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Esprit Turbo project car - part3 - the further continuation - Page 253 - Esprit 'Project & Restoration' Room - The Lotus Forums #ForTheOwners Jump to content


Esprit Turbo project car - part3 - the further continuation


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On 28/10/2020 at 21:38, Lotusfab said:

Thanks Roo, been a long road!

what a nice article is that, and what did you have a long time spent on this beauty,

i gone do the same with a LHD but not as good as you did, (i think) i keep the steering wheel black and so on...

but it will get compomotives but no roof stereo,

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My luck has really turned. Just got the speedo drive working! I jacked the car up, put it in gear and ran it whilst I messed around. I discovered even with the nylon and brass drive held in by a 9 mm

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Seems like they built a big house just behind where the original picture was taken. 🙂

Your car is an absolute delight Fabian. 🙂

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It's getting there......

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  • 3 weeks later...

Update

I have done some testing of the ignition timing advance. The curve is not correct resulting in ignition timing that is far too advanced. Thats not ideal, especially with forged HC pistons. I am removing the distributor. I don’t have a test rig and and don’t wish to make one so I am sending the distributor to distributor doctor. They will refurb it and plot advance curves before and after. The springs have probably gone weak. I plan to set up the suspension over the next few weeks using the string box method. Its then off to a rolling road to fine tune the jetting. All part of the fun now the car is in one piece! Cortina awaits!

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 Hi Dave, not sure depends on how the covid stuff goes. Also need to do some serious miles on the car in the uk first, once I have the suspension and jetting sorted.

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Well my distributor has come back. I sent it to Distributor Doctor. An excellent company. They plotted the advance curve and surprisingly it was spot on within 1/2 a degree. They said the distributor was in very good condition and didn’t need a rebuild and only charged a nominal fee! Heres the plot.7AB04BC1-8117-4F32-B958-06C00168BF3B.thumb.png.55fd63939c8b03ac345eebb9290beb64.pngThe reason I sent it to them was the advance curve. I have a variable timing light. I was using the advance function to make readings easier when setting the timing. It gave 25 degrees advance at 2000 rpm when it should have been 20. I couldn’t get the timing at rpm consistent over the whole range. Now I know the distributor is spot on the error must be in the timing light variable advance. I will reinstall it and set the timing using the zero advance setting on the light. After this a friend has organised a dellorto expert to check over the carb set up. I then plan to take it on a rolling road. I still need to se5 up the suspension and plan to have the wheels balanced on the car. Compomotives are beyond the capabilities of most garages. I had two leaks when I switched over to new tyres caused by the garage using excessive pressure to seat the tyre rather than lubrication and a little effort. When I saw what they were doing I stopped them! Two days wasted dismantling and resealing the split rims. No more than 40 psi should be used when fitting tyres on comps and they must be very well lubricated!

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Fabian,

In regard to tuning the carbs and spark curve do be mindful of the likelihood that fuel has evolved substantially since the time our cars were engineered. Pinpoint adherence to either original jetting or timing is not necessarily the correct answer. Well proven tuners in the UK capable of setting up what your engine actually wants are identified in these forums from time to time.

Cheers

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Thanks Steve your right of course. I am trying to get the basics as per the book before I put the car on a rolling road. I have just put the distributor back on and run the engine. I can’t explain why the idle setting is 10 degrees BTDC and at 2000 rpm it still shows 25 degrees with the timing light on zero adjustment. it should be 18+/- 2 degrees with an idle setting of 10. The advance curve on the distributor is correct. All I can think is the rpm gauge on the dash is misreading. I have an electronic tacho coming tomorrow to see is the car gauge is correct. Any other ideas?

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There's a substantial history of confusion arising from Lotus' manner of expressing the timing specs, as commented on here and there from the earliest years. The most critical figure will inevitably be total advance under full load, as the engine either lives or dies by this under full boost. 

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You may recall I upgraded this engine to forged pistons HC spec.This is adding further complication to the tuning, as the compression has increased. The HC has totally different jetting and different model carbs. The rolling road people I will take it to have been tuning Lotus Esprits for many years, so hopefully they will be able to fine tune everything and get to the bottom of this.

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So I have been working on the tuning. I retarded the ignition by two degrees from the book value the engine seems to accelerate more smoothly. I have decided to try the idle jet and holder for the later HC car, as I am running that setup. It uses a 58 idle jet and a 7850-9 holder. The holder has larger air holes than the 7850-7 but the jet is much larger. The 9 holder is weaker than the 7. I am still trying to perfect the transition to 3000 rpm. The idle jet and holder control this transition. I tried to find some graphs explaining the effects of jet and idle holder without much luck. I though I would have a mess around before involving the rolling road. 

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Hi Fabian - In addition to compression, an HC uses larger inlet tracts, different inlet manifold and increased boost.   Additionally, you cannot directly compare DHLA40's to the HC's DHLA45's - as the 45's are a different design with an additional 'Powerjet' circuit and actually runs a smaller choke size than the LC models!  (my guess is they only went to a 45 body to take advantage of the power jet) - To avoid running lean at high speed.

When I was setting mine up, which does run an HC head, elevated compression and increased boost, I experimented with larger idle jet holders in DHLA40's and found them unsatisfactory as they immediately 'kicked' too rich as soon as the throttle was touched from idle, before transition occured.

I get pretty good transition & power off a 43 idle jet with standard holders.  I also run larger main jets and pump jet calibration based on an HC, which has a slightly elevated volume.

NB - What do your plugs look like, now you have a some miles on the engine?

  

 

 

 

 

 

 

 

 

 

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Thanks Steve, really interesting, because  of the number of variables maybe a rolling road is really the way ahead. Not sure whether I will even bother with the new jets and holders, now I know what you have already discovered. I knew the carbs were a different model, but didn’t know about an extra circuit. I also believe the HC has vacuum advance. The engine runs great beyond 3000 rpm, so I was thinking the mainjet, emulsion and air correctors didn’t need adjustment? Can you remember what sizes you used? 

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Fabian, please don't presume that the feel of the engine adequately sums up whether it's correctly tuned. With forced aspiration engines it is quite imperative that lean settings are avoided under boost, as is excess spark advance. Don't lean on it much before the pro's have sorted it out. Afterwards you may fiddle with driveability concerns once the base fuel and spark settings are sound. Cracked pistons and/or blown head gaskets are no fun. 

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9 hours ago, Lotusfab said:

 I also believe the HC has vacuum advance. 

I believe the vac advance on the HC is not used when the engine is warm, its cut in/out by a temperature controlled valve.

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10 hours ago, Lotusfab said:

Yep, I need to get it on a rolling road ASAP. I have an expert taking a look at  it next week. Hopefully he can steer me in the right direction. 

He will if he's at all worth doing business with. 😑

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