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PostPosted: Thu Jan 29, 2015 2:45 pm 
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I get some disturbing knock readings from my FC commander.
When reving the engine in neutral it reads as high as 35-40.
When boosting it trough 2, 3 or 4th it gives a spike of 55-65 when around 4500-5000rpm.
I cannot hear any noise resembling knock, but i am unsure if this is possible to hear.
I tried retarding the ignition timing 3 degrees, but knock levels remain unchanged..... If this really was detonation would it not be reduced with retarded timing?
Engine mods are larger turbo, sport exhaust/downpipe/airfilter.
(I`m not sure if the car really has been dynoed. according to previous owner it has)

I also reach 100% injection duty, but this occurs after the knock spike.
Will this damage my injectors?
I hope this will go away when I change the fuel filter.


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PostPosted: Thu Jan 29, 2015 7:46 pm 
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I would check to see whether it's had a non standard knock sensor fitted. The standard one is tuned to the knock frequency emitted by the engine, generic ones are broadband so will just pick up engine noise in general.

If retarding the ignition makes no difference, then it probably isn't knock you're reading.

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PostPosted: Fri Jan 30, 2015 12:06 am 
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I've always understood that the Apexi PFC 'knock' readings are not a real indication of true knock. They are no substitute for det cans or a fully fledged gated and filtered knock sensing system. I am surprised that you are seeing 100% duty on the injectors. Given the mods you have I wouldn't have thought you'd be anywhere near that level. General rule of thumb is that if the injectors are running more that 85% then it's time to upgrade your fueling system.

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PostPosted: Fri Jan 30, 2015 8:33 pm 
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Location: Tromsø
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I`ve been looking closer at the knocking, and it indicates 20-30 through the gears at almost zero load and low revs.
Makes no sense really.
And I get knock readings as high as 15 when rolling down a hill in gear with zero fuel going in.
So im going to turn off the knock warning light and forget its there.

The injectors are at 100% when boost reaches 1,2 bar, max is 1,35
Should the injectors be able to support that? Or is it overfueling because of bad mapping maybe?
The filter has been ordered and should be here in a few days. Would a clogged filter reduce fuelpressure and injector capacity?

The cars also feels a bit jerky when load is under 5%. It got alot worse after i changed the sparkplugs and oil last week. All is well with the leads and the distributor I think. I replaced all of it 30000km ago. When its idling it sounds like it skips a beat here and there, more like a sparkproblem than injectorproblem. Or could a faulty injector cause symptoms like this? It feels like the whole engine drops in power just for a millisec, almost like it looses a cylinder briefly. Really annoying. Changing to stock ecu made no difference.


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PostPosted: Wed Feb 04, 2015 9:28 am 
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Ive been told that apexi uses knock as a scale so you will pick up varied readings along a drive. Once it starts to read over 60 then that tends to indicate that its knocking.

Ive done tests and had readings at 50 and still not heard any knock.

My gt4 runs like the way you describe yours. Has general driving readings of 20 up to 40 sometimes then will have little moments where it shoots up to 60 odd.

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PostPosted: Wed Feb 04, 2015 12:08 pm 
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Jon9985 wrote:
Ive been told that apexi uses knock as a scale so you will pick up varied readings along a drive. Once it starts to read over 60 then that tends to indicate that its knocking.

Ive done tests and had readings at 50 and still not heard any knock.

My gt4 runs like the way you describe yours. Has general driving readings of 20 up to 40 sometimes then will have little moments where it shoots up to 60 odd.


Yes that sounds like its the same.
Have never been over 70. And when over 50 it only occurs in brief spikes.
I got to talk to the guy who tuned it, he said it was maybe a bit high, but nothing that will damage the engine.

Regarding my Injector max duty problem
My car has been mapped to 1,3 on original turbo. Now its fitted a stage 3 fensport st185) turbo.
And the boost control is out of operation for some reason, so the pressure exceeds 1,3.
Have to turn the boost down or the injectors cant keep up.
I hope this solves the problem.


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PostPosted: Fri Feb 06, 2015 10:10 am 
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The Toyota knock sensor is tuned to the engine specific knock frequency as nibbles said. There are however still engine mechanical noises generated in the same frequency band so the knock reading can be generated just by engine noise. The idea is that you set the warning threshold at the maximum measured engine noise (typically 20-40 but can be as high as 50-60 under certain circumstance or worn engines).

Rather than remove the knock warning altogether just increase the warning level to 65-70 if you are sure you are just measuring engine mechanical noise. You will still retain a warning that way in the event you get bad knock.

Your turbo boost control issues sound like the dreaded "boost creep" do a search ;-) there is loads of info.

In standard injectors I found that 100% duty cycle was common at high rpm and high boost (over 1.2 bar) but that was at 10.5-11:1 afr. You will probably find most mappers will run rich for safety and at similar afr levels as above.

It is not ideal to run the injectors at 100% duty cycle and a maximum of 80% is suggested to be safe to prevent the injector overheating and seizing. I have never experienced anyone it actually happened to though.

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PostPosted: Sun Feb 08, 2015 2:33 am 
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If the wastegate is not able to keep the pressure down, would it not be possible to simply "dump" the intake pressure using a pressure relief valve set to 1,3 bar??
So the unwanted boost would just be released into the air.


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PostPosted: Sun Feb 08, 2015 3:47 pm 
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The ST205 OEM dump valve downstream of the compressor in the ST205 WTA intercooler is designed to relieve 'excess' boost pressure from the intake side when the throttle plate opening is reduced during gearchanges or off-throttle 'over-run'. It's not designed to function under wide open throttle which is where the boost creep can occur.

Ideally it would be better to get the OEM internal wastegate working effectively with the exhaust manifold and downpipe. I used to have a hybrid CT20b based turbo on my 330bhp ST205 and that required the wastegate housing to be machined and re-contoured to improve the gas flow through the twin port wastegate. I was running an upgraded actuator. Many actuators are sealed but if you use something like a Forge actuator then you can change the internal springs so that it opens at a different boost level. Often you only find this out on the rolling road when you are calibrating or mapping after an engine build. I'd be tempted to upgrade to an actuator like this.

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PostPosted: Sun Feb 08, 2015 8:22 pm 
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I was not thinking of using the dump valve for this, but rather a springloaded "safety-valve" mounted in paralell with the dump valve. http://s284.photobucket.com/user/Kjetil_Gout_Eriksen/media/911d8939-9e54-4c12-a093-3480c93a1149_zpsi81c59s1.png.html?sort=3&o=1

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We use these valves at work and it can be set to open at any given pressure (very accurate). Only thing is I need to be able to regulate the flow when it opens, so it doesnt drop the pressure to much or to little. Can do this with a cone valve mounted on the outlet of the pressure valve. If done right no boost creep could occur. This could not damage the turbo right?

Could do the same thing with a pressure transmitter, a pressure controll instrument and two or three solenoid valves opening in stages. Would probably be better but more expencive. http://s284.photobucket.com/user/Kjetil_Gout_Eriksen/media/a64bc176-85d0-433b-a97b-b4645fb5e70b_zpsqnrh7hxn.png.html?sort=3&o=0

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Offcourse it would be better to divert more trough the wastegate, but its also alot more difficult and very expencive.
Have these valves and instruments laying around work and noone will miss them hehe. So it will be no cost for me.
This could be installed in a couple of hours.

I will try this. Just for fun.
But first I have to get my engine running normal again..


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PostPosted: Sun Feb 08, 2015 9:40 pm 
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Diceman wrote:
Rather than remove the knock warning altogether just increase the warning level to 65-70 if you are sure you are just measuring engine mechanical noise. You will still retain a warning that way in the event you get bad knock.


Can the levels of all warnings be adusted in the commander?
If so I will set it to 70. Thank you

I looked trough the menus on my commander. I cant find the
warning level adjustments for knock.


Last edited by TRDTromsø on Mon Feb 09, 2015 3:18 am, edited 1 time in total.

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PostPosted: Mon Feb 09, 2015 12:25 am 
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I'll be interested to see how this performs!

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1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2012 Van Diemen JL12 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp


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PostPosted: Mon Feb 09, 2015 3:34 am 
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First I need to see if the actator rod is actually moving and engaging the wastegate.

Can I manipulate the actuator to open the wastegate manually?
Maybe best to use my spycam and record movement of the rod While boosting.
If its engaging like it should but cant divert sufficient exhaust, I will try my "boost creep elminator"


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PostPosted: Tue Feb 10, 2015 10:18 pm 
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TRDTromsø wrote:
If the wastegate is not able to keep the pressure down, would it not be possible to simply "dump" the intake pressure using a pressure relief valve set to 1,3 bar??
So the unwanted boost would just be released into the air.


You stand a good chance of 'overspeeding' the turbo causing failure.

The easiest way to test the actuator is to rig up a tyre pump to it (one port blocked, other port pressurised) and check the rod pushes out at the correct pressure. The force required is greater than can be easily applied by hand.

It's not uncommon for some aftermarket downpipes to foul the wastegate and stop it opening fully (or jamming open, not your symptom in this case). Some also tend to shroud the wastegate a bit reducing flow through it.

The normal bodge is to fit a restriction in the exhaust to reduce turbo efficiency. The correct method is to improve flow through the wastegate - possibly even going for an external wastegate.

Boosting beyond 1.3 would tend to indicate an actual problem though, maybe jammed wastegate, failed actuator, split hose, incorrectly plumbed etc. etc.

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PostPosted: Wed Feb 11, 2015 10:57 am 
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I have seen more than 1.3 bar from actuator only as a result of boost creep ;-(

Otherwise I totally agree with nibbles.

The knock level can be adjusted, it may be a datalogit only setting.

I have a datalogit but no longer have a power fc (or running gt4 lol)

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