Worn turbo impeller question, would this affect boost curve?

[Big Red Suburban]

Impeller pic links are below.

I've been thinking of a gear change to reduce my 4.10's to 3.73's or even 3.42's. I pull my boat some (~3000 lbs) and would very rarely pull more, maybe up to ~5000 lbs. I would like an extra mpg if I could get it and I would love to reduce the noise & rpms while running down the highway/interstate.

I've read that the 6.5 is most fuel efficient at 1800 rpms, however as my truck drives now, I think it would struggle to stay in OD when at 1800 rpms.

Don't get me wrong, the truck runs great, after all the modifications it is a totally different truck. It really seems to take off at 2100 rpm and up. With my current setup running steady on flat ground 55mph I've got 1 psi, 60mph 2psi, 65mph 3psi. I got to thinking maybe my turbo is worn to the point boost doesn't build until later than normal, so I took a look (and a picture) and here is what I found.

impeller pic 1
impeller pic 2
impeller pic 3

Could the wear on the impeller cause the boost to be lower than normal at any given rpm? Or does the computer sense the lower boost and close the wastegate more to compensate for a worn turbo?

[ 09-22-2004, 02:33 PM: Message edited by: Big Red Suburban ]

[Beedee]

Hey Big Red
Can't open the pic's with out permission ???????

[Big Red Suburban]

I think I got the links fixed now.

[JeepSJ]

Looks like a whole lot of dirt there on that inlet. If the intake is that worn, I'll bet that the exhaust impeller is probably worse. How do the bearings feel? Wastegate working OK?

[Petrella]

just make sure you get no end play in the shaft, and make sure that the impeller isnt touching the inner housing. the tips of the impeller look like they have been chipped by dirt particles, so make sure your changing your air filter regularly. if you dont get any play in the shaft, i think it will be fine. the impeller isnt chipped bad enough that you would lose boost pressure. i just replaced a turbo on one of my peterbilts cause dirt chipped the impeller and caused play in the shaft and it touched the inner housing, thats a cat turbo that cost me $5000, so if a little dirt screwed that up, it wouldnt take much to screw up the gm turbo.

Anthony
------------------------------------------------
1994 K2500 4x4 Suburban
6.5 Turbo Diesel
Pyro,Tranny,Oil,Diff temp Gauges, Boost Gauge
FSD Cooler from my GM dealer
Sweet sounding JK Exhaust
Boost Controller
Crystal Projection headlights, Turn signals and reflectors.
Euro Tail Lights
Cowl Induction Hood
2" Lift
305/70R/16 BF Goodrich All Terrains
3.73 Limited Slip
American Eagle 16x10 chrome wheels, style 145
Alpine Stereo, Alarm, and Navigation System
Indigo Blue Metallic

[ 09-23-2004, 07:34 PM: Message edited by: Petrella ]

[Turbine Doc]

Red,
You looked at the WG vac/electrical circuit at all, with JK's chip I think you ought to be making more boost, those numbers look like a factory boost curve even with the compressor wheel erosion

[Big Red Suburban]

I just re-read my post and I listed my numbers incorrectly. At 55 its 2psi, 60 its 3psi, 65 its 4psi. These are unloaded, flat ground, steady speed. As soon as I press the accel, boost comes right up. It still makes plenty of boost overall, I've seen spikes as high as 14 to 15 psi, steady at 12 psi I'm just curious if the efficiency of the turbo has degraded some such that I'm losing some boost at lower turbo speeds.

Since I've had the suburban, I've kept the K&N clean. What you see in the picture that looks like dirt is actually oil which has made its way thru the CDR. I think the wear on the impeller is from the PO

When everything is cool, I can grab the nut on the end of the impeller shaft and wiggle the shaft back and forth some, it does not contact the impeller housing. I can't however move the impeller shaft in and out.

My question is this, at any given load and rpm, does the computer send a signal for "x" amount of vacuum to the waste gate or does it continuously adjust the vacuum to the waste gate until "x" amount of boost is seen? If the first case is true, I assume I am loosing some boost compared to a new turbo, if the second case is true, the waste gate would compensate for the worn turbo. I would see the same boost, it would just not be as efficienct of a turbo.

Thanks...

Hey Petrella, do you have any pics of your rig with the 2" lift and tires on it? Is it a body or suspension lift?

[CareyWeber]

Originally posted by Big Red Suburban:
Impeller pic links are below.

I've been thinking of a gear change to reduce my 4.10's to 3.73's or even 3.42's. I pull my boat some (~3000 lbs) and would very rarely pull more, maybe up to ~5000 lbs. I would like an extra mpg if I could get it and I would love to reduce the noise & rpms while running down the highway/interstate.

I've read that the 6.5 is most fuel efficient at 1800 rpms, however as my truck drives now, I think it would struggle to stay in OD when at 1800 rpms.

Don't get me wrong, the truck runs great, after all the modifications it is a totally different truck. It really seems to take off at 2100 rpm and up. With my current setup running steady on flat ground 55mph I've got 1 psi, 60mph 2psi, 65mph 3psi. I got to thinking maybe my turbo is worn to the point boost doesn't build until later than normal, so I took a look (and a picture) and here is what I found.

impeller pic 1
impeller pic 2
impeller pic 3

Could the wear on the impeller cause the boost to be lower than normal at any given rpm? Or does the computer sense the lower boost and close the wastegate more to compensate for a worn turbo?

Big Red Suburban,

How many miles are on your sub?

One place for dirt to enter before the turbo is where the CDR tube goes into the air intake tube there is one hose clamp from the factory, but I installed another closer to the inake tube.

Carey

[Petrella]

i will be taking some pictures of my truck this weekend and ill post them up a soon as i can. my truck has a suspension lift i never touched the body, actually what i did was put a 2 inch spacer between the leafs and the axle for the back. the front i cranked the torsion bars right up and got the front end re alligned. there is a noticeable difference in height, people always asking me how i raised it when im driving on the road when really it was so simple hahaha.

[gmctd]

Could stand a good cleaning, but if no radial or axial contact with housing, it should be good to go.
That's a GM-4, btw.

[ 09-24-2004, 12:30 PM: Message edited by: gmctd ]

[Big Red Suburban]

Currently 173,000 miles. Yes, it is a GM-4 turbo. I was somewhat hoping everyone would agree that it is worn out and give me a reason to replace it with a GM-8 However, in reality, its probably fine, and not worth the money/effort to replace it

[markrinker]

How many miles have you been running the K&N vs. stock paper filters?

[Big Red Suburban]

I bought it with 155,000 miles on it. I installed the K&N filter within a week.

[markrinker]

Safe to assume that the damage happened before the K&N. For wear that bad, it would appear that the filter was compromised at some point - or the filter housing not latched properly.

When I bought truck #1, that filter housing was latched, but the bottom tabs were not engaged, allowing unfiltered air directly into the turbo.