Slow running speed during warmup.

[mleadbeater]

 

Hi

My ‘6 throttle mechanism has been improved by fitting a system as often used with Weber carbs, incorporating machined aluminium arms, mounting on a common shaft with Rose type bearings, see photo below. This enables easy and precise setting up of the 3 butterflies, and I have achieved a smooth tick over of around 850rpm, when warm.

However, there is no provision for setting a fast idle speed during warmup, as the original cam for this is no longer present. The bifrucated cable for this function is still fitted, but only operates the enrichement lever on the PI regulator.

So, I was thinking, as you do, of possible ways to provide a fast idle facility.  My idea is to install a 12 volt solenoid air valve in the hose connected to the slow running needle needle valve fitted to the front throttle body, which, at present is fully screwed shut.

A simple switch on the dash could operate this solenoid valve, normally closed, with the needle valve set to a fast idle, say 1100rpm, to be switched off when the engine is sufficiently warm, in conjunction with the enrichment lever returned to the normal running position.

Has anyone done this modification?, or can you see any problems?

Cheers

Mike

 

Edited October 30, 2023 by mleadbeater
error

[Waldi]

Hi Mike,
I use the standard design linkage on my CP TB’s with (blue) PU bushes and the 3 rose joint links. It works ok, and I do not need an additional solenoid operated idle air valve (which would be a hand on/off operation, unlike with the EFI-conversions.

Can’t you just add the cam on the new linkage?

Waldi

[TR NIALL]

I find just using the enrichment lever on the MU tends to foul the Plugs all to easy there is also a better Choke/Enrichment  mechanism available from one of the upgrade suppliers that only uses one Cable instead of the split cable idea.

Fred Millturn is the man to contact.

Edited October 30, 2023 by TR NIALL

[mleadbeater]

Waldi, Niall, thanks for the replies 

to add a cam would mean making it from scratch, which doesn’t look easy. My linkage is totally different to the standard one.

I wouldn’t mind a switch , and, if successful, could be automatic with a thermostatic switch, akin to the “Otter” switch as used on Jags of the 60’s. What I am proposing is dead simple.

This would also make the enrichment system independent from the fast running, allowing the cable to be pushed in soon after the engine starts.

 

By the way, I can’t believe that a new double cable is £90 from our favourite parts supplier!

Cheers

Mike

 

Edited October 30, 2023 by mleadbeater
edit

[Spit_2.5PI]

Hi Mike. Yes, I do something like you're describing. My Prestige throttle bodies have "bedded in" such that I now use the idle adjuster on the front body to set the tick-over. However, for various reasons I haven't fitted the Prestige fast idle and I get around this with a hose take-off on the rear throttle body. I currently have a 1/4" hose from this to a ball valve under the dash. Fully open to start (plus a bit of throttle when cold) then it idles without throttle and I progressively close the valve as the engine warms. Of course, I hope one day to have a servo-controlled fast-idle valve run by some electronics - one day - when I get some time. Meanwhile I just play with the valve! It works fine.

Cheers, Richard

PS: Perhaps a slightly larger tube than 1/4" may be required for starting without any throttle. Some experimentation would be required.

PPS: I'm forgetting you've probably got a brake servo on the rear throttle body. No servo on a Spitfire.

Edited October 30, 2023 by Spit_2.5PI

[michaelfinnis]

The solenoid would only give one fixed fast idle speed, where as the original cam gives a variable setting depending on how far out the cold start cable is pulled.

You say you have the slow running air valve screwed fully shut. If the throttles are set  up as intended by Triumph, the throttle butterflies are closed at idle (or with a fag papers clearance if a CR car) and the engine would stall if the air valve was fully closed.

[mleadbeater]

Thanks for your response, food for thought ( Im laid up in bed at present, getting over a heavy cold, so my rambling mind has been considering many possible mods )

Interesting , Richard, a valve under the dash, a simple solution. I was considering a cable to manually adjust the idle valve, hmmm.

Michael, yes, the solenoid valve would only have one idle setting, and, as my car had done well over 100k, the bodies and butterflies are probably well worn, Ive managed, as Roger states, to balance them with a flow mater, to achieve a steady idle.

A pal of mine has bored out the SU’s on his DB4 , and made oversized butterflies, he is a perfectionist, shows what can be done.

My other  gripe with the ‘6 is its lack of momentary enrichment on opening the throttle, it tends to bog if i don’t increase the revs and slip the clutch, any novel solutions to this ?

cheers, back to a snooze,

Mike.

ps Richard, if you want a servo for your ‘spit, I have nearly new one , only briefly used on my TD, which I decided was unnecessary, let me know.

[elclem1]

Triple webers - I use the accelerator pedal to get it warm then after that its fine. 

[michaelfinnis]

2 hours ago, mleadbeater said:

 

 

 

My other  gripe with the ‘6 is its lack of momentary enrichment on opening the throttle, it tends to bog if i don’t increase the revs and slip the clutch, any novel solutions to this ?

 

I know there is no accelerator pump or equivalent, but surely something is wrong, I've never experienced this problem with the TR. Mixture too weak maybe?

[stuart]

55 minutes ago, michaelfinnis said:

I know there is no accelerator pump or equivalent, but surely something is wrong, I've never experienced this problem with the TR. Mixture too weak maybe?

Correct that’s why the PI always runs slightly rich to cope without the enrichment facility when you boot it 

Stuart

[TR NIALL]

Mike I’ve flipped your photo around as I was struggling to make out what you’ve done have you disconnected the Balance Pipes at the rear of the Throttle Bodies and closed off the Air Bleed Screw altogether if so that is part of your problem.

Edited October 31, 2023 by TR NIALL

[mleadbeater]

Thanks for flipping the photo, I tried inverting a duplicate in my photo file, then inserting in the post, but it wasn’t having it. How did you do this?

The car is as I bought it, as you say the balance pipes nearest the head are all blocked off , I was told that earlier cars didn’t have them.

I could refit these, would this be worthwhile?

I’ll also try enriching the mixture, is this the same as moving the enriching lever?, ie short term for a test?

Tests I did with my colortune showed a perfect blue flame.

Thanks to all , will get back on it when i’ve recovered.

Cheers

Mike

Edited October 31, 2023 by mleadbeater

[TR NIALL]

2 minutes ago, mleadbeater said:

Thanks for flipping the photo, I tried inverting a duplicate in my photo file, then inserting in the post, but it wasn’t having it. How did you do this?

The car is as I bought it, as you say the balance pipes nearest the head are all blocked off , I was told that earlier cars didn’t have them.

I could refit these, would this be worthwhile?

I’ll also try enriching the mixture, is this the same as moving the enriching lever?, ie short term fir a test?

Tests I did with my colortune showed a perfect blue flame.

Thanks to all , will get back on it when i’ve recovered.

Cheers

Mike

I flip the photo on my iPad and re post it.

As far as I’m aware all TR5s and 6s had them and yes I’d replace them and control your Tickover with the Bleed Screw on the front Throttle Body.

I wouldn’t try enriching the mixture leave that for the moment the enrichment lever only operates on start up in conjunction with the Choke when alls properly set up.

Im not sure a Colour Tune would benefit you at the early stages of Set Up but an Air Balancer for the Throttle Bodies is a must if you want to achieve a good set up.

[mleadbeater]

 Niall

I see from your profile you are rapidly approaching your 70th, as am I, the complexities of computer software is becoming an ever-increasing puzzle to me, fortunately I have a son who is very computer-savvy and bails me out, often with a look of incredulity at my ineptitude.

So, to enrich the mixture, I should adjust what?

I am a big fan of colortunes, I would expect to see immediate changes to the flame colour as I tweek the mixture, as I have found over many years of use on carburettored cars. On the SU for example, you can observe the correct functioning of the dashpot enrichment, as you blip the throttle the flame will momentarily burn yellow, ie rich, then return to a normal state colour of bright blue.

However, this car is my first dabble with the early Lucas PI system, so i’m still well down the learning curve, all part of the fun of ownership.

Are you suggesting the colortune is not useful on the PI system, am I missing something?

I bought an air balancer, and did my best to balance them, but think wear on the butterflies and spindles makes this difficult/impossible. I could spend lots of time to sort, but I don’t really want to goto the the probably considerable expense of doing so. My car is a “ mid range” one pricewise, generally in good condition both mechanically and bodily , with plenty of scope to improve without major expense ( hopefully), as someone remarked at a recent local rally its a good car for “ragging around “ , without the concerns over spoiling a concours car. Of the many classics i’ve, including a 911, XK 150 , Aston DBS, TD, owned over 50+ years, the ‘6 is probably my favourite drive so far, with a TR2 being a close second.

I’ve just fitted a stronger return spring, which lowered the idle by around 150rpm, which is steady at around 850, suggesting wear.

yet to see how the car  drives but I suspect the bogging issue to worsen at this lower idle speed.

Thanks again, I’m enjoying the brilliant feedback from likeminded enthusiasts as ever with this forum, sorry to be rambling on a bit, its helping my convalesce .

Mike

[Spit_2.5PI]

20 hours ago, mleadbeater said:

ps Richard, if you want a servo for your ‘spit, I have nearly new one , only briefly used on my TD, which I decided was unnecessary, let me know.

Thanks Mike, but the Spitfire is so light it doesn't need a servo.

Richard

[michaelfinnis]

10 hours ago, TR NIALL said:

 

As far as I’m aware all TR5s and 6s had them and yes I’d replace them and control your Tickover with the Bleed Screw on the front Throttle Body.

 

TR5s and CP TR6s only had the balance pipes furthest from the head, with the air bleed screw in line with them. The CR cars had the two sets of balance pipes with the air bleed screw in line with the pipes closest to the head, I'm not sure why the change was made.

Mike, with the extra set of balance pipes blanked off as you have them the air bleed screw is not going to work properly unless it is moved to the CP position. As TR NIALL says, could well be the cause of your problem.

Also, I would think that having the air bleed screwed shut and the butterflies slightly open to get the engine to idle would affect the manifold vacuum, which is what ultimately controls the MU. 

Adjusting the mixture involves removing the black cap off the MU and moving one of the adjusting nuts, but you need to be sure of what you are doing. They are meant to be set up on a test rig, but I have read articles on doing it on the car. No reason why not in principle, but I've never tried it.The original Lucas manuals can be found online, and there have been articles in these forums.

(also) Mike.

[TR NIALL]

7 hours ago, michaelfinnis said:

TR5s and CP TR6s only had the balance pipes furthest from the head, with the air bleed screw in line with them. The CR cars had the two sets of balance pipes with the air bleed screw in line with the pipes closest to the head, I'm not sure why the change was made.

Mike, with the extra set of balance pipes blanked off as you have them the air bleed screw is not going to work properly unless it is moved to the CP position. As TR NIALL says, could well be the cause of your problem.

Also, I would think that having the air bleed screwed shut and the butterflies slightly open to get the engine to idle would affect the manifold vacuum, which is what ultimately controls the MU. 

Adjusting the mixture involves removing the black cap off the MU and moving one of the adjusting nuts, but you need to be sure of what you are doing. They are meant to be set up on a test rig, but I have read articles on doing it on the car. No reason why not in principle, but I've never tried it.The original Lucas manuals can be found online, and there have been articles in these forums.

(also) Mike.

Mike I’m in work at the moment with limited Wi-Fi so it’s as Mike explains above all the Fuel Adjustment is done within the MU and you would need fair knowledge to set one up right so I’d stick to sorting your Throttle Bodies first and get them set up as they should be.

Theres Lucas Training Notes floating around on the WWW if you can get a hold of those from somewhere you’ll gain a lot more info on the whole Injection Systen.

[Mike C]

The Lucas PI manuals are here:

http://vitessesteve.co.uk/LucasStuff/Lucas_Petrol_Injection_Manuals.htm

To set up the PI properly you really need a calibration rig plus knowledge of your engine capacity and camshaft, if not standard.

[Steve-B]

Apologies for my possibly weird question but don’t all TR6s come with a Choke knob on the dash to alleviate/ assist starting? I tend to use my Choke(which goes to the MU) for 10-15 seconds after a cold start, or when the cars been off for several weeks.

(Asking as I never seem not to be absolutely amazed with the collective knowledge and helpfulness of the members of this forum!)

Edited November 1, 2023 by Steve-B

[Mk2 Chopper]

Yes they all do. The op has the cable/ knob but not the cam on the throttle linkage. 

Gareth

[Steve-B]

46 minutes ago, Mk2 Chopper said:

Yes they all do. The op has the cable/ knob but not the cam on the throttle linkage. 

Gareth

Got it, thanks Gareth 

[mleadbeater]

thanks guys for your replies, to clarify any confusion 

I post  below a photo (hopefully right way up ) of the full induction system of my ‘6, it seems I have  a CR set of bodies, with blocked off inner balance tubes, and adapted Weber-style linkage, all carried out by a previous owner.

I still have the redundant fast idle cable, and just use the enrichement device on the PI regulator, manually blipping  the throttle during warm up, via the other part of the “choke” cable knob ( which is misleading as, to me , it aint a choke at all).

My aim is to set the (now closed ) idle jet on the front end of the outer balance to give a fast idle, say 1100 rpm, and to fit a low cost air valve in the hose to the jet from the inlet plenum, with a switch to select fast idle when warming up.

I already have a dash mounted fuel pump switch, which I consider a very worthwhile mod for both security and safety, so I could replace this with a two pole double throw switch to control both pump and fast idle valve.

I intend to try this out in the near future, and will report on progress, and will continue to try to understand the mysteries of the infamous PI system, surely it can’t be that complicated? or is there a “vodoo” element involved?

All part of the fun of ownership of a flawed but great car, as are most cars of this era.

Cheers

Mike

ps, sorry, but yet again my photo appears inverted, bl***y computers.

Edited November 1, 2023 by mleadbeater
photo

[TR NIALL]

27 minutes ago, mleadbeater said:

thanks guys for your replies, to clarify any confusion 

I post  below a photo (hopefully right way up ) of the full induction system of my ‘6, it seems I have  a CR set of bodies, with blocked off inner balance tubes, and adapted Weber-style linkage, all carried out by a previous owner.

I still have the redundant fast idle cable, and just use the enrichement device on the PI regulator, manually blipping  the throttle during warm up, via the other part of the “choke” cable knob ( which is misleading as, to me , it aint a choke at all).

My aim is to set the (now closed ) idle jet on the front end of the outer balance to give a fast idle, say 1100 rpm, and to fit a low cost air valve in the hose to the jet from the inlet plenum, with a switch to select fast idle when warming up.

I already have a dash mounted fuel pump switch, which I consider a very worthwhile mod for both security and safety, so I could replace this with a two pole double throw switch to control both pump and fast idle valve.

I intend to try this out in the near future, and will report on progress, and will continue to try to understand the mysteries of the infamous PI system, surely it can’t be that complicated? or is there a “vodoo” element involved?

All part of the fun of ownership of a flawed but great car, as are most cars of this era.

Cheers

Mike

ps, sorry, but yet again my photo appears inverted, bl***y computers.

 

 

Edited November 1, 2023 by TR NIALL

[mleadbeater]

thanks again, Niall, 

 

[TR NIALL]

Hi Mike yes CR Bodies but I’m still trying to understand why the back pipes were blanked off maybe to turn them into CP type ones.

Its said the CP type are easier to adjust on the connecting rods but either way yours seem to be the rose jointed type so adjustment should be handier.

if it was me that were trying to achieve what would be a better driving car I would slacken off those rods until the Butterflies were completely closed and adjust the Air Bleed Screw to allow some air and the car should start further adjustment of the Rods will then allow the Butterflies to open evenly with the throttle cable.

Im not very good at writing to explain what I’m thinking but I’m sure you get the idea,Cheers.