EGT temps .. muffler? - EDIT, Have you checked your muffler lately?

[Gizmoman]

Been a while since my last post.
Today I was out for a test run trying out a larger WAIC heat exchanger (was 10 X 10 inches, now 7 X 26 dual core). My typical test run is on the freeway for about four miles pushing it fairly hard. Then off, under and back on which is a steep on-ramp that get's my egt's up into the 1300's rather quickly.

As I was approaching 65 mph, I felt a surge and immediately backed off for a second. The engine sound sort of changed but it seemed to run fine so I finished my route back to the house.

It turns out the muffler had slipped out of the 2 bolt compression sleeve (done it before) just after the turbo 180 bend. I put two small sheet metal screws into each end so that's not going to happen again.

Odd thing was, it seemed my EGT's went up with it off. Any thoughts on why that would be? I didn't run it for long like that so I don't have any hard numbers. It seemed like the EGT temps were more "responsive" to my right foot. It has me wondering if my muffler (some sort of glass-pack affair from the PO) is causing some blockage. Also, I don't know if the EGT's would be lower or higher at WOT without the muffler.

Here is a shot showing what the affair looks like. The pipe is 2-1/2"

[GEE-BEE]

glass packs dont flow, get a bora or flowmaster

I ordered a Bora for the Jetta mk1 build and a installing a flowmaster on the mk1 caddy when it comes out of paint this week
both are 2.5 i.d. and mfg by techtonics tuning

I ordered s/s on the downpipes from TT and they are at the ceramic coater and the complete exhaust is s/s, over kill for the good weather in So Cal.

[Gizmoman]

I agree about the glass pack possibly creating back pressure. I was thinking of cutting one end off to see how it's built just for fun.

I think a straight thru with sound baffles would be best for cooling things down, but I'm also looking for very quiet, 4" OD and 2-1/2 inch ends - tough to find so far

[theman53]

With that turbo and that much pipe at the back it may not be that loud. I found if you can get the tip of the exhaust out 5" or so and possibly turned down some there is not much noise over a full on muffler.

[shorttimer]

Back in the late 60s, a muffler shop I knew, made 'glass paks' and another similar muffler that used lava rock instead of glass. They sold them by the 100s. It was a perforated core with a larger diameter outside tube with rounded ends and the glass or rock was sandwiched in between. Maybe 3/4" material.  He made them in a variety of lengths. They were both a straight through design & only provided a slight notch down on quiet. They were easily fit into a small space. They were just a little too noisy for me.

[Gizmoman]

Does anyone have insight on back pressure, low end torque, lower/higher EGT's?

[Gizmoman]

Yey! The site is finally back up! I was beginning to go through withdrawls!

I found out why my numerous engine mods were less than inspiring (except for the Holset )

Here's a shot of the 4" diameter "glass pack" muffler after I sliced the end-bell off the exit end. . .


Keep in mind, the pipe diameter from the turbo is 2-1/2". I assumed the ID of the muffler was the same - wrong.
Yes, that's 1-1/2". The open area is only 1/4 of what a 2-1/2" pipe is!

EGT's now drop faster and are lower at idle. About 150-200 degree across the board reduction, and take much longer to arrive at 1300F. I'd have more data but I'm redoing my headlight circuit and have the dash apart.

Here's a shot of the replacement muffler - 2-1/2" straight through. It's a good-ol Trush Cherry Bomb. I could have done better but didn't want to wait another week. Besides being sourced locally, it was only 48 bucks.

It a tad louder but not enough to worry about. I'll post a vid when I get the lights working again - always somthin'.

BTW, I should't have titled this thread like I did - very misleading. It seems what I saw when the pipe blew off was EGT's being more "responsive" as there was no restrictions at that moment. Before the muffler improvement, the engine always felt like it was restricted - turns out it was!

[ropadopa]

nice find,  I figured that you may have gained a few pounds of boost hence creating more egt's.??

[Gizmoman]

nice find,  I figured that you may have gained a few pounds of boost hence creating more egt's.??

Yes, I have a DIY boost controller set at 22 psi. It was hard to reach before - fairly easy now. More air = lower EGT's. What I was seeing is the numbers on the digital gauge move faster than they did before the pipe blew off, and it freaked me out a bit.

The fact that it blew off (twice since the rebuild) made me think it may be restricted. Very glad I checked. The pipe in the photo is actually smaller than 1-1/2" with all those bumps in the ID. probably closer to 1-1/4" or less.

I spent big buck trying to get that "restricted" feeling out of the engine. All I had to do was spend 45 bucks on a muffler

[RabbitJockey]

this was a great read.  i can't believe how restrictive that muffler was, or why it was even made like that.  it is even smaller than a stock 1.6na exhaust pipe.

[shorttimer]

From the first pic, of your original muffler, I thought it was like the kind I saw being manufactured back in the day. It's amazing it ran as well as it did with that much restriction. I'll bet your 'seat' dyno feels the difference, too.

[sdubfid]

approx. what rpm do you get to 15psi at? 22psi?

[Gizmoman]

My butt dino is definitely showing better numbers!
After all I have done over three years I was getting quite disappointed - almost ready to give up which is very rare for me. On a positive note, the unknown restriction pushed me to go with a much better turbo, custom intake manifold, and a larger IC heat exchanger. Expensive, yes, but now I have a 1.9 AAZ that is quite "optimized".

As to where the boost is based on RPMs, I'll have to do some tests with the wife taking notes. I have a tach, water temp, EGT, boost, oil temp, charge air temp - all digital - way too much data. My test run with the new muffler was only 4 miles or so, then I started working on the headlight issue which I thought would be a quick fix - not so much.

As soon as it's back on the road, I'll update - maybe even do a video.

All I need now is a beefy transmission to take the hit

[ORCoaster]

Gizmoman,  Clearly deceptive advertising on part of the manufacturer.  Making it all look big on the outside, little on the inside, where no one can see it!   Glad you figured it out.  I have a hunch all the air pushing in finally made this end product reveal itself.  New kind of Pop Off Valve?

[Gizmoman]

I've got no idea how it was advertized - it came with the van. The PO put the AAZ into it and clearly had different goals than I did.

Even when it was a stock 1.6 N/A, it was still choked a bit with that muffler which was not stock at all. Who knows.