Adjusting the IP to match the Holset

[Gizmoman]

All four screws are in excellent shape and as reasonably tight as I can get them with a big screwdriver.

I mean the ones you would loosen to adjust the timing.

You did say bolt - I'm going to do some more methodical tweaking to the pump this morning, backing off the LDA spring, checking out the pin position and grind, etc. I may check for boost leaks again with the engine at TDC. If I can still hear an air leak at 30 psi, there's a boost leak at the manifold, or trouble in the valvetrain. It also wouldn't hurt to check timing again - and the pump mounting bolts

The 20 psi stumble is instantaneous though and whatever is causing this is something abrupt - none of the above would give an on/off change (to my knowledge). burn_your_money, earlier you asked if I kept my foot in it during the stumble and I said no. I should clarify that I let off because it was obvious that adding fuel with my foot made the engine act like it was running out of fuel. It felt exactly like a gasser with a bad fuel pump (which I gave felt before).

Not to muddy the water but I should mention that I have never seen smoke from this engine - regardless of any of my adjustments. Is there a "standard" for the number of turns the fuel screw should be set to?

[libbydiesel]

If the boost pin is conical, I would fairly strongly recommend against grinding it.  If it is the AAZ 'joke pin' then grind away. 

When you are checking for a boost leak are all intake valves closed?  You should check for any leaks on the exhaust side as well.

You might consider making a couple runs with the feed and return running to a different fuel container just to eliminate the fuel tank, lift pump, etc, from the mix. 

 

[Gizmoman]

Thanks for the info libby - excellent as always.

Right now I'm trying to stay focused on the simple fact that this engine (since the complete rebuild if it and the IP) has alway hit high EGTs at around 14 psi.
Sure, I can get it to change a tad by tweaking things a bit but nothing I have done has helped significantly. Even changng from the K14 to the Holset and adding a water to air intercooler didn't do as much as I think it should.

Today I found this link and read it entirely https://www.pug306.net/index.php?pageid=boschtuning
Based on that read, the LDA's job is to provide the proper boost to fuel ratio and frankly, the changes I have made to the spring tension or fuel screw has had little effect. I even spun the boost pin 180 degrees and felt no change whatsoever.

I removed the boost pin again this morning (it slides out very easily by the way - no turning required) and looked down into the pin bore and can see no pin sticking out at all. I then made a "feeler" using a thin piece of wire with a short 90 degree bend at the tip. Feeling down the bore, the wire actually goes into a small perpendicular hole about 1/8" deep when I get it close to the bottom of the bore.

I know Giles has an excellent reputation but he's human. Is there a chance he left the pin out or forgot to put it in for some reason?
Or maybe the pin doesn't stick out until I begin fueling.

Here are some photos of where I am right now. . .







I am open to all thoughts.

EDIT:
I looked inside the boost pin bore while I moved the fuel lever to full throttle. It does make a small pin stick out a bit so it is there.

[theman53]

That is not the intake I was thinking of, you should be just fine with that design.
See if you can move the go pedal cable and get the pin to pop out. It looks like a pin was riding on that ramp at some point, so it should be there somewhere.

[Gizmoman]

That is not the intake I was thinking of, you should be just fine with that design.
See if you can move the go pedal cable and get the pin to pop out. It looks like a pin was riding on that ramp at some point, so it should be there somewhere.

I did and the pin is there - I edited the previous post to reflect that.

Thanks for the confidence in the intake build - means a lot coming from you.

[Gizmoman]

I should point out that in the article I linked to a few post back, there is a limit to how much fuel the pump can put out by grinding the pin - mine has obviously been ground. It also states that there are some internal mods that can be done to increase stroke but a pump dyno would be required (plus some good knowledge).
As I mentioned previously, when I sent the pump to Giles several years ago, I told him I was running a K14. A K14 can boos most efficiently to 14 psi before it begins to flatten out (as I understand it).

That said, I believe I may be at the pump max for fueling without Giles or a good rebuilder making more internal changes. If that's the case, without more fuel. I don't see how I can expect more boost. Not that I want to run more than 20 but with the wastegate wired shut, I should be able to exceed 20 with this turbo - unless there's not enough fuel.

Still doesn't explain the 20 PSI stutter.

[vanbcguy]

A stumble like you are describing can really only be a lack of power to the shutoff solenoid or a lack of fuel to the pump.

Sent from my XT1097 using Tapatalk

[Gizmoman]

A stumble like you are describing can really only be a lack of power to the shutoff solenoid or a lack of fuel to the pump.

Sent from my XT1097 using Tapatalk

It seems to be directly related to 20 lbs of boost so the solenoid is out. I have no idea what other thing couls cause such an abrupt loss of fuel - if that's even what it is.

[Gizmoman]

Here's some more info if anyone can use it.

- From the top of the boost pin center stem to the hub edge of the starwheel is currently 0.124"

- when the spring is fully compressed, it is .380" tall

- I measured the depth from the spring seat in the cap to the edge of the cap and got 0.462. Then I measured from the top of the spring (in it's free state) down to the top edge where the cap sits. This came out to 0.301".

This means the current star wheel setting has the spring compressed 0.161". which is far from fully compressed.
The free height is 0.927, compressed height (cap on, current starwheel position), the spring is compressed to 0.766.

So, the pin can travel approximately 0.386" until the spring is fully compressed (assuming the screw on the cap is backed all the way out).

Pin ramp dimensions:
The pin's distance from the top edge of the round section at the end, to the end of the ground ramp is  about 0.52" and I can see where the pin has made a small line up the pin. The pin-line starts just above the top edge of the round.

Also, the ground ramp begins about 0.16" above the round section and it appears that the pin has been going from the original ramped surface and onto the new ground surface during its travel. It leaves the original surface at about 1/6th of it's travel.

I chucked the pin in the lathe and followed the track made by the pin using a similar diameter probe.
The linear travel of the pin shows it has been moving around 0.280". The ramp nets the total movement of the pin to be 0.140" over that travel distance.

[Gizmoman]

OK,
Here I am replying to my own post again but possibly this thread may help someone else.

After studying the grind on the boost pin (probably ground for K14 turbo), I decided I still didn't have enough spring pre-load. So I turned the starwheel even higher (more spring pressure) and it seems to have put things into a better place. The height from the starwheel hub to the top of the pin bore is now only 0.95" [2.41 mm].

A test drive shows I can boost to 20 psi if I floor it and in about 3-5 seconds, the egt's reach 1350F - not nearly as quickly as they did before. Also the stumble and instant boost drop from 20 to 11 psi is gone entirely and I may never know what it was.

All in all, I have learned a lot, especially today.

I believe I could grind my own boost pin to more closely match what I want the fuel to boost ratio to be and back the starwheel off considerably. This would provide a much smoother transition of power than I have now which is fairly abrupt. This hard hit is not being very nice to my drive train, I'm sure.

The pin has a #34 stamped on the end. does anyone know a good source to purchase a new one? I should get several if they aren't too expensive. It may take several different grinds to get it right.

Thanks all.

[burn_your_money]

Try running a new temporary return line from the pump to the drivers seat and back. Keep an eye on the line after some hard pulls to see if you are getting any air in the line. It may take up to 30 seconds for the air to make it to the drivers seat depending on how long the hose is.

What happens after 1350F? Does it stop climbing or do you back off?

[Gizmoman]

Try running a new temporary return line from the pump to the drivers seat and back. Keep an eye on the line after some hard pulls to see if you are getting any air in the line. It may take up to 30 seconds for the air to make it to the drivers seat depending on how long the hose is.

What happens after 1350F? Does it stop climbing or do you back off?

That would take a lot of hose for sure.

As for the 1300, I back off. I have melted the #4 piston on this engine before and and have become obsessive with high EGT numbers.
I spent five years and untold bucks on this one and 1350F is my ceiling.  The warning light comes on at 1100 ; )

[burn_your_money]

Since it's just a temporary thing you could use cheap PVC or whatever hose. It just has to be clear enough to see bubbles.

[Gizmoman]

Since it's just a temporary thing you could use cheap PVC or whatever hose. It just has to be clear enough to see bubbles.

Possible air in the line has been mentioned several times, so doing somthing to identify/stop it makes sense. I probably have enough of the clear hose in a box somewhere. Maybe I could get the wife to watch it while I drive to make sure I don't miss any bubbles. She likes being involved in these projects and this one has kept me busy for sure.

I must say though that since my last increase of LDA spring tension, the stumble is gone. I can also reach 20 psi with egts eventually reaching 1300F. As I won't be pushing it this hard very often, I may just hold off on this project until I can grind a 1.9 boost pin that is a better match for the Holset.

Does anyone know where I can get 1.9 pins?
I have found them on ebay but only in Europe.
Thanks,
Jim

[Gizmoman]

This morning I ran the star wheel all the way to the bottom of the stem - didn't count the turns but I think it was less than 10.
Took it for a spin but was again getting high EGTs and it wouldn't boost over 10 psi.

Back at the shop, I started thinking about using a spring with a higher compression rate and went to my collection of springs. I actually found one with nearly the same ID and a tiny bit larger wire diameter. It was also about 3/4" taller than the stock spring.

I installed the taller spring onto the lowered starwheel, put the cap back and went back out. I boost was now going to 16 max and the flat spot seemed to reappear. I went back, heated the spring under load and shortened it by about 1/2". I dropped it in oil while it was still hot to keep the temper.

The new shortened spring is in now and back to hitting 20 psi without too much effort. Also, The only way I can get it to hit 1300 is to really hold it for 30 seconds or so at 20 lbs. The good news is I can maintain 18 lbs for quite a while and the egts stop climbing at 1250F.

This is about as close to my goals as I could hope for and am going to consider this a successful ending.

Thanks for everyone's  valuable assistance. I'm still interested in grinding a 1.9 boost pin if I can find one and would appreciate a link or a source.

Jim