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

cuervo

cuervo

Runn'n down a dream!
 Premium
Joined
Jan 2, 2004
Posts
3,800
Reaction score
992
Location
Sweet Home Alabama!
Well I'm finally getting back to this task. :waytogo:

What I've got.

GMPP 383 - 4l804
620 cfm custom TBI
454 80 injectors
60 psi pump 255lph
18 psi at the (now using an adjustable and stock spring set to 15 psi)
A Harris TBI custom chip (now using a home brew custom chip)


When I last left off, it was well noted that it was rich in just about every area but I can't seem to find the log now. That was probably 16 months ago.

So now, I finally got a couple of melcals solder up with new chips and I'm working with the $85.

I get some logs down tomorrow and go from there. I can see this section has pick up a bit since I left off.

Thanks to Dave and Mark for doing most of the leg work.
 
Last edited:
Last night I tried to get a log from datamaster, of course now it's not connecting using the same laptop I used the first time.
 
16 month old gas?

Looked at your motor cam specs and that should be an easy tune. Lot of gas from the injectors you got. May want to start by turning down BPW to get BLM closer to start. I did a motor like that once and used an ajustable regulater turned up to 16 PSI on stock injectors. You probably still have more fuel if I did the math...

Comm ports change all the time on laptops. Plug the USB into another port, then reopen datamaster. If not plug in cable to USB port and restart computer, then reopen datamaster... look at control panel, devices and open it to see what comm port it says it's using, make sure datamaster is on same comm port.

I'm looking at buying a used Panisonic Tough Book laptop. Not only are they drop proof and waterproof and have batterey life of double normal laptops! They still have serial port and USB ports. Serial port never changes comm port. This would make it way easier to hook up my wide band O2 on serial, then usb for TP. I have a hard time getting 2 usb hooked up. One to TP is always one of 2 USB ports on my laptop, easy. But if I hook up my USB wireless mouse, or plug in my USB printer when I go in the house? They work fine! But when I go out to tuning they all change? Computers are only as good as the human that builds them. Dumb...:dunno:

Thanks for the thanks! But I am just continuing what a lot of other pioneers did with tuning. Without them we would all be screwed!
 
eagle mark said:
16 month old gas?

Looked at your motor cam specs and that should be an easy tune. Lot of gas from the injectors you got. May want to start by turning down BPW to get BLM closer to start. I did a motor like that once and used an ajustable regulater turned up to 16 PSI on stock injectors. You probably still have more fuel if I did the math...

Comm ports change all the time on laptops. Plug the USB into another port, then reopen datamaster. If not plug in cable to USB port and restart computer, then reopen datamaster... look at control panel, devices and open it to see what comm port it says it's using, make sure datamaster is on same comm port.

I'm looking at buying a used Panisonic Tough Book laptop. Not only are they drop proof and waterproof and have batterey life of double normal laptops! They still have serial port and USB ports. Serial port never changes comm port. This would make it way easier to hook up my wide band O2 on serial, then usb for TP. I have a hard time getting 2 usb hooked up. One to TP is always one of 2 USB ports on my laptop, easy. But if I hook up my USB wireless mouse, or plug in my USB printer when I go in the house? They work fine! But when I go out to tuning they all change? Computers are only as good as the human that builds them. Dumb...:dunno:

Thanks for the thanks! But I am just continuing what a lot of other pioneers did with tuning. Without them we would all be screwed!
Click to expand...

No, I was still driving it with the harris chip in it.

I'm putting new headers on it and changing out the power steering pump today. I hope to get it done and get some logs.
 
Well, my logging issue was the buad rate. I had to set it to 4800.


Well, I finally got a new log with the new long tube headers on but pretty much the same result. Rich rich and more rich.

lerm.jpg


stem.jpg


I'll attach the log as well. I still have a lot of reading to do.

I was watching the o2 in closed loop and it keeps dropping really low in voltage. Is that normal?

http://www.mikesell.net/images/383v2.zip
 
One of these days I will get datamaster... so I can't read your log... but from what I see it's rich!

What does your second VE table look like?
 
eagle mark said:
One of these days I will get datamaster... so I can't read your log... but from what I see it's rich!

What does your second VE table look like?
Click to expand...

Datamaster is a free download. It just lets you log 20 times then wont log until you register but you can still read logs.


http://www.ttspowersystems.com/DataMaster_downloads2.html

DM35x85 is the version for my truck.

My xdf file, $85, does not have an adder or secondary VE table.
 
Last edited:
A lot of BLM are at 105 so I did a large change to the ones in red. The forumla called for -10 but I didn't want to go that far and just did -3.

If I can't get the BLMs to 128 and stay in the 45-90 range what is my next step? Lower the fuel pressure?
 
Your running higher pressure than stock with BB Injectors already? :eek1:

I never go below 12-13 PSI on TBI injectors. It looked overall rich so drop BPW by 5 and make sure WOT high RPM does not go leaner. It looks good there now.

This is from looking at your data pictures
 
I tried taking more out of the VE table but it had little result. It's still very rich in all areas.

Are BPW and base pulse width constant the same thing? Right now it's at 123.

Yeah, I'm starting to think this motor doesn't really need all that pressure and injector flow.

I think it's already going lean on WOT. The motor is supposed to be good upto 5000 and peak HP @4500 but starts to fall on it's face at 4000 pretty bad.

edit
The spring is supposed to be either a 16 or 18, I do not recall. I might have to put a different gauge on there and double check the pressure.
 
Find your pressure first!

Yes the Base Pulse Width Constant is like a course adjustment to the VE table. So it may get you right where your rich and leave you lean top end...
 
eagle mark said:
Find your pressure first!

Yes the Base Pulse Width Constant is like a course adjustment to the VE table. So it may get you right where your rich and leave you lean top end...
Click to expand...


I took 5 out of the BPW and drove over to get a schrader valve so I could hook up a second pressure gauge just to be sure.

The numbers already look better. A lot of them went from 105 to between 113 and 121.

Is the only way to increase fuel at WOT through pressure and BPW?
 
Well, I know for sure I have 18 PSI.

Should I take a couple more points out of the PBW or start over on the VEs. I did go back to the original VEs before changing the BPW to 118.

fuel.jpg
 
There are a lot of other factors that go into changing fuel pressure and BPW, some you can get away with a little.

Your origanal post said 13.5 PSI and a harris chip. I would go back to 13.5 maybe 15 and that chip and start datalogging again!
 
eagle mark said:
There are a lot of other factors that go into changing fuel pressure and BPW, some you can get away with a little.

Your origanal post said 13.5 PSI and a harris chip. I would go back to 13.5 maybe 15 and that chip and start datalogging again!
Click to expand...


All of the logs I posted up are from the current 18 psi and that harris chip that is/was extremely rich. I just thought it was 13 psi, it had been a year since I looked at it.

The only way for me to change the 18 is to get a new spring.
 
That's as low as the spring will go even with adjustable regulator? If you have an adjustable regulator you could put a stock spring back in, I don't know how far a stock spring will go but I know for sure it will hit 16 PSI, maybe more...

There's always more than one way to skin a cat! I like K.I.S.S.!

Once you start changing fuel pressure there are other things to consider like Injector Bias measured in milliseconds like 0.396 and then AE and PE and probably things we don't even know of? It's like the ECM can adjust itself right? Well how come we have to tune it then? Because it can only go so far, it was only designed for a certain range!

If you stay close to 13 then your in the KISS. I just used the injector sizing excel spread sheet for a 383 with 90 pound injectors at 18 PSI and that would support 424 HP with a BPW of 88.1... pretty big change in BPW and I'm not sure of all the consequences... plus your motor is probably closer to 350 HP.

Now at 13 PSI on your 90 pound injectors will support 360 HP at a BPW of 103.7 so your a lot closer to stock BPW and have plenty of room to go up to? What was yours? 126? I've found the spread sheet to be a little on the low side for BPW... so at 13 PSI you may be spot on.

Plus of all the mail order chips available you have one from a guy who has done this a long time and has a great reputation. So if you gave him all the correct specs to begin with then your chip is probably real close and only God could tune it better by mail!

Just my .02 cents...

Link to injector sizing spreadsheet.
http://eagle-mark.com/pictures/displayimage.php?pid=1188
 
Last edited:
eagle mark said:
That's as low as the spring will go even with adjustable regulator? If you have an adjustable regulator you could put a stock spring back in, I don't know how far a stock spring will go but I know for sure it will hit 16 PSI, maybe more...

There's always more than one way to skin a cat! I like K.I.S.S.!

Once you start changing fuel pressure there are other things to consider like Injector Bias measured in milliseconds like 0.396 and then AE and PE and probably things we don't even know of? It's like the ECM can adjust itself right? Well how come we have to tune it then? Because it can only go so far, it was only designed for a certain range!

If you stay close to 13 then your in the KISS. I just used the injector sizing excel spread sheet for a 383 with 90 pound injectors at 18 PSI and that would support 424 HP with a BPW of 88.1... pretty big change in BPW and I'm not sure of all the consequences... plus your motor is probably closer to 350 HP.

Now at 13 PSI on your 90 pound injectors will support 360 HP at a BPW of 103.7 so your a lot closer to stock BPW and have plenty of room to go up to? What was yours? 126? I've found the spread sheet to be a little on the low side for BPW... so at 13 PSI you may be spot on.

Plus of all the mail order chips available you have one from a guy who has done this a long time and has a great reputation. So if you gave him all the correct specs to begin with then your chip is probably real close and only God could tune it better by mail!

Just my .02 cents...

Link to injector sizing spreadsheet.
http://eagle-mark.com/pictures/displayimage.php?pid=1188
Click to expand...


Well, I sent him my motor info and he suggested the fuel pump, spring and chip. After two trys it was still extremely rich. So far rich that I had to ajust the BPW to even get to the numbers off of the 105. At this point I'm pretty close. If I have to get the lower spring I might still have my old stock TBI, it might have a lower spring that would work.

I wish I would have known the GMPP 383 didn't need that much fuel. I would have saved myself about a grand.

So now, I've spent all the money on the autoprom, chips, solder flash roms on mecals just so I could fix what someone else could not. I was told that harris chips were good, the best, and now some guy with nothing more then the interenet and some friends I'll make it right.
 
Well if you have been getting it closer than just keep going! :waytogo:

The scenario I posted was a good way to start. Since your WOT looks good it may be better for you to just work on VEs that are off. You could try to drop BPW by 10 and check WOT, then another 10 and check WOT. But don't let WOT go lean. If it does put BPW back and work on VE for rich cells.

Also if it has been running this rich this long you may want a fresh O2 sensor! Pull it out and if it is sooted up? Replace it and check data! Then start tune again. HTH!
 
You must log in or register to reply here.

Latest Posts

Top Bottom