Project: The New CDD Shop Truck

[YJMike92]

What kind of boost should I expect from a stock turbo? On my recent trip to the east coast. my waste gate control rod came off which opened the wastegate which killed all boost. Since I was several hours into the trip I rigged the wastegate shut. The most boost I saw was 15lbs In the West Virginia hills. It was heading higher until I took my foot out of it because EGT temp was about 1150.

 

[YJMike92]

That’s awesome, I guess think of it like a carburetor fuel system, realistically you only need some positive pressure feeding the carburetor (injection pump) for it to perform properly, but you get a more consistent result if you have 5-6 psi through the rpm range

Got it. Thanks

 

[Thewespaul]

I’ve gotten 27 psi with a big pump, but noticed no power difference between 20-27 psi. It just really hit a wall past 20 psi, seemed to quit making power there. These turbos are a pretty antiquated design, and are real small for this big of an engine.

 

[saburai]

IM(very)HO, 15 psi is about max for a engine w / o studs.

 

[Thewespaul]

Most I go on customer trucks is 12, if they have plans on studding it anyways, and they are well aware of the risks and accept them, I will go to 15. No higher

 

[YJMike92]

Most I go on customer trucks is 12, if they have plans on studding it anyways, and they are well aware of the risks and accept them, I will go to 15. No higher

I got nervous at 15 especially not being close to home. That's why I got off the throttle. IDI is all still new to me. I feel like the stock actuator is faulty. It begins to open @ 5lbs. Rigged my radiator pressure tester so I could test the actuator. I ordered an adjustable actuator from Amazon not sure how that will work out. Any thoughts?
https://www.amazon.com/gp/product/B07FMB66RK/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

 

[Thewespaul]

I’m sure you could make that work, I prefer to use a manual boost controller inline to the wastegate line

 

[YJMike92]

I’m sure you could make that work, I prefer to use a manual boost controller inline to the wastegate line

I'll give this one a try. How is your manual controller activated?

 

[saburai]

You could try disconnecting the wg and plugging the hose I only got about 12# on Diego and that's with a baby moose and a fresh turbo. On Raylan, the new truck, which is studded, it's disconnected and I made an adjustable accuator rod. If conditions are right, it'll hit 15-16 which is good enough for me. Of course YMMV...

Edited to add:
Sorry Wes, didn't mean to hijack the shop truck thread

 

[Hydro-idi]

I’ve heard that 13 psi is about the max without an intercooler. From what I understand, the charged air becomes super heated from the turbine & loses most of its efficiency very quickly. If your looking to gain effective boost beyond that #, an intercooler is recommended.
Of course, studs are pretty much mandatory for a 6.9 imo. A 7.3 idi will handle stockish boost with new HG’s and stock headbolts, although arp’s are a big bonus.

 

[Thewespaul]

No hijack here, I enjoy the discussions!

What I have found as far as the turbo super heating the intake is you will know once it reaches that point because egts will stop going down even though you continue adding boost. Every turbo seems to hit it at different boost levels, probably depending on wear. Intercooler is definitely a great upgrade, usually 15 psi is 12 with an intercooler, and if you turn a stock pump all the way up you you can get to 14-15 with an intercooler

 

[saburai]

No hijack here, I enjoy the discussions!

What I have found as far as the turbo super heating the intake is you will know once it reaches that point because egts will stop going down even though you continue adding boost. Every turbo seems to hit it at different boost levels, probably depending on wear. Intercooler is definitely a great upgrade, usually 15 psi is 12 with an intercooler, and if you turn a stock pump all the way up you you can get to 14-15 with an intercooler

That's basically my plan, maybe a bit more with a slightly bigger pump.

Just gotta get the body functional enough to turn a wrench...

 

[YJMike92]

No hijack here, I enjoy the discussions!

What I have found as far as the turbo super heating the intake is you will know once it reaches that point because egts will stop going down even though you continue adding boost. Every turbo seems to hit it at different boost levels, probably depending on wear. Intercooler is definitely a great upgrade, usually 15 psi is 12 with an intercooler, and if you turn a stock pump all the way up you you can get to 14-15 with an intercooler

No hijack here, I enjoy the discussions!

What I have found as far as the turbo super heating the intake is you will know once it reaches that point because egts will stop going down even though you continue adding boost. Every turbo seems to hit it at different boost levels, probably depending on wear. Intercooler is definitely a great upgrade, usually 15 psi is 12 with an intercooler, and if you turn a stock pump all the way up you you can get to 14-15 with an intercooler

I'm trying to understand here. As I mentioned I was at 15lbs boost and EGT at around 1100-1150 on a long uphill grade guessing 2000 ft above sea level. I got off the throttle because of the temperature. If I had stayed on it would there have been a point EGT could or would have gone down?

 

[saburai]

I'm trying to understand here. As I mentioned I was at 15lbs boost and EGT at around 1100-1150 on a long uphill grade guessing 2000 ft above sea level. I got off the throttle because of the temperature. If I had stayed on it would there have been a point EGT could or would have gone down?

Good question! I'm relatively new to diesels, and I've never had the guts to hold on past 1000 for any length of time. For me, it seemed that egts went up faster than boost. Being a conservative guy I of course backed off...

 

[Thewespaul]

Egts can be tricky to explain, but the two biggest contributors to high egts are too much fuel and a restriction of air flow. The reason why you hit a brick wall past a certain point with these turbos is the hot side wheel. The cold side which compresses air into the intake, is big enough to supply 26-27 psi, especially with the 60-1 mod, but the hot side cannot flow enough exhaust to support that kind of boost level. You start getting higher egts because more and more exhaust gets left in the combustion chamber, not allowing cool, intake air in. This restriction for the intake air brings your boost level up. This is why boost does not equal a higher power level, it’s just a measurement of restriction in the intake. I am making more power at 14 psi now than I was at 26 because of this.