Diesel Place banner

1 - 12 of 12 Posts

·
Registered
Joined
·
2,481 Posts
Discussion Starter #1
So as alot of you may alread know; I've decided to postpone my full mechanical conversion into *likely* late 2019.

For now I'm keeping the ds4 and accociated intact.

I swapped out my s vin for the f vin intake. WHAT A DIFFERENCE!! should have done that a year ago when I got the darned thing!

*hindsight* :hehe: always better than foresight.

So I think I'm running a bit on the lean side now...

The sensors in the intake are picking up on the extra air and it's temperature drop (quick read with the multimeter on the sensor wires yeild the results. One intake vs the other)

But I'm beginning to think that it would be a good idea for me to trick the ds4 into delivering a bit more fuel via resistor. Just splice the correct wire and use a fuse holder; insert different coded resistors until the goal is achieved. I don't want to billow black smoke, but I don't want so smell burnt injectors either. I think it's running a bit lean.

My first inclination was to splice into the map sensor but thats already done physically by actually adding more air flow. If I were to add a resistor in that circuit the ecm would compensate by delivering either more air or tuning down the fuel rate. ? Maybe both until it leveled out? Who knows. :confuzeld

Wondering if someone may be able to point me to the correct wire? Say in the ds4 harness (assuming)? Where there is a will... there is a way.

I haven't looked into the wiring schematics yet but I know it CAN be done....

Just a matter of finding the correct wire :)
 

·
Administrator
Joined
·
15,600 Posts

·
Registered
Joined
·
2,481 Posts
Discussion Starter #3 (Edited)
Lol. I know THAT! :) those are the pmd resistors.

Not what I'm talking about...

I'm talking about splicing in a resistor inline within a circuit. Particularly a circuit that senses the amount of fuel being delivered that returns to the ecm via ohm value. Raise the ohms, will trick the ds4 into pumping more fuel.

Technically with this method you could force the pump to max out.

Of course... that may trip off the ses. Not something I'm aiming for...

But :thumb: thanks anyway...

Edit: if the pmd resistor is a finite adjustment; then what I am talking about would be the "primary" adjustment. Infinite. Without bounds.
 

·
Registered
Joined
·
2,481 Posts
Discussion Starter #4
Also; was thinking of the map sensor. If you added a resistor inline within that circuit then it would force the ecm into increasing the duty cycle of the wastegate. More boost.... but I don't need to do that. Yet. Lol. I have plenty of air. Gonna focus on fuel for now. :) :thumb:
 

·
Administrator
Joined
·
15,600 Posts
Lol. I know THAT! :) those are the pmd resistors.

Not what I'm talking about...

I'm talking about splicing in a resistor inline within a circuit. Particularly a circuit that senses the amount of fuel being delivered that returns to the ecm via ohm value. Raise the ohms, will trick the ds4 into pumping more fuel.

Technically with this method you could force the pump to max out.

Of course... that may trip off the ses. Not something I'm aiming for...

But :thumb: thanks anyway...

Edit: if the pmd resistor is a finite adjustment; then what I am talking about would be the "primary" adjustment. Infinite. Without bounds.
Experimenting with the resistors to aid in extra fueling was tried unsuccessfully by Kennedy.

IIRC, He went beyond the #9 resistor to try and gain more but the attemps only lead to ECM and performance problems.

You'll have to search #11 or #12 resistor in the threads to find the postings or go back through Kennedys posts
 

·
Registered
Joined
·
7,380 Posts

·
Just add Fuel
Joined
·
548 Posts
I’m not trying to be a jerk here. If I seem a little short, it is just because I don’t have a lot of time.

First, I just want to clarify: Lean does not mean hot. You will not damage your injectors. Diesels run lean normally. Additional air will actually reduce your combustion temps. With the possible exception of running GM-X turbo at 20+ psi and driving your intake air temperatures so high you drive heat into the engine. So don’t work too hard to add fuel just to prevent “burnt” injectors. Not going to happen.

Getting the DS4 to inject more fuel isn’t easy. You can change the calibration resistor to get a very tiny amount. You might be able to cheat the fuel temperature sensor signal to get another very tiny amount – but going very far with the fuel temperature will lead to a derate.

The DS4 fuel system actually monitors valve closure. The PCM commands valve closure time to get a certain amount of fuel. It then monitors the valve closure to make sure the valve closed when it was supposed to. This is a pulsed signal sent back to the PCM. Adding a resistor to this circuit isn’t going to help at all.

As DieselPro suggested, the optic bump can add enough fuel to feel with the butt dyno. This is really the only option you have to get more fuel except for reprogramming… or mechanical modifications.
 

·
Registered
Joined
·
45 Posts
This just my opinion...If at anytime your trying to increase the performance of the DS4 pump, you will have to program your pcm to deliver more fuel and recalibrate the inside of the pump itself to handle and allow the increase in fuel flow. The original pump was built with economy in mind, like the over the road trucks now. The electronic pumps can be modified to deliver more fuel, but he changes have to occur inside the pump. Like the old mechanical pumps you could "shim" them to deliver more fuel, but this adjustment was still inside the pump. This type of recalibration is best left to someone who has a pump stand and can meter the fuel flow through the poppets. I would also imagine the pump shop would have to have the ability to make the parts needed for this type modification. Something has to allow for more fuel flow, larger dia.poppets etc. Increasing the duration of the poppet opening isn't going to allow much more fuel flow because you only have so much time to squeeze as much fuel through the poppets per revolution as possible.
 

·
Registered
Joined
·
256 Posts
As paleyjim said, a diesel almost always runs lean. They do not control the amount of air allowed into the engine, to make less power they simply use less fuel. If you need more fuel because of an intake or turbo modification, get a tune. If you're satisfied with the performance, nothing needs to be done, you won't hurt it by running "too lean"
 

·
Registered
Joined
·
7,380 Posts
The optic sensor (encoder) is what the technician sets the fuel with on the test stand. So if you want more fuel that is the easiest, most sure fire way to get more fuel. Only takes a very small adjustment. If you go too far the engine will surge. And , Yes it will make more fuel than most stock 6,5L's can use efficiently.
https://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/470-6-5-6-2-high-performance-engine-modifications/821770-optic-bump-gains.html

Those telling you it needs a tune or some special programming to make it work have never did an optic bump or trying to sell you something. Of course someone will also tell you that I am wrong, but they have not done it either,
 

·
Registered
Joined
·
5,860 Posts
^^ When Peabody speaks, Guy listens!!
 

·
Registered
Joined
·
2,481 Posts
Discussion Starter #12 (Edited)
Yea I'm not looking to spend any more $ on this particular engine right now. This is the same one that I have all the mechanical conversion goodies for, so spending anything on it at this point will be mechanical conversion related. So what I'm looking for is optic bump. :thumb: thanks guys!
 
1 - 12 of 12 Posts
Top