What's your A/F on Overrun?, 'Nother D-Jet A/F Question |
|
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. |
|
What's your A/F on Overrun?, 'Nother D-Jet A/F Question |
BeatNavy |
Mar 12 2017, 12:28 PM
Post
#1
|
Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
For those with D-Jet, what are you typically seeing for A/F ratio on a medium to hard overrun? Based on what I've read here mine seems too rich - like in 10's and 11's. Once the RPM's drop closer to idle it bounces back up to normal idle A/F ratios. Does A/F on overrun even matter?
|
BeatNavy |
Mar 12 2017, 06:13 PM
Post
#2
|
Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
Not particularly. That's sort of been the root cause of my continuous futzing with D-Jet recently. It runs well, but mileage is not great best I can tell. With 2056 I've never got better than 20 mpg driving to/from work -- 20 minutes of "parkway" driving which is 95% of what I do. I maybe got closer to 23 to 25 last year going to and from Hershey on the highway. Maybe that's all I should expect (IMG:style_emoticons/default/confused24.gif)
I've swapped out different combos of CHT and with and without spacer recently, and I got leaner, and hotter, after removing the spacer, but interestingly the mileage didn't seem to get better. The spacer I had on the CHT was long - like 23 mm -- and seemed to act more like a ballast resistor and enriched mixture even after warm-up. Today I cut the spacer down some to try to allow good warm-up while still allowing the CHT to get to "operating temp" that's not too rich or lean. I may be chasing a couple of minor issues...but I wanted to see what a "normal" overrun A/F would be as this hasn't really changed with all the screwing around I've done. |
mgphoto |
Mar 12 2017, 11:55 PM
Post
#3
|
"If there is a mistake it will find me" Group: Members Posts: 1,339 Joined: 1-April 09 From: Los Angeles, CA Member No.: 10,225 Region Association: Southern California |
Not particularly. That's sort of been the root cause of my continuous futzing with D-Jet recently. It runs well, but mileage is not great best I can tell. With 2056 I've never got better than 20 mpg driving to/from work -- 20 minutes of "parkway" driving which is 95% of what I do. I maybe got closer to 23 to 25 last year going to and from Hershey on the highway. Maybe that's all I should expect (IMG:style_emoticons/default/confused24.gif) I've swapped out different combos of CHT and with and without spacer recently, and I got leaner, and hotter, after removing the spacer, but interestingly the mileage didn't seem to get better. The spacer I had on the CHT was long - like 23 mm -- and seemed to act more like a ballast resistor and enriched mixture even after warm-up. Today I cut the spacer down some to try to allow good warm-up while still allowing the CHT to get to "operating temp" that's not too rich or lean. I may be chasing a couple of minor issues...but I wanted to see what a "normal" overrun A/F would be as this hasn't really changed with all the screwing around I've done. The issue is not your temp sensor, it's the mps, it must be adjusted correctly. Temp sensor is measured by the ecu and compared to a set resistance within the ecu. Spacers just try to compensate for the cold head, hot engine problem. Opening the throttle with get her started. You are just going to chase your tail following the resistor - fuel pressure route. If you can adjust the idle with the "pot" on the ecu your tps is adjusted correctly, 1/3 of the battle won. The best way to adjust the mps is an Air/Fuel mixture meter and the Racer Chris mps kit. A correctly adjusted mps with your engine combo, 24 mpg is not out of reach. Even with a certain amount of aggressive driving style! Mike |
BeatNavy |
Mar 13 2017, 03:41 AM
Post
#4
|
Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
The issue is not your temp sensor, it's the mps, it must be adjusted correctly. Temp sensor is measured by the ecu and compared to a set resistance within the ecu. Spacers just try to compensate for the cold head, hot engine problem. Opening the throttle with get her started. You are just going to chase your tail following the resistor - fuel pressure route. If you can adjust the idle with the "pot" on the ecu your tps is adjusted correctly, 1/3 of the battle won. The best way to adjust the mps is an Air/Fuel mixture meter and the Racer Chris mps kit. A correctly adjusted mps with your engine combo, 24 mpg is not out of reach. Even with a certain amount of aggressive driving style! Mike I've also spent a lot of time messing with my MPS (I have two of the 043's to play with). Both have been repaired with Chris' kits. I have spent hours getting the numbers to match Brad Anders' numbers as close as possible to include graphing them out on Excel to get the slope / range as he did. Funny, I could never get the 0 psi number (WOT) to even get close to his. Full load stop wouldn't adjust that far out. But as I've said, overall the car runs great. I was just curious if a rich overrun would point to something else going on, or if those numbers are typical. Nobody has any values to throw out there? Thanks, Mike. |
Lo-Fi Version | Time is now: 19th May 2024 - 03:52 PM |
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 ... |