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
> Road Test, Slow acceleration and valve chatter
VA_914
post Oct 25 2020, 01:12 PM
Post #1


Newbie
*

Group: Members
Posts: 4
Joined: 31-March 08
From: Hampton, VA
Member No.: 8,873
Region Association: MidAtlantic Region



I am finally road testing my 2.0 restoration and haven't quite got it right yet. It starts fine, runs smooth idling or revved up in the driveway but on the road test it accelerated slow, with what sounds like valve chatter when I give more gas to accelerate. It wouldn't go over 3000 rpm in 1st, 2nd or third. I tweaked the timing a bit and it seemed to get better, less chatter and almost up to 4000 rpm. Suggestions, comments; am I on the right track?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Superhawk996
post Oct 25 2020, 01:53 PM
Post #2


914 Guru
*****

Group: Members
Posts: 5,673
Joined: 25-August 18
From: Woods of N. Idaho
Member No.: 22,428
Region Association: Galt's Gulch



QUOTE(VA_914 @ Oct 25 2020, 03:12 PM) *

sounds like valve chatter.


(IMG:style_emoticons/default/welcome.png)

I'm going to suggest what you're hearing is detonation or "ping", that could maybe be described as a clatter or chatter sound. Never heard of the term valve chatter that could be put in the context of acceleration.

What freqently happens is that as you tip in on the throttle the mixture goes lean and/or you're running way too much timing advance and that induces detonation.

Detonation will damage an engine very quickly.

Maybe you can describe the nose a bit more if you don't think it matches my description.

The fact that you can't rev to more than 3000 RPM under load says something is very wrong. Likewise that it got better and the "chatter" decreased when you tweaked it says something. When you say you tweaked the timing what does that mean? There is a timing specification that needs to be set with a timing light. Is that what you did or are you just moving the distributor and quessing?

Way to many factors to guess at. Also depends on whther engine is still Fuel Injected, running carbs, and whether or not it even still has the proper distributor in it.

Need more information and and folks will try to help.
User is online!Profile CardPM
Go to the top of the page
+Quote Post
VA_914
post Oct 25 2020, 04:40 PM
Post #3


Newbie
*

Group: Members
Posts: 4
Joined: 31-March 08
From: Hampton, VA
Member No.: 8,873
Region Association: MidAtlantic Region



Yes, "ping" is what I was trying to describe, sorry for the vague terminology. By tweaking the timing, I changed it from about 22 degrees to 27 degrees (as indicated by the dial on the timing light) by rotating the distributor. I had originally set it a few years back (2015) but I have removed the engine a couple times since then due to major oil leak and transmission issues and was suspect of the timing when I heard the "ping".

When I began the restoration (2006), it had carbs. It is now fuel injected. I bought another 1974 2.0 with severe body issues for parts and a second set of FI components for a 1974 2.0. I picked the best of those to put on the restore, trying to keep things compatible using a document by Paul B. Anders I found on reenlist.

A little more of the backstory; I shipped the engine to Arizona to be rebuilt (by Greg Robbins) over 10 years ago. He put in 96 mm Keith Black pistons and Raby Cam kit, so it's about 2056 cc now. I added a couple before and after pics.

Attached Image

Attached Image

Attached Image

Attached Image
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
porschetub
post Oct 25 2020, 05:11 PM
Post #4


Advanced Member
****

Group: Members
Posts: 4,695
Joined: 25-July 15
From: New Zealand
Member No.: 18,995
Region Association: None



QUOTE(VA_914 @ Oct 26 2020, 11:40 AM) *

Yes, "ping" is what I was trying to describe, sorry for the vague terminology. By tweaking the timing, I changed it from about 22 degrees to 27 degrees (as indicated by the dial on the timing light) by rotating the distributor. I had originally set it a few years back (2015) but I have removed the engine a couple times since then due to major oil leak and transmission issues and was suspect of the timing when I heard the "ping".

When I began the restoration (2006), it had carbs. It is now fuel injected. I bought another 1974 2.0 with severe body issues for parts and a second set of FI components for a 1974 2.0. I picked the best of those to put on the restore, trying to keep things compatible using a document by Paul B. Anders I found on reenlist.

A little more of the backstory; I shipped the engine to Arizona to be rebuilt (by Greg Robbins) over 10 years ago. He put in 96 mm Keith Black pistons and Raby Cam kit, so it's about 2056 cc now. I added a couple before and after pics.










Even the cat knew the carb was shit (IMG:style_emoticons/default/av-943.gif) ,nice work so far.
User is online!Profile CardPM
Go to the top of the page
+Quote Post
Superhawk996
post Oct 25 2020, 05:53 PM
Post #5


914 Guru
*****

Group: Members
Posts: 5,673
Joined: 25-August 18
From: Woods of N. Idaho
Member No.: 22,428
Region Association: Galt's Gulch



Looks Great.

If possible you may want to check mixture. Wideband O2 would be ideal.

Running a 2056 on stock FI has been done by others but there is usually tweaking involved to get it running well.

The wild card is what the compression ratio was set at when rebuilt with the 96mm pistons. Have you tried using premium? Does that reduce the ping?

27 degrees timing should be fine.

Other stuff would focus on not having uncontrolled vacuum leaks that could be leaning you out.

Bottom line, you can do some tuning here an there but don't run it hard for extended periods with it detonating. It really can wreck an engine in short order. Need to find what is causing it and fix. Not running clean up to 5000 rpm is a sign that something is wrong. Any backstory on the injectors? Are you sure they are cleaned and flowing properly? Fuel pump pressure checked and set correctly?
User is online!Profile CardPM
Go to the top of the page
+Quote Post
VA_914
post Oct 25 2020, 08:13 PM
Post #6


Newbie
*

Group: Members
Posts: 4
Joined: 31-March 08
From: Hampton, VA
Member No.: 8,873
Region Association: MidAtlantic Region



Yes, I now run premium in it, but that didn't seem to have much of an effect. Also, the injectors were checked when the engine was rebuilt. I have installed both a fuel pressure gauge and vacuum gauge in the engine compartment. The fuel is typically 28, but I have taken it up to 31 at times. My reasoning was that the displacement was 10% larger so I should up the pressure by 10%, assuming the injector pulse width remained the same. The vacuum is typically 10-12 psi at idle and goes up to 16 or so at higher rpm.

For O2 monitoring, I would need to weld a sensor into the heat exchanger? What other tweaks have people done for a 2056?

A couple other things wrt the mixture: There are two vacuum ports on the distributor bellows; one for advance and one for retard (I assume). The throttle body I am using only has one port that size, so I connect it to the port on the distributor side of the bellows and leave the other side of the bellows open to the air. Do I have this backwards?

The throttle body has an idle adjustment that allows air to pass around the throttle valve through a tube in the body. It also has a small screw that protrudes into the throat and keeps the throttle valve slightly open, depending on how you set the screw. Both effect the idle speed, presumably because they effect the mixture? I have a second throttle body that has two ports the same size as the distributor bellows, one above and one blow the throttle valve. It has the same type idle adjustment but no screw to keep the throttle valve slightly open. Should I try that one instead?

Lastly, I have two pressure sensors, one that Greg Robbins sent to Jeff Blysing to recalibrate for the larger displacement when the engine was rebuilt and one from the second injector set I bought. Unfortunately, I have mixed them up and don't know which is which. As it turns out, they perform a little different, but neither resolve the major issues (ping and 3-4000 max rpm).

BTW thanks for your comments and I appreciate the advice about the detonation damaging the engine. I have never gone more than around the block and my intuition told me to back off when I heard the "ping".
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914Toy
post Oct 25 2020, 08:19 PM
Post #7


Senior Member
***

Group: Members
Posts: 710
Joined: 12-November 17
From: Laguna beach
Member No.: 21,596
Region Association: Southern California



Long shot, are you sure your timing light is accurate
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
wndsrfr
post Oct 25 2020, 08:23 PM
Post #8


Senior Member
***

Group: Members
Posts: 1,427
Joined: 30-April 09
From: Rescue, Virginia
Member No.: 10,318
Region Association: MidAtlantic Region



QUOTE(Superhawk996 @ Oct 25 2020, 03:53 PM) *

Looks Great.

If possible you may want to check mixture. Wideband O2 would be ideal.

Running a 2056 on stock FI has been done by others but there is usually tweaking involved to get it running well.

The wild card is what the compression ratio was set at when rebuilt with the 96mm pistons. Have you tried using premium? Does that reduce the ping?

27 degrees timing should be fine.

Other stuff would focus on not having uncontrolled vacuum leaks that could be leaning you out.

Bottom line, you can do some tuning here an there but don't run it hard for extended periods with it detonating. It really can wreck an engine in short order. Need to find what is causing it and fix. Not running clean up to 5000 rpm is a sign that something is wrong. Any backstory on the injectors? Are you sure they are cleaned and flowing properly? Fuel pump pressure checked and set correctly?

(IMG:style_emoticons/default/agree.gif)
Be careful if it's pinging...that's caused by too lean fuel mixture, too hot spark plugs, too far advanced timing, poor fuel combined with high compression ratio. It will definitely destroy a piston. I'm across the river from you in Smithfield and so is Steve Anderson. We can possibly noodle out what's up with your car...shoot a PM to me to connect up....
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
JeffBowlsby
post Oct 25 2020, 09:05 PM
Post #9


914 Wiring Harnesses
*****

Group: Members
Posts: 8,438
Joined: 7-January 03
From: San Ramon CA
Member No.: 104
Region Association: None



VIN check please. (IMG:style_emoticons/default/wink.gif)
User is online!Profile CardPM
Go to the top of the page
+Quote Post
JeffBowlsby
post Oct 26 2020, 07:14 PM
Post #10


914 Wiring Harnesses
*****

Group: Members
Posts: 8,438
Joined: 7-January 03
From: San Ramon CA
Member No.: 104
Region Association: None



14729 on the 914 LE Registry. Great transformation.
User is online!Profile CardPM
Go to the top of the page
+Quote Post
wndsrfr
post Oct 27 2020, 04:55 AM
Post #11


Senior Member
***

Group: Members
Posts: 1,427
Joined: 30-April 09
From: Rescue, Virginia
Member No.: 10,318
Region Association: MidAtlantic Region



QUOTE(wndsrfr @ Oct 25 2020, 06:23 PM) *

QUOTE(Superhawk996 @ Oct 25 2020, 03:53 PM) *

Looks Great.

If possible you may want to check mixture. Wideband O2 would be ideal.

Running a 2056 on stock FI has been done by others but there is usually tweaking involved to get it running well.

The wild card is what the compression ratio was set at when rebuilt with the 96mm pistons. Have you tried using premium? Does that reduce the ping?

27 degrees timing should be fine.

Other stuff would focus on not having uncontrolled vacuum leaks that could be leaning you out.

Bottom line, you can do some tuning here an there but don't run it hard for extended periods with it detonating. It really can wreck an engine in short order. Need to find what is causing it and fix. Not running clean up to 5000 rpm is a sign that something is wrong. Any backstory on the injectors? Are you sure they are cleaned and flowing properly? Fuel pump pressure checked and set correctly?

(IMG:style_emoticons/default/agree.gif)
Be careful if it's pinging...that's caused by too lean fuel mixture, too hot spark plugs, too far advanced timing, poor fuel combined with high compression ratio. It will definitely destroy a piston. I'm across the river from you in Smithfield and so is Steve Anderson. We can possibly noodle out what's up with your car...shoot a PM to me to connect up....


Thinking might be fuel delivery is lean...filter or in tank pickup clogged?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
BeatNavy
post Oct 27 2020, 06:03 AM
Post #12


Certified Professional Scapegoat
****

Group: Members
Posts: 2,919
Joined: 26-February 14
From: Easton, MD
Member No.: 17,042
Region Association: MidAtlantic Region



QUOTE(VA_914 @ Oct 25 2020, 10:13 PM) *

Yes, I now run premium in it, but that didn't seem to have much of an effect. Also, the injectors were checked when the engine was rebuilt. I have installed both a fuel pressure gauge and vacuum gauge in the engine compartment. The fuel is typically 28, but I have taken it up to 31 at times. My reasoning was that the displacement was 10% larger so I should up the pressure by 10%, assuming the injector pulse width remained the same. The vacuum is typically 10-12 psi at idle and goes up to 16 or so at higher rpm.

For O2 monitoring, I would need to weld a sensor into the heat exchanger? What other tweaks have people done for a 2056?

A couple other things wrt the mixture: There are two vacuum ports on the distributor bellows; one for advance and one for retard (I assume). The throttle body I am using only has one port that size, so I connect it to the port on the distributor side of the bellows and leave the other side of the bellows open to the air. Do I have this backwards?

The throttle body has an idle adjustment that allows air to pass around the throttle valve through a tube in the body. It also has a small screw that protrudes into the throat and keeps the throttle valve slightly open, depending on how you set the screw. Both effect the idle speed, presumably because they effect the mixture? I have a second throttle body that has two ports the same size as the distributor bellows, one above and one blow the throttle valve. It has the same type idle adjustment but no screw to keep the throttle valve slightly open. Should I try that one instead?

Lastly, I have two pressure sensors, one that Greg Robbins sent to Jeff Blysing to recalibrate for the larger displacement when the engine was rebuilt and one from the second injector set I bought. Unfortunately, I have mixed them up and don't know which is which. As it turns out, they perform a little different, but neither resolve the major issues (ping and 3-4000 max rpm).

BTW thanks for your comments and I appreciate the advice about the detonation damaging the engine. I have never gone more than around the block and my intuition told me to back off when I heard the "ping".

From my experience and listening to others I don't think a basic 2056 is going to run that poorly using stock FI. It won't run great, but I think (as others do) that you have something else going on: timing and/or fuel delivery issues.

A couple of comments and feedback to questions.

1. Yes, a wideband sensor would be very helpful. You need to weld a bung in somewhere in the exhaust stream. Different schools of thought on where exactly. If you put it in the HE you're only getting one side of the engine, although the gasses will be hotter as it's closer to engine. It also depends on your actual muffler. Might want to search here to see examples of how it's been done.

2. I don't think there's a linear relationship between fuel pressure, displacement, and volume of fuel injected during the pulse. No matter, 31 psi shouldn't be terribly off.

3. Idle vacuum should be around 15 psi, although it depends on the cam. If you have the Raby 9550 (IIRC) cam, the only Raby cam designed for FI, then you may not. I've had two of those. One on D-Jet and one on Microsquirt. Neither pulled 15 psi in my case. They are also a little finicky cold, but that quickly goes away with some heat. That's my experience anyway. At WOT a vacuum gauge should show 0 psi. How are you measuring?

4. You aren't sure of the compression ratio? That is a wildcard. According to Jake the Raby 9550 really shouldn't go much above 8.5 (at sea level, which you are). Not sure that would cause what you're experiencing, but may impact idle or other behavior.

5. Not sure what you mean about throttle body and the small screw that keeps the valve open. Can you post a pic? AFAIK on a stock TB there's the idle air bypass valve which is that throat with the big screw that protrudes into it. That simply lets in more air into the manifold. If you have one port on the TB it goes to the retard port on the dizzy, the one that faces the dizzy body. Leave the advance port on the dizzy open.

6. I agree with Seahawk and John (wndsrfr). Focus on timing - verify the timing marks and your timing procedure -- and fuel delivery issues. Seahawk mentioned possible clogged injectors. I'd highly recommend sending them out for cleaning if they've been sitting around for 10 years. That's a cheap and effective way to remove that variable. Wndsrfr is a great resource local to you. If he's offering, let him help before you get too much further.

Good luck.

EDIT: I see in your post you said you "checked the injectors when the engine was rebuilt" What does that mean? Cleaned? If they were run at all at that time and have had ethanol sitting in them for 10 years....
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Gint
post Oct 28 2020, 11:44 AM
Post #13


Mike Ginter
***************

Group: Admin
Posts: 16,063
Joined: 26-December 02
From: Denver CO.
Member No.: 20
Region Association: Rocky Mountains



Still running points in the distributor and not a electronic replacement? if so, check/inspect your points, the plastic rubbing block, points gap and dwell.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
VA_914
post Oct 29 2020, 10:24 AM
Post #14


Newbie
*

Group: Members
Posts: 4
Joined: 31-March 08
From: Hampton, VA
Member No.: 8,873
Region Association: MidAtlantic Region



John came over yesterday and after pushing the car back and forth in 4th gear for an hour looking for timing marks, we finally decided to start it. He immediately said it wasn’t firing on all cyclinders and after a little checking it seemed both 3&4 were’t firing with loose wires/connectors being the likely suspect. Thanks for the help John and hopefully I can get it resolved in the next day or two.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
BeatNavy
post Oct 29 2020, 10:36 AM
Post #15


Certified Professional Scapegoat
****

Group: Members
Posts: 2,919
Joined: 26-February 14
From: Easton, MD
Member No.: 17,042
Region Association: MidAtlantic Region



QUOTE(VA_914 @ Oct 29 2020, 12:24 PM) *

John came over yesterday and after pushing the car back and forth in 4th gear for an hour looking for timing marks, we finally decided to start it. He immediately said it wasn’t firing on all cyclinders and after a little checking it seemed both 3&4 were’t firing with loose wires/connectors being the likely suspect. Thanks for the help John and hopefully I can get it resolved in the next day or two.

(IMG:style_emoticons/default/smilie_pokal.gif) @wndsrfr

Loose injector connectors? I had a really annoying minor issue where my #3 injector wire would pop out at random times. Usually happened when I was really enjoying a great ride with little traffic marveling how well the engine was running and sounding. I knew immediately when it happened, and because it was #3 the CHT gauge would show rapidly dropping head temps and the AFR gauge would go really lean. Then I'd have to find a safe place to pull over, pop the engine lid, etc. It wasn't a big deal but it was a buzz kill for my teener cruising bliss at the moment.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Superhawk996
post Oct 29 2020, 10:46 AM
Post #16


914 Guru
*****

Group: Members
Posts: 5,673
Joined: 25-August 18
From: Woods of N. Idaho
Member No.: 22,428
Region Association: Galt's Gulch



QUOTE(BeatNavy @ Oct 29 2020, 12:36 PM) *


Loose injector connectors? I had a really annoying minor issue where my #3 injector wire would pop out at random times.


This is the one thing I really hate about the vintage fuel injection system. The connectors used on teeners are archaic and lack basic features like being waterproof and having locking connectors that we now take for granted on modern machinery.

User is online!Profile CardPM
Go to the top of the page
+Quote Post
Root_Werks
post Oct 29 2020, 10:56 AM
Post #17


Village Idiot
*****

Group: Members
Posts: 8,287
Joined: 25-May 04
From: About 5NM from Canada
Member No.: 2,105
Region Association: Pacific Northwest



QUOTE(Superhawk996 @ Oct 29 2020, 09:46 AM) *

QUOTE(BeatNavy @ Oct 29 2020, 12:36 PM) *


Loose injector connectors? I had a really annoying minor issue where my #3 injector wire would pop out at random times.


This is the one thing I really hate about the vintage fuel injection system. The connectors used on teeners are archaic and lack basic features like being waterproof and having locking connectors that we now take for granted on modern machinery.


(IMG:style_emoticons/default/agree.gif)

I think D-Jet 914's rely on the little rubber boot to keep the injector plug in place. L-Jet much improved with metal locking clips.
User is online!Profile CardPM
Go to the top of the page
+Quote Post
DRPHIL914
post Oct 29 2020, 10:57 AM
Post #18


Dr. Phil
*****

Group: Members
Posts: 5,752
Joined: 9-December 09
From: Bluffton, SC
Member No.: 11,106
Region Association: South East States



also, in addition to the connection at the injector coming loose, which i have also seen once or twice, i would look close at the FI grounds. they are located at top of the case, hard to see with air cleaner in place but if you remove it you can see those spade connectors where they are bolted on , the female connectors on the harness get loose and may not even be connected, mine were working loose and would give me intermittent contact so i would get a burst of power and smooth running and then you could tell it was only firing at times on only one pair of injectors. but sounds likeit might me a easy quick fix for you!
User is online!Profile CardPM
Go to the top of the page
+Quote Post
Gint
post Oct 29 2020, 11:51 AM
Post #19


Mike Ginter
***************

Group: Admin
Posts: 16,063
Joined: 26-December 02
From: Denver CO.
Member No.: 20
Region Association: Rocky Mountains



That could also be the FI trigger points in the bottom of the dizzy. If memory serves me it fires two cylinders at a time. Can't remember which are pairs though at this point.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914_teener
post Oct 29 2020, 12:03 PM
Post #20


914 Guru
*****

Group: Members
Posts: 5,193
Joined: 31-August 08
From: So. Cal
Member No.: 9,489
Region Association: Southern California



QUOTE(Gint @ Oct 29 2020, 10:51 AM) *

That could also be the FI trigger points in the bottom of the dizzy. If memory serves me it fires two cylinders at a time. Can't remember which are pairs though at this point.



Ditch the stock dizzy........you will never look back.


That'd be my advice.

NICE car BTW
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

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:

 



- Lo-Fi Version Time is now: 28th March 2024 - 12:46 PM