Reverse split cams and N2O?
10-26-2007, 08:13 PM
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Reverse split cams and N2O? Nobody can give me an educated answer on whats right? People say you shouldnt spray when using a reverse split duration cam, but when asked why everybody responds "Well I just heard you shouldnt?" Can an informed person separate myth from from fact for us? What is really going on here?
Wasnt real sure where to post this one
Wasnt real sure where to post this one
10-26-2007, 11:02 PM
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I haven't heard that you shouldn't spray with a reverse split. I have heard that it probably isn't the optimal setup to get the most benefit from the nitrous, though.
Think of the engine as a pump. Most of the mods we do are to increase air flow through the engine to provide as much oxygen as possible to the fuel mixture. If we increase the volume of oxygen through the intake, the result is more combusted gases that need to exit through the exhaust.
In the case of nitrous, we are drastically increasing the amount of ingested oxygen by chemical means. The increase is normally much higher than we could expect to see through normal NA mods to the intake. What goes in must come out.
A reverse split cam is intake biased and tends to compound the problem of getting rid of the extra exhaust gases resulting from the fuel mixture burn with nitrous. A normal split will be exhaust biased and allow extra time for the burned gases to exit during the exhaust stroke.
Now, having said that, there are some people that believe choosing a cam for nitrous use doesn't become a big factor until you reach levels of nitrous that are higher than a 200 shot.
I have probably oversimplified here; but I only stayed one night at the Holiday Inn. I'm sure there are a lot of members better qualified than I to answer your question. Maybe they will chime in later.
Think of the engine as a pump. Most of the mods we do are to increase air flow through the engine to provide as much oxygen as possible to the fuel mixture. If we increase the volume of oxygen through the intake, the result is more combusted gases that need to exit through the exhaust.
In the case of nitrous, we are drastically increasing the amount of ingested oxygen by chemical means. The increase is normally much higher than we could expect to see through normal NA mods to the intake. What goes in must come out.
A reverse split cam is intake biased and tends to compound the problem of getting rid of the extra exhaust gases resulting from the fuel mixture burn with nitrous. A normal split will be exhaust biased and allow extra time for the burned gases to exit during the exhaust stroke.
Now, having said that, there are some people that believe choosing a cam for nitrous use doesn't become a big factor until you reach levels of nitrous that are higher than a 200 shot.
I have probably oversimplified here; but I only stayed one night at the Holiday Inn. I'm sure there are a lot of members better qualified than I to answer your question. Maybe they will chime in later.
10-27-2007, 12:04 AM
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Are you useing your stock intake? If not and you are running a FAST, a reverse split cam wouldn't help you out. When a reverse split cam is spec'd it is usually because the intake side has a bigger restriction in it rather than the exhaust side. An example of this would be useing a 2 barrel carb on a older SBC, the carb is the biggest restriction due to not enough flow. With the reverse split cam you can "fool" the motor into thinking that you are useing a 4 barrel carb due to giving the intake valve more time to be open. I second the info provided by TA455, with keeping your n2o down to around a 100-150 shot. If you plan to run a 150 shot it would be very wise to make sure of an efficient exhaust system and strong exhuast flow number's to clear the gases out of the combution chamber's.
10-27-2007, 12:33 AM
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Thanks guys, heres the background info, 2004 GTO m6, stock LS6 intake, TR 230/224 @112 cam, Patriot stage 2 ls6 heads, Kooks 1 3/4 longtubes, w/ SLP loudmouth, and SLP pulley, plus all supporting mods. I just purchased a kit from Nitrous outlet and was just wondering why people said what they said?
10-27-2007, 12:58 AM
#6
To emphasize what TA455 said..
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
10-27-2007, 02:42 AM
#7
To emphasize what TA455 said..
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
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10-27-2007, 02:49 AM
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As long your under a 200 shot, almost any cam will be fine. You may not get the full potential of the nitrous shot, but you will definately know its there. The best thing to do is to try it out and see, that will tell the true story.
10-30-2007, 12:42 PM
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Originally Posted by Asmodeus
To emphasize what TA455 said..
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
To emphasize what TA455 said..
The reverse split is less than ideal because that cam delays the opening of the exhaust valve (increases low end torque). Nitrous burns faster and wants the exhaust valve opened sooner. The exhaust valve is also open a shorter duration and you have a lot more exhaust gas to dispell than the the intake lobe brought in by itself. It might not all get out by the time the valve closes (increased lift is another way to compensate, but you already have the cam, and I don't know if your valvetrain can handle a 1.8 rocker on the exhaust side). This can polute the incoming air charge as well as heat it up. Some not so friendly things can happen under those conditions (easier to detonate), and it won't optimize power.
Bingo.
