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How much can be milled off the Cylinder head?

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  • How much can be milled off the Cylinder head?

    In the process of replacing the CH gasket, I want to maximize the compression ratio of my gasoline Smart 42 Mk1 -2000.
    This because it will be run on 100% E85 only, so no knocking problem anymore.

    On many engines, the valves will hit the piston if you mil off too much of the gasket face.
    On the Smart, it seems quite OK, there is very vertical valves in combination with a big distance to the gasket face, and bowl in pistons too.
    And there are no cut outs for the valves in the pistons.
    Are there anyone who have tested how much distance it is between piston and inletvalve as minimum over a cycle?

    Second problm will then ofcourse be, how to re-time the camshaft when some mm are off the cylinderhead?
    Are there any offsett woodruffs or similar? Or should I aim for a full sprocket tooth...

    Its much written about tuing the Smart on the net, but I have found quite little about how to tune the internal of the engine, are there anything I have missed?
    Thanks for any advice!

  • #2
    Re: How much can be milled off the Cylinder head?

    No-one have a clew??

    Comment


    • #3
      Re: How much can be milled off the Cylinder head?

      dont think any one runs there car purly on E85. might be worth phoning a smart inde in the uk to find out

      Comment


      • #4
        Re: How much can be milled off the Cylinder head?

        ES: You are going places no one has been!
        If you really want to though, you will have to calculate the valve to piston clearance by measuring the valve lift in relation to cam degrees then equate that to crank angle degrees with respect to the cam timing. A laborious process and not made any easier with hydraulic tappets. The other method is to loosely assemble the engine with plasticene on the piston crown, rotate the engine over the overlap/gas tranfer period, dissemble and measure from the cuts in the plasticene the clearance. This method doesn't tell you when the clearance is at its minimum but the inlet valve out accelerating the descending piston is the usual danger point.
        Vernier sprocket is the usual method of re-timing a cam but I've never heard of one for a smart engine. An off-set key may work. One whole tooth will surely be too much.
        The other thing to watch for with a big skim is that the waterways aren't breached.
        A lot of work then..Good luck!

        Comment


        • #5
          Re: How much can be milled off the Cylinder head?

          Thanks Thrumbleux!
          Well Im not sure if Im such a pioneer, the same operation as you describe, many have made on other engines, not only for being able to run efficient on ethanol.
          However, I have not seen any engine from modern times, where there is such a hughe distance between the valves and the piston.
          As it feels now, I could even open one valve at maximum lift (any info of how much it is..?), put the CH loosely on the block, and turn the crankshaft and deform some plastelina, and even see a distance of some mm....
          I will try to do what U wrote now, couldnt imagine that it was a white spot on the map!
          Will report ofcourse!

          I didnt look closer to the sprocket camshaft yet, but will in the weekend.
          Yes, I will also be careful with the waterjacket!

          Yes, a full tooth of the cam sprocket is about 8 mm or so, and this much is ofcourse not realistic to mill off...
          Hmm, any idea where I can buy Vernier sprocket for the engine?

          Comment


          • #6
            Re: How much can be milled off the Cylinder head?

            Originally posted by ethanol-smart View Post
            However, I have not seen any engine from modern times, where there is such a hughe distance between the valves and the piston.
            As it feels now, I could even open one valve at maximum lift (any info of how much it is..?), put the CH loosely on the block, and turn the crankshaft and deform some plastelina, and even see a distance of some mm....
            It will be quite a roomy (spacious) combustion chamber being a turbo motor so what you propose should work. I dont know the valve lift (best measured with a dial gauge, vernier caliper or similar) but shouldnt be less than one quarter of the head diameter.

            Originally posted by ethanol-smart View Post
            I will try to do what U wrote now, couldnt imagine that it was a white spot on the map!
            Will report ofcourse!
            I don't understand the above - lost in translation?!

            Originally posted by ethanol-smart View Post
            Yes, a full tooth of the cam sprocket is about 8 mm or so, and this much is ofcourse not realistic to mill off...
            Hmm, any idea where I can buy Vernier sprocket for the engine?
            Don't know about vernier, but perhaps slightly retarded cam timing will be OK.Carefully check exhaust valve clearance as it will be the vulnerable valve with retarded cam timing.
            Incidentally, many manufacturers use the same cam timed slightly differently to achieve slightly different torque curves. Both Vauxhall (Opel) and Porsche (air cooled 911) have done so.

            Comment


            • #7
              Re: How much can be milled off the Cylinder head?

              Thrumbleux;
              It will be quite a roomy (spacious) combustion chamber being a turbo motor so what you propose should work. I dont know the valve lift (best measured with a dial gauge, vernier caliper or similar) but shouldnt be less than one quarter of the head diameter.

              -Yep, 1/4 of the valvediameter U mean.


              I don't understand the above - lost in translation?!

              -Only that I couldnt imagine that this was not explored more on such a popular tuning machine as the Smart.



              Don't know about vernier, but perhaps slightly retarded cam timing will be OK.Carefully check exhaust valve clearance as it will be the vulnerable valve with retarded cam timing.
              Incidentally, many manufacturers use the same cam timed slightly differently to achieve slightly different torque curves. Both Vauxhall (Opel) and Porsche (air cooled 911) have done so.

              -I agree, a normal VVT on a Merc is advancing the cam timing 20 degrees on lower rpm for increased tourqe.
              Some few degree of retarded cam wil probably dont do so much on an turbo-engine.
              On the other hand, with more focus on the lower rpm, maybe one could consider one full sprocket advance anyway, how many teeth we have on the sprocket? 30? One tooth would then mean 360/30= 12 degrees only.
              The engine might have less optimum breething at higher rpm, but hey, thats why we have a turbo!

              Comment


              • #8
                Re: How much can be milled off the Cylinder head?

                Originally posted by ethanol-smart View Post
                -Only that I couldnt imagine that this was not explored more on such a popular tuning machine as the Smart.
                Most smart tuning seems to be remap and external induction mods.

                If you check valve/piston clearance for a wide range of cam timings, you should be able to experiment once the engine is built and has run. Sounds as though you have some latitude.
                What compression ratio are you aiming for?

                Comment


                • #9
                  Re: How much can be milled off the Cylinder head?

                  Originally posted by Thrumbleux View Post
                  Most smart tuning seems to be remap and external induction mods.

                  If you check valve/piston clearance for a wide range of cam timings, you should be able to experiment once the engine is built and has run. Sounds as though you have some latitude.
                  What compression ratio are you aiming for?
                  Yes it really seems so. Turbos are too easy to tune!
                  I agree, I will see the borders now in the wekend, and will know what margins there are.
                  CR?, Well for the process of making a powerful and efficient engine, 17:1 is not impossible, see this report:
                  http://www.epa.gov/oms/presentations...01-2743-v2.pdf

                  What I want to stress the pistons and the conrods and bearings with might be a bit less, maybe I will stay by 12:1 or so, I will think about it...
                  With very high CR, a stronger starter might be needed in winter time, does the diesel Smart starter fit to the gasoline Smart engine?

                  Comment


                  • #10
                    Re: How much can be milled off the Cylinder head?

                    Originally posted by ethanol-smart View Post
                    Yes it really seems so. Turbos are too easy to tune!
                    I agree, I will see the borders now in the wekend, and will know what margins there are.
                    CR?, Well for the process of making a powerful and efficient engine, 17:1 is not impossible, see this report:
                    http://www.epa.gov/oms/presentations...01-2743-v2.pdf

                    What I want to stress the pistons and the conrods and bearings with might be a bit less, maybe I will stay by 12:1 or so, I will think about it...
                    With very high CR, a stronger starter might be needed in winter time, does the diesel Smart starter fit to the gasoline Smart engine?
                    The engine used in the report is a modified VW diesel engine with original compression ratio of 19.5:1. Have you considered how much you can machine off before puncturing through into the cooling passages?

                    Comment


                    • #11
                      Re: How much can be milled off the Cylinder head?

                      Originally posted by ethanol-smart View Post
                      Yes it really seems so. Turbos are too easy to tune!
                      I agree, I will see the borders now in the wekend, and will know what margins there are.
                      CR?, Well for the process of making a powerful and efficient engine, 17:1 is not impossible, see this report:
                      http://www.epa.gov/oms/presentations...01-2743-v2.pdf

                      What I want to stress the pistons and the conrods and bearings with might be a bit less, maybe I will stay by 12:1 or so, I will think about it...
                      With very high CR, a stronger starter might be needed in winter time, does the diesel Smart starter fit to the gasoline Smart engine?
                      The engine used in the report is a modified VW diesel engine with original compression ratio of 19.5:1. Have you considered how much you can machine off before puncturing through into the cooling passages?

                      Comment


                      • #12
                        Re: How much can be milled off the Cylinder head?

                        Originally posted by ethanol-smart View Post
                        http://www.epa.gov/oms/presentations...01-2743-v2.pdf

                        What I want to stress the pistons and the conrods and bearings with might be a bit less, maybe I will stay by 12:1 or so, I will think about it...
                        ES: Ignore the report - it is operating control strategies unavailable to you, ie EGR at high rates.
                        More to the point though, you will have to operate with control strategies as they are available from the smart ECU. Ignition timing is the most obvious parameter to create a problem. Despite what the report suggests, alcohol fuels are slower burning than petrol. An increase in advance of 6-15 CAD (crank angle degrees) over petrol fueling timing is usual when 100% methanol is used. A complete understanding of the timing strategy employed by the ECU would be of help - if available. Otherwise you may not get sufficient advance.

                        As for the actual final CR you use, I'd try and correlate the increased RON over petrol and how it relates to detonation (knock) suppression and then correlate the increase to the standard CR = 9.0:1 of the 700cc engine. (The internal cooling effect of alcohol is on your side in this regard). The 'blend' aspect needs to be factored in also.

                        I'd also want to estimate the peak cylinder pressure and compare it to the con rod capability based on known information from those who have really upped the boost on these motors. (I seem to recall a post from Ian at Big Performance saying that 'at 13X hp it was fine, at 13Y hp it went bang'. The difference between 13X and 13Y was in the region of 5hp). From the hp figure the torque figure can be calculated then the cylinder pressure (or BMEP at least). Working to a slightly lower than that BMEP to allow for a proportionally higher peak pressure should allow you to arrive at a safe figure for the CR that the rods can withstand.

                        Still the integrity of the head needs to be considered, not just for the waterways (and oil galleries) but for the loss of strength by reducing the deck thickness and hence stiffness. Without adequate stiffness the head will shuffle under high load running and you'll never keep the thing in head gaskets. The cam bearings won't appreciate a flexing head either. I haven't looked, but is it possible to remove metal from the block? If open deck, it should be possible without detracting from the block integrity.

                        For further reading, see if you can source info on speedway engines running methanol. For a long time they were pushrod 2-valve / cylinder motors (for a low centre of mass), and had to have a braod torque range (fixed ratio transmission), so the comparison to a road engine is closer than might otherwise be expected from a pure competition unit.

                        I'm not trying to be negative with this post - merely I want to make you aware of where I think you should devote your attention in order to make this a worthwhile and successful conversion. Plenty to think about then - but that's always the case with ambitious engineering projects!

                        PS.
                        How much relevent information is available from those who have raised the CR on other (non smart) engines to best exploit the different qualities of E85? Are they also running mapped management systems?
                        Last edited by Thrumbleux; 31-03-12, 11:55 AM. Reason: splng

                        Comment


                        • #13
                          Re: How much can be milled off the Cylinder head?

                          Tolsen and Thrumbleux,

                          I know that the integrity of the CH is important, especially if you want to do something with a highly stressed engine like the Smart.
                          However, my aim is not to combine maximum performance with minimum fuel consumption.
                          Even if the fuel is giving a lot of opportunities in both areas, my main target is fuel efficiency and a better coldstart.
                          The performance is there, and with higher top pressures one need to be careful, and not allow too high boost.

                          I have a profficiency in combustion development so I know about the issues with flame propagation and burning speed.
                          The thing with ethanol is that (all now compared to gasoline), there is a quicker burning during the main combustion, but a slower ignintion delay (a very well known term in diesel-combustion deveploment), which during some circumstances are giving a need for a more advanced ignition timing, but in other situations a retarded or equal timing as on gasoline.
                          There are some effects of this, one is higher efficiency due to less cooling losses.

                          When EGR is introduced in high amounts, the ignition delay and the main combustion is slower, and the same applies for ultra lean operation which is another parade dicipline for ethanol.

                          Thrumbleux' idea of milling off the cylinderblock instead is brilliant, and something that is without any issues, I think.
                          As you say, an open deck block is perfect for such operations, and it should be explored sooner or later.
                          The only problem is that it is part of a total removal of the block out from the car, something that I might consider if needed in a later stage of my Smart-life...:-)

                          All this I know, and with time, I will start to explore the lean burn capabilites of the Smart engine as well as I already did on the M102 (MB 190 E 2.0 with KE-jetronic), and my AMG C36, which is equipped with a broadband-band lambda and a piggy-back ECU for fuel and ignition control.
                          I have seen the huge potential both in torque and fuel efficincy with this fuel, and will explore it furter now on my first turboengine, the Smart.
                          On the MB190E, I managed to reach the same fuel consumption in 110 km/h lean burning E85, as the car uses on pure gasoline.
                          If you count on that is corresponds to a FE-increase by some 27%, considering that the E75 (this was a test in wintertime in Sweden where some idiots have decided to mix in more gasoline wintertime despite that its not needed at all), have about 27% less energy content than std gasoline (with 5% ethanol nowadays).
                          Modification on that car was some 2.5 mm milled off CH to increase CR + advanced ignition as it is easy to achieve by simply turning the distributor on that engine.

                          On the AMGC36, I got down my FE from std fuelconsumption on gasoline, 1,2 l/ 10 km to 1.3 l/ 10 km on E85 (= FE 23% down) by only running as lean as possibly on highway cruising (this means about AFR 20 or leaner, my broadband lambda cant report leaner than AFR 20), but with std igniton so far. There is an issue with my piggy-back system making it impossible currently to advance the igniton at all, which is limiting the FE. Anyway, I managed to improve the FE with as much as 23% only by running lean.

                          (You can test and calculate yourself and compare the energy-consumption between different fuels and fuelconsumptions here:
                          http://etanol.nu/forbrukning.php the homepage is mainly in swedish even if we have an international section, but hey we have google translate nowadays, so it shouldnt be of any problem. I can help in translating too if anyone have any particular questions about ethanol in gasoline cars.)

                          The engine is running as usual otherwise, and I have full access to all my 285 Hp, anytime I want them ;-)
                          My piggyback ECU is only then switching to stoichiometric and finally fat mixture, during those moments.

                          My plans for the Smart is now first to increase the CR as much as possible, step 2 is to adapt some kind of piggy-back so I can lean out the mixture during part load, but this time also in combination with advanced ignition timing.
                          Step 3 would be to increase the power from my std 54 Hp to something more, exciting...
                          Here I will be quite moderate, but after a while, the horns will probably grow out on me,and I will boost more than safely for the engine...
                          Then step 4 might be a milled block in the end....;-)

                          Tomorrow will be measurment day with my daughters plastic clay...

                          Comment


                          • #14
                            Re: How much can be milled off the Cylinder head?

                            Great post ES. Thanks. It lets me know you really are aware of what you are doing. And that you've had some prior success.
                            So, back to the original question....
                            It might be worthwhile checking the deck thickness - make that thicknesses - over the sealing face with ultrasonics. Ultrasonics are used in the checking of hull thickness (early corrosion warning) on ships. NDT companies have the kit and ability, so if there's one near you, turning up with your CH for an hour should give you a better idea of how far is still safe re milling. If going this route you may need to know the grade of alloy - bu only if they cannot access a part of the CH that can also be physically measured, as calibration can be performed from there.
                            Keep us posted on developments - I'm very interested in how you progress with this. I'm also very interested in HCCI. If you can point me to any recent info you may be aware of, it would be much appreciated!

                            Comment


                            • #15
                              Re: How much can be milled off the Cylinder head?

                              One thing to consider is that Turbo engines run a low compression ratio for a reason. That is that you are already cramming more air and fuel into the cylinders than you would on a normally aspirated engine. So if you increase the compression ratio you will only be able to run lower boost pressure!!
                              I would say do not alter the compression ratio at all. Just get it 'chipped'!
                              Good Luck

                              Comment

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