More fuel for thought
FINE-TUNING FOR INNOVATIVE NEW THROTTLE BODY
IN THE LAST ISSUE OF VANTAGE (Winter 2016) we drove an Aston Martin DB5 prepared by GTC Engineering and fitted with Jenvey’s intriguing new Heritage Throttle Body system, designed to look like classic Weber DCOES but featuring modern fuel injection and fully-mapped engine management.
We were impressed, but this brand new system was still a work in progress and there were a couple of driveability issues, chiefly when coming off idle or the overrun. John and James Winsor at GTC were keen for us to try the car again after more development time, so we duly reappeared at the company’s workshops near Silverstone for Take Two.
The DB5 is now running on an Emerald K6 engine management system, mapped by Emerald itself, and the idle control valve is now plumbed-in to give a smoother, more stable idle and better progression moving away from it. There has been some visual tweaking, too, with period-looking transparent fuel pipes making the installation look even more like the original carburettor system.
It took just seconds to sense the improvement. The starting is instant, the idle perfect with a slight hiss from the control valve while it stays open to feed the extra air a cold engine requires. The hiss subsides as the engine warms.
There are no jerks, flat-spots or surges, just a rich, smooth flow of torque from idle speed to high revs. It feels fabulous, as if every hydrocarbon molecule is contributing something useful, and the throttle response is instant. It’s hard to imagine how a Marek straight-six could run more efficiently than this. Point proved and mission accomplished.
Our story stated that the throttle bodies are available in 38mm, 40mm, 42mm and 45mm sizes, but actually that’s not quite right. Scrub the smallest of those, and add 48mm, for the correct range. Meanwhile, GTC is fitting its second Jenvey Heritage Throttle Body system to a DB5 GT. A what? Yes, a DB5 shortened and lightened in DB4 GT fashion some years ago. Should make quite an entertaining machine.