Twin Plenum Vitesse injection - FI in a P6, uprated diff question too

mrtask

mrtask

Well-Known Member
Do any forum users know what I would need to do to fit a twin plenum injection system from a Vitesse SD1 to my '73 P6, with regard to the ancilliaries, wiring it in to the old loom, hooking up the ECU, fuel pressure meters, airflow meters, all the modern stuff that wasn't needed with the old SUs. I doubt I'll by the one that's on ebay.uk at the moment, funds not permitting, but perhaps one day I'll be able to afford a working set-up...
Whilst I'm daydreaming, and not strictly speaking the right part of the forum for this question, but how much power can the standard diff in a V8 P6 take? Has anybody fitted a limited slip diff? Or adapted a Jaguar IRS to their P6? Allegedly there are a few P6s fitted with 4.6litre Range Rover lumps, what diff do they use?
 
In answer to your question about how much power a P6 diff will take, I would say not a lot! Even with the standard V8 it's easy with the right circumstances to blow a diff.
I believe the racing P6B's used a modified Jag diff.
My favourite P6B job was always a tune up, they came in running dog rough with loads of free play on the throttle pedal 'cos the throttle bushes were shot, and no performance.Carry out tune up and fit the bushes, and hey presto, loads of grunt and instant throttle response.
If the customer took the car when it was wet, first time they pulled out of a side turning, they'd boot it as they did before, but this time it would be away, the inside wheel would spin,and when it gripped again the diff output shaft would snap! Then came the phone call, off we went with the tow truck, and got another job to do.
Even tho' we told people to be careful they just forgot.
As for the EFI systems there is one type that only needs a couple of wires to wire it in, but I can't remember which one offhand. If it progresses on to more than a dream, I can find out.
 
There was an article about this in P6 News a few years ago but I don't think it was the twin plenum system .Allen Myers wrote the article, I think Paul Atkinson helped him do the conversion
 
IIRC the EFI heads have a machined area in the combustion chamber to clear the injectors.
You would probably need the later heads to get the best out of the EFI system anyway.
 
I would advise against it.

reason being I had a 1987 efi range rover with the same(ish) system and it was a little ropey but only really on starting, sometimes it wouldn't. I eventually tracked it down to a non airtight rocker cover gasket of all things but even then I wasn't 100% convinced.

When it wouldn't start and you kept trying it would foul the plugs, it didn't matter how well you cleaned the plugs up they never worked again. a new set of plugs and it would start fine.

It was a good system when running but beware. The later hotwire version was much better.

A proper tune up and balance carbs would be a better idea. sd1 tp's are 20 years old. but there are companies who can supply new recon and reworker ecu's though.

You could probably source a good 3.9 range rover and scoop the engine rather than trying to find a TP sd1 as they are sought after even in poor condition which inflates the price. the RR 3.9 is supposed to be more fuel efficent also.

As for the rear diff, remember that the p6 diff case has mounts for the rear brakes to hinge.

I had an sd1 an know plenty of people with them great car and only about 3,000 left on the dvla books now..

Colin
 
I'm a big fan of EFI systems and would always recommend one over carbs, but they have developed in leaps and bounds over the past 20-30 years, probably more so than any other part of a modern car.
What would probably be a good compromise would be to use the vitesse plenum chamber, fuel rail, injectors and throttle bodies, and use a good aftermarket ECU such as the Emerald M3d system , or Megasquirt if you fancy DIY.
You will then have full control over the fueling and ignition, and they can be setup to exactly match your engine.
These aftermarket systems can cost upwards of £500 though, so you need to be serious !!
 
G'Day all
Mob here in Australia called TriumphRover Spares have a twin throttle set up for around the $750 mark. It apparently flows around 400HP (!) in the correct setup, but you will need the stage 2 heads with big valves and a bunch of other bits (namely the Haltec ECU $1670) to make it work.
I have been eyeing it off for a project that I have on the cards at the moment, I might have to try it and let you know!
As for diffs, the blue car has eaten its diff. So new centre from a Jag is planned, with uprated half shafts, the univeral joints have already been uprated with heavier duty ones. I am putting around 290ish HP through the diff and they last for a little while, but at least the are cheap from the wreckers! I have thought about the whole Jag diff thing but it involves some serious cutting of the body to fit new mounts to hang the thing. It is best if you are building a car from a shell, it makes it much easier to fit.
Hope this helps and inspires someone else to have a go!!!!
Cheers
GUY :D
 
Sorry! - not spotted this thread before for some reason.

Referring to the question on diffs. HarveyP6 is right in saying the P6 diff has definite limitations - but the P6 running in the classic saloons series actually does use a P6 diff and not a Jag!

Alan Ramsbottom at Beechgrove Engineering in Leighton Buzzard, who preps it, has carried out extensive work on it and this is available (and fitted!) for other customers as well.

Start point is to box in (or pocket) the rear mountings to improve the rigidity of the whole assembly and stop it tearing out of the shell. You'd need to do work of this kind to fit the Jag diff so this is neutral in terms of a comparison between them.

Then there is an uprated input shaft in a much tougher steel (the one that runs in the long tube from the prop shaft to the diff proper).

Next come LSD internals, adjustable between road (soft) and race (rigid).

For my money though the star turn is a conversion to Sierra Cosworth vented rear discs. Apart from keeping their fluid where its meant to be long term, you can get a range of pad grades for them unlike the Rover originals. Also, being vented and larger, they keep the heat out of the output flange oil seals on the diff which are otherwise prone to cooking and leaking. Alan has a vented disc conversion for the front to go with this, which has the merit of keeping the existing calipers (suitably spaced) and hub arrangement (and hence all the original load paths).

Alan acknowledges the problem with the strength of the output shafts but uses these as a safety valve (or sacrificial item) to protect the rest of the diff. Interestingly the racer uses only one set per season as a planned change. I wonder if that is because it runs the LSD? That would undoubtedly eliminate the shock loads from a spinning wheel coming to grip, so they could be getting an easier life.

To date he has had adequate supplies of the output shafts but I think the time is approaching where remanufacture is required, at which point they will be done in a tougher material and we'll discover what the next most vulnerable item in the diff is!

Sadly my Thailand car is still not quite ready to receive this treatment, so I shall have to wait to report the improvements. All my engineering knowledge suggests, however, that these are very worthwhile upgrades - and the racer works!

Chris
 
Depends what you mean by expensive! Sierra Cosworth calipers are reasonably readily available - check out e bay - its the discs that are specials so as to fit the Rover hub.

Chris
 
Hi Chris
Do you know the prices for the diff/LSD upgrades and brakes upgrades, front and rear from Beechgrove Engineering?

Blueman
 
Yes, there is a 4 SU system and manifold, I think they call it a Boxer system, I know someone that had one, and they are good, but you have to be on top of your game to keep them in adjustment. They do look good though.I think he may of had one for sale
 
Quad SUs sounds cool. Has anybody got any photos of this 'boxer' manifold? The twin plenum setup I was daydreaming about got sold on fleabay for looooads of money, but not to me!
I read that it is possible to swap the standard SUs for larger ones of a Jag; do they bolt straight on? Which ones fit, what else would be required to make them work properly and give a power increase?
 
You must log in or register to reply here.
Back
Top