Need help getting my 12valve tuned

[Soup Nazi]

J,

The stock plug is what determines the total travel if everything else is removed. i.e, rack stop plate, AFC, governor travel is maxed, etc.

Adding a Mack truck plug, machining the stock plug or stacking copper washers...whatever method is used will allow more forward travel if all the other things are allowing it.

That number could vary from pump to pump just from set up and machining tolerances of the pump itself.

In the end, one could add a plug and get more travel, but you can overtravel the rack and ultimately the plunger ( past the spill port ) and just dump the pressure earlier than wanted.

IMO, the stock plug is best!

Rack travel way out there 21mm's is doing very little or no good anyway. The fuel is late in the cylce, the smoke and late burning fuel/heat just goes up and up.

[Eastern Diesel]

Schoust Im trying to get my pump tuned without pulling it back off but if I do have to pull it ill let you know about the rack plug.

[Bobcat698]

I know going from a tuned 887 pump with stock rack plug at 468ccs my egts were HOTTER than with my tuned 180 pump with 2095 rack plug and 640ccs... plungers must be turned too far.

[JGK]

Originally Posted by Soup Nazi

J,

The stock plug is what determines the total travel if everything else is removed. i.e, rack stop plate, AFC, governor travel is maxed, etc.

Adding a Mack truck plug, machining the stock plug or stacking copper washers...whatever method is used will allow more forward travel if all the other things are allowing it.

That number could vary from pump to pump just from set up and machining tolerances of the pump itself.

In the end, one could add a plug and get more travel, but you can overtravel the rack and ultimately the plunger ( past the spill port ) and just dump the pressure earlier than wanted.

IMO, the stock plug is best!

Rack travel way out there 21mm's is doing very little or no good anyway. The fuel is late in the cylce, the smoke and late burning fuel/heat just goes up and up.

Hmmm. This is very interesting. When they showed me the rack travel on my 215 pump with the dial indicator, the indicator was measuring the rack movement through the plug hole - the plug was removed. The rack was moved manually through its full range and 21 mm was all it would go. The head tech said you could run the pump without any plug at all and it would make no difference (presumably, other than a little oil leakage). The plug is just a concave cap (which I saw) and doesn't contact the rack, according to him.

Guess I need to go back and make sure I didn't misunderstand them.

Thanks for your input,
-Jay

[Soup Nazi]

Originally Posted by JGK

Hmmm. This is very interesting. When they showed me the rack travel on my 215 pump with the dial indicator, the indicator was measuring the rack movement through the plug hole - the plug was removed. The rack was moved manually through its full range and 21 mm was all it would go. The head tech said you could run the pump without any plug at all and it would make no difference (presumably, other than a little oil leakage). The plug is just a concave cap (which I saw) and doesn't contact the rack, according to him.

Guess I need to go back and make sure I didn't misunderstand them.

Thanks for your input,
-Jay

If the plug is removed, there is a small machined part that stabilizes the control rod that will fall out. The machined piece is round and has an "L" shape in the center that matches the control rods geometry or "L" shape. The plug holds this piece in place. The piece is called by Bosch a "guide bushing"

If you were to remove the plate, AFC, etc and hold the rack forward using the accel lever you could unscrew the plug and watch the plungers move even further forward or actualy rotate further. At least this is true in the pumps I have built here.

I could see where differing pieces with differing machined tolerance could prove this untrue in some cases.

In the end, the rack/control rod does not need to be that far forward anyway, it is fruitless.

[Hammer]

The guy that did my pump marked where my plate is set at 500cc but that is 18.5mm of rack travel. So I moved slid the plate back some more it should be around 17mm now.

500cc's at how many strokes and with what injectors di he use for your test stand?.Also,at what boost does he have the AFC set to allow the rack to go into full travel.How far up the rpm band does this "500cc" of fuel pull too?.

Personally,it sounds like a tuning issue and a set of mismatched injectors.IF one ran 500cc of fuel with a set of his injector and then you slap the pump in your truck,with your injectors,who knows what its flowing and where its flowing at.Also,the purpose of having a pump done on a stand it to maximize your fuel systems potential,if you do not add all the parts and then go monkeying around with the setup,who knows where your at and what you would make........Andy

[inline6359]

If i have the stock rack plug and no plate will i still lose cc's after 17mm?

How can i measure my rack travel and where?

[JGK]

Originally Posted by Soup Nazi

If the plug is removed, there is a small machined part that stabilizes the control rod that will fall out. The machined piece is round and has an "L" shape in the center that matches the control rods geometry or "L" shape. The plug holds this piece in place. The piece is called by Bosch a "guide bushing"

If you were to remove the plate, AFC, etc and hold the rack forward using the accel lever you could unscrew the plug and watch the plungers move even further forward or actualy rotate further. At least this is true in the pumps I have built here...

Don,

I spoke with the Bosch tech to get a more detailed explanation of this, and you are entirely correct that there is such a bushing. In fact there are two, one at the front and one at back of the pump and they do indeed keep the rack in proper alignment. He said if you remove the foreward one, the rack will drop a bit, so it must be there to keep things properly aligned. In fact, he said running the pump without the guide could cause the forward plunger to come out of index with the rack at full travel and thus when you took your foot off the throttle, that plunger would stay wide open!! Yee haw!

However, he said, it does not restrict rack travel to something less than 21 mm nor does its removal allow it to go more than 21 mm. Rack travel is dictated entirely by the stop pin through the rack at the back of the pump where the other guide bushing is.

As to Smokem's comment about the restricted fueling past 17 mm, he had no comment. He had not actually measured fuel output relative to the helix and spill port interaction at various points of rack travel in that range, particularly with respect to the different pumps (215 with the notch vs 180 vs 160, etc.) So Smokem's observation could be entirely right on.

Inline6359,

I think, if I understand Smokem and the tech's comments correctly, with no plate, or a 0 plate, you will see increasing output of fuel beyond 17 mm. Just that with the 215 pump, it may not be a linear increase compared to the other pumps due to the notch. The increase may fall off a bit more quickly with the 215. But it will flow a huge amount. The tech measured the output of my pump at 418 cc per 1000 strokes at 2000 engine rpm equivalent with the governor lever fully forward in the deepest point in my #10 plate, which was fully forward. The gauge showed 20.1 mm rack travel, just .9 mm shy of smacking the stop pin. Just be aware that running with no plate will allow the rack to hit the pin, and that can break it eventually.

The best way to measure rack travel is through the hole in the front with the plug removed. But, of course, you have to remove the pump! However, you may be able to come up with a creative way of measuring it through the stop plate hole. The tech said that with the plate removed and the fuel lever up, you can move the rack fully forward to its maximum point by pushing the lever forward till it stops. The trick is finding some way to measure this point. Perhaps from the front of the plate hole to the front edge of the lever? I don't know. I haven't tried yet.

-Jay

[Soup Nazi]

The easiest way to see the continued forward movement of the control rod ( rack ) by changing the plug is to:

1) Remove a DV holder and DV
2) Remove the AFC housing and the stop plate
3) Slightly loosen the plug, but dont take it out

While looking down into the plunger, move the accel lever forward and slowly unscrew the plug. You will see the plunger rotate further as the plug is loosened outward.

When we disassemble pumps here, we leave the control rod in the housing before we put it in the cleaner. This makes the afformentioned steps very easy to see. One can insert the guide bushing in the front and install the plug, push the rod forward and loosen the plug and get a good amount of additional travel.

But again, you dont need that much travel in nearly all cases. I use less than 10 on the street with my big pump and under 17 on small pumps

[AsTroSS]

Looks like good time to ask few questions about *big* pump,


Do you have Bosch pn for 13mm barrel/plunger and Bosch pn for best bosch pump cam(or aftermarket)?


My mailbox is open for advices

[inline6359]

**** your mailbox, i wanna hear to.

[JGK]

Originally Posted by Smokem

... Breaking the stop pin in the rack should not be an issue, substantial force would be hard to produce for pin breakage.

But entirely possible. That appears to be what took out my governor. The broken pin was found in the bottom of the governor housing! I have always run with a stop plate, a #10 for the last 2 or 3 years, and not fully forward. So as far as I know I wasn't hitting the pin at WOT. But it broke somehow.

-Jay

[JGK]

Originally Posted by Soup Nazi

The easiest way to see the continued forward movement of the control rod ( rack ) by changing the plug is to:

1) Remove a DV holder and DV
2) Remove the AFC housing and the stop plate
3) Slightly loosen the plug, but dont take it out

While looking down into the plunger, move the accel lever forward and slowly unscrew the plug. You will see the plunger rotate further as the plug is loosened outward.

When we disassemble pumps here, we leave the control rod in the housing before we put it in the cleaner. This makes the afformentioned steps very easy to see. One can insert the guide bushing in the front and install the plug, push the rod forward and loosen the plug and get a good amount of additional travel.

Don,

Yesterday, I asked the tech if he had observed this. He said he had never tried, so it may be true, just that he hadn't done what you described. I wish he had a P-pump on the stand cuz I would have insisted we go tinker! But he said the rack is relatively soft metal (aluminum?) and suggested if the rack was bumping into the plug, or something restrained by the plug, the end of the rack would show evidence of the impacts over time. Have you found any indication on the end of the rack that it is hitting something, and what that might be - threaded edge of the plug, for instance?

Thanks,
-Jay

[Signature600]

I'm guessing I can measure the rack travel on my pump but removing the plug, and putting a dial indicator on the rack??

I've been fighting a low power problem for a long time...since this pump was tuned. 913 pump, 19*, 2095 rack plug, no plate or AFC guts, 022 DV's, DDP4's, 6K Springs = 378hp

So, in my feeble little mind, I'm thinking that:
1. Too much rack travel
2. I can't get the thing to idle or run right below 2500RPM...almost misses, we'll call it a big lope, but above that it smooths out!

So I'm gonna do a little tinkering when I have it off, like putting a new AFC on it, and tuning it, and trying to figure out exactly how much rack travel I have. Any pointers??

Chris

[Bobcat698]

Originally Posted by Smokem

Most views are that if you use no fuel plate the pin in the rack will break, you have always used a fuel plate and yet your dislodged itself correct? I would not call the rack material relatively soft, if the rack has contacted the plug it should be visible in the base.

I had the rack plug install farmed out last year as I didn't have time to do it myself, the shop argued with me that the rack wouldn't hit the stock plug and that they had tested it on another pump.
I told them not to worry about it, just do what I tell them. I enjoyed the look on the tech's face when he saw the wear marks on the stock plug

[Schoust]

How much more fuel would a 160 pump produce with the addition of the Mack rack plug?

[Soup Nazi]

Originally Posted by Signature600

I'm guessing I can measure the rack travel on my pump but removing the plug, and putting a dial indicator on the rack??

I've been fighting a low power problem for a long time...since this pump was tuned. 913 pump, 19*, 2095 rack plug, no plate or AFC guts, 022 DV's, DDP4's, 6K Springs = 378hp

So, in my feeble little mind, I'm thinking that:
1. Too much rack travel
2. I can't get the thing to idle or run right below 2500RPM...almost misses, we'll call it a big lope, but above that it smooths out!

So I'm gonna do a little tinkering when I have it off, like putting a new AFC on it, and tuning it, and trying to figure out exactly how much rack travel I have. Any pointers??

Chris

The funky idle is the gov. Get the crazy springs out and use either a 3 or 4K kit.

Install the AFC, stock AFC spring, and the fuel plate. Install a normal rack plug too. The 181 DV's are fine, but I know some like the other stuff.

[Signature600]

Originally Posted by Soup Nazi

The funky idle is the gov. Get the crazy springs out and use either a 3 or 4K kit.

Install the AFC, stock AFC spring, and the fuel plate. Install a normal rack plug too. The 181 DV's are fine, but I know some like the other stuff.

That's the plan Don...if I ever get parts to put the rest of it back together!

Chris

[KTA-Cummins]

I love the wild CC numbers thrown around in this thread. I had a customer get his pump tuned at a local diesel shop its a 180hp pump with flat top 12mm plungers they told him they had it now fueling to 600+cc's. I said yeah right!! Well he put the pump back on the truck and it cleans up the fuel at 420rwhp. I gave him one of my pumps set at 400cc for a demo, and he had to turn the fuel down to keep from drowning it out. Oh and Don~ is right I am afraid adding the more rack travel isn't going to gain you more power as those extra cc's of fuel come too late in the combustion cycle to add any power. If you need more fuel I recommend going to a bigger plunger and running less rack travel. By doing that your injection event for the same quantity of fuel is shorter so you make more power.

[Schoust]

So Kta are you saying that the MACK plug mod in a 160 pump is not going to net any more power because the extra fuel is coming to late in the combustion cycle??