philak Posted January 17, 2009 Share Posted January 17, 2009 Quick question and sorry its a bit basic but it's stuck in my head and i can't find an answer anywhere (and don't have an engine to look at right now). I've read the Haynes manual and it's no clearer to me. Exhaust gas drives turbine>spins shaft>spins compressor which then a: forces air from the intercooler into the intake manifold or b: forces air through the intercooler then into the exhaust manifold.(edit...meant intake) Is is a or b? I can find plenty of pics of turbochargers and plenty of intercoolers but no diagrams of how it all plumbs together. If the answer is "a" does the air input to the intercooler come direct from the air filter? If the answer is "b" doesn't all the extra piping and intercooler core create a lot of lag and drop of intake pressure? Cheers Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted January 17, 2009 Share Posted January 17, 2009 a). What would be the point of blowing air into the exhaust? input to the intercooler comes from the turbocharger. The turbocharger sucks air from the air filter and intake. 'inter' means 'between' and means a cooler between two entities. In this case it is the turbocharger and the engine, although it was originally meant to be the cooler between two superchargers. Either way it cools the inlet air. Quote Link to comment Share on other sites More sharing options...
crwoody Posted January 17, 2009 Share Posted January 17, 2009 Check out the link (a bit long) below. http://www.google.co.uk/imgres?imgurl=http...=image&cd=1 Quote Link to comment Share on other sites More sharing options...
TD5 power Posted January 17, 2009 Share Posted January 17, 2009 hi A) the turbo pushes the air through the intercooler into the engine. This cools the air making it more dense and therefore getting more oxygen into the cylinder, so more fuel can be added giving more power. i think there is a slight drop in pressure between the turbo output and the inlet manifold but not a lot. if there is lots of sharp bends and restrictions in the piping this may cause lag but i don't know how noticeable it would be. HTH matt edited because i didn,t read the question properly Quote Link to comment Share on other sites More sharing options...
philak Posted January 17, 2009 Author Share Posted January 17, 2009 Sorry Jim, that was a typo about the exhaust manifold. I meant intake. TD5 power.....thanks for the clarification and thanks to woody for the article. The diagram is just what i wanted and it shows the quite lenghy route the intake air travels. Quote Link to comment Share on other sites More sharing options...
gruntus Posted January 17, 2009 Share Posted January 17, 2009 Hi Philack, The turbo charger by design blows air into the induction manifold (forcing air into the sytem under pressure) which gives you a higher charge of air (forced induction) rather than drawing it in by vacuum as the piston travels down the bore. So, when the turbo has spun up and doing its work there is a constant positive "pressure" in the induction system so the air gets rammed into the cylinder as soon as the induction valve opens. Now then if you have your head around the above think about the compressor side of the turbo and the exhaust side of the turbo you will notice that they are next to each other but both are seperated from one another but connected by a common shaft. As the exhaust blows out the exhaust ports the hot expanded gas blows past the fins of the exhaust side of the turbo which spins the same shaft that the induction compressor is attached to thus as the turbo spin faster a higher presure gets created on the induction side. With the above in mind its time to look at intercoolers. As the turbo is driven by hot gasses then this heat naturally transfers to the induction side and the turbo would usually run hot air into the induction side. To reduce the temperature of the forced air and get a denser charge of air into the cylinders, intercoolers are fitted "in line" to cool the air. Intercoolers are used to transfer the heat from the induction side and are really a cooling radiator. The cycle of air is this: normal air (at atmosphere)--> air filter--> turbo (pressure)--> intercooler (pressure)--> inlet manifold (pressure)--> cylinder/bore of engine (/suck/squeeze/bang/blow)--> exhaust manifold--> turbo (exhaust side spins turbo)--> exhaust--> atmosphere You could go into a lot of detail on cooling air etc but the above should get you by for now. Superchargers are the same basis as turbos only instead of the exhaust turning the shaft it usually has a mechanical drive to turn the turbine. This gives you a pressure in the induction cycle at all times however it uses energy from the engine to turn the shaft. Witha turbo you are getting something for nothing however older turbos werent very effective until the engine was revving above three thousand revs (hence the phrase turbo lag). Hope this helps. Grant Edited to add, as the system is under constant pressure (the air is ready to go in the bores as soon as the valves open) slight pressure drops across inetrcoolers etc may be negligable Quote Link to comment Share on other sites More sharing options...
philak Posted January 17, 2009 Author Share Posted January 17, 2009 Grant, its the constant pressure of the system that i was missing . I was picturing the turbo working directly off the exhaust ( a very short route) and thinking the inlet side should be as short as well for maximum efficiency ie to maintain boost generated by the compressor, but i was thinking of it in terms of on/off pulses instead i suppose. Therefore it seemed odd to have this relatively long route through the piping and intercooler. Having seen the pics and all the replies i'm getting it now. Cheers. Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 17, 2009 Share Posted January 17, 2009 The gas laws come into this, for those that can remember that far back to school. Pressure, temperature and volume are all interrelated (can't work out how to show the formula), so if pressure rises, as in a turbo, and volume can't rise, so temperature rises. This came to a head back in the days of racing production Escort Cosworths. There was an option to use the big turbo, supposedly for group A use, but with a standard intercooler it couldn't flow enough inlet charge, so the inlet temperature increased, and the bigger turbo cars were slower than those with the smaller one. In a petrol engine, for every I degree the inlet charge is dropped, you gain 1 bhp. Cheers David Quote Link to comment Share on other sites More sharing options...
gruntus Posted January 18, 2009 Share Posted January 18, 2009 Hi Philack, One thng to note now that you have your head around it is how the waste gate on a turbo works (there are smarter guys on this forum than me but I will try to explain simple style ). If the exhaust turbine was allowed to just keep spinning higher and higher at increasing revs you could actually create too much pressure on the induction side and have too much pressure getting into the engine. So what generally happens is as the turbo hits its optimum pressure (we will say 1.5 bar as an example) and the turbo starts to generate 1.5 bar pressure at 3000RPM it would continue to generate increasing pressure further up the rev range. So what we now have is a waste gate on the exhaust side of the turbo to keep the pressure at a particular setting. A waste gate is actually a little door that opens inside of the turbo that allows the excesssive exhaust pressure to bleed past the turbine and into the proper exhaust. This is controlled (on a 200TDi anyway) by having a waste gate actuator. How it works is as the induction side reaches optimum pressure and then starts to increase, this pressure is connected to the waste gate actuator which moves a small arm connected to the waste gate in the turbo which will then bleed some of the exhuast gas which in turn then lets the exhuast turbine spin at a set speed thus maintaing a constant steady speed and pressure (in this example from 3000RPM and at 1.5bar). All the below are example for illustration only!!! REVS__________1000rpm____2000rpm____3000rpm____4000rpm_____5000rpm____6000rpm (yeah I wished) Induct pressure__0.1bar_____0.9bar_______1.5bar______1.5bar_______1.5bar______1.5bar. Waste gate______closed_____closed_______closed_______open________open_______open (the wast gate wont be fully open just enough to allow exhaust turbo to maintain constant speed to produce 1.5bar) ________________________________(but ready to open) Dont allow dump valves etc to confuse you with regard to to waste gates there are a number of trick things that can be done which are very clever however in this case we are looking at a very basic tractor setup on a 200TDi engine. When you mentioned having a short airfilter--turbo--induction route this is actually what was fitted on the first TurboDiesel Land Rovers but due to this setup (no intercooler and hence a hot charge of air) there were very high temperature stresses which resulted in cracked pistons etc. The first intercooled Turbo Diesels (200TDi) are a good,realiable, basic engine to see all this working and due to the only electrical control being a start/stop fuel solenoid are favoured by some people for their simplicity (Im one of them being simple slightly myself ). Hope this helps. Cheers Grant Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted January 18, 2009 Share Posted January 18, 2009 Grant While there may be some heat transfer along the shaft of the turbo, the vast majority of the heat in the charge air comes from the compression of the air in the compressor itself. Think of the rise in temperature of a bicycle pump after inflating a tyre. As said further up the thread, you get more oxygen in the charge air the denser it is. So the colder the better. This also lowers the EGT as well. Quote Link to comment Share on other sites More sharing options...
philak Posted January 18, 2009 Author Share Posted January 18, 2009 Thanks for the extra info Grant. It's a fascinating subject to get into and interesting that the turbo engines appear so reliable .I'm guessing that devices like waste gates/actuators don't see a lot of servicing in many defenders and would therefore start going wrong , causing other engine problems as you describe. I've always thought of turbos in general as being somewhat fragile, probably stems back to the early F1 turbo days when the Renaults were lucky to finish races. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted January 18, 2009 Share Posted January 18, 2009 And the turbo BMWs were lucky to complete practice Brabham-BMWs using the 2002 block IIRC. Quote Link to comment Share on other sites More sharing options...
Briarston Posted January 18, 2009 Share Posted January 18, 2009 The gas laws come into this, for those that can remember that far back to school.Pressure, temperature and volume are all interrelated (can't work out how to show the formula), so if pressure rises, as in a turbo, and volume can't rise, so temperature rises. This came to a head back in the days of racing production Escort Cosworths. There was an option to use the big turbo, supposedly for group A use, but with a standard intercooler it couldn't flow enough inlet charge, so the inlet temperature increased, and the bigger turbo cars were slower than those with the smaller one. In a petrol engine, for every I degree the inlet charge is dropped, you gain 1 bhp. Cheers David Boyle's Law P1,V1/T1 = P2,V2/T2 where P=pressure, V=volume, T=temperature (I think.Yes it was a long time ago!) Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 18, 2009 Share Posted January 18, 2009 And the turbo BMWs were lucky to complete practice Brabham-BMWs using the 2002 block IIRC. Used and weathered 1502 blocks. They needed to 1500 cc, and they got over 1300bhp in qualifying. Cheers David Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 18, 2009 Share Posted January 18, 2009 Boyle's Law P1,V1/T1 = P2,V2/T2 where P=pressure, V=volume, T=temperature (I think.Yes it was a long time ago!) Exactly. Couldn't see a relevance for it when at school, but as soon as we started tuning turbos, it all made sense. Cheers David Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 18, 2009 Share Posted January 18, 2009 I've always thought of turbos in general as being somewhat fragile, probably stems back to the early F1 turbo days when the Renaults were lucky to finish races. It was usually the engines that expired rather than the turbos, although if you imagine a high speed trubo suddenyly having the air flow stopped by shutting the throttle, there were some wierd forces in action that could shatter blades. Early turbos ran in plain bearings supported only by the oil, and were only air cooled. Later turbos are water cooled and have better bearing technology. Cheers David Quote Link to comment Share on other sites More sharing options...
bluespanner Posted January 18, 2009 Share Posted January 18, 2009 Used and weathered 1502 blocks. They needed to 1500 cc, and they got over 1300bhp in qualifying.Cheers David I read about that in an old EVO mag. Apparently they used 100k mile blocks, as these would have all the stresses worked out. or something. Roly Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 18, 2009 Share Posted January 18, 2009 I read about that in an old EVO mag. Apparently they used 100k mile blocks, as these would have all the stresses worked out. or something.Roly Yup, old blocks that were then left out in the rain and occasionally peed on. Cheers David Quote Link to comment Share on other sites More sharing options...
howard14 Posted January 18, 2009 Share Posted January 18, 2009 Used and weathered 1502 blocks. They needed to 1500 cc, and they got over 1300bhp in qualifying.Cheers David Hi David. When you say 1300 bhp, do you mean 300 bhp! If so thats very good for 1.5Lt. On the other hand 1300 would be off the richter scale, but well worth having. Best regards. Howard. Isle of Skye. 2x300TdiDef.... Quote Link to comment Share on other sites More sharing options...
western Posted January 18, 2009 Share Posted January 18, 2009 Boyle's Law P1,V1/T1 = P2,V2/T2 where P=pressure, V=volume, T=temperature (I think.Yes it was a long time ago!) http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html Quote Link to comment Share on other sites More sharing options...
gruntus Posted January 19, 2009 Share Posted January 19, 2009 GrantWhile there may be some heat transfer along the shaft of the turbo, the vast majority of the heat in the charge air comes from the compression of the air in the compressor itself. Think of the rise in temperature of a bicycle pump after inflating a tyre. As said further up the thread, you get more oxygen in the charge air the denser it is. So the colder the better. This also lowers the EGT as well. Hi Rover, I'm aware of air heating under compression (essentially its what makes the diesel cycle) and saw the intercooler as just a means of removing the heat from the air charge really. I hadnt really attributed much of the the heat from the turbo compressing the air as i didnt think the pressure created by the turbo was all that great in comparison to say a normal garage air compressor (I have worked on two stage compressors before and the pipe work and heads are exceedingly hot!). Effectively I had attributed most of the heat generated in the charge by the radiant heat in the turbo (when you consider EGT) so I stand quietly corrected sir! All the best. Cheers G Quote Link to comment Share on other sites More sharing options...
rallycinq Posted January 19, 2009 Share Posted January 19, 2009 Hi David. When you say 1300 bhp, do you mean 300 bhp! If so thats very good for 1.5Lt. On the other hand 1300 would be off the richter scale, but well worth having. Best regards. Howard. Isle of Skye. 2x300TdiDef.... I meant 1300BHP. Akin to a grenade with the pin pulled out. Good for one out lap, one quali, and one in lap, then place the melted ruin in the bin. Cheers PD Quote Link to comment Share on other sites More sharing options...
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