Dan Baldwin
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Posts posted by Dan Baldwin
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Norm is running N42 with alot of material shaved from the bottom of head. He said his head chamber isn't open any more. It's like E31 head
True enough. Mine, after some shaving, is still an open-chamber head, though. As I stated above, I've run over 10:1 with the stock cam without any real detonation issues. I'm at 10.8:1 (from actual volume measurements) now, but of course I do have a pretty big cam.
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In my first post I implied that D_D gave us the equation for the volume of a square "cylinder". The equation pi*D*h (height times bore times 3.14) is actually for the surface area of a cylinder.
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Oh yeah, Dresbach, I don't think the higher compression will wear out your engine faster, as long as there are no detonation issues, and there shouldn't be assuming the ignition timing is set properly. It's better to burn out than fade away anyway, right? A properly tuned L28 with 9.8:1 CR should last practically forever. These engines are very strong and reliable. Oh yeah, the handy Lengine calculator gives 8.5:1 for the dished piston motor, and 9.8:1 (not quite 10) with the N47 head, so the gain, stock vs. stock, is more like 1.3.
I do think you will notice the power gain. Beauty is that torque is increased EVERYwhere, from idle to redline. If you're stock cammed, you might try to aim for maybe 10.2:1. I did run around 10.5:1 for a while with the stock cam without issues, but that's with a different bore/stroke, and might have been right on the edge. The only times I got detonation was when I stupidly set the timing to 18 degrees at idle, with the stock mechanical advance, which gave me something like 43 degrees advance at rpm, and when I lost an advance spring and was getting ~25 degrees or so at idle.
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Before I rant, I'll address the original post. Dresbach, What your proposing is an excellent idea. Easy swap, and your compression will go up about 1.5, from ~8.5:1 to ~10:1 assuming neither head is shaved. You might want to check the cc volume to see if it has been. Stock cc on an N47 is 44.7cc.
Now for the ranting and raving (tune out if you don't have the stomach for it):
Whoa, this is getting scary! Datsun-Dude, your volume equations are incorrect. The volume of a cylinder is pi*r^2*h. NOT pi*D*h (unless you have square "cylinders")! Also, a 1 liter beaker isn't going to give you nearly the accuracy you want. We're talking about chamber volumes in the 40cc range. 1cc accuracy is essential, and you'd really like to be in the tenths. ARRRRGGGGGGHHHHHH!
Shane, you do know that the Grand National was turbocharged, not supercharged, right? As has been gone over before numerous times on this and other sites, the supercharged L28 is a pretty poor idea compared to a turbo as far as practicality and performance are concerned. Besides, all this guy wants to do is increase his compression
DAW, as has also been beaten to a bloody pulp on this site, an open chamber N42 has been used on MANY highish compression L28 without any undue detonation issues. OK, Norm broke some ringlands at 11.6:1. I have had no issues at 10.5 and 10.8:1. NONE. On 93 pump. N42s and N47s have been plopped on many a flat-top bottom end with no problems. Just because the open chamber heads *theoretically* should have detonation problems doesn't mean they do. Based on my and others experience, what the poster is proposing does NOT pose a detonation risk.
PEOPLE, if you do NOT have the technical or practical expertise on a subject to offer helpful feedback, DO NOT POST.
I'm not trying to be mean, but what I've seen in this thread is NOT up to the standards of HybridZ. Not by a long shot.
If this reply is too insensitive for HybridZ, may the moderators remove me now.
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I think you're backward on the rod angle/leverage issue. Since max cylinder pressure is ~15 degrees, the longer the rod, the worse the rod angle in terms of leverage. A shorter rod will be situated at a greater angle with the crank throw, which will give greater torque. This is augmented by the fact that since the rod is in pure compression, and is at an angle, and has to react all the vertical force from the piston, the actual compressive force in the rod is actually higher than the downward force on the piston. The downside is piston side load. The shorter the rod, the greater the side load, which means greater frictional losses.
Anyway, my point is that longer rods aren't necessarily better for performance. Too long and you should lose torque due to the rod primarily pushing on the crank radially, with the tangential torque-producing force minimized. Too short and the side loads will take away from the gains from improved angularity between the rod and crank at max cylinder pressure.
In any case, increasing displacement is most likely a power-improving proposition, even if frictional losses are increased due to increased rod angularity.
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Keep your provocative' date=' condescending comments off the forum. DAW[/quote']
Zounds! What is this, ancient thread resurrection week?! Hey, if you're not paying attention to pertinent aspects of a discussion, you can expect to get a little semi-polite ribbing for it. It certainly isn't meant to piss anybody off, only to get them to THINK. Am I the only one on the whole fricking internet that can occasionally stand to be corrected, and even once in while find that I was maybe (gasp) wrong about something without working myself into a tizzy over it?!
As far as your 4-years post-doc, congrats! I did manage 2 years of graduate study to get my M.S. WAY back when, and I DID do it with a short attention span!
But cirrusly, that post (and this one) was NOT meant to be mean-spirited at all. I like to think it was in the spirit of light-hearted comeraderie. I'm sorry if it doesn't appear that way from your end.
Happy Memorial Day!
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De-stroking is for boosted motors' date=' for the most part. The idea is to put more direct pressure on the crank. The down side is that the rod has less leverage on the crank, which may limit torque. The up side is that the motor can rev higher, and produce more power.quote']
More direct pressure on the crank? I have no idea what you're talking about there. If you reduce stroke, you WILL (as opposed to may) reduce torque. Please go to the beginning and read this whole thread again. On any L6 combination I can put together, destroking ALWAYS loses power potential. Yes, the short-stroke motor can rev higher (assuming equivalent piston strength), but not by enough to make up for the lost torque. Believe it or not, to maximize the power of a motor you pretty much want to maximize its displacement, via bore and/or stroke. This applies to boosted and NA motors. Yes, you can make as much power with a 2.8 turbo as you can with a 3.1 turbo, but only if you have more boost. With equal boost, the larger displacement motor wins. At equal power levels, the bigger motor still wins, as it's operating at a lower boost level, so less lag, more streetable.
Why do you think 83.6 is the "perfect" stroke for an L28? I would beg to differ:)
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First, this is not Dan Baldwin, but Bob H. Dan is at my house and we are trying to get his motor up and running again after his big rebuild,(it broke after we took it to VIR).
First, DAW, in your post, you were addressing three basic sizes of heads and to the best I could tell, also about three different E-88 heads. Yet on page 4, post 6,(before the post you commented on) Dan posts about the 4 different type of E-88 heads. Hence his "short attention span" comment.
(steps up on soap box)
I got sick and tired of members whining or complaining the moment they felt they were personally insulted or the thread took a negative turn,(its the internet, not real life). Far too many people are way too sensitive on the internet boards. At the least sign they were "personally affronted", off they went to whine to a moderator. Don't misunderstand me as I think there is a good role the moderators can play in this,(although they don't always). You get members who post a reply to a more forward response from someone like me: "hey! that's not nice!, That is the most insulting thing ever said to me" or something along those lines.
Give me a break guys. HybridZ is one of the only good Z boards left but it may not stay that way. It has taken a rather significant downturn in the last few months. There is a natural turnover in all boards, but you hope to retain the knowledgable types over time,(or at least replace them). Dan and I were discussing how esp. in the last few months, memebers on hybridz have gotten really sensitive. This was not the first time someone has had a response like DAW against Dan or others. I'm not saying my approach is the best, but it does cut down on the signal to noise ratio. There is a balance to be found, but grow up guys. It is usually fairly clear when it is a one on one insult.
In the end, hybridz faces becoming a zcar.com or otherwise. That would be a sad, huge loss. I encourage you guys to think a bit before feeling offended, much less posting about it. I encourage you to PM the individual vice posting it to raise feathers of all involved It is the internet and sarcasam and feelings don't convey well. If you have someone who has been here for a while and a bunch of posts, it is unlikely they are attacking you or trying to insult.
(steps off soapbox)
-Bob Hanvey
edit- I see Pete (and Tim!) addressed it well.
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First of all, the end justifies the means for tyrants. Not calling anyone HERE a tyrant, just pointing out that that philosophical viewpoint deserves a bit of analysis. i.e., how do people end up behaving when their perhaps well-intended ends justify any and all of their actions?
From reading the posts through, the "end" intended is simply to have a DOHC head on an L-series motor. All I want to know is "why"? The object seems to be to have an aftermarket head or highly modified head from another car to sell to the L6 Z community as a performance upgrade. This IS a farfetched idea. Sure, I'd love to see it done, but i haven't seen anything in this thread that leads me to believe that it's gonna happen any time soon. Automakers have TONS of experience designing and building cylinder heads. And they have VAST economies of scale on their side. Not to mention armies of engineers and designers. We (If I may use the editorial "we" here) don't. I keep hearing things like "cost is no object" practically in the same breath as "RB26 cylinder heads are too expensive". Making a bolt-on DOHC cylinder head for an extremely limited market is going to be a fricking expensive and time-consuming proposition. Those of us who want to go fast have WAY too many better options.
The idea is a helluva lot easier than the execution. This is art. This is science. This is engineering. This is certainly a worthwhile endeavor in terms of an educational experience. This is NOT the path to a practical and reasonably priced performance upgrade to the L-series engine, I don't think.
Believe it or not, I AM trying to help. Really.
An Italian philosipher once said "The end justifies the means." That's what this project is about' date=' me thinks...Everyone seems to want to critisize this idea or offer advise on alternative motor swaps or mods instead of contributing thier knowledge to the project!
<snip>
But when someone comes forward and pitches an idea--that doesn't sound farfetched at all--for for a mod that's sure to boost the perfomance of your motor, he gets shunned.
The fact is, if performance shops sold twin cam, 24 valve heads for the L28, half of you guys would have it on your car, probably reguardless of price. Right now there's a guy trying to make that a reallity; let's show a little support, eah...
Sorry if I come off a little harsh; I'm not trying to step on anybody...
It's just that sometimes these discutions start turning into arguments when we're supposed to be trading tech tips and advice...
So let's get back into the groove here, comrads :wink[/quote']
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First off, HOLY CRAP that is a BIG engine!
Now for more pertinent stuff. Design rpm ranges for camshafts have NOTHING to do with structural concerns. Only for getting mixture into the cylinders and exhaust out.
You don't *have* to be a structural engineer to put together a big motor that will survive, but it would help if you had the assistance of an EXPERT in the field, rather than putting it all together yourself and hoping for the best.
As far as hope for the bottom end, I was thinking of NA L6 motors. This is a deep-skirted design, and the bottom end is very stable. Your monster motor may need that girdle for stability.
Again, rule-of-thumb maximum average piston speed doesn't account for a lot of what goes on in the motor. Specifically, it doesn't account for the effects of rod length on peak piston accleration. It also doesn't account for the actual strengths of pistons, rods, crank, block. I think you should find a knowledgable, successful engine builder experienced with building reliable monster motors like yours for the street, and open your wallet. It sounds like your engine is way to specialized for way-too-general rules of thumb regarding safe engine speed.
What is happening to my mind is that I keep reading how cams are good for 7-9000 rpm and the guys who are talking about them and some apparrently running them' date=' and I wonder where all the data is to substantuate and confirm such engine performance physicallysnip
I am thinking things like modus of elasticity and tensile strength and 'G' forces gainst a complex reciprocating mass.
snip
At this time I personally don't think even 6500 rpm would be safe using this setup without a Girdle, but there again, info online is very sparce in that area.
snip
You speak of "Hope" for the bottom end [/quote']
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Valve events have zero to do with it. There is some compression relief TDC on the compression stroke, but on the exhaust stroke you're looking at all that mass being slung around at TDC with no opposing forces to speak of. 4000fpm (average speed I presume) sounds like a general rule of thumb number. But it's not speed that kills, it's the sudden stop. i.e., peak piston acceleration is more important than average piston speed. Allowable peak piston acceleration will depend largely on piston and rod design and construction. I would hope that the bottom end is stout enough to handle all the pistons and rods can.
What kind of setup are you thinking of, and what redline are you hoping for?
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Any will bolt in except the T5 from the ZX turbo. Problem is that the hole in the tunnel is in the wrong place (assuming yours is the "monkey-motion" four-speed, with the straight shifter mounted in a rubber bushing hanging off the back of the tranny). The later 4-speeds and 5-speeds have a bent shifter that mounts to the tranny a bit forward relative to the earlier tranny. You can either butcher the hole, or modify the shifter to offset it aft.
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Gonna take a lot of work to complete (few years probably)
It is an old car with old suspension design
Of course the car is an old design but how much does that limit it's capabilities? Can it be modified within a reasonable budget to do over 1g on a skidpad and 70mph in a slalom?
I have a '71 240Z, somewhat modified in the suspension and motor departments. I also have a '95 Z28 convertible. I can say that the 240Z's "old" suspension design is about 1,000 times better than the Z28's. Not a whole lot has changed in basic suspension design over the past 30 or so years, geometry is geometry. The 240Z's McPherson strut/Chapman strut arrangement is pretty good, not perfect. It is (IMO) far better than most semi-trailing arm IRS arrangements (BMWs and 911s up to the 90s). And it's light-years better than the F-body's live axle arrangement. Stock vs. stock and mod vs. mod, a 240Z would handily outhandle (har har) a 3rd gen F-body, maybe even laden down with 1000 lb. of ballast to eliminate the weight advantage. With the 1000 lb. weight advantage of the 240Z, it shouldn't even be a contest.
All that said, it was a hoot to watch an LS1 Camaro hold off a Boxster S at the SCCA races a couple of weeks ago at NHIS. The Boxster could keep up, but never could pass. Of course it goes without saying where each of them was faster than the other.
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Just so everyone knows, I did NOT write the word "dodo". Ferchrissakes, if you wanna **** me, go ahead, but don't put WORDS I DIDN'T SAY in my posts! Please?
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My 3.1 had no issues with running hot, with proper carb jetting. That's putting out 235 rwhp, and with a 3-row 260Z radiator. The engine was strong as a horse for ~30k street miles and 50+ track days, until that little issue of losing oil pressure on right-handers finally caught up with me. Rebuild in progress. Comp oil pan with swinging gates will replace the stock one I was using.
FWIW, the parts for the rebuild ran me $1150. New pistons, one new rod, lots of little shit that added up.
If you want to get to 250hp NA, you want to maximize displacement. I'd go 3.1 if you're staying with the L6. $250 for the crankshaft doesn't seem so bad when you're spending that much or more on an air filter/backing plate! You'll also be spending at least $1000 (I spent $1500) on headwork and cam setup. I went cheap on carburetion, $600 for a used set of triples.
Last time I added it up, my motor cost me about $5000 to build, including everything, so there's at least a data point.
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I doubt that a heavier car with less hp would be faster than Jeffp's car:) If you would like to be able to market them, then cost is the #1 issue. If you attempt this I certainly wish you success, but there are dozens of more cost-effective ways to bestow your love upon the Z car that would be more effective at making power, and would be less likely drive you to insanity over the course of the next 2-5 years!
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Even at that hp level, rod life/reliability is really more a function of operational rpm levels. Ignition and fuel controls are WAY more advanced than they were 30 years ago. Suspension and engine mechanicals, not *as* much more advanced. That's what I have to explain to Z06, M3, etc. drivers that can't believe my dinosaur-age car was quicker than their latest/greatest tech gee-whiz-bang-mobile around the race track:)
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Are these custom rods, or treated stock rods? How high will you be revving? Stock rods *can* be had for WELL under $100, if you have a sympathetic Nissan parts guy on your side. Probably good for 7250rpm or so as-is. Lead time maybe a week?
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I'm talking about just dropping in an RB26 engine. You can get them for ~$5000 or so in the US. Timewise and costwise, I just don't see any justification for trying to make a DOHC 4-valve head for the L engine. Also, it seems to me that valve area might be a limiting factor for an RB20 cylinder head on a 2.8+ liter L engine. And you wouldn't be able to go very much bigger, certainly not enough to take full advantage of the L motors larger bores.
I guess I still just don't get it.
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So, how is this gonna be cheaper or easier or better than an RB26?
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Why on earth wouldn't you just plop in an RB26 engine? It sounds like the end-goal is more to have a DOHC 24valve Z car than to have a very expensive (in terms of time and money), but possibly worthwhile learning experience. If the primary goal is increased performance, I wouldn't even consider attempting something like this. There are several MUCH cheaper, quicker, and similar- or better-performing alternatives. Hey, SOMEbody's got to be the voice of reason here;)
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So far I've gotten .200-.250, and .180 minimum from one reliable source, .090" from another source, and ~.150"/.100" minimum from Nissan Motorsports, with the caveat that consistency is important (i.e., .100 on one side of the bore and .200 on the other side might not be so good).
My block is about to be checked, I should have numbers tomorrow. I'm keeping my fingers crossed. REALLY hoping it looks ok to go another .020" so I can use KA24E+.5mm pistons. Not going with forged since I learned that some KA24E race motors rev to 7400rpm reliably with STOCK pistons. That's a much longer-stroke motor than a 3.1 (96mm vs. 83mm).
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I'm having my block ultrasonically tested and would like to get an idea from those who know what I should consider a minimum thickness. The builder wants to bore (hone?) at least .25mm (.010") to clean up gouging from the #1 piston, which had been in contact with the conrod (not properly clearanced).
Note that I put 50+ track days and ~50k street miles on this engine before the lack of oil pressure during right-handers caught up with me and I lost the #1 rod bearing, so I wonder if I should even worry about this...
Thanks,
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It's the reduced piston acceleration that allows for higher rpm with a shorter stroke. As mentioned above, though, you lose more torque than the increased rpm would make up for. Basically, this is a very good way to lose torque EVERYwhere, and lose peak power as well, while having a *marginally* higher redline.
Another thing worthy of your consideration is that with greater displacement you can tune more for high-rpm power, while still maintaining enough low-rpm grunt for streetability.
Displacement rules.
Dyno torque poll, both NA and Turbo L6s
in 6 Cylinder Z Forums
Posted
Turbo has WAY more torque and hp potential. At the same power level, the turbo will have a MUCH better torque curve, as YO said. It'll be making close to peak torque for a much broader rpm range, starting at much lower rpm.
If torque is bigger than hp, you've got way more power potential, turbo or NA. The nature of the engine's torque delivery will change, though (greater lag for the turbo, reduced low to midrange torque for NA).
If peak torque is greater than peak hp, torque must be falling off relatively early, given that a stock L6 is good for 7000 rpm or so. O' course if you're making 456 lb-ft to the wheels, it's going to take a mighty big turbo to keep that up at 6000 rpm (I think, not a turbo expert here)!
z1, how much boost are ya running? Damn those numbers are BIG! Link to dyno sheets?
One of my 3.1 NA dyno runs from last year can be seen here: http://www.classiczcars.com/photopost/showphoto.php?photo=2274&password=&sort=2&thecat=500
I later gained 5hp (different dyno, went from 228 to 233) by going to smaller air jets, improving the lean condition at the top end. Don't know what's up with the RICH spot and corresponding hole in the torque curve. Hopefully the recently corrected cam timing (I was running it ~4 deg retarded) has fixed that to some degree. Feels better for sure. The dyno will reveal...
I've gotten reports of a 10.4:1 3.2 NA motor making 280+ lb-ft at the crank (seems pretty optimistic, I'm only making 200 to the wheels), with a much lower peak hp figure. It all depends on where the torque curve is. Mine was all above 4500 (hopefully more like 3000 and up now).
Anyway, to make big hp numbers NA, you've gotta rev it, and be willing to sacrifice low-end to some degree. With a turbo you have options. Lower boost and highish revs, or higher boost and lower revs. For maximized power you'd want to maximize boost and revs.