My new 1990 HDJ81 (1 Viewer)

[TuffMudder]

Here's the catch can

I'm working on faith here, because my instinct says, "the problem appears to have been fixed, stop screwing with s***!", but you guys know way more about this than i do, so i'm going to stir that hornets nest.

I'll start by switching the pcv hoses back and see if the problem recurs.

If it doesn't, i'll talk with the shop about reworking the intake box.

I'll go to a 4" intake and outlet then necked down to the 2.5" turbo inlet (I think that requires a double boot)
I'm going to keep the 3" snorkel for the time being and compare with and without the snorkel, before deciding on the 4" snorkel

Do i need to move the pcv inlet to the air box or is the current location ok?

Let me know if this is what you guys are suggesting as their have been comments regarding further looking into air intake as well as looking at the fuel system

 

[TuffMudder]

Also @mudgudgeon any suggestions on what filter. I'd like to stay with plate style, but want to go back to dry. Was thinking i'd just get one of the dry high performance filter from aem like their 28-20129. Is that along the line of what you were thinking?

 

[dan1554]

Also, if there is any blockage to the PCV, your oil will exit via the dipstick. Ask me how I know!

 

[mudgudgeon]

Also, if there is any blockage to the PCV, your oil will exit via the dipstick. Ask me how I know!

Or past stem seals, which could also cause smoke

 

[mudgudgeon]

I think the duramax filters are regularly used, and I'd guess are readily available to you.

 

[TuffMudder]

I switched ports on the pcv hoses and it made no difference. I then put the ac delco back in and ran it up some hills and on the interstate and no problems.

Im wondering if this was something simple that occurred during the install, a collapsed hose was mentioned, that was then sorted during trouble shooting.

Possibly?

 

[TuffMudder]

@mudgudgeon Regarding your comment in the intake thread. I was never trying to get more power from this mod, I'm wanting to increase air flow to lower egts. I realize the exhaust would have been a better place to start, but I ended up doing this ass backwards

That being said, am I barking up the wrong tree thinking changes to the air intake will effect egts?

 

[IanB]

@mudgudgeon Regarding your comment in the intake thread. I was never trying to get more power from this mod, I'm wanting to increase air flow to lower egts. I realize the exhaust would have been a better place to start, but I ended up doing this ass backwards

That being said, am I barking up the wrong tree thinking changes to the air intake will effect egts?

Air intake is not your bottleneck right now, given your boost level and stock turbo, so I wouldn't expect it to make much difference at all. Exhaust will make a decent difference though.

 

[TuffMudder]

Thanks Ian. i've got the intercooler going on a week or so and then will get prices on a 3" exhaust.

 

[IanB]

Intercooler is another thing where the results are going to be underwhelming if done before opening up the exhaust, as it's not addressing the current bottleneck. Intercooler likes a hotter tune to get the most out of the increased cooling as well.

When you do your exhaust, you'll see the benefits and/or shortcomings of your intake side upgrades at the same time, I expect it will be pretty dramatic even without an intercooler.

If you want to bring EGT's down then the engine needs to be able to let the heat out. Do a dump pipe and 3" mandrel bent system, run inside the frame rails, and put a free flowing muffler on it. I'd do this before adding an intercooler, as an intercooler adds a lot more points for failure while you're trying to get this thing running properly, it just muddies the waters and should wait till you're satisfied everything is good to go. You need to check your tune and make sure there's nothing fxxxy going on there as well, you shouldn't be able to hit those kinds of temps just trying to drive at highway speed.

Edit: you kind of skipped a step in going straight to the airbox without doing the exhaust, I'm not sure I've ever seen anyone go about things in this order before, lol.

 

[TuffMudder]

Edit: you kind of skipped a step in going straight to the airbox without doing the exhaust, I'm not sure I've ever seen anyone go about things in this order before, lol.

Yeah, I always end up doing things out of order and it's typically due to impatients. It's a character flaw

 

[mudgudgeon]

I think Ian is right on the money.

Exhaust and an intelligent tune will have the most impact in your rig right now. Both in terms of performance, and improved EGTs.

Talking bottle necks, climb under your truck and have a look at the factory installed bottle neck where the stock exhaust passes over the rear diff and frame.
If that's not begging to be changed, I don't know what is

 

[TuffMudder]

yeah, i saw that. If i'm trying to tuck the exhaust inside the frame rails, do i need to wait until the sliders are attached or is that not an issue?

 

[TuffMudder]

Do the hdj81's have a clean filter monitor on them stock? Mine doesn't have one, so wanted to check. If they don't, did any of you add one?

 

[IanB]

Do the hdj81's have a clean filter monitor on them stock? Mine doesn't have one, so wanted to check. If they don't, did any of you add one?

I think that's mostly an Aussie spec thing, maybe some other markets but not HDJ81's.

If you run the exhaust inside the frame rail you shouldn't have any issues with adding sliders at a later date as long as you leave a bit of room between the exhaust and the frame rail for the brackets to slide in.

 

[TuffMudder]

That's good, i'll stop to check on pricing today and see if i can get that scheduled

 

[TuffMudder]

I went by a local muffler shop. This is a shop that mainly does custom exhaust for off road and drag applications along with various performance mods and has a dyno service.

He wants me to wait until i have the sliders on and bring it back, so i'm back to that delay, but i also had some concerns. Mostly things that contradict what i've already hear about going to a 3" exhaust. I will say, he's had that shop for over 15 years and he has a great reputation in town.

I asked him about mandrel bent and he can't do it in house and said it would add a lot of cost and you didn't loose anything compared to the well bent exhausts he did in house.

He initially said he would do the exhaust from the first flange (within 12 inches of the turbo) back, but he wouldn't take the exhaust off the turbo housing because of the tendency for the bolts to be backed in so hard that taking them off had too much of a risk of ruining the turbo. (@Crab Sack, did you remove the exhaust from the turbo housing when you rebuilt it?). I got the impression, i could convince him to do it, but i'm always leery of the end result when you have to talk someone into doing the job.

Regarding the dump tube, he said 3 inches wouldn't help. He said the fan was only about 2 1/4" and blowing so fast that as long as you got to 3" within the first foot, the extra diameter up close was unnecessary.

When he saw the crimped bend over the back frame, he said he wouldn't need to flatten it nearly as much, so it would flow better. He was a little skeptical he could get a smooth bend over it with enough clearance, but in the end said he could probably manage it.

To the best of my knowledge, this is the only guy in this market within 70 miles. Is he correct on the above?

 

[mudgudgeon]

Hmmmm, fiind another shop.

IMO by not changing the dump pipe, you are giving away a LOT.
getting exhaust clear of the turbo with no restriction is important.
Also the factory dump pipe pages the exhaust it through the wheel well. With a custom dump pipe, you can run the exhaust on the inside of the frame rail all the way to the back of the rig. 100series turbo diesel exhaust ran this way.
This reduces the number of bends required, and reduces the bends to around 45degrees vs 90 degrees with the stock route.

3" will fit everywhere, it's tight at the transfer and tight above the rear diff, but 100% achievable.

I would definitely go mandrel bends, and full flow mufflers.
Check out my exhaust for my turbo build linked in my signature, this is on a 105 series, but chassis is virtually identical to 80series

 

[TuffMudder]

Yeah, that's what i was afraid of. I tried to suggest things in each area, but his responses included things like if you want a 3" dump at the turbo, someone else will doing it, but that softened to I guess i could do it but it would be stupid and a waste of money. He's a nice guy, but he seems set in his ways (he looks to be in his early 40's, that statement made him sound 70).

Just out of curiosity, does anyone know the diameter of the turbo fan? His explanation was that the turbo blows a hi velocity stream that is under 2.5" in diameter

 

[IanB]

It's only ever going to flow as well as the bottleneck, you don't want that to be your dump tube.

This is a guy who I'm willing to bet has never even seen a 1HD-T before, let alone done exhaust on one to know what works best. If he's not willing to build what YOU want, find someone else.