A Must Read For Budding Tuners, Or Those Interested In "knock"

[Rolls]

Alcohol burns slower than petrol, it is conceivable that an explosion might be slightly less powerful, or due to there being more fuel it explodes faster/slower.

I'm not sure but it is plausible that it may sound different.

[DVS JEZ]

Same here mbt before knock limit on e85. Sr20 310kw

Gtr 296kw

[HYPED6]

Hey Guys,

Im not on here much, but I just thought I should clear up a few things about tuning E85.

Yes you can hear detonation on e85. detonation is detonation, end of story. The same hi pressure wave still smashes the same piston area in the same way.

The fuel makes no difference. E85 has a huge resistance to uncontrolled burn, this is what indicated the RON rating, not hard hard it is too ignite.

With E85, or any fuel with high knock resistance for that matter is it wont normally ping unless in extreme conditions, so you wont damage pistons as such.

What happens is tuners that over advance there engines hammer top rod bearings. Not by pinging the engine, but by making the high pressure event too early for the engine it self.

There is no ping as such but the physical force still hammers the piston down and literally every power stroke puts more and more ware on the top rod bearing and little ends of the rods.

The lower EGT's with E85 are from the evaporation of the fuel, more specifically the ethanol. The quicker it evaporates, the more heat it dissipates and the more fuel you need to use.

This is a factor in the fuel usage, not the main cause.

Another factor that will influence EGT's are ignition timing. The more timing you put in the lower your EGT's. regardless of fuel.

So if we have an RB26 running -5's on 98 that can say run 26 deg at 8000rpm on 24psi with EGT's of 750 and we add 2 deg, the EGT's may drop 30deg to 720.

The added timing may also cause the engine too ping. The pinging is not the cause of the lower EGT's, its the advanced timing.

I have never seen an EGT fast enough that could detect a knock quicker than the human ear so it doesn't really make sense to use it as knock detection.

Your engine would be dead way before the EGT Sensor has even picked it up.

I have seen engines 16deg over advanced at full noise. I pull the timing out, EGT's go up, but the load on the engine drops massively but still makes the same power.

[GTR_JOEY]

Thanks for clearing that up mate.. Good reply

[Lithium]

Yes you can hear detonation on e85. detonation is detonation' date=' end of story. The same hi pressure wave still smashes the same piston area in the same way.

The fuel makes no difference. E85 has a huge resistance to uncontrolled burn, this is what indicated the RON rating, not hard hard it is too ignite.

With E85, or any fuel with high knock resistance for that matter is it wont normally ping unless in extreme conditions, so you wont damage pistons as such.

What happens is tuners that over advance there engines hammer top rod bearings. Not by pinging the engine, but by making the high pressure event too early for the engine it self.

There is no ping as such but the physical force still hammers the piston down and literally every power stroke puts more and more ware on the top rod bearing and little ends of the rods. [/quote']

Awesome, thanks for the response - thats a lot more like what I would have expected... I couldn't see how detonation would sound substantially different from any other det, let alone unidentifiable. The over-advancing would result in torque loss on the dyno, or at least reaching a maximum torque level... surely?

[HYPED6]

The torque loss is minimal, but it is still there. Unless you are running a super small turbo, and need to over advance your engine for thermal management,

minimum timing for maximum torque is still the best method to use. Provided you are using the correct fuel for the application.

Edited December 24, 2011 by HYPED6

[Lithium]

Excellent... everything you have said so far is pretty much how I expect, so thus far I see no point in changing how I have been doing things, thanks for your input

[STATUS]

I have seen engines 16deg over advanced at full noise. I pull the timing out, EGT's go up, but the load on the engine drops massively but still makes the same power.

yeah we are starting to see more and more over advanced engines come in on e85.... i just dont get it.. E85 is one of the simplest fuels to tune for... that said i will often do a 98 tune first to give myself a decent base / engine charactaristic to work from

[STATUS]

We are in the final stages of testing a dash mounted KNOCK monitor for a company, i will post up all the results once we are satisfied... at this point im wrapped with the results and hope to be finished in a week or two from now.

Pricing will place it sub $150 and will suit ALL cars (tested on 12 differrent engines so far).

This is a consumer product primarily (fit and forget in your car) but could be used for tuning (i still recomend knockbox or kmon for serious tuners as you can use headphones) if wired externally as its a stand alone system and only needs power and earth from the car.

I should add it has 0-5v output too ive got it as a logged input on my dyno atm. So any aftermarket ecu can have it as input to trim timing.

[Lithium]

My curiousity has been piqued

[Elusivity]

Yeah this does sounds good! Trent, will the company or yourself be making recommendation for installation locations for the sensor on different engines?

[STATUS]

Yeah this does sounds good! Trent, will the company or yourself be making recommendation for installation locations for the sensor on different engines?

no need, the setup procedure is very simple and has been designed so a 7 year old could do it...

[skylinecouple]

I've been tuning with the PFC for years now and always use the knock sensor display. How would you say the Nissan knock sensor is in regards to sensitivity ? If I'm aiming for around ten knock, would the standard sensor be too sensitive or is just fine for normal tuning. Bare in mind I've had this car for over ten years now and never blown an engine due to knock. Though I've always suspected I could put a lot more timing into it.

[DVS JEZ]

I have found pfc to be inconsistant. Sometime (mostly) 40 or so is actually pinging.

A GTR i did today was pinging with a knock reading on 19 which means it didnt actually pick up the detonation.

Best to get it checked where possible. But the norm is over 40 is real det

[JonnoHR31]

Yer they're all different. For example myne constantly reads up to ~20 just from normal engine noise cruising around and i often get false readings on limiter of over 100

[t_revz]

We are in the final stages of testing a dash mounted KNOCK monitor for a company, i will post up all the results once we are satisfied... at this point im wrapped with the results and hope to be finished in a week or two from now.

Pricing will place it sub $150 and will suit ALL cars (tested on 12 differrent engines so far).

Sorry if the result was put into a new thread but was this developed and available?

Was thinking about the copper tube with hose to ear muffs trick but this would be better

Also another question about quench pads. If there generally the hottest parts of the chamber(I think) then would their removal make it more Det resistant if CR is the same or would this larger area between piston-head on the edge of the cylinder cause it to be just as Det prone?

[GTSBoy]

Quench pads serve a very important purpose in creating in-chamber turbulence that enhances mixing and SUPRESSES detonation. Their removal or buggering them up by fitting massive head gaskets is not a great idea.

[t_revz]

I'm probably completely wrong but I didn't think from the way I read the original post that a poor mix of fuel/air would make it more prone to Det.

Or would a lean pocket on the cylinder walls be easier to self ignite from pressure rise therefore Det?

If race or big Hp cars remove pads, then on 98ron what would the major changes be to prevent knock if removing them increases the likelihood? Safer timing levels? Reduced CR?

[GTSBoy]

Or would a lean pocket on the cylinder walls be easier to self ignite from pressure rise therefore Det?

Perzactly. Quench pads are perhaps poorly named. What they really are are squish areas. The squish causes the mix to tumble in the chamber, leading to finer mixing, which leads to more even flame propagation and all the goodness that follows. 4 valve heads suffer from an almost complete lack of swirl and only get a limited amount of tumble from the flows coming in through the inlet valves, therefore they need all the help they can get in the way of tumble and turbulence from squish.

I'm no expert on designing or modifying combustion chambers (well, at least in engines, it's exactly what I do in somewhat larger industrial situations), but I would suggest that if big HP engines are having the squish area removed, there is nothing to suggest that that was in fact the best way to get to that power level, and it could be argued that a different approach could have yielded better performance.

[LWO]

I have found pfc to be inconsistant. Sometime (mostly) 40 or so is actually pinging.

A GTR i did today was pinging with a knock reading on 19 which means it didnt actually pick up the detonation.

Best to get it checked where possible. But the norm is over 40 is real det

I found on my gtr apexi djetro on a low load ping read about 20. I occasionally still get over 100 on crank I presume from starter motor mesh? The base ignition map has a lot of low load advance. After some fiddling now I never get more than 12. Reset max timing to no more than 32 (was 48) and varified number with timing light. Bp98 always used.

Edited October 17, 2012 by LWO