First exhaust brake test--- failure

[sk66]

Finally got a compression tester adapted to the exhaust manifold (replaced EGT probe/plate)... I need to make sure the exhaust brake doesn't generate excessive back pressure resulting in hanging valves.
Well, in the driveway I was unable to measure any back pressure; my gauge only has increments every 10psi, but I wasn't even seeing a notable flutter. I decided to give it a test run anyway. So at 55mph coasting downhill I shut the exhaust valve and the exhaust note changed as expected, but I felt nothing of significance... no engine/exhaust braking. I pull over to check the gauge and it's not showing anything either.

The lockup clutch should have been engaged in 4th above ~40mph; I think. If not, this isn't going to be of any real benefit on an automatic... exhaust braking only being effective at very high speeds isn't of that much use; especially if the transmission has to be being driven by the engine for lockup (?).

Next step I'm going to move the brake valve up to the turbo downpipe. It's more hassle, but oh-well. I'm figuring maybe eliminating the entire 2.5" exhaust will cause it to generate more back pressure (less space to compress). I'm a bit disappointed that the results were so poor/inconclusive...

If anyone has any other ideas/suggestions, I'd love to hear them.

 

[Nenw]

I know very little to nothing about these other than what one does. Last week I did get to drive a manual with an exhaust brake and it was very noticeable. The boss of a shop south of Taichung has one installed. Seemed to work at multiple speeds and was very noticeable. It was cool to experience driving one. And given the mountains here seem like a smart mod.

 

[sk66]

And given the mountains here seem like a smart mod.

If I can make it work...
Moved the valve up to the down pipe; still no reading on the compression tester in the driveway... test drive tomorrow. I was anticipating that I might need to make a larger flapper plate that leaked less; but I was thinking I would at least be getting some kind of result.

 

[TimB]

This would be a great mod if it can be made to work. Good luck with it. I used to sometimes drive heavy goods and was always happy to find that my truck for the day had an exhaust brake. They should be standard fitment on anything weighty.

 

[sk66]

This would be a great mod if it can be made to work. Good luck with it. I used to sometimes drive heavy goods and was always happy to find that my truck for the day had an exhaust brake. They should be standard fitment on anything weighty.

Yeah, I've had a few issues with brake overheating/fade... one was near panic and I had to use the emergency brake. I think the L300 is pretty bad about utilizing the rear brakes; particularly with the stock/worn font suspension.

I haven't really had an issue since doing brake maintenance (rotors/pads/fluid/lines) and being more consistently aware/concerned with brake use. But it would at least be nice to only need the brakes for slower curves on long downhill mountain roads... I don't like the smell of really hot brakes (or the risk of a grease fire).

 

[sk66]

Test drive two... mostly a failure. I think it felt like the van didn't want to accelerate downhill like it sometimes does; and there was an audible release of air when I pressed the compression tester relief valve. But there was no braking per-se, and whatever pressure was built up didn't measure as readable on the gauge.

I can easily accept that at low pressures the cheapo compression tester I got is useless. But I also calculated that the open gap on the valve when closed equates to ~ .4 sq in. of bypass; that's almost 1/3 of the OEM exhaust pipe diameter (IIRC), and half of the exhaust pipe diameter required for an 80HP motor...

So I guess I'll move on to making a new plate for the flapper.

 

[Nenw]

Yeah, I've had a few issues with brake overheating/fade... one was near panic and I had to use the emergency brake. I think the L300 is pretty bad about utilizing the rear brakes; particularly with the stock/worn font suspension.

I haven't really had an issue since doing brake maintenance (rotors/pads/fluid/lines) and being more consistently aware/concerned with brake use. But it would at least be nice to only need the brakes for slower curves on long downhill mountain roads... I don't like the smell of really hot brakes (or the risk of a grease fire)

I was really concerned about this considering the amount and type of offroad I was doing. After getting the van I had done a bit of maintenance to my brake system. I had completely flushed the system with new fluid, multiple times in fact. Turned the rotors (still stock), a pad swap (napa gold) front, oem rear, new brake hoses, master cylinder rebuild and new rear wheel cylinders. Almost a totally new system except for the front calipers, but I still had some concerns.

I started digging a little deeper and was completely unaware that it is recommended that you flush the system every 3 years or so for normal driving. I also learned the difference between overheating your pads (brake fade) and boiling you fluid (foot to the floor).

I decided that I needed higher quality pads and fluid. So I started doing some research. What I ended up with was some EBC green pads to fit the stock calipers. Apparently they are out of production now and whatever is in the field is the last of it. These were definitely and upgrade over the Napa pads. Next was the DOT 4 I was using. I ended up using Maxima DOT 4 Racing.

I went with this due to its high boiling point over standard DOT. 600F Dry/400 Wet compared to 510 Dry/310 Wet for Prestone DOT 4.

It was the WET temp rating that got my attention. Even though I knew I was flushing the system regularly, that difference between a fresh fluid and a contaminated fluid was pretty considerable. Considering the big descents, hot brakes, rain, snow, water crossings, puddles, mud, etc. I figured this was a worthwhile expense.

When I flushed my maybe one year old brake fluid with the new stuff, I was shocked at how contaminated it already was. This was very low miles since the last bleed and mostly highway, but I was goofing offroad a little bit. This solidified my concerns, but also highlighted my need to rebuild the calipers or get new ones (still haven't) since it looked like there was a bunch of sediment in the fluid as well.


That all being said, I feel a bunch more secure knowing I've taken some additional precautions. If I ever upgrade to the 2 piston calipers, then I can definitely find some higher quality, high heat pads. But for now I feel like I've got a solid set-up.

The exhaust brake is sick. I was really impressed with the one that I drove. If I spoke mandarin I would learn what I could for you. Google Translate works wonders and if I ever end up back with those guys I would be happy to ask. Regardless, you are pretty dedicated to this stuff and I am certain you will not come away from this empty handed.

 

[sk66]

That all being said, I feel a bunch more secure knowing I've taken some additional precautions. If I ever upgrade to the 2 piston calipers, then I can definitely find some higher quality, high heat pads. But for now I feel like I've got a solid set-up.

Very similar here... upgraded to slotted/dimpled rotors, performance pads, Bosch ESI fluid (365˚), B-line braided lines. I haven't really had any issues since other than the brakes occasionally smelling hot.

But dang, my brake fluid didn't look that bad when I flushed it, and it was probably a decade old.

IDK that I will end up getting anything out of the exhaust brake... I'm starting to think that the transmission has the be being driven by the engine for the lockup clutch to lock. And without transmission-engine lockup an exhaust brake won't do anything. But I am sure that this would work with a manual transmission.

 

[bikerjosh]

@Nenw that is some pretty spent looking brake fluid. Are you sure you weren't sucking in contaminates? I realize it is closed system but that is a lot of contamination in a short time. How was the pedal feel, consistently firm? When I swapped out my front calipers I flushed the system and got a lot of dirty/discolored fluid out but didn't look anything like yours.
On the exhaust brake you saw do you know if they had one on any AT equipped vans? I use the MT on my van for a lot of the braking by down shifting down as far as 2nd when coming to a stop but still interested in additional braking performance.

 

[Nenw]

Yeah, it was pretty bad. I'm certain that I was pulling in contaminants. Big descents, water crossing, then the contraction of the caliper going from hot to cold. I figured it was acting like a vacuum and just pulling stuff in past the seals. I wouldn't be surprised if I flush out some critters one day. That for certain was the worst it ever looked when I bled it.

When I return stateside, I will be doing a full refresh. Right before I left I started losing fluid again in my reservoir and overall performance was garbage. MC, front calipers, rotors, rear wheel cylinders, maybe even the brake booster. When I got the van it was looking pretty bad from a previous MC leak.

I don't know if the shop had any AT vans with the exhaust brake. 95% of the vans here are MT.

My apologies for the potty mouth.

 

[sk66]

I don't know if the shop had any AT vans with the exhaust brake. 95% of the vans here are MT.

Was it a mechanical type (cable actuated) exhaust brake? I would be interested to know what they used; I couldn't find anything purpose made that fit such small exhausts (≤ 2.5").

On a diesel a functioning exhaust brake works better than downshifting (auto or manual); and a jake brake is supposedly better yet.

 

[Nenw]

Any further luck on this?
I may be headed back to the shop one of these days. Anything that you want me to ask or snap some pics of?
Did Evan ever get in touch with you about this stuff?

 

[sk66]

Any further luck on this?
I may be headed back to the shop one of these days. Anything that you want me to ask or snap some pics of?
Did Evan ever get in touch with you about this stuff?

Evan did contact me, he didn't have much to add.
I have made/installed a full blocking plate in the valve and have adapted a boost gauge (smaller range/more accurate) to the exhaust manifold. Just need to install the valve again and give it a quick test...

I would be interested to know what valve they use as I couldn't find anything directly suited. I would have preferred vacuum activation, or even cable because the electrical type take about 2 seconds to travel fully. But it's not that big of a deal and electrical is so much easier to install/run.

If it turns out it won't work at all on an automatic I will move it on to someone with a manual.

 

[sk66]

Some progress today...

Installed the valve in-between the downpipe and my aftermarket (T3/DelicaWorks) stainless exhaust... very pleased that neither part needs modified for it to fit. Now with the modified/larger butterfly I was able to see/generate 20 psi exhaust backpressure in the driveway... that's about the best it cold do under throttle.

At idle the backpressure just flutters around 0-3 psi. As the rpm is increased the backpressure climbs, but still flutters. Then around 12-15 psi it stops fluttering and then tops out about 20. I didn't go to full throttle as the engine was definitely under load and struggling... by 20 psi it didn't seem like more throttle was making much difference. From what I've read, 20 psi is a good/safe number for an exhaust brake.

Based on the way it behaved I'm pretty sure it won't generate more than 20 psi backpressure while decelerating off-throttle... my only concern is that the high temp silicone hose for the boost supply gauge isn't high temp enough to be attached directly to the exhaust manifold, and I will lose my ability to read the pressure in the middle of a test run.

Anyway, I now have a functioning exhaust brake... next is a test run to see how/if it works with the AT lockup clutch.

 

[sk66]

Oh, I forgot the pic...