PI TO CARBS CONVERSION

[tr62500]

Chaps,

 

Thanks for your comments, I can see all points of view, I must say that I want to stay with the PI system if I can, as its part of this car and also, I do like challanges. I should say the reason for my original question, is that my 6 has not been started for 3 years, it has a bosch pump fitted, and a newish metering unit. But the car was prevously run without any filtering, so I am thinking that there is possible damage to the injectors and metering unit. I am going to put a new tank in, as the existing one has rusted and add a fuel filter. Attempt to purge the system. See what happens when I crank it over, If things don't work out, I was looking at a carb system.

 

John

[Mike Goldthorpe]

To me, the PI system is part of the Triumph history. It's what makes our cars different which, for me at least, was one of the reasons I got mine.

Carbs are OK but I've had problems starting my Citroen Traction Avant before and that's only got one carb! The TR6 I had was used everyday for a decade+, commuting and shopping duties as well as drives to Wellington from Auckland (I'm in New Zealand). Consumption was not good on the drive to work cycle but that was mainly due to me being stationary in traffic (the Citroen, with it's single carb, also suffers from a bit of a thirst!). The long drives gave me decent fuel consumption - about 25 mpg, give or take. I didn't do much to the PI system while I had the car - changed to unleaded compatible MU when the original died and the pump was replaced with a Bosch one at the start of my ownership when the Lucas one died (old car,classic car dealer bought, bound to happen). Keep a decent regiment of preventative maintenance (I believe they call it a "service" in the trade) and I'd be surprised if you find any problems at all.

Carbs...might as well have got an MGB or GT6 if you want them..... ;-)

[Alec Pringle]

Hi John,

 

it's a TR6PI.

 

That's PI, as in Petrol Injection, it's what made the ruddy car worthwhile.

 

So it might need replacement injectors, and/or a reconditioned metering unit, and/or a PRV. Big deal, Neil Ferguson will soon deal with that for a reasonable cost, it's not a fortune and it's not rocket science. Get it set up properly and it will work, as long as you don't fiddle with it unnecessarily.

 

Yes you could put SUs on it - if they could match PI then Triumph wouldn't have spent all that money with Lucas. Fitting SUs to a PI car is like getting married, then buying a packet of 3 and wearing them all at once.

 

You could fit Webers - bit like getting married then buying a vibrator apiece and a 12-pack of AA batteries.

 

It's not quite like the real thing . . . . . and it's missing the point.

 

Cheers,

 

Alec

[scotty]

My 6 was dragged out a garage in June where it had lain under a film of dust for 16 years . It needed 6 new/ recon injectors , a recon metering unit - total £160 from Neil and a bit of tinkering with the prv as the pump was pushing out too much . Got me to Harrogate and back with with no issues . I don't want to get involved in NTCs juvenile baiting but it starts on the button both hot and cold with me standing outside the car - If you take your time and set it up properly in the first instance it will be v reliable .

[Andy Brady]

And Stromberg 175's?

[Alec Pringle]

No better and no worse than SUs in my experience, decent enough carbs but not a substitute for PI - my comments above re SUs apply equally to Strombergs.

 

Cheers,

 

Alec

[Guest ntc]

del

Edited September 6, 2011 by ntc

[Andy Brady]

No better and no worse than SUs in my experience, decent enough carbs but not a substitute for PI - my comments above re SUs apply equally to Strombergs.

 

Cheers,

 

Alec

 

 

 

You don't find that the Stromberg, (a fine TRiumph designed precision instrument), stays in tune far longer and are more economical than the le cheapo BMC SU's?

[Mk1PI]

They would if the diaphragms would last more than 18 months....

 

And Neil - fine tuning the metering unit (ie tweaking all those things that you MUST not touch) to an individual "no longer standard/part" engine is pretty straight forward and can have very beneficial effects on driveability and fuel consumption. No different really to playing with needles on an SU (what is the factory SU needle for a 150 bhp cam??? or factory jets and chokes for a modded Webered car??) .

I would suggest that a slight adjustment on a metering unit to lean off mid range or the like is way simpler, cheaper and quicker than changing needles or jets on multi carbs (one tweak for all six pots )

 

If you are not confident the specialists are very able to do this.

Edited September 6, 2011 by Mk1PI

[cmdr19]

 

Yes, spot on. A few idiosynchracies is what makes owning a TR6 PI fun. Also, how many carburated car owners can push the choke fully in within a few hundred yards and then drive/idle smooth as silk?

 

 

Me actually. Mine runs SU's, starts 1st time whether its 34c or -10c, needs choke for half a mile or so and uses all 6 cylinders as Triumph intended.

As for performance, it's quick enough (for me anyway),

[Dave McDonald]

My TR5 was put on twin 2 inch SUs by previous owner and has always been as flat as a f--t. Had it on a Rolling Road today and am embarrased to reveal the pitiful power output. It will be going back onto the intended PI system over the Winter.

Dave McD

[Willie Felger]

Hi John,

 

My 72 CP car runs on triple HS6 SUs on a Goodparts manifold - mail order from the States. The reason being that when I bought the car as an abandoned resto the entire PI system was in boxes, unused for about 20 years and in a very dogeared state and would have cost a fortune to reinstate.

 

I already had 2 reconned SUs and a spare electronic Facet fuel pump, so it wasn't much of a choice. I have never owned a TR6 before but a couple injected 1970s Mercedes. To me every TR6s always seems to run and smell very rich - as if they have the choke out - and I still hate following them in a convoy in my TR3A coz they smell so bad. My Mercs were both high mileage cars but were clean as a whistle by comparison. My personal conclusion is that Bosch injection is good but Lucas isn't.

 

My 6 runs smoothly, sounds wonderful and starts first time every time - even with no choke on the centre carb. (It also runs very hot but that's a silted block and not a carb problem!)

 

There are a few tricks - such as all 3 carbs need to be "front" ones with the float chamber at the front in order to clear the steering and each other, but I managed to swap one and buy one to achieve it. As someone has else said, I found a second hand distributor pedestal - and corresponding short drive gear - from an ex US carb car.

 

I don't know how to add pictures to this but if you can get your e-mail address to me I'll send further details.

 

I love my carbies and they look awesome!

 

Regards,

 

Willie Felger

 

1959 TR3a

1972 TR6

[Andy Brady]

They would if the diaphragms would last more than 18 months....

 

 

 

Can't say as how I've had any issues with the diaphragms to be honest.

[Tom Fremont]

 

. To me every TR6s always seems to run and smell very rich - as if they have the choke out - and I still hate following them in a convoy in my TR3A coz they smell so bad. My Mercs were both high mileage cars but were clean as a whistle by comparison. My personal conclusion is that Bosch injection is good but Lucas isn't.

 

 

 

I would lay the blame for that on the P.I. cam with its 70 degrees of overlap. My '250 on Webers + P.I. cam leaves far less soot on the tail than the Stromberg'd cars with their cleaner cams but it literally stinks by comparison, as it did before with a Kent cam and 78 degrees of overlap. Original Stromberg'd cars had 20 degrees of overlap ( early ) and 36 degrees ( later, with the 125 BHP P.I. cam ). These emissions cars smell comparatively clean; don't know about the 125 BHP P.I. cars but I would expect they will too if the m/u is adjusted optimally.

[johnny250]

I'd be interested to put my old 250 with SU's (+ tr5/6 head+cam) up against a good PI car anytime. I don't know where you chaps are running the cars to think that a carb set-up is sluggish, we are hard pressed to find a road where you can exceed the available top end performance and give a good account against modern traffic at the traffic light Grand Prix. Starts first spin, no Hi-Torque **** needed, and sails to the top of Stelvio without a cough

 

john

Edited September 7, 2011 by johnny250

[rpurchon]

I'd be interested to put my old 250 with SU's (+ tr5/6 head+cam) up against a good PI car anytime. I don't know where you chaps are running the cars to think that a carb set-up is sluggish, we are hard pressed to find a road where you can exceed the available top end performance and give a good account against modern traffic at the traffic light Grand Prix. Starts first spin, no Hi-Torque **** needed, and sails to the top of Stelvio without a cough

 

john

 

il agree with you totatly there john.but you are wasting your breath as far as pi owners go.they are snobs

its like that old sketch with john cleese ronnie corbit and ronnie barker.

richard SUs, i know my place .

Edited September 8, 2011 by rpurchon

[Tom Fremont]

I'd be interested to put my old 250 with SU's (+ tr5/6 head+cam) up against a good PI car anytime.

john

 

 

While you're at it ( if you get any takers ) see if you can rope in a good Weber DCOE'd car too

[johnny250]

Of course Tom, it would be great to compare all.... is it the right time for the Register to organise a day out at Santa Pod......anyone?

It would be really interesting to see the difference between all options....... Lucas PI, EFI, carbs of all sorts and not forgetting , supercharged

 

john

[Peter Cobbold]

Of course Tom, it would be great to compare all.... is it the right time for the Register to organise a day out at Santa Pod......anyone?

It would be really interesting to see the difference between all options....... Lucas PI, EFI, carbs of all sorts and not forgetting , supercharged

 

john

 

Yes good idea - can I run in the 'Single carb' class?

Peter

[Shezbo]

il agree with you totatly there john.but you are wasting your breath as far as pi owners go.they are snobs

its like that old sketch with john cleese ronnie corbit and ronnie barker.

richard SUs, i know my place

 

I say steady on, as a TR6 - PI owner I am not a snob, I just so happen to have a car worth more than yours!

[Mike Goldthorpe]

Well, from here it seems not so much as case of which fuel delivery system is best but an advertisement of well maintained cars operating as their manufacturers intended :-)

My PI worked great once all the niggles were sorted and the car used as intended (often). My carb car and bikes do the same - once everything was sorted and they were used as intended (often).

They all work great but once you neglect the maintenance, they repay you by not working...and where then does the blame go? Not on the operator but on the system!

 

As I said, I liked my PI as it was a part of British automotive history. It's what made the press rave at the time (well, they seemed to in the Brooklands book I have...until unreliability issues became the norm). Once I got the PI system sorted, it stayed sorted and worked for over a decade (OK, the minor hiccup here and there). I didn't see my car as better or worse than any other car because of the PI system - just different.

 

Now, for snobbery, try telling people your 1973 (not tax free) 125bhp TR6 is the doggies danglies in the pub - once the 150 boys stop putting you into your place, the modern car drivers start.....

[Andy Brady]

Never had a PI Triumph but I did have a mechanical system on a BMW back in the day and despite the system being a generation on from the Lucas system, it was also a PITA.

 

The problem with mechanical PI systems is that the system has to be perfectly set up and wear free to work as advertised, the systems are not self correcting to an extent like electronic systems. Wear in particular makes the systems temperamental and a PITA and can seriously impact the performance, even to the extent of stopping the car dead in its tracks. Carbs will work surprising well even when worn and not ideally set up without a great performance hit.

 

IMHO, mechanical PI was a technology before its time, it's amazing they actually got it to work with cogs and gears, but it really did need electronics to make PI deliver on its technical promise. I'm very impressed with anyone who can get a Lucas system to work 100%, but I'd personally go with carbs to preserve my sanity.

[stuart]

Never had a PI Triumph but I did have a mechanical system on a BMW back in the day and despite the system being a generation on from the Lucas system, it was also a PITA.

 

The problem with mechanical PI systems is that the system has to be perfectly set up and wear free to work as advertised, the systems are not self correcting to an extent like electronic systems. Wear in particular makes the systems temperamental and a PITA and can seriously impact the performance, even to the extent of stopping the car dead in its tracks. Carbs will work surprising well even when worn and not ideally set up without a great performance hit.

 

IMHO, mechanical PI was a technology before its time, it's amazing they actually got it to work with cogs and gears, but it really did need electronics to make PI deliver on its technical promise. I'm very impressed with anyone who can get a Lucas system to work 100%, but I'd personally go with carbs to preserve my sanity.

 

My previous Volvo estate (87. 740) had Bosch mechanical injection very similar to the Lucas system and that did Interstellar mileage with no problems at all. Change the filters often and a drop of injector cleaner through every now and then. Would happily return good MPG as well which wasnt bad for a brick shape.

Stuart.

[modelbuilder]

il agree with you totatly there john.but you are wasting your breath as far as pi owners go.they are snobs

its like that old sketch with john cleese ronnie corbit and ronnie barker.

richard SUs, i know my place .

 

 

 

What a really odd comment.

 

Rodders.

[david johnson]

What really odd spelling as well Rodders. Ferrari used too have reliability issues of real significance, but they sold to people who wanted what they offered. Just over 100HP in a heavy sports car with a specific image is laughable. David.