Dan Baldwin
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Posts posted by Dan Baldwin
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I'm running 45mm carbs with 39 (maybe 38?) chokes. This seems to be pretty ideal for my setup (.550"/~305deg cammed 3.1). The torque reaches maximum at about 4700, and doesn't begin to fall off until ~6000, peak power is at around 6500 (rev-limit at 7000rpm). The "How to Modify" book seems to imply that much bigger carbs are better for my setup, but I really don't think I'd want to go bigger, and would definitely consider 40mm/36mm venturis for a milder-cammed 2.8 street or autoX motor. For maximum power, 44s or 45s.
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setup in brief:
N42 bored and stroked to 3.1 liters
N42 head ported and cammed (.550"/~305deg) by Sunbelt in Atlanta
11:1 CR, 93 octane pump fuel
3x2 45mm OER Racing carbs, 38 or 39mm venturis
'84 truck 5-spd (3.321/1.902/1.308/1.0/0.833)
3.70 R200 LSD ('87 turbo)
dyno plot here if the image doesn't show up: http://www.classiczcars.com/photopost/showphoto.php?photo=6881&size=big&password=&sort=7&thecat=500
breakup above 6000 due to being forced to use points temporarily
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General rule regarding strokers is that you lose revs with the square root of stroke. i.e., if you increase stroke 10%, your rev limit should go down on the order of the square root of (1/1.1). So, theoretically, your redline would be reduced by a factor of 0.95. So you've gained 10% more torque EVERYWHERE, and only lost 5% of your rev potential.
Specifically regarding the L6 stroker, I limit mine to 7000 rpm. I am assured by a source at Nissan Motorsports that the 240SX pistons I'm using are regularly revved to 7500 in KA motors, which has a much longer stroke than a stroker L6. So they should be good for more than 7500 in a stroker L6. I'm also told that the stock L24 rods are good for 7500rpm in a stroker. I do not know what revs the forged diesel crank is good for, but I'm sure a properly prepared one could be made good for 7500.
I have made a 7200 rpm "pill" for the MSD, but I'm not planning on using it anytime soon. I think I'm being fairly conservative at 7000, I don't really feel the need to push it beyond that at the moment.
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That was my first ever run down the drag strip! Not too shabby, equalled Norm's best trap speed (way slower than his quickest ET)! I went with a friend from my time-trialling club. He's never beaten me on the road courses we go to (has been within a tenth, though) in his 260fwhp 2240 lb. Omni GLH-S. I think he figured to beat me at the drags. I won the first two rounds, but my trap speed was dropping as I was having fuel pressure issues, and he beat me on the 3rd and 4th runs (I still had a quicker ET on the 3rd run, SUCK reaction time, though). His best ET was 13.888 @ 107.56, best trap speed was 108.77 (14.097). Needless to say, he was having trouble hooking up:)
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His first name is Jason, but I don't have any contact info on him. If anyone can put me in touch with him I'd appreciate it.
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Go here for all kinds of cool and weird used Z wheels:
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The N42 and N47 280Z heads (44.6cc) will increase your compression compared to the '73 E88 head (47.8cc). N42 has square exhaust ports so you can use the exhaust manifold you have now. I've heard that notching of the block for valve clearance *may* be required to fit an L28 head (bigger intake and exhaust valves). Maybe something to check.
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FWIW, my radiator-shop 3-row 260Z radiator was sufficient to keep me from overheating on the grid at Watkins Glen for ~8 minutes in 85 degree weather (sumthin's wrong with my starter, couldn't risk it not starting for my time trial).
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'cuz the studs on the booster are too short.
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Another thing to consider is the RATE at which the flow area is increasing as the valve opens. I.e., absolute maximum lift might not be as important as quickly providing flow area, and quickly closing that area off. Stuff to think about, anyway...
Practice has repeatedly shown that high-flowing, big-hp engines want lots of valve area. I don't know of any direct L-series engine big-valve vs. small-valve comparisons, but it seems I've heard that L-heads are flow-challenged for big hp numbers. It only makes sense, if you're going to be modding for top-end power, to start with the bigger valves and mod from there.
Taking into account flow boundary layers, the difference in effective flow area should be greater than a straight ratio would predict (smaller flow area => thicker boundary layer => less effective flow). But even if the bigger valves really do only flow 5% more than the smaller ones, I'd still call that significant. I believe most people would rather have flow area via larger valves than via a lumpier, low-end-torque-robbing cam. So, price vs. price, it would seem to make more sense to install a big-valve head rather than spending similar or more money on a cam for a small-valve head.
But it IS a lot easier to install a mild cam than it is to remove and replace the head...
yr Devil's advocate,
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Unfortunately the adjusting tips don't just screw right off. I twisted the threaded rod in two trying to remove the short one from my old booster. It's got some funky looking locking threads. I'm certain that later 7/8"MCs are compatible with the longer tipped pushrod, I just need to know the exact years and if there's more than two pushrod+tip length/MC piston socket configurations.
Dan
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This is somewhat discussed in a topic below, just want to confirm something. When I went to 280ZX rear discs on my 240Z, a also put in the ZX 15/16 MC and a bigger-than-my-71's '72 ('73?)+ booster. I want to put a 7/8" MC back in, but my old one isn't compatible, it needs a much shorter pushrod from the booster.
So, are there just two configurations of booster pushrod length (long and short) and MC piston socket, and if so, should any 7/8" MC after '72 ('73?) work with my long-pushrodded booster?
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I've had good success with Bridgestone S03 Pole Positions. They should last over 20k miles if you don't heat cycle them to death first like I did. On my second set now. I've won my class time trialing with these tires vs. Kumhos, Hoosiers, etc. Probably about 1.5 seconds slower than Hoosiers at most tracks. They're great rain tires at the track as well.
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Here's my reply to Bob from that thread:.250" thick steel is WAY more then you need for any caliper on a 2' date='400 lb 240Z. The Outlaw 4 piston rears on my 240Z use a .125" thick, about 3" square peice of 4130 with small spacers to get the caliper centered over the rotor and I only use two of the backing plate mounting holes. You're dealing mostly with longitudinal forces. Every single aftermarket bracket I've seen designed for the Z is overbuilt.
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I guess you don't remember the spindly aluminum StrictlyZ rear brake brackets, yikes!
Without getting too far into it, just knowing the weight of a car isn't enough. And it isn't enough to know the thickness and material of a bracket to know the design is sound. Somebody QUALIFIED has to do an actual analysis to determine the structural integrity of a design. I have designed aluminum brake brackets, and I have designed steel brackets where there wasn't enough space to get adequate strength in aluminum.
Reading through this thread, it's interesting to note how sensitive people can be to a little constructive criticism. But designing and selling critical brake hardware is serious fricking business. In my opinion, if a design hasn't been subjected to at least a rudimentary engineering analysis, it doesn't belong on the market. Same for critical suspension and chassis hardware.
Again, the question isn't whether or not 1/4" is thick enough, or whether 4130 steel or 2024-T6 (I assume the Brembo guy wasn't referring to T0!) aluminum is the "right" material, it's whether or not the overall design was conducted based on sound engineering principles. I'd rather have a balsa wood bracket proven by sound analysis than chrome-moly steel or aircraft aluminum that wasn't. (ok, maybe I exaggerate...)
And it's NOTHING PERSONAL! I wouldn't let someone without an M.D. perform my needed lobotomy, either, no matter how enthusiastic and well-meaning they are.
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My understanding was if the rear tire pressure is optimal, then having slightly low pressure in the front will decrease the effective front contact patch size under load reducing grip and hence in this scenario getting the car closer to neutral handling. Am i missing something?
Reducing tire pressure INcreases contact area (contact patch area is roughly the load on the tire divided by the pressure). But that doesn't mean cornering grip is increased, usually the opposite with street tires at street-normal pressures. Maybe if you tried something like 32 or 34 in back and 30 or 28 up front, rather than reducing front pressures. Removing the rear sway bar might be a good thing to do if oversteeriness persists. Are the Eibachs progressive-rate springs? You might be better off, handlingwise, with linear rate springs, as that would reduce your initial roll rate in cornering, and reduce your total roll for a given level of cornering gs.
Don't be shy to remove the rear bar if other methods fail to fix your understeer condition.
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Dealer cost on that part is $660! Luckily for me, the shop that did my rebuild had one laying around, barely used (they went all dry-sump). $200 to me, all cleaned up and brand new looking, tee hee hee!
Would an accusump solve your problems?
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Thanks for the kind words! In reverse order,
I've got a stock (LOW breakaway) 3.70 LSD, and a newly installed rebuilt '84 truck 5-speed. This is likely the best stock Nissan 5-speed for roadracing: 3.321, 1.902, 1.308, 0.833. Man I'm glad to be rid of the super-tall ZX 5th gear! I don't see myself in the 11s anytime soon, btw. My main interest in going to the drags would be to see what kind of trap speed I could get. I'm too much of a candy-ass shifter to be really quick, I'm afraid. Not to mention I've no idea how to launch.
Norm,
running the numbers, I guess I should be good for at least 110, but I don't know if I believe it! Guess I'll have to make a trip to NEDragway soon. I don't see low 12s with me behind the wheel. Maybe mid-13s. Let me know if you're ever in New England and maybe we'll see what you can do with it (just don't BREAK it!)
Pete,
I think I'm sort of a wuss on brakes as well. BobH certainly was underwhelmed at VIR! Maybe next year... I plan on doing all the NHIS COM events, plus the Glen and Lime Rock. Hope to see you solo there. I spend $170 for an hour and a half at the dyno. I think the rate is $150/hour with A/F. Pretty steep compared to $40 for the bike here in New Bedford. Didn't know you could pay extree for an expert, but I don't think they have a 3x2 carb expert anyway. I like 'em there, too. Should be getting data files from them soon, will post.
More (plots) to come!
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I went to New England Dyno on Saturday, with my rebuilt 3.1 liter. Results were, to say the least, beyond my expectations. Based on the small displacement bump and increased compression ratio, I expected at most an increase from 235rwhp to 245.
Current setup is:
89.5mm bore/83mm stroke, 3133cc (up from 3098cc)
11.1:1 calculated/10.8:1 measured-volume CR (up from 10.74:1 calculated)
N42 head with cam setup, porting, and modest cc reshape by Sunbelt
3x2 45mm OER Racing carbs
My 280Z magnetic pickup distributor failed on Friday afternoon, so I had to put my 240Z dizzy and points (new/unused) in. Worked fine up to 6250rpm, beyond that points bounce pretty much ended the runs. Fortunately peak power looks to be right around 6250, but there may be a couple of additional ponies up there!
After doing a few runs on pump gas, playing with jetting and then timing, I did three runs on VP C11 fuel (104 motor octane, ~107 (R+M)/2?). These runs were well below the runs on pump gas, with maximum hp made with about 4 degrees more advance compared with the pump-gas runs. What this tells me (other opinions welcome) is that my "detonation-prone" open-chambered N42 has no issues running on 93-octane pump, at close to 11:1 CR.
The mixture curve (and, consequently, the torque/power curves) are a bit of a roller-coaster, going from 13:1 at 3000 to 10.25:1 at 4500 to 13.3:1 at 6300. Yuck. I still have carburetion issues below 3000, I had to ease on the throttle to keep it from bucking too badly beginning the runs.
1: 251.8 (165 main, 200 air jets; ~15 initial/34 max advance)
2: 254.8 (160 main, 190 air jets; ~15 initial/34 max advance)
3: 253.0 (165 main, 190 air jets; ~15 initial/34 max advance)
4: 241.6 (165 main, 190 air jets; ~19 initial/38 max advance)
5: no data
6: 245.2 (165 main, 190 air jets; ~11 initial/31 max advance)
7: 237.1 (VP C11; 165 main, 190 air jets; ~15 initial/34 max advance)
8: 243.0 (VP C11; 165 main, 190 air jets; ~19 initial/38 max advance)
9: 237.0 (VP C11; 165 main, 190 air jets; ~23 initial/41 max advance)
Whaddya think?!
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Weight distribution would SUCK with a transverse fwd-based setup. The engine would be entirely in front of the front wheels. Doubtful you could fit it, anyway. I kinda wonder if the benefits of even a well done longitudinal-engine awd setup would be enough to compensate for the weight gain and forward c.g. shift (road course usage). Rwd more fun anyway:)
Just bein' my usual nay-saying self!
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I think we were talking about stock Vipers, but give me $40k (and a year). I wouldn't guarantee anything, but I think with the right people (engineers, techs, drivers, etc.) involved, it's certainly well within the realm of possibility to run with or beat the fastest T1 cars, given that there are no restrictions (on the Z).
Of course you have to consider at what point it is no longer a Z!
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Stock Viper vs. modded NA, pump gas, 6-cylinder Z (under $15,000)? Z wins!
http://www.comscc.org/results/nhis0802.htm
http://www.comscc.org/results/nhis0902.htm
http://www.comscc.org/results/nhis1002.htm
http://www.comscc.org/results/lrp_1102.htm
Note, for the August NHIS event, I had POORLY tuned 2" SUs with a big retarded cam, = no midrange and no top end, either. After that I had 45mm 3X2s. The October NHIS event was in the rain. No Viper in the Lime Rock event (he crashed), I included it anyway cuz I set FTD (fluke)!
Stock Z06s are slow, too;)
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Rebuilt motor runnin' GOOD, though I did get reports of trailing exhaust smoke coming out of 3, hmm... It is nice for the oil pressure not to take a dive during right-handers. Competition pan is just what the doctor ordered. $200 used, deal of the century!
Corner workers in 6 said I was fastest on the track in Group 1 (experienced big-bore). Wheee! That was after putting the Hoosiers on. First two sessions I spun due to street tires heat cycled to death (couldn't be MY fault, right?). Gotta start saving the street tires for wet track conditions. Which means I'll be using up Hoosiers more quickly. $$$$$
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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 high revs, or high boost and lower revs. For maximized power you'd want to maximize boost and revs (big turbo(s), big intercooler). Right?
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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.
Rotary Valve Heads!!!
in Miscellaneous Tech
Posted
This has been done before. I "invented" this back when I was a co-op at Martin Marietta in New Orleans in 1988. The older British guy who sat next to me informed me that this had been done at various stages in ICE history. Some European automaker (Renault?) had a rotary-valved W-configured engine more recently, in the mid-90s. Nothing new under the sun, eh! It does seem to have a lot of potential. D.L. Potter once told me and a group of Georgia Z-club guys that an L-series valvetrain requires 150hp at 7000 rpm! So seemingly outrageous hp increases *might* be *theoretically* possible with this concept. Apparently it just isn't practical/practiceable. Yet. The piston ICE, she no dead yet!
P.S.: You want I should send your gloves to your home address, Bob_H?