panhard Rod and brake reaction bars. Manifold will be next then

Kev,
How did my car compare to your old 4/4 when I took you round Curborough last year? Throttle bodies, Librands manifold and silencer but no suspension mods. It did have an extra 16 stone of Kevfits to drag round though.

Gareth...nice to hear from you.

I was well impressed with your car and skills round Curborough last year..perfect narrow bodied nimble sports car...very stable in the tight corners of the circuit.

In the right hands it shows what a great sporting car the 4/4 can be.!!!

There are a couple of threads on here about throttle bodies. Could someone explain to an old duffer more familiar with Amal and SU exactly what a throttle body does. My impression is that its little more than an intake trumpet fitted with a butterfly and an injector. In which case of itself it is unlikely to change performance. Its the ECU that will do that by changing advance and retard and injection volume and timing.

Am I correct?

Yes Howard, thats basically a good description of a TB!

More power is gained because each single of 4 TB's has about the same mass flow that is available through the standard single unit that is supplying air to ALL 4 cylinders. So effectively much more air in, more fuel in, bigger bang, so more power!

The flow efficiency of air through the TB's to each cylinder is also massively improved, in the same way as an aftermarket 'header' exhaust improves the flow out. So once again, more air in, more power!

Of course you then need an ECU to maintain and calibrate the correct Air Fuel Ratio...

Then of course you can add cams, that give more valve 'lift' and 'duration' that again enable more air/fuel in...

And perhaps a supercharger!

Then it all gets more and more expensive!!

I’m back Richard 😉. Different moniker as I could never get my password sorted! Yes....I had my 2010 4/4 fitted with throttle bodies...by Aero Racing who at the time I think was the only option as the factory wouldn’t allow my dealer to fit the kit. In addition my car was modded to end up like Max 5’s car. Mike Duncan fitted the 4:1 diff, I fitted a panhard rod and Librands sports exhaust system, Williams did the front end Suplex kit and CR6ZZs. It was dyno’d at 156bhp. I also had the factory fit a Supersport style set of bonnets.....they cocked it up at first and that bonnet is on the Williams 4/4 race car as a result!
It was a lovely car and yes, I regretted selling it for the Roadster. It may not have had the performance of the Roadster but it was a lot more nimble handling wise and I didn’t have sump clearance worries. I should have swopped it for what I believe is the best 4/4....the 75th Anniversary model with the 2 litre Duratec.

It was rather iffy at MOT time, the 200 cell cat on the Librands system did it no favours and I was constantly getting the engine management light on due to lambda sensors giving spurious readings. I believe Williams have sorted that out for the new owner who loves the car.

On reflection I’d have gone down the route Kev and Craig did if it had been available at the time...the T/Bs certainly weren’t cheap. My best mod was the diff change to 4:1. It made 5th gear that more usable and helped acceleration. But I have to say the sound of the T/Bs was addictive when it came on cam!

I finally found the photo I was looking for!