Neil S

iTrader: (1)

Following on from Stu's Wideband AFR Meter thread...

What would be considered the most useful parameter to be aware of when gauging how close to the danger zone your engine is?

EGT - Obv. this decreases the further away from the cylinders we come, and is also an average of all 4 pots (If one goes lean then it might not make enough of a difference to alert the driver)

AFR - Susceptible to air leaks between head / manifold / turbo / downpipe... again a combined reading of all cylinders (I dont know how much difference a lazy injector would make to overall AFR )

So, which gives the best indication of a potential problem?

Neil.

ECU Monitor Enthusiast

iTrader: (1)

There is NO guarantee against meltdown !!!

Either is ok but both together will be better.

At the end of the day, by the time you have seen a problem at high boost/rpm
you will have melted a piston.
Assuming you have been watching readouts while driving fast !!

EGT gauges react far too slowly from my experience.

You can melt an engine even when AFR is correct !!!!

Fiecos Dan

i asked the same sort of questions a few months ago,
the answers i got from several well known tuners on here.

max ex temp at mani 925 oC, 875oC at mani
fuelin 11.7-12.2 afr top end 4+5th gear,
12.6 best for power but not very safe on the road,
15.0 best for mpg, but best for cruise 14-14.5:1

Neil S

iTrader: (1)

Hi Simon,

Of course there is no gaurantee, I was just wondering which would give the first indication - I guess you've answered it with the response of the EGT gauges.

One other point is that most electronic gauges have warning levels and/or tell-tales so you may still get some idea of the levels the temps reach prior to a problem. (Not if your gauge takes 5 secs to react though )

Cheers!

Neil.

PS - you have PM

Neil S

iTrader: (1)

Numbers Duly Noted fiesta cossie

Neil.

Shings

Neil

I had both in my escort turbo.
Didn't prevent my engine blowing up- gave very little warning if any as well...

Drove to the pod and all seemed normal although I did feel the car was down on power and 5th run and she blew.

All temps and gauges were running as normal.

In my opinion unless you have the best money can buy they're close to not much help at all

J

Stavros

Things are different for different cars n specs too, from what ive read on the GTR boards most of them are mapped with AFRs of 10s and low 11s...

XRTypeRS

Was it a wideband AFR meter you had Jake?

Stu @ M Developments

iTrader: (12)

Its a tricky one Neil... i would personally favour AFR for the road,a dn a combination of both for track use.

Unless you run into a problem that retards your spark map, your EGT's wont generally stray to far from the mapped level unless your AFR changes and an AFR meter is faster to respond as its not affected by the heat soak of the manifold like an EGT sensor is..

AFR however can be messed up by anything from complex to simple. A few examples top of my head:

Fuel pump buggered.
Fuel filter blocked.
Fuel pump wiring substandard/corroded.
Slightly too much boost.
Simple coolant or air temperature sensor error.
Map sensor reading low (leaky pipe common)
TPS error (Not registering WOT)
Alternator output low.
Faulty injectors
Faulty fuel regulator.
The list goes on and on... its woefully easy and all too common to run an engine deadly lean.

However.. a gauge is only any use if you happen to be looking at it when summat goes wrong, Or you buy one with adjustable warning light levels that can illuminate a bright warning upon AFR issues, and maybe even trigger a rev limiter or suchlike, which is one of the reasons i like this new one im testing, at least on paper.

ImaRacing 700

You want no more than 11.7 flat out AFR in top gears for safety..FUCK MPG if you want that buy a diesel

Fiecos Dan

yeah lets run 11.7 alday long, inc cruise, idle?????

why waste fuel and bore wash wen could be set up probertly with alittle more time????

Stu @ M Developments

iTrader: (12)

I dont think anyone cares about MPG at WOT Phil, or they would back off, and thanks to decent mapping we can have both worlds

And you dont want any LESS fuel than 11.7 at WOT is what you meant im sure

Stavros

Stu-- Any comment on what i said about big power GTRs seemingly being mapped for 10s and low 11s flat out? Why so rich? And how can you know what that rich is needed? Pure experience of the type of car or?

Stu @ M Developments

iTrader: (12)

Yes Steve,
There are various reasons you would do this and the main one is high EGT's.

The more fuel you put in at high RPM and BHP, the more controllable the EGT will be. The more horsepower we make from a given engine, generally speaking, the higher the EGT will become for any given exhaust design, sometimes necessitating either higher AFR and slightly less power as a result, or a cam/head/exhaust rethink to improve the engines VE and cut down on thermal losses.

Its worth bearing in mind high EGT's are more often a problem with low comp motors than high comp though and a High compression motor could easily run slightly leaner fueling and more economical mixtures with lower EGT's than a low compression lump running exactly the same power level. This can be a major bonus on a competition car and is often a considerable factor in the choice of compression.

The second most common factor is overfuelling most of the cylinders to compensate for excessive airflow in another when individual cylinder trim and/or monitoring is not available. In Fords, the YB is a common example of this.

edited to make more sense....

Stavros

Stu- edit the above post as you seemed to have mixed high and low comp up a few times so im confused as hell

and so on

BTW the cars im thinking off seem to all run about 8.5:1 and im talking 800bhp+ cars from 2.6-2.8 engines revving to about 10k with peak power probably in the mid 8000s (race fuel too generally)

Stu @ M Developments

iTrader: (12)

Try reading that see if it makes more sense Steve.. il have a third attempt if not

Stavros

Aaaaaaaah Makes sence now mate

The thing about unequal airflow is prob a factor too as they affected badly by that.

When you say choice of compression on race cars is affected a lot by how economical itd be, you mean that theyd deliberatley run more comp so they used less fuel so had to carry less or have less pitstops yea?

I suppose only way to know about unequal airflow is 1 EGT probe on each exhaust manifold pipe or summat?

Stu @ M Developments

iTrader: (12)

Yeah, absolutely that, less pitstops can be better than horsepower for obvious reasons, and finding 0.5mpg can be a huge achievement in something like F1 racing.

1 EGT sensor or AFR system on each header is the only way to ascertain equal airflow and mixture distribution. Yes.

Rick

Shings - when did ur car blow? Sorry to hear that What happened?

Stavros

Yea i was wondering about Shings car going bang too?

Neil S

iTrader: (1)

Interesting Posts guys!

Stu would it not be easy enough to design your own controller and provide whatever output you like?

Doesnt sound too tricky

Neil.

SapphyMike

Secs,

I thought you were going to be testing something you were making that eliminated blow ups???

foreigneRS

am doing just that neil

i'm building a microcontroller based 'engine monitor' (shamelessly ripping off the idea of the original SECS monitor) with 8 analogue inputs.

1 will be for egt using a AD594 thermocouple amplifier for a downpipe placed thermocouple taking the average (i also have one in each exhaust 'header' for mapping purposes).

1 will be wideband lambda using the output from my techedge wb02 controller, although i will probably input this onto the microcontroller using a serial port input as i want the other 7 analogue inpts for the usual other things like tps, act, boost, battery voltage, oil pressure, fuel pressure, coolant temp.

it will also have a gps sensor as a serial input for getting the road speed, position, direction etc, and a frequency input for engine speed, and a radio controlled clock and lap timer. the gps can be programmed so that it knows the positions of all corners on the nurburgring and will read out the next corner.

we can easily program the microcontroller to give an alarm (audible and visual) depending on certain conditions, like rpm > 4000, lambda < 0.8 or whatever we want.

the monitor will also output all readings on the serial port and/or CAN bus for rapid datalogging by an external laptop.

should be proper bo i tell thee.

Rick

Up for SHings

Karl

In Shing's absence I shall reply.

Jake bought Tim's old car for anyone that does'nt know.

He took the car to santa pod and on his last run one of the red injector fuel lines fractured. This was evident by a misfire so jake nursed the car round to the paddock area. I managed to reconnect the fractured line using some fuel hose and the engine now ran again. However there was significant amount of smoke coming from the breather, so he called it quits for the day. Jake drove the car home and as the problems had not improved I pulled the engine out to inspect it. The problem was caused by a cracked ring land on one of the pistons.

The new engine went in, but jake sold the car on as the gearbox was also brocken!

The car will be making a return soon with more mods and new owner!!

Neil S

iTrader: (1)

Sounds interesting!!

Keep us posted on your progress

Neil.

Rick

Karl - thanks for reply. Ring lands seem a problem with CVH's. Think it could have been caused by the fuel line? Get any decent times? My engine is going strong by the way - only 15psi at the moment, but pulls like a train and so smooth