Esprit Turbo project car - part3 - the further continuation

[drdoom]

There is a great deal of information to be found on the forum, "SpeedTech", hosted in America. A very recent discussion was graced with what I find to be the most comprehensive summary yet offered in any such thread. Will attach a link in the next submission.

From all I've read to date I'd go with Valvoline VRP synthetic 20W-50.

Cheers 

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=62098

Review comments from member RDY4WAR in particular.

[Lotusfab]

This is interesting

 

[Andyww]

3 hours ago, drdoom said:

There is a great deal of information to be found on the forum, "SpeedTech", hosted in America.

The choice of oil is missing a very good option in the USA though, Mobil1 10w-60. This was discontinued in the USA but still available in the UK. Note the Mobil advert above (video states its a paid-for promotion) does not mention this as it is from the USA.

[canamfan]

This is one slippery slope topic, no pun intended. I thought about Valvoline VR1, “Street” version & NOT the “Racing/not for street use” type, for the latter didn’t have the appropriate detergents to allow normal drain intervals. Used Street VR1 it in my 911sc, it was OK, using Brad Penn 20w50 partial syn. in her now, tends not to seep as much in the air cooled. I’m using Red Line 10w60 full synthetic in my ‘84 Turbo Esprit & really like it, easier starts & seems to ignore hot summer temperaments by keeping solid, steady temps with or without A/C on., plan on staying with it. Mind you, I’m sure price & availability is a factor for many, I’ve used Mobil 1 20w50 full syn. In the Esprit & think it’s not what it used to be, still very good but for the money wanted better hot temp. protection. Too much ZDDP & not enough appropriate detergents can be a bad thing too. I know the sweet spot for the 911 is around the 1200 to 1300 ppm & that’s what the Brad Penn delivers, but for the Esprit I’m still trying to figure what that # is, so in the meantime I’m doing shorter intervals for piece of mind. Trusted Charles Navarro’s experienced thoughts on the Porsche for his recommendations over many forums. Had Lucas 10w60 in Esprit before but added Red Line ZDDP supplement to bring it up to 1300+ ppm, some motocycle oils have slightly more ZDDP & lots of classic car flat tappet owners seek those out. I suppose it boils down to lots of things that an individual is just simply comfortable with be it price, availability, correct viscosity & application. Of course modern oils have had great improvements over the decades & suppose the basics like proper drain intervals shouldn’t be ignored because there’s no magical oil that stays clean without changing it. I apologize in advance for a lengthy post 😜

[Lotusfab]

Engine Tuning

I finally got to the bottom of the engine stumble at 2600 rpm. Its not the idle jet size or the pump jets, its the ignition timing! The distributor I have does not have the correct advance curve. The timing at 3500 rpm is correct, but this puts the idle timing off. Most people would probably think its fine. The solution is to replace the distributor with a solid state system and have a sensor ring welded to the crankshaft pulley or find a company that can set up the advance curve on the distributor, so its correct at idle and 3500 rpm.

I know upping the idle jet size has been touted on here as a solution for some years. I am now not convinced. I would exercise caution when increasing jet size make sure its not so rich you get unburnt fuel getting into the oil! The factory jetting is correct, so if the engine is stumbling with a 40 jet something else is wrong. ie. jet blocked with varnish, float height, pump jet setting, blocked carbs or ignition timing to name but a few! 

 

[910Esprit]

You may have a point Fabian, but let's explore this further....

Your car only has a 3 point advance curve specified.  Not exactly a complex map! 

• 1000rpm - 12  (no cetrifugal advance) - MIN
• 2000rpm - 20  (12 degrees static +8 degrees of centrifugal advance)
• 3000rpm - 28 (12 degrees static +16 degrees of centrifugal advance) - MAX

(there is no significance to 3500 other than to ensure max advance has been achieved during dynamic tyming)

So assuming your dizzy is a genuine Turbo version, in good condition and has been timed correctly, the idle position and the max advance are determined by the mechanical properties of the dizzy and the only real variable point on the advance curve is 20 degree of advance at 2000rpm.   You could easily test this with a timing light.   So I'm not convinced your theory is correct., as even if the timing was a few degrees off, either way, a stumble would not be the normal outcome.   (pinking or loss of power would be more typical)

I agree that 40 idle jets were correct at the time of manufacture, when the formulation of petrol was different, cylinder heads had not been skimmed and exhausts etc were Lotus originals etc.   However, most of these variables no longer apply.   But I do agree that just whacking in larger jets and hoping for the best is not a good idea... 

Contradicting my own post, maybe the original advance curve no longer suits modern fuels etc?

I suppose Rolling road testing with a mappable curve may be the best way to test this.   Be interesting to see how you get on.

[Andyww]

At the end of the day these setups will never be 100%. The weight and spring advance curve is never perfect and carb fuelling is never spot on.

The only way to get things absolutely right is to use EFI with ignition which has feedback from O2 and MAP and temp sensors etc. A no-feedback system on older cars will be susceptible to fuel differences, temperature changes etc.

BTW I am not advocating an EFI conversion! I did that on an Excel in the past and it was a money pit and never really delivered as expected. Its better to get things as good as possible with carbs even if not perfect IMHO.

[drdoom]

Andy, I'd be pleased to hear of your experience with the Excel EFI conversion so if it suits you perhaps a new thread over on "Engines . ."?

[Lex Templar]

Fabian my hand made Swaine Adeney Brigg Bond case arrived, for the important docs..🤣

[Lotusfab]

Well done Lex, excellent!

[Lotusfab]

Once Covid is over take a trip to Deezerland. Remember Miami motor museum had the Bond collection, well some of it has been moved to Orlando. Deezer Action Park, awesome cars in the collection. Heres a preview...

www.youtube.com/watch?v=dkxN39Vqd-Y&feature=

 

[Lex Templar]

Rog is holding a cigar outside the Miramonti Grand in Cortina!

[Lotusfab]

Very cool!

[Lex Templar]

35 minutes ago, Lotusfab said:

Very cool!

I guess you should have one in the glovebox!

[Andyww]

On 29/09/2020 at 18:37, drdoom said:

Andy, I'd be pleased to hear of your experience with the Excel EFI conversion so if it suits you perhaps a new thread over on "Engines . ."?

It was such a long time ago, I cant remember a lot of it. I remember the biggest issues were installing a recirculating fuel system (Turbo Esprit already has that!) and the cold-start idle air was never right. The system I used was called SDSEFI and amazingly is still available. I believe there are better systems available these days, it was very "hobbyist" and the ECU and coil units looked like they were made in someones bedroom.

I used Weber throttle bodies to replace the carbs, that part was pretty neat.
It turned out to be very expensive and with hindsight I should have simply had the carbs re-jetted. What I didnt know at that pre-internet time was on the very late Excels Lotus has to deliberately under-jet them to get them through emission controls so they had flat-spots and hesitation from the factory which could be corrected.

[drdoom]

Interesting and not at all surprising, that note regarding the late Excel jetting. I am familiar with the SDS approach, a most rudimentary digital EFI/spark solution that nonetheless has its merits. Thanks for the reply.

Cheers 

[LOTUSMAN33]

Fabian’s in print ! 😎

Fantastic write up and the 2CV looked magnificent 😂

No seriously get your copy as very good and the Esprit looked really good in glossy print 👍

 

 

Dave  

[Lex Templar]

Lovely to have it in print.

[Lotusfab]

7 hours ago, LOTUSMAN33 said:

Fabian’s in print ! 😎

Fantastic write up and the 2CV looked magnificent 😂

No seriously get your copy as very good and the Esprit looked really good in glossy print 👍

 

 

Dave  

Wow, I hadn’t seen that yet!

[LOTUSMAN33]

I subscribe so get it early mate 👍

My eyes lit up when I opened the envelope, it looks Ace Fabian so well done you.

 

[Lotusfab]

Thanks mate, I have press reader but its bot on there yet. I wonder what they wrote, as I haven't seen any of it! The 2CV was really cool! 

[LOTUSMAN33]

Here you go, hopefully you can read it until your copy arrives, you think they would have sent you a copy first especially as making the front cover.

Dave  

[stephenwhyte]

Look forward to reading the super-glossy clear Readly version to see the Copper Fire shine😎

[Lotusfab]

Thanks Dave!

[Lotusfab]

I gave them a list of credits to include, but sadly it appears to have been edited out! So here it is as it should have been published. Apologies if I have forgotten anyone. Thank you all!