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WaterH said:
Exhaust is 3”. I’ve heard if I increase the timing, the EGT goes down. But at the risk of popping a head gasket.
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That exhaust should be more than enough. What size injectors are you running? Stock? The original bread truck weighs as much or more and ran non-intercooled for 70k just fine. Increasing the timing will help with MPG's and power. Increasing boost and cylinder pressure is what blows head gaskets. The VE pumps only like a little bit of advance.

WaterH said:
2071 at 55 mph
2636 at 70 mph
It has a 3200 governor spring, but it probably starts defueling before that. To be honest, I start defueling before that. lol.
I would probably do better to run taller gears, but I love the low end.
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For what you are using this thing for, that gearing is fine. I'd tow in 4th gear around that speed in my old truck. It cooled the EGT's down after 2500 rpm. If I lugged it in 5th at 75, around 2100, the EGT's would skyrocket.

WaterH said:
The question was rpm, not EGT. I have never had a EGT above 1500. (I back off if I see 1400)
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I maxed out at 1250 EGT pre turbo.
 
Only time I have had high egt in that era Cummins is when an injector went bad. Ran and idled fine. Put it under big load and the turbo would start to glow red. Changed the injectors and the problem was solved.

A ir gun and checking manifold temps at each hole would give you an indication if one is over fueling compared to the rest.
 
bad zuki said:
That exhaust should be more than enough. What size injectors are you running? Stock? The original bread truck weighs as much or more and ran non-intercooled for 70k just fine. Increasing the timing will help with MPG's and power. Increasing boost and cylinder pressure is what blows head gaskets. The VE pumps only like a little bit of advance.
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Stock injectors. I believe bread trucks topped out at 45 mph. As I understand it, increasing timing increases cylinder pressure. I don’t have arp head studs and such, so I’m not keen on doing anything to cause a rebuild.
 
ThePanzerFuhrer said:
Only time I have had high egt in that era Cummins is when an injector went bad. Ran and idled fine. Put it under big load and the turbo would start to glow red. Changed the injectors and the problem was solved.

A ir gun and checking manifold temps at each hole would give you an indication if one is over fueling compared to the rest.
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So when you do this test with the ir gun, does it need to be under load? I guess in my case I could get someone to do it. How did you do it in a conventional truck? Or could you pull over quick and shoot it?
 
WaterH said:
So when you do this test with the ir gun, does it need to be under load? I guess in my case I could get someone to do it. How did you do it in a conventional truck? Or could you pull over quick and shoot it?
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I start it up cold and bump it up to 1800 and watch the manifold temps. One will lag behind the rest giving you a clue that cylinder may be over fueling. It’s not the most accurate deal but it will give you a hint on what’s going on.

You also need to kinda take into account the shape of the manifold as the ones by the turbo will heat up faster than the ends so it isn’t an exact science.
 
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CarterKraft said:
OP, you need to pick a system cooling, fueling, air inlet, exhaust etc. and do single tests to prove pass/fail for each.
You are already getting wack-a-mole suggestions that are just going to tire you out.
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Well, I have driven the truck 30,000 miles. So obviously all of those systems “pass”. But just because something passes doesn’t mean it can’t be improved. Small gains are still gains.
 
CarterKraft said:
Damn way to come in her and swing your purse.

You know anything about drive pressure? Its like boost but in reverse...
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As the only person on this website who can calculate and predict it. Yes.

Here's a data point for you.
T25 turbo. 0.49 A/R turbine housing. 4 litre diesel.
2000rpm, 20psi boost, 18psi drive pressure.

Absolutely tiny turbo. Drive pressure below boost. Because the biggest single factor in drive pressure is turbo efficiency.
Get the size wrong (as the bigger=better retards always do) and the efficiency sucks so the boost sucks, so the response sucks, so the drive pressure sucks.

I've been doing this for decades now. Yet still the internet is full of clowns who think the biggest turbo that will barely spool is the correct choice.

It's incredible. They can't even tell the difference between a cooling problem and a turbo problem yet think they have all the answers.
 
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Dougal said:
As the only person on this website who can calculate and predict it. Yes.

Here's a data point for you.
T25 turbo. 0.49 A/R turbine housing. 4 litre diesel.
2000rpm, 20psi boost, 18psi drive pressure.

Absolutely tiny turbo. Drive pressure below boost. Because the biggest single factor in drive pressure is turbo efficiency.
Get the size wrong (as the bigger=better retards always do) and the efficiency sucks so the boost sucks, so the response sucks, so the drive pressure sucks.

I've been doing this for decades now. Yet still the internet is full of clowns who think the biggest turbo that will barely spool is the correct choice.

It's incredible. They can't even tell the difference between a cooling problem and a turbo problem yet think they have all the answers.
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Tell me more about your turbo sizing skills.

800cc gasoline v twin
Looking to make 75 HP at sea level 50hp at 10k

Doesn't have to be here, I have a turbo thread on the SXS sub.
 
CarterKraft said:
Tell me more about your turbo sizing skills.

800cc gasoline v twin
Looking to make 75 HP at sea level 50hp at 10k

Doesn't have to be here, I have a turbo thread on the SXS sub.
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It's about 3 hours solid number crunching for a new turbo match. Petrols are only low boost so not as challenging and there should be enough existing info out there to simply copy.
 
Dougal said:
It's about 3 hours solid number crunching for a new turbo match. Petrols are only low boost so not as challenging and there should be enough existing info out there to simply copy.
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I've gone over a bunch of this work in my thread but I came to my "right" size and the other aftermarket options are completely different hence the rub.
 
So I made a trip down to my other property a couple days ago. It was the same weather (hot AF) as the trip I made their before swapping the airflow direction on the radiator. I drove the same speed. (About 62)

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I can say the water temp went down from 220-225 to under 210. So I definitely say this mod is a win. I’m not saying it still couldn't use improvement.
 
That's a pretty significant drop!

Does the AC still work tittays?
 
WaterH said:
So I made a trip down to my other property a couple days ago. It was the same weather (hot AF) as the trip I made their before swapping the airflow direction on the radiator. I drove the same speed. (About 62)

IMG_1517.jpeg


I can say the water temp went down from 220-225 to under 210. So I definitely say this mod is a win. I’m not saying it still couldn't use improvement.
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Is the blade direction (cup) correct for the new direction?
 
bdkw1 said:
That's a pretty significant drop!

Does the AC still work tittays?
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AC has always worked great on this truck. That’s good because there are some air leaks at the doors. In fact, the main interior noise is from wind/air leaks. If I’m going in a headwind, it’s pretty bad. Tires and motor make less noise than my Bronco. But at 60 mph, it’s a toss up which is harder to carry a conversation in. So far I just turn the music up.

CarterKraft said:
Is the blade direction (cup) correct for the new direction?
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I put the fan and shroud on the other side of the rad, so it’s all correct.
 
So, since my work on the air bag fittings, the truck actually remains the same height and level for weeks at a time. Well, almost, the truck will go down a bit when the temp goes from 95 to 70, but it goes back up again with the temp.

When I was doing that work, I found that the air pump was back leaking my tank down. I thought I needed a check valve. It turns out there is a check valve right at the end of the air pump line. But of course, it was leaking backwards. It was a very small leak, leak never the less.

I ordered a new one and while I was waiting for it to show up, my safety blow off valve decided to blow off at around 80 lbs. The pressure switch doesn’t shut off till 120, so that means the compressor never shuts off. When I went back there to see what was going on I grabbed some of the plumbing. It turns out that compressed air plumbing gets hot. No, correct that, it gets hot AF.

Anyways, I ordered and got a new blow off valve too. I ordered the check valve and blow off valve different days and they came in the same envelope. Hmmmmmm.

New on top, old bottom.

IMG_1521.jpeg


I pulled the #1 battery out to get at the valves.
I couldn’t believe how dirty it was in my battery / air compressor compartment. This was after some cleaning. There’s only small openings to the outside. The dirt and dust just floats in.

IMG_1520.jpeg


After installing them, I started the compressor and let it run till the switch shut it down. So far so good. I listened reall close for the check valve leaking. I didn’t hear it but now I could hear a leak somewhere else. WTF

I sprayed everything down with glass cleaner and no bubbles. Well turns out I didn’t spray everything because it was leaking out the pressure switch electrical spades! So I ordered on of them. Installed it tonite and it appears there is no leak. I wonder if there’s any chance there will be pressure in the morning.

Edit, all this stuff was brand new when I built the truck. Irritating.
 
WaterH said:
I had no idea air systems were so unreliable.
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Not unreliable in the real world, the expectation is not for them to be absolutely perfect. The cost would be 10x or more what it is currently if perfection was expected. You’re gonna have to learn to live with a low airbag truck after sitting a while. All of the trucks that use this stuff have a huge engine drive air compressor so the little leaks are not to be worried about, Comparatively speaking to your little electric tinker toy compressor.
 
ThePanzerFuhrer said:
Not unreliable in the real world, the expectation is not for them to be absolutely perfect. The cost would be 10x or more what it is currently if perfection was expected. You’re gonna have to learn to live with a low airbag truck after sitting a while. All of the trucks that use this stuff have a huge engine drive air compressor so the little leaks are not to be worried about, Comparatively speaking to your little electric tinker toy compressor.
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The compressor did keep up with everything but the blow off valve. Lucky I didn’t burn it up on that. When I was driving, I can’t hear the compressor run. Every once an awhile I would hear this hiss like a big truck air brakes. lol. Should have figured it out quicker.
 
WaterH said:
The compressor did keep up with everything but the blow off valve. Lucky I didn’t burn it up on that. When I was driving, I can’t hear the compressor run. Every once an awhile I would hear this hiss like a big truck air brakes. lol. Should have figured it out quicker.
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I bet you could wire in a time delay timer to prevent hour long run times...
 
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