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The KOJO Tune - Available now!

Dan, if you're willing to "Kojo tune" your rig, I wonder if it is worth the pain to do the optic bump.
I believe the -1.94 TDCO setting will electronically do the same and fit better with the tune.
-1.94 + optic bump should make the pedal accelerator more sensitive and could be unpleasant for daily driving.

my .02 ;)
 
matuva said:
Dan, if you're willing to "Kojo tune" your rig, I wonder if it is worth the pain to do the optic bump.
I believe the -1.94 TDCO setting will electronically do the same and fit better with the tune.
-1.94 + optic bump should make the pedal accelerator more sensitive and could be unpleasant for daily driving.

my .02 ;)
Click to expand...

Matuva is a very smart man.
 
Not to rock the boat but KOJO's sig mentions an optic bump. He would be the one to make it work though.
 
I really have optic bump in my burb and it gives more performance with -1.94 tdc offset than any of those separately, but if you move too much that optic sensor it really messes idle and makes throttle too sensitive. Also if you prefer 100% drivebility i would not do it..
But if you dont do too big bump it is ok, especially if you have torque converter with lower stall speed then stock (GM uses same tc in 454 and 6.5).

Kane has made lot of testing with optic bump and tdc offset. He has also tested engh's chip, stock and my
 
Yes, when you make more bump and learn/teach PCM, it will move TDCO late and you can adjust injection pump again more advance to get it closer -1.94 or a bit less (depends how you like it). But, with kojo chip, I don't have disturbing "too sensitive pedal" symptom cause it's modified. When I changed EM chip... idle was bad = too much bump. BUT, it is working nice with Kojo chip...
BTW, the guy at Dyno said "feels nice pedal response" :smile5:

All in all, I try to find all "things" what I can test myself to learn my Sub features to be best for me... it's just fun :thumbsup:
 
I like my pedal now. And I'm going to order KOJO tune. So if bump or timing change isn't going to give me gains I'll leave it alone. I only want to do what may be necessary to take full advantage of the tune.
 
Detroit Dan said:
I like my pedal now. And I'm going to order KOJO tune. So if bump or timing change isn't going to give me gains I'll leave it alone. I only want to do what may be necessary to take full advantage of the tune.
Click to expand...

That would be TDCO -1.94 from all I've gathered. I'm all for free mods, but have no desire, based on the info i've gathered over the years, to do Optic Bump.

I drive like I have a cup of coffee on the dashboard without a cover that I don't want it to spill. I like to 'load up' my drivetrain before applying deeper throttle to move the weight.
 
I just prefer having it all working correctly, with the proper precision. The optic bump seems like a trick for fooling the PCM, and it may not be reporting accurate data. So I like to just have all the data accurate. Now how do we know the OS is in the "correct" position to begin with? I assume its calibrated when installed but perhaps the "fear" of optic bump could be misplaced if thats not even true.
 
IIRC the OS is set correctly when an idle fuel rate of 8mm3-10mm3 is read by a scanner. IDK if that is how it's done on a pump stand. I can't see any way else to measure adjustment.
 
I get what your saying but the most accurate adjustment would be a determined fuel rate at x-rpm, any physical measurement would vary, even electronics aren't 100% the same.
 
The most accurate adjustment would be comparing reported timing to actual timing. The OS measures timeing off the camshaft reference, so a machine could input a specific calibrated timing reference from a spinning shaft and read what is reported by the OS.
 
I think we are talking about two different things, I'm not talking about timing the pump, I'm talking about initial fuel calibration of the pump. You can do what ever you like on the test stand but once it's put on the engine the pcm determines the timing through time Set and TDCO learn. The Bump is a way to fool the pcm.

They may just visually adjust the OS with the pump on the test stand, then fine tune fuel rate with the resisters.
 
My whole point is that the OS is a timing source, not a fuel rate determination. If the OS is set in a position when calibrated on a test stand, so that it accurately reads the camshaft reference, then when you move it, it may not accurately read the timing. So when you set that TDCO it may not be truly precise either. Kind of like when your CPS is 180 out of phase the timing is reported wrong, but the PCM doesnt code on you for it.

When you do the -1.94 TDCO, at least the PCM knows exactly what is going on, and everything reported is accurate. So timing can be controlled as the PCM program intended.
 
It's true the pcm utilizes the OS for timing, anytime I've heard of a pump being put on a test stand was to "calibrate" it. Whether it's a DB2 or a DS4 that is a fuel rate, not timing.
 
the DB2 doesnt have this timing source, but the DS4 has some complex computer test equipment and Id be willing to bet it checks timing to be in a certain tolerance. Maybe I'll visit the Stanadyne shop and ask them about it.
 
Yes, it has to be within certain specs or the throttle response will will be erratic. That is what happens when the bump is too far. The bump is what this was all about, how it can fool the comp. into giving more fuel yet still be drivable.
 
NVW said:
Yes, it has to be within certain specs or the throttle response will will be erratic. That is what happens when the bump is too far. The bump is what this was all about, how it can fool the comp. into giving more fuel yet still be drivable.
Click to expand...

Right, and my aprehension about the bump is the possible negative affects it could have on timing accuracy and the accuracy of the data the scanner displays. The OS is a timing source and youre messing with it when you bump it. You might gain 3mm3 of fuel, but I prefer knowing that the everything is working as optimally as possible with the electronic injection.

It may not just be erratic pedal response is my point. It may be real world timing inaccuracies, so when the OS is reporting 13 degrees its actually 11.5 degrees or 15, and the TDCO is learns is -1.94, but the pumps actual position may be -2.58 or something, so the electronic injection is not as precise as before.
 
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