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Thread: 300R vs 300X
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05-27-2019, 10:23 AM #76
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05-28-2019, 06:12 AM #77Screaming And Flying!
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05-29-2019, 06:59 PM #785000 RPM
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Hopefully flow bench numbers and specs from cam doctor will be shared once someone disassembles one, anyone know SCR of these new V8s? Imagine it’s fairly low being it’s port injected and tuned for 87 octane.
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06-01-2019, 10:05 PM #79
Only thing Merc shows is bore and stroke .. something close my program showed was a 4 valve bent 6 Beemer that I had to bump the numbers around a little to get it to peak a little over 300 @ 6400 ish.
It was easy to get it to make 250 or 500 .. LOL
I still think I have too much intake valve diameter and duration .. but, I think the rest is close
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PRE-Z06 liked this post
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06-02-2019, 12:22 PM #80
LMAO ... C5 - ZR-1 .. instead of hitting the like button, you should have said :
Hey dummie , it's a bent 8 .. not a 6 ...
Reconfiguring ...
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06-02-2019, 12:39 PM #81
Well everything else staying the same, just dividing into two more holes was worth 80 HP ...
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06-02-2019, 02:33 PM #825000 RPM
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06-02-2019, 04:25 PM #835000 RPM
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I was applauding your efforts at plugging in guesses to the dyno simulator, but it’s still speculation as I can’t even find compression ratios on the new V8s. Why the guess of a reverse split cam? I doubt the overlap is that great as it doesn’t sound that aggressive in my humble opinion and would think it needs help on the exhaust side as assume outboard exhaust are more restrictive.
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06-02-2019, 09:33 PM #84
Your right , it's backwards ... it was late , I was tired , the sun was in my eyes ..
I meant for it to be a church steeple intake. high lift short duration to build cyl pressure.
Hang the exhaust open, it don't hurt nothin and it avoids pumping losses. On the T/D stuff blown or 700+ inch nitrous we left the ex open 300+ degrees .
And yes, no doubt, a poor outboard has to blow that **** out into some pretty thick air (water) and needs all the help it can get. I think I had it that way a couple times , even a few times LSA at 106 and as wide as 116 installed @ 110 . Garbage in , garbage out some of it .. but most all cases that peak between 6 and 6400 seem to make 450 ft/lbs @ 3000 LOL
I've put the compression @ 8 and 9, I would imagine thats where thay would put it not knowing if John Q. Customer is going to put the motor on a heavy azz hull , a big prop and lug the pizz out of it the whole time it's under wty ..
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06-03-2019, 07:37 AM #855000 RPM
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Agreed compression is probably similar to Verado’s 8.35:1 even though that engine is supercharged it’s supposed to run on premium fuel and they just pull timing if someone puts in the cheap stuff. Low compression, a late IVC and a relatively speaking poor exhaust is going kill torque. The 4-stroke makes more “bottom end torque” (40% more at 2k rpm) mainly because of the increased displacement over the 2-stroke, don’t think they’re peak numbers are that much different. Though that’ll help a heavier hull and the production boats just like cars don’t seem to be getting lighter these days unfortunately.
The Grump mentioned in the article below he was hanging the exhaust valve open on his bigger NA small blocks for more than 300* @ .050” though he was turning 9k+ rpm
https://www.scribd.com/doc/110755831...e-Bill-JenkinsLast edited by PRE-Z06; 06-03-2019 at 07:44 AM.
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06-04-2019, 11:03 PM #86
Yea , a 355 was big to him .. LOL
But if we look at combustion and the exhaust event on a 2 stroke or 4 . We see they both start out with 20 to 30* degrees of advance to peak the cyl pressure around 14* degree ATDC . And both will see the party being over by 90* degrees ATDC.
A 2 stroke will open @ 90* and stay open thru the entire transfer event and of course close 90* BTDC.
A 4 stroke with something like a Comp 280 hyd / flat tappet ( mild ) is 230* @ .050 but follows the same pattern .. Opens @ aprox 90* ATDC , it's fairly empty by the time it gets to BDC ( pressure wise ) and as stated, no need in closing it for the ride up 180* + 90 = 270 + 10* over the top to help pull some of the fresh charge and you have 280* degrees on a really mild cam, seat to seat. It's a lot easier to measure them @ .050 lift so thats what the industry does. But in the real world the valves are off the seats and leakin ten each way from bein sealed up. Fer me datz dayum near 300* degree's ..
Chaz = thinkin last week ZR-1 ain't even no who the cigar man even wuz ..
*yes I know, sometimes more, sometimes less ..
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06-05-2019, 07:23 AM #875000 RPM
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Ramp rates vary so much off the seat that .050” is a better comparison than advertised numbers as heads aren’t even allowing much airflow at such low lift. Marine lobes are soft/slow for extended higher rpm use obviously so advertised (.006”) duration is higher than normal cams. A 2019 production engine has to succumb to emissions which makes my guess that intake duration is low and lsa is wide to make it as efficient as possible by exhausting as little unburnt fuel from no overlap. For reference the last NA 4.6L DOHC Ford from 15 years ago that had to comply with the EPA (so similar size, power and rpm as mentioned early)...
Intake: 184 deg @ .050/.394 lift
Exhaust: 196 deg @ .050/.397 lift
114 lobe center
If we assume we can get 1hp for every degree of intake duration added, then there will be some nice gains to be had with hanging the valves open longer to ingest more air assuming the intake and exhaust can keep up. Hopefully this becomes the LS of outboards one day and maybe the Merc will make be more like this engine...
https://www.enginelabs.com/news/volv...percar-opener/
The Z06 came out in 1963 as I’m sure you know, I chose the screename because I had ‘99 FRC that everyone thought was a Z06 because the body looked the same. My late uncle had a 327 4-speed Camaro in the ‘70s and taught me a few things when I had the Vega, he for sure knew who the Grump was. Here’s a cam from a little 12:1 358ci engine when I worked at Team Texas that had over 300* advertised duration...
LH-(YF3E 6A273 BB)
Exhaust: 196 deg @ .050/.397 lift
114 lobe centerLast edited by PRE-Z06; 06-05-2019 at 10:11 PM.
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06-05-2019, 07:55 AM #88Screaming And Flying!
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so you get you carby OMC 200, take it apart and grind on it and you have 300 with the cost of a gasket set
hows the 4 stroke cost compare with that to add 50% or 100HP?
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06-05-2019, 08:21 AM #89Supporting Member
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Compression, cams, and tune are to come and you will be able to add 50% more h.p.-Unfortunately for those that want to keep living in the 80s, you will miss the smoke, the stalling, the shaking, the narrow power band, the lack of torque and the high fuel usage. These motors are going to make a common 400+ h.p., turn 7000, and have a 1.60 gear which will turn anything that you can currently bolt a 3L motor on the back of "a candidate for big time performance". The only downside to this new technology is cost but the good thing is that dollars are the one thing that we all can make more of.
Joe
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06-05-2019, 08:54 AM #90Screaming And Flying!
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I am amazed Merc lets punters hack the PCU and BRP worked hard to prevent it.
I wonder how the EPA views that?
narrow powerband of a 2 stroke versus a 4 cam 4stroke?? Those 2 companies that tried to get a 4s to replace the the F1 v6 needed your help.
It might be different once they use VVT and a blower
I am starting to wonder whats the point of a huge horsepower performance outboard, 160mph in an Allison or will it be 100mph in a Hatteras?
Look what happened to the Stern Drive business, pushed it to almost 2000hp and then it died, was there a market or use for the product?
I have noticed when people are selling modern engines and they post the ECU dump of the % rpm, 99 times out of a hundred they spend 90% at idle and less than 1% at WOT, just saying....Last edited by powerabout; 06-05-2019 at 09:36 AM.
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