New SUs running very rich

[DRD]

If SUs could have been made to work sensibly with a PI cam . . . . . Triumph wouldn't have gone to the bother of fitting Lucas PI.

 

The more sensible answer might have been to utilise, for example, 2500S component as a known quantity . . . . . rather than trying to knock the corners off octagonal wheels.

 

I'm not sure why you're worrying about insulting the garage - if they knew what they were about then they wouldn't have wasted their time and yours with trying to adapt SUs to a PI head/cam/dissie . . . . . .

 

Find someone who knows what they're doing and start again.

 

Cheers,

 

Alec

Not true, with the appropriate expertise & equipment you can setup HS6 carbs to work well with hotter cams. But everything is a compromise and the overall the PI system gave good power and flexibility for a wider range of driving conditions.

[Peter Cobbold]

The garage say they set the carbs up for 2% CO at idle and 3% at 3000 rpm. I have no reason to doubt. They even bought new measuring equipment after I complained. They said they were not 100% sure about the old equipment. They measure through 2 holes front and back in the exhaust manifold. I now have after 600 miles 9.3% CO at idle and 12.6% CO at 3000 rpm. One problem I have is, the garage is the other end of the country, but that's a long story.

I had with my strombergs with normal driving a fuel consumption over 28 mpg and now 20 mpg. The biggest problem will be the MOT next year.This is a standard sort of conversion they have been doing for years. That's why I don't undertsand what is going wrong or changing.

The change in CO after 600miles might be the sparks changing not the carbs. New unlubricated plastic points can wear that fast. So check the static timng hasn't gone retarded badly.

 

20mpg points to the wrong needle, and its easy to change to one of those already found to work- see above.

 

Peter

[TR NIALL]

@ Pual,

The saloon engines were canted over to the the exhaust side, so I guess the saloon manifold on a 6 will slope down steeper to the head..

?

Peter

Yes it will but if one wants it level you can get an 8 degree slope machined onto it but I don't think it's necessary on a TR6.

I Think the Angle on the Manifold was only used to miss the Suspension Turret on the 2.5 Saloon things are very close under the Bonnet.

[Peter Douglas Winn]

After all this I am starting to wonder if the problem is somewhere else. e.g. ignition. I will go and check the ignition values I have a good strobe. I will measure the dwell angle and take the plugs out. Also look at the dissy cap. I cannot believe the richness adjusting screws are vibrating loose after a few miles.

[TR NIALL]

Niall

 

At the risk of drifting off topic, what benefit does the 2.5S manifold give over the std TR6? Is there more of a difference than just the carb mounting angle?

 

Paul

Hi Paul are you talking TR6 American Manifold if so they used Stroms with only 2 Carb fixings so you need to do a fair bit of adapting to accept SU Carbs as they are 4 stud Mounting and are slightly bigger spaced,you need to slot the Mounting Holes on the SU Carb Bodies.

To me the 2.5 Manifold is the proper one to use,I also think the Flow is so much better than the American one but I ain't got any figures to back that up only if they were the same why didn't Triumph use the American one with the Stromberg or with an adaptor plate for the 1"3/4 SU and don't forget the 2.5 Manifold and 1"3/4 SUs were only used specifically on the 2.5s for good reasons me thinks.

Are the American Manifolds 1"1/2 if so that Manifold would be restrictive as the 2.5s is one is 1"3/4.

Edited August 4, 2017 by TR NIALL

[Peter Cobbold]

After all this I am starting to wonder if the problem is somewhere else. e.g. ignition. I will go and check the ignition values I have a good strobe. I will measure the dwell angle and take the plugs out. Also look at the dissy cap. I cannot believe the richness adjusting screws are vibrating loose after a few miles.

Good. But a badly retarded spark is not going to make the difference between 28 and 20 mpg although it can mess up the idle CO.

 

Why do you assume your needles are correct when others on here have told you otherwise ?? There's not a lot of point in us replying if the garage and carb supplier are assumed to be perfect and above all possibility of being wrong....

 

Peter

[TR NIALL]

Just for some clarification

BDQ Needles were used on the 2.0 Dolly Sprint

BCY Needles on the 2.5 Saloon

I'm using BDM Needles Yellow Springs on a 2.5cp after advice from ANDREW Turner who is an SU Carb Specialist.

[PaulAA]

Hi Paul are you talking TR6 American Manifold if so they used Stroms with only 2 Carb fixings so you need to do a fair bit of adapting to accept SU Carbs as they are 4 stud Mounting and are slightly bigger spaced,you need to slot the Mounting Holes on the SU Carb Bodies.

To me the 2.5 Manifold is the proper one to use,I also think the Flow is so much better than the American one but I ain't got any figures to back that up only if they were the same why didn't Triumph use the American one with the Stromberg or with an adaptor plate for the 1"3/4 SU and don't forget the 2.5 Manifold and 1"3/4 SUs were only used specifically on the 2.5s for good reasons me thinks.

Are the American Manifolds 1"1/2 if so that Manifold would be restrictive as the 2.5s is one is 1"3/4.

 

Hi Niall

 

Yes, the CF manifold. It's a minor detail, but the swap from Strombergs to SUs on mine was straightforward and didn't need much adaptation.

 

I'm running the HS6s with a head skimmed to 9:1, Wishbone 518 cam, BDM needles, yellow springs and no vacuum connection (I tried fitting a converter to the retard capsule on the dizzy and it didn't work. Then it broke). I've not RR'ed it, so no figures, but it has considerably more poke than it did when stock, but it runs out of breath at 4k rpm. Received wisdom is that there is a constriction in the manifold airways to cyl 2 & 5, so I'm wondering if the 2500S manifold solves that problem.

 

Apologies to the OP for digressing!

 

Paul

[TR NIALL]

Hi Niall

 

Yes, the CF manifold. It's a minor detail, but the swap from Strombergs to SUs on mine was straightforward and didn't need much adaptation.

 

I'm running the HS6s with a head skimmed to 9:1, Wishbone 518 cam, BDM needles, yellow springs and no vacuum connection (I tried fitting a converter to the retard capsule on the dizzy and it didn't work. Then it broke). I've not RR'ed it, so no figures, but it has considerably more poke than it did when stock, but it runs out of breath at 4k rpm. Received wisdom is that there is a constriction in the manifold airways to cyl 2 & 5, so I'm wondering if the 2500S manifold solves that problem.

 

Apologies to the OP for digressing!

 

Paul

Going to PM you.

[Peter Douglas Winn]

I have just done some measuring and looking. Plugs are totally black. All plugs are working. All plugs look to have a simular gap. Eye measurent. Dewell angle is 34°. Ignition 850 rpm 16°.

I will have to get somebody to press the accelerator for the higher reading but the advance retard is working to some extent.

Edited August 4, 2017 by Peter Douglas Winn

[dingle]

Make sure that the float chambers are level, regardless of the angle of the manifold.

 

Berry

[Waldi]

If the SU's are of the type that lower the main jet as a choke (the part where the needle goes in/out) make sure they return fully upwards after the choke is used. They can sometimes stick, resulting in richer mixture.

Waldi

[Peter Douglas Winn]

If the choke is sticking after the car came back from the garage, it would explain a lot. I would have thought that when waiting at a traffic light one would notice higher revs.

 

Peter, Re the needle I don't know if they are correct but I do know the carbs were set up for CO values three times and the values changed negatively. Please explain why the shape of the needle causes these values to change. I don't see what the shape of the needle have to do with the values changing. Perhaps I am missing something. The garage always measures at 850 revs and 3000 revs.

The problem is why do the values change after such a short time? This is not fine tuning, it is major adjustments.

Edited August 5, 2017 by Peter Douglas Winn

[Peter Cobbold]

If the choke is sticking after the car came back from the garage, it would explain a lot. I would have thought that when waiting at a traffic light one would notice higher revs.

 

Peter, Re the needle I don't know if they are correct but I do know the carbs were set up for CO values three times and the values changed negatively. Please explain why the shape of the needle causes these values to change. I don't see what the shape of the needle have to do with the values changing. Perhaps I am missing something. The garage always measures at 850 revs and 3000 revs.

The problem is why do the values change after such a short time? This is not fine tuning, it is major adjustments.

Carboned-up plugs are well known to raise CO.

 

Checking CO at idle or 3000rpm stationary tells you nothing at all about the mixture when driving. The idle test is only valid if the needles are known to be right for that engine. But yours are not......because

1 your plugs are black with soot.

2. as George and DRD have pointed out your needle profile is way richer than the ones they know to work well.

Change to the needles suggested by Niall, George or DRD. And fit new plugs.

 

And find a garage that understands the most elementary operation of the si engine. They should have read the plugs, certainly fitted new before checking CO, and suspected the needles. And they should know it is impossible to assess SU needles with the engine unloaded.

 

Trust the advice freely given here by TRers who know from experience how to tune SUs to the TR6 engine,

 

Peter

Edited August 5, 2017 by Peter Cobbold

[BlueTR3A-5EKT]

If the choke is sticking after the car came back from the garage, it would explain a lot. I would have thought that when waiting at a traffic light one would notice higher revs.

 

Peter, Re the needle I don't know if they are correct but I do know the carbs were set up for CO values three times and the values changed negatively. Please explain why the shape of the needle causes these values to change. I don't see what the shape of the needle have to do with the values changing. Perhaps I am missing something. The garage always measures at 850 revs and 3000 revs.

The problem is why do the values change after such a short time? This is not fine tuning, it is major adjustments.

What load do the garage apply on their rolling road to the engine when they check the CO at 3000 rpm - or are they just revving an engine ?

Engine power load will change the fuel demand, See Peter's SU talk notes on this. To do with throttle opening position etc.

 

If you are using too much petrol you may have 'bore wash' (oil is washed off the cylinder walls by excessive fuel), so the engine will need a rebore soon anyway. You could then get the thing set up on a dynamometer after rebuild.

 

Peter W

[Peter Douglas Winn]

I think we are missing the point. We have 2 problems, very high consumption which could be as a result of wrong needles, choke etc. The garage should be able to hack that one. They have already put in other needles. I will give them the Club experts info. concerning the needles. Thank god it is garage that listens to their customers and not advers to suggestions.

Re: rolling road I do not know the answer. I know they have had the car on a rolling road but when and how I just don't know. I will ask them this question.

 

The more difficut one is the CO values have changed drastically. They have not gone back to the origina values. How can a different needle affect the CO values? What could be the connection.

 

Re Bore Wash it was at the garage because of a rebore that started it all off.

[Peter Cobbold]

NO Peter, it is you who is going around in circles. We dont appear to be getting through your belief that (a) the garage is right and ( the new carbs are right.

Listen to us and put in two correct needles. And you'll be sorted. And new plugs.

====

CO is a measure of incompletely combusted fuel. Not enough oxygen to burn all the fuel to CO2. In other words high CO while driving or on rolling road means its too rich. CO vs AFR varies with engine to some extent. A representative relationship - where sparks and plugs are working correctly- looks like this:

http://www.crypton.co.za/Tto%20know/Emissions/airfuelratio5big.GIF

 

Idle CO can be high since idle mixture is set rich. On this graph 5% CO = AFR 12. BUT idle measurements tell you - and that garage - nothing about driving mixture.

 

I think you have two problems. Way over-rich needles that are fouling the plugs. The more the plugs soot up as you drive the idle CO goes even higher. Assuming the fuel level in the jet has been confirmed to be correct.

 

Your third problem is that garage. As they have had your TR on their rolling road they should have found the over-rich running and identified it.....easily. Ditch them, fit new needles and plugs yourself.

 

Peter

Edited August 5, 2017 by Peter Cobbold

[Peter Douglas Winn]

I have for the first time looked at the difference between the needles BCE BDM BAG BCY. It seems that my needels are over the top. I will pass this info to my garage.

[DRD]

I have for the first time looked at the difference between the needles BCE BDM BAG BCY. It seems that my needels are over the top. I will pass this info to my garage.

 

Hope this fixes the issue for you.

[Peter Douglas Winn]

I amnot sure but I think they use a Lambe at the front and back of the exhaust manifold. There are 2 holes blocked off with washers and screws.

[Peter Douglas Winn]

Peter.

I think I have understood and I have told the garage what has been said about BCE versis BDM and BCY needles.

I have also told them about the Sparkplugs and the CO.

Thirdly about setting up the CO values under load.

We will see how they react.

[Peter Douglas Winn]

I have sent your comments to the garage. Unfortunately they are on holiday, so no reply. I cannot do anything without permission, the carbs are sealed and have a guarantee. If I cleaned the plugs and advanced the ignition would that give me a temporally help?

[Peter Cobbold]

If the garage knew they had set up the carbs right there'd be no need to "seal and guarantee". Because you would never need to investigate them. In my view the 'seal and guarantee' is designed lead you into believing they have spent time and effort on the SUs.

 

Have you checked them out on line? or spoken with other classic owners who are customers?

What's their website?

 

Find a local garage with a portable UEGO they can use to record AFR as your drive ( the sensor is poked up the tailpipe).

Get a written report and act against the original garage accordingly, leaving the seals unbroken.

 

Peter

[Peter Douglas Winn]

Peter

For legal reasons I cannot go into details at the moment. One day the story will come out. It is nothing to do with the garage. I have no complaint with tte garage till now. The garage has been in the business with triumphs for 40 years. The owner was well known in the Triumph racing scene. They are doing these conversions many times a year. This is why at the moment I do not doubt the Garage. They do not do things without a reason even if I do not understand. They are a cross between Revington and TR Bitz. When you go there there are always 10 or more TRs being done up. On top MGs, BMW Csi, Roadsters, They have a team that have been together for many years and a work force of abouit 10 to 15 persons.

 

Peter sorry I am an Injection man, what is a UEGO? Unwanted Exhaust Gas Observer perhaps.

 

I thought untill I have talked to the garage the ony change I could safely make (reversable) was to advance the ignition to just before pinking..

[Peter Cobbold]

UEGO: Universal Exhuast Gas Oxygen. Its a wideband sensor that measures AFR from 17 to 10 .

Lambda can only measure 1 7 to 14.7, not rich mixtures, likewise CO.

UEGO kits can be bought for DIY use at ca £150.

UEGO is really the only way to accurately assess rich mixtures.

 

Advancing the spark wont correct cunsumption caused by a over rich mixture.

But if the spark timng is really badly out, then consumption can go silly. I assume the static and centrifugal have been checked?

 

Peter

Edited August 14, 2017 by Peter Cobbold