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 )

 
 Reply to this topicStart new topic
> Dyno pull questions, Too Lean?
audio_file
post Dec 7 2013, 07:03 PM
Post #1


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
Hey all, took my '75 2.0 to a dynojet dyno last week to establish a baseline of sorts. Based on receipts from previous owners, I think it has Euro-spec Mahle p's and c's, a web-cam of unknown grind, to go with the dual webers she sports. Here were the results:
(IMG:http://www.914world.com/bbs2/uploads_offsite/i219.photobucket.com-13409-1386464602.1.jpg)

I paid for two runs, but the guy running the dyno said I was so lean he wasn't comfortable doing a second pull. The sheet shows it being right around 14-17:1 most of the pull, and richening up after 5k rpm. Is that not where I should be with this car? Also, the resistance of the dyno wheel exposed the ignition irregularities you see on the power graph, any suggestions on what that could be? I'm running a svda dizzy out of a 1.8 car, with pertronix, and the total advance set at about 28 @3500 RPM (I THINK, I can't remember exactly, it's been too long since I did it, lol).
Thanks, as always!
Chris
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Dec 7 2013, 07:10 PM
Post #2


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
Way too lean. So lean that it was breaking up and detonating, thats what those peaks and valleys are in the power plots.

Flat line it at 13:1 and the engine will be happy for AFR
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
audio_file
post Dec 7 2013, 07:20 PM
Post #3


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
Thanks Jake! Guess I'll be finding a good carb-tuner to get these re-jetted/adjusted. Is it likely that I've done damage running the car like this? (not too hard, just normal-ish driving)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914werke
post Dec 7 2013, 07:21 PM
Post #4


"I got blisters on me fingers"
**********

Group: Members
Posts: 10,059
Joined: 22-March 03
From: USofA
Member No.: 453
Region Association: Pacific Northwest
Nice! Who's chassis Dyno?
User is online!Profile CardPM
Go to the top of the page
+Quote Post
audio_file
post Dec 7 2013, 07:24 PM
Post #5


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
QUOTE(rdauenhauer @ Dec 7 2013, 05:21 PM) *

Nice! Who's chassis Dyno?

Hey Rich! Marysville Speed and Custom in Smokey Pt, they had a 2 pulls for $50 deal last weekend.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Dec 7 2013, 07:29 PM
Post #6


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
If you just pulled it a couple of times you'll be ok.
I'd go up 2-3 main jet sizes to start, BUT check fuel pressure and float levels first, else jetting may not help.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
audio_file
post Dec 7 2013, 07:33 PM
Post #7


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
QUOTE(Jake Raby @ Dec 7 2013, 05:29 PM) *

If you just pulled it a couple of times you'll be ok.
I'd go up 2-3 main jet sizes to start, BUT check fuel pressure and float levels first, else jetting may not help.


That was the only pull, but I've probably put 3k on it in the past year set up that way, THATS what I'm worried about!
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Dec 7 2013, 07:47 PM
Post #8


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
The street will take much longer to kill it than the dyno. It you were driving it around at WOT all the time I'd be worried, but you can't do that on the street.

Do you have ANY exhaust leaks?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
audio_file
post Dec 7 2013, 07:51 PM
Post #9


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
QUOTE(Jake Raby @ Dec 7 2013, 05:47 PM) *

The street will take much longer to kill it than the dyno. It you were driving it around at WOT all the time I'd be worried, but you can't do that on the street.

Do you have ANY exhaust leaks?

I backdated the 75's exhaust with pipes from a 73-74, and they were a bit out of alignment, requiring a lot of massaging by the guys at triad to quiet down a leak once they were bolted up... Not noisey anymore, but could still be a small leak there...
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Dec 7 2013, 07:57 PM
Post #10


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
Then thats where part of the lean condition may come from.. It may not really be that lean..

But the power was breaking up… Or the plugs are firing late.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
messix
post Dec 7 2013, 08:02 PM
Post #11


AKA "CLUTCH KILLER"!
*****

Group: Members
Posts: 6,995
Joined: 14-April 05
From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada
Member No.: 3,931
Region Association: Pacific Northwest
was Cam running the dyno?

they're good guys up there.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
audio_file
post Dec 7 2013, 08:11 PM
Post #12


Member
**

Group: Members
Posts: 295
Joined: 6-August 11
From: Everett, Wa
Member No.: 13,409
Region Association: Pacific Northwest
Ok, any other way to check for exhaust leaks besides feeling for air?
I believe the lean reading honestly, the person I bought it from had some major issues getting it to pass emissions in his area, finally leading him to sell the car. I'm sure he had it set up to run lean trying to get it to pass...
Not sure the name of the guy running the dyno, seemed knowledgable enough to keep me from ruining my car, lol.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
r_towle
post Dec 7 2013, 08:22 PM
Post #13


Custom Member
***************

Group: Members
Posts: 24,574
Joined: 9-January 03
From: Taxachusetts
Member No.: 124
Region Association: North East States
Cover the tailpipe (s) with a piece of wood while it's running.
Any leaks get louder and easier to find.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
gothspeed
post Dec 7 2013, 08:39 PM
Post #14


Senior Member
***

Group: Members
Posts: 1,539
Joined: 3-February 09
From: SoCal
Member No.: 10,019
Region Association: None
+1 ....... right where that dashed line is where the fuel should be under load ...... right around 13:1 ..... (IMG:style_emoticons/default/smile.gif)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
« Next Oldest · 914World Garage · Next Newest »
 

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: 15th May 2024 - 02:03 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 ...