Balancing Throttle Bodies

[Ginger pig]

All,

Still suffering with this issues with the engine stalling when I go to accelerate. Several people have had a look at it with no luck.

I still think that the throttle bodies (butterflies) may have something to do with it.

I know that you should not dismantle the throttle bodies/balancing connector and idle screw but that horse bolted many years ago when I was young, inexperienced and a twat!

I bought myself a vacuum gauge that you can use on the plenum back plate (has a tapered rubber surround).

On idle I get a very very low reading on the gauge (almost unregistered).

When I pick the revs up by depressing the accelerator I do get quite a strong reading of around 5 - 5 1/2 across all four inlets (not totally level but hopefully a goo starting point.

I have read the process in the manual about altering the idle screw; but the manual assumes that it has been altered; not completely dismantled and therefore starting from scratch.

Could I please confirm the following:

Should both pairs of throttle bodies be reading the same vacuum reading or are one pair supposed to be slightly more open/closed?

What should the vacuum reading be on a warm engine on idle (I was positive that I should have had a decent reading when it was idling as I have seen some videos on youtube that would suggest that I should be getting at least 4kg's of air per hour). The vacuum is almost non existent on idle?

When adjusting the idle screw; will it be best to have the screw fully turned out, so that the butterflies are fully closed and then turn the screw inwards to start to open the butterflies (1/8 of a turn at a time according to the process) or have the screw fully in (butterflies more open) and the progressively close them?

Sorry if these are stupid questions but the project has been stalling (excuse the pun) on this problem for over a year now.

Thanks in advance

Mark

 

 

[eeyoreish]

Have you refurbed your carbs with new seals and o rings etc? First thing to do if you haven't.

Also check that your spindle bearings are free and that your butterflies are opening and closing at exactly the same time across both carbs. You can see this by removing the progression hole caps and looking down through the progression drilling holes to see where the butterflies are in each carb as you open them.

Also check for air leaks, vac pipes and carb to inlet o rings are all OK.

I've had an off idle stumble on my N/A since I've owned it and have gradually improved it by refurbing the carbs with genuine Dellorto kits and then balancing with a Carbtune 4 barrel manometer tapped into the ports on the carb bodies.

I've read that the idle jets in the Dellortos are sized to meet emissions regs and ideally could be a size larger. Hence tuning them seems to be a bit of a knife edge - slightly off perfect tune and you'll feel it!

The set up and balancing procedure in the Lotus manual is actually pretty easy to follow so that's mostly what I've used. The Des Hamill book is worth having if you need to work more 'in depth' but for basic tuning it's more info than you really need.

I still need to set the mixtures on mine (currently all set to standard 6.5 turns from closed) with the Colortune.

By cleaning, refurbing and balancing my carbs I've moved my car from pretty annoying/undriveable to a very subtle stumble that is hardly noticeable. I'm hoping that setting the mixtures and a final air balance will sort that.

 

 

[Winter]

Another possibility: balance the carbs at about 3,000 engine rpm and then for idle, use a Gunson colourtune.  Take care with the metallic windowed part that screws into the spark plug thread.  It gets hot very quickly and it is all too easy to get burnt fingers handling it.

[DanR]

If you can tap into the manifold ports between the head and throttle plates make yourself one of these...

When there is no suction on the fluid in either bottle the throttles are synchronized.

[jonwat]

4 hours ago, eeyoreish said:

Have you refurbed your carbs with new seals and o rings etc? First thing to do if you haven't.

What's all this crap about balancing carbs???

It's a fuel injected SE 

[Ginger pig]

All,

Thank you for your comments but John is right; my car is an Esprit SE (fuel injected).

I still appreciate that you took the time to write though!

Mark

[eeyoreish]

Oh well, the perils of reading TLF on a mobile..! Couldn't see your vehicle.

[CHANGES]

Hi Neil,

Just a few points.  when you fully stripped them did you make sure the BAV  was in the correct way round, they have a slight chamfer on them .  This allows the BAV discs to sit correct in the TB's  and also influences the air flow around them.  Otherwise there is not much you can get wrong rebuilding them..                                      Another small point is the balance screws for each TB. They are factory set and sealed..  The problem is they can get clocked up with crap or work loose over the years.   Remove the sealed cap and then the screw,  clean the tiny air bleed gallery and screw then replace.   This gallery acts as a bypass or bleed around each BAV ,  Use these to balance the BAV's in each TB then balance the TB's to each other. The more accurate you do this the smoother the results will be.. NB .. Always have these bleed screws to a minimum.

Hope this helps.      

[Barrykearley]

Chap - have you had this car on freescan?

the tps - that needs to be set right - if it's not it could well be causing the issues your having.?

my old fave - the aic valve ( bastard hateful thing ) is that working correctly?

Don't start twiddling things til you've done the simple things first - these are the first ones up in the fault finding charts from lotus

and is the fuel a year old? If so use that on the bonfire and go and grab some fresh 

 

[jonwat]

9 hours ago, eeyoreish said:

Oh well, the perils of reading TLF on a mobile..! Couldn't see your vehicle.

And the perils of people asking for assistance without bothering to state model, year & mods.

To answer the original question " Should both pairs of throttle bodies be reading the same vacuum reading or are one pair supposed to be slightly more open/closed? "

They should ALL be the same through the full range of throttle opening.

[Ginger pig]

All,

 

Thank you for your responses thus far.

Dave,

That's some excellent advice!

When I say; stripped............. that is in the looses sense, I left the butterflies alone but just separated the pair from each other, so did not touch the BAV's.

John,

The model and year were in my account details but I do generally remember to add to the title but on this occasion forgot.

All,

Should I be getting a vacuum reading on idle as currently get pretty much nothing?

Thanks again

Mark

[sailorbob]

The MAP should be around 0.65 - 0.70 bar at warm idle.

[Ginger pig]

All,

This is the tool that I used to measure the vacuum on each inlet:

Like I said; this hardly registers any vacuum on each inlet when they are balanced currently.

The furthest forward pair are the static ones with the balancing adjustment seeming to be on the rear most pair.

When I 'unbalance the rear pair; I can get 5kg per hour on the rear ones but the forward ones do not register ever.

Does that mean that I should adjust the idle screw first so that I get the required vacuum on the static pair before then adjusting the rear pair to match?

Hope this makes sense............. Some of the terminology escapes me!

Thanks

Mark

 

[ragingfool35]

i tried to do same thing using a similar tool.  however, the IAC porting is connected to a common rail for the cylinders i think, so that would foul the readings when measuring this way.  attempting to measure with engine running, the IAC would have to be disconnected to keep from generating erroneous variations.  i think the only way to adjust them is to remove intake, plug the ports (if connected at intake) and use a flow bench or similar to produce constant airflow, then use your anemometer to adjust.  maybe Travis or Dave can confirm or deny that.  the adjustments are only for idle, though getting the linkage screw too far off will have an affect above idle as well.

i haven't read previous topic to know if you have confirmed, but as many similar topics indicate, stalling while accelerating from idle is often due to high IAC counts and/or improper TPS idle volts (or malfunction).  perhaps you have already checked? 

[Barrykearley]

Mark

have you been working through the fuel injection manual? Them there twiddly bits are really far down on the list to adjust??

heres an extract section that may help - as Chris mentions - the aic will play havoc with any measurements if it's still connected

 

 

[Chillidoggy]

On ‎22‎/‎12‎/‎2015 at 07:57, Barrykearley said:

Chap - have you had this car on freescan?

the tps - that needs to be set right - if it's not it could well be causing the issues your having.?

my old fave - the aic valve ( bastard hateful thing ) is that working correctly?

Don't start twiddling things til you've done the simple things first - these are the first ones up in the fault finding charts from lotus

and is the fuel a year old? If so use that on the bonfire and go and grab some fresh 

 

 

Can I just remind everyone to stand well clear of any bonfires at Barry's gaff?

[ramjet]

Mark, I haven't done this as I have never need to on the esprit. However, I did have to balance the slides in my Dell'ortos on my Ducati. I did it using a piece of copper wire under each slide and an assistant to gently twist the throttle. I adjusted each until they both released the wire at the same time. Yes, I know you only have two hands and there are four butterflies. Start with 1 and 2, then do 1 and 3, then do 1 and 4. That way they are all referenced to number 1. You can always check 2 against 3 etc if you wish.

This might be worth a shot if the vacuum doover isn't working that well.

Worked every time on the Ducati without a problem.

[CHANGES]

On 22/12/2015 at 09:33, Ginger pig said:

When I say; stripped............. that is in the looses sense, I left the butterflies alone but just separated the pair from each other, so did not touch the BAV's.

Ahh  I see , just definition of terminology..  bit like half dressed sex.. you don't get to see the full picture.  

In that case, as others have said i would be looking towards additional factors that could influence... AIC and TPS would be favorite.... 

My base tuning set ups are all done using similar air flow tool as mark illustrated without issue..  I first balance 1&2 with screws  illustrated pre post , then 3&4.  At this point the two banks usually have different reading but that is addressed next,  balance 1&2 to 3&4.. Use the throttle stop screw to keep the rpm at around 1500 while doing this... when fully balanced retract the stop screw to lay position and let the AIC take over..  If the TPS is set and operating in scale,  the injectors are all functioning correctly with appropriate fuel pressure and the Lamba sensor and AIC working , Then you should be ticking over smooth with good throttle response.   Nothing is disconnected or blanked out during this operation.   If you still have problems then you need to study the ECU data... 

The process Michael mentioned will only work using combinations of   2&3.. 1&4..2&4.or 1&3  due to 1&2 and 3&4 being on fixed spindles. which is why the bleed screw are there as illustrated in pre post..  The only way to do these is with flow gauge.. 

Hope this helps..    

            

[jonwat]

2 hours ago, CHANGES said:

The only way to do these is with flow gauge..             

Dave,

Is there no way to connect up a manometer as you would with Dell'ortos?

[CHANGES]

Yes.   In that statement i was making reference to Michael comments where you can only balance between 1&2  with air flow gauge due to fixed spindle , same with 3&4. 

Any suitable air flow measuring device will work to balance induction flow volume. I hate to say it but some people seem to over complicate a simple procedure that takes 10 min tops..     

[Ginger pig]

Thanks all!

Dave,

Is what you are pointing to with the red arrows; the caps that cover the screws?

How do I remove these caps?

What does BAV stand for (is this the butterfly within a throttle body)?

What is the best way to measure fuel pressure and could poor fuel pressure create these symptoms?

I have measured the TPS and IAC using FreeScan and all of the measurements were in spec.

Sorry about the novice questions but just wanted to clarify!

Kind regards

Mark

[Barrykearley]

Is the aic actually working though? Is it the correct one ? Is there any wobble in the pintle ? Is the o ring nice?  Hateful bastard things.........

you need to work through the fault finding guides - and leave them screws til very last. Is the o2 sensor behaving ?

[CHANGES]

8 hours ago, Ginger pig said:

Is what you are pointing to with the red arrows; the caps that cover the screws?

How do I remove these caps?

What does BAV stand for (is this the butterfly within a throttle body)?

What is the best way to measure fuel pressure and could poor fuel pressure create these symptoms?

Sorry about the novice questions but just wanted to clarify!

 

1/  you need to knock the cap out with small elec type screw driver..  

2/ Tap on one side and they will flip up. you can then hook them out exposing the screw.  'Only play with these if the balance on each bank is out'

3/  Yes... ''butterfly air valve''    

4/ On the back of the fuel rail there is a valve, fit suitable gauge and read off..  Fuel pressure needs to be correct for the injectors to perform to spec..  All part of the balancing act.. 

5/ If unsure always best to ask, look at it as research   measure twice cut once theory...  

[jonwat]

17 hours ago, CHANGES said:

Any suitable air flow measuring device will work to balance induction flow volume.

So, where does the manometer connect into, could you please put another arrow on your picture?

Many thanks.

[Ginger pig]

All,

Once again; thank you for your responses!

Barry,

Great call on the IAC; I will remove and inspect.

Dave,

You appear to be the font of all knowledge regarding the Esprit. I really appreciate the time you have taken to describe in detail my next steps.

I will put all of this new found knowledge to use in the next few days when I work on the car. It makes a massive difference to the enjoyment factor when you know what your doing.......... in my case; a rare event!

Kind regards

Mark