Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 Engine Rebuilding Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
LM2 AFR readings

Here is a recording of the AFRs on my '82 SC with frequency valve but no Lambda sensor feeding into the mini-brain. Taken with an LM2. Unfortunately I can't get the RPM readings to work right (pretending that the car has 8 or 12 cylinders seems to be better than for six, but still well off), and those would be helpful. This is from the full track at Miller. I think the big spikes are for corners where I brake and downshift. I used about 0.5 second smoothing to make the graph less jittery. Sure goes way lean off throttle. WOT in the low 13s and high 12s mostly. Car ran fairly well, tailpipes wiped off as just a very light gray.

So is this the norm for a well functioning CIS on a race track? One expert says you want to run 13.2 based on his dyno tuning of Euro SCs (which don't have FVs and such).

Old 09-21-2016, 08:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Puny Bird
 
Mark Henry's Avatar
 
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,055
Of course you have lean peaks...you took your foot off the go pedal.

That's perfectly normal, no load so the lean peaks are nothing more than air (thus lean reading) getting sucked past the throttle plates. The smaller lean peaks you have are also deceleration, maybe your foot isn't fully off the pedal. Again no load so all is good.

The numbers you want to be concerned with are the ones under load, I like 12.5 on hard acceleration and just a hair rich of stoich AFR at cruise.
If 13.2 is good for CIS I have no problem with that.

Your numbers look pretty good.

BTW just an FYI you don't see as big a lean spike with carbs, because even under deceleration you are still sucking fuel out of the carbs, whereas most FI systems shuts the injectors down. My SDS EFI is programmed to cut the fuel completely (stops backfiring) so my decel lean AFR spike is off the charts.
__________________
'74 Porsche 914, 3.0/6
'67 Bug, 2600cc T4
'67 Bus, 2.0 T1
Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend.

Last edited by Mark Henry; 09-22-2016 at 08:28 AM..
Old 09-22-2016, 08:18 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
Mark - any idea where those rich reverse peaks come from?

What surprised me about this trace is how much variation at WOT there is. I haven't had the time or patience to figure out how to correlate this data with my Racepak GPS speed and RPM data. With that I can figure out where on the track I am, which corners the decal spikes are for, etc.

But Miller has about four longish straights, or rather WOT segments: The long start/finish straight with gears 3,4, and 5; after turn 3 with 3d up to 4th, the long stretch leading up to turn 12 or so (3d to 4th), and from Tooele corner to Clubhouse (3d to 4th). I'd expect to see the upshift as a spike, but not all that jiggling around with the trace.

Now if I can build something which will modify the tach signal so the LM2 will recognize it as a 6 cylinder car, I can learn more with less effort. The tach reads it fine, the Racepak reads it fine, why doesn't the Inovate read it suitably?
Old 09-22-2016, 09:29 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Puny Bird
 
Mark Henry's Avatar
 
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,055
Not sure on the rich peaks, my bet is they happen at a certain small RPM range at or just off WOT, but at the same time I'd say they are nothing to overly worry about.
Rich, but the power won't bog out till close to 10:1 AFR. Rich is better than lean under load.

Can't help you on the LM2 issue, I use a WMS (Western Motorsports) meter.
__________________
'74 Porsche 914, 3.0/6
'67 Bug, 2600cc T4
'67 Bus, 2.0 T1
Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend.
Old 09-23-2016, 08:36 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
Anyone out there have an LM2? A problem I have with it is that it will quit at some ill defined number of minutes, maybe 7 or less. The display will show the same number, as will the recording - a straight line. Not to be believed. Inovate hasn't returned my call.

If I turn it off, and back on, it will work for a while, then lock again. I wonder if I'm overheating the sensor? Perhaps I need to weld a nut with the right thread over the bung to get the sensor farther from the exhaust flow, I think. The sensor is new as of about three events ago.
Old 09-23-2016, 12:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Puny Bird
 
Mark Henry's Avatar
 
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,055
Are you running leaded race or AV gas?
I know lead kills these O2 sensors pretty quick. But I think it should last a season.
__________________
'74 Porsche 914, 3.0/6
'67 Bug, 2600cc T4
'67 Bus, 2.0 T1
Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend.
Old 09-23-2016, 02:03 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
Pump premium, which in these parts is 91 octane (RON+MON), with some percentage of alcohol (weekend after tomorrow I'll be at Hallett in Oklahoma, and Oklahoma gas stations proudly announce that there is no alcohol in their gasoline.

No lead - this is a stock 3.0 liter motor.
Old 09-23-2016, 05:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Gordo2's Avatar
 
Join Date: Sep 2002
Location: Stafford, VA
Posts: 1,714
Garage
Innovate LM2

Quote:
Originally Posted by Walt Fricke View Post
Anyone out there have an LM2? A problem I have with it is that it will quit at some ill defined number of minutes, maybe 7 or less.

My LM2 flakes on me sometimes as well - normally straightens out with a free air recalibration.

On the RPM readings - I am only able to get my LM2 to provide & record accurate RPM readings by disconnecting the vehicle tach. If I have the LM2 and tach both taking input from the tach wire (black/purple for my '83) - my RPM readings are all over the place.
I've tried all sorts of things to get it to work, but haven't tried their tach adapter (clamps onto a plug wire, providing an independent RPM signal).

Sorry can't really say much regarding your AFR readings - I've only run my LM2 with my PMO carbs. Meanwhile, I normally use max smoothing to review recordings - I think it helps identify AFR trends (what conditions cause my engine to go too rich or lean) without becoming sidetracked with the freakish spikes.

Good luck, Gordo
__________________
Don Gordon "Gordo"
'83 911SC Targa
'87 FJ-60 TLC
Old 09-23-2016, 06:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
Walt Fricke's Avatar
 
Join Date: May 2004
Location: Boulder, Colorado
Posts: 5,082
I also have a Racepak connected to my tach wire. Registers the tach signal fine. Interestingly, if I turn the Racepak off, the tach quits - goes to zero. EE friends say this seems reasonable, depending on the unpowered state of a transistor or IC in the Racepak, which may go to ground without the device being powered.

In my case, I suspect the Inovate is reading stray signals which the Racepak as well as the Bosch tach filter out. The Inovate is reading something. Then again, there are small and occasional larger spikes which show up on the bottom of the display from channels which have nothing attached to them! Given what a wonderful and large capacitor the battery is (even my garden tractor small one), I have trouble seeing some other component of the car creating voltage spikes.

On the other hand, I just replaced my alternator. The shop showed me the failed parts of the old one - the stator was bad, and it looked like a diode or two was bad. I can always hope I'll not get good tach signals.

I don't like the idea of getting a signal from a plug wire. The AIM data system has this as an alternative, but it doesn't seem to work all that well. Friends who investigated with an oscilloscope the signals from an inductive clamp said they were inconsistent. Somehow inductive clamping works fine for setting spark advance with a strobe, but that may be because missing the odd signal doesn't affect the strobe effect?

I think I am going to have to find a suitable circuit and build something which (maybe use an opto isolator)outputs a nice 5v or so square wave. If the Inovate people were more communicative you'd think they would have figured this out - something like that should be less than a buck in parts in bulk purchase. Power from the car's 12V, stepped down to 5V.

If I fix this I'll post. Won't be soon.
Old 09-23-2016, 08:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 05:17 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.