attn: SABSBENSON 3cyl help

[wing nut]

hey,

david L6 reccommended that i talk to you about 3cyl modificatons. im looking to free up the exaust as much as possible. i was told a 3-1 pipe may hurt low end so much that i wont be able to get on plane. i also was emailed a pic. from a 3cyl. hydro that has a little 90* elbow comming out from the bottom of the exaust plate of the motor. i need a way to make power. i will be using carburators alo bigger then factory so i need a way to ge the exust out FAST!

any help will be appriciated.

thanks,
scott

[Dave S]

Try a V4 :D

[Capt.Insane-o]

easy.;) :eek:

[Mark75H]

i was told a 3-1 pipe may hurt low end so much that i wont be able to get on plane

First thing I'd suggest is stop listening to whoever told you that. There is absolutely no truth in it at all. Ed Runne's 3 into 1 header box seems to work super well ... racers that I have seen run it love it and claim an 8 mph speed increase on 100 pound hydros (but I have not seen them using a GPS).

I also don't think you need to enlarge anything on the exhaust side of an OMC triple, even with bigger carbs. Tuning, not opening up. Since you are not racing under any special rules getting a bigger motor is by far the easiest and cheapest solution.

[wing nut]

im sticking with this size motor b/c i dont have the money for a bigger one, and because its more fun to beat someone with just a little 3cyl :)

there is going to be 3, two barrel carbs. on the motor with 5pedal reed cages. the only thing im concernd about is getting on plane.. after that its all top end. i was thinking of rigging up a "flap" on the end of the 3-1 pipes, it would be activated by a shifter cable up near where i sit. when im getting on plane the lever would be closed, and once up it would open it up, free up the exaust and haull ass :)

scott

[Mark75H]

Sorry, but it just doesn't work that way. You are not going to get more than 3 or 4 hp increase on the triple without spending enough money to buy a good used V-4 :( :( :(

[Dave S]

Well Wing, More power to ya. Keep tryin and learning, that is how we all got OLD;)

[wing nut]

Originally posted by Mark75H
Sorry, but it just doesn't work that way. You are not going to get more than 3 or 4 hp increase on the triple without spending enough money to buy a good used V-4 :( :( :(


there is already porting done to the block, im going to lighten the pistons adn rods, an balence them, add bigger carbs. and releive the exaust more. thats alot more then 3 or 4 hp.

scott

[Crab Claw]

Intake mods make the most power on the 3 cyl.
It will get on plane!! Don't worry!!!

[Crab Claw]

You should see 68 to 70 mph with a basic mod 3 cyl on the Vixen!
This would be with cut heads and some basic clean up work.
Sounds fast to me!!

[wing nut]

Originally posted by Crab Claw
You should see 68 to 70 mph with a basic mod 3 cyl on the Vixen!
This would be with cut heads and some basic clean up work.
Sounds fast to me!!


rite now im getting just about 60mph with an ol tired 3cyl. im hopeing for high 60's low 70's with the mod. motor. i have a head thats cut .080 for the motor also. ill keep every1 updated on the progress..

im still waiting to hear some info from sabsbenson.

thanks,
scott

[Mark75H]

you are more likely to get more speed by trying a few better props and blueprinting the bottom of the boat


Steve Benson builds motors for FE class racers, where the rules don't allow the bigger carbs, I kinda doubt he has any experience with what you are trying to do.

Again, relieving the exhaust is not going to give you any more power ... going over plane or top end ...the triple is a 2 stroke, not a 4 stroke

Your cut down head should give you a few hp and mph, it is definitly one thing that will work. I don't know how you are going to get really bigger carbs on that thing without spending mucho dinero that could just go into a bigger motor

Here is a picture of one of Steve's motors that probably pulls 100 hp or so - - - thru stock carbs

http://www.hydroracer.net/forums/attachment.php?s=&postid=10403

[Crab Claw]

A mod 50 intake, reeds and carbs would help. Alot!!!
But need to talk to Cees in Boxtel, Holand to find them. They're not in the USA anymore. Lots O Money too!!!

[Raceman]

"add bigger carbs. and relieve the exhaust more. Thats alot more then 3 or 4 hp."

That's not necessarily true. Bigger isn't always better. Just blindly increasing both the inlet and outlet may very well hurt instead of helping.

[Mark75H]

A mod 50 intake and carbs is going to cost as much as 2 running V-4's, those parts are not cheap!

[Dave S]

Make your own 2bbl intake by cuttin and welding the parts together. I ran against a 3cly in 1975 that had the 2bbl, I think the guy made it himself. You can pick up an old V4 135 for next to nuthing, you just have to know were to look.;)

[wing nut]

Originally posted by Dave S
Make your own 2bbl intake by cuttin and welding the parts together. I ran against a 3cly in 1975 that had the 2bbl, I think the guy made it himself. You can pick up an old V4 135 for next to nuthing, you just have to know were to look.;)


we are planning on cutting up a 2 barrel carb intake and grafting it onto my motor.


over all i really need the help on exaust. you cant say relieveing the exaust wont help b/c if im putting 2x as much air into the motor, with bigger and higher ports, that i wont benifit from getting the exaust out quicker and with less restriction.. it just doesnt make any sence to me.. unless im mising something?

will a 3-1 pipes out the side of the motor help or hurt performance? (with out all the chambers b/c i dont have enough money for them, and they are really hard to build.

scott

[Mark75H]

hurt

[race#115]

well from what i have read i think these guys are giving you good advise .I have done alot of tuning on two strokes and by changing the port hieght you can gain some peak hp but you will loose mid range plus the same goes for bigger carbs so it sounds to me like this thing will take the whole lake to wind it self up.plus building pipes takes alot of r&d just having open pipes i dont think will be ideal .the 49.9 omc has been played with for years with very good results i think you will get better results by doing the head cleaning the ports opening the exhaust at the gear case and spend lots of time on the bottom of the boat and prop work.

[P man]

From people Ive talked to (in terms of little pads anyways) their biggest gains came from blueprinting. I dont know how square your boat is but I was amazed by what ive heard. If you take the time and REALLY work the bottom, you will prolly pick up more mph then from any exhaust work.

[Mark75H]

Thanks Patrick & 115 ... It takes a lot of power to push a crooked boat. The same power pushes a straight and true boat faster and gets there quicker.

Here is one of the 2 stroke things you are missing:

The exhaust set up on your triple is a system. At 120º apart the timing between the cylinders acts as a reverse supercharger. Opening up the passages or separating the the exhaust passages with some kind of outside pipe arrangement will reduce or eliminate the exhaust reverse supercharging. The cylinder exhaust ports are open for only a fraction of each motor revolution .... the passages outside the ports are open all the time ... there is no restriction there.

Here is another:

Just doubling the carb and reed size won't come close to doubling the intake air flow .... a more realistic estimate would be a 10% air flow increase. The main intake ingredient is the piston sucking air into the crankcase. If the stock set up is 70% efficient (34ci of air per revolution) doubling the size is not going to give 68ci of air into the crankcase. Your doubling of carb and reed size will increase the air flow to something like 40ci per revolution. The 9 ci shortfall is more due to the crankcase and piston being an inefficient pump than the carbs and reeds being a restriction.

Look back at the numbers above. There is no way you are going to get more than 49ci of air into it no matter what carb/reed size you have without a supercharger.


Are ya "gettin' it" now?

[Crab Claw]

I've heard from a former racer that some times a stock motor with no pipes or porting is faster than a motor with the Blewy Pipes and ground out ports. Those Blewy Pipes sound fast though!!!

[Mark75H]

The Claw is correct. I am a current mod racer, often pure stock powerheads beat all out modified noisey motors for 3 reasons:

1) some mods just don't work

2) doing your boat blueprinting/set up homework pays off

3) spending money on the right prop is money well spent. The most powerful motor in the world is worthless with the wrong prop.

[P man]

Isnt that negative exhaust pressure theory also the reason a 4cyl rice rocket actually looses power with dual exhaust:D

[wing nut]

im starting to "get it" :D

ok to end the discussion about the bottom it was "blueprinted" when i re-build the boat. the bottom is compleatly straight, the pad was filled in and is now flat and straight as an arrow.

if the motor is ported, and bigger carbs/reeds are used what kind of gains am i looking at? also lightend pistons and rods, and .080 cut off the stock head.

scott

[Mark75H]

5 or 6 hp



Patrick they are way different...

On a 3 cylinder 2 stroke the pulse from one cylinder actually directly affects another cylinder with the initial primary wave. The 120º time between the cylinders' patterns synch's up with the exhaust duration of 145º or so giving a few degrees of overlap.

On a 4 cylinder 4 stroke car motor the exhaust pulses in their tail pipes are completely different, each cylinder is 180º apart from the one before and after it. If a street car motor had enough overlap for the next cylinder to directly affect it, it would have to have an exhaust open time of more than 180º and wouldn't pass emissions tests in Afganistan, much less here.

The 4 stroke's pipes help suck air out, the 3 cylinder 2 stroke's exhaust system pushes mixture - that has over run the cylinder and is in the exhaust passage - back into the cylinder and slightly increases the cylinder pressure.

[P man]

oh ok I just thought that cause a buddie of mine had a mustang v6 and out tech teacher always told him that he would gain hp with a single exhaust system.
That makes perfect sence though.
I know nothing about 4 stroke timing though:confused:

[wing nut]

Originally posted by Mark75H
5 or 6 hp





how do i here of these 100+hp 3cyl's then? what do you do to gain hp in them if intake, and porting, cutting heads, and lighting and balenceing the pistons and rods doesnt make much???

im not trying to sound like an ass.. i just wana know how i can make my motor one of the 100hp 3cyl's :)

scott

[Crab Claw]

How about some Nitrous. Got to be someone around here that knows about Nitrous. Works on V6s. Why not on a 3 cyl.

[wing nut]

i need to get the motor mod, and running good, then the nitrous comes in. i dont wana get nitrous untill the motor is tuned good.

scott

[Mark75H]

The 100+hp factory "mod 50" race motors have a big tuned exhaust log on the side, I think the passages are all the same size internally, but it sticks out the side farther ... and ... it is on the opposite side of the block. The only parts that are common with your motor are the crankshaft and pistons. I'm suspicious that the exhaust being moved to the other side of the motor has something to do with the rotation of the crankshaft interfering with the flow to the transfer passages.

Here's a picture, you can see, its completely different from your motor

[Dave S]

No wonder they beat Mercs, they cast up a new motor. Merc just used a 3 carb front and some lumpy pistons that like to FRY:D

[wing nut]

mark im talkin about a mod. 3cyl, not a mod50, that produces 100hp or more.. those mod 50's are retty sick though!

scott

[Mark75H]

Sorry, these ARE the mod 3 cyl motors that you were hearing about; Steve Benson's expansion chambered FE motors and the OMC CC and RS Mod 50's

There isn't any way to get that much power from 49 or 50 ci without going to those extremes

[delawarerick]

Dave S are you starting to see the light. Light being OMC. Rick:D

[Dave S]

Hi Rick, I hope you are doing OK. I think that the V4 is a very good starting point for a cheep high po boat setup. You can easly mod it and the heads come off so you can see those Big pistons.:p Just like a Merc V6, just smaller...........

[Travis Fulton]

wing are you still working in the triple??? wayne taylor just finished up a triple for me that probally makes 120+ hp but it dosent make it @ 10000 rpm's, more like 68-7k!!!!! it has fuel injection and a single chamber right off the exhaust plate! this thing is way badddddd!!! also steve benson just did a mod triple with big chrysler carbs and 3 pipes off the side, merc electronics, if you are using that 49 ci block you had pitch it and get a 56 ci triple preferably 87 or so with the bridge in the exhaust port, and the bigger the bore the better!!! try some big carbs!!! also bigger the better!!!! the motor cant ever get too much air!!!! it just needs what it wants when it wants it!! and the exhaust legenths are critical in conjuction with the porting so they work together!!! you need to talk tohire someone like wayne taylor to put the exhaust and ports in as he has done it and made it RUN!!! or anyone else that has done it,

[Mark75H]

Yeoowwwww, Travis!! Them is some big honkers!

[wing nut]

i still have the 49 c.i block and a ton of parts for it.. im thinking of getting like a 13ft cat to put it on:)

first things first though.. i need to get my boat running again!

scott
:p

[Laker]

Wing!
I love your thinking.
Bakers, Agnews and others have built some serious 3 cylinder Loopers. It can be done.
Keep up the good work and if you choose to step up to a V4 let me know!

[sasbenson]

Scott,

After viewing the rebuild photos I can see that you have put forth a lot of effort into this project and obviously are very serious about it , so I certainly don't mind taking the time to pass on some information which may be helpful!
If your budget will allow, the first modification I would consider is to find a 1987 or later 56inch 70hp "lostfoam" powerhead and start with that as a foundation as it is a big improvement over the early omc 3cyl engines. This powerhead will easily adapt to your midsection by simply drilling the mounting holes to 3/8 bolt size. The lostfoam block also has an excellent built in "pulse tuned" exhaust system which outside of fiddling with the "tuner" pipe, which is part of the adaptor plate between the powerhead and mid section, needs no modifications. Keep in mind that the mid section can also be a part of the "tuning" of the whole exhaust package!! After that, the way to increase performance is to improve the intake side of this engine and increase the compression ratio so you see 170-180 psi at cranking speed. Looking at your boat, I think you could easily reach the "safe" max speed of that hull with this approach. To see some radical modifications to a 56 block try this link to the hydro racer forum
http://hydroracer.net/forums/showthread.php?t=2047
Most won't apply to your application but you might get some ideas. Good luck on the project!

Steve B






:)

[Marhokka]

....1987 or later 56inch 70hp "lostfoam" powerhead and start with that as a foundation as it is a big improvement over the early omc 3cyl engines.
... The lostfoam block also has an excellent built in "pulse tuned" exhaust system which outside of fiddling with the "tuner" pipe, which is part of the adaptor plate between the powerhead and mid section, needs no modifications. Keep in mind that the mid section can also be a part of the "tuning" of the whole exhaust package!! After that, the way to increase performance is to improve the intake side of this engine and increase the compression ratio so you see 170-180 psi at cranking speed.


Can you tell the optimum rpm-band of this stock exhaust system: is it tuned for top power rpm or maybe lower?

How it will work at higher rpms, 6000 and over?