injection/carb ??

[21er]

Hi all

Bit new to the TR6 world, generally i'm swatting up on the models and specs or the cars available, anyway to my point..theres a TR6 on ebay with the item description, "Fuel injection system removed and replaced with triple Webber DCOE 40's, this is a massive improvement on the fuel injection system (renowned for poor fuel consumption & very unserviceable)" all i'd like to know is that is this statement a valid point?

 

jason

[RogerH]

Hi Jason,

the PI when set well is quite good on fuel consumption and in the hands of a knowledgable engineer can be kept in tune very well.

3 webers will give you very good performance but at the expense of economy. Don't forget they also need to be kept in tune.

If you wany economy go for 2 SU's !!!

 

I would have thought anybody stating what you have posted doesn't know what he is saying or is simply trying it on.

 

Roger

[Richard Crawley]

Hi Jason, welcome to the forum.

I agree with Roger; they make lovely noises but I don’t agree that 3x Webbers are a massive improvement over PI at all & if the engine is developing the power it should be, fuel consumption is likely to be worse not better than a correctly set up PI. In my view, Webbers can be a very good solution for getting decent performance from an imported carb engine car or race engines but you could still do the same with a correctly set up PI.

 

Watch out that it's not a converted import, these don't command the same prices as an original UK PI car.

[TR6 Poor]

Well, you won't be able to drive a Webber car in the mountains, without rejetting. So, vacations to the mountains would be out of the question. I wonder if PI gives problems with a change in elevation?

[Guest ntc]

Hi Jason, welcome to the forum.

I agree with Roger; they make lovely noises but I don’t agree that 3x Webbers are a massive improvement over PI at all & if the engine is developing the power it should be, fuel consumption is likely to be worse not better than a correctly set up PI. In my view, Webbers can be a very good solution for getting decent performance from an imported carb engine car or race engines but you could still do the same with a correctly set up PI.

 

Watch out that it's not a converted import, these don't command the same prices as an original UK PI car.

 

Hi Jason

Another point of view,fitting Weber's to an unmodified engine is a waste of time however if other mod's have been carried out they can and will out perform a mechanical injection system including economy

 

Neil

[Guest ntc]

Well, you won't be able to drive a Webber car in the mountains, without rejetting. So, vacations to the mountains would be out of the question. I wonder if PI gives problems with a change in elevation?

 

I think you will find it is the other way round

 

Neil

[RogerH]

I think Neil is right. The early (if not all) TR6's had fun in the mountains, changing plugs every 10 or so miles due to over rich fouling.

 

Roger

[TR6 Poor]

Well, I spoke to a person who worked for Weber, owns a company in California now, which manufactures FI, or PI systems. He drove a Weber TR6 while there quite a bit, and he told me he wouldn't want to be in one at 5k feet. If I remeber right, said the car made 130 some HP, didn't say where. He was in management at Weber years ago, a British person. There is nothing to compensation for altitude built into Webers that I am aware of? I have seen articles by people who attempted to drive one in the mountains overhere, when you get up to a certain elevation, the car will not even run, as it is too rich.

[Guest ntc]

Well, I spoke to a person who worked for Weber, owns a company in California now, which manufactures FI, or PI systems. He drove a Weber TR6 while there quite a bit, and he told me he wouldn't want to be in one at 5k feet. If I remeber right, said the car made 130 some HP, didn't say where. He was in management at Weber years ago, a British person. There is nothing to compensation for altitude built into Webers that I am aware of? I have seen articles by people who attempted to drive one in the mountains overhere, when you get up to a certain elevation, the car will not even run, as it is too rich.

 

Sounds like he had fitted them to one of your stock engine's then

 

Neil

[foster461]

I would say that an engine configured for PI (cam, head etc) will develop pretty much the same power on correctly set up Webers although the curve and the torque might be a different. My personal experience is that fuel consumption is not significantly different from the two Strombergs when driving like a normal person. Obviously if your driving style is on/off the fuel consumption will be worse as the Webers can flow a lot of fuel when asked. I had some out of band email exchanges with Tom F on fuel consumption and I think his experience was similar to mine.

 

I would not go out of my way to convert a PI car to Webers but I can imagine some scenarios where that might make sense.

 

I have no experience with Webers at significant altitude and I dont recall this coming up as an issue although it is a well known problem with the PI. If the Webers do have problems at altitude I'd like to hear more !.

 

Stan

[Chris59]

I agree with Roger, and others guys, as I drive both PI and carbs TRs and 2500 saloons since a long time : when set well and maintain, nothing is better than a Lucas PI.

I use as often as possible my 2500 PI Mk2 saloon for rallys with my family, and no problem since 10 years and nearly 40 000 km, thanks to Malcolm (Prestige and Developments) job.

On another side, if not well tuned, it may be a nighmare

 

Cheers,

 

Chris.

[Alec Pringle]

Lucas PI and Weber systems can both work well on 6-pot Triumphs, but the PI doesn't like excessive altitude without a little judicious tweaking.

 

I haven't used a triple-Webered 6 over the Alps, but I have used other Weber-carbed engines and without exception they didn't take kindly to thinner air. I'm referring here to 70s Weber carbs, maybe DCOEs have acquired some extra technology since those days and can now cope better with altitude variation ?

 

Cheers,

 

Alec

[Kevin Warrington]

We struggled a little in September 2007 in our TR6 PI coming over the top of the Grand St Bernard (8,200 feet, I think). Anyone with any sense would have gone through the tunnel which is a couple of thousand feet lower.

 

We were running a little rich in any case, even at sea level and during our crossing of the pass, the road was being resurfaced with long stretches of single track road controlled by lights. It was a bright and warm day, even with snow on the ground at the top of the pass and I honestly thought that we were going to have to turn around and go back to lower altitude. The exhaust was a rich black and stank of petrol. Once we'd got over the top and started the descent, all was fine again.

 

Kevin

[D1070]

Having scaled the infamous Stelvio Pass(just under 9000ft) on a couple of occasions with my triple webbered

5 i can report no loss of power/rough running on either occasion.

However there is little doubt,from my experience,that fuel consumption is higher when compared

to the PI equiped 6s i have had in the past.

[Tom Fremont]

I had some out of band email exchanges with Tom F on fuel consumption and I think his experience was similar to mine.

 

Now that I've been " outed ", here's what I get for fuel economy, in Imperial gallons: 30 mpg on 2-lane roads with minimal stop-starts and scant sporting behaviour / 24 mpg overall with every type of driving thrown in. Cam is CP type ( 150 BHP ). Overdrive equipped. Best I've ever gotten with the triple Webers is 33.6 mpg @ 60-65 mph.

 

Webers can give great performance with poor fuel economy. Many have stopped short of completing the tuning diligence, then slandered the carbs.

 

I'd really like to get to the bottom of the altitude question. The only part of the carb with delivers fuel without regard to air-mass flow-through is the accelerator pump, so I can guess these might do with leaner jets. Otherwise I'd expect them to be OK...

[Tom Fremont]

I had some out of band email exchanges with Tom F on fuel consumption and I think his experience was similar to mine.

 

Now that I've been " outed ", here's what I get for fuel economy, in Imperial gallons: 30 mpg on 2-lane roads with minimal stop-starts and scant sporting behaviour / 24 mpg overall with every type of driving thrown in. Cam is CP type ( 150 BHP ). Overdrive equipped. Best I've ever gotten with the triple Webers is 33.6 mpg @ 60-65 mph.

 

Webers can give great performance with poor fuel economy. Many have stopped short of completing the tuning diligence, then slandered the carbs.

 

I'd really like to get to the bottom of the altitude question. The only part of the carb with delivers fuel without regard to air-mass flow-through is the accelerator pump, so I can guess these might do with leaner jets. Otherwise I'd expect them to be OK...

[tony r]

Now that I've been " outed ", here's what I get for fuel economy, in Imperial gallons: 30 mpg on 2-lane roads with minimal stop-starts and scant sporting behaviour / 24 mpg overall with every type of driving thrown in. Cam is CP type ( 150 BHP ). Overdrive equipped. Best I've ever gotten with the triple Webers is 33.6 mpg @ 60-65 mph.

 

Webers can give great performance with poor fuel economy. Many have stopped short of completing the tuning diligence, then slandered the carbs.

 

I'd really like to get to the bottom of the altitude question. The only part of the carb with delivers fuel without regard to air-mass flow-through is the accelerator pump, so I can guess these might do with leaner jets. Otherwise I'd expect them to be OK...

[tony r]

Hi Guys

Some thoughts for the pot. Based on experience with a 1971 US TR6.

Single biggest improvement installing a gas flowed exhaust manifold to replace the original 6-1 cast manifold.

Now installed Triumph 2000 Saloon PI Engine. Balanced, Stage 2 Cylinder Head inc "Swan Neck" Stainless Valves, Half Race Camshaft, Profiled Distributor to Match, Lumenition Ingnition, V-Notched Plugs. Using Twin HS6 SU Carbs. Set 19 Degrees BTDC and CO c 2.5%. Produced 140 BHP @ 4000 RPM @ Wheels @ Rolling Road/Tuning Specialist near Cambridge. Does 30-33 MPG on long runs. Pulls well from 1500 RPM not too happy about doing 30 MPH in Top Gear in Town.

Would I install Mech PI? Probably not based on the simplicity, performance and relaibility of the curent set up?

Would I Install Triple Webers? Probably not based on prof advice which sugests only nominal increase in power and lower fuel economy

Would I install Electronic PI? Probably yes if I had the money spare. Smoother performance and more power.

Hope this helps the debate. Anyone else done similar?

Tony R

[Tom Fremont]

Would I Install Triple Webers? Probably not based on prof advice which sugests only nominal increase in power and lower fuel economy

You'll never know for sure without trying them on your engine When I switched to these, making no other changes the difference was like night and day. Using 28mm chokes ( then ) I figured the " opening " was about 38% more than what (2) Strombergs, or S.U. HS6s gave. Using 30s and 32s now the strangling is virtually gone I'd say

 

When we're happy we tend to tune out arguments in support of change ( For example, did ou notice my post about 33+ mpg with triple Webers ) Just to toss in a gratuitous S.W.A.G. for your engine, I'd say you'd achieve another ~ 15 BHP on mapped triple Webers, if it's good for 6000 rpm duty. On a full race engine in the '60s Kastner was able to get 30 additional HP with the Lucas P.I. ( which he hated; SCCA wouldn't let him use Webers which he loves ) for 190 max vs. 160 with twin Strombergs.

[trfella]

I think PI can sound lovely too

 

What's the crack with these ram pipes?

[stephen cooper]

Ah very old video that, car no longer running the ToiletTune exhaust, has a proper exhaust and sounds much better.

 

FYI they lengthen the inlet tract and obv get rid of the air filter/plenum restrictions.

 

http://www.jagclub.ru/triumph_tun.html

 

http://triumphwestoz.blogspot.com/

 

make interesting reading

[asland]

Hi

 

Since my '71 TR6 PI CP52... was bought as a restoration project and is still under restoration, my experience with the PI system is from a friends TR5. I have though quite some experience with Webers and SU’s.

 

I feel Webers are presented unfavourably above which I feel is misleading and the conclusions not based on facts. I may be committing suicide by speaking out for Webers, but I take the chance.

 

1) Problems at high altitudes

Neither Lucas PI, SU nor Weber have direct correction for altitude. This is 90’s on technology (electronic injection) where the inflowing air is measured by weight/mass not by sheer volume like the 3 systems above. Of the 3, from a theoretical point of view, the SU’s are probably best suited for high altitude, though I have so far been unable to conclude based on years of experience.

Webers 0

Lucas 0

SU 1

 

2) Power

A tuned Lucas and Weber setup will produce more power that SU! The SU may have more torque at low rpm, because the variable venturi/choke will generate higher air velocity at low rpm. and thereby sucking fuel more effectively. At the same time this variable venture, will – due to its construction – present a restriction at high rpm/velocities. Theoretically, the Lucas will have the edge on Webers once again because the Webers have fixed chokes which will restrict airflow at high rpm. Lucas PI does not need chokes as the fuel are not sucked in but pumped into the inlet. The difference is marginal though.

Webers 1

Lucas 1

SU 0

 

3) MPG

Theoretically, air and fuel should be mixed in a ratio of appr.13:1 by mass ( stochiometric combustion). In practice, the highest efficiency and consequently; power, is achieved at a ratio closer to 12:1 i.e. a slightly richer mixture that stochiometric. Today’s engines run lean due to environmental reasons – not performance!! This makes the engine less efficient, but will not produce amongst others less CO - which is said to have a negative effect on the atmosphere.

The main purpose of any induction system, is to maintain a predefined ratio between air and fuel. In addition there is a relation between the size of the fuel droplets and the efficiency. The smaller the droplets; the greater the surface of the fuel will be and the more area the air/fuel reaction process can take place.

The SU is a lousy instrument for making microscopic fuel droplets. Webers are much more of a high class instrument for making droplets and mixing them in the correct ratio to the air. Again the Lucas may be concluded as the winner as the fuel is sprayed into the inlet under pressure and not sucked in, but if so marginally in front of Weber since the Lucas spray nozzle is not very good.

Webers 1

Lucas 1

SU 0

 

4) Mechanical design and maintenance

The SU is definitely a rouged piece of equipment. The disadvantage with SU are - they have many moving parts that wear. The needle, nozzle and the spindle to mention 3.Design is the Achilles heal of the Lucas PI. Need I detail this further? The benefit of the Weber is that it has very few moving parts and those that are moving are of very high quality. The spindles f.ex. run in ball bearings not like SU – directly in the carb body. Wear along the spindles, will upset the air/fuel mixture and will reduce power and mpg. Once set up correctly !!!!! the Webers will overall outperform the 2 opponents overall.

Webers 1

Lucas 0

SU 0

 

5) Price

Webers 0

Lucas 0

SU 1

 

 

TOTAL SCORE subjectively!!!

Webers 3

Lucas 2

SU 2

 

To be continued!!! I have for some time, had 3 40DCOE Webers in the back of my garage. I have just recently bought a manifold for the Weber’s and plan to run a comparison test between the Weber and the Lucas PI. Anybody wants an update???

 

Cheers

Hal

Edited January 26, 2009 by asland

[johnny250]

Thanks for those observations Hal... I was interested to learn that Webers and PI are better than SU's regarding economy, and that they have fewer parts, I didn't realise that......

 

John

[Tom Fremont]

Thanks for those observations Hal... I was interested to learn that Webers and PI are better than SU's regarding economy, and that they have fewer parts, I didn't realise that......

 

John

 

Hi John,

 

I surmise you're happy with your S.U.s Seems you just may have tuned out the operative word " moving " in front of " parts "

 

Hal, a 1st hand comparison is yet wanting in the discussion [ at least in terms of recent postings newer than 3 years or so ]. Not that it will persuade the happy among us to change though...

[foster461]

Seems you just may have tuned out the operative word " moving " in front of " parts "

 

Yup. There is a lot of parts in 3xdcoe's (essentially 6 individual carbs) and thankfully few of them move..