SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: JS44SDS on September 13, 2014, 12:43:54 PM
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Hello guys,
I am new here and have a question I have been looking for for a fair amount of time. If you have a sbc with say 400hp how much gain would you see using a set of say CMI E-top water jacketed headers. I know dollarwise the logs are much cheaper-I just want to know the approximate HP advantage with Glenwood log manifolds, Stainless Marine center Risers (or equivalent), and a CMI Etop water jacket header. Your input would BE GREATLY appreciated.
I found this but didn't get a real feel for the advantage HP wise you would see.
http://www.socaljetboats.com/engine-mechanical-electrical/water-injected-vs-water-jacketed/ (http://www.socaljetboats.com/engine-mechanical-electrical/water-injected-vs-water-jacketed/)
Thanks in advance,
Scott :)
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First off, welcome to the forum
Second... Well... typically, an engine would not be dynoed with log manifolds. In my dyno experience, typically a set of dyno headers would be used. Sometimes, if they would fit, the customer’s exhaust was tested. Regarding the amount of horsepower of said SBC, a lot would depend on the tests and how they were run. I don’t think that it is possible to run logs during a dyno test, at least not the aluminum logs. If said SBC made 400HP with dyno headers, log manifolds would yield substantially less horsepower. I have heard claims regarding the flow capabilities of the center riser manifolds and in looking at their design, I agree that they are an improvement over logs. I just can not believe that they are on par with a good set of headers.
My thoughts on this are: They do not have smooth contoured bends, especially at the all important departure angle at the head flange, where the exhaust transitions from the port into the primary tube/port (in the case of manifolds). The cross-sectional shape is inconsistent and allows for gaseous expansion at various places. This causes the gasses to lose velocity in the areas of expansion and causes pumping losses in areas where the gasses are forced to increase velocity. I don’t see much intentional tuning with the cross-sectional area. The lengths of the ports are short and are combined with a collector area that is less than ideal. Lastly, the inner surface is rough and increases surface friction and therefore restricts flow.
In certain automotive racing classes requiring exhaust manifolds, significant gains can be made by porting the manifolds. The majority of work is concentrated in the flange area so that no part of the manifold covers the port in the head. Actually, an intentional mismatch where the port in the manifold is larger than the port in the head helps to prevent reversion and intake charge contamination. Unfortunately for us as boaters, the largest gains with manifolds occur with the merge collectors of the exhaust pipes merging into a single exhaust. This type of system will provide the best scavenging with a manifold; however I do not see a way to incorporate this type of system into a boat. I suppose that you could do an OT setup, but in my opinion, a good header setup will make more power.
Sorry for the long winded reply, in short, I don’t think that you would feel a difference, there might however, be a measurable difference. You will also have to re-jet your carb to realize any difference at all.
Good luck,
Joe
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First off, welcome to the forum
Second... Well... typically, an engine would not be dynoed with log manifolds. In my dyno experience, typically a set of dyno headers would be used. Sometimes, if they would fit, the customer’s exhaust was tested. Regarding the amount of horsepower of said SBC, a lot would depend on the tests and how they were run. I don’t think that it is possible to run logs during a dyno test, at least not the aluminum logs. If said SBC made 400HP with dyno headers, log manifolds would yield substantially less horsepower. I have heard claims regarding the flow capabilities of the center riser manifolds and in looking at their design, I agree that they are an improvement over logs. I just can not believe that they are on par with a good set of headers.
My thoughts on this are: They do not have smooth contoured bends, especially at the all important departure angle at the head flange, where the exhaust transitions from the port into the primary tube/port (in the case of manifolds). The cross-sectional shape is inconsistent and allows for gaseous expansion at various places. This causes the gasses to lose velocity in the areas of expansion and causes pumping losses in areas where the gasses are forced to increase velocity. I don’t see much intentional tuning with the cross-sectional area. The lengths of the ports are short and are combined with a collector area that is less than ideal. Lastly, the inner surface is rough and increases surface friction and therefore restricts flow.
In certain automotive racing classes requiring exhaust manifolds, significant gains can be made by porting the manifolds. The majority of work is concentrated in the flange area so that no part of the manifold covers the port in the head. Actually, an intentional mismatch where the port in the manifold is larger than the port in the head helps to prevent reversion and intake charge contamination. Unfortunately for us as boaters, the largest gains with manifolds occur with the merge collectors of the exhaust pipes merging into a single exhaust. This type of system will provide the best scavenging with a manifold; however I do not see a way to incorporate this type of system into a boat. I suppose that you could do an OT setup, but in my opinion, a good header setup will make more power.
Sorry for the long winded reply, in short, I don’t think that you would feel a difference, there might however, be a measurable difference. You will also have to re-jet your carb to realize any difference at all.
Good luck,
Joe
Ya, What he said^^^^^^^^^^^^^^^!
I would add that HP wise it could be 45 hp or so, but depending on the boat your using, the difference in performance could be 2-5 MPH with a well set up hull, or virtually nothing in a family boat that most of us have. Headers would probably give you a better throttle response, maybe a couple more RPM, but your hull is going to be your biggest determining factor to performance gains.
In English, is it worth 2K for a set of CMI's just to get rid of your logs? Not unless the rest of your boat is pretty well dialed in and you need another 5MPH. JMO.
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I had my BBF built last year and have thru bolt logs... My pump has some mods as well. I have a heavy hull but still picked up speed an performance with the logs.
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1st off-thanks for the welcome and time for your responses. I do not have a jet boat but something a bit different. I joined here specifically because there was a thread that asked a similar question and knew jet boat owners DO use log manifolds like my type of hull which is a Jersey Speed skiff-kinda like the east coast version of a cracker box but has some major differences. My boat weighs around 1650 ready to go SO our hulls love RPM and do NOT like a lot of torque so you do not see Big Blocks in them or long stroke SBC's. Most use logs as they are mandated by APBA in competition use.
Yea, I know the CMI's are 2k but if I could regain 35-40 usable horsepower I would definitely consider it...as 35-40 HP in a skiff is a fair amount. Competition boats run 283's and make around $325 hp and do around 80 mph. Mine is a little more stacked under the hood.
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First off, welcome to the forum
Second... Well... typically, an engine would not be dynoed with log manifolds. In my dyno experience, typically a set of dyno headers would be used. Sometimes, if they would fit, the customer’s exhaust was tested. Regarding the amount of horsepower of said SBC, a lot would depend on the tests and how they were run. I don’t think that it is possible to run logs during a dyno test, at least not the aluminum logs. If said SBC made 400HP with dyno headers, log manifolds would yield substantially less horsepower. I have heard claims regarding the flow capabilities of the center riser manifolds and in looking at their design, I agree that they are an improvement over logs. I just can not believe that they are on par with a good set of headers.
My thoughts on this are: They do not have smooth contoured bends, especially at the all important departure angle at the head flange, where the exhaust transitions from the port into the primary tube/port (in the case of manifolds). The cross-sectional shape is inconsistent and allows for gaseous expansion at various places. This causes the gasses to lose velocity in the areas of expansion and causes pumping losses in areas where the gasses are forced to increase velocity. I don’t see much intentional tuning with the cross-sectional area. The lengths of the ports are short and are combined with a collector area that is less than ideal. Lastly, the inner surface is rough and increases surface friction and therefore restricts flow.
In certain automotive racing classes requiring exhaust manifolds, significant gains can be made by porting the manifolds. The majority of work is concentrated in the flange area so that no part of the manifold covers the port in the head. Actually, an intentional mismatch where the port in the manifold is larger than the port in the head helps to prevent reversion and intake charge contamination. Unfortunately for us as boaters, the largest gains with manifolds occur with the merge collectors of the exhaust pipes merging into a single exhaust. This type of system will provide the best scavenging with a manifold; however I do not see a way to incorporate this type of system into a boat. I suppose that you could do an OT setup, but in my opinion, a good header setup will make more power.
Sorry for the long winded reply, in short, I don’t think that you would feel a difference, there might however, be a measurable difference. You will also have to re-jet your carb to realize any difference at all.
Good luck,
Joe
Thanks for the info. I just used 400hp as a bench mark as to whether you would gain "X" amount of hp with the center riser and then the header over the LOGS as that is our benchmark as thats what 99% of our boats use. I realize set up and hull type make a difference but was just looking for the basic benefit of the move up in exhaust systems as I always wondered if the water in a wet exhaust negates some or all of the gain by using water jacketed headers. I have ideas about it BUT that's just bench racing and just an opinion...I know somebody had to do the dyno work as I never believe the claims of the manufacturers. A pic of my boat so you guys have an idea.
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Okay, now we are going to need pictures!
Sent from my SCH-I535 using SoCal Jet Boats mobile app
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Figures, now the pictures
Sent from my SCH-I535 using SoCal Jet Boats mobile app
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Figures, now the pictures
Sent from my SCH-I535 using SoCal Jet Boats mobile app
So guess my question is unwelcome since I do not own a Jetboat? If so it wasn't my intention to offend-if it pleasure you ban my account...was just looking for some info. that I found here which I appreciate. :)
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Thanks for the info. I just used 400hp as a bench mark as to whether you would gain "X" amount of hp with the center riser and then the header over the LOGS as that is our benchmark as thats what 99% of our boats use. I realize set up and hull type make a difference but was just looking for the basic benefit of the move up in exhaust systems as I always wondered if the water in a wet exhaust negates some or all of the gain by using water jacketed headers. I have ideas about it BUT that's just bench racing and just an opinion...I know somebody had to do the dyno work as I never believe the claims of the manufacturers. A pic of my boat so you guys have an idea.
That thing is sweet!!!!!!!
Sent with my Fingers
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That was in reference to my POS cell phone. Sometimes the square indicating where a picture is loading doesn't show up on my phone and I didn't see that you already posted a pic before I stuck my foot in my mouth.
What you are doing sounds really cool and I would love to see more pics. Variety is the spice of life and I still welcome you and what you are doing.
I'm sorry I don't see the kind of gains from the exhaust that you are looking for. I will look for the website with info on porting exhaust manifolds when I can jump on my PC.
Cheers,
Joe
Sent from my SCH-I535 using SoCal Jet Boats mobile app
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So guess my question is unwelcome since I do not own a Jetboat? If so it wasn't my intention to offend-if it pleasure you ban my account...was just looking for some info. that I found here which I appreciate. :)
i dont own a jetboat either. O0 i have center rise exhaust. obviously nothing will beat a set of tuned headers... but then again no one wants to deal with water injected or dry headers these days let alone trying to get them insured.
a set of lightning water jacketed headers are gonna be upwards of $2500 new... imco power flow center rise you're lookin at only $1800 for a sbc. performance is gonna be better with the headers since they're seperate tubes all the way to the collector, whereas the center rise is just to the riser. but is it worth the extra $700 for realistically 10-20hp?
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That was in reference to my POS cell phone. Sometimes the square indicating where a picture is loading doesn't show up on my phone and I didn't see that you already posted a pic before I stuck my foot in my mouth.
What you are doing sounds really cool and I would love to see more pics. Variety is the spice of life and I still welcome you and what you are doing.
I'm sorry I don't see the kind of gains from the exhaust that you are looking for. I will look for the website with info on porting exhaust manifolds when I can jump on my PC.
Cheers,
Joe
Sent from my SCH-I535 using SoCal Jet Boats mobile app
::) Now I feel like a d$$k-sorry for assuming too much...much appreciated for the help.
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i dont own a jetboat either. O0 i have center rise exhaust. obviously nothing will beat a set of tuned headers... but then again no one wants to deal with water injected or dry headers these days let alone trying to get them insured.
a set of lightning water jacketed headers are gonna be upwards of $2500 new... imco power flow center rise you're lookin at only $1800 for a sbc. performance is gonna be better with the headers since they're seperate tubes all the way to the collector, whereas the center rise is just to the riser. but is it worth the extra $700 for realistically 10-20hp?
How much better HP/% gain will you see on a imco power flow center rise versus a Glenwood log manifold. If I found either the center rise or the Jacketed headers I would buy used IF a set came up and it did something for the boat...I am contemplating redoing the boat and want to do something different in a Skiff-and Jacketed headers have only been used once or twice. NOT ME OR MY BOAT but this is how we can turn.
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How much better HP/% gain will you see on a imco power flow center rise versus a Glenwood log manifold. If I found either the center rise or the Jacketed headers I would buy used IF a set came up and it did something for the boat...I am contemplating redoing the boat and want to do something different in a Skiff-and Jacketed headers have only been used once or twice. NOT ME OR MY BOAT but this is how we can turn.
getting an exact percentage is never gonna happen. every motor is different.
LIGHTNING HORSE POWER COMPARISON
Performance figures on headers vary considerably. As a rule, the higher horsepower engines benefit more than the lower horsepower engines. For example, the 330 hp Mercury engine will gain approximately 50 to 75 rpm, where as the 365 hp Mercury engine will gain approximately 300 to 400 rpm (45 hp). Blown engines gain up to 800 rpm (80 hp). Of course this is comparing these headers against stock Mercury center rise manifolds.
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getting an exact percentage is never gonna happen. every motor is different.
That give me a fair idea...not to beat a dead horse BUT is a Glenwood log manifold BETTER than a stock Mercury center rise manifold? I really appreciate the help in trying to get a fair grasp on the topic.
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If you can find a used set of Harman marine(not Hardin) its a way better log as they have water jackets up around ports. The ford benefits from this more but still one of the best made.
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NOT ME OR MY BOAT but this is how we can turn.
That's why I love boat racing... Because all other sports require only one ball