twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 I'm not at all sure James - but it would certainly make sense - if the fuel is "squirted" directly into the recessed bowl and it is confined for a fast, clean burn then the bowled piston shape would indeed be linked to the "Direct Injection" aspect of the engine rather than the "Turbo" part. Which, would answer all the questions on piston choice... keep 'em the same. Good catch sir! I found a video which explains a little about direct injection... granted its for "Gasoline"... and its very American-orientated (the engines are vee-shaped) - but it does go some way to explain the difference - you can view it on YouTube Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 Western/Simon/James - good shout, that's a major part of the puzzle solved then! Quote Link to comment Share on other sites More sharing options...
Simon Smith Posted February 10, 2013 Share Posted February 10, 2013 Actually a quick calculation based mainly on guesswork, I make the compression ratio 200:1 I don't think the starter would even turn it over! Direct and indirect injection on diesels isn't really like that video at all. I supose the direct injection is similar, but on an indirect injection diesel the fuel is injected into a "pre combustion chamber" which is a spherical chamber in the cylinder head which also has the glow plug in it, this chamber has a small opening which "squirts" the exploding mixture at the top of the piston where those grooves spread the flame over the complete surface area of the piston. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 200:1, goodness! No, I'm quite happy with 19:1 thank you very much. I'm embarrassed to say that diesel is still something of a dark-art to me, I learned everything I know on petrol engines. It is, in part, for this reason that I want to build a diesel engine and why I'm so keen on advice from this forum. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 10, 2013 Share Posted February 10, 2013 cranks from all the 2.5 diesels are dimensonally identical upto the 300tdi. I know a 200tdi with a 2.5na crank in, it runs fine Quote Link to comment Share on other sites More sharing options...
western Posted February 10, 2013 Share Posted February 10, 2013 TD engine compression ratio is 21:1 200Tdi is 19.5:1 +0.5:1 looking at the parts info for both engines the crank is common http://www.brit-car.co.uk/product.php?xProd=84626 as is the camshaft [my 200 has a 2.5n/a diesel cam, as my original cam nose bot chewed up some years ago. Quote Link to comment Share on other sites More sharing options...
Simon Smith Posted February 10, 2013 Share Posted February 10, 2013 The reason for the different compression ratio is due to the size of the combustion chamber, nothing to do with the crank or rods. Simply the swept volume to unswept volume ratio. The swept volume is the same for all 2.5 ltr engines, petrol, diesel, turbo diesel or tdi. with Tdi head and TD pistons there is effectively no unswept volume apart from those vees in the piston and the piston-head clearance, hence the 200:1 compression ratio. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 Just checked my Defender parts manual and indeed you are correct sir (at least for the later 2.5 NA/Turbo engines): 2.5 NAD crankshaft = ETC8829 to (V)399927, ERR1181 from (V)399928 2.5 Turbo Diesel crankshaft = ETC8829 to (V) August 1989, ERR1181 from (V)August 1989 200TDi crankshaft = ERR1181 300TDi crankshaft = ERR2112 2.5 NAD camsaft = ETC7128 2.5 Turbo Diesel camshaft = ETC7128 200TDi camshaft = ETC7128 300TDi camshaft = ERR3547 Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 However, as Simon quite rightly says - now we know that the bowl in the piston is linked to the "direct injection" element rather than the forced induction and the volume of the recess creates the compression ration - there is no need to consider swapping crank, con rods or pistons between the different engines. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted February 10, 2013 Author Share Posted February 10, 2013 So ladies and gents - looks like we have some updates based on your shared knowledge: (starting at the bottom of the engine for a change...) The sump can stay the same (no design features are specific to the turbo element of the engine) The block can stay the same (no design features are specific to the turbo element of the engine) The crank can stay the same (shared with 2.5NAD and no design features are specific to the turbo element of the engine) The main bearings can stay the same (no design features are specific to the turbo element of the engine) The con rods can stay the same (no design features are specific to the turbo element of the engine) The pistons can almost certainly stay the same (no design features are specific to the turbo element of the engine - only the "Di" part) as the NA or 19j Turbo pistons can not be used. The cam can stay the same (shared with 2.5NAD and no design features are linked to the turbo element of the engine) Quote Link to comment Share on other sites More sharing options...
NickMc Posted February 10, 2013 Share Posted February 10, 2013 I would use the Tdi pistons over the TD ones all day long. As a few have said the shape in the top of the piston has to do with it being DI. Quote Link to comment Share on other sites More sharing options...
western Posted February 10, 2013 Share Posted February 10, 2013 Don't think TD pistons would work with a Tdi head & direct injector, there wouldn't be any combustion chamber for the fuel to burn in. a straight Tdi withoput the turbo would be the quick & easy way to go as Glencoyne have found. Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted February 10, 2013 Share Posted February 10, 2013 Just checked my Defender parts manual and indeed you are correct sir (at least for the later 2.5 NA/Turbo engines): 2.5 NAD crankshaft = ETC8829 to (V)399927, ERR1181 from (V)399928 2.5 Turbo Diesel crankshaft = ETC8829 to (V) August 1989, ERR1181 from (V)August 1989 200TDi crankshaft = ERR1181 300TDi crankshaft = ERR2112 Interesting, I wonder what difference there are between the 300tdi and earlier cranks, the only differences I've seen are the key ways in the front are different between the two. I wonder if they are the same casting just machined a little differently, I have photographed 2 300 tdi cranks here one earlier than the other, notice they both have the same casting numbers (in different places) but the one on the left has the British leyland flying asshole/plug hole of doom symbol. Bl went out in 1986, if the casting for the 300 crank was new why would an engine designed much later have their symbol cast into it? Unless they all use the same casting and well into the 90's they were still using the bl casting dies? Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted February 10, 2013 Share Posted February 10, 2013 Yep, the piston bowl relates to the combustion type (DI vs IDI) and injector position / spray pattern. If you went all-out for reliability you'd run it naturally aspirated. You could increase the compression ratio by skimming the head for better efficiency since you're not running "external compression" with any boost - up to 21:1 would be fine. I'd set the fuelling level by using an EGT gauge to ensure it remains reliable. Otherwise, build it up in a neat and tidy way with quality components and you should see 150,000 miles without opening the engine again. Quote Link to comment Share on other sites More sharing options...
western Posted February 10, 2013 Share Posted February 10, 2013 300tdi casts were sold of to brazil hence the TGV diesel based on 300tdi, LR bought in cranks as they no longer had the means to make them. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 10, 2013 Share Posted February 10, 2013 Interesting, I wonder what difference there are between the 300tdi and earlier cranks, the only differences I've seen are the key ways in the front are different between the two. I wonder if they are the same casting just machined a little differently, I have photographed 2 300 tdi cranks here one earlier than the other, notice they both have the same casting numbers (in different places) but the one on the left has the British leyland flying asshole/plug hole of doom symbol. Bl went out in 1986, if the casting for the 300 crank was new why would an engine designed much later have their symbol cast into it? Unless they all use the same casting and well into the 90's they were still using the bl casting dies? Different measurments to fit the different blocks, the 300 also drives the oil pump off the crank, the 200 and earlier drive the oil pump via the skew gear, off the cam shaft. Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted February 10, 2013 Share Posted February 10, 2013 Skimming the head won't gain you any CR increase, the head surface is totally flat. There is very little room to deck the block either, only about 60 thou of squish from memory. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 10, 2013 Share Posted February 10, 2013 Skimming the head won't gain you any CR increase, the head surface is totally flat. There is very little room to deck the block either, only about 60 thou of squish from memory. Skimming the head will alter the compression ratio but the difference is so slight you dont worry about it. You can alter the deck height on the block but again the work involved and increase in compression wont be worth worrying about. Compression ratio gets altered by altering the size and shape of the combustion chamber. Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted February 10, 2013 Share Posted February 10, 2013 Skimming the head will alter the compression ratio but the difference is so slight you dont worry about it. ??????? The only reductions in volume of the cylinder you'll gain are that the tips of the injector and glow plug will be further exposed by a few thou. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted February 10, 2013 Share Posted February 10, 2013 Oh aye. Senior moment there... Decking the block would raise the CR (which is lower than it otherwise would be by design due to the anticipated turbocharging) - but you're probably right, likely to be not worth the effort. Make sure that the inlet side is clean and well flowed of course, match the ports to the manifolds and take any flash off the castings, it's more critical if you're not pushing the air in with a turbo. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 10, 2013 Share Posted February 10, 2013 ??????? The only reductions in volume of the cylinder you'll gain are that the tips of the injector and glow plug will be further exposed by a few thou. The valves sit under the surface buy about 1mm... Hence I skim them without taking the valves out. Quote Link to comment Share on other sites More sharing options...
Maverik Posted February 11, 2013 Share Posted February 11, 2013 With regard to Cranks, I was reading up on the 2.8 TGV the other day and evidently one of the upgrades on the 2.8 engine was that the crank was forged as apposed to cast makeing them slightly superior in quality. Not quite a "standard" LR part but have you taken into consideration any TGV bits? Mav Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 11, 2013 Share Posted February 11, 2013 With regard to Cranks, I was reading up on the 2.8 TGV the other day and evidently one of the upgrades on the 2.8 engine was that the crank was forged as apposed to cast makeing them slightly superior in quality.Not quite a "standard" LR part but have you taken into consideration any TGV bits? Mav the throw on the tgv's crank is different iirc so you'd need rods and probably the pistons if if the tgv has a different size gudgion pin. Quote Link to comment Share on other sites More sharing options...
rick Posted February 15, 2013 Share Posted February 15, 2013 the throw on the tgv's crank is different iirc so you'd need rods and probably the pistons if if the tgv has a different size gudgion pin. Yep, and I wouldn't use 2.8 pistons as the bore size is bigger by about 2.5mm. I wouldn't trust the core thickness of a 300Tdi block to go out that far..... Quote Link to comment Share on other sites More sharing options...
Yostumpy Posted February 17, 2013 Share Posted February 17, 2013 So, in a 110 say, which would be more economical? a 200 tdi or a 200di Quote Link to comment Share on other sites More sharing options...
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