Toyota V8 Exhaust Pipes Length/Size

[melvinmelvin]

When floods are over and things back to normal I will put my longtail through a major upgrade.

Among other things I will install a new engine.

I have put my eyes on one of the following;

a) Toyota 4500 cc V8 diesel

Toyota 4700 cc V8 benzine

preferrably a) if I can find it in the 2nd hand market.

My ambition is to have one of the (if not the) fastest boat on Chao Praya.

Hence, I will have to go through a lengthy period of testing various propellers and shafts.

During this test period I will run the engine with open/free exhaust, no muffler. (Easier to swap shaft.)

(The only way (I can think of) to support the weight of a muffler would be by rods resting on the tube/pipe for the shaft.)

(What do you call that propeller tube in English?)

So initially I will just weld on some larger pipes to the manifold pipes.

My thinking so far is 1 pipe for every 2 cylinders. That is 2 pipes on each side of the engine.

I would like to have the engine performing as close to its maximum as possible while

I work to sort out length of shaft and the propeller size, blades/diameter/pitch.

What would be a good diameter for the exhaust pipe for 2 cylinders?

(I was thinking of 3 inch)

Same same for both a) and above or different?

What would be a good length for the exhaust pipe?

(I think I know the theory behind the optimum length when the engine runs at its maximum, but I don't have the equipment

and I don't have the knowledge to fiddle with this.)

Any views on the length?

Does it matter at all?

(The pipe cannot be too long since it will not have any support for its weight, other than the weld.)

If it doesn't matter I'll just weld on a meter or so to the manifold so that the gas and the worst of the noise disappears astern.

In advance thanks for any views.

Edited February 14, 2012 by Crossy

[melvinmelvin]

hmm,

weird, the smileys should really have been , I surely typed but it ends up as a smiley

[funcat]

...why badder with the longtail...??!!

[transam]

3 inch for 2 cylinders is too big. For a 4.5 litre engine each of the 8 primaries would be about 1.5 inch dia.

You can buy hedder mufflers which bolt or weld onto the primaries collector. If open pipes, then 8 going skywards about 18 inches long.

Be nice to see a diagram of your thoughts.

[melvinmelvin]

3 inch for 2 cylinders is too big. For a 4.5 litre engine each of the 8 primaries would be about 1.5 inch dia.

You can buy hedder mufflers which bolt or weld onto the primaries collector. If open pipes, then 8 going skywards about 18 inches long.

Be nice to see a diagram of your thoughts.

2 inch for 2 cylinders then? I just assume that the final pipe section shold be somewhat larger than the primary?

When you say primaries collector I understand that as being the end of the manifold?

Not a very practical place for a muffler in a small boat, would want the muffler to be aft of the actual hull.

Yes, if this was a seagoing boat I would opt for skywards pipes.

But since this is a boat for rivers and klongs I would be very reluctant to add to the height.

I regularly pass under bridges with absolutely minimal clearance between bridge and engine.

[Spoonman]

If open pipes, then 8 going skywards about 18 inches long.

Be nice to see a diagram of your thoughts.

Zoomie's wont work an a NA motor, it needs some back pressure.

[transam]

If open pipes, then 8 going skywards about 18 inches long.

Be nice to see a diagram of your thoughts.

Zoomie's wont work an a NA motor, it needs some back pressure.

Need diagram of OP's thoughts.

[melvinmelvin]

Need diagram of OP's thoughts.

Right, will try to give you an idea;

Not my boat in the above pic, but very similar, 28 feet.

Similar boat above, slightly shorter than mine I'd guess.

Exhaust pipe arrangement above.

Exhaust pipe arrangement above.

I was thinking of doing something similar. Except that I had the idea of 2 pipes each side of the engine.

And also to have the pipes pointing approx horisontallly as to not add any height to the boat.

My idea was 1 pipe per 2 cylinders each side, that is 2 pipes each side.

I was thinking 3 inch pipes but you said too big. So would 2 inch pipes be good?

Note, the boat's beam in the aft section is a little bit more than 1 meter.

Ample room for a V8 but would not like to have a muffler in the boat as well.

Dunno if this helps.

[seedy]

If each cylinder has a separate exhaust port - not siamesed - then I agree that 1.5" would work well.

Join 4 pipes each side with a 3" collector, then a muffler.

Fabricate braces to hold the weight of the system - do not rely on the exhaust manifold bolts/studs in the head. Use a flexible section in the system to allow engine to twist - I would place this just after the collector.

A long thin pipe will tend to increase mid-range torque, while short and fat will be best for high rpm. It all depends on the rpm you will be operating at, I would guess upper mid range of the engine for most running.

If running a turbo diesel then the above is moot as the spent gas is forced out and just about any style of system would allow adequate flow.

[melvinmelvin]

If each cylinder has a separate exhaust port - not siamesed - then I agree that 1.5" would work well.

Join 4 pipes each side with a 3" collector, then a muffler.

Fabricate braces to hold the weight of the system - do not rely on the exhaust manifold bolts/studs in the head. Use a flexible section in the system to allow engine to twist - I would place this just after the collector.

A long thin pipe will tend to increase mid-range torque, while short and fat will be best for high rpm. It all depends on the rpm you will be operating at, I would guess upper mid range of the engine for most running.

If running a turbo diesel then the above is moot as the spent gas is forced out and just about any style of system would allow adequate flow.

right, many thanks for this

initially there will not be any muffler, just open pipes

and initially, while sorting out proper shaft length and screw specs, it will run at rather high rpm,

that is the rpm where you, according to the specs, find the max hp

(or to phrase it more correctly;

when the engine runs at the max HP rpm while having full throttle then I have a reasonably OK screw (and shaft))

(sounds easy to sort out, but it isn't, there are plenty factors and considerations in this process)

after that the time will come for mufflers, braces/support, (I am concerned about the manifold bolts),

I think the only fairly good support would have to use the shaft tube,

so as a start I should go for short and fat and redo it when time comes for mufflers

[seedy]

Your best fuel economy - if this is a concern - along with reasonable speed, will be to operate the engine at its torque peak. Manufacturer of the engine can provide this, typically around 70% of the max RPM.

Also, your prop will need to be pitched to operate at your desired rpm, or serious cavitation will result.

Would like to see it when up and running. Love Hot Rods.

If you want one less worry re: manifold attachment, use studs instead of bolts, especially on aluminum heads as removal and replacement will 'pull' the aluminum material from the head. With studs, install once with Hi-Temp Loctite and they stay put.

Edited October 27, 2011 by seedy

[melvinmelvin]

Your best fuel economy - if this is a concern - along with reasonable speed, will be to operate the engine at its torque peak. Manufacturer of the engine can provide this, typically around 70% of the max RPM.

Also, your prop will need to be pitched to operate at your desired rpm, or serious cavitation will result.

Would like to see it when up and running. Love Hot Rods.

If you want one less worry re: manifold attachment, use studs instead of bolts, especially on aluminum heads as removal and replacement will 'pull' the aluminum material from the head. With studs, install once with Hi-Temp Loctite and they stay put.

thanks,

am aware of the consumption/torque aspect,

when I referred to max HP rpm it was as my method to find the right screw "size"

normal operating rpm will typically be in the 65-80 % range (upper part of that range I guess)

not so worried about cavitation,

Would like to look/see it? same same, me too!

HA! not even sure I can find the boat after the water disappears from Nonthaburi.

[transam]

Your best fuel economy - if this is a concern - along with reasonable speed, will be to operate the engine at its torque peak. Manufacturer of the engine can provide this, typically around 70% of the max RPM.

Also, your prop will need to be pitched to operate at your desired rpm, or serious cavitation will result.

Would like to see it when up and running. Love Hot Rods.

If you want one less worry re: manifold attachment, use studs instead of bolts, especially on aluminum heads as removal and replacement will 'pull' the aluminum material from the head. With studs, install once with Hi-Temp Loctite and they stay put.

thanks,

am aware of the consumption/torque aspect,

when I referred to max HP rpm it was as my method to find the right screw "size"

normal operating rpm will typically be in the 65-80 % range (upper part of that range I guess)

not so worried about cavitation,

Would like to look/see it? same same, me too!

HA! not even sure I can find the boat after the water disappears from Nonthaburi.

Screw size is the least of the problems. In fact it is the last trial and error thing. Tomorrow l will post my thoughts on your project.

[Topcroc]

When running V8 ski boats that operated in fresh water and were direct cooled, i.e. not through a heat exchanger we ran the cooling water after circulating in the engine to both exhaust pipes.

This cooled the pipes at the through hull fitting, also reduced the "Bark" of the exhaust note.

You could do the same but have to ensure the entry to the exhaust pipes is set up so water does not run back to the heads when you turn of the engine.

It is simple to do, sounds great, cheaper than mufflers and lighter.

[melvinmelvin]

When running V8 ski boats that operated in fresh water and were direct cooled, i.e. not through a heat exchanger we ran the cooling water after circulating in the engine to both exhaust pipes.

This cooled the pipes at the through hull fitting, also reduced the "Bark" of the exhaust note.

You could do the same but have to ensure the entry to the exhaust pipes is set up so water does not run back to the heads when you turn of the engine.

It is simple to do, sounds great, cheaper than mufflers and lighter.

Re cooling my thinking was to use an ordinary/standard radiator-exchanger/fan combination as in an ordinary car.

Don't think I fancy having a constant stream of Chao Praya through the engine.

Yes, your idea is surely attractive and should be fairly easy to arrange.

Could use a couple of venturi type pumps maybe, will only work while under way, but still.

Thanks, noted, will think about that.

[BSJ]

Man that's overkill. A 4 cylinder turbo motor could do high speed running using less fuel and weighing a lot less!

[Topcroc]

Yes water pick-up is like a venturi, run from it to a water strainer then a Jabsco water pump that runs off the V belts. Extremely simple set up, Jabso pump is a simple rubber impeller.

Have been thinking about the water entry to exhaust, as the engine is mounted on a gimble, i.e. high, the exhausts could run from the heads downward like a set of extractors ending just over the transom so no problem of water ingress when the engine is turned off.

[Topcroc]

The set up above would work on any type of engine 4, V6, V8.

BSJ is correct in as much as there are plenty of small light suitable engine out there producing stacks of HP.

As you are running in fresh water alloy blocks and cyl heads should be no problem.

[hedonist44]

Have you considered the amount of torque your going to have on that big block? Better do some serious study on it before you get too far along. Here are some pics of exhaust systems used in the boats back home. Each exhaust is same length to ensure proper tuning and going into the receiver that will give you your desired back pressure. You can run wet or dry pipes all depending on what you like. The wet stacks will be slightly muffled compared to the dry ones.

[melvinmelvin]

Thanks for comments and pics.

I know I said higher up that I'd like to have the fastest (or one of the fastest longtails on Chao Praya).

That is still my ambition. In my view that doesn't really take very much. Mainly because most

longtails I've seen over the past 10 years are fairly off on the wrong track re shafts and screws.

And also because there are not too many relatively powerfull engines around, (in longtails).

There are some longtails with 6 straight, V6 and V8 benzine around but most (not all) of these are

converted to gas and lose in performance.

I am fairly sure that any standard (not tuned) Toyota V8 (lightweight alloy) (benzine or diesel) that delivers

250 (or above) hp and with a torque anywhere between 350 to 450 (or above) Nm would do just fine

re being the fastest on the river. Don't even think I need a turbo to outrace the others, from the very start to top speed.

This is provided that I put some thought and work into the selection of screw and shaft.

After all, the boat is fairly lightweight (see the first pic I posted) even if its 28 foot LOA its only 1.15 meter wide

in the aft section. I'd guess total weight of boat, me, engine, fuel and equipment would be roughly 1 metric ton.

To outrace the others with a straight 4 or V4 (that delivers stacks of HP as suggested above) would take some

work on the engine I'd guess. And I'd end up with a very high rev engine, which I for various reasons would like

to avoid if I can.

I liked the idea of wet exhaust and will certainly look more into that and probably end up with that.

In particular if it reduces the bark to an acceptable level, so that I can skip mufflers.

Mufflers are clumsy to arrange on these longtails. Would need support from some rods fastened to the shaft tube.

Not really concerned about the noise myself but more and more Thais are becoming a bit sensitive to noise

in living areas along the klongs.

Farang in own longtail is weird enough, not necessary to do even more to attract the possible attention of BIBs

or the Marine Department.

cheers

[melvinmelvin]

Yes water pick-up is like a venturi, run from it to a water strainer then a Jabsco water pump that runs off the V belts. Extremely simple set up, Jabso pump is a simple rubber impeller.

Have been thinking about the water entry to exhaust, as the engine is mounted on a gimble, i.e. high, the exhausts could run from the heads downward like a set of extractors ending just over the transom so no problem of water ingress when the engine is turned off.

Yes, ingress of water should be easy to avoid.

Down from the manifolds, maybe slightly up again and then straight aft should do the trick.

[melvinmelvin]

Have you considered the amount of torque your going to have on that big block? Better do some serious study on it before you get too far along. Here are some pics of exhaust systems used in the boats back home. Each exhaust is same length to ensure proper tuning and going into the receiver that will give you your desired back pressure. You can run wet or dry pipes all depending on what you like. The wet stacks will be slightly muffled compared to the dry ones.

Nice pics (and boats).

I liked some of those air intakes.

However, a constraint for me is not to add (more than absolutely necessary) to the height of the engine/boat.

Am frequently just scraping under some very low footbridges across the klongs.

Will have to figure out something re air intake.

[melvinmelvin]

btw,

I ordered a brand new longtail just before Xmas, will be delivered end March.

Have done a thorough search of 2nd hand engine markets in Chonburi, Samut Prakan, Rangsit, Nonthaburi and Suan Luang.

It appears that the Toyota 4500 cc diesel, 1VD, that I mentioned in the first entry is not on the market in LoS.

Nobody has ever heard of it. Although its on the market in Australia, US and Europe, used in Landcruiser and in some Pickups.

The 4700 cc Benzin, 2UZ, is known to people, although I only found 1 shop that has 1 engine.

They wanted 120 000 for it, whilst the normal V8 price tag is about 25-30 000.

And I guess any spare parts for the 2UZ will be few and far between.

Hence, I have settled for what seems to be the standard fare in LoS, the 4000 cc Benzin, 1UZ.

All shops seems to have several of that one.

[transam]

btw,

I ordered a brand new longtail just before Xmas, will be delivered end March.

Have done a thorough search of 2nd hand engine markets in Chonburi, Samut Prakan, Rangsit, Nonthaburi and Suan Luang.

It appears that the Toyota 4500 cc diesel, 1VD, that I mentioned in the first entry is not on the market in LoS.

Nobody has ever heard of it. Although its on the market in Australia, US and Europe, used in Landcruiser and in some Pickups.

The 4700 cc Benzin, 2UZ, is known to people, although I only found 1 shop that has 1 engine.

They wanted 120 000 for it, whilst the normal V8 price tag is about 25-30 000.

And I guess any spare parts for the 2UZ will be few and far between.

Hence, I have settled for what seems to be the standard fare in LoS, the 4000 cc Benzin, 1UZ.

All shops seems to have several of that one.

Member philipm had a V8 with all the hop up stuff for conversion. PM the guy and see if he's still got it.

[SoCalChris]

Cool project....I love to see its maiden voyage when completed.

Regarding exhaust pipe configuration, you might want to consider a tri-Y design (4-2-1) as you get good midrange and top end power (good fuel economy too) while a 4-1 header can result in a great top end, but maybe a soggy bottom end. Low end power is not that important for a boat, but will affect your holeshot. I had the 4-1 header on my '69 Hurst/Olds I bracket raced, and a high stall torque converter helped to quickly get the engine into the meat of its rpm range.

I don't know what the firing order of the 4.0L 1UZ is, but you might get lucky in that you can pair the cylinders for optimal scavenging of the exhaust gases and more power. The "4-2" section will pair the cylinders firing 360 crank degrees from each other so the exhaust pulse from one cylinder will suck the exhaust gas out of the other cylinder and vice versa. Then the "2-1" section ideally will then have an exhaust pulse every 180 crank degrees. This setup works well with modern 4 bangers on the street, but again, your engine might not allow for this. For pipe size recommendations, refer to Honda/Toyota/Nissan 2.0L 4cyl aftermarket tri-Y header designs. I have the 4-2-1 header on my Nissan GA16DNE...the motor really kicks in at 3K rpm and pulls hard to redline.

Good luck!

Edited January 23, 2012 by SoCalChris

[transam]

Cool project....I love to see its maiden voyage when completed.

Regarding exhaust pipe configuration, you might want to consider a tri-Y design (4-2-1) as you get good midrange and top end power (good fuel economy too) while a 4-1 header can result in a great top end, but maybe a soggy bottom end. Low end power is not that important for a boat, but will affect your holeshot. I had the 4-1 header on my '69 Hurst/Olds I bracket raced, and a high stall torque converter helped to quickly get the engine into the meat of its rpm range.

I don't know what the firing order of the 4.0L 1UZ is, but you might get lucky in that you can pair the cylinders for optimal scavenging of the exhaust gases and more power. The "4-2" section will pair the cylinders firing 360 crank degrees from each other so the exhaust pulse from one cylinder will suck the exhaust gas out of the other cylinder and vice versa. Then the "2-1" section ideally will then have an exhaust pulse every 180 crank degrees. This setup works well with modern 4 bangers on the street, but again, your engine might not allow for this. For pipe size recommendations, refer to Honda/Toyota/Nissan 2.0L 4cyl aftermarket tri-Y header designs. I have the 4-2-1 header on my Nissan GA16DNE...the motor really kicks in at 3K rpm and pulls hard to redline.

Good luck!

And PAW or Summit (USA) sell the pipes to weld up to do 4-2-1.

[melvinmelvin]

btw,

I ordered a brand new longtail just before Xmas, will be delivered end March.

Have done a thorough search of 2nd hand engine markets in Chonburi, Samut Prakan, Rangsit, Nonthaburi and Suan Luang.

It appears that the Toyota 4500 cc diesel, 1VD, that I mentioned in the first entry is not on the market in LoS.

Nobody has ever heard of it. Although its on the market in Australia, US and Europe, used in Landcruiser and in some Pickups.

The 4700 cc Benzin, 2UZ, is known to people, although I only found 1 shop that has 1 engine.

They wanted 120 000 for it, whilst the normal V8 price tag is about 25-30 000.

And I guess any spare parts for the 2UZ will be few and far between.

Hence, I have settled for what seems to be the standard fare in LoS, the 4000 cc Benzin, 1UZ.

All shops seems to have several of that one.

Member philipm had a V8 with all the hop up stuff for conversion. PM the guy and see if he's still got it.

You mean he had one for sale?

[transam]

btw,

I ordered a brand new longtail just before Xmas, will be delivered end March.

Have done a thorough search of 2nd hand engine markets in Chonburi, Samut Prakan, Rangsit, Nonthaburi and Suan Luang.

It appears that the Toyota 4500 cc diesel, 1VD, that I mentioned in the first entry is not on the market in LoS.

Nobody has ever heard of it. Although its on the market in Australia, US and Europe, used in Landcruiser and in some Pickups.

The 4700 cc Benzin, 2UZ, is known to people, although I only found 1 shop that has 1 engine.

They wanted 120 000 for it, whilst the normal V8 price tag is about 25-30 000.

And I guess any spare parts for the 2UZ will be few and far between.

Hence, I have settled for what seems to be the standard fare in LoS, the 4000 cc Benzin, 1UZ.

All shops seems to have several of that one.

Member philipm had a V8 with all the hop up stuff for conversion. PM the guy and see if he's still got it.

You mean he had one for sale?

Yep

[melvinmelvin]

Cool project....I love to see its maiden voyage when completed.

Regarding exhaust pipe configuration, you might want to consider a tri-Y design (4-2-1) as you get good midrange and top end power (good fuel economy too) while a 4-1 header can result in a great top end, but maybe a soggy bottom end. Low end power is not that important for a boat, but will affect your holeshot. I had the 4-1 header on my '69 Hurst/Olds I bracket raced, and a high stall torque converter helped to quickly get the engine into the meat of its rpm range.

I don't know what the firing order of the 4.0L 1UZ is, but you might get lucky in that you can pair the cylinders for optimal scavenging of the exhaust gases and more power. The "4-2" section will pair the cylinders firing 360 crank degrees from each other so the exhaust pulse from one cylinder will suck the exhaust gas out of the other cylinder and vice versa. Then the "2-1" section ideally will then have an exhaust pulse every 180 crank degrees. This setup works well with modern 4 bangers on the street, but again, your engine might not allow for this. For pipe size recommendations, refer to Honda/Toyota/Nissan 2.0L 4cyl aftermarket tri-Y header designs. I have the 4-2-1 header on my Nissan GA16DNE...the motor really kicks in at 3K rpm and pulls hard to redline.

Good luck!

The firing sequence is 1-8-4-3-6-5-7-2

when looking at the engine from the front; odd numbers on the RIGHT side, even numbers on the LEFT side

the cylinders are numbered from front to back

[SoCalChris]

The firing sequence is 1-8-4-3-6-5-7-2

when looking at the engine from the front; odd numbers on the RIGHT side, even numbers on the LEFT side

the cylinders are numbered from front to back

Bads news....this firing order is not tri-Y header friendly with optimum exhaust gas scavenging and keeping each bank of the V8 isolated.

Options:

1. You still could do a tri-Y for space savings pairing 1-5, 3-7, 6-8 and 4-2 cylinders for the primaries. This would create pulse intervals of 270 and 450 crankshaft degrees that might still produce good midrange power, but really with unknown results.

2. Really crazy exhaust header design with primary tubes crossing over the top of the engine and paired with the cylinder having the 360 crank degree exhaust pulse interval. I've seen this on race engines, it looks cool, but really don't recommend it.

3. Keep it simple, just do the 4-1 like other people have suggested. This would be my choice.

Cheers,

Chris