4" Exhaust Build

[Aldo Orozco]

Nice exhaust

 

[enos1010321]

Hey man I really like it! It's really cool you're doing something different! Don't worry about all these people saying it's overkill, I think it looks great!

 

[Archer Fabrications]

Hey man I really like it! It's really cool you're doing something different! Don't worry about all these people saying it's overkill, I think it looks great!

Nothing is wrong with overkill, as long as there are plans to take somehwat advantage of it in the future hahah. Even if it isnt taken advantage of only thing lost is a little cash, and some addes pounds

 

[PANICiii]

Very nice work

 

[iceguru1114]

This is probably a little OCD, but next time you weld stainless you might want to consider back-purging:

http://www.burnsstainless.com/weldingarticle3.aspx

Also, I don't know how this misinformation got started, but there is no such thing as a desirable amount of backpressure on a 4 stroke spark ignited engine. If you are over-scavenging (which is the reason you might want some back pressure), the route cause is NOT backpressure, it's cam timing; you either have too much duration, too much overlap, or both. On an engine with fixed valve timing, there are points where backpressure can help increase the fresh air content captured in the cylinder, which is good, but it's important to understand that this does not mean that backpressure is a desirable thing; it's simply acting as a bandaid in this scenario.

Another caveat that might lead people to believe that backpressure is a good thing is if you are utilizing inertial pressure wave tuning. Diameter plays a role in fluid velocity which can and will effect which order resonance peak you are able to capture. Smaller diameters increase fluid velocity, which has the potential to decrease the resonance order captured and increase the scavenging effect (in the case of exhausts). However, you still want the largest possible diameter to accomplish this 'ideal' resonance order because these two design targets compete with one another; smaller pipes might decrease your resonance order which is good for power, but they also increase backpressure, which is bad for power.

SO, the goal with sizing exhaust pipe diameters is to go as large as you can before you run into the asymptotic point of no additional gains. However, backpressure is never your friend. If you are seeing gains from additional backpressure on a 4 stroke engine, it is because the backpressure is acting as a bandaid (see first paragraph). The proper solution to this problem is the use of a cam phaser and/or variable valve timing/lift. This brings us full circle to the fact that our engines have fixed cam timing/lift and, thus, at some points of operation, backpressure ends up having a benefit. However, the benefit is comparable someone repeatedly stumbling into an unstable wall to keep it from falling over, then claiming that stumbling into the wall is a desirable solution.

 

[RpVilleneuve]

That is awsome. Especially since you did it yourself. I wish I had some welding skills. I'm going to pick up a welder from harbor freight to start practicing with. Also, I wouldn't call it overkill. Just room to grow !

 

[rough]

I must say, that's one of the best looking exhausts I've seen!! Very clean and should last a very very long time!! Thumbs up!!

 

[____Kurt____]

KYN, that's an awesome exhaust you made there, but how was the clearance around the transfer case and oil pan? I know when I made my 3.5" turbo back it was tight going through that area but then again my 3.5" fit closer to the chassis than any aftermarket 3" I've seen. I don't like the idea of a sloppy "custom" exhaust that just rides an inch or two above the asphalt. I ask because I think I will be looking into a 4" aluminum turbo back exhaust for my custom manifold. Thanks

 

[KYNgsx]

Thanks. The downpipe is as high as it can be before running into clearance issues from above with the subframe.

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My car is pretty low in the front, but the clearance came out pretty good. It's about the same as the 3" exhaust I had before. (I would have to report back later if you wanted a specific measurement of ground clearance, though.)

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The 90 degree bend in the front could tuck a little higher if I used a 3" v-band to 4" tube adapter like this:

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I only found this after already building the downpipe. It would have made it much easier and saved a few steps versus welding the v-band to the 3"-4" cone adapter and then the bend like the way I did it. The lowest point of the exhaust is the rear where the exhaust has to snake around the rear diff and under the drive shaft and rear control arms.

 

[____Kurt____]

You did a nice job, would you be able to get a picture/measurement from the exhaust to ground where it passes under the driveshaft Infront of the rear diff? That is where the lowest point would be. Im glad I work in a machine shop, so I will be able to make one of those adapters.
Thank you

 

[wvdsm92]

looks and sounds great

 

[illestep3]

damn looks awesome didnt think a 4" would fit that good, nice work