detonation.
Turbo Mini Forums

had a few thoughts about this today and wondered if it would be interesting to everyone?

there seems to be a lot of det damage going around , blown head gaskets and melted broken ring lands etc , and some notes that occurred to me are ..

1) timing..

in my car I find that 95 octane is fine on a 8.5:1 cr up to 12 psi ,on a 12:1 afr.

if I run only 6 psi flat out at high revs for a while , then I get the kl flashing. what this tells me is , that while a brief blatt up the rd is ok , let the heat build up ,and it will det. whatever the boost , on the ignition timing I have in the car .

so , if your on a test run , dyno or otherwise , and do a short run say 10 to 20 seconds , don't assume that ignition timing will be ok for longer full throttle runs . be cautious . it may be that you have 22 degrees of timing and its fine on 15 psi , for a 20s run on the dyno .but hold it at that for 3 times on the track , and something melts ,and you would be better off with 17 degrees , losing say 10 bhp on the dyno , but having an engine that lives .


2) chamber shape..

having the beak in the chamber creates more turbulence. this speed up flame front travel ,so it takes less time to burn the mix , timing needs to be less advanced ,and the mix can run a bit leaner , since its a race in the cylinder between the flame front burning as it should ,and the pocket of mix trying to detonate . if you can burn everything quickly enough before the det occurs , you can run a leaner mix,because you don't need the extra cooling from running rich ...alternatively you can run rich and possibly use more boost .


3) octane .

this has a direct effect on how much boost you can run . fuels octane rating is a number that lets you know how easily the fuel will det . the higher the number the better , if I go racing I will use shell v power ,and run up to 23 psi pk 19 steady . I and matt woods had simultaneous identical blown head gaskets 2 years ago at avon . I have put this down to bad fuel . don't allways trust what you buy ,and try to get to the stn when they have just filled up ,,the last fuel in the stn tanks is the lowest octane of that batch .
using a lower octane than you expect can ruin your whole day !


4) cooling system.

in the light of the terminators head and piston calamity , I am wondering about the dry decking trend.

I see the water coming into the block ,passing over cyl 1.2.3.4...then into the head at 4 and then over 3.2.then 1. if the water has picked up heat from all 4 cylinders then 3 chambers , it arrives at no 1,pretty bloody hot .

simon has had damage to no.1. and I wonder if this is a reversed trend from the no.4 being the hot cylinder . I did a survey on which cyl blows on here somewhere but forgot to ask are you dry decked.
personally I prefer the idea of the water running up from the block through the head face as it seems more even . and then plumbing no 4 heater outlet into the top hose to alleviate that corner .although on my car I haven't done that and rely on my huge metro mk1 rad instead.

a step I like the idea of , is if dry decked run the hose out of the block into a small motorbike rad , then back into the head .this would give no1 a cooler shot at the other end.
alternatively leave the head open to the block , and connect an outlet on the no4 end of the head and take that to a 2 port entry to the rad,the other port coming from the other end of the head.

I like the idea of running a thermostat, keeping pressure up in the head and avoiding steam pockets.

5) mixture..

its great temptation to run a little lean ,and save fuel .if this is at the cost of aluminium ,its not a good choice.
a test on a hot day on the dyno can mean the air temp is up ,the air is thin and the mix may be right .
put that same engine in a cold environment and it can be running lean . and die .its a competition between the cold air making it cooling in the chamber so its less likely to det ,and the lean mix doing the opposite .you'll soon know which factor takes dominance.

I have found that my engine appears to like a leaner mix 12.5 to 13.5 to one ,than one would choose on a turbo engine to keep it safe .if I assume that the inners are running richer and outers leaner , then its averaging out in the downtube .I may be running 12:1 on the inners ,and 14:1 on the outers..

a scary thought . without data I don't really know ..but the moral is , run a bit richer than ideal in case the outers are well lean .


6) plugs

run a 7 or 8 ngk. I ran 7's predominately ,then went to 8's its a little less happy on cruise even with an msd
but its a little safer from the plug heating up and maybe causing det.as an example , on the astra turbo lpg , with very high temps in the cylinder , I ran 7's the only had some new 6's to put in ,within a week it had blown the head gasket .

7) turbo specs/design..

if running a small turbo for good response on the street , don't expect the chamber to be as det resistant as a engine using a big low back pressure turbo.

same for intercooling a big intercooler will allow more timing and det resistance than a little one .provided you are up in the boost areas where its needed.


8) red mist..

a small anecdote to demonstrate..

at avon in 2011 I had my light doors on ,my new sidepipe and it was avon time .. I had been trying to get a good launch off the line , and finally I got one , the steering wheel boss shot out and hit me in the chest and it was going to be a stonker ,slammed it into 2nd flicked to high boost pulled out choke and car did its usual berserk scrabbling for grip as it hit 23 psi .flailing around like an angry blue marlin with a toothache ..RED MIST TIME ...

yup ,the knock lite started flashing and I had two choices , back off ,or floor it .I chose door number three and tried.. pathetically unsuccessfully.. to lift and reapply the pedal to get it to stop flashing and still somehow do a good run ...HOPELESS. back to base on 2 cylinders 40 miles away was the upshot ...numpty!

bottom line is its an engine ..do something to it that it doesn't like ,and it will die .doesn't matter if you just watched fast and furious for the 45th time , or if a bit older ,mad max 1. it will still die .doesn't matter if you just had an argument with your girlfriend and her mother ,the engine wont care. youll just get no sex ,and have to rebuild the bloody thing (the engine that is , not your libido)

so listen to it and treat it nice .

regards
robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

What an excellent set of musings Robert,I particularly relate to 'bottom line is it's an engine..............'

'Where does the engine go?'

Yes nice write up there.

Nice Robert just what I was looking for.

As for the Dry decking thing last time I did a head gasket it was 4 and 3 that went and that was on a long drive at a steady 70mph.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

Thats a few thoughts? thats a months worth for me

I think we where really lucky with the metro van. When it was on the rolling road the tuner ran a fan something similar to this:



Engine temps never really got above 60-70 degrees and I would assume this held back a lot of potential problems.

When we went on the Rolling Road day, they wouldn't wind it up beyond 16psi as it was apparently detonating. They where only running a more moderate sized fan.

We did have a huge and very efficient intercooler, taking up the whole front of the vehicle with ducting to force all air through it.

John's default driving mode was 'Red Mist' so we where both presently surprised to find the pistons factory fresh when we pulled the engine apart.

We had no dry decking, no coolant leaving the head at the heater tap, a supply from the bottom hose getting pumped round the turbo and back into the top hose above the thermostat. It just ran a cheap fiat cinq rad with a cheap fan behind the intercooler. Worked a treat.

Great write up!

Reading up on RTS Clutches

Pmsl red mist is a bitch

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

Red Mist

As opposed to the green mist which usually lingers around my tent

If something is worth doing, it's worth doing half of.

Thanks for sharing Robert.

In the 13's at last!.. Just

Strangely, my head gasket seems to go when I'm driving like an old lady.

In the 13's at last!.. Just

Mine leans out when pottering about also, say up a slight slope, off boost or with very little boost, say a couple of psi. However driving full throttle full boost the afr is between 10 and 11. Its down to the needle, maybe this is what yours suffers with?

More Boost is always going to be hard temptation to resist.

The human desire to always go fast is an expensive hobby.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

So in conclusion to that a 5 port and carburettor are less than ideal.

Ive had a feeling since Avon the other day that Simon had an air pocket in the head because the radiator is low. Now I know the last time the gasket went it was 3 + 4 that blew it makes me believe that even more and the air pocket seems to form in random places in the head, thoughts?

I seriously doubt it!

That's something I have never really thought about mate.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

If you connected your heater take off in the head to the thermostat housing or header tank with a small id pipe it may give a point at which the air could bleed off.

Is your piston damage from det or just from the drive to the pub with a blown gasket?

Edited by paul wiginton on 28th Jul, 2013.

I seriously doubt it!

Also I have always used that wetter stuff in the past but I have not put any in this year Could have something to add to this.

Edited by madmk1 on 28th Jul, 2013.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

I've always had the #4 end heater take off plumbed into my top hose, never blew a head gasket and I used to drive it like i hired it everywhere.

It did used to get some massive air pockets in the head, every time i filled the system for the first time i had to bleed off the air from the heater tap.

I guess I was just lucky though

I have a temp sender in a thermostat sandwich plate. I had to bleed mine through that and the top hose to get mine to fill properly.

I just turn the pump on and full it, maybe I am just doing it wrong

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

gary , id go for too much cruise advance ?that's what killed my 16v propane gasket /lands.but that sort of knocking you can usually hear. especially on tip in , where you just open the throttle to go from vac cruise to 2 or 3 psi.

re pauls suggestion , good idea paul , I hadn't realised simon has no bleed at the top . I have a pipe on the therm housing blocked with a bung , I just pull the bung out and let it bleed.having said that , with a powerfull pump id expect it to clearance the pockets , but I don't know if simons is that powerful .
re the piston damage , i'd say that was done at full chat in 4th or 3rd on the track .prob 4th after the heat has built up .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Yes It is mate. it has a good push to it, I also have a sleeve in there. as if I used a sat I would get no return. Also its more of a swirl pot I have, as a norm its 1/2 full.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

Interesting stuff Robert.

I believe a lot of cause for detonation lies with cooling efficiency in all aspects, and as a result I've spent a fair while thinking about cooling design for mine, for both the coolant and intercooling circuits/components.

The other things you mention such as fuel quality and extended running at full chat will definitely change the characteristics of how much heat is present in the charge entering the engine, how much heat is generated by the ignition of that charge and ultimately, how much heat the engine generates as a result of the charge ignition. My guess is that it's a big balancing act, and a tricky one at that, if you wish to run the engine on the ragged edge of it's abilities, and it would be wise to sacrifice some of the total power output in an attempt to preserve the engine against environment changes for things we believe are constant (fuel quality, etc).

As you say, tuning a car on the dyno for maximum output is not the best way of preparing the engine for every day running (more so on demanding running), and is only realistic if you can maintain the conditions you had on the day the tune was performed, to enable predictable results from the engine, without fear of detonation. So it may be best to establish the ideal tune for your engine, and then edge towards more conservative timings, keeping the fuel in check for the engine speed/load conditions accross the board.

Just my 2 pence, of course!

one can always hold the engine on a dyno steady state , or do a much slower run up ,that way the engine has the chance to throw up any anomalies while being tested .
I tend to like dyno sweeps of 30 seconds instead of the normal 10 seconds seen nowadays for just that reason.
steady state testing can be a little bit punishing .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

This is where my car fell down as the fuelling in 2nd gear was shit as on the RR everything was done in 3rd (if that makes sense)

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.