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Old 06-11-2008, 04:25 AM   #21
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This is true. I think it can be overcome pretty easily though. If you are doing an engine build, you might as well make her love the revs.

I mean, engine wasn't technically designed for boost either. Even if it does have a close relative whose was.

On the list of ultimate miata plans. Revs to 9k are on there. I figure head work to match the high flow manifold, and a new oil pump gear. See how it goes from there. I don't intend to run much more than 12 psi. Though this may increase if I do end up running ethanol..but that's really speculative and not probable at this point.
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Old 06-11-2008, 04:45 AM   #22
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Quote:
Originally Posted by patsmx5 View Post
I've got datalogs of my stock 99 motor at 7950. It wasn't floating. It wasn't pulling much either though. Still it wasn't valve float holding it back. I've had motors float valves at high RPMs. You know it when it happens. Motor will buck and backfire and basically hit a wall. It will refuse to go any faster.

Nothing on the motor supports making power in that RPM range. You can put Power-Card-Valve-Springs that don't float to 11ty Billion RPMs, but many aspects of the head, cams, intake manifold, and undersquare engine design will hold you back from making high RPM power. If you want more power, turn up the boost and bring DOWN the rev limit. IMO that's the road to reliable HP. A lot goes wrong at high RPMs. VE is downhill, friction is up, crank flex is multiplying, etc. For example if the motor would turn 9K it wouldn't make any measurable HP because the losses would be so high. You can fight them or you can work around them.
IDK how diminishing your returns would be esp if your turbo can breathe the cfm's you need to hold boost on a extended rev range and you dont run into a flow reversion in the intake ports caused by a backlash in pressure differential. Ultimatley this is a game of how much we can breathe in and out, if you have a nice clear inroute and a nice effecient out route then the frictionnal looses will be moot. IDK why you are so hard on crankflex pat, we have a forged crank already, and given a proper balance and some op gears that wont desintegrate at that high a rpm/vibration lvl etc, and a head that will flow what we need in and out, i see no reason why we cant make every bit of hp you dream of and more. You as always are being abit to problematic with your hp developement man. Alot of the funn of building a super high hp motor and realy testing it is finding out why things go boomb and fixing them better. We cant do the whole excercise on a spreadsheet calculating the force equations and resonant frequenqys as they effect the metals at varius temperature ranges.
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Old 06-11-2008, 05:58 AM   #23
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Quote:
Originally Posted by AbeFM View Post
Also, can I just pressuize the cyl, and pull the springs out from the top, or do I need to pull the head? I don't mind pulling it, but I've always wanted to try it that way.
Abe, Ive never really liked the idea of pressurising the cylinder to hold the valves in place. It does work and in most cases it works well, but if for some reason there is a slight leak and the pressure does release then the valve drops into the cylinder and you have to remove the head regardless.

A better method that I have used is to remove the spark plug from the cyl and rotate the crank using a socket on the pully nut so that the piston is at BDC then thread in loads of that cheap blue nylon rope through the spark plug hole. Force as much in as you can but remember to leave a tail that you can use to pull it all out with (dont ask me why I mention this) . Then turn the crank again untill it wont move any further and hold it in this position. I used a bungie on the end of my ratchet.

This will give you something nice and solid to push against without the risk of having to remove the head.

Cheers

Tom
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Old 06-11-2008, 11:06 AM   #24
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Old 06-11-2008, 12:02 PM   #25
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9K RPM, that's what I'm shooting for with my build.
The things you have to bring up to par.
-Rods
-OP gears
-rings
-bearings
-balanced rotating assembly (complete)
-cams/gears
-lots of headwork (the more the merrier)

Things in addition that will help further
-Knife-edged Crank
-shaved flywheel
reduced rotating mass iow
-Anything that will reduce friction and crank flex.
-Balance everything!!!
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Old 06-11-2008, 12:22 PM   #26
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Quote:
Originally Posted by Zabac View Post
9K RPM, that's what I'm shooting for with my build.
The things you have to bring up to par.
-Rods
-OP gears
-rings
-bearings
-balanced rotating assembly (complete)
-cams/gears
-lots of headwork (the more the merrier)

Things in addition that will help further
-Knife-edged Crank
-shaved flywheel
reduced rotating mass iow
-Anything that will reduce friction and crank flex.
-Balance everything!!!
see photo above your post.
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Old 06-11-2008, 12:38 PM   #27
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I will be building a 99/00 head...so yeah
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Old 06-11-2008, 02:17 PM   #28
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Quote:
Originally Posted by Duckie_uk View Post
Abe, Ive never really liked the idea of pressurising the cylinder to hold the valves in place....
A better method that I have used is to remove the spark plug from the cyl and ...Force as much in as you can but remember to leave a tail that you can use to pull it all out with (dont ask me why I mention this) .
Tom
That's one I hadn;t heard before. While a pain in the ***, it does seem like a good idea.

I guess you could put the motor at TDC, hold it, and use air pressure to hold the valves up, then if the seal breaks they only fall a cm. But that's not as clean as your method.


Quote:
Originally Posted by patsmx5 View Post
I've got datalogs of my stock 99 motor at 7950. It wasn't floating. It wasn't pulling much either though.
I agree in general that you want to work with the character of the motor, the squareness is certainly a factor, but if the rods will take it, you're fine.

I'm thinking with limited pressure driving it (no positive displacement (sc) or rising rate (tc + wastegate) air pump), your intake, throttle body, etc would all have been big factors, as well as the exhaust.

To a degree, the headwork must be an effect, clearly Mazda optimized it for sub-redline opperations, but that doesn't mean it can't be pushed further. The 99+'s have a much better head and I'm sure can be taken further. If you're not getting valve float, it means is doesn't hurt to try. It also means no need for springs yet.


Quote:
Originally Posted by Zabac View Post
9K RPM, that's what I'm shooting for with my build.
The things you have to bring up to par.
-Rods
-OP gears
-rings
-bearings
-balanced rotating assembly (complete)
-cams/gears
-lots of headwork (the more the merrier)

Things in addition that will help further
-Knife-edged Crank
-shaved flywheel
reduced rotating mass iow
-Anything that will reduce friction and crank flex.
-Balance everything!!!
Where does one get this OP ring? What does it cost, do they actually work? I'd heard of people putting them in and grenading anyway.

Cams would be the smartest thing to do in the quest for higher revs. Most of the rest is done already on my motor - pistons/rings excepted, I don't know what to do there. I guess get something lighter.

Someone on here, I forget who, MarkP maybe?, revs his motor to 8500, been doing it for a while. He makes quite a bit of power, and it doesn't look like the motor was starving up there. So, that set up, or Paul's, right now seem the best to copy as both are still pulling strong at 7+k
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Old 06-11-2008, 03:20 PM   #29
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Abe, you mean OP gears? I don't know what OP rings are.
The oil pump gears are for sale by Bill at Miataroadster I think, but hopefully we will have our own source soon, I am relying on it. There was a big team effort to get them drawn up and a few guys worked their butts of to get that done, now we are waiting on a machinist for a cost estimate, etc. not sure when they will be available.
As far as them shattering, it is a widely discussed topic and there is a ton of speculations out there as to what causes them to shatter.
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Old 06-11-2008, 03:47 PM   #30
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Quote:
Originally Posted by Zabac View Post
I will be building a 99/00 head...so yeah
and? they come with shim over lifters. that pic is a shim under lifter.
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Old 06-11-2008, 04:55 PM   #31
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I wasn't sure what you mean by that comment.
From what I read so far, the solid lifters in the 99-00 heads are much better for a higher rev limiter. Are you saying it's the opposite?
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Old 06-11-2008, 05:06 PM   #32
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I, too, and curious of the advantage of the PITA shim-under-lifter mod. It seems a small reduction in reciprocating mass...... Is there anything else about it?

Heck, V-tech motors reving to the moon have big head screw adjusters and rockers, so I am not sure I see the big deal.



OMG! Yes, keep me posted on the oil ring thing. I wonder if a stand alone oil pump couldn't be made for testing gears - run a stock one to failure with an electric motor, then the "improved" one.
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Old 06-11-2008, 05:15 PM   #33
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Abe, more testing? Go talk to Joe and make a video, haha
The Miata head is still a big mystery to me, damn lifters...
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Old 06-11-2008, 05:49 PM   #34
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the conversion is for two reasons mainly:

1. less reciprocating mass in the valvetrain
2. you wont spit shims out at high rpm.
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Old 06-11-2008, 06:06 PM   #35
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Matt, I like your sig. Could you do one for me? I'll polish the car, you tune mine till it has a dyno like that. :-)


Anyway, yeah - I can wiggle my shims out with (not inconciderable) effort without pulling the cams. Well, I loosen them. I have my doubts this would happen, but it's probably not a bad mod for a track beast.

Thankfully, the 99 head is pretty good, you can just run it, though a little deshrouding, etc, helps!
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Old 06-11-2008, 06:11 PM   #36
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So, in a 99-00 head you want to swap over the shim under lifter? I read that somewhere on Mnet, ****, it's back to reading now...thanks for the info y8s.
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Old 06-11-2008, 06:35 PM   #37
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Quote:
Originally Posted by AbeFM View Post
Matt, I like your sig. Could you do one for me? I'll polish the car, you tune mine till it has a dyno like that. :-)


Anyway, yeah - I can wiggle my shims out with (not inconciderable) effort without pulling the cams. Well, I loosen them. I have my doubts this would happen, but it's probably not a bad mod for a track beast.

Thankfully, the 99 head is pretty good, you can just run it, though a little deshrouding, etc, helps!
at high rpm... say if a valve floats or bounces... those shims get real loose real fast.
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Old 06-12-2008, 06:37 PM   #38
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Quote:
Originally Posted by AbeFM View Post
Heck, VTEC motors reving to the moon have big head screw adjusters and rockers, so I am not sure I see the big deal.
The big deal is because VTEC has a totally separate high RPM lobe with lots of duration, it can be designed for a slow ramp which means it can rev high despite a high valvetrain mass. Such a lobe profile would be terrible at low RPM, wihtout VTEC.
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Old 06-12-2008, 08:21 PM   #39
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Erm... Interesting. Sounds believable.

Although... My katana750, which revved to, I dunno, 12k or 14k or something, also had screw adjusters. And it idled just dandy. My lopiest idle was my old Kawi. You could argue the kan-a-tuna was giving up some top end, but it was making 98 hp on 1980 tech with only 750 cc's, so... There must have been some reasonable cams in there.

I'm just thinking maybe the mass in the head isn't such a big deal.

<edit>:
You figure, you've got 16 valves, total valves weight must be under that of just the rods or just the pistons. Then, they are going half the frequency of those parts. And to top it all off, they are moving like 1/4", not 4 inches.

Also, the shim-and-bucket is not light. They look very very stable, sitting all tight in that bore, but there have to be pumping losses and friction on the bore's circumference, etc. It seems to be the miata's set up would be more lossy than the honda's, even if it looks cleaner.

Show me a NA miata making 250 crank HP. :-)
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Old 06-13-2008, 02:41 AM   #40
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The problem with valves is that spring force sets the max closing acceleration - they might "ski jump" off the lobes if the RPMs are too high. Rods are pushed and pulled by the crank pin..
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