annointed

I have an Apexi Power FC stand alone engine management system, and I'm adjusting the Ignition timing settings, as they are very aggressive from the factory (it came tuned for my car, supposedly). It has a knock sensor readout on the handheld controller, a bar that stretches to the right when any detonation is detected. Small bar = no detonation, long bar = mucho detonation. I can also shift to a 10 sec graph that shows detonation as spikes, but I prefer the bar readout.

Anyway, the first night I had it, I heard audible detonation several times under load/heavy acceleration, and the knock gauge/readout bar was over an inch long. For those running Links, that probably corresponds to 200+ units. I know some amount of detonation is acceptable, ie, for Link tuners, generally under 100 units...I was actually surpised to learn that so much silent knock might be acceptable...Can anybody tell me how much/little detonation is acceptable?

Based on the Link example that I gleaned from a search, I would logically assume that I can safely allow maybe a half inch long knock bar/spike to light up (as audible detonation was about 1.25 inch long bar/spike). I feel strange tolerating any detonation whatsoever, so I want the advice of more experienced tuners.

Thanks,

Mark

Pete Croney

Mark

Go with your instinct. NONE is acceptable.

Pete Croney

I should add that we also got loads of det when we first ran the default map.

Gez

Speak to Clive at RC Developments. He has mapped the power FC for the RC Demo Car. He also use to work for DP motorsport who are the UK agents for all the APEXi gear. Phone no is 01606786706.

Regards

Gez

annointed

Thank you gentlemen...and I'll give them a call today, Gez.

Sam Elassar

i think you are confusing two completely different things here!

there is a big difference between det and engine noise your engine noise can be value and it depends on your car. det can be recoginsed by spikes in the engine noise if that makes sense.

also engine noise is rpm dependant. so lets say your engine noise should be 20-30 ( link example here) at 2000rpm maybe slightly more at 4000rpm but it could reach 80-90 by the time you are revving to 7000rpm. that is still not det. det is when you engine noise goes from 0 to 60 around 4000revs for example but again it is still not 100% correct and can get it wrong sometimes.

i hope that makes sense i am sure a lot of poeple will reply and maybe explain things better than me.


sam

RT

Yes, apparently one of the black arts of engine tuning is separating the engine noise from true det.

Also, I've heard that forged pistons create a lot more background noise than cast pistons. Don't know how true this is and why it is so. Can anyone explain?

Cosie Convert

Forged pistons have a higher thermal expansion coefficient than cast pistons, that means that the bore clearance when cold is greater on forged pistons. There will therefore be a bit more noise from forged pistons until they are fully up to temperature.

As far as I am aware

annointed

Sam, you hit the nail on the head. On Thursday I detuned the timing to the point that, at >50% throttle it was noticably retarded, and yet, it had the same amount of what I was calling silent "detonation" above! At that point, I decided I was simply experiencing engine noise, and promptly (and quite happily) advanced the timing again! (as high as 44 degrees in some spots!). The car is once again happy, and extremely quick, and the knock readout is still just showing the same engine noise, of course, there is more at higher RPM's but its easily within a safe zone, and waaaaaaay short of the level that I saw the first night with the car when it was clearly pinging.

Interesting discussion about the forged internals, too =)

Sam Elassar

hi

Mapping your power fc may not be very difficult however you do sound like you have not really done this before and this worries me i hope that i am wrong. knock control via your power fc or even with the link is not really the most accurate way of checking for knock however it is very safe way of doing things.

although i am not an expert i have not heard of silent knock before? it is kind of contradiction of terms on it is own right. the reason probably not that many people have you responded to this is every one is probably worried you will end up blowing your engine if you misinterpret/use the advise you get over here.


Engine noise is acceptable, and it should be a gradual raise in your knock sensor activity. it is RPM related and also gear related. it usually higher in the higher rpms and in higher gears.

Knock happens when the mixtures inside the combustion camber burn an uncontrolled manner. This can produce various engine noises (knock), what I know of is pinking, knock and pre ignition.

Pinking, is the most common, it is produces a light metallic clinking noises and is cause by the ignition being too far advanced. Basically because of the too much advance the pressure rise in the cylinder occurs too eary and the piston rattles against the bore as it goes over the TDC. Although it is not an engine breaker at light loads and low speed it causes you too loose power so you would need to get rid of it anyway.

The second on is knock, it produces much heavier noise than pinking and it is because of the gases in the combustion chamber under certain condition colliding. This depends on the mixture ratio, spark plugs, ignition advance, shape of the combustion chamber, and also on the quality of the fuel and the ability of the fuel to resist knock. So it will be car specific to a certain extent. This will usually happen at the point of highest torque ie in a Subaru engine maybe between 3500-4500 rpm. Basically when you floor it between gears.

The third one is detonation, this happens at high rpm and on full load. This when the fuel mixture start to burn before the spark arrives. Caused by something in the combustion chamber getting to hot and igniting the fuel. Again this is cause by the ignition timing being too far advanced, among other things like weak mixtures (too lean), wrong choice of spark plugs. Water injection will help here. This will cause you to blow your engine and is very serious!!!!!!!!!!!!!!!

I have noticed that the Subaru runs very rich as standard but it also runs quite a lot of ignition advance as standard. Maybe it runs rich to cool the combustion chamber and combat detonation?

So be very careful. With what you are doing and look for things. Mainly spikes in your engine noises are not really wanted. The best thing to do though is to make your self a set of det cans or buy them from some where and listen to knock your self. You ears and brain will be able to interpret knock my better than you ecu, as you can differentiate what is knock. pinking. det better than the ecu. All the ecu reads is noise that could be anything.


sam
ps guess who is bored on saturday night

Sam Elassar

when i read your first post, what you are suffering could well be the second one i have mentioned, ie knock which happens under acceleration. you need to retart the timing in that area. i had a subaru for 2.5 years and i only heard the car knock inside the car once!!!!!!!!!!!!!!!!!
i usually done it using the knock link and the link ecu. so i had two knock sensors to check for knock.

unfortunately, having an ecu and raising the boost may not give you all the power that you need you may need to tune it further so join the club. just because it is not as quick as you want it does not mean to increase the advance until you loose the engine! just need to get a bigger turbo or something


you have not said what fuel octane do you run your car on?

one question about the power fc though. did your car start straight away with it? and how is your cold and warm starts settings as standard ?

sam

[Edited by Sam Elassar - 4/20/2002 10:34:53 PM]

annointed

Sam, I have never heard anyone claim there is a differnce between knock, detonation, and pinging (what you call "pinking") until your post just now, but maybe I'm just getting introduced to last week.

Anyway, I'm not too worried. In addition to the Power FC, I am running a ported TD05-16G with a 3" Rallispec turbo back, and AVC-R boost controller set at 1 bar (14.5 psi). The engine and driveline is just a jspec '94 WRX, so internals are not STi quality. That first night I was running 93 MON, which is 97-98 RON, so after several audible detonation events, I carefully drove out that tank of gas, filled it with Sunoco Ultra 94 (99 RON), and took it to Rallispec for tuning. They pulled back the timing under load, and with the Ultra 94+GTA fuel enhancer, all has been well ever since. The stock WRX clutch is slipping under the ~300 ft-lbs, so as soon as my ACT clutch and lightened flywheel are installed, I'm getting it dyno tuned as well.

So I'm not worried, as all I was doing was taking the Rallispec tuning, and further pulling back the timing, but I quickly realized that no matter how much I retarded the timing, a small amount of engine noise is ever-present. This is my first experience with a knock sensor readout, so this was a revelation to me. I look forward to the dyno tuning as well, when fuel maps will also be modded if necc.

Anyhow, at higher RPMs, especially in 3rd and 4th, there is a little more engine noise than down low. Upon further reading, I realized this was normal, and (surprise!) that Rallispec knows what they are doing, so I returned the Ignition settings back to where they left them, except that I slightly pulled the low load/high RPM timing, which they had left untouched.

Doesn't sound too risky to me. My main concern right now is not ignition timing, but rather how far I can safely push the stock injectors. I'm running a Supra TT fuel pump, but the injectors are 370-380 cc, as best I can tell, so 300 hp is probably maxing them out...tempting to upgrade them right now, just to be on the safe side, and since my next stage of upgrades requires me to go with 550+ cc injectors anyway...

But, enough rambling. Thanks again for your feedback.

Mark

Cosie Convert

Sam, You know me, I hate to disagree with you but..... as far as I'm aware there are only 2 types of knock - 1 as you said pinking. Points 2 and 3 I would say are the same thing although they sound different at 3000 rpm than 6000 rpm. The gas shock waves only collide because of the secondary point of ignition, which as you point out may have a number of reason for happening.

I think your second and third descriptions combine to give the reasons for the uncontrolled Detonation of the charge causing Knock.

Sam Elassar

cc
well 2 out of 3 is not bad that is a pass right . it just terminlogy

mark
it is very difficult to judge from someone post what is the level of their knowledge. so sorry if i bored you too much.

as for pinking/ pinging ( potatos/ potatos ) knock and det this is according to some of the books that i have read and it made sence to me. so the terminlogy may differ with tuners.

engine noise should be constant and should not really get any less with you reducing he ignition. ifyou reduce the timing and you start getting less or no spiks then you could have been knocking and reducing the timing has cured it.

it is all very difficult to comment as i have not really seen the power fc on a subaru before. i have seen them on skylines and they looked feature loaded. i am even considering it for my evo7 !


what i know is with a knocklink fitted to properly tuned car you should not get any activity or spikes on the tuning module. first two greens is as much as you get really. when i fitted the knocklink to my evo all i get is the bottom green flickering ( only sometime) when floored apart from that it is very clean even hitting the rev limiter.


did porting your standard td05 16g make a noticable difference?

sam

[Edited by Sam Elassar - 4/20/2002 11:22:58 PM]

annointed

I'll just chalk up the "pinging/pinking" term issue to a UK/USA thing...kinda like hood/bonnet and other terms I've run into

Anyway, I appreciate your words of caution. It doesn't take much detonation to do in an engine, especially when it's audible detonation like I had that first night with the car. Since Rallispec tuned the FC, all I have is engine noise, which I feared might be "small-scale detonation," so to speak, even though it is 10-15% of the magnitude of the detonation I previously experienced. I've looked at many people's datalogged charts this week, and based on them, I'm sure what I see on my knock display is the normal baseline engine noise that one can expect, and if an expert tuner like Rallispec saw no problem with it, I shouldn't either.

Unfortunately, I never got to drive the TD05 in stock form. The WRX front clip I got came with a TD04, so I imported a TD05-16G from Possum Bourne and had it ported before being put on the car. All I know is it comes on strong and would gladly pull way past the 7k reline if I let it. No sign of boost taper whatsoever. Eventually I'll upgrade the compressor wheel, but for the time being, it suits me quite fine.

I am still curious about the Injectors. I was not going to upgrade them until I do my next stage and move from a 300 hp set-up to a ~400 hp one, which will involve completely upgrading internals. I'm told my stock injectors can handle up to 300 hp, I just feel like I'm not giving them any breathing room by running 8 year old injectors at 95% duty.

Any thoughts are appreciated.

Thanks again fellas

Mark

Cosie Convert

Straying off topic in typical fashion......... Sam, have you come across any prices/results for hybrid TD05's

Andy

Cosie Convert

Mark

I think you will find that at 95% duty, your injectors are not closing. this is due to the 'off' time interval being too short to allow the valve to close and open again.

If you do the maths, at 6000 rpm, 2 revs of the engine (1 cycle) takes 20 ms if you run 95% open then 5% closed = 1ms ! it aint going to happen !

A practical limit for full control is 85% IDC. At 6k rpm this allows 3 ms to close and re-open.
I don't think it's a big issue maxing out injectors, my engine relys on this ! (same inj as you) The purists hate it because you effectively get a step change in fueling between 85 and 100 % depending on RPM as they hang open. In my experience this causes no harm to the injector.

Monitor your exhaust gas mixture sensor output to confirm adequate fuel supply, a double check can be made by monitoring EGT.

Have you tried an adjustable fuel pressure regulator ? If you are running a big pump then you can get another 15% or so flow at higher pressure.

Andy

[Edited by Cosie Convert - 4/21/2002 12:04:58 AM]

annointed

Hybrid TD05's??? Are we talking beyond the normal big 16, or 18G compressor upgrades?

Sounds like a conversation I want to hear! I'll be listening...

annointed

My a/f gauge is a 0-1 Volt, 20 LED gauge, but I'm sending it in to be recalibrated to display .78-.98, as this should give me a better idea of fuel mixture at WOT...

I just wanted reassurance that I don't need to fear that an 8 year old injector will crap out on me for running it ragged!

Cosie Convert

No worries I run mine up to 26 psi !

annointed

26 psi
^
|
|
HOLY CRAP! Must be nice having RA internals!

[Edited by annointed - 4/21/2002 12:30:55 AM]

Cosie Convert

Not so sure that RA internals are so special ? Supposedly stronger block but otherwise same as your WRX

annointed

Careful, the last thing I need is encouragement to run 26 psi!

Cosie Convert

11.87 @ 115 mph 1/4................You know you want it

annointed

Yeah, I've been reading your posts on iclub, lol. But every time I look at that 11.whatever at 115 I go

I'll be there eventually!

Cosie Convert

You'll make it before the overweight 02 'uglys' do, that's for sure !!

annointed

Amen to that! Gotta love GC8, grrrrrrrrr!

Well, I'm off to the beach now! water is just warm enough to play...and show off the Scooby!

Sam Elassar

hi andy

no results but there is few companies in the states that will do an upgrade for the TD05 series, you can get td05 20g for the evo 1-3 so i am not sure if they can do the same for the subaru.

in here turbo dynamic do a conversion for £900 exchange basis !!!!!. they do few conversions around the same price 430bhp and 450bhp i think if i remember correctly.


sam

annointed

900 pounds!!!

There are many places here in the States that will do Mitsubishi turbo upgrades. Rallispec told me they have several reliable people who can upgrade my TD05-16G to a big 16 or an 18G for $400-500. They were not sure if a 20G will fit in a TD05 housing. The only 20G's I've seen have been in DSM's, and they all had TD06 housings.

john banks

I was going to say that if you run your injectors wide open (beyond the point of no return ) you depend entirely on fuel pressure for your fuelling with no room for correction. However if you ran an 80% IDC you would as well since we are only dealing with open loop fuelling, so there are no corrections - it is a blind process fuelling based on MAF voltage, RPM and load. So apart from the step at the magical point of no return, we only have the theoretical issue of them overheating or sticking open. Presumably in an injector's spec there is a quoted MTBF based on a more "normal" IDC?

With regard to knock/detonation, do any of us know how JECS or the aftermarket ECUs detect detonation? The gold standard as I understand it is a DSP system using individual knock sensors for each cyclinder - fed into something like a TI 320C25 series. This has integrated signal conditioning and a DSP which not only uses discrete Fourier transforms but has a superior signal to noise ratio and uses multiple harmonics to detect knock with vastly improved specificity and sensitivity over conventional systems. The Knocklink (being a simple analogue filter which is crankshaft angle time compensated) or the devices in many aftermarket ECUs (Pectel being a noteworthy exception) are poor relations in comparison with overall less processing power for the whole ECU than DSPs like the TI device.

Since most cars have more cylinders than we have ears and a uC/DSP has far greater computational power for signal processing than even "experienced" ears using det cans, should a solution like this be considered gold standard?

http://www-s.ti.com/sc/psheets/spra039/spra039.pdf
http://www.google.com/search?q=knock...r+tms320&hl=en
http://www.icspat.com/papers/4mfi.pdf

So back to the topic - the only answer can depend on the system your Power FC uses to detect but more importantly process the "knock" signals.