How can I tell if my exhaust is restrictive

[Not_An_Abba_Fan]

Just thought I would bring this to the attention of fellow Forum users.

Below is a picture of a well known exhaust.



This is a classic example of the restriction created by a "kiss" pipe. You can clearly see the discoloration of the pipework in front of, and just behind, the kiss pipe, this is because it gets hot. It gets hot because there are two 2 1/2" pipes coming off the cats trying to squeeze the exhaust through a section of pipe that is smaller than 2 1/2". When you cut one of these open, you can see how small the hole is that the exhaust has to get through.

Here is one I prepared earlier.



This style of exhaust creates a lot of back pressure (back pressure is bad, mmkay), and causes the car to lose top end and fuel economy.

[undersuspicion]

nice thread NAAF, very informative gave you rep for it.

[Dr HaxZaw]

good thing we cant tell from the photo what brand it is... otherwise people would stop buying them and then complaining on car forums about how their cheep exhaust has lots of problems

[Zarconia]

Interesting.....

[acarmody]

But, but, but, how could that exhaust be bad.........its so shiny?? LOL.

So NAAB to all the people interested in a new exhaust, do you recommend something else, like completely independent pipes, or a H pipe, or......

[VTSSDUDE]

That kiss pipe sure looks like it would restrict. I am shocked as the maker is a good known brand.

[SUSS8]

But, but, but, how could that exhaust be bad.........its so shiny??

So NAAB to all the people interested in a new exhaust, do you recommend something else, like completely independent pipes, or a H pipe, or......

that is a good question, id be interested in finding out also...i bought my car with the exhaust already on their and it feels restricted. stuck my head under and the cats say VN on them (when was told he had high flo cats) & lukey exhaust & HM headers..... and ive alwais said it feels restricted.

[Not_An_Abba_Fan]

But, but, but, how could that exhaust be bad.........its so shiny?? LOL.

So NAAB to all the people interested in a new exhaust, do you recommend something else, like completely independent pipes, or a H pipe, or......

It all depends on what you want to achieve, what the car is mainly used for and how you want it to sound.

I did a comparison of different types on our Senator. When we bought it, it had a similar system to the one pictured. Sounded like crap and seemed to have no go. I removed the rear resonator and the kiss pipe and fitted a true X pipe just behind the cats. It got louder, but still lacked the punch in the mid to top end. I then removed the mufflers all together and fitted the X pipe further back in the system where the mufflers were and had one pipe out behind each wheel. It got really loud, but it went really well. Off the line it seemed to be the same up until about 2000 rpm, then it accelerated at the same rate all the way to redline. The economy was really good, averaging about 9L/100 on the highway and around 11-12 around town.

The downside was how it sounded. It was too industrial for my liking, I probably should have ran the exhaust out the back through a resonator, but I removed the X pipe altogether, fitted a couple of mufflers and ran two separate pipes all the way, no X, no kiss, and no H. It sounds crisper, but we have lost a lot of economy and bottom end. It goes great from around 3000 rpm, but it feels like you have the handbrake on below that compared to what it was like with the X pipe.

So, to answer your question acarmody, an X pipe in the correct spot will be the best as far as acceleration and economy go, a completely split system sounds the best, and the H pipe system is a bit quieter. If all you want is top end, the H or split system will suit best. But on the other hand, if you are chasing a big dyno figure, take the exhaust off at the headers. There is a way to build a system to get good dyno figures an keep it quiet, but it is custom made and won't be cheap. It will be built based on the type of extractors and the current output as it has to suit the engine.

[itsArthurKomar]

haha thats why im gettin varex muflers for min and the pipe work custom made :P

[undersuspicion]

thanks for the info NAAF. Good reading.

[Not_An_Abba_Fan]

haha thats why im gettin varex muflers for min and the pipe work custom made :P

Varex mufflers are restrictive too. Anything that is in the pipe that interrupts flow is not good.

[HamaTime™]

Very informative NAAF, thanks a bunch

[itsArthurKomar]

no but when varex are open its just straight through,whcih is good. but when close is good for me coz i dont want noise and dont care bout performance coz ill only have it closed up at nights when i come home from work

Varex mufflers are restrictive too. Anything that is in the pipe that interrupts flow is not good.

[acarmody]

no but when varex are open its just straight through,whcih is good. but when close is good for me coz i dont want noise and dont care bout performance coz ill only have it closed up at nights when i come home from work

There is still a butterfly in the pipe, quite a decent size restriction.

[wraith]

Lol @ the guy telling NAAF about exhausts. Interesting right up NAAF. Still plan to pop in and say hello when I'm next over that way.