Optical sensor replaced, now questions...

[greatwhite]

I had my optical sensor fail last week on my 98 K2500 TD.

I had a core pump on the shelf, so I pulled Op sensor out and replaced it in my 98. Now working to scrape together the cash to buy a new one from JK.

I marked the cam ring in the IP before removing the U/S sensor, thinking to just line up the replacement and good to go.

Well, "best laid plans" and all that jazz. Once I pulled the U/S senor out, there was no mark on the cam ring.

Crap.

I guess i saw a shiny line of diesel instead of a score mark.

This just become more difficult.

Pop the replacement on in as close to the original position as I can guess.

Out comes my lappy scanning software. I use carcode on this old rig, seems to be the only one that works consistently on it. Not user friendly, but very complete piece of kit once you figure it out.

Quick scan of calculated idle fuel rate: 2.3 MM3.

Yup, it's waaaaay out.

So, after repeated sucking fuel with the mityvac, adjusting, running, scanning, adjusting, running, etc this is where I ended up:

Time Set 3.9

IPT 11.0

IPTD 10.7

Fuel rate 7.5 mm3

TDCO -1.50

Idle RPM 600

Desired idle 600 rpm

Runs smooth, seems right.

Except:

I noticed something odd on my test drives. I give 'er a WOT run and now the turbo only builds a max of 10 PSI on the gauge.

I'm running a Heath TM at the moment and it's adjusted to around 13 psi blow off. It used to hit the blowoff easily on a WOT run, but now tickles 10 psi if it's lucky.

So, if the TM is still adjusted to 13-ish psi, it must be fuel.

Now, in all fairness, I'm not the first owner so it's possible someone has mucked with the IP before I got it and did an Optical bump on it.

There were some things on the truck when I bought it years ago that indicated someone in the past had tried mucking with things. It's not the orignal IP either:

http://i40.photobucket.com/albums/e235/gr8twhite/c6b77605-0307-4b82-959f-e4f36bbc226b_zps08e1465a.jpg

DS-S5521. Wierd number, but I'm guessing it's a rebuilder unit. Never seen a red Stanadyne tag before either....

I also went from a "7 resistor in the FSD to a #6 while troubleshooting, but that's a near infinitesimal amount of fuel difference.

I flash my own PCM's, so turning the fueling up in the cal is not a problem for me. 10 min job, tops. That would regain boost at WOT and more fuel more power, more boost, etc.

My concern is the difference in boost after setting the optical sensor. It seems to make sense to me if someone had "bumped" it to cheaply up the fuel rates and I set it back closer to stock (IE: 7.5 MM3) that less top end fuel means less turbo boost.

The truck also feels a bit more "sluggish" compared to before I replaced the sensor. Noticeably down on throttle response and acceleration.

Just asking if what I'm thinking is right (about someone having "bumped it" and then I normalized it) before I start dialing up fuel rates/timing in the calibration file to regain top end power and throttle response or if someone sees something wrong with the numbers I've set it at as listed above.

This is the first time I've ever messed with an optical sensor so just looking for a second opinion on my thoughts.

Cheers

[More Power]

There's been some discussion here in the board about optical sensor adjustment. A search should find some of them. For a few 6.5 owners, like you, it can be an interesting excercise to save money or to experiment with different performance values, but it really requires DS4 bench equipment to do it right. I'm all for a DYI project. If there's something to learn, keep us posted... Jim

[greatwhite]

I'm just setting it to the FSM fueling rates by using scanner capable of reading calculated fuel rate.

I've never used a test rig, let alone the Standyne one.

All I can figure they'd be looking at for optical sensor would be miss counts (or total count, same deal different approach), and maybe hertz for the optical sensor.

That should equate to the calculated fuel rate at the specified RPM.

My FSM gives it as:

630-650 desired idle

fuel rate 7-15 mm3

desired inj pump timing 4-10 at idle

I've seen the fuel rate move around as I adjust the Op sensor so I would think getting the fueling rate and pump timing in line with the FSM specs would put the OP sensor where it should be on the cam ring.

I would more than willingly listen to an explanation that counters that theory.

Cheers

[arveetek]

I replaced the optical sensor in my previous DS4, along with giving it a "bump." While it did give me more noticeable power, it also messed with my tranny shift points as well as my cruise control. It's as if the PCM couldn't control the engine speed properly.

After that DS4 finally died, I replaced it with another stock DS4. I'm happy to have my cruise control and shift points back to normal. The Kennedy chip restored the power I had before and then some.

It took very, very little movement of the OS to make a HUGE difference in timing and general engine performance. It got quite old popping the top of the pump off and making hairline adjustments until I was able to live with the results, but I was never able to get it where I was completely satisfied.

I had no equipment whatsoever to show me what I was doing... just had to adjust and test drive to check results! :(

Casey

[greatwhite]

I replaced the optical sensor in my previous DS4, along with giving it a "bump." While it did give me more noticeable power, it also messed with my tranny shift points as well as my cruise control. It's as if the PCM couldn't control the engine speed properly.

After that DS4 finally died, I replaced it with another stock DS4. I'm happy to have my cruise control and shift points back to normal. The Kennedy chip restored the power I had before and then some.

It took very, very little movement of the OS to make a HUGE difference in timing and general engine performance. It got quite old popping the top of the pump off and making hairline adjustments until I was able to live with the results, but I was never able to get it where I was completely satisfied.

I had no equipment whatsoever to show me what I was doing... just had to adjust and test drive to check results! :(

Casey

Yup, get the optical sensor wrong and all kinds of wonky things can start happening.

Problem is, the ecm thinks the ip cam timing is a certain value and in actuality it's different.

It uses the encoder sensor to "time" the injection events properly and when it's "bumped" too much, it doesn't know where anything is so you get all kinds of odd behavior for an APP setting.

"theferminator" on another web site went so far as to say a messed up optic bump destroyed his 4l80e by frigging up the torque management ( I believe that's what he said it was, memory is a bit foggy sometimes!).

I have no problems with shifting, cruise, etc in my truck so far so I'm good there. Nothing jumps out at me in any of the datalogs I've run either.

It really helps when You can adjust the sensor and check the fuel rate on a real time scanner. Gets it really close before you even shift it into drive to check.

However, I'm thinking my idle fuel is just a touch low at 7.5 mm3

This weekend I think I'll bump it up to 8 mm3.

The problem comes when you go the other way, which advances the injection event.

Advancing it screws with the pcm and in particular it's "abuse management". IOW, it doesn't manage the upshifts properly and can roach a transmission.

Guys "bump" the sensor hoping to get a touch more fuel, but I do that by altering the fuel and spark tables and reflashing the PCM.

I just want the Op sensor where it should be in order for the operating program in the PCM to do it's thing properly.

I'm pretty sure I'm good as long as I keep adjusting it by the idle fuel rate.

:)