Civicman86

Ok well I was just thinking and had a question. Thought it might strike up some good tech talk in the FI section.

I know most hondas can usually tune for MBT when tuning the ignition (Max torque comes before detonation, in general, correct?). If that is true, what do you do with cars that detonate before MBT? Do you have to use detcans or the like, or is there some other method that people use?

** I know this isnt really honda baed but I was just curious**

.dave

Put in higher octane fuel.

tony1

Spark plugs will give you a very good indication of what's going on in the cylinder...

Blaze45

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Spark plugs will give you a very good indication of what's going on in the cylinder...</TD></TR></TABLE>

This is very ture, but since most people such as myself dont get to tune cars and look @ plugs very often other then our own setup, care to divulge some key things we should look for when tuning? If not, its totally understandable.

Finland

You could also raise the detonation threshold by ensuring the coolest possible intake charge.

JDogg

if you detonate before max tq is reached hten turn down the boost or use higher octane gas.

david@didrace.com

You also have to determine which cylinder(s) is/are detonating and why (faulty injector, etc.).

Civicman86

So my next questiin is why would a motor "act" this way? Is it usually the very high compression motors that would have this problem? Or does the design (eg. quench design) also play a big role in this. Seems like when the engineers are developing a motor they would want it to be able to reach MBT without detonation being a problem. Am I maybe missing something?

ekslax

from what ive read on pgmfi.org, they say if you have a pepper like spots on the spark plugs (white ceramic) then you should back the timing off a few degrees

david@didrace.com

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Civicman86 &raquo;</TD></TR><TR><TD CLASS="quote">So my next questiin is why would a motor "act" this way? Is it usually the very high compression motors that would have this problem? Or does the design (eg. quench design) also play a big role in this. Seems like when the engineers are developing a motor they would want it to be able to reach MBT without detonation being a problem. Am I maybe missing something?</TD></TR></TABLE>

With enough boost any motor on a given octane is knock limited.

Tony the Tiger

Horspower (or torque) vs engine displacement vs compression ratio vs octane is the most basic guideline to follow to determine the detonation limit of a certain setup. Engine redline is just as important because a lower redline engine always make more torque vs the same HP.

Quench/head design, heat (ie: intercooler, radiator, etc), volumetric efficiency (small vs large turbo, cams, etc), would be the next series of things to look at.

There is also how consistent the engine runs. That would be difference between cylinders, from equal fuel delivery, to equal air delivery (intake manifold design), timing for diffferent cylinders running in different conditions (ie: cyl #3 on a Honda runs hotter due to various reasons such as lesser surface area to water jackets, etc).

As for how to look for signs for detonation, this is stricky all about experience. You need to blow up a few motors before you know what's really knocking

non-VTEC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">
You need to blow up a few motors before you know what's really knocking </TD></TR></TABLE>

gonna have to agree with tony on this one.....although i went through a motor mainly due to detonation but it was not noticeable on the plugs nor was it audible under load and it never showed up on the dyno.......

detonation can be a tricky bastard......

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by non-VTEC &raquo;</TD></TR><TR><TD CLASS="quote">gonna have to agree with tony on this one.....although i went through a motor mainly due to detonation but it was not noticeable on the plugs nor was it audible under load and it never showed up on the dyno.......

detonation can be a tricky bastard...... </TD></TR></TABLE>
why do you know it detonated if it didn't show up on the plugs? Maybe you just got a bad tank of gas one day

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">
why do you know it detonated if it didn't show up on the plugs? Maybe you just got a bad tank of gas one day </TD></TR></TABLE>

Probably because it showed on on the pistons and chambers when the motor was dissassembled?

Muckman

iTrader: (2)

I agree, detonation can be very tricky to diagnose. Everyone knows what severe detonation sounds like (or at least you should) and its very obvious when it occurs. But what Im having trouble with is slight detonation - the silent, slow killer.

Knock sensor not logging anything (not even spikes), nothing audible (not even from a det can), EGTs are not high either (&lt;1500*F) and I never saw anything that resembled "peper" on the spark plugs. I thought I had a good safe tune. I had some bearing issues and when I pulled the pistons, I noticed my ceramic coating on the piston was worn off around the intake side (the hot side). Evidence of detonation. WTF?

JDogg

just remember, that detonation and pre-ignition are 2 very different things. pre ignition occurs before hte spark plug sparks, detonation occurs after the spark plug sparks.

0xenocron

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">just remember, that detonation and pre-ignition are 2 very different things. pre ignition occurs before hte spark plug sparks, detonation occurs after the spark plug sparks. </TD></TR></TABLE>

Your motor can last for a while through slight detonation though and with 2 maybe three cycles of actual pre-ignition you're done.

Pre-ignition can be caused by consistant detonation as well, but not always.

I am a big advocate of reading plugs.

here is a nice link:
http://www.motorcycle.com/mo/mcrob/rt-fuel2.html

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">Knock sensor not logging anything (not even spikes), nothing audible (not even from a det can), EGTs are not high either (&lt;1500*F) and I never saw anything that resembled "peper" on the spark plugs. I thought I had a good safe tune. I had some bearing issues and when I pulled the pistons, I noticed my ceramic coating on the piston was worn off around the intake side (the hot side). Evidence of detonation. WTF?</TD></TR></TABLE>

From what I remember from EFI101, EGTs will go down slightly just before MBT and then SHOOT up after, especially if you are detonating.

I think Water Injection is a starting to become a more popular method of detonation prevention as well. Cheap and easy too

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">Probably because it showed on on the pistons and chambers when the motor was dissassembled?</TD></TR></TABLE>
I would think this would have showed up on his plugs though. If you have pits in the combustion chamber and on pistons i would think that some of those missing pieces of piston are gonna show up on the plugs as shiny specs.

0xenocron

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">
I would think this would have showed up on his plugs though. If you have pits in the combustion chamber and on pistons i would think that some of those missing pieces of piston are gonna show up on the plugs as shiny specs. </TD></TR></TABLE>

Probably depends on where in the cylinder space the detonation event begins...

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xenocron &raquo;</TD></TR><TR><TD CLASS="quote">

Probably depends on where in the cylinder space the detonation event begins...</TD></TR></TABLE>
well that would be a bitch . Reading plugs AND using some kind of det cans/knock sensor equipment must be the only way to be sure you have no knock.

xsi-t

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">
well that would be a bitch . Reading plugs AND using some kind of det cans/knock sensor equipment must be the only way to be sure you have no knock.</TD></TR></TABLE>

That and not leaving an extra degree or two in just for 4whp - 8whp

Muckman

iTrader: (2)

I agree with that. Being overly conservative with ignition is going to result in higher EGTs but at least you wont destroy your pistons. Consider it full time anti-lag lol.

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">I agree with that. Being overly conservative with ignition is going to result in higher EGTs but at least you wont destroy your pistons. Consider it full time anti-lag lol.</TD></TR></TABLE>

Our hondas don't have it so bad with conservative timing, but most of the lower CR turbo motors still go through valves, burn up turbine wheels, etc... with conservative ignition timing.

Mild detonation can be seen on the plugs over time, but more serious detonation can trash a motor within a few pulls. Sometimes it's not even visible on the plugs because a few pressure spikes from detonation was enough to crack the ringlands or punch a hole through the pistons.

It can be really tricky... Even if an engine was detonating, it doesn't mean it was happening all the time. The engine could run great for a few pulls on the dyno and a few track days; but when conditions get demanding with 5-6 consecutive 5th gear pulls, a hardcore roadracing event, etc... with some heatsoak (fuel heatsoak, IC heatsoak, etc..), detonation begins to happen. The motor blows up at that certain time frame although it could be running fine for years already.

Generally, there is much more then just mapping the ECU for tuning. You also have to understand the setup and know when to be really cautious just by looking at the power level, octane, engine, etc... If someone was to bring me a 11.5:1 CR Dodge SRT-4 engine, I'll tell him to run race gas all day long, whereas if a Honda came in, I know it's doable at a certain power level on pump gas. Experience really counts when it comes to safe tuning. All the tools like det cans, reading plugs, knock sensors, etc.. only gives you a rough idea on how the engine is running.

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xsi-t &raquo;</TD></TR><TR><TD CLASS="quote">

That and not leaving an extra degree or two in just for 4whp - 8whp</TD></TR></TABLE>

That's the easy part... If you are tuning a motor that is detonation-limited on pump gas, how will you know when to leave an extra degree or two? You have to find out whether the motor is detonating or not beforehand, before you can leave that extra buffer room. That's what we are all trying to discuss here...

non-VTEC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">

Probably because it showed on on the pistons and chambers when the motor was dissassembled?</TD></TR></TABLE>



even though the pistons look like that i had 2 or 3 techs/mechanics check out my plugs right after a few pulls and the plugs always looked good.....and even the dyno graphs looked smooth.....you would not suspect there to be detonation but the cylinders/pistons tell a different story.......a bad tank of gas is possible...i live in toronto and they fuel we have here is terrible.......oh well.........hopefully i wont crap out my current motor completely although it is making noises again