Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

So apparently detonation doesnt kill engines...*dyno charts!*


  • Please log in to reply
36 replies to this topic

#1 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 08 July 2005 - 08:34 PM

I'm about to loose my sanity over what my Outback is doing/has been doing...wait, its already gone! :alien:

1996 Legacy Outback Wagon....EJ25D Phase 1 (earliest DOHC EJ25, the 155 hp version), 4EAT AWD....201k miles.

Its all BONE stock except for STi struts (with stock OB springs and strut mounts).

What does it do? CONSTANTLY detonates/pings/pre-detonates/knocks on accel to any sort of speed. All the time, it does it. *Ttt..T..TT...ttttttTTTTTTTTT....t...T....T...ttt....T...*

ALL OF THE TIME.

Now...its done this since I got it at 148k miles years ago...still does it to this day. Run 93 in it and it stops...mostly...but with it normally getting 20~24 MPG around town...with gas prices as they are, I can barely afford the 87 that goes in it.

Assuming its done this since mile 1....how the heck has this engine lasted so long detonating/knocking/pinging/pre-detonating all the time?

No CELs....EVER....I should find a spare knock sensor to throw in it and see if that makes any difference.

I thought engines were supposed to blow up when they knock/detonate/predetonat/preignite/ping.....

<------------is HIGHLY confoozed. :confused: :confused: :confused: :confused:

#2 Legacy777

Legacy777

    Moderator

  • Moderator
  • 12,604 posts
  • Houston, Tx

Posted 08 July 2005 - 08:49 PM

Any codes stored in the ECU?

Have you checked your knock sensor? I wonder if it's not working. You might want to test it. Replace it, and then reset the ECU.



#3 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 08 July 2005 - 09:00 PM

I'll hook up DeltaDash to it tomorrow and see whats what...maybe throw it on the dyno and do some logging....

I might grap onto a knock sensor off an STi for a few pulls and see whats what...

#4 blitz

blitz

    Banned

  • Banned
  • 1,091 posts
  • Warren, Michigan

Posted 08 July 2005 - 09:28 PM

...how the heck has this engine lasted so long detonating/knocking/pinging/pre-detonating all the time?

You braggin' or complainin'? :D Damn, I was having a difficult time finding the actual question in your post. :eek:

I thought engines were supposed to blow up when they knock/detonate/predetonat/preignite/ping...

Every car I've ever owned (normally aspirated) has ALWAYS been happy operating at the theshold of knock (trace amounts at part throttle). Prolonged, heavy knocking at WOT is a recipe for disaster.

Encountering det under forced-induction conditions is a more a serious problem. Piston contruction and alloy plays a large role in how well a given motor can tolerate det. The high ring-pack position which is popular, makes for a fragile top land. A forged racing piston designed for abuse will be more tolerant, but not indestructable. Det as a result of spark-lead can bring slightly different results than det as a result of lean fuel.

In short, there is no simple answer. It's a matter of understanding and minimizing your risk.

#5 RallyKeith

RallyKeith

    Got Subaru(s)?

  • Members
  • 1,481 posts
  • Reading, Pa

Posted 09 July 2005 - 09:22 AM

Well, since you have Delta Dash have you considered turning down the global ignition timing? I just bought a 96 Leg GT from another board member that only ran 93 in it. When I get it on the road I plan to try 87 or 89 and if needed using delta dash to set the global timing down a few degrees.

Keith

#6 Guest_shadow_*

Guest_shadow_*
  • Guests

Posted 09 July 2005 - 02:50 PM

Check the plugs.... If you see 'salt and pepper' fix it asap! A lot of engines will go a long time on light ping/detonation without failure - doesn't mean they SHOULD! ;)

#7 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 09 July 2005 - 02:56 PM

I cant get delta dash to work on it.

that being said...

Ok...so...run 1 is not 100% warm...been sitting for a while while beeing strapped on the dyno etc etc...

Run2 is when its fully warm....there you can see between 4k and 5k the power loss that it has....strange aint it?

these are all 2nd gear pulls since thats the only gear it stays in.

Posted Image

Now...after running water thru it as "steam cleaner" and some brake cleaner....then disabling the EGR...and some C16...THEN installing a NEW knock sensor...not much improvement at all.

Posted Image

#8 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 09 July 2005 - 03:00 PM

Its pretty typical for late-model engines to be set up so that there is light detonation at WOT. Sort of an indication that the engine is walking the tightrope between greatest efficiency (of some type) and engine death. Sort of like speeding doesn't kill you every time, just when you do it too much and something else goes wrong.

"Detonation doesn't kill engines. People kill engines." :lol:

#9 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 09 July 2005 - 03:32 PM

Ok...after ECU reset...same conditions...(mix of 10 gal of 87 and 5 gal of C16, new knock sensor, EGR disabled)

5 runs back to back to back to back to back.

Posted Image

Hm...not any better.

#10 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 09 July 2005 - 03:42 PM

HOLY CR*P!

Doesn't look like it is just "light detonation"... Have you tried it open-loop, or can't you realistically do this on late models? Maybe try a differenct ECU?

That is quite a drop-off.

#11 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 09 July 2005 - 03:48 PM

Ok...since I was bored:

18=std paper filter
20=K&N Drop in pannel filter
22=NO air filter

Posted Image

Looks like any sort of aftermarket filter is a wate of money.

#12 blitz

blitz

    Banned

  • Banned
  • 1,091 posts
  • Warren, Michigan

Posted 09 July 2005 - 03:57 PM

WJM, those are fantastic dyno charts. The engine's detonating heavily as it climbs right into the range of greastest volumetric efficiency (torque peak).

For whatever reason, your knock sensor circuit ain't doing squat.

It's interesting that the first run is clean then the subsequent runs go to hell. The normal run looks really good, with the two peaks and everything.

Question: What plug type & number are you running? I don't know why, but the plugs as being antagonistic are raising a red flag in my feeble brain. I know the knock correction isn't working, but still ... that looks like way too much abnormal combustion going on.

#13 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 09 July 2005 - 04:04 PM

...
Question: What plug type & number are you running? I don't know why, but the plugs as being antagonistic are raising a red flag in my feeble brain. I know the knock correction isn't working, but still ... that looks like way too much abnormal combustion going on.

I was thinking something like preignition, too, but figured WJM had the right parts in it. One normal-ish run, and things go south with the engine hot.

#14 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 09 July 2005 - 04:14 PM

its got the OE plat-num $12 each plugs...coil/plugs/wires are less than 15k old...all replaced about 6~8 months ago.

I am going to pull the plugs and install some one step colder NGK V-Power plugs

There was no detonation to be heard on the dyno. :confused: :confused:

When I go WOT on the street, it goes away. Its only during 1/3~1/2~2/3 throttle accel under load...like, traffic conditions...that you can hear it. I did several of those type pulls (no charts tho) on the dyno and only got detonation once. :confused:

#15 Olnick

Olnick

    Ol' Subaru Guy

  • Members
  • 2,581 posts
  • Honolulu HI

Posted 09 July 2005 - 04:26 PM

WJM, NorthWet, Blitz, anyone--care to offer a quickie little tutorial for those of us who are less "literate"?

Do the bottom lines represent torque and the top, horsepower?

What are the big drops @ 3500 and 4300? What's the peak @ 4900 mean?

How are you seeing detonation? The squiggiliness?

I don't expect a lot of detailed explanation, but I'd love to know what you're looking for and what you're seeing!

#16 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 09 July 2005 - 06:08 PM

The line on the dyno that starts out higher at low RPM is for torque (relatively RPM independent) and the lower one at lower RPM is HP (by definition, RPM dependent). The torque curve should have a relatively gentle arch from around 2k to just before redline, with a drop off expected towards redline as the engine's ability to "breath" becomes a factor. HP should climb steadily (assuming said flat torque curve) until it peaks at some RPM higher than peak torque RPM, and then fall off as torque falls off.

That horrible fast drop in the 2 curves in the middle of the RPM range is very abnormal, indicating something has disrupted combustion, and not just a little bit. We are assuming it is abnormal combustion (detonation/preignition) because of what WJM has told us earlier.

WJM's last post hints at something else, though, since he says that he doesn't hear detonation on the dyno or at WOT. It may just be that something is causing misfire, either a lean mixture or an ignition fault.

#17 nipper

nipper

    Semi Elite Master of the

  • Members
  • 17,562 posts
  • Long Island NY

Posted 09 July 2005 - 06:30 PM

Back to pinging ..
Modern engines do run on the edge of pinging. They run ultra lean. There is the "popcorn" pinging and knocking. Knocking bad VERY bad. Popcorn pinging can be normal, can also mean that there is heavy carbon buildup in the cylinders that create hotspots. The pinging you hear is "autoignition". The hot carbon spots is igniting the fuel air mixture. If ist been like this for 60K and still running, i wouldnt worry about it. Have you tried just for the hell of it using 2 tanks of premium or a can of octame boost to see if it changes or go away?

nipper

#18 Olnick

Olnick

    Ol' Subaru Guy

  • Members
  • 2,581 posts
  • Honolulu HI

Posted 09 July 2005 - 07:03 PM

Thanks, NorthWet--I appreciate the excellent explanation.

#19 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 09 July 2005 - 09:26 PM

Thanks, NorthWet...

No problem. I should have addressed your "squiggly" question, and that is it is mostly caused by instantaneous variations in power output and measuring equipment variations. Stuff like that sometimes add, sometimes cancel, but all is pretty much ignorable. Published curves usually smooth out the curves to rid them of that "noise".

#20 blitz

blitz

    Banned

  • Banned
  • 1,091 posts
  • Warren, Michigan

Posted 10 July 2005 - 01:24 PM

its got the OE plat-num $12 each plugs...coil/plugs/wires are less than 15k old...all replaced about 6~8 months ago.

Since the problem DOES seem to be ignition-related, having that stuff new eliminates a lot of possibilities right there.

I am going to pull the plugs and install some one step colder NGK V-Power plugs

That's exactly what I was gonna suggest. What is C16? Unleaded race gas?

There was no detonation to be heard on the dyno. :confused: :confused:

What exactly were you hearing at the point where the power drops off? What sort of change in the exhaust note? It's possible that you've got pre-ignition as opposed to detonation.

When I go WOT on the street, it goes away. Its only during 1/3~1/2~2/3 throttle accel under load...like, traffic conditions...that you can hear it. I did several of those type pulls (no charts tho) on the dyno and only got detonation once. :confused:

The timing is modulated by throttle angle as well as it is mapped by RPM. Finally, the bulk timing map is trimmed a little by signal from the atmospheric pressure sensor and the intake air temperature sensor.

#21 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 10 July 2005 - 05:51 PM

Since the problem DOES seem to be ignition-related, having that stuff new eliminates a lot of possibilities right there.


Yep.

That's exactly what I was gonna suggest. What is C16? Unleaded race gas?


Yep. C16 is leaded race fuel with an octane rating of 116 or so. It is THE fuel to have when doing race gas maps for big power....bad for cats tho.


What exactly were you hearing at the point where the power drops off? What sort of change in the exhaust note? It's possible that you've got pre-ignition as opposed to detonation.



Nothing. Nothing. No, both are the same thing...what it feels like is that the timing is being cut back to about 10deg or so....ive done back to back pulls in N/A EA82 subies playing with timing...and retarding the timing does the same thing...creats a loss of power.

The timing is modulated by throttle angle as well as it is mapped by RPM. Finally, the bulk timing map is trimmed a little by signal from the atmospheric pressure sensor and the intake air temperature sensor.


MAF+MAP+TPS+Engine Temp+Knock Sensor=timing. If only it would do so....

On the stock subies...timing is ECU as per preset timing/fuel map plus the inputs from TPS+MAP/MAF+knock sensor. Its nt that intelligent...it pulls timing...then advances it back as per knock.

#22 NorthWet

NorthWet

    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 10 July 2005 - 06:06 PM

WJM[/b]]
its got the OE plat-num $12 each plugs...coil/plugs/wires are less than 15k old...all replaced about 6~8 months ago.


Since the problem DOES seem to be ignition-related, having that stuff new eliminates a lot of possibilities right there.

May I point out that parts that are 6-8 months old and 15k miles neither constitutes "new" nor eliminates them as possibilities? I have had name brand (but not NGKs) sparkplugs fail in as little as 1k miles, and wire sets not much longer. As one tuning manual I read said, "If your car isn't worth a new set of plugs for tuning use, then it isn't worth tuning." Even a set of V-Powers would probably work just fine for a few pulls. (I personally haven't found a use for the more pricey ones yet, but then I am frugal. :rolleyes: )

BTW, if I read WJMs response properly (and I apologize in advance if I didn't :) ), he implied/stated that preignition and detonation are the same thing. It is not, though both forms of abnormal combustion can exacerbate the other.

#23 blitz

blitz

    Banned

  • Banned
  • 1,091 posts
  • Warren, Michigan

Posted 10 July 2005 - 08:02 PM

Nothing. Nothing. No, both are the same thing...what it feels like is that the timing is being cut back to about 10deg or so....ive done back to back pulls in N/A EA82 subies playing with timing...and retarding the timing does the same thing...creats a loss of power.

In all fairness, moving the timing in either direction (+/-) of the optimal setting would result in reduced power. The specific setting that achieves the highest mean combustion pressure will produce the greatest power. My point being that if some abnormal iginition event were causing early combustion light-off (pre-ignition), you'd see a sudden drop in power. This COULD be occurring without hearing any classic detonation noises on account of the abundant octane of the fuel you're running during the test. Pre-ignition can cause bent rods and smashed big-end bearings similar to nitrous.

I'm really curious as to how all this pans-out. Those dyno charts are really great. :D Thanks for sharing this. :headbang:

#24 99obw

99obw

    this space for rent

  • Members
  • 1,595 posts
  • Ithaca area

Posted 12 July 2005 - 06:27 AM

If the problem were ignition related wouldn't the air/fuel curves go rich during the reduced power portion of the HP curves?

#25 WJM

WJM

    SUBARU

  • Members
  • 7,828 posts

Posted 12 July 2005 - 07:18 AM

If the problem were ignition related wouldn't the air/fuel curves go rich during the reduced power portion of the HP curves?


No. The air/fuel is dependent upon how much fuel is delivered. It has very little to do with where the timing is at.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users