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2.5 P.I. Engine and P.I. advise please.


Don2138

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Hello. I hope I am allowed to post this in this section but as it is related to the Triumph 2.5 P.I. Engine I thought it would be a good place to ask.

My main question is “what to look for” with this type of Engine and Fuel Injection.

Next week I am looking at three Stags. One of them has the Triumph straight six 2.5 P.I. Engine. Description of the car seems to suggest that this Stag has a lot going for it so I should not dismiss it. Has anyone experience of a Stag with this type of engine and if so could they please give their opinion, thoughts. I know about the Injection system requiring to be converted to unleaded ( problems with the seals with leaded petrol ) but is there anything else I should know about this system. I know they had a bad reputation when they first came out but like the Stag V8 any problems should have now been sorted. As advised this is one of three Stags I will be looking at and as this will involve a round trip of about 600 miles ( I must be mad ! ) I would like to know as much as I can about the 2.5 P.I. engine and fuel Injection.

Many thanks, Don Kennedy.

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I too was concerned about the poor reputation of PI when I was thinking about buying a saloon a couple of years ago.  Do as i did - talk to malcom at Prestige Injection and maybe Chris Witor.  Basically the respose regarding unleaded is "if it works, drive it until it fails - it could take a while"!  

In the event, I bought a non runner, the fuel pump was seized, the metering unit leaked and the injectors were bunged up.  I had plently of spare pump so just dug out a good one, but as I had not spent much buying the car I decided to blow 400 quid on a set of injectors and one of malcom's lifetime guaranteed MU's.  Best 400 quid I spent - bolt on and drive off.  

I subsequently had more toruble in the pump dept, read the books, got a fuel pressure gauge and got the car running sweetly doing over 25 mpg.  It's not rocket science!.

The only bit you "can't" play with are the MU settings - that's done on a test rig - however there are others on this forum that have "fiddled" successfully on the road :-)

Bottom line is don't let the "poor" reputation put you off, a lot of it is just common sense and easy overhaul.

A Stag without the Triumph V8 is probably a whole different discussion  ;-)

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Just to echo mike's words about the PI and the service from Malcolm at Prestige: http://www.prestigeinjection.net/ Malcolm asks you penetrating Qs  about your engine and what you want from it, and sends you the M/u all set up and ready to fit.   I've raced mine for five years without resetting it - how many times would I have fiddled with a set of carbs in that time?

I'd also recommend Malcolm's Bosch fuel pump kit to replace the old Lucas windscreen wiper motor one, and Mike's suggestion of a fuel pressure gauge to check problems.   Mine diagnosed that it was pressure and pointed striaght to the source of recent probs.  Don't even think about having an ordinary direct measurement gauge inside the car, but build/modify your fuel piping to allow you to fit it temporarily. I use a long length of Aeroquip braided hose so that I can have the gauge in the car when test driving only.  

The poor reputation of Lucas Pi is down to the very poor, absent even, in-house training that Triumph offered when the Pi cars were introduced, and is mainly from 2500 owners at the time.  TR6 owners were savvy enough to seek out the garages that did understand it and over there in TRland, Pi rules.

JOhn

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If I were in the market for a Stag, I wouldn't let a 2.5 engine put me off, if all else was a convincing package. I'd much rather have an excellent as-near-to-rust-free body as possible, and few trim problems than the correct engine - dependant on cost!

The fact that a six is fitted instead of the correct V8 tends to depress the price significantly, even for cars in otherwise excellent condition. Use the cash saved on petrol to use the car more, or to find a scrapper with a better V8 later ;)

Unleaded - on limited annual mileage you may find that you may expire before the head does! If higher annual mileages, then the advice given here is sound: wait until problems arise (if the do!), then get an unleaded head - or bung in that V8 you've found!

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Many thanks to all for your time replying. Looks like I should not rule out the 2.5 PI Engine. Off next weekend to have a look at the Car, maybe this is the one ?. With a round trip of about 500 miles I hope it is worth the effort.

Don Kennedy

P.S. There is a line between Enthusiasm, Dedication and Madness, I think I must be in the Madness area !.

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oh and forgot to tell my most recent mod - Malcolm now offers a Pressure Reg Valve that delivers 105psi regardless of input pressure (of course it has to be greater!).  This is a big improvement over the original type PRV which only delivers a set pressure drop, so if your pump pressure changes then so does the pressure to the MU.

Good value at around 80 quid, I fitted one just before the RBRR - peace of mind should I have had to do a pump swap on the fly!

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Part of the appeal of a Stag must be the sound of that V8, but having said that a PI like I have in my TR6 doesn't sound half bad either.
People say I am wasting my money putting "additive" in the petrol as it is running on un-leaded......possibly, but it is running that sweetly I don't want to change anything. I agree, run it and if you ever need to replace a metering unit or cylinder head, then is the time to fit one designed for unleaded - until then just drive it.

Your comments about the Enthusiasm, Dedication to Madness line......this might be the wrong place to ask about that as most of us are fairly at the right-hand end of that line.   ;)

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MikeyB wrote:
oh and forgot to tell my most recent mod - Malcolm now offers a Pressure Reg Valve that delivers 105psi regardless of input pressure (of course it has to be greater!).  This is a big improvement over the original type PRV which only delivers a set pressure drop, so if your pump pressure changes then so does the pressure to the MU.

Good value at around 80 quid, I fitted one just before the RBRR - peace of mind should I have had to do a pump swap on the fly!


I can concur about the alternative design PRV.

Not cheap, but does exactly what t says in the box. What ever pump I fitted whilst testing, exacly 106psi out, even my 160+psi pump.

I had exhausted my (small) stock of original style PRV's without finding one that was reliable so I bit the bullet.

Cheers

Colin

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