Hi Shawn,
Yep, I reckon Fuel injection is the way to go. My TR6 PI is putting out
around 165~170 bhp and still has very good manners around town. While it is
true the hotter cam reduces the low down torque, I have a nice smooth idle
(at arounnd 850 RPM rather than std 650) and the car will quite happily
pull away from 1000 RPM in 3rd gear without lugging. The major sacrifice
with this car is in the fuel economy - I normally only get 27 MPG cruising
at 70MPH where as a friend with a standard PI is getting up to 35 MPG.
The limitation I am having with the original lucas system is that it only
senses off vacuum and with the lumpy cam, consquently it runs way rich at
idle.
The EFI systems have the advantage at idle (below 1000 rpm) you can program
the controller to ignore the vacuum and read solely off the O2 and throttle
position sensors. The result is a nice smooth idle.
I'm currently modifying a Lucas PI system to take toyota injectors and hope
to have that installed in the next month or so (I's just waiting to get
into my brothers workshop). I'll install this on my Triumph saloon and use
it daily for a couple of months just to sort out any reliability problems.
I have driven a carbed Triumph saloon car (identical engine to the US spec
TR6) fitted with EFI and the difference over carbs was quite impressive. No
major increase in power, but the whole engine was far more responsive and
much happier to rev (normally these start to struggle after 4500 RPM but
with EFI reached redline no worries at all!). This guy also improved his
fuel economy from 28 MPG up to 33 around town and 41 on the open road at 65
MPH.
There is a crowd at advance in the states who do an EFI conversion for the
TR6, but I can't find the link.
I don't know too much about the exhaust side of things, but I understood
(from the local classic car racing boffins) there is not too much to be
gained over the stock twin pipe manifolds. My car is stock, but has a
higher flow muffler from a BMW 540. I installed this because the exhaust on
the car was two straight pipes when I got it (very unpleasant, but mighty
quick).
My understanding is a higher flow exhaust also reduces the inlet vacuum but
as I say, I know very little about it.
Perhaps someone else can add to the subject about the exhausts.
Hope this is helpful
Cheers
Bernard Robbins
'71 2500 PI
'73 TR6 PI
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