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AndyGJ

Shorty Headers - Questions about Which Ones and Installation

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I'm of the thought headers provide very minimal, if any gain, up to around 700HP. Getting rid of your cats will provide a 10-15HP gain up top though. My .02

 

 

+1 ON GETTING SOME NO CATS !!! HOWEVER, IF YOU ARE CONCERNED ABOUT NOT GETTING LOUDER, BUT GAIN 15-20 AT THE REAR WHEELS YOU CAN CONTACT LETHAL PERFORMANCE, AND GET THEIR BRAND 2.5 INCH X-PIPE WITH MAGNAFLOW HIGHFLOW SPUN CATS. THESE CATS FLOW EXTREMELY WELL, AND IS AS CLOSE TO HAVING A NO CAT X-PIPE WITH OUT THE LOUDNESS THAT IS NORMAL ON A NO CAT X-PIPE. MAKE SURE YOU GET LETHALS OWN BRAND AND NOT THE MAGNAFLOW X-PIPE. LETHALS PRODUCT IS STAINLESS, USES THE SAME HIGHFLOW MAGANFLOW CATS AT HALF THE PRICE. ADDITIONALLY, UNLESS YOU ARE GOING OVER 700 RWHP FORGET ABOUT SHORT OR LONG TUBE HEADERS ESPECIALLY IF YOU WANT TO KEEP THE EXHAUST DECIBELS DOWN SO YOU CAN HEAR YOUR WIFE OR THE NEXT HOUR AFTER YOU TAKE IT OUT FOR A DRIVE. :salute:

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Kevin - how much louder did the exhaust get when you added the FRPP shorty headers to your SGT? I just added the KR mufflers (love them!) to mine, so I have the right amount of volume that I like on the loud side of things. An earlier comment on the headers said that it didn't get louder, just smoother sounding on the shorty headers is what they noticed.

 

Any thing you recall about the change in sound?

 

Thanks,

Andy.

It's only just a little bit louder, but it's quite a bit deeper like it has more bass to it.

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Phil, again, I could be wrong but.... the sc does not push the mixture out of the cylinder.

 

 

I think this is the easiest explaination I can give:

 

If you pressurize the intake side, do you think the pressure somehow magically disappears in the combustion process? No, if you pressurize the intake side you have to pressurize the exhast side.

 

Pressure in/Pressure out.

 

I mean, it's not like you stuff 20psi into the intake and it somehow magically disappears. It HAS to come out...and it comes out of the exhaust.

 

Does that make more sense?

 

 

Phill

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Nice exposition, Phill. If I could have understood it I might have said, "Uh-huh, just what I thought". As it is, I just will mention that valve overlap has different effects on 'charged engines than on normally aspirated ones.

 

As to the shorty headers: they are more like jewelry than jock-straps. For those who value a lumpy idle, the noise of tubular headers is a real plus: that "tink, tink, tink" usually damped out by cast iron is sweet to the trained ear, and you don't have to open the hood to verify it.

 

 

Agree with both points. I intentionally left valve overlap out of the equation. It would just compound the confusion. It would also aid in getting my point across that the pressure going into the intake would go out of the exhaust when both valves are open as the same time. But I digress.....

 

I actually was looking for that "tink tink tink" you mention when I put my shorties on. And that's ALL I was looking for. And didn't get it.

 

I love that sound but if I want it, I fear I'll need to cam it. And I ain't goin' there.

 

 

Phill

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But the SC does not push anything out as the intake valve is closed during the exhaust stroke so the SC has no effect on the contents of the cylinder at that time.

 

 

You're not taking into account the PRESSURE the SC added (edit: to the cylinder). Yes, the exhaust valve is closed (not taking into account valve overlap) but the cylinder is PRESSURIZED, and it is pressurized by the supercharger. With a NA engine, there is no PRESSURE in the cylinder when the exh. valve opens (leave expansion out of the equation for the moment).

 

Add 2 BAR (~30psi) and maybe it would be easier to "see". If you have 30psi of pressure in the cylinder (vs. 0psi), when the exhaust valve opens, what happens? Does the pressure wait for the upward motion of the piston to expell the burnt gasses? No, the PRESSURE in the cylinder (due to the SUPERCHARGER) expells the gasses and the piston finishes the job.

 

I sometimes find it easier to explain things by exagerating so rather than use (real life) figures of 1 or 2 BAR, let's use...10 BAR. That would be 147 psi. Fill a cylinder with 147 psi and what happens when you open the valve? Does the gas wait for a piston to move before exiting the cylinder?

 

Am I gettin' close yet?

 

 

Phill

Edited by 2010KonaBlueGT

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The pulses of each exhaust exit create the vacuum to suck or scavenge the exhaust more completely from the cylinder and the exhaust manifold.

 

 

 

I had another thought that might help.

 

Yes, scavenging is one of the primary reasons a NA engine can achieve greater than 100% VE. It actually helps "suck" the incoming intake charge into the cylinder and you can see just over 100% VE (101%-110% VE) on high performance engines.

 

A Super Charger running 15psi boost gives your engine 200% VE.....

 

Where's your scavenging effect now? (It's moot)

 

 

Phill

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+1 ON GETTING SOME NO CATS !!! HOWEVER, IF YOU ARE CONCERNED ABOUT NOT GETTING LOUDER, BUT GAIN 15-20 AT THE REAR WHEELS YOU CAN CONTACT LETHAL PERFORMANCE, AND GET THEIR BRAND 2.5 INCH X-PIPE WITH MAGNAFLOW HIGHFLOW SPUN CATS. THESE CATS FLOW EXTREMELY WELL, AND IS AS CLOSE TO HAVING A NO CAT X-PIPE WITH OUT THE LOUDNESS THAT IS NORMAL ON A NO CAT X-PIPE. MAKE SURE YOU GET LETHALS OWN BRAND AND NOT THE MAGNAFLOW X-PIPE. LETHALS PRODUCT IS STAINLESS, USES THE SAME HIGHFLOW MAGANFLOW CATS AT HALF THE PRICE. ADDITIONALLY, UNLESS YOU ARE GOING OVER 700 RWHP FORGET ABOUT SHORT OR LONG TUBE HEADERS ESPECIALLY IF YOU WANT TO KEEP THE EXHAUST DECIBELS DOWN SO YOU CAN HEAR YOUR WIFE OR THE NEXT HOUR AFTER YOU TAKE IT OUT FOR A DRIVE. :salute:

 

 

The Magnaflow X pipe is good too. I've had it on my car for about 4 years now. Headers traditionally give bigger gains because the ports are not matched very well or the design of the OEM manifolds is poor. The design of the 3V manifolds are pretty good and not much difference between the ports so there are no gains to be had on our cars where headers are concerned. The gains come from getting rid of the restrictions of the cats.

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You're not taking into account the PRESSURE the SC added (edit: to the cylinder). Yes, the exhaust valve is closed (not taking into account valve overlap) but the cylinder is PRESSURIZED, and it is pressurized by the supercharger. With a NA engine, there is no PRESSURE in the cylinder when the exh. valve opens (leave expansion out of the equation for the moment).

 

Add 2 BAR (~30psi) and maybe it would be easier to "see". If you have 30psi of pressure in the cylinder (vs. 0psi), when the exhaust valve opens, what happens? Does the pressure wait for the upward motion of the piston to expell the burnt gasses? No, the PRESSURE in the cylinder (due to the SUPERCHARGER) expells the gasses and the piston finishes the job.

 

I sometimes find it easier to explain things by exagerating so rather than use (real life) figures of 1 or 2 BAR, let's use...10 BAR. That would be 147 psi. Fill a cylinder with 147 psi and what happens when you open the valve? Does the gas wait for a piston to move before exiting the cylinder?

 

Am I gettin' close yet?

 

 

Phill

 

 

Phil....I just took your explanation as fact, but now that you exagerated the issue (147 psi) I totally get it...the piston really has very little to push at this point...man, you make this stuff easy to understand. Thanks for saving me the $$ on the headers...I'm going for the low restriction cats now!

 

This forum is the greatest resource!!

 

Andy.

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Well Phil, we will have to agree to disagree. Yes the SC can introduce more air/fuel mixture into the same size cylinder and then the intake valve closes and the piston, on the compression stroke, compresses the air/fuel mixture. The air fuel mixture is detonated near the top of the piston travel due to spark, or in cases of over compression or low octane fuel, it ignites spontaneously due to heat (compression, similar to diesel). The air fuel mixture is detonated. If you have a compressed air fuel mixture then there is even more of an explosion to force the piston down on the power stroke. But again, getting back to basics, the air fuel mixture is mostly burned up in the explosion. The intake valve is closed and the SC can only introduce pressure when the intake valve is open. The intake valve is NOT open on the exhaust stroke so it is only the piston pushing the unburnt remnants out of the cylinder. It really is very simple.

 

Yes you can pack more air fuel compound in to the cylinder under pressure but then more is burned and generating more power. The SC does NOT push or force the unburnt compound out of the cylinder. The only force moving the unburnt mixture out of the cylinder is the upward movement of the piston and the scavenging effect of the exhaust manifold. To use your theory that there is more air fuel mixture to move with a SC would negate the use of the SC. If the compressed air fuel mixture existed after spark then there would be no additional power from the additional mixture. Again, it is very simple. The SC can only add pressure to the cylinder when the intake valve is open and the intake valve is closed during the exhaust stroke. If the intake valve were completely open during the exhaust stroke then the incoming air fuel mixture would be diluted with hot exhaust gasses which would not only dilute the air fuel mixture but also heat the incoming air fuel mixture. The incoming air fuel mixture is intentionally to be as cool as possible. That is why SC have an intercooler to reduce the temperature of the incoming air fuel mixture. The cooler the air the more dense and thereby more explosive of a combination of air fuel and spark. SC, by their very nature, heat the incoming air fuel mixture due to compression. That is why the inter cooler is necessary. The air fuel mixture also contributes to the temperature of the cylinder and the explosion. By leaning the air fuel mixture you raise the temperature and gain HP. But leaning the mixture too much contributes to excessive heat and pre-ignition and burnt pistons. A richer mixture will produce a cooler cylinder .

 

Implying that there is more air/fuel to force out with a SC compressed mixture is also erroneous. And to prove this the additional air fuel compound produces more power than a NA air fuel mixture. If it were the same amount of power there would be no reason to add additional air fuel were it not to create additional power. And the additional air fuel mixture IS burned up the same as with the NA air fuel mixture. And the proof of this is that the Whipple and Kenne Belle supercharged engines meet CARB standards. So, it really is very simple.

Edited by 07SGT

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Interesting ... I don't see them on the Ford Racing website anymore. :shrug:

 

 

You can still get them on eBay or Summit; P/N M-9430-S197C

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You can still get them on eBay or Summit; P/N M-9430-S197C

 

 

Found them at Summit!! Thanks!

Andy.

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Found them at Summit!! Thanks!

Andy.

 

 

Ceramic coated or plain?

 

I didn't know they stopped making the ceramics. I have 'em and they still look new.

 

 

Phill

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