I just got a Haynes repair manual, and I checked it, and the pic below is all I could find on cam timing alignment. I can't find any mention of a procedure for adjusting the valve lash after a rebuild. It appears as though you just bolt everything back together and that's it? I'm still wondering if the stiffer valve springs used in the rebuild might have something to do with the problem?

 

Is that between 0.005 to 0.010 on each the head and the block or the total for both? If on each, that might've tightened the valve lash by as much as 0.020. I've confirmed that there's no way to adjust the valve lash on the 7.3L except to shorten the push rods! I was reading a thread on Dieselstop about bent pushrods, and a guy stated that if you deck the block and heads that you must compensate by grinding an equal amount off the pushrods. One would think that the hydraulic lifters would compensate for small amounts, and no #'s of thousandths were mentioned, but I thought I'd call this to your attention just in case.

When I built my own race engines (40 years ago) I recall that the valve overlap during the transition between the top of the exhaust stroke and the start of the intake stroke made a lot of difference in breathing at moderate and higher RPMs. I experimented with several custom ground cams, and verified results with timed runs in 3rd gear over a fixed distance between about 3K and 7K RPM. It occurred to me that with a turbo the back pressure is much higher, and that this valve overlap might be even more critical.

 

Ernest there is almost no overlap on the diesel cam. Not enough clearance between the head and the piston crown to allow it.
Look at the pictures of FN74's cylinder head. It's completly flat, no combustion chamber at all and if you find a picture of the piston, it simply has a small depression machined into the center of it.
On some diesels, for instance the ones with pre-combustion chambers, the pistons stick up out of the block a tiny bit and the heads are completly flat on the bottom.
The only clearance that there is, is the thickness of the head gasket.
All of the old VW engines had several different thickness's of head gaskets available and you determine which gasket to install by measureing how far out of the block the piston sticks up.
So if you think about it, there is no room for any valve overlap at all. Both valves MUST be closed when the piston reaches TDC.

 

Well, that works out fine on the compression stroke, but it means that a lot of exhaust gases wind up getting compressed and then resisting the incoming air during the start of the intake stroke, leading to very poor volumetric efficiency compared to a gasser. No wonder you need 20 psi of intake boost pressure to make these things produce any power! Since no more trouble shooting seems to be taking place, I'll hijack this thread for a brief side discussion.

I don't know if you've seen my posts on air flow analysis here, https://www.ford-trucks.com/forums/610048-additional-thoughts-on-psd-air-flow.html#post4719783 and on my new gauge for measuring it here, https://www.ford-trucks.com/forums/615567-more-mods-femco-air-filter-gauge-etc.html , I'll know more when I start towing again, but it's looking like an air flow gauge is the best way to assess and monitor overall engine performance. By that I mean if you start up a grade in 4th and press the throttle, you'll see a rapid increase of air flow into the engine as the boost comes up, then as you push harder to maintain speed, the air flow doesn't increase much more, even though the boost is still increasing, along with EGT, and at that point you can better judge when it's more efficient to downshift to 3rd than by just watching boost and EGT alone.

Now I'm starting to understand all the HP claims by International on their "cam-less diesel" that was tested on a Pikes Peak race awhile back. Since their valves were actuated by high speed solenoids, I guess the valves could stay wide open until just before TDC, and then slam shut! I wonder what happened to this design? I haven't seen it mentioned for several years, and I'm wondering why it never made it into production.

 

BMW is using that technology right now on some of thier production cars. A gasoline engine with no throttle body. They control the amount of "throttle" by carefully controlling how far the intake valves open. I don't know if they are doing it with multi-valve setups, but it would be very easy to make it be a two valve engine for good emission control and tractability and then have all the rest of them open up at WOT for making a lot of power.

 

Oh I wouldn't say that just yet. I don't give up that easily. Just that since the truck otherwise runs fine and has no catostrophic issues, it has moved down on the priority list. 300/500 at the tires is still plenty to get me where I need to go. Even with 10k hooked to the bumper That being said, I had a few extra hours on Thursday and did a compression test that resulted in 400 +-10 psi across the board. Then Friday night just for kicks I put my bone stock turbo back on and went for a drive. Power didn't feel dramatically different, although the truck did smoke more(less air) and max boost was 30, just like prior to rebuilding the motor. So Saturday morning I put the old(new) turbo back on and took the family to Browns Camp to do some camping and riding quads.

I have deffinately been working on my truck too much. I timed my turbo R&R at 35 minutes . In the driveway, with no power tools!!

One other step I did was to go through and thoroughly clean all my major grounding points. I kept having visions of the infamous dim headlight caused by a bad ground. Thought maybe this could happen to the sensors too. No luck though. The engine runs good, does not miss, starts fine, no longer blows coolant, no intermittant issues, no unexpected codes. It is obvious whatever the issue, it is affecting ALL cylinders evenly. My next step I think is to replace the intercooler, and then start replacing wiring harnesses. And I am still always open to other thoughts. Oh yeah, I rechecked my timing again, for the third time, it appears to be spot on. I even cross referanced with my old OEM broken motor.

Stay tuned for next weeks episode of CRANKED!! Mystery of the Ailing PSD

 

FN there are only 2 harnesses under the hood and they ain't cheap. If you dont find any chaffes, cuts, or corroded connectors I wouldn't just replace them.

How much boost are you producing on the new turbo?

 

Alan- I am making a max of 36psi on the new turbo in the 120 setting. about 33 in the 60 tow setting.


So, in this weeks episode, I went online and paid for an online subscription to the Ford Service Manual for my truck and then went through Symptom chart 10, "Lack/Loss of Power". Everything went fine up to KOER on demand test. Got a code P0476, "DTC P0476 indicates an exhaust back pressure control valve performance malfunction was detected during KOER On-Demand Self Test." On repeated tests this code came up. So I start to follow the KB for the EPR(exhaust pressure regulator).

So starting with step "KB7 KOER DIAGNOSTIC TROUBLE CODE (DTC) P0476" and moving on to KB8, this is where things start getting weird. It asks me to hold WOT KOER for 30 seconds. Monitor EBP, should not exceed 28psi. Well I get 28-29 psi. With 4" back exhaust. So this is borderline. Is their something wrong, or is it because of the aftermarket mods?

Moving on to KB11-
KB11 EBP CHECK DURING KOER

• Key off.
• Disconnect EBP sensor harness connector.
• Install ICP/EBP Adapter Cable D94T-50-A or equivalent between EBP sensor and harness connector.
• Measure voltage between signal circuit and signal ground on ICP/EBP Adapter Cable D94T-50-A or equivalent.
• Perform KOER On-Demand Self Test.

Does voltage increase 2.0 V ± 0.5 and then decrease as the test ends?
<TABLE cellSpacing=0 cellPadding=3 width="92%" border=1><TBODY><TR><TH width="50%">Yes </TH><TH width="50%">No </TH></TR><TR><TD width="50%">REPLACE PCM. RESTORE system. CLEAR DTCs and RETEST. </TD><TD width="50%">GO to KB12 . </TD></TR></TBODY></TABLE>


Short answer- No. Voltage only increased by initially 1 volt, then decreased to only .5 volt. What this means, I do not know. Is this reading from the EBP a cause, or effect?

Next oddity. I decided to back up a bit in the KB list to KB1, which is actually for code P0475

KB1 DIAGNOSTIC TROUBLE CODE (DTC) P0475

• possible causes:
  • shorted to power
  • open/grounded circuit
  • damaged solenoid
  • damaged PCM
• Disconnect EPR harness connector.
• Measure resistance between Pin A and ground.

Is the resistance less than 5 ohms?
<TABLE cellSpacing=0 cellPadding=3 width="92%" border=1><TBODY><TR><TH width="50%">Yes </TH><TH width="50%">No </TH></TR><TR><TD width="50%">GO to KB2 . </TD><TD width="50%">REPAIR open in Circuit 570 (BK/W). RESTORE system. CLEAR DTCs and RETEST. </TD></TR></TBODY></TABLE>


well with the Key off, it is less than 5 ohms. Only about 2.7 ohms. Appears good. Except when I try this with the KOEO, I now get 27ohms. Appears Bad. When the fuel pump shuts off, the resistance is only 12 ohms. Better, but still bad. Running another ground wire from battery to chassis makes no differance.

Now I am wondering if my ground floor is not absolutely 0, and therefore skewing all the rest of my sensor data just enough to cause problems. As if that is not enough borderline bad info, I went ahead and checked the EPR coil

KB2 CHECK EPR COIL

• Measure resistance across EPR coil contacts A and B.

Is the coil resistance between 2.5 ohms and 12 ohms?
<TABLE cellSpacing=0 cellPadding=3 width="92%" border=1><TBODY><TR><TH width="50%">Yes </TH><TH width="50%">No </TH></TR><TR><TD width="50%">GO to KB3 . </TD><TD width="50%">REPLACE regulator. RESTORE system. CLEAR DTCs and RETEST. </TD></TR></TBODY></TABLE>
And I get 12.7ohms. good or bad?

This is just getting maddening now. Any chance someone else can possibly perform a few of these tests and let me what know you find? Particularly the battery to chassis ground resistance, with key off and key on.

 

Below, I'm quoting from various posts on this thread which I read again from the beginning to see if I could detect a common denominator for your missing HP. I think I might have, and this is it... AIR FLOW!!! The maximum HP possible can be calculated by assuming that all of the available CMAFF=Cylinder Mass Air Flow Fresh, lb/min combines with the MFF=Mass Fuel Flow, lb/min, and liberates that amount of bth/hr for conversion to HP. If you're AIR FLOW LIMITED, then adding additional MFF only makes small incremental additions to HP, as the additional fuel finds the last few remaining O2 molecules to combust with and liberate a few extra btu/hr. Your dyno runs and turbo R&R's seem to confirm this is your problem, and the cause seems to be excessive TBP= Turbine Back Pressure, psi, which might be a faulty EBPV or just limited by your 4" exhaust?

"...But, FN's engine was built for 400-450 HP, and he's not even close to that on the dyno yet."

"...Also, I finally Dyno'd the thing, and in tow I got 290hp and 505tq, the followed with a 298 and 504tq. on the EXTREME setting I got 299hp and 531 TQ, and followed with a 299hp and 537tq. Seems way low to me, especially the torque. The HP hits 299 and flatlines until redline. TQ is very peaky. Somebody has to know that this means!!???"

The above sure looks like AIR FLOW LIMITED performance, +8 HP, then +1 HP when ALL THAT EXTRA FUEL finally found a few stray O2 molecules to combust.

"...Then Friday night just for kicks I put my bone stock turbo back on and went for a drive. Power didn't feel dramatically different, although the truck did smoke more(less air) and max boost was 30, just like prior to rebuilding the motor."

Again, this appears to suggest an AIR FLOW LIMITED performance because for some reason (possibly excessive TBP) the Garret GT38R BB turbo can't flow much more air than the stock turbo.

"...Left field thought,, have you confirmed the exhaust is clear?"...."HAHAHAHAHAHA, it that were the case it would be one for FTE history!!!! ...All this discussion and work and it boils down to a neighborhood prankster jamming a rock up the tailpipe."

Well maybe not a rock, but any restriction that increases TBP decreases both the VEN=Volumetric Efficiency Net, % and TEN=Thermal Efficiency Net, % of the engine. The next generation of my PSDEM includes additional details of the CMAFF combusting with the MFF to produce the EMGF=Exhaust Mass Gas Flow, lb/min and the EVGF=Exhaust Volume Gas Flow, ft3/min=cfm which depends on EGT=Exhaust Gas Temperature K. As seen in the equation below, TBP is a sensitive function of EVGF, EPD=Exhaust Pipe Diameter, in, and EPL=Exhaust Pipe Length, in.

TBP=[some other stuff][(EVGF)^2][(EPD)^-4][(EPL)]

For a fixed value of EVGF and EPL, TBP decreases by a X2.44 if you increase EPD from 4" to 5", which is probably a much better choice for your higher HP goals, because to get 450 HP you need to increase CMAFF by something like X(450/275)=1.6, and increasing EPD from 4" to 5" will allow an increase of a X1.56 without increasing TBP from its original stock (275 HP) value.

My measurements of AFIVAF=Air Filter Inlet Volume Air Flow, ft3/min=cfm with my new AFAFG= Air Filter Air Flow Gauge agree very with those predicted by my model, and the resulting predictions of maximum RWHP=Rear Wheel Horse Power agree with my two dyno runs. For very little $ and effort (compared to all you've done so far) you can measure your AFIVAF, and provide me some additional information on your set up and I can predict your maximum RWHP.

In summary, it's clear that you've been fighting a number of issues including head gaskets, boost leaks, and now possibly electrical gremlins as well. However, if you don't have (for whatever reason) sufficient CMAFF you can't make the power. Just measuring BP=Boost Pressure, psi doesn't necessarily mean CMAFF. In fact, some of your BP #'s sound to me like the air is just piling up in the CACT=Charge Air Cooler Tube, creating increased BP, but not flowing through the engine and out the tailpipe, which is another place I'm trying to figure out how to measure the EVGF with some kind of a gauge.