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 > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Dec 2007
Location: Just a little north of 13669/Nation's capital
Posts: 867
Send a message via AIM to brighton911
Twin plug what if question

I'm helping my friend commission his 930 on Megasquirt. We're having the usual teething problems but that is expected. He is running a twin plug setup with COP's on each. My question is: what if one coil on a twin plug setup goes south? It would still run but now just on single plug on that cylinder. I'm thinking on a boosted engine putting out lots of HP, the loss of one coil/plug would not be good. What are your thoughts of loss of one plug?
And for those that like to worry, short of testing each coil every day, you really have no way of knowing both coils are working. That would bug me.
__________________
1986 Targa Guards Red
2012 Cayman S

Last edited by brighton911; 06-12-2018 at 03:49 PM..
Old 06-12-2018, 03:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
'76 911S 3.0's Avatar
 
Join Date: Aug 2004
Posts: 815
Garage
You would potentially see a lean spike when that cylinder's exhaust made it to the oxygen sensor, losing a plug would result in less complete combustion and would indicate as lean on a wideband. That would be about the only way I would see being able to identify a dropped plug on a cylinder.
__________________
-Jayson
1976 911S Signature Edition - 3.2SSt (JE 98mm 9.5:1 pistons, 964 Cams, ARP Rod Bolts, Big Port SC Heads, 3.2 Carrera Manifold, ID725's, B&B Headers, TS HyperGate45 Gen V, TS RacePort, BW S360, AEM Infinity 506, E85)
IG: Signature_911
Old 06-12-2018, 03:54 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Apr 2011
Location: behind the redwood curtain, (humboldt county) california
Posts: 639
Garage
wouldn't a dropped plug show rich??

If the mixture isn't completely burned, wouldn't the o2 sensor show rich??

Do the ECU's have the equivalent of a "check engine light" that would store a code??

When I worked in a dealership at the onset of computer tailoring of the last bit of mixture, (GM CCC), we would joke about putting black tape over the check engine light - but never did.

Seriously, doesn't the ecu have a way of indicating a problem, short of hooking up a laptop??

It would seem helpful to the driver if the O2 sensor went out of spec, alerting her to a likely problem.
chris
Old 06-12-2018, 05:47 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
'76 911S 3.0's Avatar
 
Join Date: Aug 2004
Posts: 815
Garage
Quote:
Originally Posted by chrismorse View Post
If the mixture isn't completely burned, wouldn't the o2 sensor show rich??

Do the ECU's have the equivalent of a "check engine light" that would store a code??

When I worked in a dealership at the onset of computer tailoring of the last bit of mixture, (GM CCC), we would joke about putting black tape over the check engine light - but never did.

Seriously, doesn't the ecu have a way of indicating a problem, short of hooking up a laptop??

It would seem helpful to the driver if the O2 sensor went out of spec, alerting her to a likely problem.
chris
Oxygen sensors measure oxygen content to determine air fuel mixture. An unburned mixture will have excess oxygen, thus reporting as lean. Some ECUs have fail-safes that can put the engine in limp mode (or completely shut the engine down depending on how you set it up) if the oxygen sensor reports too lean of a condition for a prescribed load. Others store codes, but really the best method is to look at the logged data to identify the problem. FWIW, the Infinity has the capability of triggering a MIL lamp if your ECU detects a fail safe condition.
__________________
-Jayson
1976 911S Signature Edition - 3.2SSt (JE 98mm 9.5:1 pistons, 964 Cams, ARP Rod Bolts, Big Port SC Heads, 3.2 Carrera Manifold, ID725's, B&B Headers, TS HyperGate45 Gen V, TS RacePort, BW S360, AEM Infinity 506, E85)
IG: Signature_911
Old 06-12-2018, 07:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Uncertifiable!!!
 
Uwon's Avatar
 
Join Date: Jan 2011
Location: Ontario, Canada
Posts: 1,293
Garage
Quote:
Originally Posted by brighton911 View Post
I'm helping my friend commission his 930 on Megasquirt. We're having the usual teething problems but that is expected. He is running a twin plug setup with COP's on each. My question is: what if one coil on a twin plug setup goes south? It would still run but now just on single plug on that cylinder. I'm thinking on a boosted engine putting out lots of HP, the loss of one coil/plug would not be good. What are your thoughts of loss of one plug?
And for those that like to worry, short of testing each coil every day, you really have no way of knowing both coils are working. That would bug me.
I have two switches on my dash that can individually turn off the coils to each set of six plugs (3 top on one side and 3bottom on other side). A quick flip of each switch (black ones) will tell you if one or more plugs is/are missing on that circuit.



Cheers,
Johan
__________________
Living well is life's best revenge- George Herbert (1593-1633)
2006 C2S, A4 Quattro, the RST hot rod-http://forums.pelicanparts.com/porsche-911-technical-forum/748639-evolution-carrera-rst.html

Last edited by Uwon; 06-13-2018 at 03:24 AM..
Old 06-13-2018, 03:20 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
wayner's Avatar
 
Join Date: Apr 2007
Location: I live on the road, I just stay here sometimes...
Posts: 6,260
I’ve read quite a bit about this on other threads when using twinned boxes

I haven’t looked but I think Henry smidt is one of the contributors if you want to search in his name or msd twin plug
__________________
Wayner
.
I can't wait to see what I do next!...
.
Old 06-13-2018, 03:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
Registered User
 
356RS's Avatar
 
Join Date: May 2003
Location: Bend, Oregon
Posts: 2,091
Garage
If you add a dual AFR display on your dash you can catch the problem before it gets too hot.

__________________
Mark Jung
Bend, OR
MFI Werks.com
Old 06-13-2018, 06:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Chain fence eating turbo
 
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,660
You’d lose power as now your timing is retarded
Old 06-13-2018, 06:51 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
kent olsen's Avatar
 
Join Date: Apr 2006
Location: McMinnville, Oregon
Posts: 1,193
Garage
I've got twin plugs and twin MSD's on my 81 3.0L in my 72 911. I put a switch, in the engine compartment, that turns one MSD off to check that they are both working. It works like doing the Mag Check on an airplane before takeoff.
__________________
Kent Olsen
72 911 SCT
upgraded 3.0L
McMinnville, Ore
RGRUPPE #104
Old 06-13-2018, 09:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
wayner's Avatar
 
Join Date: Apr 2007
Location: I live on the road, I just stay here sometimes...
Posts: 6,260
Here is the factory RSR solution for twin plug switches (looks like carried over from the 550 spyder of 1955)

__________________
Wayner
.
I can't wait to see what I do next!...
.
Old 06-13-2018, 09:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
wayner's Avatar
 
Join Date: Apr 2007
Location: I live on the road, I just stay here sometimes...
Posts: 6,260
Aha!

I found the thread...

MSD for Twin Plug
__________________
Wayner
.
I can't wait to see what I do next!...
.
Old 06-13-2018, 10:16 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
Join Date: Dec 2007
Location: Just a little north of 13669/Nation's capital
Posts: 867
Send a message via AIM to brighton911
Well there ya go, the "problem" has already been solved (of course). Yes, I like that idea of switches to cut out coil sets as a check. Thanks for everyone's inputs.
__________________
1986 Targa Guards Red
2012 Cayman S
Old 06-13-2018, 10:21 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
Functionista
 
manbridge 74's Avatar
 
Join Date: Jul 2011
Location: CO
Posts: 4,996
Interesting side fact. When a 964 comes in for service a guy is supposed to pull each coil quick disconnect off one by one to check each circuit’s ability to run the car...
__________________
Jeff
74 911, #3
I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible.
Old 06-13-2018, 10:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
wayner's Avatar
 
Join Date: Apr 2007
Location: I live on the road, I just stay here sometimes...
Posts: 6,260
The other option discussed in the other thread is to run two coils off just one box

( much discussion ensued)
__________________
Wayner
.
I can't wait to see what I do next!...
.
Old 06-13-2018, 10:29 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 06:28 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, 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.