Dan Baldwin
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Posts posted by Dan Baldwin
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Whoops, pardon me, I though you were thinking of INcreasing boost and retarding timing. Backing off both can't be a bad idea if you're unsure you'll have the gas you need to run at 14psi/27deg.
Have fun at Lime Rock, I'll be there with COMSCC on Nov. 19/20. BRRRRRRR!
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If you've never driven on a track before, leave the boost turned down and don't worry 'bout octane boost. You'll have your hands PLENTY full learning to carry speed through the Uphill and Downhill without the extra power
Also, consider that you're going to be running the engine HARD, no reason to try to experiment with a setting you haven't proved under more benign conditions.
Think I'd experiment at the dyno with timing/boost level/octane boost before turning it up at the track.
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My opinion is:
Forget about stroking it. You're wasting time and money doing that.
You can get 500hp from 2.8L Think more "high rpms" / less stroke.
The rpm potential you gain with the shorter stroke is less than the displacement you lose. Assuming custom forged pistons and bottom-end rebuild anyway (500+hp, right?), stroking shouldn't raise the cost much at all relative to total project cost. 5% more stroke = 5% more torque everywhere, at the expense of ~3% rpm potential up top, assuming peak piston acceleration is the limiting factor. I'd rather have the 5% everywhere than 200 more rpm up top.
That said, for a first-time turbo build, I'd plan on more modest hp goals and build on a JY 2.8 turbo bottom end and get some experience with building a turbo before risking a bottom end with a lot of time and money invested in it.
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The little magnets are sorta press-fit into the plastic collar/sleeve that slides onto the distributor shaft, with a couple of layers of adhesive teflon tape holding them in. The tape had come off and the #1 and #5 magnets came out from centrifugal force. I epoxied all of them in place and taped over them again.
Won my class at NHIS, and set the SPB class record for NHIS chicane/chicane at 1:18.7. I think I was third-quick overall, behind a Formula SCCA car (1:11s) and a very fast and well-driven ~400rwhp supercharged M3 built by Turner Motorsports (1:15s). It was pretty funny being gridded behind a freaking formula car and in front of the killer M3 for my timed runs (they run groups of cars with similar times to prevent "catches"). There were a few wide eyes at that sight:)
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.008/.010 are cold clearance numbers. I don't think I'd set them tighter than that.
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Decided the good news deserves its own thread:)
I had thought I killed the motor by lean-running-induced detonation. It suddenly lost a ton of power and started running ragged after an acceleration run from ~80 to ~110. Initial look at pistons through the spark plug holes revealed what I *thought* to be detonation evidence. Figgered I might have holed a piston or something (I tend to assume the worst-case scenario has indeed happened). More experienced eyes saw only carbon build-up flecks.
The REAL problem turned out to be the Pertronix Ignitor (replaces the points) throwing 2 magnets, killing cylinders 1 and 5. The magnets (being magnetic and all) were right there stuck to the vac advance plate. Glued and taped 'em back in place. Runs mucho better-o with all 6 firing!
To the track!
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Turns out the Pertronix collar that goes on the distributor rotor lost two magnets, that was the problem! I tend to assume the worst initially... Going to NHIS tomorrow, WOOHOO!
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Just did a compression test, all 6 between 190 and 215. Cleaned and gapped an old set of plugs and gave 'er a try. And the freaking starter wouldn't stop spinning. Even after I turned off the key. Guess I need a new solenoid and/or starter. SHITE. Home I go again. It's a bitch to have to work on the job job during the day while the car is just back in the shop desperately in need of some attention. I should work closer to home...
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You know, if you didn't hear the detonation when the thing was in full melt down, how do you know it hasn't been detonating before this?
I'm sure it has been. I've had the fuel delivery issue for well over a year now, and have done quite a few track days with the issue. I stupidly hoped whatever crud was in the tank would clear out. He who lives on hope...
FWIW, at the time of the engine rebuild last year there was ZERO evidence of detonation, the pistons were pristine aside from some carbon buildup. Pistons that had seen ~3 years at ~10.35:1 with the stock cam, another ~2 years at the same CR with a 290/.503" cam, and another year and a half at 10.74:1 with the Sunbelt ~310/.550" cam.
Latest word, fab/shop/manufacturing guy here at work says it doesn't necessarily look like detonation to him, what's visible through the plugs and looking at the plugs themselves.
More to come...
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You P-head guys will get a laugh out of this, I think I detonated my motor to death
Like the 'tard that I am, I've been running it with fuel pressure issues for quite a while now (up, down, 0psi, 7psi), replacing fuel filters (at the tank, prior to fuel pump) ALL the time (once or twice a day at the track). Whenever it decides to not bump up to at least 2.5psi at the gauge under the hood.
Anyhoo, tonight I was scrubbing in a new set of Hoosiers on the highway, ~85mph, and a Sentra SE-R pulls alongside, obviously interested in the Z. So I drop to third and gun it. All is well initially, but the throttle seemed to stick (stupid floormat) for the shift into 4th. Then it just seemed to be running really ragged. Lost power. Oil pressure fine, no clanking, just no power and runnin pretty rough. Limped back to work, pulled car in the shop. Plug 4 ceramic busted, piston 1 has a fricking field of small craters on it. I'm guessing one piston has a hole in it (eww). Will further survey damage tomorrow.
I hafta get home now (always keep one motorcycle escape vehicle at work). 35 mile ride. Must get there and make meself a margarita or three to ease the pain.
Am I bummed? Yes. No track glory this weekend I guess.
I have but one thing to say: FOOK.
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But of course, with careful tuning and 2-3psi more boost on the 3.1, you again find yourself with a 10% advantage over the 2.8!
That said, if I were going turbo, on a schedule and on a budget, I agree that spending the budget on ancillaries is wiser than going the stroker route. But without time and budget constraints, I'd maximize displacement for sure. 10% is 10%, eh?!
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I knew Bush was a fricking moron before the debate, I know it even more now. Not a CLUE.
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What will the car's mission be? There's something to be said for being able to hit the throttle and GO from 2000rpm in a real-world street car.
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Big cams bleed off compression, AT LOWER RPM. At the design rpm range volumetric efficiency is as good or better than a stock/mild cam. Your setup will work, but a much higher CR is of course possible with that cam. I think a more pertinent question is will your FI setup breathe enough to take advantage of the cam at higher rpm. If not, you're sacrificing low-end with the cam but not getting the benefit up top.
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Here are my musings, but I'm no expert!
Compression ratio is a REFERENCE number. There is no need to bust your balls trying to find out what the ACTUAL compression is, just go by the geometrical ratio, as that's what just about all the useful comparison data out there will be based on. Dynamic or effective compression ratio is next to meaningless, it seems to me. A cam that gives good volumetric efficiency at lower rpm will require a lower compression ratio than a cam that gives good volumetric compression ratio at higher rpm, because of there's more TIME for detonation to occur at lower rpm, not because of less "effective" or "dynamic" compression ratio. If you can get close to 100% volumetric efficiency with a big cam (and you can, even MORE than 100% is possible over a very limited rpm range), then effective/dynamic compression ratio as I usually see it presented (based solely on when the intake valve closes) is sort of an invalid concept if you ask me, though it can lead to a correct conclusion (more cam => higher CR possible).
For the same reason, cylinder pressure during cranking doesn't really tell you anything conclusive as it's dependent on too many issues. A mild cam with high CR will yield greater cranking pressure of course, a big cam requires much higher rpm to fill the cylinder.
Just consider the geometric compression ratio, and know that with a bigger cam you can go much higher with it.
Like fastener bearing stress, it's not an ACTUAL stress, it's just the load divided by diameter times thickness. Test data is in terms of this REFERENCE stress, not actual which would be MUCH harder to measure. So the design, stress, and test engineers all have a geometrical reference value they all agree on. Same with CR. Absolutely no need to worry about the ACTUAL compressible fluid thermodynamics going on when all the reference data is going to be in terms of what geometric CR is possible given a fuel octane rating and cam.
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I'd leave it the frick alone and spend ALL efforts on the L28 build. You might get some sidedraft SU carbs to replace the downdraft Webers, but I don't think the 4bbl is a good idea. 4bbl = GREAT for a V8, less than ideal on an I6. I think the cam you'd want for the low-comp L26 and what you'd want for a built up L28 might be different anyway. I really think I'd leave the L26 alone except maybe SU carbs. Wet nitrous setup, maybe
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On a 260Z L26 bottom end, any of those head options will have your compression ratio very low (E31=>8.6:1, N42/N47=>8.3:1, shaved P79=>8.1:1). You might consider getting a 1981(?)+ 280ZX non-turbo bottom end (aka F54 NA) with flat-tops if you want a good base to build performance with. Here's what the New England ZCar club got with that bottom end with a stock N47 head and stock cam:
http://www.zccne.org/events-2004/dyno-2004/bad-dog.jpg
Thats 164rwhp at 9.8:1 CR on pump gas, not too shabby.
The N47 and presumably the P79 linered heads reportedly flow as well as square-ported heads stock, only drawback is you can't port 'em.
Me, I'd go the flat-top L28 route with the N42. If the chambers have sharp edges (never recall seeing anything particularly nasty in my N42), it shouldn't be any big deal to sand/grind 'em down. Otherwise, no mods whatsoever required, but of course you can shave a bit and/or use the 1mm gasket to get over 10:1 CR.
If you get a warm fuzzy from the heart-shaped P79 chambers, or are dissuaded by reports of detonation with the N-heads (never a prob for me) go ahead and shave that head, shim the cam towers, and use the longer N-head valves. If you shave .080" and use the 1mm head gasket, that puts you at 9.8:1, on a flat-top L28 bottom end.
Either way, I don't think I'd bother with a stock L26 bottom end.
Go here for all the bitterness regarding L-series cylinder heads
:http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=36702
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Oops, I screwed up, bending strength and stiffness will be reduced by 15%, not 12%. I was thinking 1/12*bh^3 instead of 1/4*pi*r^4 (DOH!). 15% is SIGNIFICANT. I wouldn't consider ANY reduction in journal OD, even for my engine with less than half the power you're aiming for. Like the equation says, moment of inertia varies with the FOURTH POWER of OD, so even removing a little costs a lot more in terms of strength and stiffness.
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Point is, it was FOOKING STUPID to go in there in the first place, and NOTHING can be done to fix that. So we have to REMOVE the STUPID FOOKS who put us there before they do something ELSE even MORE, well, you know...
IMHO
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Just so you know, going from 1.967" to 1.887" will reduce the bending strength of the rod journal by 12%.
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There's a time and place for this kind of criticism. IMHO... right now is the wrong time. .
Right now is EXACTLY the right time for any and all valid criticism of what's going on. This administration has been given a pretty much FREE REIGN and it's clear they're a bunch of f***-ups. No more should we stand idly by in the name of "patriotism" or whatever while our leaders take us further down the path to our ultimate DESTRUCTION!
(enough hyperbole for ya or do you want more
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"We know we can't count on the French. We know we can't count on the Russians. We know that Iraq is a danger to the United States, and we reserve the right to take pre-emptive action whenever we feel it's in our national interest." - John Kerry on CNN's Crossfire in 1997.
Never said I agree w/ Kerry. But I find it hard to believe ANYBODY could be as reckless with our military as Bush and krewe. FWIW I voted for Clark in the primary (voted for McCain in 2000).
How do we wind up with these dickholes?!
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SportZ2: "You really believe that Isreal is a stand alone country?"
That was sorta my point. We've supported them for long enough, time for them to be weaned off American tax payer dollars (not gonna happen of course), and let them stand on their own.
jmortensen
Wonders never cease! FWIW, I wasn't calling both sides EVIL outright, but evil CLEARLY is at work within them, as it is in our own country, and in our own hearts. To recognize that is to begin to be able to FIGHT evil (something which Bush and his cronies have no comprehension of).
Speaking of evil working within our country, John, what about the active Al Queada cells in our own country? Shouldn't we invade ourselves? I guess we ARE at war with ourselves when the exec. branch gives itself the authority to suspend all liberties of ANYONE it calls a "terrorist", regardless of any relevant evidence. If OBL/Al Queada HATE freedom, they must be pleased with the current administration, we're certainly well on our way to totalitarianism.
Anyway, I KNOW you don't *SERIOUSLY* think that Iraq contributed to any significant degree to Al Queada's horrifically successful attacks against us, do you?!
Vote for ME! (this is the first presidential election I'm old enough to run in)
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Killing how many Americans on American soil? Compare that with OBL/Al Queada. Iraq is a big screw-up priorities-wise. Besides, doesn't Israel have the means to defend itself? Evil amoral Palestinian suicide/homicide bombers vs. evil amoral Israeli helicopters launching missiles against old blind clerics walking out after their prayers, now THAT's a conflict I think we should stay the hell away from.
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UN Attacks Terrorism
in Non Tech Board
Posted
Invading Iraq has done NOTHING to prevent any of our citizens being murdered. Indeed, it has only ensured that MORE of our citizens will be/are being murdered.
Of course I fully support the US reserving our right to defend ourselves. That's not what we're doing in Iraq.