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Old 11-21-2005, 02:17 PM   #1
jblaine
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Default Hydra, plugs, engine noise

I've got a version 8 EJ207 shortblock + WRX heads and a 16G, as a lot of you know. As part of that swap, I had purchased heat range 7 *and* 8 NGK iridium plugs. The heat range 8 plugs were purchased as a backup based on two things:

1. NASIOC user ebeck had "lots of knock" with heat range 7 and had to use 8 on his EJ207 setup (much larger turbo, however).

2. The compression ratio of the v8 EJ207 block with WRX heads is somewhat unknown. Quirt at Crawford Performance has told ebeck several times that it is roughly 9:1. I have not convinced myself firsthand of this yet.

So here we go:

I'm running a Hydra Nemesis.

Over the last 5 months (it feels like a tedious 2 years), I have been datalogging the hell out of my car. Here's the cliff notes version in chronological order:

- Swap done, using heat range 7 NGK iridiums

- Original Element Tuning map was reporting lots of knock. This was a rough map done for a PE1820 turbo.

- Sunoco GT100, 16psi peak, and conservative timing did not make this reported knock go away.

- Insert skepticism and some fear

- After discussion with Phil @ Element Tuning, I used the 100 octane tankfull to generate a new Knock Threshold map to suit my car.

- A month or so after that, I revisited this. I was uneasy about the knock voltage levels (regardless of octane) that seemed distant from the other main cluster at that RPM and load.

- I contacted Phil again. This time I provided him with a plot of my unloaded free-revving knock voltage from 0-6500RPM. I also provided him with portions of logs containing WOT pulls. I also provided him with 5 knock voltage plots showing 2+3+4 pulls from 2800-6800RPM at WOT. Lots of data, all done with 100 octane, reasonable boost, and reasonable timing.

- Phil commented that, aside from his car, he had never seen knock voltages that high in his Hydra tuning. Perhaps the heads are noisy. Regardless, it was his assessment that it was extremely unlikely that it was knock given the data in the logs sent.

- For reference, my knock threshold map was above 2.05 volts from 2400 to redline. I would consistently see 2.1 and 2.2 voltages in spots above 5600RPM.

- Before doing a track day at Sebring, I decided to do a compression test now that the swap had 3000 miles on it (many many many WOT pulls while tuning, etc). Compression was 150psi in all cylinders. Heat range 7 iridiums looked fine.

- Changed oil, did the Sebring track day, changed oil, yadda yadda.

- Ever-paranoid and cautious, I was still not convinced everything was okay, I decided to try heat range 7 NGK copper plugs. No significant change in noise level.

- Yesterday morning I pulled the copper plugs after 2 weeks of use. They looked normal/boring.

- I installed the heat range 8 NGK iridiums finally. DRASTIC change in knock voltage levels. I have seen a single 1.9 out of 20 pulls, and that was at 6500RPM. From 0-5700RPM the voltages are well below 1.7, mostly below 1.2 even.

- I got another tank of Sunoco GT100 last night and started rebuilding my entire knock threshold curve (I am currently at $280 in GT100 fuel just for the sake of tuning a basic knock threshold curve).

- Keep in mind that I have never heard a single audible detonation event.

THE QUESTIONS

a) What the hell is going on here?

b) I don't really care about the answer to this one, but was ebeck's "knock" as reported by his UTEC not knock at all? I clearly ran my car hard for 3000 miles on 93 octane and 18psi with high knock voltages from my heat range 7 plugs. The result? Perfect compression still. Car runs like a champ. Super crisp.
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Old 11-21-2005, 02:52 PM   #2
rjrutzky
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Quote:
Originally Posted by jblaine
a) What the hell is going on here?
Sounds like your car likes the 8 heat range plug better.

I use 7s on my 207 v7 and don't ever see over .9 on the knock volt (I am still at low boost though). Sounds like you made a good find for your car to me--congrats. Have you done any dyno tuning or just street. I'm scared to push mine with the base timing map until I get on a dyno.
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Old 11-21-2005, 02:56 PM   #3
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I have my suspicions but I don't want to be a "know it all." I'll see if someone else has the same conclusion but if not I'll answer of course.

Thanks,
Phil
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Old 11-21-2005, 05:06 PM   #4
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Quote:
Originally Posted by rjrutzky
Sounds like your car likes the 8 heat range plug better.

I use 7s on my 207 v7 and don't ever see over .9 on the knock volt (I am still at low boost though). Sounds like you made a good find for your car to me--congrats. Have you done any dyno tuning or just street. I'm scared to push mine with the base timing map until I get on a dyno.
I've done lots of street tuning (only) so far.

*pokes Phil*
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Old 11-21-2005, 05:15 PM   #5
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Quote:
Originally Posted by jblaine
I've done lots of street tuning (only) so far.

*pokes Phil*
I'm trying to get Phil to come to Atlanta. Know any other Hydra users that would sign a petition/fork out some dough?
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Old 11-21-2005, 05:34 PM   #6
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When I got my ver8 longblock from Japanstar it had range 8 irridiums in it. I never had any knock until a fuel tuning session inadvertently induced massive lean knock at 6300 RPM. Never had any knock since. Although my timing is certainly on the conservative side for a spec-C engine. This behavior didn't change AT ALL when I went to range 7 coppers (because I'm still just running the VF36).

I find it curious that the previous Japanese owner was running range 8 plugs. Maybe they know something we're just starting to clue in on?
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Old 11-21-2005, 06:43 PM   #7
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I've got a theory for you, mind you it's really out there.

Putting in a colder plug transferred more heat to the heads (valves in particular), the heated valves expanded more (lengthened) and closed the lash of the bucket-camshaft interface. Tighter lash meant quieter buckets and less false knock.

Please attack at will.
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Old 11-21-2005, 07:40 PM   #8
jblaine
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It's possible, bboy. I'm open to anything at this point. The shim clearances were all checked when I put the engine together though (all within spec).
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Old 11-21-2005, 07:44 PM   #9
jblaine
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Quote:
Originally Posted by rjrutzky
I'm trying to get Phil to come to Atlanta. Know any other Hydra users that would sign a petition/fork out some dough?
Nope.

Your best bet is to post in the Southeast Region forum.

ATL is way too far for me, for what it's worth. I haven't blown this thing up in 5 months now, so I intend to keep at it myself unless Phil happens to be within 100 miles someday.
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Old 11-21-2005, 07:45 PM   #10
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Quote:
Originally Posted by fragment
When I got my ver8 longblock from Japanstar it had range 8 irridiums in it.
Interesting.
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Old 11-22-2005, 07:43 AM   #11
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Quote:
Originally Posted by bboy
I've got a theory for you, mind you it's really out there.

Putting in a colder plug transferred more heat to the heads (valves in particular), the heated valves expanded more (lengthened) and closed the lash of the bucket-camshaft interface. Tighter lash meant quieter buckets and less false knock.

Please attack at will.
That's definitely thinking outside the box. Unfortunately, I have no opinion unless I have an idea how EGT and fuel were affected. When I've used a colder plug in the past in search of the tuning sweet spot, I had to make global changes to my fuel.

BTW, if the engine is 9:1 (and I'd believe Quirt), you're not only igniting a more efficient charge, it will run leaner than the same map on a 8:1 engine, and consequently make more noise.And power. What is the PN on your coilpacks?

S.
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Old 11-22-2005, 10:04 AM   #12
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1. Is this still the same rough map for the PE1820 turbo, or have you done changes or auto-tuning at all?

2. What is the AFR at knocking events?

3. Have you tried other gas instead of Sunoco?

4. Have you tried other plugs instead of NGK Iridiums? (IK22, IK24, etc)

5. What is your knock threshold map showing below 2400?
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Old 11-22-2005, 11:01 AM   #13
jblaine
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1. I've done GOBS of tuning. The fuel map I have built is for my setup.

2. Extensive testing at various AFRs, boost levels, and timing. No change to knock voltage magnitudes.

3. Sure, 93 octane Mobil.

4. As mentioned, yeah. I tried NGK copper heat range 7 as well.

5. I think this will answer your intended question: A free rev from 0-6500, sent to Phil, resulted in "Those are high voltages for a free rev." I'd have to dig around in a pile of logs to get your exact answer, as I don't really do WOT pulls from below 2400 in 4th gear...
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Old 11-22-2005, 12:13 PM   #14
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won't running at wastegate boost levels also allow you to build a noise curve? Assuming 7 - 10 psi, on 94 octane you shouldn't have any real knock...
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Old 11-22-2005, 12:14 PM   #15
Element Tuning
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Quote:
Originally Posted by n2xlr8n

BTW, if the engine is 9:1 (and I'd believe Quirt), you're not only igniting a more efficient charge, it will run leaner than the same map on a 8:1 engine, and consequently make more noise.And power. What is the PN on your coilpacks?

S.
You're on the same page as me here in regards to compression, power and noise. As you make more power noise tends to increase, this is why a simple "free rev" to establish a knock threshold map isn't sufficient but it does help establish the base noise level of a particular engine.

Also keep in mind higher compression generally leads to higher in cylinder temps. I'm not implying the colder plugs are incorrect so let's here more opinions.

Phil
www.elementtuning.com
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Old 11-22-2005, 12:59 PM   #16
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S. thanks for being polite

The point is that jblaine changed his plugs from 7 to 8 heat range and knock noise dropped by more than half--his compression did not change. Colder plug-->less noise.

Are you arguing that jblaine has lost power by moving to one step colder plugs and therefore the engine is less noisy?
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Old 11-22-2005, 04:37 PM   #17
jblaine
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Quote:
Originally Posted by n2xlr8n
What is the PN on your coilpacks?

S.
I have no idea. You're welcome to come look I'll try to remember to check one out the next time I'm pulling it. They're stock 2002 WRX coil packs.
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Old 11-22-2005, 04:43 PM   #18
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Quote:
Originally Posted by fragment
won't running at wastegate boost levels also allow you to build a noise curve? Assuming 7 - 10 psi, on 94 octane you shouldn't have any real knock...
Yeah, it will allow you to build "a noise curve".

I doubt it will be real useful when you're making a crapload bigger bang at 16+psi though. It's just gonna light up your knock meter of choice like a christmas tree.
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Old 11-22-2005, 08:55 PM   #19
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For the sake of moving things along I’ll share a few bits of information.

1) The heat range of a spark plug rarely has an impact on detonation. For this to happen, the spark plug heat range would have to be so far off that the insulator becomes hot enough to ignite the air/fuel mixture. If this was happening the spark plug insulators would show clear signs of overheating.
2) The heat range of a spark plug has no effect on spark energy given the correct application. You simply select a spark plug hot enough to keep the insulator clean of deposits to prevent the spark plug from fouling. Obviously if the spark plug is fouling out spark energy will be reduced.
3) Spark plugs do not add any heat to the combustion process. A hotter plug will retain more heat in the combustion chamber while a colder plug will transfer that heat faster into the spark plug and the heads.

Could Bboy be on to something in regards to heat transfer into the heads? It’s really far fetched and highly unlikely but I did have to think about it for a second

The hotter the burn the higher the combustion temperatures the higher the HP will be. Remember heat is energy and the less heat you transfer from the combustion process into the spark plugs, heads, and piston the greater the energy available to create power. I believe n2xlr8n was alluding to something along these lines.

As more power is made noise tends to increase as you have everything moving in the engine faster, hitting harder, and with more force. My knock threshold map is significantly different at 400 whp on pump fuel vs. 550 whp on race gas. Unfortunately sometimes knock can happen within the window of normal engine noise if the power is high enough or if the engine is “noisy” enough. The highest level of power comes from riding the cusp on detonation and with a good engine and engine management you can ride this line successfully.

Now, the million dollar question is did you reduce power with the colder spark plugs and therefore engine noise was reduced or did you reduce some low level detonation with a colder spark plug due to controlling the temperature of the insulator? Unfortunately that answer will be in the dyno plot when you put your car on the dyno and test it

Thanks,
Phil
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Old 11-22-2005, 09:29 PM   #20
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I guess the next question is: Can 1-step colder plugs reduce power output enough to significantly reduce engine noise?
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Old 11-23-2005, 01:31 AM   #21
jblaine
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Quote:
Originally Posted by Element Tuning
Now, the million dollar question is did you reduce power with the colder spark plugs and therefore engine noise was reduced or did you reduce some low level detonation with a colder spark plug due to controlling the temperature of the insulator? Unfortunately that answer will be in the dyno plot when you put your car on the dyno and test it

Thanks,
Phil
www.elementtuning.com
Thanks Phil. That makes sense.

Given a total lack of change in original (high) knock threshold levels when going from 93 to GT100 on the hr7 plugs, I would have to say the former -- reduced power going to hr8, and they're likely unnecessary.

This is where you say, "Well if you experienced that lack of voltage change, why did you put hr8 plugs in?" Because? I'm paranoid? I don't know.

As an aside, having seen my buddy's hr7 plugs from his "TXS Stage 4 WRX"-like setup, they seem pretty unnecessary there.
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Old 11-23-2005, 01:37 AM   #22
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FWIW, I tuned the GT100 map to 11.6:1 and 20.8psi from 3800-6000 yesterday and tonight with nothing outside my new knock threshold curve. EGTs were 1600F at 6800RPM. Ran fine, sounded fine.
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Old 11-23-2005, 09:56 AM   #23
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Quote:
Originally Posted by jblaine
FWIW, I tuned the GT100 map to 11.6:1 and 20.8psi from 3800-6000 yesterday and tonight with nothing outside my new knock threshold curve. EGTs were 1600F at 6800RPM. Ran fine, sounded fine.
I have a few customers that have issues running colder plugs on the STI engine so they appear to be more sensitive than your combination due to the lower compression. You know if it gives you piece of mind and you're not experiencing cold start or cold running issue then go with it.

I still use heat range 6 plugs on my car and have done so approaching 700 whp. With a drag turbo I make around 600 whp and have sprayed a 70 shot of N20 on top of that. So far I have not felt the need to go with a colder plug on the STI application for normal street use or drag racing.

Once I get the Time Attack car back from California I'll check the insulators for any over heating since the car was used for extended periods at high rpm and very high egts. For road racing a colder plug may be beneficial if there are signs of over heating the insulator.

Thanks,
Phil
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Old 11-23-2005, 12:18 PM   #24
jblaine
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Quote:
You know if it gives you piece of mind and you're not experiencing cold start or cold running issue then go with it.
I'll likely leave them in for a few thousand miles if only for being sick of screwing with it There are no cold start/running issues so far, but then again I live in Florida. Cold is 55F.
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Old 11-23-2005, 01:28 PM   #25
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Now I see you are two steps away from the recommended stock plug. I could see that causing a reduction in power. If those plugs stay in your engine for long, it will be interesting to see if they foul quickly, cause misfires, etc.

It's hard to compare heat ratings between plug manufacturers; they are not the same.

I'm with Phil on using the stock heat range. Unless your car is for track use only, where you are running it hard most of the time, colder plugs will just not do anything for you in a detonation reduction sense.
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