Turbo experts... where's the boost?

[DrCharles]

As you may have seen in the "Great deal on a new turbo" thread, I elected to just buy the $209 center section (CHRA) instead of the $595 complete turbo. It's in and working, but as those old Wendy's commercials used to say, "Where's the beef boost"?

I have an IP and injectors of unknown age. Pump is turned up two flats, wastegate actuator shortened three turns, and it used to make lots of smoke when floored with the old turbo, or at low rpm below boost. During the installation of the new one, I found a leak at the snail-to-intake junction, and there may have been a small one at the sliding wye joint. I coated the surfaces with ultra copper RTV and let it set up before starting the engine.

Today (60 degrees out!) I did some testing. I could only get to 6 psi boost. I tried shortening the actuator rod another three turns - still only 6.5. I suspect the wastegate is prematurely opening. So I disconnected the wastegate and tied it closed. Now I can get 9-10 psi. Has anyone seen a weak spring on the actuator cause this? It sure takes some force to extend it and put it over the wastegate arm though...

On a highway pull at 9+ psi up to 80 mph, the pyro slowly climbs until it's 1150-1200 and little if any smoke. I think the Chinese turbo with my old housings just won't make more than 10 psi, which is OK on my non-studded 7.3 anyway. But am I overfueling, or should I be looking at changing the timing (think the guy who timed it, with a meter, said it was at 8.5 deg but not sure).

I don't feel too bad about spending $209, but the R&R, as you know, is a real PITA so I think I'll wait a while before investing in the Classic Diesel rebuild and upgrade I should have bought ($800 + shipping). Thanks for any tips.

 

[DrCharles]

A couple things I forgot to mention:
1) The truck ('93) was originally a 7.3 NA, 5-speed. I bolted on the complete factory turbo setup.
2) Exhaust has a Gale Banks downpipe (and 3" pipe with one Walker "garbage truck" muffler).

 

[DrCharles]

OK, more driving today. I can get 10.5 psi if I really mash the pedal all the way to the floor. Time to check the adjustment and see if it's really moving the pump arm all the way.

Another interesting observation: the oil pressure (sending unit at turbo oil inlet) is higher! It used to drop off the bottom of the gauge at idle when hot, which is 4 psi or less with that sending unit. (I have a variable sender with the resistor in the cluster jumpered, not the "idiot light without the light that Ford so thoughtfully provided). Now the pressure is well up on the gauge even at a hot idle. That means more oil to the rods and mains

I also noted that with 10 psi boost available (and still no smoke at full boost and wide-open, so I may be able to turn it up another 1/2 - 1 flat), the Facet 40285 pump can no longer keep up with the demand (Fuel Filter warning comes on) during a long pull, flat on the floor

I am planning to reinstall a new mechanical lift pump, and leave the Facet in series, after the mechanical pump. You can suck through the lift pump with no resistance, I checked I like having the Facet for easy priming and elimination of air after repairs, without cranking the batteries/starter to death. But it is marginal for stock boost/fuel and is overmatched with greater-than-stock boost.

If it still can't keep up with the mechanical pushing, out it comes!

 

[hacked89]

Your oil observation is odd. You are saying before you swapped this turbo on your pressure was X and after the swap it’s now X+Y? And you have the variable res sending unit off of the gallery that’s feeding the turbo? How exactly is that plumbed?

 

[DrCharles]

That is correct. I connected to the main gallery at the top rear of the engine, and ran a #4 Teflon braided line to the turbo oil feed with a 180 degree tube AN fitting to line it up with the feed port.

The switch/sender on a stock IDIT is installed at the turbo (on the other feed casting port), so I just installed the physically larger variable sender in the same hole.

So when the pressure comes up on a cold start, I know everything else inside the engine is already lubricated

What the changed reading tells me is that the old turbo bearings were really loose and passing a substantial amount of oil back to the drain - enough so that the pressure drop between the gallery (along the #4 feed line and fittings) was significant. I doubt that the main gallery pressure changed much, but I'll bet it would be measurable if I were curious. Anyway the slightly increased pressure can't hurt!

I'll post a picture later - I just got back from a test run with the mechanical pump feeding the Facet electric pump. Seems to have fixed the warning light problem, but due to impending darkness, the start of rain, and (as always) another vehicle in just the wrong place, I could only do one 45-80 mph run at nearly 11 psi boost. It feels great. I just have to be somewhat careful not to make smoke with too much pedal at lower rpm/load before the turbo spools up.

I think many people are not aware that the injection timing retards as the fuel pressure drops, which is not what you want it to do! There are a couple of threads on this board but I don't have the link handy...

 

[TNBrett]

Here’s my take on what you’re seeing. First off, the factory oil pressure gauge mod is better than stock, but an actual gauge with numbers would be helpful and fairly inexpensive. If the original center section was shot and the pressurized oil was basically falling through it, I can understand your oil pressure improving. If your facet pump is struggling to keep up, remedy that situation before making any other fueling changes. If you want to keep the facet for priming, plumb it in parallel with the mechanical one. After you get the fuel supply issue resolved, hook a trailer to the truck, or put a load in the bed, and see what she’ll do boost wise. You may be surprised. I have to be loaded, or be on it really hard to get maximum boost.

 

[hacked89]

That is correct. I connected to the main gallery at the top rear of the engine, and ran a #4 Teflon braided line to the turbo oil feed with a 180 degree tube AN fitting to line it up with the feed port.

The switch/sender on a stock IDIT is installed at the turbo (on the other feed casting port), so I just installed the physically larger variable sender in the same hole.

So when the pressure comes up on a cold start, I know everything else inside the engine is already lubricated

What the changed reading tells me is that the old turbo bearings were really loose and passing a substantial amount of oil back to the drain - enough so that the pressure drop between the gallery (along the #4 feed line and fittings) was significant. I doubt that the main gallery pressure changed much, but I'll bet it would be measurable if I were curious. Anyway the slightly increased pressure can't hurt!

I'll post a picture later - I just got back from a test run with the mechanical pump feeding the Facet electric pump. Seems to have fixed the warning light problem, but due to impending darkness, the start of rain, and (as always) another vehicle in just the wrong place, I could only do one 45-80 mph run at nearly 11 psi boost. It feels great. I just have to be somewhat careful not to make smoke with too much pedal at lower rpm/load before the turbo spools up.

I think many people are not aware that the injection timing retards as the fuel pressure drops, which is not what you want it to do! There are a couple of threads on this board but I don't have the link handy...

Thanks, I understand your setup.
What you and tnbrett described with the turbo increasing the pressure was also what I was going to respond, but wanted to ask questions before assuming.

You seem to get the idea that it's not increasing your main gallery pressure, I wasn't sure if you were joking or not about more pressure for the rods and mains in your first post.

I've tested running it to a jug bypassing the turbo and it was no pressure differential, cold at least.

 

[DrCharles]

My cold oil pressure also looks about the same as it did before the CHRA swap. Check it out hot, you might find a difference like I did.

I wasn't trying to be funny... I'm wondering if my oil pump is really marginal from wear, and with the extra demand from the worn turbo, it wasn't able to maintain pressure at idle?

Guess it's time to hook up a good mechanical gauge and see the actual psi...

 

[Farmer Rock]

If you continue to pump fuel through the lift pump with the e pump like that, you will blow the diaphragm and flood your crankcase with fuel...


Rock

 

[DrCharles]

How would that happen? I plumbed it so the fuel goes through the mechanical pump first, then through the electric pump, then to the filter...

Or were you referring to TNBrett's suggestion to parallel the pumps?

 

[IDIBRONCO]

How would that happen? I plumbed it so the fuel goes through the mechanical pump first, then through the electric pump, then to the filter...

Or were you referring to TNBrett's suggestion to parallel the pumps?

I saw where you said that. I suppose that he didn't notice it. I think you'll be just fine with the mechanical pump first since you won't be pumping through it at all. You'll be drawing through it if anything.

 

[The_Josh_Bear]

I wanna know what you're asking... 10-11 psi turned up only 2 flats and not WOT smoke is stellar! You should be pumped!

We can generally max out or nearly max with a setup like yours and get up to 15psi with the waste gate unplugged or wired shut. (I've been warned not to wire it shut so as not to overspeed the turbo by @Thewespaul so I don't).
For reference my setup has a maxed stock IP, a charge air cooler and BHAF and I get up to 13-14 psi WOT empty on a mild hill. But because of the waste gate blowing open that's about all I get even loaded or big hills or whatever.

Anyway nice work!!

 

[DrCharles]

The question is, why isn't there more boost with the wastegate line disconnected and the fuel turned up to where the EGT can hit 1200

Since my 7.3 is not studded, that 11 psi seems to be a safe limit anyway. It's a lot more responsive just driving around.

My concern is the EGT which reaches 1200 after a long acceleration in 5th gear (45-80+ mph), truck empty. I expected it to be lower since I'm not overfueling. Although I do have to take it easy on the pedal when the turbo isn't spooled, or I get a lot of smoke. I could max out the pump screw, but then I'd be worried about EGT as well as mosquito-fogging when I don't intend to.

The IP and injectors are of indeterminate age. Right now $1200-1400 to rebuild both is not in the budget, but I'll have to replace them someday...

 

[The_Josh_Bear]

Ok I get it, you're thinking you have the fuel to make 1200 egts so it should be higher PSI. That makes sense.

1. As you mentioned already timing is very important. Bad timing can lead to high EGTs and lower than optimal boost.

2. So can a leak in your up pipes, I'd double check that the RTV didn't blow out somewhere. It works pretty good but will eventually fly the coop. And the loose fit you have may be more than it can overcome.

3. You will always run hotter than a setup like mine with charge air cooling. Hotter intake temps=hotter exhaust. Not saying that's all of it, but could be over 100° of it. I wish I had hard numbers but it's a significant difference.

4. Could be as you mentioned a weak spring on the wastegate. Mine is so strong I can't really move it with my hands, I have to leverage a screwdriver or similar to manipulate it. I'm not a gorilla by any means but fairly strong.
To test this, wire/bolt the thing shut and take a test run. If she easily runs up higher then that's the ticket. Since the IP isn't maxed out you shouldn't be in danger of over-spooling the turbo, and honestly looking at the compressor maps I couldn't find a practical danger zone of that with a stock IP maxed out anyway.

 

[DrCharles]

Thanks. I actually did wire it shut and it made only a small difference, not enough to risk running that way with no protection at all. My spring feels very strong too. I could apply variable air pressure to the actuator and watch the gate arm for movement, but that doesn't tell me how effective each increment of opening is...

I do have an adapter box to measure timing - but I don't own a dial-back timing light Could always calibrate the damper, I suppose. Or I might just experiment with a dime's width one way or the other from the current, allegedly correct, setting.

About the up-pipe joint - that pipe is at least 2" ID. Does a small (say 1/32") leak really affect boost that much? Even if it went all the way around, the total area of that gap would be a tiny fraction of the 3+ square inches of opening.