Fuel Injection swap to carbs - a conundrum!

[harrytr5]

Is that Nic ex NLG?

If it is, how are you Bee keeping going.

Keep to PI

I have been running on EFI since 2010

Using original throttle bodies but changed again 3-4 years ago to Jenvey heritage throttle bodies with inbuilt injectors.

These are look alike webbers.

Very happy with it.

Kept all PI in case and stored.

Regards Harry 

[TRTOM2498PI]

The CP cars were lumpy on idle, but OK on the move. The CR cars are smoother on idle, and a little easier to live with around town, but I would always go CP every time ! It is a sports car afterall.

When I had my engine built by a top engine builder back in 2011, I did some research on camshafts, and we fitted a Newman PH2/PH3 hybrid cam.  Many other mods, and entire rotating assembly balanced at Vibration Free in Bicester. The car (on Lucas PI), idled beautifully (actually smoother than a CP cam), and made more power everywhere.  You could put it in 4th gear at 1000RPM & it would pull without hesitation.  Malcolm Jones set up the PI system, (Prestige Injection), by using one of his calibrated MU's, plus a set of fuel injectors. We went for a test drive from his place, and he could not believe how the car behaved low down for a high-lift cam and generally how it behaved and pulled on the road.  He said it was one of the sweetest engines he had been in or set-up.

The car has now been converted to EFI, which has transformed it again, and will allow me to try a Newman PH5 cam, which should be interesting.

 

Cheers.

Edited December 6, 2023 by TRTOM2498PI

[cp25616]

Interesting info about the cams Tom, much appreciated.

Alan G

[astontr6]

2 minutes ago, cp25616 said:

Interesting info about the cams Tom, much appreciated.

Alan G

I have been using the Newman PH2 cam for 5 years it takes some beating because of the increase in Torque. It is far better than the old CP cam.

Bruce.

[michaelfinnis]

PI cars, CP or CR, should drive perfectly smoothly, if they don't something is wrong. To me it makes more sense to fix the problem rather than throw the lot away and fit a non standard set up which may cause as many problems as it solves. I also wonder how well SU's would work with a CP cam. My understanding is that one of the reasons for adopting PI was that it could tolerate a wilder cam than stromberg/SU carbs.

Peter's suggestion of using an engine driven pump is interesting. This arrangement was used in race cars very successfully for many years. The pump was the same Lucas pump but driven by a belt rather than electric motor, which would get around any problems with the original pump which the road cars were supposed to suffer. You would have to source a bypass valve and other bits, but the system is still used a lot in classic racing so it must be possible. I wonder if anybody has done this on a TR?

For what it is worth I have a CP car with a Lucas pump, and haven't had any problems with the fuel system. It does take a few turns to start if not started for a while, but that is a characteristic of the car and isn't a problem. 

Mike.

[CharlieBubbles]

On 12/6/2023 at 9:08 AM, TRTOM2498PI said:

The CP cars were lumpy on idle, but OK on the move. The CR cars are smoother on idle, and a little easier to live with around town, but I would always go CP every time ! It is a sports car afterall.

When I had my engine built by a top engine builder back in 2011, I did some research on camshafts, and we fitted a Newman PH2/PH3 hybrid cam.  Many other mods, and entire rotating assembly balanced at Vibration Free in Bicester. The car (on Lucas PI), idled beautifully (actually smoother than a CP cam), and made more power everywhere.  You could put it in 4th gear at 1000RPM & it would pull without hesitation.  Malcolm Jones set up the PI system, (Prestige Injection), by using one of his calibrated MU's, plus a set of fuel injectors. We went for a test drive from his place, and he could not believe how the car behaved low down for a high-lift cam and generally how it behaved and pulled on the road.  He said it was one of the sweetest engines he had been in or set-up.

The car has now been converted to EFI, which has transformed it again, and will allow me to try a Newman PH5 cam, which should be interesting.

 

Cheers.

Similar experience more recently Tom on my CR Bosch PI (conversion done about a decade ago with Malcolm Jones by PO)- put in a Newman PH2 Cam when rebuilding the engine (and finally converting it to unleaded which is what started the whole project) last year, then off to Prestige Injection (now Carl Fitchett) for MU refurbishment and balancing to the new cam, new injectors and throttle bodies. Result: so far so very good; no low down lumpiness/grumpiness at all and altogether infinitely smoother and more powerful right the way through the power band. Very glad that (for once) I did the jobs in the right order. Funny how one thing leads to another, and another, and another isn't it?

[harrytr5]

On 12/5/2023 at 10:36 PM, harrytr5 said:

Is that Nic ex NLG?

If it is, how are you Bee keeping going.

Keep to PI

I have been running on EFI since 2010

Using original throttle bodies but changed again 3-4 years ago to Jenvey heritage throttle bodies with inbuilt injectors.

These are look alike webbers.

Very happy with it.

Kept all PI in case and stored.

Regards Harry 

Interesting about the cams.I first fitted a Newman cam PH1 and thought it was the bees knees.Almost like an automatic which suited the EFI and after running in the engine I had it tuned on Emeralds rolling Road.It failed to make power after 3500 RPM and could not make out why.Back to Newmans and suggested the PH2 which they supplied me.

Duly fitted and on the rolling road power restored, but I so loved the PH1 and its drivability. Schnipple in Germany makes the PH1 work on his 2.7 six cylinder TR5/6 engines

and would love to know the secret. The hybrid cam of Toms sounds interesting too but did not know it existed. Efi does not like a lot of overlap due to shock waves and gas reversion. This was explained to me by Emerald. The TR5 /early 6 one is fine.

Regards Harry

[michaelfinnis]

24 minutes ago, harrytr5 said:The hybrid cam of Toms sounds interesting too but did not know it existed. Efi does not like a lot of overlap due to shock waves and gas reversion. This was explained to me by Emerald. The TR5 /early 6 one is fine.

Regards Harry

TR5/earlyTR6 cam has a long overlap, more than the PH1/PH2 ?

[marki]

I fail to see the obsession with Lucas PI, the system wasn’t great 50yrs ago and obviously isn’t great now. It’s rich at low revs and lean at higher relies on the compression/ vacuum of the engine the older and more tired the engine becomes the more fuel will be delivered creating bore wash. SU’s will be 100% reliable better fuel economy and you will only loose a bit at the top end and how many of you often take your car to 6000 ? When I had my 6 I converted to EFI which was the best thing I did but it came at a price. 
Cheers Mark

 

[Mk2 Chopper]

It's because its one of the unique features of the TR5/6.

Everyone accepts its outdated technology, not as efficient as modern systems and more complex than carburettors, but it's part and parcel of a UK/ European spec car. People like to modify and that's great, it's good to have variety. Some of us like to preserve the originality of our cars as much as is possible. 

Triumph soon dropped P.I.,  so it's great to keep and use something that's only fitted to a relatively small number of vehicles, the survivors of a different era. 

Gareth

[cp25616]

Ditto Gareth, well put and well said.

Alan G

[Andy Moltu]

Triumph ran out of money which meant the Lucas PI system came out without the full features that Lucas wanted to use like altitude compensation.

However it is fundamentally reliable, efficient and capable of delivering high power. A reputation in the past gained because of ignorant grease monkeys who assumed all faults with the TR5,6s and 2.5PIs were were down to the PI system and meddled with things they new nothing about!

Clearly it can never match the features of modern efi which adapt fuel and ignition instantly to suit demand.

It's hardly a mega issue to run a bit rich at tick over. Going lean at the top end is often the result of one of 2 things - highly tuned engines capable of demanding more fuel than standard at top revs and WOT (3/4 race cams and above with flowed heads) or because the metering unit has been set too lean because there seems to be an obsession with low CO figures at tick over - keeping the punters happy knowing most of the cars will rarely get over 4000rpm.

Are carbs better? Webers/Dellortos can match the power but usually not the economy. SUs and Strombergs are OK but don't give the absolute performance. When I got my 6 35 years ago the first thing I did was take of the Strombergs and refit the PI and the difference was huge.

[Rob Salisbury]

47 minutes ago, Andy Moltu said:

Triumph ran out of money which meant the Lucas PI system came out without the full features that Lucas wanted to use like altitude compensation.

However it is fundamentally reliable, efficient and capable of delivering high power. A reputation in the past gained because of ignorant grease monkeys who assumed all faults with the TR5,6s and 2.5PIs were were down to the PI system and meddled with things they new nothing about!

Clearly it can never match the features of modern efi which adapt fuel and ignition instantly to suit demand.

It's hardly a mega issue to run a bit rich at tick over. Going lean at the top end is often the result of one of 2 things - highly tuned engines capable of demanding more fuel than standard at top revs and WOT (3/4 race cams and above with flowed heads) or because the metering unit has been set too lean because there seems to be an obsession with low CO figures at tick over - keeping the punters happy knowing most of the cars will rarely get over 4000rpm.

Are carbs better? Webers/Dellortos can match the power but usually not the economy. SUs and Strombergs are OK but don't give the absolute performance. When I got my 6 35 years ago the first thing I did was take of the Strombergs and refit the PI and the difference was huge.

                 100% Agree, considering it's age it is still a brilliant piece of period engineering and when you fully understand just what is going on it is almost infinitely adaptable and tuneable, ...... I ran a Triumph 2.5Pi Auto saloon for almost 24 years and most of that time it was CP spec (head,cam and distributor), one major secret to having a smooth idle is to have the throttle bodies set up either with the Churchill jig or some mechanical means of insuring that they are perfectly aligned to one another.                                                                                   Cheers Rob 

[DRD]

17 hours ago, Andy Moltu said:

Triumph ran out of money which meant the Lucas PI system came out without the full features that Lucas wanted to use like altitude compensation.

However it is fundamentally reliable, efficient and capable of delivering high power. A reputation in the past gained because of ignorant grease monkeys who assumed all faults with the TR5,6s and 2.5PIs were were down to the PI system and meddled with things they new nothing about!

Clearly it can never match the features of modern efi which adapt fuel and ignition instantly to suit demand.

It's hardly a mega issue to run a bit rich at tick over. Going lean at the top end is often the result of one of 2 things - highly tuned engines capable of demanding more fuel than standard at top revs and WOT (3/4 race cams and above with flowed heads) or because the metering unit has been set too lean because there seems to be an obsession with low CO figures at tick over - keeping the punters happy knowing most of the cars will rarely get over 4000rpm.

Are carbs better? Webers/Dellortos can match the power but usually not the economy. SUs and Strombergs are OK but don't give the absolute performance. When I got my 6 35 years ago the first thing I did was take of the Strombergs and refit the PI and the difference was huge.

That just isn't true, SUs can provide similar or better performance as the PI as long as the engine isn't strangled by low compression, a tame camshaft and all the other gubbins the US cars had. 

However if you have a PI car personally I'd keep it original and get it working properly. But if its already a carb car I wouldn't try and convert it to PI. 

[Andy Moltu]

All things being equal 6 separate inlets (Lucas PI, Webers Dellortos) are going to have an advantage over 2 SUs or Strombergs because they effectively give one choke/injector per inlet.

Twin carb set ups are compromised by unequal inlet tracts. 

Otherwise I agree the performance of the US cars was hindered greatly by the state of tune of the engine more than the carbs.

[Tom B]

A "strange" noise from the fuel pump can come from throttled fuel input (blocked filter?) or from poor electrical supply. I wouldn't immediately jump to the conclusion that the pump itself is on the way out. My '70 PI is a joy to drive and I wouldn't dream of changing to carbs...