JDL Auto Design - 2014 Exhaust Products

[was385]

Originally Posted by Lee@JDLAutoDesign

The "lip" created by the mismatch in diameter acts as a forward facing step that the flow has to go up, over and around as it enters the overpipe. This causes a really messy flow field with significant regions of reversed flow. To combat the reversed flow the flow in the center of the pipe has to accelerate, so you end up stretching and distorting the flow field, which creates all sorts of nasty acoustic disturbances at a wide range of frequencies (think of the sound a compressor makes when it surges).

Here is a CFD model I made some time ago showing 2D velocity contours of flow from a plenum entering a runner with a 0.090" radius on the entrance. In this case the flow moves from left to right. You can see that the flow in the center of the runner is accelerated and large separation bubbles form on the sides of the runner. This case is a little bit different because the diameter ratio of a plenum/runner is much larger than a collector/overpipe, but hopefully this will make the effect a bit more ~tangible.

Will any aftermarket over pipe have the same diameter? Also can you comment on the heat issues people are having with the fan shroud? Is an uncoated header going to destroy that?

[CTB727]

Originally Posted by weederr33

As I purchased the EL headers, too. This is a bit concerning for me. I didn't realize it would come so close. Do you have any sort of thermal coating on the headers?

Yeah, I have the titanium coating.

Originally Posted by BatStig

The driving isn't going to be an issue. It's the standing still with no airflow that will be the problem.

My shroud did get a little melted, nothing serious, but that was after a session on the track. Now I just make sure to open the hood after a session and everything is wonderful.

I'll keep that in mind between autox runs. So far my shroud seems to be in good shape.

p.s. Your car sounds amazing in those YouTube videos. It convinced me to get EL over UEL

[Lee@JDLAutoDesign]

Originally Posted by was385

Will any aftermarket over pipe have the same diameter? Also can you comment on the heat issues people are having with the fan shroud? Is an uncoated header going to destroy that?

Any aftermarket X.XX" pipe should be the same, give or take the material thickness. At any rate, you wont see an issue like this unless you have a gross difference in size with the downstream pipe being the smaller of the two.

The EL headers i have seen in person didnt seem to have any clearance issues. Ill ask Ronnie and/or Jesse to comment on this since they have personally installed quite a few. Youre fighting radiant heat here so heat shields, reflective tape, etc can all be very effective

[was385]

Originally Posted by Lee@JDLAutoDesign

Any aftermarket X.XX" pipe should be the same, give or take the material thickness. At any rate, you wont see an issue like this unless you have a gross difference in size with the downstream pipe being the smaller of the two.

The EL headers i have seen in person didnt seem to have any clearance issues. Ill ask Ronnie and/or Jesse to comment on this since they have personally installed quite a few. Youre fighting radiant heat here so heat shields, reflective tape, etc can all be very effective

Alright sounds good. My concern at this point is if the guys with thermal coatings are having this issue, does that mean it is pretty much necessary to get a coating on top of the reflective tape, etc?

[was385]

Originally Posted by Lee@JDLAutoDesign

The "lip" created by the mismatch in diameter acts as a forward facing step that the flow has to go up, over and around as it enters the overpipe. This causes a really messy flow field with significant regions of reversed flow. To combat the reversed flow the flow in the center of the pipe has to accelerate, so you end up stretching and distorting the flow field, which creates all sorts of nasty acoustic disturbances at a wide range of frequencies (think of the sound a compressor makes when it surges).

Here is a CFD model I made some time ago showing 2D velocity contours of flow from a plenum entering a runner with a 0.090" radius on the entrance. In this case the flow moves from left to right. You can see that the flow in the center of the runner is accelerated and large separation bubbles form on the sides of the runner. This case is a little bit different because the diameter ratio of a plenum/runner is much larger than a collector/overpipe, but hopefully this will make the effect a bit more ~tangible.

I've been thinking more about this and are we going to see the same effect on any stock component or is it just the overpipe? Said another way, if we have the JDL header and then switch out to a 2.5" aftermarket overpipe, are we going to have the same issues with the overpipe to stock front pipe flanges?

[DocWalt]

It'll be with any stock component except for the midpipe because of the way the midpipe is made where it meets the frontpipe.

What I did to kill the fluttery/wooshy noise was use a 2.25" overpipe so the steps between pipes weren't as bad, then I ported the factory frontpipe flange and removed the silly gap you can see between the pipe and flange:


Once I went with 2.5" all the way to the midpipe the fluttery/wooshy noises went away and I'm left with just the sound of the exhaust rushing through the pipes.

[was385]

Originally Posted by DocWalt

It'll be with any stock component except for the midpipe because of the way the midpipe is made where it meets the frontpipe.

What I did to kill the fluttery/wooshy noise was use a 2.25" overpipe so the steps between pipes weren't as bad, then I ported the factory frontpipe flange and removed the silly gap you can see between the pipe and flange:


Once I went with 2.5" all the way to the midpipe the fluttery/wooshy noises went away and I'm left with just the sound of the exhaust rushing through the pipes.

Alright thanks. The modification of any of the exhaust components is beyond me so going with a slightly smaller diameter OP may just be the best option as I'm not willing to spend the money to change out the front pipe. Didn't really want to do the OP but I guess I'll have to.

[jonkim2]

Pretty much in the same boat. Thanks everyone for your input


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[kch]

So it looks like I should order an OP/FP to go with my UEL header (if it ever comes--the wait is killing me).

If I order an OP/FP now, will they take another 2-3 months, or do those move faster?

[leoh007]

Originally Posted by 2016 Camaro SS

Running the JDL UEL, JDL OP, and JDL catted FP, fitment was absolutely perfect. Even the custom flange to mate with the Perrin catback. Not a single leak, all Grimmspeed gaskets.

You wouldnt happen to have a video would you? This is a similar setup that Id like to use, except I have a Motiv Overpipe. Not sure about Motiv's Catted front pipe since they have the flange that seems to give people problems with the Perrin CBE from what ive read on this thread. Any insight to what Front pipe I should buy? I have an Automatic, not sure if that makes a difference

[leoh007]

Just purchased my Uncatted UEL!!! Cant wait! Order Number #1472. Any idea when I would receive my item? Called and was given a 4 week lead time

[2016 Camaro SS]

Originally Posted by leoh007

Just purchased my Uncatted UEL!!! Cant wait! Order Number #1472. Any idea when I would receive my item? Called and was given a 4 week lead time

Might be even longer. I'm just setting your expectations properly. I would give it about 6 weeks. You will have to be patient, but it is worth the wait.

I do not have a video of my setup yet, but I will try to get one up. This is the setup I'm going to stick with for a long time.

[kch]

Originally Posted by leoh007

Just purchased my Uncatted UEL!!! Cant wait! Order Number #1472. Any idea when I would receive my item? Called and was given a 4 week lead time

I ordered on 12/22 and am still waiting. Their bender is apparently having issues and has really dropped the ball.

[leoh007]

Originally Posted by kch

I ordered on 12/22 and am still waiting. Their bender is apparently having issues and has really dropped the ball.

I just received my invoice number #590. what number were you? I really hope it doesnt take 3+ months to receive this