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Old 07-01-2010, 09:10 PM
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Had a cam brainstorm, your thoughts?

I was checking the timing on a car today and had a thought. If this has already been done by someone, please point me in that direction as I think it is an interesting idea.

The crank spins twice to the cams 1 revolution. The second time, both valves are closed, so there is no air/fuel/spark to push the piston back down. More importantly the piston has to push its way up towards the cylinder head. My thought is if on this second travel up the exhaust lobe of the cam has a second low lift area to open the exh valve, just enough to relieve some of the pressure so that the piston can travel more easily.

I suppose it would possibly free up some power, but it would also put less strain on the bearings. I have two concerns:

Cam to connecting rod clearance(more for stroker applications)
Cars utilizing 02 sensors would possibly be thrown off by the slight air with no fuel.

What do you think?
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Old 07-01-2010, 09:52 PM
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Old 07-01-2010, 10:28 PM
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Quote:
Originally Posted by texas97z
I was checking the timing on a car today and had a thought. If this has already been done by someone, please point me in that direction as I think it is an interesting idea.

The crank spins twice to the cams 1 revolution. The second time, both valves are closed, so there is no air/fuel/spark to push the piston back down. More importantly the piston has to push its way up towards the cylinder head. My thought is if on this second travel up the exhaust lobe of the cam has a second low lift area to open the exh valve, just enough to relieve some of the pressure so that the piston can travel more easily.

I suppose it would possibly free up some power, but it would also put less strain on the bearings. I have two concerns:

Cam to connecting rod clearance(more for stroker applications)
Cars utilizing 02 sensors would possibly be thrown off by the slight air with no fuel.

What do you think?
Take a look HERE and you will see what the 4 strokes do- there's no wasted stroke where the exhaust would be open a little to relieve pressure- there IS the exhaust stroke, however.

When the piston is traveling down, it is either making power, or pulling in a fresh charge.
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Old 07-01-2010, 10:28 PM
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Compression tends to make more power.

What you're suggesting sounds like a 'Jake brake' on a diesel truck, same principal, it's for slowing the truck down.
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Old 07-01-2010, 11:34 PM
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What you need is a two stroke V-8.
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Old 07-01-2010, 11:42 PM
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Ok, another good thread out of thin air?

I think there may be some built-in breathing tricks/momentary events on some of the multi-valve inline 4s. Or else there has been plenty of experimentation. I noticed on 01 Nissan that none of the 4 valves seemed to have the exact timing or ramp for that matter.

Made me feel a little bit like a cave man eating a raw fish while watching a fire caused by lightening.

No understand cam.. . Duntov
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Old 07-02-2010, 01:02 AM
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That would be sweet if they made a two stroke V8! They could set it up like a detroit diesel, and have ports near the bottom of the cylinder and have the air/ fuel mixture force fed into the engine via a blower or turbo, or BOTH!
Those engines have 4 valves per cylinder, all of them Exhaust!
I bet if you made around a 400 ci V8 using this setup you could patent it and it would probally easily beat the big blocks because you have power every other stroke rather than one every 3... Twice the power THEORETICALLY
So say a 400 sbc puts out 400 horse and around that in torque, with a 2 stroke setup similar to this you could potentially get 800 horse and 800 ft. lbs.

I want in on some of the money if someone patents this though!!! even if it's 1 or 2 %
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Old 07-02-2010, 02:18 AM
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This is a six cylinder two stroke diesel, TS3, but has the cylinders horizontally opposed, exhaust is scavenged with a Roots blower.

More info here andhere.

Killed by Chrysler the TS4.

"The engines that were put in trucks ran up to 1.2 million miles between the 8 of them, trouble free, before being pulled out and scrapped on instructions from Chrysler to protect Chrysler’s joint venture in England with Cummins."
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Old 07-02-2010, 06:24 AM
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2sroke

Quote:
Originally Posted by QParker
That would be sweet if they made a two stroke V8! They could set it up like a detroit diesel, and have ports near the bottom of the cylinder and have the air/ fuel mixture force fed into the engine via a blower or turbo, or BOTH!
Those engines have 4 valves per cylinder, all of them Exhaust!
I bet if you made around a 400 ci V8 using this setup you could patent it and it would probally easily beat the big blocks because you have power every other stroke rather than one every 3... Twice the power THEORETICALLY
So say a 400 sbc puts out 400 horse and around that in torque, with a 2 stroke setup similar to this you could potentially get 800 horse and 800 ft. lbs.

I want in on some of the money if someone patents this though!!! even if it's 1 or 2 %
Maybe you could put a big check valve under the carburetor.

knock out the freeze plugs

Drill 1 5/8ths from there into the cylinders for exhaust ports.

Port out to 1 3/4

Use 1 3/4 shorty headers up side down bolted over freeze plug holes

Route exhaust into the breather (eliminating exhaust emissions altogether)

Apply to Obama for Green Money; Hire Alvin Greene as finance Director.

Someone else needs to work out the details with the existing exhaust ports, I worked Alvin Greene into it and got lost.
////////////////////////////Duntov


L
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Old 07-02-2010, 06:33 AM
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I didn't explain my thoughts very well, but some of you got what I was suggesting anyway, by way of the 4 stroke engine idea. This was very hypothetical thinking just for fun. So sorry no patents or plans here, just wanted to stretch the imagination muscle, or see examples if anyone had tried it.

Thanks for playing along, if anyone else has thoughts keep it going.

Josh
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Old 07-02-2010, 06:47 AM
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Is there an older lady in Flower Mound Tx that makes the best Biscuits in the world?

Quote:
Originally Posted by texas97z
I didn't explain my thoughts very well, but some of you got what I was suggesting anyway, by way of the 4 stroke engine idea. This was very hypothetical thinking just for fun. So sorry no patents or plans here, just wanted to stretch the imagination muscle, or see examples if anyone had tried it.

Thanks for playing along, if anyone else has thoughts keep it going.

Josh
Most of us that had a dirt bike have thought of it at least once..
I know a really smart/crazy old man who has talked about it constantly since it first came up in conversation in the Seventies...

Think we'd all like to experience the Power curve it would have. Drove my first 238 Detroit in 70 and still like any 2 stroke
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Old 07-02-2010, 10:25 AM
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I have a spare 4banger lying around I think it backfired and lit the carb on fire so many times it plugged all the jets and stuff, so it'd be a good test engine...
Maybe I'll start small like with a lawnmower, we need a new one anyways!
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Old 07-02-2010, 12:32 PM
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If you trash your lawn mower trying it, I also have a spare we could try it on. Tinkerers unite
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Old 07-02-2010, 12:43 PM
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on a 4 stroke cycle, it is made of an induction stroke, compression stroke, power stroke, and exhaust stroke.

if you let out pressure during the compression stroke then the engine will lose power.

long duration cams already do this, as the intake valve is open as the piston is rising in the bore during the compression stroke. the effects on cam timing on the static compression ratio is called dynamic compression ratio.

this is why high static compression ratios are needed with long duration cams (late intake closing point) to keep the cylinder pressure up.
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Old 07-02-2010, 12:50 PM
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opening the exhaust valve on the compression stroke will send your uburned fuel and air out the header....not good for power.

HOWEVER, add a supercharger and a special timing setup and you *should* be able to convert any 4 stroke into a 2 stroke...

I've always wanted to see this...
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