No H-pipe

Nightfire said:

You hit the nail right on the head. The mod motors are odd firing motors so therefor a crossover mid-pipe is needed to equalize the exhaust pressure pulses

Click to expand...

I am confused? If the point of a cross over is to equalize the exhaust pressure pluses, then why was my stock crossover about half way down the length of my car?

My friend who has raced and a mechanic friend said the crossover was mainly there to equalize the sound of the exhaust pulses and had nothing to do with how the engine runs or performs. I mean, if it had to do with performance, why wouldn't all cars have them? This was the first out of all the vehicles that I have owned, 1 out of 7, that had an H pipe.

I am not trying to tell anyone off, just confused. My 85 K5 blazer had 335hp engine, and had true duels and ran like a top. Till someone jack it,

ChillPhatCat said:

Not saying that true duals are bad, they are really personal preference as I've never seen a study that really says they hurt power output. So I hope you don't take offense by this. But I don't think you can scientifically claim that your mileage went up .4 MPG. There's no way that .4 (1.5%) is outside of your margin of error. For one, nobody pumps back in exactly what they burned on the previous tank, nor does the tank always hold the same amount, since gasoline expands as the temperature rises. On top of that, a million things can influence the mileage within that margin as well, chemical makeup of the gas, air temperature, air pressure, tire pressure, carbon build up in the engine, engine temperature etc. This could be proven in a laboratory setting, but not really on the street unless the gains were more substantial... maybe 1-2 MPG.

Click to expand...

No offense taken, just happy to get above 25

ChillPhatCat said:

Not saying that true duals are bad, they are really personal preference as I've never seen a study that really says they hurt power output. So I hope you don't take offense by this. But I don't think you can scientifically claim that your mileage went up .4 MPG. There's no way that .4 (1.5%) is outside of your margin of error. For one, nobody pumps back in exactly what they burned on the previous tank, nor does the tank always hold the same amount, since gasoline expands as the temperature rises. On top of that, a million things can influence the mileage within that margin as well, chemical makeup of the gas, air temperature, air pressure, tire pressure, carbon build up in the engine, engine temperature etc. This could be proven in a laboratory setting, but not really on the street unless the gains were more substantial... maybe 1-2 MPG.

Click to expand...

really! mine went from 27.4 to 27.6mpg's hwy.......
true. the only real way to get the best guesstament on mpg's would be taking an average reading over multiple tanks.

midnightdriver said:

I am confused? If the point of a cross over is to equalize the exhaust pressure pluses, then why was my stock crossover about half way down the length of my car?

My friend who has raced and a mechanic friend said the crossover was mainly there to equalize the sound of the exhaust pulses and had nothing to do with how the engine runs or performs. I mean, if it had to do with performance, why wouldn't all cars have them? This was the first out of all the vehicles that I have owned, 1 out of 7, that had an H pipe.

I am not trying to tell anyone off, just confused. My 85 K5 blazer had 335hp engine, and had true duels and ran like a top. Till someone jack it,

Click to expand...

First of all, by eliminating the crossover doesn't mean that you'll suddenly lose 50HP. The power differences are minimal, however there remains to be a difference.

Second, Im not an expert on the dynamics of pressure diffusion, however I doubt that there is a specific location on where the crossover needs to be placed (within means).

Third, Ford is one of the only car manufacturers (if not the sole manufacturer) that designs and impliments an odd-firing sequence in their engines. In fact, I know for a fact that all of GM's engines are even-firing engines and therefor do not need a crossover. Even Fords V6 motors had an even firing order.

The odd-firing order of the 4.6 Mustangs is the same as the old 5.0 Mustangs. This firing order also happens to be the same as the old 351W. It's the odd firing order that makes the "Mustang sound." If you ever hear a stock 351W Mustang from the '60s, you'll notice that the overall tone is very similar to that of our cars.

That being said, a crossover was (I believe, correct me if I'm wrong) an innovation from Ford in the '60s that was said to help increase exhaust scavenging by helping to equalize pressure between both cylinder banks. There was a point with my '86 GT at which I had a crossover, but I had true duals on that car for the most part. I never really noticed any difference in fuel economy or power with either setup. However, it most definitely affects the sound. That car probably sounded the best when it had Hooker SuperComps and a true dual system dumped. My friend has a '65 fastback with a built up 10.5:1 289 with the same exact setup, and it really does sound good.

So mostly it just comes down to sound.

Nightfire said:

First of all, by eliminating the crossover doesn't mean that you'll suddenly lose 50HP. The power differences are minimal, however there remains to be a difference.

Second, Im not an expert on the dynamics of pressure diffusion, however I doubt that there is a specific location on where the crossover needs to be placed (within means).

Third, Ford is one of the only car manufacturers (if not the sole manufacturer) that designs and impliments an odd-firing sequence in their engines. In fact, I know for a fact that all of GM's engines are even-firing engines and therefor do not need a crossover. Even Fords V6 motors had an even firing order.

Click to expand...

Hmm.... Interesting, are there any advantages to being odd fire or is it mainly ford trying to be differrent?