P8 ECU Fuel Trim Screw Adjusting?

[Tom H]

To start with, I know how to adjust fuel trim on a 15M ECU with Guzzidiag to get 0, OR +/- numbers. I don't have an exhaust gas sniffer, so.....

The questions is:

With the screw on the P8. How do you know what is 0. As in not plus or minus?

I have read that only a certain amount of turning the screw does anything. How do you know that you are in the center/0? Gently turn it one way until it stops, then turn it the other way until it stops and find the center?? OR??????

Thank you!!
Tom

[lucky phil]

To start with, I know how to adjust fuel trim on a 15M ECU with Guzzidiag to get 0, OR +/- numbers. I don't have an exhaust gas sniffer, so.....

The questions is:

With the screw on the P8. How do you know what is 0. As in not plus or minus?

I have read that only a certain amount of turning the screw does anything. How do you know that you are in the center/0? Gently turn it one way until it stops, then turn it the other way until it stops and find the center?? OR??????

Thank you!!
Tom

Towards the end of the page.

http://bradthebikeboy.blogspot.com/2012/10/throttle-position-sensor-setting_21.html

Ciao

[Kiwi_Roy]

Its a weird Pot, from memory about (Wayne says 6 turns),  from end to end, It doesn't have a mechanical stop that I can recall.
I opened up the P8 and connected my meter on Ohms then set it half way for a start, rode then moved it 1/4 turn and rode again etc.
It's a long time since I had the EV with a P8 but it might backfire at certain settings. Turning it several turns one way you might hear a tiny click, then if you go the other way 3 turns you are near the middle, sorry if I had a P8 handy I could be more help
Never mind I see you have it sorted.
https://wildguzzi.com/forum/index.php?topic=110025.0

Must have document for anyone with a P8
https://dpguzzi.com/efiman.pdf  This gives a really good description of how the fuel injection system works.
There's not many schematics showing a P8, Carl's 98 EV shows a modern 15M
here's a couple
https://www.thisoldtractor.com/guzzi007/schematics/1996_California_1100i.gif
https://www.thisoldtractor.com/guzzi007/schematics/1996_Sport_1100i.gif  (i'm not so sure about this one, the pinouts are different)
Note one end of the ECU relay coil is wired to the ECU, inside the ECU is a small diode going to ground, I have fixed a couple of P8s for owners and found this diode burnt out.
The "Safety Diode" doesn't need to be in the ECU it could be re-wired outside just going to ground.
The Safety Diode prevents the ECU relay from closing if you accidentally put the battery in backwards, modern guzzles usually have one, sometimes it's incorporated in a special relay. e.g. https://www.thisoldtractor.com/guzzi007/schematics/2007_Norge.gif    Relay (29)
I think its a bit silly when they could have used just one relay type with a separate diode.

[Wayne Orwig]

Yes, odd number of turns, but I think it is 6. Been a while though. It SHOULD click when it reaches the end and not damage it. I wouldn't try to prove that though.
Clockwise is leaner I believe.
On a properly warmed up engine at idle, you will notice the idle change enough that it isn't a problem finding the proper trim setting.

[ampm7]

Go to Guzzitech and go to the loop/tonti forum and it will have an explanation. The adjustment is only for CO analysis from idle to 2000 rpm. Turning it clockwise leans mixture and turning counter-clockwise richens the mixture just as a carburetor air/fuel mixture screw would. It makes some difference as a TPS cleaning/adjustment does but it does not cure the problem of the bike hesitating/choking particularly at decel in first, second or third gear and partial throttle from 2500 to 3500 rpm. I have on order the upgrade EPROM M27C256B DIP28 -10F1 88801 1215L from China but it is taking over 2 months to receive. The reason I know this number is because I ordered this EPROM from Germany and it had been sitting somewhere for close to 20 years and the terminals were extremely brittle and some of them broke off when I inserted it. However, under the adhesive tag indicating it was for a '98 EV I got the number and found it on EBay. I ordered from two different suppliers 10 each. So, if they get here and it works I'll have some extras. Otherwise, I will get rid of the bike and go back to Harley. Sorry to say...

[Tom H]

OK, got it. Why it does not have stops is beyond me!

Thank you all!!!!
Tom

[ejs]

Go to Guzzitech and go to the loop/tonti forum and it will have an explanation. The adjustment is only for CO analysis from idle to 2000 rpm. Turning it clockwise leans mixture and turning counter-clockwise richens the mixture just as a carburetor air/fuel mixture screw would. It makes some difference as a TPS cleaning/adjustment does but it does not cure the problem of the bike hesitating/choking particularly at decel in first, second or third gear and partial throttle from 2500 to 3500 rpm. I have on order the upgrade EPROM M27C256B DIP28 -10F1 88801 1215L from China but it is taking over 2 months to receive. The reason I know this number is because I ordered this EPROM from Germany and it had been sitting somewhere for close to 20 years and the terminals were extremely brittle and some of them broke off when I inserted it. However, under the adhesive tag indicating it was for a '98 EV I got the number and found it on EBay. I ordered from two different suppliers 10 each. So, if they get here and it works I'll have some extras. Otherwise, I will get rid of the bike and go back to Harley. Sorry to say...

What ECU program Are you going to burn into those eproms ??

[guzzisteve]

I use a Colortune in plug hole so I can see the flame color change. A sniffer in tailpipe works also but slower. I've never had one jacked up, luckily. Usually within 1/4 turn.

[lucky phil]

What ECU program Are you going to burn into those eproms ??

Well I think if you buy an eeprom reader/burner which are fairly cheap you can use the Guzzidiag XDF to read the eeprom and get the .bin file and read it on tunerpro and  burn whatever maps or adjustments you like yourself onto a new chip with the chip burner.

Ciao

[Tom H]

Wayne, when I mess with a 15m trim. I look at what it's set at. Then try 0 and see how it idles. Then adjust for best idle after making sure the TPS and TB's are set and ballanced. Also, as with my EVT I had a ping at high speed. I enriched it to +15 IIRR and got rid of the ping.

Tom

[ejs]

Well I think if you buy an eeprom reader/burner which are fairly cheap you can use the Guzzidiag XDF to read the eeprom and get the .bin file and read it on tunerpro and  burn whatever maps or adjustments you like yourself onto a new chip with the chip burner.

Ciao

I was wondering what aftermarked program (binfile) he was going to burn. I have an aftermarked eprom on the EV myself. It is not eeprom inn the p8

[lucky phil]

I was wondering what aftermarked program (binfile) he was going to burn. I have an aftermarked eprom on the EV myself. It is not eeprom inn the p8

True, it's an eprom. But why not burn your own. Might be fun.

Ciao

[Wayne Orwig]

True, it's an eprom. But why not burn your own. Might be fun.

I used to do it often. In fact I still have a lot of blank 27C256 chips sitting around. I switched to OTP chip when the EEPROMS became impossible to find or too expensive.

[flower_king001]

what overall effect past idle does the trim adjustment have?  Performance, MPH?

[Kiwi_Roy]

what overall effect past idle does the trim adjustment have?  Performance, MPH?

From page 16 of the manual.
use the exhaust gas analyzer to check the CO which should be 2.5-3.5%. If this is not the case,
carefully remove plug “N” from the front of the computer and with a 4 mm wide screwdriver adjust the trimmer screw to achieve 2.5-3.5% CO. Turning the screw clockwise leans the idle mixture. This adjustment changes only the idle mixture.
Note: Do not force the adjusting screw beyond its limit stop (it can make a max. of about 3 turns)

BTW I don't know anyone with an exhaust gas analyzer, do you?

[lucky phil]

From page 16 of the manual.
use the exhaust gas analyzer to check the CO which should be 2.5-3.5%. If this is not the case,
carefully remove plug “N” from the front of the computer and with a 4 mm wide screwdriver adjust the trimmer screw to achieve 2.5-3.5% CO. Turning the screw clockwise leans the idle mixture. This adjustment changes only the idle mixture.
Note: Do not force the adjusting screw beyond its limit stop (it can make a max. of about 3 turns)

BTW I don't know anyone with an exhaust gas analyzer, do you?

I do, they are fairly inexpensive but home tuners can get away without them. More important for professionals as they set up the CO to what they know works for each model and it saves time. At the very least it gets them very close to what they need quickly.

Ciao

[Wayne Orwig]

what overall effect past idle does the trim adjustment have?  Performance, MPH?

I've heard it said, on the P8, the idle mixture affects it to a pretty high RPM, well above idle. I can't say it does or doesn't.
I just set them right for idle and it has worked well.

[guzzisteve]

I used one of these, price is not bad.

https://www.gunsonshop.com/contents/en-us/p245_G4125_Gunson_Digital_Exhaust_Gas_and_CO_Tester.html

[LowRyter]

lean it out until you get a backfire.  then fatten it. 

it's a simple way to adjust when riding and encountering elevation changes. 

Perhaps I'm doing it wrong?

[JoeB]

I've heard it said, on the P8, the idle mixture affects it to a pretty high RPM, well above idle. I can't say it does or doesn't.
I just set them right for idle and it has worked well.

Dusted off my copy of 90's Guzziology. They state the pot trim for the P8 affects up to 2000rpm, and the bypass screws 2000-4000rpm.
Like you I've set them at idle.
Computer trim pot adjustments are said not to be immediate, but take a bit to stabilize.
Have used CO meter but seemed to have to tweak it a bit anyway after.
Anymore like LowRyter I just go for a decent ride and adjust as necessary.
 

[Tom H]

FK, I know with a 15m ECU it will help a bit at around 3500. My EVT had a slight ping on the freeway when passing at 65-70mph. Adjusted the trim up about 10 from where it was. Idled better and the ping went away.

Tom

[Tusayan]

I have on order the upgrade EPROM M27C256B DIP28 -10F1 88801 1215L from China but it is taking over 2 months to receive. The reason I know this number is because I ordered this EPROM from Germany and it had been sitting somewhere for close to 20 years and the terminals were extremely brittle and some of them broke off when I inserted it. However, under the adhesive tag indicating it was for a '98 EV I got the number and found it on EBay. I ordered from two different suppliers 10 each. So, if they get here and it works I'll have some extras. Otherwise, I will get rid of the bike and go back to Harley. Sorry to say...

The model number of the eprom itself has no bearing on the map subsequently burned onto it.  Blank 27C256-10 EPROMs or non-eraseable equivalent can be ordered new from e.g. Mouser for delivery in a couple of days, but like the ones you’ve ordered they won’t be storing any data, or work until in your ECU until they are loaded with the appropriate file.

The best way to set the idle trim potentiometer is by experiment.  Start lean and richen a little bit at a time until (hopefully, and assuming maps and all else is in order) the misfires disappear.  The effect at small throttle openings is up to at least 3000 rpm and is immediate on a bike with no O2 sensor.

Altitude compensation programming was inadequate on some stock Guzzi chips, but otherwise given the ambient or air box pressure sensor, there is no need to adjust for altitude.