Dyno..usefull interpitaion wanted

[David Carter]

Boom, hope i peaked your interest. Got my subaru dyno'd

They guy that dyno'd my car. gave me alot of bad news in the hopes (i'm assuming) i'd let him tool on my car.

Now I don't really believe him... He said i was going into detonation..as far as my understanding.. you either detonate and blow your motor or you don't.. you can't HOVER in detonation.

Now what i did have was bad o2 sensor issues because of the larger exhast issue most subarus run into.

All i asking if it's possiable is if someone can read this dyno and give me thier best read on it.

Mods:
Borla Headers/up-pipe,
Bell mouth 2,3/4 Downpipe
Stromung mid-pipe and cat.
Cobb tuning exhaust
Unorthidox Pullies (all of em)
Manitcore 8.5MM Race wires
Weapon R "secret weapon" intake

Suspention:
KYB GR2
Perrin Springs
Power Suspention Race complete chassie bushing kit
Whiteline rear diff and support bushings
Whiteline Gold Endlinks
Addco 25mm Custom Front Sway bar
Hotchkins 25+mm Rear Sway Bar

Power Slot rotors F&R
EBC Green pads
Goodridge Steel Braided Brake lines.
STI Group N Engine, Trannie, Pitch Mounts

Please give me your best interpitation.

David Carter

[Kelly]

ya, your deffinatelly running lean. That red dotted line is where you want your AFR. Did he throw on some "knock ears" or sensor of some sort to confirm this?

The dyno sheets from my car look much different, when I had about the same mods as yours. I had much more fuel, like high 12's.

It doesnt necceserally mean your in detonation if your lean however. What that dyno sheet doesnt tell, is where the ignition timing is. Our ECU already pulls back an asston of timing cause the car didnt come stock with an intercooler.

I think Id change the O2 as well, and maybe go a bit easy on her.

[IronMonkeyL255]

Don't the minor dips in the graph represent detonation?

[David Carter]

ya, your deffinatelly running lean. That red dotted line is where you want your AFR. Did he throw on some "knock ears" or sensor of some sort to confirm this?

He clipped something to the coilpack..thats about it. This was my first dyno so i still didn't know what all comes in a good package.

The dyno sheets from my car look much different, when I had about the same mods as yours. I had much more fuel, like high 12's.

It doesnt necceserally mean your in detonation if your lean however. What that dyno sheet doesnt tell, is where the ignition timing is. Our ECU already pulls back an asston of timing cause the car didnt come stock with an intercooler.

I think Id change the O2 as well, and maybe go a bit easy on her.

I did change it right away...check engine light, Mil fix..2 days check engine light same code... O2 sensor bung fix 4 days ,check engine light same code.....my 2.5 rs does the same..

David

[free5ty1e]

The dips in the A/F graph represent overly-rich readings. It looks like you're running an efficient ~14.7:1 until near the end of the dyno run, when the ECU decides its time to dump more fuel.

Detonation, by the way, can occur without you blowing your engine. It's when the detonation goes unchecked and uncompensated for that it becomes run-away detonation and causes catastrophic engine failure. Our ECUs know enough to pull timing to prevent this. Each detonation (or knock) event does put additional stresses and wear on the engine internals though.

What boost level were you running for this?

[IronMonkeyL255]

I was talking about the dips in the hp/tq graph.

[tonflo]

You are getting way lean about 4700 rpm

[BAC5.2]

I'll do my best to interpret it for you....

First of all, the little dips in the graph show timing correction, not det. Det is knock. Knock pulls timing. So does a bunch of other stuff.

See the dip from 2500 RPM to about 3750 RPM? There is no corresponding dip in fuel, so what does that tell me? You pulled a little timing. Maybe one or two degrees. If it was a boost dip, you would have seen a slight fuel increase (further lean).

A bad oxygen sensor would have actually defaulted to open-loop mode, unless there is a short (in which case the car will try to stay closed loop while on-boost). Open loop = rich as a mother. Like smelly black smoke rich. I noticed when my O2 sensor wen't bad, and when Matt's wen't bad, both of our cars ran horribly lean. Mine was lean to the point of getting 23mpg!

So, replace the 02 sensor and try the dyno again. I bet your AFR will richen up, and the ECU won't pull so much timing.

The clip on the #1 plug wire is for engine RPM.

[BAC5.2]

You are getting way lean about 4700 rpm

You've got it the other way around. At 4700 he finally starts richening up.

You aren't allowing the computer to control boost anymore, are you? Computer probably figures "shit, I can't do anything to correct this." and dumps fuel to 100% IDC.

[tonflo]

My mistake, I knew what I meant, but I said it wrong. Does that make sense? Sorry. Isn't a safe a/f under hi boost in the 11-12 range?

[Impregacy]

isn't detonation (at least the destructive kind) usually pretty audible. and it seems like it would also be felt by the driver if it were happening that much. it's never happened on my car but it seems like it would send a noticeable vibration through the car and i would know it if it happened.

[douglas vincent]

The really dangerous detonation is Pre-ignition. It very destructive and is what will shatter piston rings and crack your pistons. I have suffered this more than I want (two shot engine to show for it).

This type of detonation is VERY audible and sounds like rocks hitting up into your exhaust, or bb's in a tin can.

The other style of detonation is not so audible, if at all, and is what "melts" your pistons tops. This can take a long long time, if its occasional, or in as short as 20 minutes if you are running at the track 100%, and then you get piston failure.

Predetonation occurs on the upstroke of the piston and that is why it is so destructive.

The other detonations occur as uncontrolled burn of fuel and air, but often at about the same time as you are supposed to have ignition, or as a second ignition on the downstroke.

[BAC5.2]

Doug's got it.

Pre-det is audible. It's the sound of one cylinder trying to spin the other 3 backwards. The only problem, is that the other 3 are still spinning forwards.

Causes of pre-det? Bad bad tuning of aftermarket engine management. It would have to be more than 12 degrees of timing advance, I'd think. It's actually pretty difficult to get the engine to ACTUALLY ignite before the piston is at TDC.

Another cause, is simply WAY to hot, igniting remaining fuel fumes before the piston reaches TDC. Carbon deposits on the piston face or combustion chamber will promote this, as they will create hot-spots that can promote pre-det. Another side effect of pre-det is hurting valves. But of course, if you are pre-detonating, the valves are the least of your concerns.

A sign of pre-det is back-fires. Where the combustion explosion hits, then the intake valves open and POP the flame exits through the intake valve and back through the throttle body.

Other det is just like Doug said. Just an uncontrolled burn. This kind of detonation isn't THAT detrimental to performance, but it will increase combustion chamber temperatures and as doug said, melt pistons and such.

Doug has got the most experience with both types of any of us here on the boards.

[David Carter]

What boost level were you running for this?

The mods i listed are all i have.. i haven't messed with MBC'S or any kind of aftermarket computer. ECU's Stock. Boost is made by the stock hardware. The only thing i'm not mentioning is i raided Vibrant's Catalog and redid all the piping in larger diameter stainless steel pipe and silicone hose, removed the airbox and resonatorand went with a modified Weapon R "secret weapon" open air unit.. I also replaced ALL the stock dry-rotted rubber vac lines and hoseing with silicone vac lines..

So, replace the 02 sensor and try the dyno again. I bet your AFR will richen up, and the ECU won't pull so much timing.

Done, we dyno'ed the car and then went to an auto-cross at cal-ripkin stadium,MD when i got home the next day i replaced all the o2 sensors. and installed all the MIL fix's i could find.

I'm gonna try the dyno again on Feb 18th when the next race is.

David

[free5ty1e]

i replaced all the o2 sensors

...all of them?

[Legacy777]

I'm going to add a few things.

Personally, I don't think your engine is detonating.

From my experience dynoing the car, and doing a little reading....I think there's two separate things going on.

You do probably need a bigger fuel pump, and or need to verify all the sensors are working properly.

My dyno run has the same dip at around 4200 rpm. Below that, AFR is higher....around 12.5. It's not overly high, but higher. Then it drops significantly.

There's two reasons I can see for this. The ECU is going from closed loop to open loop. OR the VE of the combined engine & turbo severely drops as engine rpm increases. It's probably a slightly combo of both. It'd be interesting to see dyno runs of guys with a stock ej22t motor, but higher flowing turbo, and see what their hp/tq numbers and AFR is like.

One other thing to note is that if they just stuck a sniffer type wand up the tail pipe, it's not a true reading of AFR's. O2 content will change after the Oxidation reaction in the catalyst.

Here's my dyno scans
http://www.main.experiencetherave.com:8 ... gdyno1.jpg
http://www.main.experiencetherave.com:8 ... gdyno2.jpg

log from my wideband
http://www.main.experiencetherave.com:8 ... wblog1.xls