Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

2 Pages V  1 2 >  
 Reply to this topicStart new topic
> Manifold Pressure Sensor MPS Adjustment, I have read PBanders thread several times
thompson-mfr
post Jun 21 2012, 01:05 PM
Post #1


Thompson, Ryan
**

Group: Members
Posts: 198
Joined: 30-September 08
From: Silverton, OR
Member No.: 9,598
Region Association: Pacific Northwest
Hello all,

I need to adjust my MPS as it is a TYPE4 unit. I have adjusted it before "Guess and Check" method but decided to do it the correct way. Last time I used the "Guess and Check" method I got lucky and it ran beautifully.

Just changed and adjusted points/dwell/timing. Valve job done 1000 miles ago.
74 2.0 original FI

I have read PBanders thread a bunch of times.

I have a multimeter that will do HFE tests.

I looked at the multimeter he suggests and I don't see any difference between mine.

I need to have it explained to me "like a small child" how to hook up the multimeter to the MPS. I see the HFE input terminal on my mulitmeter. It has EBCE inputs both PNP and NPN.

I know I need to hook to 8 and 10 on my MPS.

I have tested the unit to make sure it is within spec. 350 ohms between 7 and 15 and 90 ohms between 8 and 10. Holds vacuum and no continuity between case and connections.

Any and all help will be greatly appreciated.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
brant
post Jun 21 2012, 01:09 PM
Post #2


914 Wizard
**********

Group: Members
Posts: 11,623
Joined: 30-December 02
From: Colorado
Member No.: 47
Region Association: Rocky Mountains
I don't believe you can adjust the MPS with a multi-meter
you can test the continuity that you already have done


I don't know how to use a wave-tek
hopefully someone with real experience will chime in


The other way to adjust one is to use a wide band o2 sensor and adjust under load either on a dyno or in real time on the road.
(that is how I have done them in the past)

brant
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
thompson-mfr
post Jun 21 2012, 01:15 PM
Post #3


Thompson, Ryan
**

Group: Members
Posts: 198
Joined: 30-September 08
From: Silverton, OR
Member No.: 9,598
Region Association: Pacific Northwest
Forgot to mention:

The full load stop screw has been drilled out (PO) just enough to access the inner screw without removing full load stop screw. Kida different. Can't adjust the outer screw this way obviously.

I will try to post a pic if this is unclear to folks.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Bartlett 914
post Jun 21 2012, 01:29 PM
Post #4


Advanced Member
****

Group: Members
Posts: 2,215
Joined: 30-August 05
From: South Elgin IL
Member No.: 4,707
Region Association: Upper MidWest
You need an inductance meter. This is different from a multi meter.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
JeffBowlsby
post Jun 21 2012, 02:25 PM
Post #5


914 Wiring Harnesses
*****

Group: Members
Posts: 8,503
Joined: 7-January 03
From: San Ramon CA
Member No.: 104
Region Association: None
Its important to remember that Brad A developed his tables based on the Wavetek LCR55 and because of the sensitivities of the values he cautions about using any other meter. Other inductance meters may give other values...perhaps other tables specific to the other meter would need to be developed.

Also, the Brads calibration table values need to be adjusted for elevations above sea level, per his notes.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
benalishhero
post Jun 21 2012, 05:55 PM
Post #6


Member
**

Group: Members
Posts: 313
Joined: 28-November 07
From: Portland, Maine
Member No.: 8,384
Region Association: North East States
The wavetek LCR55 has been discontinued. At least I could not source a new one. The Amprobe LCR55A is available new. I too have enriched mine by reading the plugs, but want to set it correctly. Going for it this weekend. I will post my results.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
brant
post Jun 21 2012, 06:25 PM
Post #7


914 Wizard
**********

Group: Members
Posts: 11,623
Joined: 30-December 02
From: Colorado
Member No.: 47
Region Association: Rocky Mountains
regarding a "free hand" adjustment the MPS is more sensative than my human eye can see....

I spent a day doing back to back runs with the 2 adjustment screws... a tiny change made a big difference. There was no way my seat of the pants could tell any difference. Only the wide band could tell the difference. I don't believe you can get close without the right tools...
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
benalishhero
post Jun 21 2012, 06:30 PM
Post #8


Member
**

Group: Members
Posts: 313
Joined: 28-November 07
From: Portland, Maine
Member No.: 8,384
Region Association: North East States
QUOTE(brant @ Jun 21 2012, 08:25 PM) *

regarding a "free hand" adjustment the MPS is more sensative than my human eye can see....

I spent a day doing back to back runs with the 2 adjustment screws... a tiny change made a big difference. There was no way my seat of the pants could tell any difference. Only the wide band could tell the difference. I don't believe you can get close without the right tools...


Well, FWIW my car hasn't run this well since I've owned it.(11 years) But ya, I have the correct tools, and want to calibrate it correctly.......
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
JeffBowlsby
post Jun 21 2012, 06:37 PM
Post #9


914 Wiring Harnesses
*****

Group: Members
Posts: 8,503
Joined: 7-January 03
From: San Ramon CA
Member No.: 104
Region Association: None
QUOTE(benalishhero @ Jun 21 2012, 04:55 PM) *

The wavetek LCR55 has been discontinued. At least I could not source a new one. The Amprobe LCR55A is available new. I too have enriched mine by reading the plugs, but want to set it correctly. Going for it this weekend. I will post my results.


Yup, I know...

I have a Wavetek LCR-55. At some point maybe some side by side comparisons might need to happen (a shootout) to see how different meters are calibrated...maybe the good meters are precise enough for any differnces to be negligible.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jun 21 2012, 08:57 PM
Post #10


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
Jeff I just bought the Amprobe.
Maybe I can make arrangements to send my meter to you so you can compare the readings on both.

With Geoff's guidance I just put an 037 top on an 41 base to create a working unit. Took longer to figure out how to get the right clips on the terminals. Than it did to do the adjustments.
Double checked my work 3 times. Dead on.
I just went with Brad's numbers. I'm here in Portland, about 300 feet.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
JeffBowlsby
post Jun 21 2012, 09:34 PM
Post #11


914 Wiring Harnesses
*****

Group: Members
Posts: 8,503
Joined: 7-January 03
From: San Ramon CA
Member No.: 104
Region Association: None
Sure, just email me to coordinate. I have a few MPS on hand I could characterize and compare the meters.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 9 2012, 09:49 PM
Post #12


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
Update :

I bought both an Amprobe LCR and an Innovate LM-1.
So now I'm in this up to my neck.

The LCR made adjusting the MPS very simple.
All adjustments dead on with Brad's MPS chart.
But the LM-1 still shows me very lean at idle.
I'm like 25.5%
Probably too lean at partial throttle too.
14 & 15%.

So I'm thinking I'll do the 2500 rpm test and dial the AFR to 12.7 with the MPS inner screw. Then back out the full throttle stop the same amount of turns?
Am I on the right track? Suggestions?

The full throttle stop screw has an adjustment hole in it. Does that have an operational effect?

Sorry thompson-mfr for kind of hijacking the thread.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 9 2012, 10:41 PM
Post #13


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
I need to add one thing.
This is a 73.
But it doesn't have a ballast resistor. Never has had one.
Might this be part of the problem?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914_teener
post Jul 9 2012, 10:57 PM
Post #14


914 Guru
*****

Group: Members
Posts: 5,197
Joined: 31-August 08
From: So. Cal
Member No.: 9,489
Region Association: Southern California
QUOTE(cary @ Jul 9 2012, 08:49 PM) *

Update :

I bought both an Amprobe LCR and an Innovate LM-1.
So now I'm in this up to my neck.

The LCR made adjusting the MPS very simple.
All adjustments dead on with Brad's MPS chart.
But the LM-1 still shows me very lean at idle.
I'm like 25.5%
Probably too lean at partial throttle too.
14 & 15%.

So I'm thinking I'll do the 2500 rpm test and dial the AFR to 12.7 with the MPS inner screw. Then back out the full throttle stop the same amount of turns?
Am I on the right track? Suggestions?

The full throttle stop screw has an adjustment hole in it. Does that have an operational effect?

Sorry thompson-mfr for kind of hijacking the thread.




(IMG:style_emoticons/default/popcorn[1].gif)

You are one more step down the rabbit hole than I........I couldn't find a new LM-1 though?

also and apology for the hijack (IMG:style_emoticons/default/unsure.gif)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Bleyseng
post Jul 10 2012, 04:04 AM
Post #15


Aircooled Baby!
**********

Group: Members
Posts: 13,034
Joined: 27-December 02
From: Seattle, Washington (for now)
Member No.: 24
Region Association: Pacific Northwest
QUOTE(cary @ Jul 10 2012, 01:41 AM) *

I need to add one thing.
This is a 73.
But it doesn't have a ballast resistor. Never has had one.
Might this be part of the problem?



Yes!
Put one on before you go any further with adjustments.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 10 2012, 07:21 AM
Post #16


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
Dang it......... that's what I thought you were going to say. I was hoping to tweak the MPS and drive off into the sunset.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 10 2012, 10:38 PM
Post #17


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
$1.19 for a five pack at Radio Shack.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 13 2012, 09:13 PM
Post #18


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
Well I finally got the ballast resistor installed.
Looks like it dropped the AFR about 2%.
Drove a little smoother.

So I decided to adjust the inner screw.
I started with an AFR at idle of about 23%.
At 2500 RPM's its about 17.5%.

I decided to adjust the 2500 rpm first.
Boy, it doesn't take much.
I might have moved it 75 degrees CCW total.
Attached Image
Here's the 2500 reading

That left me at idle with a 15.4%
Attached Image

Set up for a road test.
Attached Image

It was really cool to hear the engine start to smooth out as I lowered the AFR past about 17%. Now that AFR is close TO being correct. Everything works. The idle speed and mixture both work like they're supposed to.

It was also really amazing watching the AFR as I adjusted the idle speed.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Bleyseng
post Jul 14 2012, 04:03 AM
Post #19


Aircooled Baby!
**********

Group: Members
Posts: 13,034
Joined: 27-December 02
From: Seattle, Washington (for now)
Member No.: 24
Region Association: Pacific Northwest
(IMG:style_emoticons/default/piratenanner.gif)



Now drive it like you stole it!
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
cary
post Jul 14 2012, 07:52 AM
Post #20


Advanced Member
****

Group: Members
Posts: 3,900
Joined: 26-January 04
From: Sherwood Oregon
Member No.: 1,608
Region Association: Pacific Northwest
That is the plan ......................
Thanks for the help.

Wash and a wax and she's good to go. I'll put 500 miles on her and do a final adjustment.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
« Next Oldest · 914World Garage · Next Newest »
 

2 Pages V  1 2 >
Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 

Display Mode: Standard · Switch to: Linear+ · Switch to: Outline

Track this topic · Email this topic · Print this topic · Subscribe to this forum

- Lo-Fi Version Time is now: 13th May 2024 - 11:12 PM
Invision Power Board v9.1.4 © 2024  IPS, Inc.
All rights reserved 914World.com © since 2002
914World.com is the fastest growing online 914 community!
We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ...