free hit
counters
S4 timing - Engine/Ancilliaries - The Lotus Forums #ForTheOwners Jump to content


S4 timing


stevefh

Recommended Posts

Hi all,on my 1993.5 esprit S4 I set up the timing with flywheel TDC set up exactly.The timing dots are not central on the pulley teeth but that pair of teeth are reasonably aligned.However,when the engine is run the exhaust manifold is glowing red hot,so I assume i am one tooth out.Are the exhaust valves remaining partly open allowing the fuel to burn in the exhaust manifold?Looking from the front of the engine do I take the belt off the exhaust pulley and move the pulley one tooth CLOCKWISE retaining the position of the inlet pulley to cure this?Is there another reason for this?Thanks for any help.

 

 

Link to comment
Share on other sites


Upgrade today to remove Google ads and support TLF.

I assume you mean the manifold is glowing red during a normal drive, not after a thrashing which is normal? 

What have you done to the engine, just changed the belt or what????

A little more info would be useful. :ermm:

Cheers,

John W

http://jonwatkins.co.uk

Link to comment
Share on other sites

Once an engine has been worked on post factory it is very unlikely the cam timing dots will line up perfect. What you have to do is find the best compromise, carefully assessing how you want your engine to perform.. Your standard 100' / 110' timing would always be best edging toward the 104' 104'  which is the preferential timing for those looking for performance.  This will be advancing the cam timing on both cams . Anywhere in between the two will give you an acceptable timing set up . 

20 hours ago, stevefh said:

so I assume i am one tooth out.

Never assume always be sure...   I see so many with timing a tooth out because people never check carefully enough or presume it was correct form previous owner/belt fitter.. 

Most mistakes come from initial set up with slack in the belt between the exhaust pulley and the crank . Even when you are doing your check , have you made sure tension is on that area of the belt.  So many people think when they have just gone past TDC they can knock it back a bit.. That is so wrong and just shifts tension point on the belt and alters the timing readings.  Always bring round to TDC in running direction. 

You must also allow for TDC errors on the marks and the angle you are reading from.  So best to find true TDC with DTI to be sure..   

Its not  totally relevant but the content should show you what you are looking for .       

 

Link to comment
Share on other sites

Thanks for replies so far. I removed the belt from the pulleys to do the valve gaps and give me practise at doing the timing before changing the cam belt (2 years old)this summer.The exhaust manifold is getting red hot when idling ,so is it that the exhaust valves are not closing early enough in the cycle and is my solution above of moving exhaust pulley one tooth clockwise ,looking from the front,correct.Dave ,thanks for the detail, I will use it this summer,but for now I just want her to run with no red hot manifold .

Link to comment
Share on other sites

17 minutes ago, stevefh said:

so is it that the exhaust valves are not closing early enough in the cycle and is my solution above of moving exhaust pulley one tooth clockwise ,looking from the front,correct.

Not necessarily . You need to do the basic checks as stated in previous post and find best/ closest to correct alignment..      You seem to have made your mind up you need to do this and want conformation from people who have not inspected you set up..   Its always best in situations like this  to go back to basics and set up again ... Align your cams with the dots , lock them off, set crank at TDC and fit belt with tension as previously stated. If half a tooth out move to the 104 direction as indicated above..  This is your best option and will isolate that area.  .. If manifold still glowing at tick over you will need to look deeper.. 

 

  • Love 1
Link to comment
Share on other sites

Thanks again Dave,please explain how I know ,from the front,which is the”104 direction”clockwise or anti-clockwise and do I just move the exhaust pulley relative to the cam belt or am I misunderstanding. I have yet to change anything.The belt is still under tension with TDC set,bearing in mind your comment on TDC, and dots slightly out ,as per hot running.

Link to comment
Share on other sites

Ok, The details are in the vernier post,  but i will try to explain.. Firstly can I say it is easier to do than explain..   To do a 104 timing you need either a set of 104 pulley's or vernier pulley's ... But if you are looking for the best misalignment using std pulley's you should move towards the 104...   So  your exhaust cam normally should be fully open at 100' BTDC which is where your blue dot should line up with the red as per very first pic in the thread.  To get to this point the crank will have already passed 104' BTDC which means if the blue dot is passed the line up point (above the line line pic or further around clockwise when looking from in front of the donkey) then your error is towards 104'  which is the better side to be ..   but without actually measuring it , you will be trusting to guess work. As a rough guide it should be within 1/2 a tooth.

hope that helps, I don't know how i can explain any further.. 

 Please note this is only a compromise to facilitate changes in the engines set up dimension due to head gasket and machining that may have been done..    You should study and fully understand all the parameters before changing your cam timing . 

Link to comment
Share on other sites

  • Gold FFM

You are seriously overthinking this. The human eye is a perfectly sufficient gizmo for said measurement.

  • Like 2

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

Link to comment
Share on other sites

Hi all,the reason I ask this as I am doing the timing again and I am getting the same setting as before which gave me a glowing red hot manifold! I am using a mirror and a ruler.The gap between the pairs of teeth on either side of the dotted pair of teeth are not the same and I think they should be .Unless I get some help on this I will try to get the gaps the same with the minimum gap possible on the dotted pair of teeth.

Link to comment
Share on other sites

  • Gold FFM
31 minutes ago, stevefh said:

The gap between the pairs of teeth on either side of the dotted pair of teeth are not the same and I think they should be .Unless I get some help on this I will try to get the gaps the same with the minimum gap possible on the dotted pair of teeth.

I don't fully understand what you're saying here.  But, put simply, if you're within a tooth or so (or even 2) then it ain't that causing your glowing manifold.

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

Link to comment
Share on other sites

Thanks Barry,did the set up look correct when it glowed red hot as mine does and did you turn the exhaust pulley one tooth clockwise when looking from the front,to cure it?My thinking said this and Dave agreed,but when I set it up it was a long way out so I stopped.

Link to comment
Share on other sites

  • Gold FFM

Forget the glowing manifold - all that shows is that you are driving it properly. The brighter and more orange it is the better you are driving it 👍

some folks historically played around with different pulleys and being one tooth out to obtain different timings. I can’t remember all the numbers but there’s lots of different colour dots available - and some can be close to others if fitted a tooth out.

Only here once

Link to comment
Share on other sites

17 hours ago, stevefh said:

Thanks Barry,did the set up look correct when it glowed red hot as mine does and did you turn the exhaust pulley one tooth clockwise when looking from the front,to cure it?My thinking said this and Dave agreed,but when I set it up it was a long way out so I stopped.

I did not agree with your thought , I just stated that clockwise was the safe direction moving from 100' toward 104' .. In other words if the blue dot was slightly above the line it would be in the better direction..    But moving 1 tooth when it is close is so wrong..   .. The cam pulley has 40 teeth that is 9' per tooth.. The crank has 20, so 18' per tooth ..  As we are measuring crank angle ,  from 100' to 104' = 4'.  divide by two allowing for crank/ cam pulley ratio which = 2'  .. This is only 22% of one tooth for movement to go from 100' to 104 cam setting ..  This is not a lot but cam timing is about small degrees of movement.   There should be no reason why you can not get the two dots on the cam wheels close, unless the engine has had major head skimming done ie .040 to .050 and the thin head gasket that Gary kemp supplies..    As Sparky said you are seriously overthinking this..    With the std cam wheels you have one position which will be the best it can be..  People do get them one tooth out and run them like that ..   What we a saying is get the tension correct in the area's as stated at TDC and if the dots are lined up within 1/2 a tooth then that is just how it is ...., If you want to get it spot on then fit verniers..    Sorry if this sounds abrupt but i don't know how i can say it any clearer..   

  • Like 2
Link to comment
Share on other sites

On 10/01/2019 at 10:54, stevefh said:

The exhaust manifold is getting red hot when idling 

With my S4s the manifold would be glowing after a good run but after a few minutes idling, to let the turbo cool, the glowing would have faded away.

Just saying.

Cheers,

John W

http://jonwatkins.co.uk

Link to comment
Share on other sites

  • Gold FFM

Also have you checked the exhaust valve clearances, too tight would allow ignition to continue into the manifold. 

A compression check will ascertain if valves are closing properly too.

Link to comment
Share on other sites

Hi all, keep your thoughts coming. It is the same plugs as when it was running fine . I have just done the valve gaps but i am sure all gaps were set in spec.I considered if a broken valve spring had caused this overheating of the exhaust manifold but decided one spring problem would not cause it,and unless it broke when I was doing the gaps ,it was running fine before. I have thought of a gizmo to fix the centre line between the cam pulleys and hope when I use it, it gives me a slight difference in set up of timing spots from my current problem setting. I did the gaps because they were noisy. I have owned this S4 since it was 18 months old and the head has not been skimmed.

Edited by stevefh
More info
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...