Guest eric-z Posted November 7, 2002 Share Posted November 7, 2002 what do you all think about this Idea.... turbo L28 block from a zx crank from a L24(are crank journals the same size?) connecting rods from a L24 flat top pistons from the zx now what I assume would happen with this is that the since the stroke is shorter on the L24 then when it reaches TDC it won't be all the way at the top of the cylinder so it would give a larger combustion chamber, droping down compression, and allowing for more turbo boost. not to mention a little bit of a higher rev. I haven't really heard of this being done so there is probably something wrong with it, just wondering what it was. eric Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 7, 2002 Share Posted November 7, 2002 actually if I have my math correct then you would only be getting 28.7cc larger combustion chamber in each cylinder.... would that be enough to make a diffrence? eric Quote Link to comment Share on other sites More sharing options...
David K Posted November 7, 2002 Share Posted November 7, 2002 8.05:1 Quote Link to comment Share on other sites More sharing options...
Guest Ian turbo240 Posted November 7, 2002 Share Posted November 7, 2002 I have often wondered about building an L28 bore/L24 stroke turbo engine. The only advantage is you could use a long rod for good rod/stroke ratio. Depending on the valvetrain, you could also rev the engine to 7500+. It would definately be interesting. I think that the c/r would be very low with the stock L24 rods and L28 pistons. I don't have the #'s right now, but I'll work it out. I'll assume a P series head. Ian Quote Link to comment Share on other sites More sharing options...
Guest Ian turbo240 Posted November 7, 2002 Share Posted November 7, 2002 Well, David is right. The c/r would be about 8.1:1. That would be fine for a turbo setup. Ian Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 7, 2002 Share Posted November 7, 2002 why is it that that CR is higher than the stock turbo zx? Quote Link to comment Share on other sites More sharing options...
DavD3 Posted November 7, 2002 Share Posted November 7, 2002 Keep in mind that in such combo your L28 engine will have 2569cc. Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 7, 2002 Share Posted November 7, 2002 I did realize that the engine would drop to 2569cc but wouldn't the ability to run more boost and higher redline be a better deal than having the extra cubic inches. eric (still wondering why there is a higher CR than the stock turbo zx, if anyone could tell me that would be awesome) Quote Link to comment Share on other sites More sharing options...
Guest Ian turbo240 Posted November 8, 2002 Share Posted November 8, 2002 The main reason for the higher c/r is the flattop pistons. You have significantly reduced the combustion chamber volume as opposed to the dish pistons stock in the L28ET. Keep in mind that the stock flattops are not designed for a turbo application. Turbo pistons generally have thinner rings spacer further apart for strength in the ring lands. You may have problems with the stock flattops if you use them with a turbo setup. Ian Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 8, 2002 Share Posted November 8, 2002 well what if I used the stock turbo pistons. I knew the NA zx had flat tops but I guess I just assumed they were the same. eric Quote Link to comment Share on other sites More sharing options...
speeder Posted November 8, 2002 Share Posted November 8, 2002 Looks as if you will have to have custom pistons made for this engine due to the reduced deck height caused by the shorter stroke (79 - 73.7mm). The lengthened rods 130.4 - 133mm)won't make up enough of the difference. I get an additional -2.7mm deck height. Might as well get the correct dish along with the correct pin height, and make your new pistons forged, please. I have thought about building one of these things, also. Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted November 8, 2002 Share Posted November 8, 2002 Dodge 2.2 turbo pistons work in this application if you overbore and clean off the tops of the pistons a little to get 0 deck. A friend of mine has this setup on the bench right now, waiting on the car to get finished. Also has a huge fastraxs BB turbo to bolt on to it. Give us till spring and we'll let you know how it works out. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted November 8, 2002 Share Posted November 8, 2002 If your aim is to lose peak power and peak torque (relative to using an L28 crank), then you're on the right track. The higher rev capability would be more than offset by the lost displacement. Peak piston acceleration for an L28 at 7000rpm is the same as for an L24 at 7320rpm. That means you could rev 4.6% higher, but the displacement of the L24 is 13% less. So you'd have ~13% less torque and ~9% less peak power potential. There are L28 setups that will get you in the CR range you want, anywhere from 7.5:1 to 10:1. Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 8, 2002 Share Posted November 8, 2002 yeah I mean I'm not trying to say your wrong and that it has to work because it makes sense to me. I'm no turbo expert either (just read some stuff on it), I'm just trying to start some conversation and learn a thing or two from people who do. also if this would work then it would be relatively cheap and you wouldn't have to spend alot of money to get the 280zx to take more boost. also you said you think you would be loseing more power than you would gain at higher 30+psi boost. I just saw this 2.0 volvo engine running like 42psi makeing insane power(I forgot the actual numbers), I guess I was just wondering if this would be an easy way to crank up the boost(not to 42psi but maybe 4-5psi more at least). oh yeah and the stock zx can take 25psi. Quote Link to comment Share on other sites More sharing options...
Guest Ian turbo240 Posted November 9, 2002 Share Posted November 9, 2002 I've gotta pipe in here. First to Rick Bowers: Looks as if you will have to have custom pistons made for this engine due to the reduced deck height caused by the shorter stroke (79 - 73.7mm). The deck height is the same when using L24 crank and rods with L28 pistons vs. L28 crank and rods with L28 pistons in any L6 block. All of the L6 blocks have the same deck height, and using the L24 crank and rod is what we are discussing. The pistons also have the same compression (pin) height. Second: oh yeah and the stock zx can take 25psi What stock 280ZXT engine are you talking about? The last time I ran 20psi on a stock 280ZXT engine, it blew a headgasket! Maybe what you meant is that the stock internals are capable of handling this amount of boost if you have the proper engine management and turbo using 100+ octane fuel. That's about the only way for any L engine to survive that amount of boost. Now consider this: I just saw this 2.0 volvo engine running like 42psi makeing insane power(I forgot the actual numbers), The main problem with the L engine is the cylinder head design. The Volvo engine (B20FT?) is a cross-flow head, which promotes a little better HP. You also have to consider cylinder pressures at a certian boost level. To a point, an engine will respond well to boost increases. Then, it will reach a point where the tuner has to take out a lot of timing to conpensate for the high cylinder pressures so that detonation does not occur. There is a point where the boost increase will not make a power increase because of the need to retard the timing too much to avoid detonation. This tends to occur at about 25psi for the L6 engines. Any more than that and you are just putting an unnecessary load on the turbo and the engine. At this point, the only way to increase HP is to increase the VE of the engine, or to increase the RPM at which the peak torque is achieved and maintained. Some ways to increase the VE is:larger turbo head porting/large valves better camshaft etc. Inevitably, doing these things acomplishes the second thing which is raising the rpm at which peak torque is reached/maintained. However, most of the time, this leads to an engine that has a narrow powerband, and is no fun to drive on the street. All in all, your best bet for a street L6 engine'd car is about 3.0 liters with a hybrid turbo and good intercooler. With good ems, you will get 350-400hp. Hope this helps out. Ian Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 9, 2002 Share Posted November 9, 2002 dan, you do know we are talking about a turbo car don't you. I understand that if you were to attempt to do this on a normally aspirated car then thats what it would look like. the stock CR of a 280zx turbo is 7.6:1. I figure with the above set up you will be able to drop compression below that to accommodate for more boost, more boost=more power. eric Quote Link to comment Share on other sites More sharing options...
Guest eric-z Posted November 9, 2002 Share Posted November 9, 2002 oh yeah, Rick what would be the consequences of haveing the negative deck hight? Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted November 9, 2002 Share Posted November 9, 2002 Yeah, I know you're talking about a turbo. But I *think* (me no turbo expert) you can run as much as 20psi at 8.5:1, intercooled. And a lot more than that (I'd guess) at 7.6:1. I just don't hear of ANY serious turbocharged street engines below that CR level, I think you'd be losing a lot more than you'd gain with more boost (30+psi?!). I think you should figure out what CR you want, based on what boost you want to run, then try to get there with the L28 crank (or LD28 crank?). The point is, you can get there without resorting to a shorter-stroke crank. Quote Link to comment Share on other sites More sharing options...
speeder Posted November 11, 2002 Share Posted November 11, 2002 Oh yea I do remember reading somewhere that all L series pistons have the same pin height Sometimes I resemble my avatar. Quote Link to comment Share on other sites More sharing options...
Guest Ian turbo240 Posted November 11, 2002 Share Posted November 11, 2002 Rick, BTW, that is one wicked freakin' Z you have on your sig! I like it (jealous)!!! Ian Quote Link to comment Share on other sites More sharing options...
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