Chewievette Posted May 8, 2006 Author Share Posted May 8, 2006 While I'm not going to argue with you guys since you have far more experience with these engines than I do, I have to point out that with this combo the rod/stroke ratio is right about 2:1. I have always been told that the easiest way to increase power is to increase rpm, not displacement. Why else would all those ferraris and lambos be running such high revs? I've noticed that there are two ways to make power; the american way, big cubes low rpm and everyone else's way, high rpm, small cubes. I dont know, I guess I need to do some more research. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted May 8, 2006 Share Posted May 8, 2006 While I'm not going to argue with you guys since you have far more experience with these engines than I do, I have to point out that with this combo the rod/stroke ratio is right about 2:1. Which, relative to the lost displacement, will amount to somewhere between diddley and squat in terms of power/torque (i.e., you'll still be making way less with this "superior" r/s of 2:1). I have always been told that the easiest way to increase power is to increase rpm, not displacement. Why else would all those ferraris and lambos be running such high revs? Absolutely NOTHING wrong with gaining power through revs. BUT, giving away 7% displacement to gain ~3.5% more theoretical rpm (not even that on the L6!) is not the way to improved performance! I've noticed that there are two ways to make power; the american way, big cubes low rpm and everyone else's way, high rpm, small cubes. I dont know, I guess I need to do some more research. Actually, the way to make power is big cubes AND high rpm! But displacement IS more important. Maximize displacement, THEN maximize rpm! Quote Link to comment Share on other sites More sharing options...
johnc Posted May 8, 2006 Share Posted May 8, 2006 Racers who build displacement limited engines do so because of rules. Those GT2 2.4L engines spin to 9,000 rpm because they have to to make the power needed to win. Tony D is crewing for a Z running a L20A in a Bonneville car that redlines at 9,300 rpm. They did that to meet the regulations for yet another class. For a street engined car that is not limited by rules, displacement is the most logical and lower cost path to power. But, having heard a 2.4L engine in front of a sequential transmission bang to 9,000 rpm 4 times as it accelerated down the front straight at Laguna Seca, I can say that the sound will make the hairs on the back of your neck stand up. There's a certain emotional value to that, which I have yet to experience with a stroker shifting at 7,500 rpm. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 8, 2006 Author Share Posted May 8, 2006 Okay so this is a totally bad idea with no merrits what so ever and I should run away screaming eh? Sounds great... Quote Link to comment Share on other sites More sharing options...
johnc Posted May 8, 2006 Share Posted May 8, 2006 Its not a "bad" idea at all. Remember, this is HybridZ. You'll get opinions here offering alternatives and some of the wording of those opinions seem kind of absolutist, but that's typical of text based communication. If we were all sitting around a picnic bench, body language would show that this whole thing is just bench racing. Ultimately you do what you want to do and we would look at your car and say "cool!" Quote Link to comment Share on other sites More sharing options...
Mack Posted May 8, 2006 Share Posted May 8, 2006 not necessarily run away screaming, just realize that its probably not going to make the horsepower you are thinking it will unless it had a BC gerolomay ported head and a race camshaft on it. as well as balanced the hell out of everything in the rotating assembly, running superlight forged pistons and all that crap. reason I was looking at doing it is I need an 89mm bore, and I wanted a semi high RPM motor.... plus Im too cheap to source an LD28 crank and do all the necessary parts. I already have an L24 rotating assembly and an N42 block with a trashed crank. If you wanted to do just to be different, go ahead. just dont get pissed when the guy with the 3.1L kicks your *** on the street. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 8, 2006 Share Posted May 8, 2006 If you wanted to do just to be different, go ahead. just dont get pissed when the guy with the 3.1L kicks your *** on the street. You can always negotiate for a starting line advantage because you're running a 2.4L block... I know of one 240Z here in SoCal running a true 2.4L engine that is making lots of power on 100 octane unleaded and SUs. He's spanked more then a few strokers even without a head start. Even after the losers count the freeze plugs in the block they just won't believe that a 2.4L on SUs can beat their 3.2L running webers. Displacement sometimes gets beat by good tuning. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 9, 2006 Author Share Posted May 9, 2006 Even though it might not make all the power it can, I dont expect it and to tell you the truth I dont really want it. Too much power can be a bad thing too. Besides if I dont like it I only have to swap the rotating assembly out to get a standard stroker engine. The L20A crank is as good as bought so I'm committed now. I keep finding new LD28 rods for $150 each! I think I'll go used for those. I would use lighter rods but I havn't tracked down a source for FJ20 rods yet, anyone got a source? Plus I have this devilish idea to throw boost on it so diesel rods might be a good idea. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 9, 2006 Share Posted May 9, 2006 you know, for as heavy as the LD28 rods look, they only weigh about 80 grams (each) more than L28 rods. not THAT bad. that was done on a shadow scale thingamabob. supposed to be very accurate. at first we thought it was 100 grams! but then realised that the bearings were still in the LD rods and not the L28 rods, lol! You could make up that difference by lightening up the pistons. Ask 1 fast Z how much lighter you can make pistons. I think he took out almost 2 pounds from a total of 6 pistons. and that was going from standard flat tops to an 89mm bore as well. oh yeah, one more thing..... the LD28 rods have a 25mm pin. so, yeah, you'll have to figure something out there...... Id suggest going through KB silvolites web catalogue and search by diameter and look at the pin sizes, you never know there might be something out there for a stock motor that may fit your application..... Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted May 9, 2006 Share Posted May 9, 2006 I thought stock L24 redline was 7000... If that, then the peak inertial load comes to 2570G His setup will extend the redline to 7290rpm(if inertial load is kept the same) Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted May 9, 2006 Share Posted May 9, 2006 I like the idea. Good to see something different. One thought though, reciprocating mass has more or less of an effect on rotational inertia than rotating mass? I think it would be more. Dave Quote Link to comment Share on other sites More sharing options...
Clifton Posted May 9, 2006 Share Posted May 9, 2006 Too much power can be a bad thing too. I haven't run in to this problem yet:mrgreen:. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted May 10, 2006 Share Posted May 10, 2006 Too much power can be a bad thing too. I have this devilish idea to throw boost on it Hmmm, so is power GOOD, or BAD?! If you're SERIOUS about maximizing power, you may as well know that destroking is not the way to do it, as cool and novel an idea as it may seem. When Mark Donohue (race driver/engineer extraordinaire) was asked how much power was TOO much (he drove 1000hp turbo Porsche CanAm cars), he said when he could spin the tires at the end of the straight, that was enough. Cirrusly, just because you've as good as bought the destroker crank doesn't mean you have to use it! I still encourage you to make the MOST of your build and not bother with destroking it. But, in the words of Aleister Crowley, "Do as thou wilt"! Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 10, 2006 Author Share Posted May 10, 2006 As long as I have a source for all the parts I might as well try it right? I am NOT going for max power, I cant spend that much right now. and when I do its certainly going to be with some sort of stroker. but for now I am just trying something that's not too difficult and as far as I've been reading, never attempted before. I just want to see what kind of numbers the engine can put down. If I dont like it I'll save up and build something else! I LOVE building engines, if I could make money at it that's all I'd do. I'm not afraid of spending my money on something that very well might not produce the most power ever. I threw in that comment about boost because I have an unhealthy obsession with twin turbos, so its not a huge stretch of the imagination to see myself putting a couple on there. Especially if it turns out to be a weak engine, boost would serve as a bandaid in that situation. Although I have yet to find a weak L6. Quote Link to comment Share on other sites More sharing options...
evildky Posted May 11, 2006 Share Posted May 11, 2006 I know a local guy that took an L28 block and E31 head (shaved and fitted with oversized valves) L24 crank, forged pistons, lots of porting and an L7 cam, that thng revs like a motorcycle engine, it is absolutely amazing the power band comes on at like 1500 and feels pretty much flat to 7000 rpm Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted May 19, 2006 Share Posted May 19, 2006 Short stroke/oversquare is a fine idea (my Aprilia is 97mm/67.5mm), but if you're giving up displacement for it you are giving up power. Throwing away stroke just to get a "better" bore/stroke ratio (or rod length/stroke ratio) is barking up the wrong tree imo. Fuel economy differences between the destroker 2.75 and stroker 3.1 would be minuscule. Consider that for a given weight and aerodynamic characteristics, it takes the same hp to the ground to drive the car at a given speed, whatever the displacement is. The larger displacement will have greater internal losses, but not by much. Gear the smaller-displacement motor appropriately as recommended and any fuel economy benefit disappears! Closer-ratio gearbox is desirable anyway if the engine has a relatively narrow powerband. Which is why I have an '84 truck 5-speed. No doubt a 302 Z28 is a blast to drive (never had the opportunity)! But a similarly-tuned 383 would be, too! It'd be much faster, and wouldn't give up as much revs up top as you might think. Nothing's more fun than pressing the accelerator down and getting THRUST. More thrust = more fun (to me!). Even if the bore/stroke looks more like a tractor's than an F1 engine's. To each his own! But don't deceive yourself... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 19, 2006 Share Posted May 19, 2006 I gotta wonder how much of a favor you'd be doing yourself to run a 2 liter with a 4.44 rear end vs a 2.8 with a 3.36 (for instance) too. If we weren't talking about existing engines, I'd love to have an oversquare 3 liter L6 that revved to 9K. But withing the confines of reality, the 3.1 is going to make more power than the 2.0, regardless or r/s ratio or ultimate rev capability, and the rev limiter isn't the r/s ratio, its the crank itself, and the valvetrain. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted May 19, 2006 Share Posted May 19, 2006 Don't spend a lot chasing after a good stroke/rod ratio though, the benefit in terms of horsepower is little, usually not noticable until high rpm is reached. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted May 20, 2006 Author Share Posted May 20, 2006 Too bad there's not a "tall" aluminum L6 block available with 92mm bore... Its in the works... This engine might be a fading dream since my daily driver is beginning to act up, the expensive kind of acting up.. If it breaks, I wont have any choice but to swap in the stock L28 and get the Z running that way. Quote Link to comment Share on other sites More sharing options...
wishihadaz Posted May 25, 2006 Share Posted May 25, 2006 You can always negotiate for a starting line advantage because you're running a 2.4L block... I know of one 240Z here in SoCal running a true 2.4L engine that is making lots of power on 100 octane unleaded and SUs. He's spanked more then a few strokers even without a head start. Even after the losers count the freeze plugs in the block they just won't believe that a 2.4L on SUs can beat their 3.2L running webers. Displacement sometimes gets beat by good tuning. I/we would like to know who is building and tuning 2.4Ls like that! I'll bet it's only for the track though, right. Quote Link to comment Share on other sites More sharing options...
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