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ECU, Engine, Injector, Coils or something else - Page 3 - Engine/Ancilliaries - The Lotus Forums Jump to content
modifiedv8engines

ECU, Engine, Injector, Coils or something else

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Ah Ha .....thats even better news .......

Maybe some adaptive story telling to match my diagnosis here but could it be the damaged turbo seal, or whatever has pumped some oil through the intake and #4 cylinder being the closest to the TB, it gets the oil first .........this is a thought but would need to have a fag and a cuppa to think more about this possibility. 

Another point of interest

The 4 cylinder cars 910/912 engines run 8.0:1 CR with a compression pressure quoted as 9.5 bar (140 lbs in2)

The 8 cylinder cars 918 engines run 8.0:1 CR with a compression pressure quoted as 10.7 bar (155 lbs in2)

So the V8s get another 1.7 bar pressure ?? from the same compression ratio !

Manual has a typo error there !! 

So can anyone enlighten us to some measured compression pressure numbers ( actual not from the manual) please.

 

 

 

 

Edited by modifiedv8engines

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Something else to consider Derek .......based on the compression number in this case 8 x Atmospheric pressure 14.7 /1 = 117.6psi. So Lotus added another several psi to get to 155 apparently .......that is indeed a big effect ! Based on that, the 4 cylinder engines would appear to have less duration and lift perhaps with a peak of 140 psi . 

Then there is the accuracy of the gauge, if its sealed correctly, engine temp, and the speed at which the battery/starter is able to spin the engine.

 

 

 

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1 hour ago, sailorbob said:

Cam duration and lift can have a big effect on the compression ratio.

Pressure not ratio!

You cannot simply multiply the compression ratio by the pressure of air at one atmosphere to derive the compression pressure because, in addition to the cylinder filling not being 100% due to things like the cam's effect, the act of compressing the air also raises its temperature which, in turn, raises the pressure.

 

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Derek its nice of you to point this out but all Im trying to find out is irrespective of the laws of physics and yes we know when gases are compressed, heat, expand etc but has anybody .........actually measured the compression ratio ( or pressure ) of their Esprits V8 engines other than me as I would like establish a comparison....thats all. 

My question if its answerable is 2.0,2.2, 3.5 litre Lotus engines all run a 8.0:1 CR piston yet the cylinder pressures are very different - 1.2 bar difference due to cam duration and valve lift ?

Or some actual results from compression pressures from a 4 cylinder ......you know, the half a V8 engine version 😉

Answers on a post card please  

 

Edited by modifiedv8engines

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I cannot help with V8 compression pressure readings but on a couple of 910 engines cylinders #2 to #4 were about on spec. but cylinder #1 was down by about 20-30 psi. Both ran all OK though.

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When I tested mine a year or so ago they were all somewhere between a little over 9 and 9.5 bar. Since they were fairly consistent I put down any lack of compression down to the gauge inaccuracies (since it suited me to do so). I'll dig out the pictures if I can find them.

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13 hours ago, modifiedv8engines said:

you know, the half a V8 engine version 😉

The amount of charge within each of the smaller V8 cylinders is substantially less. 

2200cc ÷ 4 = 550cc per cyl

3500cc ÷ 8 = 437cc per cyl

A smaller charge then compressed to within 1/9th of its original size will create a higher pressure.

 

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Theoretically, cylinder pressure depends on the valve timing and CR, as has already been said. I seem to recall the 910 being around 140 psi per cylinder, but there's so many variables which can affect the test. Personally I would look for consistency across the cylinders when testing, unless they're showing ridiculously low, in which case engine performance will already have dropped off noticeably.


Margate Exotics.

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23 minutes ago, Steve V8 said:

A smaller charge then compressed to within 1/9th of its original size will create a higher pressure.

Can you explain why? 

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Cheers,

John W

http://jonwatkins.co.uk

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Thanks guys.........thats really very useful information and no doubt will assist others too when they get to that stage where they need to reach for that compression tester.

 

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2 hours ago, jonwat said:

Can you explain why? 

idk GIF

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46 minutes ago, jonwat said:

Bullshit then :rofl:

Not at all John...I just don't don't have the mathematical skills to create an equation to prove the density of a compressed gas compared to an uncompressed gas within two specific cylinders taking into account bore and piston stroke within those cylinders...or I would

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The cylinder capacity does not affect the compression pressure. For a given mass of air, if you compress it to half its original volume the pressure will double providing the temperature remains the same. It does not matter if the air mass occupies a volume of 1 m3 or 1 cm3, see Boyle's law if you want to know the theory behind it.

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47 minutes ago, sailorbob said:

The cylinder capacity does not affect the compression pressure.

As I thought. :thumbup:


Cheers,

John W

http://jonwatkins.co.uk

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1 hour ago, sailorbob said:

The cylinder capacity does not affect the compression pressure

Well something obviously does, 1.2 bar is a big difference. I cant see that valve lift/duration would make any difference at compression test engine speeds.

 

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The V8 camshafts have less duration then the 4 cylinder camshafts which could mean some of the air charge is being lost out of the exhaust on the 4 cylinder. Also, the 140 psi quoted for the 4 cylinder is the minimum pressure whilst the 155 psi  quoted for the 8 cylinder is +/- 15 psi which means the difference is not necessarily 17.4 psi.

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Make of the following what you will and its probably your explanation Sailor Bob thats close/correct.

To recap - Compression test pressure range within approx 1 bar. Hot Comp test ( lost count of how many) but both middle cylinders on both banks give a slightly lower compression pressure so thats cylinders 2,3, 6,7.

Cylinders, 1,4,5,8 higher

Leak down test ( Sealey VSE 2060 ) pressure 25 psi as recommended by Sealey technical support ( not a bad tool for £45 quid) but disregard the instructions as the leak  gauges will hit the stops if you use 100psi). Blurb says bigger capcity engines tend to leak more than smaller capacity engines but fail to give an example.

Leak down pressure recorded as moderate on a cold engine which indicates 35% leakage. This was for cylinders 1,2, 3, 5, 6, 7, 8 with cylinder #4 slightly better @ 25% 

Pressure leakage to crankcase via piston rings  - no hissing from inlet, exhaust, or air bubbles from header tank.

Not too alarmed at those results and with cats removed which are clear/clean, Im reasonably confident that the bank # 1 turbocharger is at fault.

Weather depending ......will re-install spark plugs tomorrow, start engine and see if the impellors are spinning, as the shafts in both units have some slack/play but other than oil deposits on bank #1, look okay-ish. 

 

 

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Had a good search but does not appear to be any write ups on V8 turbocharger removal (engine in situ).

Any tips would be most grateful .......guessing crow-foot wrenches for the mtg to the exhaust manifold but no doubt once the car is supported on stands and the next several hours with dust, grit, coolant and oil dripping in my eyes and face I will have another job crossed off the list. 

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There is no easy process - you will want to remove as much as possible to improve access, including feed and return pipes and the wastegate actuator.  I've also had to split the turbo (meaning removal of the CHRA and compressor) in some cases.  Hopefully it will not be so painful for you, but it is not a pleasant or easy job.   You may need heat or even to split nuts in order to remove seized parts.

Take regular breaks for tea and deep breathing exercises......


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Thanks Mike

Did I read somewhere the Brown SEIMANS Fuel Pump Relay was a the only relay suitable for these cars ?

Replaced with a new Land Rover AMR something or other -  Put the old Siemans relay back in and seems to spin the engine over much faster !!! (stumbled on this one when removing fuel pump relays to double check for sparks from the coil, leads to the plugs )   If I pull the fuel pump relay to isolate the injectors and pump - I get no sparks to an earth position, like a plenum bolt and by that I mean spare plug, pushed into plug boot and earthed) 

With cat pipes removed @ idle no oil/fuel smoke ......apply some throttle and smoke haze on the overun on bank #1 turbo but no oil.... just smoke.........like its over fueling 

Bank #2 turbocharger wastegate poppet valve loose/rattling so that helps to partly explain the rattles/popping noises from exhaust which I wouldnt of found without removal so solved something today.  

Seem to be going round and round in circles thinking haunted, thinking ghostbusters

I really cant think WTF is going on with this car injectors, secondary injector seals, coil packs etc etc all of which have been checked or tested and still not much further forward ..

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You've not tried a different ECU... 

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1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Minded you mentioned that some time ago Mike.....could be that I suppose so just need to find a local car to test my ECU.  

 

 

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It's my post on page 1 about there being a TSB stating to use a Siemens relay for the primary fuel pump relay and ignition relay. I cannot recall if it gave the part number for the relay (it probably did).

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