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  1. enginead

    Capturing waste heat from diesel engine....

    What about thermo electric generation using peltier effect ceramics? Not sure how much power would be available but the concept is heating doped ceramics creates a current. Might be worth a look.
  2. enginead

    Supercharger bypass valve operation

    My experience on similar systems (Mini Cooper S) has shown that the bypass (operated on purely manifold vacuum with no active control) is continually variable so even at part load there is still some positive pressure effect from the S/C. On the Siemens system used on Mini this was compensated...
  3. enginead

    Diesel rev limit factors

    murpia, The combustion rate I referred to was the crank angle duration between 5% and 95% mass fraction burnt (measured using an incylinder pressure transducer). Essentially this crank angle duration stays more or less constant with a change in engine speed (hence speeds up or slows down in...
  4. enginead

    SULEV versus higher MPG

    SomptingGuy: Would it be good for emissions though?
  5. enginead

    Diesel rev limit factors

    I've measured combustion on a 2.0l DI diesel (fitted with an electroniuc Bosch distributer pump) and within it's preset constraints (max engine speed =4500rpm) the combustion rate scaled as a virtually linear function of engine speed if you removed some of the obvious conflicting factors (e.g...
  6. enginead

    SULEV versus higher MPG

    Facinating debate, it's worth the extra legislation just to get good threads like this:) Once we've got to the stage that the catalyst has to be working <1 min after start at normal ambient temps (LEV, LEVII, EU4) going any further is frankly rediculus. As it is catalyst heating for EU4 costs...
  7. enginead

    High Knock Sensor Output on 1 out of 4...

    There's no doubt the knock sensors will pick up things like valve train noise, piston slap (almost anything high frequency depending on the calibration). On a recent hot trip I had an engine let go at WOT (due to a miss build of the oil pick up) and subsequently looking at the recording there...
  8. enginead

    Exhaust Gas Recirculation

    Normally EGR on gasoline engines is introduced after the throttle at part load and thus is in addition to the air charge and thus doesn't displace any air. On an unthrottled diesel engine however it does displace fresh air ( in fact this is how it is usually controlled). It works as GregLocock...
  9. enginead

    I must have stumped Bosch - O2 question.

    The addition of water to the inlet shouldn't effect the lambda meter reading as it essentially measures free O2 not AFR (the lambda:AFR relationship changes depending on composition of the AFR components). As H2O is inert and provides no 'new' 02 to the system the lambda (rather than AFR)...
  10. enginead

    Question about emission test

    This is normally due to poor lambda biasing. The closed loop fuelling system is biased slightly rich to ensure that is no NOx breakthrough during closed loop operation. This is because the catalyst efficiency is much less sensitive on the rich side (HC & CO conversion) than on the lean side (NOx...
  11. enginead

    inlet swirl again?!?

    Swirl or turd I like it:) Swirl is important in engines (gasoline and diesel) as it (all else being equal) increases heat release rate and gets closer to constant volume combustion and thus (theoretically at least) increases thermal efficiency. However, it also increases heat transfer from the...
  12. enginead

    Reducing NOX emissions in gasoline engines.

    Bayislandsdiver, The chemistry and physics of NOx formation in internal combustion engines is well understood to be a rate controlled reaction (ie it never gets to equilibrium conditions) variable as a function of temperature and component availability (i.e. N, N2, O & O2). Although the...
  13. enginead

    Using O2 sensors to tune a running engine

    Is that the jingle of spurs I hear..... AFR is very important (particularly in a racing application)as the max power occurs rich of stoichiometric (lambda 0.9) and not at a fixed exhaust temperature (which is very much a factor of spark timing).
  14. enginead

    Using O2 sensors to tune a running engine

    Hi Andy, My point is that you can scale the linearisation curve of the switching sensor (it is done in ME7 as the whole closed loop fuelling control including rear trim is done in the lambda domain). The problem is, because of the relatively flat response either side of the switch point the...
  15. enginead

    Using O2 sensors to tune a running engine

    Andy, There is a linearisation curve for switching sensors (see Bosch Automotive Handbook) which does describe lambda as a function of voltage output. It's how post catalyst sensors are used as fuelling trim. In terms of the effect of temperature on the shape of the curve I'm pretty sure that...
  16. enginead

    Self Dampening Fuel Rails

    Fuel rail pressure oscillations can be a significant issue, particularly on returnless systems. A standard wave is set up by the injector closing and the inertia of the fuel being bounced back through the rail as a pressure wave. This pressure wave can then effect subsequent injections depending...
  17. enginead

    BMW Valvetronic and Audi FSI combined

    I think the BMW V12 is a homogenous only GDi rather than stratified so it doesn't attempt to use stratification as a means of reducing pumping loop work. I'll have to check if I'm correct about it being homogeneous only though.
  18. enginead

    Using O2 sensors to tune a running engine

    Victorymotorsports, The volt meter is essentially the same as an ADC but you can record or view an ADC input on a computer and thus look at it later and also sample at a higher rate than a volt meter may update at. The HT reference is High Tension as in 10,000V through the HT leads between the...
  19. enginead

    Using O2 sensors to tune a running engine

    One problem you may find with a switching sensor is the resolution (particularly on the rich side) is relatively poor. At lambda 1 it will read ~0.45V but lambda 0.7 (close to the rich limit of combustion) it only reads ~0.9V and as you mention the response isn't linear. In terms of precision...
  20. enginead

    BMW Valvetronic and Audi FSI combined

    The two things are different ways of trying to get the same effect, ie. reduce the pumping losses during the inlet stroke. At part load Valvetronic works by only opening the inlet valves enough to draw the desired charge without having to pull down the whole inlet manifold (in a normal throttle...

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