Just recently I've read about a lot of people reading compressor maps with dyno plots and using them to try and determine spool-up time. this may seem a reasonable assumption to make and may be used as a very rough guide, but that's all. Here's something i've been quite involved in for the past few months, which may dispel a few myths and hopefully enlighten people a little 2 turbochargers on the same engine can give identical, near identical or similar torque curves. You may think that it would be a reasonable assumption that these turbo's may be very similar to drive, but this is not always the case. below is an example of 2 turbo's on a diesel engine - rpm on the x axis and torque on the y axis note the curves are nigh-on identical However, i then subjected both to a 2000rpm load step response - the engine was run at 2000rpm at 10% of full-load torque and the values allowed to stabilise. Then a suddel load step was input and full-load torque was requested, and the response to that was measured. the graph below shows the response - x axis is time and the y axis is torque note the massive difference in torque response between the turbos. this would mean that when cruising at a constant speed the 2 turbos would perform near same, but when running at low load and putting your foot flat on the accelerator one turbo would outperform the other. there are many reasons for this, pressure differentials across turbine and compressor, turbine and compressor inertias etc etc which are too many to list. but hopefully this will highlight this characteristic of turbocharged engines and we'll all be a bit wiser feel free to discuss tt
ok hands up who had to read that more than once! how can we hope as amatuer tuners to get this info about turbo's? Suppose we can only copy people who have done well with particular setups.
transient response (in laymans terms) is this similar to a similar term used in audio, e.g. the transient response of bass drivers. A responsive unit (usually with a light cone mass) can change bass tones fast, changing from frequency to frequency quickly and without sounding confused or sticking to the first note for too long. So, in regards to turbo's, a highly responsive turbo can spool up fast (say with a lighter mass of fan) giving superior low down grunt before the slower responding turbo spools up? Is that part of the correct theory for what you posted above? Interesting stuff nonetheless.
transient basically means that the response varies with time. Very interesting though Similar in the results to some stuff that we were modelling using Simulink / matlab last semester - ie the settling time and response time could be easily influenced by identifying certain parameters - yet the steady state response was the same.
yep, you got the gist of it Tim, i wouldn't expect you to know this or be able to assess a turbocharger in this way, just be aware of it tt
Must be quite a few factors involved in this, inlet tract length & Volume, intercooler volume and flow rate etc Rob what are the best ways to improve throttle response then, in wordys eye can unnerstund loike
I can plaster the walls of your tent, and hook it up to electricity. Albeit, I cannot guarantee the work.
