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CHANGES last won the day on April 25

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  • Birthday 28/09/1958

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  • Name
    Dave Lisle
  • Car
    Esprit SE, (modified)
  • Modifications
    See 412 bhp thread
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  1. @Andyww I call that great research and development, Shame they did not carry it forward onto the Stevens model..
  2. I bet that was a surprise.. Many years ago I lost my bonnet.. And i never saw it go .. Yes i was looking forward , but it happened so fast i never saw it , only heard the wind noise change.. I had to go back 3/4 mile to find it impaled on the central reservation barriers ... and yes it just ripped the hinge plates straight out of the bonnet ... Ohh, one of the many joys of owning an Esprit. ( I may have been doing a bit more than 50 mph at the time ) At least you were saved any damage ..
  3. I believe there were comparable test done many years ago , not sure of figures . However I found improvements when setting up with 104/104 over 100/110.. You need to remember 100/110 was done for emission reasons for the USA market . To save on costs Lotus did a one fits all policy , this mean't the Esprit was built to meet the tightest emission laws it would encounter in the markets sold in. We did some back to back on an S4, which after fitting verniers with 104/104 cam timing and Alunox exhaust manifold , managed to achieve 300 bhp using oem ECU set up and 1 bar boost and not much else . As Ian said , any cam timing is only an approximation based on where the closest dot alignment at TDC can be achieved .. The moment an engine no longer has the original factory head gasket format , the cam timing goes out .. only slight but not perfect .. The only other way to keep this spot on is to measure your original gasket , get the crushed dimension of your new gasket , and then skim the head for the different thicknesses ..... Assuming the new gasket is thicker, and the timing was cock on before. When you consider the allowance on the original head skim and gasket replacement was 0.018'', it does not take much working out to realise , with what is available in gaskets , and how many times a head has been skimmed , chances are cam timing will change .. When i do a customers engine, i always do a cam timing check before disassembly , In most cases the cam timing is not to spec.. This gives me some idea on machining history before i start , I always recommend 104 /104 and verniers on rebuild , as a result those all get spot on cam timing . They all seem to run smoother , i expect this is to do with timing accuracy and the 104 set up .. On emissions , i have not had any issues with 104 set up on MOT's in the UK .. Great job @Chillidoggy , well thought out and executed with precision .,.
  4. Fabian you must do what you feel is right... When you put forward the data as you do then you can make the figures produce the SCR you desire. I can only point out what I see in you pics, plus what you have written , then base this on what I have experience in .. A standard combustion chamber is between 40- 42 cc depending on valves and details etc , I always use the 40 figure a reasonable guide . So using your own logic that 8.0:1 SCR is your set up with a 1.2 gasket.. You now have a 1.651 gasket. The difference in volume between the two gaskets is 3.3 cc ... Your combustion chamber has reduced by at least 3.0 cc based on your measurements of 37 cc . So taking out 3 cc from the head and adding in 3.3 cc from the gasket , This will put you SCR at back to 7.98:1.. This is just basic logic nothing else . The 0.25 figure i was referring to in my post was the deck height , not head skim ... 0.25 is only 0.0098'' Looking at your pics I notice the head is skimmed to the inlet seats. I have skimmed a head to just past that point which was 0.045''. This gave me a head volume of 33cc and a final SCR of 8.5:1 on that build. However that is all irrelevant. I only mention it because the head volume is crucial , I just wondered, did you remember to subtract the extra volume caused by the valve recess voids in the pexiglass, when you made your measurement. It all adds in to the final figure .. If you did not then you can still get a basic measurement off your plexigless plate .. and recalculate.. Also did you remember to allow for the meniscus curve on your burette . I'am not a fan of guesstimates, which is why i have tried to go into detail so you can have the most accurate assessment of your engine SCR.. Only you have done the measurements and if you are confident with your chamber volume at 37 cc and have allowed factors mentioned then regardless of what the head was skimmed too we still come back to 8.0:1 .. Personally I can not put any more input to this subject , if you still feel i am wrong with all this then disregard my comments . As i said before putting it on a dyno when done will help match any anomaly and give you piece of mind.. good luck with the rest of the build ..
  5. With the greatest respect Fabian , what went on with gaskets in 1993 etc has nothing to do with what you have now.. Fact.. You now have a 1.7 gasket , you now have a 8.0:1 set of pistons with a 23.5 bowl , You say have a combustion chamber of 37 cc , you have a a 95.27 mm bore , you have a 76.2 mm stroke, and a deck height of circa 0.25 mm ... The rest is just math. You really need to concentrate on what you have in front of you , instead of looking for it fit what you would like it to be .. The fact is , even if you had left in your original pistons , grinding the head and reducing the cc to 37 would increase your CR by 0.25 to 7.75:1 . It really comes down to when you make changes , things WILL be different.. This is what i was trying to make you aware of when i pointed out the volume / CR checks to be made.. None of this is a real problem , what you have is very serviceable . You are running the forged pistons that can take extra final CR , which is just more in line with the injection charge cooled cars than your original spec. The reason for making you aware is so you can adjust you tuning parameters to suit. If you want to maintain your existing carb jetting and dizzy set up , then you would need to control your boost accordingly.. BUT... If you want to run original boost and higher final CR that is also fine , you will gain more BHP , But you would need to get it all set up on a dyno with re-jetting/choke and dizzy re-formatting. Running std boost level with higher final CR on std tuning set up will cause detonation at higher revs from running advanced and lean , it would feel really quick like that but be damaging the combustion area at the same time .. These are the sort of changes people make and don't address properly , then moan like hell when it all goes south... Now you have been there once , none of us want to see you go there again.. The advise on how to deal with what spec you have arrived at is simple... Please don't over complicate or over think this..... Just move forward and do one of the two options to facilitate the build spec you have..
  6. Sorry to bring this up again , but i can not help feel there is something amiss .. I base this on logic of 8.0:1 pistons with skimmed head will be higher than 8.0:1 not 7.7:1 .. To get an idea of where i am coming from .. lets put some base figures we normally find on a stock engine with 8.0:1 pistons into the calculator.. Bore at 95.27... stroke at 76.2... cylinder head chamber at 40cc... H/gasket 'crushed' 1.651... H/gasket 'crushed' bore...97.3... deck height 0.25... piston bowl 23.5... The result we get is 8.001:1 ... This is what we would expect to see.. Some may vary but only slight.. I can only assume the piston bowl and deck height measurement you made has at 33 may be wrong.. I work out the combined figure should be around 23.75.. This would be an easy misread to make .. Now if we Add in other measurements you made , like cylinder head volume @ 37 , and make allowances for the 33 figure being misread .. we end up with 8.283:1 This would be a more what we would expect to see. However looking at the picture of the head , it has been machined down to the inlet valve seats , I usually see a volume of just below 35 when skimmed to this , even with cut back valve seats .. .. This would give a SCR of 8.483:1 So it may be safe to assume the SCR is somewhere between the two or at least the lower of 8.283:1 .. To be on the safe side and get the best timing and fueling , I would set the turbo waste gate to account for this in your final boosted CR. On the up side , it will be a bit more responsive off boost low down . You may need to very slightly adjust you timing and low down jets , but a dyno technician will fix that very easy. It will only be slight tweaking to refine and get the best from all that you have done .. Hope this helps clear up any doubts .. Dave
  7. Yes , that is close enough .., I use 0.065'' which is a near as dam it 1.7mm .. unfortunately you have made slight error here ... The deck height is from the top of the piston crown , to the top edge on the liner. Because the piston can rock in the bore when checking, i always take a couple of measures.. 1 from the piston edge directly over the wrist pin.. 2 and 3 from 90' of wrist pin .. with 2 and 3 , I rock the piston taking two measurements on both and then the average will give me measurement when piston flat. This should be the same or close to #1 measurement if different i take the average of the two . But because you measured the piston in the bore at TDC , the volume you will have come up with will be the piston bowl and deck height together in one .. In this case you only need to add it on to the gasket and the combustion chamber volume along with the swept volume, to give total volume , then calculate from there .. hope that helps .
  8. What I was trying to bring attention to, is that the focus should be on ALL points, nothing should be overlooked as they are interlinked.. With the component changes made and the work that was done on the head , there was high possibility static C/R would increase significantly .. I am not sure how much Fabian was aware this tied into the boosted final C/R and the influences it could have .. You are quite correct in saying fuel delivery and ignition timing need close attention . However by maintaining the final boosted C/R, the fuel delivery and ignition should be able to remain within the factory settings .. It is far easier to gather this sort of data during the build , even if it takes time . By doing so it make you aware of any compensatory adjustments that will be needed , as in this case boost level.. I must be honest when i say, the SCR Fabian has is a lot lower than i expected with the work done.. Not sure how an 8.0:1 piston set up with a well skimmed head can end up a 7.76 :1 .. I did notice the piston bowl volume was measured in the bore , this is quite normal and easier to do with the forged piston crown shape. However this measurement will include the deck height volume as part of.. Fabian listed this separately in his data at 3.45 mm . This is 0.136'' which also seem a bit high , i normally expect forged piston deck height at between .0.010'' and 0.040'' depending on build spec. However there are several spec changes in this build , with machining and a cross over of parts ie early block late pistons etc which will mix up the norm .. If all the data is correct then this has all worked out for the good .. I would just ask Fabian to re check data content and reaffirm . As i say , the SCR is not an issue , these all vary when machined , its just the adjustment to the boost level that is needed to keep things within the ignition and fueling window..
  9. At 7.76:1 you would probably be fine.. You could also just tweak boost back a fraction to get spot on .. You can use one of the on line calculators to give boost for required final C/R. I have to take my hat off to how quick you did all the measurements.. well done .
  10. Unfortunately a compression check will not give you the exact compression ratio. You can divide back the psi reading you get by 14,696 as a guide , but unless you calculate in the cam timing / overlap , is will just be a figure. With the valves opening and closing earlier or later your compression check psi will go up or down . Because of the machining your valve timing will almost certainly be slightly off spec, so any factory psi on comp check will be off.. The early engines were the 7.5:1 but the piston crown you have now will be for the 8.0:1 .. This will also be influenced by the deck height you have, which can be influence by other factors. Your gasket thickness is part of the calculation , but should not be seen as a compensatory factor for piston change, etc.. The thicker gasket will only offset the head skim up to circa 0.010'' .. Valve recess / cut back will lower ratio but only to a point. When doing this you have to dial in the shim clearance setting.. Std they are 0.100'' to 0.085'' , you don't really want these going below 0.060'' if you can help it.. so you see the restriction.. The only accurate way to do this is to measure whilst you still have it in bits.. Otherwise its best guess.. uhmm. It is not really that important what the actual C/R is , as long as its not silly high.. But knowing it is ... What you want to achieve is the correct final C/R under boost. This will then allow your ignition , carburetor and fuel type tuning to be in sync as designed .. Your adjustment factor will be your boost settings,.. you may have some anomalies off boost but they will be very slight and insignificant in comparison. But without knowing the exact static C/R you wont know what final boosted C/R you will be running at.. Sorry if this was a bit long winded , but i would rather you be aware of fact than carry on regardless.. Keep up the good work ..
  11. Looks very nice Fabian , , what extra's have you had done , other than change the valve material spec. ( so much can be done , it would be nice if you could list it all with photo's ) ... I would also be interested on the chosen combustion chamber volume , looks like its had a good skim and valve seats cut back.. You will need to know this , along with your piston bowl volume , deck height and chosen head gasket squish size , to calculate you static compression ratio. Especially as you have changed piston type and block as well . When you have your static C/R figures , you can then calculate your waste gate boost setting requirements to give the desired final C/R. Otherwise you could be showing stock boost level but running much higher final C/R.. I would also put a bit of thread sealer on those grub screws. Keep up the good work.. D
  12. This is totally correct , and as we discussed, it does make a difference, maybe very small , but all the little things do add up .. They are not.. basically they fully shut . However they never produce a full cut of .. The stop screw should be set to just touch when they are fully closed , This will prevent the return springs making the BAV have a forced contact with the TB its self.. In the past i have seen TB's with marks from the BAV in the TB inner wall , at the contact points.. You will always find one balance screw on each TB fully shut , the other cracked to balance the inconsistency in assembly.. Once you have disassembled them this original setting go out the window.. Also you will find over time even with the filtered air that passes through the bleed hole past the adjustment screw , it still gets a deposit which will change the flow characteristics.. This is normal and found in just about every TB set up I check.. This is true when the cars were new and being serviced by the dealers... Rest assured any post tuning that will have been done would of included checking the individual balance criteria.. The anti tamper screws will have been removed and replaced if adjustment was needed.. Now these cars have so many years and miles on , it would be prudent to check , This is done with a throttle flow meter , which is a very simple process to do .. Once you have balanced and set the whole system you should have tick over controlled by the ECU via the IAC valve . If this tick over is to low , I would first check the IAC function , if all is ok then any micro adjustment can be made via the stop screw or the by pass balance screws .. It is very rare to need any micro adjustment if everything is working as it should. However , most of these cars are circa 30 years old and still feature original injectors , which have never been cleaned or replaced, along with other ignition parts like the coil packs .. All of these over time deteriorate , so having a micro adjustment facility can be useful.. to compensate. I must stress that you need to be aware of what you are doing and if unsure consult a reputable dyno technician to do final set up, then do a power test to clarify all functions are performing correctly.. A power run is the only way to insure your ECU is calibrating the engines functions correctly ie. secondary injectors coming in on time , The TPS function is calibrated within range ETC ETC,, So if unsure just Ask someone . !!! A useful bit of kit to have
  13. Just to clarify a point. The polished s/s part is a reflector. The asbestos bit is the heat shield.. There should be an air gap between them to also help dissipate heat.. Failure to fit the bit you chucked will result in the s/s reflector being able to come into contact with your leads.. This part WILL get very hot from the turbo, and WILL damage your leads over time. Lotus would not have gone to the cost and trouble of having it made and fitted if it was not essential ... If you choose not to use the actual part , then i strongly suggest using an alternative.. It will save ignition issues at later stages
  14. A good way of saving this sort of area is by metal plasma spraying. This can build up the surface without introducing the heat levels that cause distortion.. It is quite common to see this used on classic cranks that have reached their machining limits. Once a suitable thickness has been achieved the area can by ground to size.. If in the case of thrust bearings the area is still on the low side ( needing thicker than available thrust bearing ) , then get someone to machine from a bronze cord the required thickness, job done .. This process is nothing new , vintage and veteran car restorers along with historic race engine builders do it quite often when no replacements are available ..
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