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S4s leads / coils / injectors typical resistances

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Hello Everyone,

Something is wrong with my ignition so I would need a few infos:

  • What should be the typical resistance measured for each lead? (Mine are original Lotus ones, age unknown — I had measured them already but I will have to find the paper ...)
  • What is the typical resistance measured at the coils?
  • What typical resistance should be measured at the main and secondary injectors?

As always, thanks in advance!

PS: Would anyone confirm the coils, coil plates and ignition control module are the same than the M100? I could swap them and give a try but I think the coils on the M100 are a bit tedious to access (not sure at all though, just vague memory, I never had to replace them so far)

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My injectors measured 2.1 Ohms for the primaries, and 1.6 Ohms for the secondaries.

As for the ignition leads, or original coil resistance, perhaps the info is buried in the Service Notes, however I fitted some new Moroso coils (8224) with 0.35 and 7.8K primary and secondary resistance if that helps. If you're stuck I could measure the original ones I have.

 

The D.I. module remains a mystery, and there's a lot of different types out there. @sailorbob and I spent a long time trying to identify it, but unless he's had a eureka moment, or some good luck recently, from memory we only managed to decide which version it wasn't, rather than what it was. It could be Lotus-specific, but not sure. I even bought what we thought might be the correct version and fitted it, but while it worked perfectly, it triggered the CEL. From our research, that is what happens on every one of them, and as the originals are NLA from Lotus, they could be a problem in the future.


Margate Exotics.

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The secondary injectors are high impedance Injectors. They should be around 16 Ohms and not 1.6

The primaries are driven by a FET for each pair, and have current sensing build into the drive circuit. (Peak and Hold Injectors).

The secondary injectors are driven by one of the QUAD drivers IC in the ECU. (2 outputs of the driver parallel connected). (Satured type Injectors) 


Esprit Freak

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Thanks!

And as for the ignition leads? I think I remember each one had a different resistance from the others. I know they are not the same length, but ... I will have to measure their resistance again.

 

5 hours ago, ian29gte said:

The D.I. module remains a mystery, and there's a lot of different types out there. @sailorbob and I spent a long time trying to identify it, but unless he's had a eureka moment, or some good luck recently, from memory we only managed to decide which version it wasn't, rather than what it was. It could be Lotus-specific, but not sure. I even bought what we thought might be the correct version and fitted it, but while it worked perfectly, it triggered the CEL. From our research, that is what happens on every one of them, and as the originals are NLA from Lotus, they could be a problem in the future.

If it's the same as the M100 Elan ones, here is a cross reference that is OK apparently (it's not free shipping outside the USA though):

Quote

https://forum.lotuselancentral.com/viewtopic.php?f=38&t=25683#p325148
The ignition coils are GM with part# DR39 and were $10 each w/ free shipping. The ignition control module are also GM with part# D1927A, but this one is actually a Delphi unit # GN10092 and cost only $24 with free shipping

Quote

http://forum.lotuselancentral.com/viewtopic.php?p=95710#p95710
Lotus Esprit uses the same coils as Elan M100.

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I found the information on the plugs leads, at least for the Magnecor's -  http://www.magnecor.co.uk/userfiles/files/Spec_sheet_for_KV85_R-100_for_UK.pdf

You're in luck! I have a D1927A here that you can have, I'll even sell it to you for a substantial discount as it's only ever been used for about 10 seconds.


Margate Exotics.

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Indeed that's interesting, thanks. I read that it's 72 ohms per cm, so as expected the length affects the leads resistance a lot. Isn't that a problem? Wouldn't it be better to cut the leads the same length?!
I know SJSportscar sells both the Lotus and the Magnecor leads: what is the general consensus about what to buy and why? For instance is the KV100 any better than the KV85 in the real world for a stock engine?

As for the D1927A, do you mean you bought it and tested it on the Esprit and that it doesn't work? I don't need it for now as the Elan's engine is running OK but I could be interested to buy it as a spare indeed ^^ (it's strange it doesn't work on the Esprit and it's working on the Elan, it's a pity)

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You won't notice any difference as long as the leads are in good order.

It's exactly as I said before: A D1927A will run perfectly well on an Esprit, but it throws up a CEL when fitted. And that was the problem with all the DI modules we investigated. If you want it as a spare for the Élan, then PM me.


Margate Exotics.

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The M100 Elan uses a cam angle sensor for the sequencing of the injectors which is why the more common DI modules work on it but not the Esprit.

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IMHO, If the leads are old, don't bother wasting time trying to determine the correct resistance, just replace them with a set of quality leads. 

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1995 S4s

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