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Discussion Starter #1
What makes a N2O cam a N2O cam?
What is different about it compared to the best cam with out N2O?
Is it events? Is it separation? Both?
Is it overlap? Exhaust opening event?

I am looking to discuss the theory of Turbo vs N2O vs Blown vs N/A real proven differences and best case scenarios.

What cam would suit each of these combos in a 502 BBC or a similar engine?
800 HP N/A
1200 HP N2O
1600 HP Supercharged
2000 HP Turbo
Give or take a 100 hp or so?
 

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What materials are we working with?

What architecture are we working with?

All we are doing is managing heat and pressure with architecture designed 50 years ago for OEM applications and easily manufacted in mass production.

At the upper end we are always playing cat and mouse between horsepower and durability. They have an inverse relationship most of the time.
 

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Throw out NOS CAms, Circle Track Cams, Marine Cams, Drag cams....that's all from the marketing department. A given cam is to make power in a given rpm range with variables being induction, exhaust, piston speed, CID, and rpm.
chris, I was told by bullet cams that I would be limited to about 300 hp worth of spray with the cam they built for my 622 bbc. it has a 115 centerline and if I wanted to put more to it, it would be best to get a cam with more centerline in it. I was always tought that the more centerline lets heat out better or more efficient? always wanting to learn more. I'm all ears.
 

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Discussion Starter #6
We need more input....come on guys...what is the diff in cams for same engine....
One blown
One turboed
One sprayed
and one all motor.
 

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Exhaust duration to get it out is one of the biggest differences I see.

23° nitrous cam for my SBC by LSM.

282 296 @ .050
.480 in .470 lobe with 1.7 rr. (.816 .799)
114 with 4 degree advance.

I see the same in blower cams. More exhaust duration.
 

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Generic formula is to open the exhaust valve sooner, keep it open longer... and leave the intake pretty much alone. This comes out to more exhaust duration, wider LSA, and advancing the cam. Too much exhaust lobe without widening the LSA produces too much overlap, and sends a lot of the nitrous right out the tailpipe without being burned. If the cam isn't advanced when using a wide split, the intake events fall behind.

Exactly how much of all these things is best determined by someone who has a lot of experience, and has done some comparisons on engines similar to yours.
 

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Post the base engine George, CID, Heads,
Considering his HP I think he means conventional heads. BBC 502" so big bore setup 800hp N/A
What cam would suit each of these combos in a 502 BBC or a similar engine?
So 400hp nitrous or what ever it takes 1200 total on nitrous. my guess takes less than 400shot.

What I have seen is
800hp N/A BBC shorter duration .050 N/A and 8-12* more duration on exhaust and 106-110 lobe sep

1200Hp nitrous more intake duration but with this small of shot maybe not more intake. But will have 14-16* of exhaust duration and 112-116 lobe sep.

2000hp turbo setup depends on twin or single and exhaust housing. but normally see smaller duration that N/A depends on size and how hard you are going to be working turbos. 114 split close to same intake and exhaust duration little more exhaust duration(4-8*).


Blower cams are normally aggressive that I see 15* more exhaust and wide lobe sep.


This is just a casual observer from the outside no expert just what I see from outside.....<--my disclaimer just would like to see this thread take off.
 

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I want to know as well and not specific to engine, but I have always been under the impression you increase the LSA. However, I have seen some more recently that are spraying quite a bit on a 109. When I had my cam done a t Bullet, they went 110 and I told them that I only wanted to spray up to 175. So my generic question to add is, is there a breaking point of amount of spray associated to where you want you LSA?? Am I leaving power on the table N/A by using a 110 for such a small shot??
 

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I want to know as well and not specific to engine, but I have always been under the impression you increase the LSA. However, I have seen some more recently that are spraying quite a bit on a 109. When I had my cam done a t Bullet, they went 110 and I told them that I only wanted to spray up to 175. So my generic question to add is, is there a breaking point of amount of spray associated to where you want you LSA?? Am I leaving power on the table N/A by using a 110 for such a small shot??
LSA = result of valve events.... a 110 LSA can be so many different combinations of events.
 

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Discussion Starter #15 (Edited)
We are getting somewhere now.............
I want us to discuss just what would you different to a cam to suit each combo on a run of the mill, engine.
I am not talking about mine specifically. We race, tune, use, Harley, BBC, Suzuki, S&S, Hemi gen 2, LS, SBC, PSB, Pro Mod.....etc.
Just engines in general. I understand all engines are different, but I also understand and practice, the same kind of needs suit all engines.
Just think for a moment. We, most of us have one kind of engine we work on. At our shop we work on small to tall, big to bad, 2 valve, 4 valve and 5 valve LOL.
They ALL like the same stuff. They all need to trap more air and fuel, burn it quick and get all of it out asap.

So given that position on the subject, let's consider from our on experience, and our own thinking, what would each combo "like" different than the other combo?

Lets talk about events...LSA, why is wide better than narrow...it is not the LSA or the advance. It is what those "common" terms mean to events.....
Let's break it down more.....I am learning here, not teaching.
 

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572 with 18 Degree Chiefs
Sheet Metal Intake x 1150's by Lance Patton
15.5 to 1
500HP Fogger System
Dry Sump Engine
Peak power 7200 to 7600
Drag Race

Cam 1
.933/.911 with 1.8/1.7
317/341 .020
286/306 .050
114/120 Centers
117 Sep

2nd cam
864/829 with 1.8/1.7
312/339 .020
283/300 .050
110/112 Centers
111 Sep

I know what the results were but in this case the application is a jet boat which is nothing more than a "Water Break Dyno". This engine is run with data logger and it well documented.

The first cam was sold as a NOS cam. Was told to customer it may be down on engine but will pick up on NOS.
The second cam is my cam, designed for what the customer wanted the engine to do.

Look at the numbers and give it some thought.
 

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Discussion Starter #17 (Edited)
^^^^^^^^^^^ Talk about what is different here^^^^^^^^^^^We are getting somewhere now.............
I want us to discuss just what would you do different to a cam to suit each combo on a run of the mill, engine.
I am not talking about mine specifically. We race, tune, use, Harley, BBC, Suzuki, S&S, Hemi gen 2, LS, SBC, PSB, Pro Mod.....etc.
Just engines in general. I understand all engines are different, but I also understand and practice, the same kind of needs suit all engines.
Just think for a moment. We, most of us have one kind of engine we work on. At our shop we work on small to tall, big to bad, 2 valve, 4 valve and 5 valve LOL.
They ALL like the same stuff. They all need to trap more air and fuel, burn it quick and get all of it out asap.

So given that position on the subject, let's consider from our on experience, and our own thinking, what would each combo "like" different than the other combo?

Lets talk about events...LSA, why is wide better than narrow...it is not the LSA or the advance. It is what those "common" terms mean to events.....
Let's break it down more.....I am learning here, not teaching.
 

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Chupa Cabra
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9,824 Posts
In general with a nitrous application I open the exhaust valve sooner to give the exhaust port more time to evacuate the cylinder. Since an oxidizer is being introduced to the cylinder in an attempt to burn more fuel and make more power, more spent exhaust gas is created as the result. To sustain power throughout the operating range with this added exhaust gas(especially at the high end of the operating range) and expel excess heat generated by the faster burn of the oxidizer being introduced, the valve needs to open sooner. Since nitrous burns so quickly, it creates a sharp spike in cylinder pressure early after TDC on the power stroke. Because of this more work is being put to the crank in a shorter period of crank degrees. The exhaust valve can be opened sooner without losing a lot of torque(if any in the usable operating range) which carries more power upstairs.

If the exhaust valve is not opened sooner in a nitrous application versus a cam optimized for the same engine but for motor usage, power will not carry as far into the operating range as it did on motor. Peak power will be made at a lower RPM.

This is caused by spent exhaust gas not being evacuated from the cylinder. Spent exhaust gas displaces fresh air/fuel charge and it also heats it up. Added power cannot be made by attempting to burn spent exhaust gas, let alone sustain at the level it was.

I also like to close the exhaust valve later in an attempt to expel the last bit of remaining exhaust gas present in the clearance volume. You don't want to force the piston to do the majority of the work in pushing the spent exhaust gas out on the exhaust stroke as that would incur a large pumping loss. The size of the motor, the piston speed it generates and the amount of nitrous used determines where the exhaust valve should open among other things. Opening the exhaust valve at the right point on the power stroke allows the pressure differential between in cylinder pressure and atmospheric pressure in the exhaust port to do the majority of evacuation for us. Opening the valve at the right point on the power stroke ensures that we incur the smallest pumping loss possible on the exhaust stroke by removing the most spent exhaust gas it can before starting the exhaust stroke. Opening it too early will expel cylinder pressure that could of been used to do more work on the piston driving it down and producing more torque. Thus slowing the car especially off the line and on the gear change. A car with a 2 speed trans may become an absolute turd if this happens. A 3 speed auto may not be affected as much nor would a 4 or 5 speed.

That said, not all of the spent gas will be forced out during blow down or on the exhaust stroke. Leaving the exhaust valve open a little bit longer and closing it later will allow the negative reflected wave that arrives during overlap to help pull that last bit of remaining higher pressure spent gas present in the clearance volume out the cylinder.

Yes you lose some charge doing this. The benefit to this is removing more spent gas from the cylinder means we can now cram more fresh charge into the cylinder than we could have had we not closed the exhaust valve later. This almost always shows a power increase versus closing the exhaust valve earlier in a nitrous application that operates at higher RPM's. A lower RPM nitrous engine may not need this as much as a higher RPM nitrous engine.

I like to close the intake valve later in a nitrous application as well. Nitrous engines that are utilizing large amounts of nitrous are timing sensitive more than likely. A later intake valve close event helps to bleed some cylinder pressure off by pushing some air/fuel mixture out of the cylinder from the late closing event. This also helps to soften the hit on a smaller tire car or one that needs some help in the traction department.

Intake valve open event I like to delay a bit to ensure that reversion doesn't occur at lower RPM's(coming off the starting line) and cause a nitrous backfire. I may be totally wrong in doing this, but I feel it helps. I normally only do this on heavy nitrous engines.

Just my two cents on the subject. I won't get into the turbo or S/C stuff, yet. lol
 

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572 with 18 Degree Chiefs
Sheet Metal Intake x 1150's by Lance Patton
15.5 to 1
500HP Fogger System
Dry Sump Engine
Peak power 7200 to 7600
Drag Race

Cam 1
.933/.911 with 1.8/1.7
317/341 .020
286/306 .050
114/120 Centers
117 Sep

2nd cam
864/829 with 1.8/1.7
312/339 .020
283/300 .050
110/112 Centers
111 Sep

I know what the results were but in this case the application is a jet boat which is nothing more than a "Water Break Dyno". This engine is run with data logger and it well documented.

The first cam was sold as a NOS cam. Was told to customer it may be down on engine but will pick up on NOS.
The second cam is my cam, designed for what the customer wanted the engine to do.

Look at the numbers and give it some thought.

Cam number 1 made 1070HP
Cam number 2 made 1175HP
NA no NOS test on the dyno.

In the boat the engine pulled to 7050 with the first cam.
In the boat the engine pulled to 7250 with the second
On the pump chart this verified the engine had picked up at least 90HP on with cam change.

On NOS
In the boat the first cam would pull to 7380 with a 500 tune.
In the boat the second cam pulled to 7640 with a 500 tune.
On the pump chart this verified the engine was making at least another 120HP with same NOS tune.

The beautiful thing about a jet is there is no BS dyno figures that are going to turn that impeller anymore rpm. What it is...is what it is.
 

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Chupa Cabra
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Cam number 1 made 1070HP
Cam number 2 made 1175HP
NA no NOS test on the dyno.

In the boat the engine pulled to 7050 with the first cam.
In the boat the engine pulled to 7250 with the second
On the pump chart this verified the engine had picked up at least 90HP on with cam change.

On NOS
In the boat the first cam would pull to 7380 with a 500 tune.
In the boat the second cam pulled to 7640 with a 500 tune.
On the pump chart this verified the engine was making at least another 120HP with same NOS tune.

The beautiful thing about a jet is there is no BS dyno figures that are going to turn that impeller anymore rpm. What it is...is what it is.
You and your wacky nitrous cams always impress me Chris!

That is the one thing I know we do a bit differently, but you can't argue with your results.
 
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