Weber/SU

[mcgrison]

Good morning,

Is there somebody who can tell me his experience in switching from SUs to Webers on a TR4? I assume that , if you drive mainly under 3000 rpm it doesn't change much. Am I correct?Thank you!

[ianc]

Both 4VC and 3VC have engines which are modified for rallying.

My car (4VC) is on HS6 SUs.  3VC is on Webers, and I have driven 3VC to & from the Midlands (some 70 miles each way) for car shows on a couple of occasions.

My car is very easy to start and the choke can be pushed home after about a mile, even on a cold day.

I did not find 3VC easy to start and it stuttered a lot for quite some miles until really warm.

In driving, using some 4000 rpm, I couldn't detect any difference in performance.

From the curves obtained on a rolling road, I know that 4VC's torque is practically flat from 3800 to 5100, starting to reduce slightly at 5300.

On a standard TR4, torque starts to fall from about 3800.  4VC's torque is over 30% higher than standard at 4950 rpm.

If you have SUs, I would stick with them unless you expect to be using over 4500 a great deal of the time.

If you PM me with your home email address, I can send you the comparative curves.

Ian Cornish

[Motorsport Mickey]

Plus 1 on the above, also unless you use those plus 5000 revs you won't find much improvement in performance. As Ian says the car will benefit from the flatter torque range of the Webers set at 3800 up to low 5000s which is where the SUs standard cam and carburation is at maximum (3500 revs on standard cam and dropping at 3800). My race TR4 would give 148hp at back wheels on 1 3/4 SU carbs (race flowed and modified) and 165 at trhe back wheels on Weber 45s similar preparation. The Webers will give large gains when you get "urgent" with the throttle but you got to use the revs. The SUs are much nicer for cruising and keeping the memsahib happy, it's drivers preferences, the Webers sound great !

Mick Richards

[ntc]

It depends on the engine spec and if the Weber’s are set to suit 

[North London Mike]

 

+ 1 for both Ian & Mick

LNK started life on SU's, and is currently on WEBERS, so 10 yrs on SUs and and 5 on WEBERS. Most people move to webers as part of a performance upgrade normally including a change of cam and some other trick bits.

If your engine is standard or you are not making any changes, stay with the SU's, great carbs. All the webers do is use more fuel. If you're fitting a longer duration cam, the webers allow you to max out at higher revs, they're more playful, a road run on webers is more of a mission. You can cruise, keeping the second choke closed but its counter intuitive. The price is about 5mpg

Sometimes its just a itch we need to scratch...............

I love my Webers 

[mcgrison]

53 minutes ago, ianc said:

Both 4VC and 3VC have engines which are modified for rallying.

My car (4VC) is on HS6 SUs.  3VC is on Webers, and I have driven 3VC to & from the Midlands (some 70 miles each way) for car shows on a couple of occasions.

My car is very easy to start and the choke can be pushed home after about a mile, even on a cold day.

I did not find 3VC easy to start and it stuttered a lot for quite some miles until really warm.

In driving, using some 4000 rpm, I couldn't detect any difference in performance.

From the curves obtained on a rolling road, I know that 4VC's torque is practically flat from 3800 to 5100, starting to reduce slightly at 5300.

On a standard TR4, torque starts to fall from about 3800.  4VC's torque is over 30% higher than standard at 4950 rpm.

If you have SUs, I would stick with them unless you expect to be using over 4500 a great deal of the time.

If you PM me with your home email address, I can send you the comparative curves.

Ian Cornish

 

[mcgrison]

1 hour ago, ianc said:

Both 4VC and 3VC have engines which are modified for rallying.

My car (4VC) is on HS6 SUs.  3VC is on Webers, and I have driven 3VC to & from the Midlands (some 70 miles each way) for car shows on a couple of occasions.

My car is very easy to start and the choke can be pushed home after about a mile, even on a cold day.

I did not find 3VC easy to start and it stuttered a lot for quite some miles until really warm.

In driving, using some 4000 rpm, I couldn't detect any difference in performance.

From the curves obtained on a rolling road, I know that 4VC's torque is practically flat from 3800 to 5100, starting to reduce slightly at 5300.

On a standard TR4, torque starts to fall from about 3800.  4VC's torque is over 30% higher than standard at 4950 rpm.

If you have SUs, I would stick with them unless you expect to be using over 4500 a great deal of the time.

If you PM me with your home email address, I can send you the comparative curves.

Ian Cornish

Thanks everybody. As I am a pacific tourist, I will stick to my good SUs

 

Edited February 21, 2021 by mcgrison

[mcgrison]

16 minutes ago, North London Mike said:

 

+ 1 for both Ian & Mick

LNK started life on SU's, and is currently on WEBERS, so 10 yrs on SUs and and 5 on WEBERS. Most people move to webers as part of a performance upgrade normally including a change of cam and some other trick bits.

If your engine is standard or you are not making any changes, stay with the SU's, great carbs. All the webers do is use more fuel. If you're fitting a longer duration cam, the webers allow you to max out at higher revs, they're more playful, a road run on webers is more of a mission. You can cruise, keeping the second choke closed but its counter intuitive. The price is about 5mpg

Sometimes its just a itch we need to scratch...............

I love my Webers 

 

17 minutes ago, North London Mike said:

 

+ 1 for both Ian & Mick

LNK started life on SU's, and is currently on WEBERS, so 10 yrs on SUs and and 5 on WEBERS. Most people move to webers as part of a performance upgrade normally including a change of cam and some other trick bits.

If your engine is standard or you are not making any changes, stay with the SU's, great carbs. All the webers do is use more fuel. If you're fitting a longer duration cam, the webers allow you to max out at higher revs, they're more playful, a road run on webers is more of a mission. You can cruise, keeping the second choke closed but its counter intuitive. The price is about 5mpg

Sometimes its just a itch we need to scratch...............

I love my Webers 

A beautiful and clean engine bay!

 

[Z320]

A friend of mine drives Weber on his TR6,

and when every I ask hin about running on after switching off the ignition his answer is "not at all".

Any experience about that from other Weber users would be great, please.

 

Edited February 21, 2021 by Z320

[ntc]

12 minutes ago, Z320 said:

A friend of mine drives Weber on his TR6,

and when every I ask hin about running on after switching off the ignition his answer is "not at all".

Any experience about that from other Weber users would be great, please.

 

Never had it on any of my cars 

[roy53]

nor me

[Z320]

Thank you guys,

sorry that stupid question: I guess you both have Webers on which TRs?

Ciao, Marco

Edited February 21, 2021 by Z320

[Rob Salisbury]

If you were to fit Webers and have them set up properly I very strongly doubt you'd go back to your SUs.

Just the sound they make is worth every penny and some!!

Cheers Rob

[North London Mike]

Webers on LNK, properly set up, jetted, rolling road etc. Starts as it should and never runs on when finished with engine (my old SU's did occasionally thought !)

[Andy Moltu]

If you are barely exploring half the rev range, it begs the question as to why you would want to spend money on a modification that won’t make a significant difference until you explore higher rev ranges with other modifications to utilise the upper revranges.

[ntc]

18 minutes ago, Andy Moltu said:

If you are barely exploring half the rev range, it begs the question as to why you would want to spend money on a modification that won’t make a significant difference until you explore higher rev ranges with other modifications to utilise the upper revranges.

Single fuel and air delivery to each cylinder is more efficient simple 

[Bleednipple]

I have SUs on my TR4 and will probably keep them, but while there are some Weber experts on here... I have a pair of 40DCOEs on another car I recently acquired (an Alfa). They have no cold start circuits fitted I think (certainly have no actuation cables), so are a minor pain to start - I have to resort a quick spray of Easy Start when cold. I'm not going to fiddle with them myself but can anyone explain in simple terms the cold start gadgetry on sidedraught Webers?

(Or maybe I'm just using a poor starting technique!)

Nigel

[Motorsport Mickey]

I always give them 2 full depressions down to the floor before attempting to start ...and they do. There are choke "gadgetry " on floats but they've never been connected on cars I drove. I think the Dellortos will start in the same menner, I should avoid the Easy Start if you can, broken rings can be the result, it explodes rather than burning quickly.

 

Mick Richards

[roy53]

13 hours ago, Z320 said:

Thank you guys,

sorry that stupid question: I guess you both have Webers on which TRs?

Ciao, Marco

Both 4 cyl and 6 cyl TRs

Roy

[roy53]

10 hours ago, Motorsport Mickey said:

I always give them 2 full depressions down to the floor before attempting to start ...and they do. 

 

Mick Richards

Same here 

Roy

[Bleednipple]

10 hours ago, Motorsport Mickey said:

I always give them 2 full depressions down to the floor before attempting to start ...and they do. There are choke "gadgetry " on floats but they've never been connected on cars I drove. I think the Dellortos will start in the same menner, I should avoid the Easy Start if you can, broken rings can be the result, it explodes rather than burning quickly.

 

Mick Richards

Thanks Mick and Roy. I tried them again this morning on the Alfa and three pre-pumps and then subtle tickling of the throttle was a winning recipe. Think I now have the knack.

Actually tempted now to put Webers (or Dellortos) on my TR4 which is at stage 2 tune and has great low end grunt but runs out of puff a bit from about 4500 (mainly on the uphills in road rallying). And prob worth it anyway the glorious noise!

Nigel  

[ntc]

I never do just full choke instant start then strait off, no popping at all, guess I set mine up different.

[Bleednipple]

4 minutes ago, ntc said:

I never do just full choke instant start then strait off, no popping at all, guess I set mine up different.

Yes sounds like you have 'chokes' (ie cold start devices) connected on your carbs ie you have a knob to pull. I think a lot of Weber setups omit them.

Nigel

[stuart]

Just to be different I have Dellortos on mine and couple of pumps on the throttle and then instant start, they do have choke mechanism but I have never bothered to connect it,I suspect if I did then it would start without pumps. FWIW anyone who knows me knows I do use all the performance available with it and yet it will still give good (30+) MPG even then.

Stuart.

[Andy Moltu]

14 hours ago, ntc said:

Single fuel and air delivery to each cylinder is more efficient simple 

That depends on your definition of efficiency.

Better air flow at any given point in the rev range/throttle openings?

Better fuel economy?

Better bling factor?

I would argue that if the driver is only reving up to 3000 rpm the same effect in terms of power could be achieved by reving to 3500 rpm at no additional cost and probably better fuel economy. If the driver is happy to explore the higher echelons of the rev range then Webers might be worth exploring but hard to justify.

What would a twin Weber set up cost?