rayaapp2 Posted May 25, 2005 Share Posted May 25, 2005 rayaapp2' date=' if you read my post a little closer, it says to use a VATN turbo LIKE the ones used on the Ford Power Stroke. They come in all different sizes...A properly sized VATN turbo will get 8-10 psi by 1500-1800rpm. The Cat dual turbo setup is for super-high boost, not for quick response. Some Detroit Diesels are like this too, with the turbo boost going into a roots supercharger. Because the Detroit is a 2 stroke, it requires boost to even run.[/quote'] Are you talking about the variable speed turbos... The only truck I have seen those on are the Chevy Duramax 6.6 LLY motors that appeared in 2003. The Powerstrokes still use the old conventional style wastegate? I have contacted two outside sources one of which is a buddy I have a Gale Banks Engineering. So one way or another we'll found out if I'm wrong. This is what I was taught. And you make a good argument. But some things just don't make sense to me yet. So far everyone I talk to thinks I'm right, but can't get me a straight answer why... Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted May 25, 2005 Share Posted May 25, 2005 So basically what this is coming down to is either go single turbo' date=' independant twin turbo, or leave to turbo out of the picture all together (at least until more R&D can be done) Personally I REALLY like the idea of twin turbos on a diesel, aka totally unique, even if it has to be independant. The whole reason I wanted to do the sequential twin turbo was so I could use the bolt on exhaust manfold but if it's going to be a major pain and I have to use a custom manifold anyways then I might as well run independant for simplicity. On a side note, would it be wise to run an intercooler on a turbocharged diesel? I always thought that the added heat would help combustion, but now that I think about it, too much heat is also bad.[/quote'] Just thought I'd chirp in and bring up BMWs rather good line of straight 6 turbo diesels. The new 535d is a 3l with sequential turbos like you're considering, might be worth looking in to the for turbo specs. http://www.pistonheads.com/roadtests/bmw/BMW535d.htm As for intercoolers, you can get BM diesels with or without. The cars with intercoolers all make higher power so I guess it's still all down to how much air you can cram into a block regardless of the fuel. BTW I've got a 325TDS Touring (Station Wagon to you Americans), the engine is fantastic for a diesel, revs to over 5k (oooo ) and it vey smooth. Only downside is that boost is a bit slow to come on. The thought of dropping one of these engines in to a Z has occurred to me but I'll leave that one on the back burner for a while I think! Sounds like a good project though, keep us posted! Cheers, Rob Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 25, 2005 Author Share Posted May 25, 2005 Just thought I'd chirp in and bring up BMWs rather good line of straight 6 turbo diesels. The new 535d is a 3l with sequential turbos like you're considering' date=' might be worth looking in to the for turbo specs. http://www.pistonheads.com/roadtests/bmw/BMW535d.htm[/quote'] Thanks for the info, I guess I'll have to take a close look at those! I would be more willing to swap in a BMW motor if it wasn't for two distict reasons, Price! I know the motors themselves aren't too bad but try getting parts to rebuild one! I had this problem when looking for parts to rebuild their V12s. and the second being Originality, meaning keeping with Nissan/Datsun parts. I never thought I'd be saying that because I dont usually follow that group, but there's just something about starting up a turbo diesel datsun and bragging about it being all Nissan that's just so appealing. Thanks again for the info. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted May 25, 2005 Share Posted May 25, 2005 So we have an engine that redlines at half the gas motor's. The intake is built slightly bigger than the gas motors. It at least has the potential to flow the same, but the engine doesn't rev as fast. Just something to think about... Ever hook a vacuum guage to a diesel engine? The diesel engine has to flow twice as much as the gas motor. I don't have it completely figured out yet, but here is what I do have. It has to do with the volumetric difference created by the combustion chamber. Because it can squish 20:1 vs 9:1 (approx number) This is why the cam can be so small. Even at idle the diesel flows approx twice as the gas counterpart. Let's say the engine has to take in 20 cc of air as a figurative number to be squished in order to get the correct air to fuel ratio. The gas engine only has to take in 9cc of air. That's less than half the amount of the diesel. The cam is built around this fact. The gas engine doesn't create the same difference in pressure the diesel engine does. I know there are some holes in this you guys will try and pick at. I know from experience that a diesel will flow more volume per rpm than a gas engine. I just am trying to figure out why and explain. All you really have to do is put a vacuum guage on and check it for yourself. I am going to talk with one of my buddies about this tonight and come up with a clear explanation. thanks also Another thing to think about... Diesels make torque and little HP. Air velocity has a HUGE impact on making torque... Evidence of a larger difference in pressure... Quote Link to comment Share on other sites More sharing options...
Guest SS-Z31 Posted May 25, 2005 Share Posted May 25, 2005 I'd also try to check out some of the VW TDI forums... Some people have taken older golfs and swapped the TDI into them... could give you some info into a gasoline -> Diesel swap even though its not a Datsun. When I used to have my 86 golf I was looking into doing this in the intrest of gas mileage ... although the stock 8v was pretty good on gas. If I can find the forums I was looking on back then I'll post em up. Also, YES diesel's flow a LOT more air than a gas engine and as far as i've read about the VW's you can't really use a manifold from a gas engine unless it was cast. I had posted up about putting a tubular header on a old N/A diesel jetta and I found out that because of the way the exhaust resonates through the manifold and out the exhaust it would crack within a month or two... Since you'd be turbo'd anyway this isn't relevant unless you use a tubular turbo manifold. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 25, 2005 Share Posted May 25, 2005 Diesel fuel has more energy per unit than gas. You have to have much higher compression to burn it though. That's why diesels run 20:1 compression, and that's why they make so much torque. Given two engines that are exactly the same size, say 2.0L, there is NO reason that the cylinder on the diesel engine will fit more air into it than the 2.0L gas engine. Hence the designation of 2.0L. Given a volume of 2 liters, you can then tune the engine to burn the fuel you want. If you're burning gas, you need 9:1 compression. If you're burning diesel, you need 20:1. That doesn't change the volume of the cylinder, only the relationship between the cylinder volume and the combustion chamber volume. Again with the cam example let's compare a stock L28 with a Rebello or a Sunbelt L28. You'll get more vacuum (a lot more) with a smaller cam. This is why you see guys with HUGE cams sometimes buying vacuum canisters or vacuum pumps. It's not because their engine doesn't flow as much air, it's because there is more overlap in the cam, so there is no vacuum at low rpms. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 25, 2005 Author Share Posted May 25, 2005 Well, I've been playing with the numbers and talking with the guys on a couple of diesel forums and here's where I'm at. The stock LD28 engine has a comp ratio of 22:1 and this is normal for a N/A diesel but to turbo charge it I need to reduce the ratio. I think that I can do that by changing out the pistons, The L24 and L26 pistons with a .060 overbore are the correct size for a drop in replacement. Problem is that I need to find the pin height and the rod length of the LD28 before I can set the rest of the specs. I also dont know what type of piston pin the LD28 has. I'm starting to think that going out and getting a Diesel Maxima manual would be very helpful. I'm not giving up on the sequential setup yet, I just need to do more research. I take it the Cat style turbo setup is totally out of the question due to the fact that I'd rather not overboost the engine, correct? and if SS-Z31 is correct then this might be totally out of the question because if the cat style setup is out of the question, then some sort of custom manifold will have to be made. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 25, 2005 Share Posted May 25, 2005 Gas pistons won't work in a diesel, this I'm SURE of. Way too much compression for gas pistons. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 25, 2005 Author Share Posted May 25, 2005 Gas pistons won't work in a diesel, this I'm SURE of. Way too much compression for gas pistons. Exactly as I suspected, unfortunately. So what can I do to the engine to reduce the compression ratio? Quote Link to comment Share on other sites More sharing options...
Guest DoTheDrew888 Posted May 26, 2005 Share Posted May 26, 2005 Larger head gasket. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 26, 2005 Author Share Posted May 26, 2005 Larger head gasket. If my guess is correct using the HKS 2mm will drop the compression into the 18.5:1 area which is apparently right where I want it. Now the question is if the HKS gasket can take it? My impression was that this is a racing gasket which would lead me to lean twards yes, however I dont know of any other solution so I guess I'm stuck with it. That is unless one of you have a different solution. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 26, 2005 Share Posted May 26, 2005 You could port the combustion chambers, just open them up with a die grinder and a burr, and cc them to whatever compression ratio you need. It would be a PITA, but I agree with you that the headgasket might be an issue at 20:1 + boost. Quote Link to comment Share on other sites More sharing options...
Guest kellysguy Posted May 26, 2005 Share Posted May 26, 2005 You don't need different pistions or ratio as turbo diesel is only .5 less. Diesels take in more air at lower RPMs because w/ no T/B, it's "wide open" all the time. It has to have max VE at every RPM level to achieve the high comp ratios. 4600 RPM is redline for power only, these motors will spin higher than that, especially w/ more fuel and boost. Only big, industrial motors have half the RPM range, most automotive "conversion" are capable of same RPM's as gas counterparts. Don't take this the wrong way, but you need to get alot better grip on diesel engines before you do ANYTHING, as you don't have any of the fundamentals down yet. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 26, 2005 Author Share Posted May 26, 2005 Don't take this the wrong way, but you need to get alot better grip on diesel engines before you do ANYTHING, as you don't have any of the fundamentals down yet. That's why I'm asking these questions! I cant learn if I dont ask. I've got the basics but apparently I need to learn the middle stuff before I can go onto the specifics. All this arguing and bringing up what seem to be odd points has really got me starting to think about going back into my little gasoline powered corner. I just want to be different, If this wont work with my current skill set and I cant figure out what I need to know then I may just give up, but not quite yet. I have to finish this train of thought before I push it aside and move to something else. I still have a lot of bodywork to do before I get to my engine so I have a bit of time to learn. Perhaps you could provide some links to websites that can help me understand the principals and theory of diesel engines? Especially those that relate to turbocharged diesels. Quote Link to comment Share on other sites More sharing options...
cheftrd Posted May 26, 2005 Share Posted May 26, 2005 If I were you, I think I'd try the turbo on the long block as-is, if, and only if, you run a good intercooler and limit the boost and make sure you've enriched. Have you ever messed around with a diesel (and I do mean MESSED)? Pitch black oil that will be everywhere...stay out of there if you can. DAW Ditto. I would run the turbo on the motor, as is. Watch your EGT. As far as HKS head gaskets go, they seal combustion up to 1300hp in the RB26, which is right at the limit of the best head studs ARP can produce. However, holding pressure has less to do with the gasket and more to do with the clamp. In the event that you have to reduce compression, stay with the thin gasket and remove compression via enlarging the combustion chamber. Diesels try to pack the air into a very small area and raising the head COULD have disastorous results as far as power production. Quote Link to comment Share on other sites More sharing options...
zuhow Posted May 26, 2005 Share Posted May 26, 2005 jmortensen said: Diesel fuel has more energy per unit than gas. You have to have much higher compression to burn it though. That's why diesels run 20:1 compression, and that's why they make so much torque. This is wrong. Diesel has 19,200 BTU/lb and gasoline has 21,000 BTU/lb. A diesel engine will make less power for a given displacement than a gas engine of the same displacement. You need a higher compression ratio to get deisel to burn because you aren't using a spark, just the heat of compression of the air, in essence a diesel engine runs on detonation! The deisel makes so much torque because of the increased cylinder pressure. The torque an engine makes is directly related to the cylinder pressure, more pressure= more torque- that's why a turbo engine makes more torque than a NA engine. You should start with the LD block and all its parts. Dont even think of trying to use the L series aluminum cylinder head on an L series diesel, they wont last too long. I'm confused as to why you would want to do this. If you just want to tinker with something I can understand. Seems to me your gonna spend a lot of time, money, and effort on building yourself a headache. But don't let me dissuade you. I'd go down to the barnes and noble or borders and read the chapter (ch9) on internal combustion engines in "Mark's Standard Handbook for Mechanical Engineers" the book is pricey (like $150) and will be largely useless to buy, so just go read the chapter. Good luck! keep us posted on how it works out for you! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 26, 2005 Share Posted May 26, 2005 This is wrong. Diesel has 19' date='200 BTU/lb and gasoline has 21,000 BTU/lb. A diesel engine will make less power for a given displacement than a gas engine of the same displacement. You need a higher compression ratio to get deisel to burn because you aren't using a spark, just the heat of compression of the air, in essence a diesel engine runs on detonation![/quote'] Not according to what I've read. How do you account for the big increase in gas mileage on diesels if the fuel doesn't have more power per unit? Here's some backup: http://www.absoluteastronomy.com/encyclopedia/d/di/diesel.htm and the meaningful quote: Diesel contains approximately 18% more energy per unit of volume than gasoline, which along with the greater efficiency of diesel engines contributes to fuel economy (distance traveled per volume of fuel consumed). As to the diesel running higher compression, I still believe the compression is necessary, and if you tried to run a gas engine with gas compression on diesel fuel it won't burn. The compression is needed to burn the fuel. I'm confused as to why you would want to do this. If you just want to tinker with something I can understand. Seems to me your gonna spend a lot of time, money, and effort on building yourself a headache. But don't let me dissuade you. Me too! Even with a lot of boost it still isn't going to be "fast". After all this hassle it might make it back to stock hp levels. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 26, 2005 Author Share Posted May 26, 2005 My main reason for doing this is because I want to run something that no one has done before. I just want my car to be unique, I'm sure some of you can understand that. I started this line of questions to see if this was possible and if it was something that I'd like to do. I'm always hearing about huge horsepower gains from diesel and when I found out that you can bolt one into the Zcars I said to myself Why not? But now that I know the truth I'm not so enthusiastic anymore. Like I said before I may just run gas because from what I've heard so far, its easier. and probably cheaper too. Quote Link to comment Share on other sites More sharing options...
zuhow Posted May 26, 2005 Share Posted May 26, 2005 jmortensen: UNITS my friend, units. that source quotes per gallon (volume) what matters is mass (per pound)., some data: diesel #1 19,240 BTU/lbm 133,332 BTU/gal specific gravity (weight relative to an equal volume of water) 0.876 gasoline 20,260 BTU/lbm 116,485BTU/gal spec grav 0.68-.74 so while it's true a gallon of diesel has more energy than a gallon of gas, it doesnt matter. what matters is how much energy you get from combining it with oxygen (air) and that take place on a per mass basis (actually on a molar basis- so many atoms fuel to so many atoms O2). Diesel is just denser. if you go by a per volume basis you would believe that diesel has more energy than acetylene, but if you've ever used a blow torch (and I'm sure you have) you can clearly see it's not the case. acetylene is a lot less dense than diesel (because it's a gas) but it burns like a mother#$^*& Beware power is not the same as effiency. Yes a diesel engine is more effiecient, but less powerful. The diesel is more effiecient because of the higher pressures involved. the effieciency of any internal combustion engine (either spark ignition or compression ignition ,ie diesel) is directly related to the compression ratio, higher compression ratio= more efficient. compare an L28 to an LD28 land you'll see what I mean LD28 ~90Hp and ~150 lb-ft (source: http://retro.co.za/lr/tech/engines.html) L28 ~150hp and ~160 lb-ft L28T ~180hp and ~200 lb-ft (source: http://zhome.com/History/zcarperf.html) we're saying the same thing on the compression issue, I think. I love this site! diesels make torque, not power Chewievette. Whens the last time you saw a dump truck tear *** away from a steet light? They just pull hard and never stop! Quote Link to comment Share on other sites More sharing options...
Guest SS-Z31 Posted May 26, 2005 Share Posted May 26, 2005 The heads are completely different too from what I remember. The diesel pistons actually go higher than the block deck and the heads have to accomodate for this. Diesel's use glow plugs not sparks (essentially a heated element that ensure's ignition) as well as the insane compression to ignite the mixture. I don't really know anything about the BTU's or VE of diesels because I didn't get that into my old VW's... I'm just speaking from what I remember reading on those forums. I still think you should read up on the TDI forums because those people are devoted to their diesels and there is a lot of good info to be read. If you're looking for horsepower don't get a diesel because there won't be any compared to gasoline. As has been said before diesel's are all about torque due to the high cylinder pressures they produce. Turbo diesels are pretty "easy" to produce crushing torque from but HP will still be missing, so you'll have all this grunt off the line then nothing. Look at the turbo diesel work trucks that you can buy chips for to increase the boost pressure... they get like 150lb-ft of torque from that (not sure how realistic this is but, it seems believable to me considering a GTi 1.8T can gain as much as 50hp and 80lb-ft of torque from a chip...) My jetta had like 54hp and 71lbs of torque and that thing was so damn slow, I was nervous driving it on the road because I couldn't get up to speed in time... Didn't weigh anything either. My golf cart had better acceleration but anyway... http://tdiclub.com/links/ has links to a few diesel sites.. not just VW's http://www.howstuffworks.com/diesel.htm also good! Quote Link to comment Share on other sites More sharing options...
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