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Esprit Turbo project car - part3 - the further continuation - Page 257 - Esprit 'Project & Restoration' Room - The Lotus Forums #ForTheOwners Jump to content


Esprit Turbo project car - part3 - the further continuation


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Thanks to Voodoo motorsport the tyre is back on and the wheel is in perfect balance.  Steering is great at last with no vibration!
I test drove it with the new idle jet and holder. It needs idle tuning, the acceleration is more hesitant than before. So I will swap to the smaller chokes, tune it properly and try again. Then its a rolling road to hopefully sort the issue once and for all. 

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If it were mine, I'd be interested to test it with just the choke changes.  I also wonder if raising fuel level by, say, 1/2mm will have the desired effect.   I believe either/both of these measures will potentially enrich the mixture from transition. 

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Yep I will fit the smaller chokes tomorrow and try again. Its very tricky to get this sorted. I was told by a well know specialist they spent a whole day on a car with my set up and had to give up, they could not get rid of the stumble. It is now worse than before at the moment, but as we all know every change affects something else. This result was expected, but I had to confirm it. With the smaller choke more venturi effect, richer mixture and maybe main jets cut in sooner? We will see. Its a learning curve. I will spend as much time on this as is needed to perfect it. Lets hope the progression holes aren't the issue! 

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9 hours ago, Lotusfab said:

Yep I will fit the smaller chokes tomorrow and try again. Its very tricky to get this sorted. I was told by a well know specialist they spent a whole day on a car with my set up and had to give up, they could not get rid of the stumble. It is now worse than before at the moment, but as we all know every change affects something else. This result was expected, but I had to confirm it. With the smaller choke more venturi effect, richer mixture and maybe main jets cut in sooner? We will see. Its a learning curve. I will spend as much time on this as is needed to perfect it. Lets hope the progression holes aren't the issue! 

Fabian, there is indeed a great deal to this and we may well be running fuel which has evolved into something less than ideal for use with the original kit. Yup, the smaller venturi must activate the mains sooner, as will raising the fuel height. If you're going into this intrepidly you must be ever so rigorous with methods, otherwise less likely to succeed. Starting points include the float height and fuel pressure regulation, assuming all kit in fine fettle. Resist temptation to stray far from established fuel height settings. There's a wealth of insights available on the Sidedraft Forum.

Cheers

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Having messed around with this since the engine was running I know this will be a major effort and cost £1000 plus to sort. Jets and rolling road time all add up! It will be worth it to perfect the car. The principles are easy. The tricky bit it getting the correct combination of jets, chokes, air correctors and emulsion tubes. On top of that we have the progression holes. I would not advise anyone to deviate from their stock engine unless they have a lot of cash to throw at the problem. I was advised to switch to forged pistons. In hindsight I should have tried to get forged pistons with the same design as the originals and not HC. I look forward to solving the problem and telling everyone how it was done, so they don’t have to spend fortunes to sort their engines.

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  • Gold FFM

I’m confused here. The pistons are the same size ? Or has the piston swap effectively  increased the cc of the engine ? 

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Only here once

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The other problem is inconsitency of fuel these days, and the increasing ethanol amount.

EFI cars with feedback can adjust to compensate but carbs cannot. I dont think carbs can ever be absolutely perfect and stay that way.

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Yep, but the gasket is thicker and makes .5 difference to the compression.Theorectically the effects should have cancelled out. Other builders have said there is no need to adjust the carb set up. That hasn’t worked with my build. The head skim has had more of an effect on this engine than I expected, as Dave Changes thought it might. The engine needs bespoke tuning. I have limited experience with these carbs, so will have to spend far longer getting it correct. When I get it drivable it will go on the rolling road. Heres the choke or (venturi). The size is stamped on it as in the picture. I am going from 36 mm to 35 mm. This in theory should make the car more driveable in the lower rpm ranges. 1B8875CB-40E6-47FB-94E8-559DE0FA297A.thumb.jpeg.1a899df321bb3c82811c2332319aad01.jpeg

I am hoping because its all rebuilt I won’t have to remove the carbs to get these out. If I do it will morph into a big job! 

These were supplied by Eurocarb and are fitted to the HC cars.

I have switch the idle jet to a 58 and gone weaker with the holder as per the HC set up. Hopefully when the choke is fitted the mixture will be richer at the weak flat spot. 

Right no more talking, chokes to fit!

I plan a test drive later today and will report on progress, if any!

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On 06/04/2021 at 06:51, Lotusfab said:

I think it will be fine if sufficient lubrication is on the barrel and wheel. Tyre bead sealer needs to be on the lip as well. I am using Voodoo motorsport to put my tyres on from now on. My local garage isn’t up to the task. They treat it as a modern wheel, which you really can’t. They have cost me four days of hard work and fractured a wheel lip so far! 

Looked this company up yesterday and will likely use them too when all mine are assembled.  One question though which I will probably get destroyed for........Are inner tubes a solution or a good reason why not?

 

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I suppose an inner tube would work.My front wheel is fine now Voodoo used the correct technique. I won’t bother going anywhere else from now on.

Well I am stumped. I just changed the chokes, it fired a few times and now won’t start! Back to basics?

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Careful !! There is NO correlation between choke size and startup. You may have assembled bits in some sort of disarray so check over what you've done. The change from 36 to 35 mm will be of no great consequence other than marginally earlier mains online but doesn't hurt to try and is without peril.

FWIW, Keith Frank ( chap referred to earlier in regard to tech analysis of carbs ) has determined Dellortos to be handicapped in terms of emulsion tube and slow run designs quite comparably to the Webers. Your transition behaviour issues will likely derive from these aspects, perhaps aggravated by modern fuel characteristics.

With the DCOEs it's been pointed out that one may run with main clusters removed altogether, for the sake of evaluating the slow run operation more clearly. Suspect it's the same with the Dellortos. This must be done with care to avoid any chance of needing deep throttle, as with traffic merging and avoidance events, but will permit low load cruise at a fair turn of speed. Checking in this way will offer some insight into the function of slow run jets, progression holes, and also the balance. Complex matter, this parsing of fuel delivery. 

In what sense were you advised to expect change of carburetion due to the small shift in CR?   

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Well I have been investigating  I found the forward carb float height was low and the rear high! I have used a method of measuring the fuel height in the bowl. It seems to be far more accurate. They are both 27 mm. I made gauges out of plastic to set the float height and a piece of cut bent metal to measure the fuel height in the bowl. Far easier than using a slide rule. 
This is of course nothing to do with it not starting, there is no spark! Now I have to find out why. I have a megaspark coil running with lumenition, maybe this is the issue and the amp has packed up? Bit of a coincidence it has happened now though! 

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The Lumenition amps are very reliable except for the very early type. A weak point is the connector between the optical sensor and the module, with the Molex plug. If you have been going in under the carbs you might have pulled it apart. 

 

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Hope so! 
Well I have just been trying to solve the ignition problem. I shorted the blue and black wires on the module. There is a spark. So the amp and coil works. The fault is probably in the wiring to the optical sensor. To test and repair very tricky in situ, I might have to take it out.

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The specialist did the bearings and clean I did the rest. I am the culprit who set them wrong! I must have misread the vernier. This time I used gauges, much easier. I also tightened the floats around the spindle , , they were rocking slightly which might have allowed the floats to snag.

I am truly stumped by this ignition problem. I tested the amp it works, the optical switch works, the distributor is turning, but no spark at plugs???

could it be the rotor arm or distributor cap??

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Well that doesn't leave much else!   Presumably there must be a path to earth in the distributor, but its a mighty big co-oincidence that it should go fall after you have been working close to this area.   You could substitute your S1 rotor & cap to test?

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