Hi,
I have a 1983 series III EFI engine fitted in an Autotune Aristocat (a kit car with almost all the donor XJ6 mechanicals fitted onto a spaceframe chassis and an xk120 like body).
Has anybody fitted a more modern EFI system? I am basically looking for more power, so any other solutions on that front are of interest.
Chris
EFI
Moderator:LJR
Re: EFI
My guess is a more modern EFI would decidedly improve emissions. The standard Jaguar one at that time was "open loop", i.e. did not monitor the exhaust oxygen content; that's for the UK - Californian engines were closed loop, and also saddled with other emissions control gear.
However, I'd doubt you'd get any better performance than by merely ensuring the existing system was working correctly. (That's not as easy as it sounds - the open loop system has a hard-wired map of mainly airflow meter and temperatures; that meter is a flap moving against a fixed spring, and a carbon-track variable resistor. Wear and ageing will alter the calibration; how to recalibrate is an exercise for the reader...).
Modern EFI systems allow the engine designer to extract more power from a given capacity by running things closer to limits (such as not pinking), but unless you change the old 4.2's cams and/or cylinder head and/or inductions system, you'd just be tuning the engine a tad better.
I'd look to AJ6 engineering for enlarged throttle bodies, remapped ECUs and other kit to get more oomph from Jaguar engines, but I'm not sure if they go back to the 4.2.
Assuming what you want is better performance (rather than necessarily more power) replacing the auto gearbox with a manual (if you haven't already done so) would be an effective 25% improvement straight off. Then replacing engine-driven bits (cooling fan, power steering) with electric ones can leave you with more of the ~200bhp for your enjoyment.
However, I'd doubt you'd get any better performance than by merely ensuring the existing system was working correctly. (That's not as easy as it sounds - the open loop system has a hard-wired map of mainly airflow meter and temperatures; that meter is a flap moving against a fixed spring, and a carbon-track variable resistor. Wear and ageing will alter the calibration; how to recalibrate is an exercise for the reader...).
Modern EFI systems allow the engine designer to extract more power from a given capacity by running things closer to limits (such as not pinking), but unless you change the old 4.2's cams and/or cylinder head and/or inductions system, you'd just be tuning the engine a tad better.
I'd look to AJ6 engineering for enlarged throttle bodies, remapped ECUs and other kit to get more oomph from Jaguar engines, but I'm not sure if they go back to the 4.2.
Assuming what you want is better performance (rather than necessarily more power) replacing the auto gearbox with a manual (if you haven't already done so) would be an effective 25% improvement straight off. Then replacing engine-driven bits (cooling fan, power steering) with electric ones can leave you with more of the ~200bhp for your enjoyment.
1986 XJ6 Sovereign Series III
1991 XJS V12 "facelift"
2021 I-Pace SE
1991 XJS V12 "facelift"
2021 I-Pace SE
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