What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Tuning a GMPP 383

Welcome to the world of glitches... :eek1:

Since it is when going closed loop that would make me check wireing to O2 sensor all the way to PCM. If it all looks good check continuity with ohm meter and wiggle wire looking for a break. Then replace O2 sensor! Sooted O2 from rich makes tuning impossible, contamination from other chemicals can not be seen.
 
eagle mark said:
Welcome to the world of glitches... :eek1:

Since it is when going closed loop that would make me check wireing to O2 sensor all the way to PCM. If it all looks good check continuity with ohm meter and wiggle wire looking for a break. Then replace O2 sensor! Sooted O2 from rich makes tuning impossible, contamination from other chemicals can not be seen.
Click to expand...


Thanks Mark,

I check out the wiring for sure. I did change it out when I changed the fuel pressure and it also convected to 3 wire heated.

I wonder if the ECM itself is going bad from all the chip swaps I've been doing? :dunno:
 
cuervo said:
Thanks Mark,

I check out the wiring for sure. I did change it out when I changed the fuel pressure and it also convected to 3 wire heated.

I wonder if the ECM itself is going bad from all the chip swaps I've been doing? :dunno:
Click to expand...
Anything is possible, although this is highly unlikely.

Back to earlier discussion, opening up BLMs to lower and higher numbers may be in order now that we know (thanks dave) we can do that. If VE is off father than O2 can adjust, I'm guessing this would keep you running. This is the way Dave explained it. Just theory to me as I have never done it. But if Dave said it can be done and works? I have total faith it will.

You've also got a mail order chip from a guy with great reputation, he has lots of hands on tuning experiance so I think it's close!

Heated O2 should stay in closed loop pretty much from a little after cold start on... depending on chip settings. I know I force open loop idle on big cams then let O2 work after I get things close, still have to leave idle open loop because of low vaccum and rich exhaust. Just the nature of the beast. Once rpms raise well things return to normal...
 
Well, it can't get any more embarrassing then this.

Seems 4 out of 8 plug wires were not on all the way. The boot was on the plug but it was not on far enough to click onto the plug.

I tossed in the 106 BPW chip and it ran great, again.
 
I read through the thread again and I didn't see a firm answer on this but:

Should I be tuning/adjusting the VE table off of the Long Term BLM or the Short Term BLM log?
 
dave w said:
Excellent question! Long Term BLM

dave w
Click to expand...

Thanks Dave!

I have a question about deceleration or part throttle issues.

When you are kind of coasting down a hill but have your put just barely on the gas, trying to maintain speed, I get a surge or jerking motion. If I give a little gas or lift off completely it stops. It there someway to affect this in the tune? :dunno:
 
cuervo said:
Thanks Dave!

I have a question about deceleration or part throttle issues.

When you are kind of coasting down a hill but have your put just barely on the gas, trying to maintain speed, I get a surge or jerking motion. If I give a little gas or lift off completely it stops. It there someway to affect this in the tune? :dunno:
Click to expand...

The Decel Enleanment vs Coolant Temp table might help? I think once the VE table is good, the problem should go away. Fix the VE cells first, many things are dependent on a good VE table! I usually don't need to adjust the other parameters once the VE table is good.

dave w
 
I posted same time as Dave. Yes VE tables have to be close/correct first! Most other things make changes based off it!
 
Ok, hair splitting time now. :waytogo:

I'm working a just a few cells at a time now so here is a case on two of them.

First a question: I tow a boat, 4200 lbs worth and I'm sure while towing a boat the truck is going to run leaner then without. I assume I should stay a little rich for this purpose, no?

First cell 2000 rpm 40 kpa

minimum 117
maximum 135
average 126.3

As you can see in the screen shot the cell is green(lean) but the average is 126.3 and the current value for that cell in the VE table is 54.30. If I was trying to move the cell to dead on 128 the correct cell value would be 53.58 but by doing so I might even lean it out more when towing so I'm inclined to go the other way and try to lower the maximum value of 135 down some which would call for an increase in the VE table.

126.jpg


So my question on this cell is increase the value or leave it alone?

Second cell 1600 rpm 40 kpa

This is just a reference to the first question

minimum 117
maximum 134
average 127.2

This cell is only different by 1 point on max and average yet it shows slightly red or rich. I like this and probably wouldn't change it.

That said how can these cells be so close, but the graph show one as lean and the other as rich?

127.jpg


Thanks again, Dave and Mark. You've been a big help on this learn process. :waytogo:
 
cuervo said:
Ok, hair splitting time now. :waytogo:

I'm working a just a few cells at a time now so here is a case on two of them.

First a question: I tow a boat, 4200 lbs worth and I'm sure while towing a boat the truck is going to run leaner then without. I assume I should stay a little rich for this purpose, no?

First cell 2000 rpm 40 kpa

minimum 117
maximum 135
average 126.3

As you can see in the screen shot the cell is green(lean) but the average is 126.3 and the current value for that cell in the VE table is 54.30. If I was trying to move the cell to dead on 128 the correct cell value would be 53.58 but by doing so I might even lean it out more when towing so I'm inclined to go the other way and try to lower the maximum value of 135 down some which would call for an increase in the VE table.

126.jpg


So my question on this cell is increase the value or leave it alone?

Second cell 1600 rpm 40 kpa

This is just a reference to the first question

minimum 117
maximum 134
average 127.2

This cell is only different by 1 point on max and average yet it shows slightly red or rich. I like this and probably wouldn't change it.

That said how can these cells be so close, but the graph show one as lean and the other as rich?

127.jpg


Thanks again, Dave and Mark. You've been a big help on this learn process. :waytogo:
Click to expand...

When the tuning gets to this point, I use Microsoft Excel.

To the best of my knowledge the $85 definition file only has one VE table. So it's likely you don't need to use Excel. What I would do, without using Excel, is recaculate the entire VE Table cell by cell.

Here is my example.
Cell 2000 RPM ~ 40 Kpa = Lt BLM 126.3
(I don't know what value your VE Table has at 2000 RPM ~ 40 Kpa) but for this example I'll use the 56.7.

Here is the Forumal I Would use:
56.7x(126.3/128)= 55.9469 or rounded to 55.9

I would then change the VE Table cell 2000 RPM ~ 40 Kpa to 55.9.

Rinse and Repeat on all other cells!:doah:

The tuning process is not perfect, so it's ok to just change the VE Tables when the Lt. Term average is less than 126 or more than 130.

So for the example above you don't really need to change the VE Table value at 2000 RPM ~ 40 Kpa.

dave w
 
I did make an excel doc to do the calculations using the formula I found on the net. It does make it a lot faster when doing all the cells one by one.

I have noticed that it can take a long drive to get enough data to populate all of the cells and even then you may end up with some cells that have less then 5 hits.

I'll attach my excel doc so if you get some time just double check it for me please. It has both rich and lean formulas in it.

I did some changes using the data from the last log but wont get to drive on it until tomorrow.

Here is the changed VE table.

ve106.jpg


I'm tossing around the idea of lowering the BPW by 1 to see if I can raise the lower cells above 45 but keep the upper cells under 95. It's just so close on each end. IF I must be out of the 45/95 grouping what end should I allow to be out of range?
 

Attachments

  • vetable.zip
    8.3 KB · Views: 1
Last edited:
cuervo said:
Thanks again, Dave and Mark. You've been a big help on this learn process. :waytogo:
Click to expand...
Your welcome and this thread should be a must read for anyone else starting to tune!

Dave is showing off how smart he is! :D

Your BLMs are split around 128. If you try to get them perfect today they will change with weather! So tomorrow you will be splitting hairs again. There is also a learn in the ECM that will help dial this in, the more you drive the closer it gets.

The areas you are showing are also the mid RPM where all engines really start to pull high tourqe! so being a tad rich here is also good!

I always lean (ha ha) towards rich, actaully a BLM of 126. Your showing red, a tad rich, I would leave it. Perfect to stay a tad rich in that area when you are towing to avoid knock.

Towing is just going to be higher MAP. Towing is a great time to record data and tune that area. Also watch or listen for Knock when towing. I have some mountain passes near me I tune on that helps with more load like towing!

Only way to really decide if you need a little more tune is long drives and lots of data with engine warmed up before starting to record data!

I think your there! :woot:
 
There really is just an overwhelming amount of information when it comes to this stuff.

In that one sticky post from Dave asking why people don't do their own EFI tuning I can finally answer that.

It's simple, the amount of learning need to do it some what effectively is a road block, when you think about it. If you are only going to tune one motor, maybe two in your lifetime is it really worth it? You can roll into either of your shops and drop down $350 or $400 bucks and come away in a day or two with a great running engine. Or, you could layout that much in hardware and then spend 5 or 6 months trying to do it yourself.

I have a lot of time and I enjoy the computer part of this entire process. So I didn't mind picking your brains apart trying to get somewhere with it. I know I'm just sipping the waters and there's more to come from the waterfall that is EFI tuning!!
 
Last edited:
It depends on the persons knowledge as well.

You need to be computer literate first, then you need to be a decent mechanic, then you need to know engines and how to tune, then you need to learn all the chip tuning stuff.

Your right about a couple days and $500. Minimum for a non stock engine, easily double that for big build then add troubleshooting mechanical issues like fuel pressure, spark plug wires... spending a couple hundred bucks on a mail order tune get's you close, as you have found out!

In the end you do have a much better running engine that uese less fuel, drives better, gets better MPG not to mention engine life, just look at your oil with a carb after 1500 miles and then EFI after 1500 miles!

I'm just a gearhead so it's where my DNA sent me!:D
 
The on question I had left over was:

When trying to stay within the 45-95 VE range, if I have to go above or below to those numbers in my VE table which one should I over shot first?

IE with current BPW I have to go under the 45 to get close to 128. Would I be better off lowering the BPW to raise the lower cells up to the 45 number even if I have to go over the 95 or am I better off having slightly under 45 and staying under the 95? :haha:

Does that make sense?
 
cuervo said:
The on question I had left over was:

When trying to stay within the 45-95 VE range, if I have to go above or below to those numbers in my VE table which one should I over shot first?

IE with current BPW I have to go under the 45 to get close to 128. Would I be better off lowering the BPW to raise the lower cells up to the 45 number even if I have to go over the 95 or am I better off having slightly under 45 and staying under the 95? :haha:

Does that make sense?
Click to expand...

Actually you can go above 95 VE or below 45 VE, as long as the BLM average changes. I had one tune where I was trying to get a LOW RPM VE cell averaging at BLM 120 to an ideal BLM 128. I set the VE to 40, still had BLM 120, set VE to 35 still had BLM of 120. The point is, if you go below VE 45 does the BLM average change? The injectors might not respond to a VE below 45 or respond to a VE above 95. To fix the problem I was having, a different set of TBI injectors were installed. Another option to fix the problem I was having was to install an adjustable vacuum pressure regulator similar to the what the factory TPI system has. A lower fuel pressure at lower RPM's keeps the VE above 45, a higher fuel pressure at higher RPM's keeps the VE below 95.

Does that make sense?

dave w
 
dave w said:
Actually you can go above 95 VE or below 45 VE, as long as the BLM average changes. I had one tune where I was trying to get a LOW RPM VE cell averaging at BLM 120 to an ideal BLM 128. I set the VE to 40, still had BLM 120, set VE to 35 still had BLM of 120. The point is, if you go below VE 45 does the BLM average change? The injectors might not respond to a VE below 45 or respond to a VE above 95. To fix the problem I was having, a different set of TBI injectors were installed. Another option to fix the problem I was having was to install an adjustable vacuum pressure regulator similar to the what the factory TPI system has. A lower fuel pressure at lower RPM's keeps the VE above 45, a higher fuel pressure at higher RPM's keeps the VE below 95.

Does that make sense?

dave w
Click to expand...


Dave that does make complete sense.

If you keep lowering (or raising) the VE table but the BLMs no longer react to those changes then something else in the fuel system has to change. Thanks for an excellent explanation of when the VE table as become ineffective and other fuel delivery components need to change! I have not read this part of the puzzle in any other tuning HOW TO until now.

So then it makes sense that if the engine is running well and I do not have surging or jerking at low level rpm then there is no need to change the BPW at this time.

Thanks!! :woot:
 
You must log in or register to reply here.

Latest Posts

Top Bottom