scoobymyster

Hi , yes I'm a newbie so forgive me if this is a daft question.
I've got a 2001 Bug eye WRX.
Last year just after I'd bought the car I noticed that on a few occasions after I'd given it a bit of stick the orange warning light would come on but engine would not show any signs of any problem and the light would never stay on long. Then one day I was on a local by pass and had a little bell end in a Saxo right up my ***, so naturally I booted it. My car did go but it felt like it was holding back. Then the warning light came on and the car started missing badly and white smoke bellowed out of the back end, I might add that at this point the bell end in the saxo was chuffed ta f•••k with himself and passed me. When the car arrived at garage and they had stripped it down they said I'd melted pistons and that det had accured. I always ran that engine on BP ultimate. What I'd like to know is now Ive got my replacment engine and I only use V power , is it possible that det can still accure. I'm just a bit worried about another £ 3500 bill. What's the best way if any of preventing it.
Thanks

dunx

iTrader: (3)

Octane booster will save you £3500 !

If your car has been modified it may need a re-map, det is often due to running weak (not enough fuel), stick it on a rolling road and see what is going on, may be cheaper to re-map in the long run !

HTH

dunx

Chris.B

iTrader: (4)

Engine Basics: Detonation and Pre-Ignition: Streetrod Stuff

Crosstalk

Dunno how to stop it aside from making sure the engine timing is spon on and it's nothing I've ever had a problem with but Det is actually a nickname (as is "det cans").

It's really premature detonation where the fuel ignites before the spark occurs, due to engine compression squashing and heating the fuel/air mixture to the point it spontaneously ignites. This is how a Diesel engine ignites the fuel, only it's designed that way and the crankshaft/valve timing is set to work correctly like that.

If your engine is suffering from "det" then the fuel is burning before the piston is ready for it's downstroke, thus the explosion is trying to push the piston back down, which is not good.

"Det cans" are simply a pair of headphones that a mechanic will use to isolate the sound to diagnose it.

scoobymyster

That hit the spot. Thanks alot

JP4

iTrader: (12)

Funny you should mention Engine Det as I was on the phone only an hour ago to one of the top engine builders speaking about this!

scoobyc

iTrader: (2)

Actually i think its when the fuel burns to quickly when ignited. Octane booster im told actually makes the fuel burn longer and so reducing the potential for Det.

Pressure + temp = boom. WIth hard engine load such as on a track the temp increases therefore more likley for big boom when you didnt need big boom, you just wanted boom.

LIghting before the spark is Pre-ignition which i believe is different to Det/Pinking.

scoobymyster

So it only happens when your giving it some hammer whist useing poor fuel

scoobyc

iTrader: (2)

think of it like this.

Imagine the fuel air mixture in the cylinder. Now it seems that it doesnt all explode at once. The explosion spreads from one side of the cylinder to the other. This is normal ignition.

Now as you know when you increase the pressure in the cylinder or the temperature things combust easier. Therefore, as the pressure will be almost the same, with the temperature increase, the mix will ignite easier.

So instead of getting say a 1 second burn, you get a half a second burn. Meaning all the energy is released in one big bang. And this is bad! (Detonation - Det).

Imagine you lit a sparkler in your hand, and let it burn for 5 min. At the end you would have some bad burns. Now imagine if you look all that burning energy, and released it in 1/10th of a second. It would be Bye Bye Hand! Same amount of energy released in both occasions, but its how its released which differentiates between burnt hand, and detontated hand.

Octane booster i believe enables the fuel to burn slower but when burnt produce more overall energy increaseing power/torque.

Its not just how Quick it explodes, but also the calorific value of the burn. SO i think octane boosters make it burn slower, and also increase the calorific value of the fuel.



Everything ive just said is probably total BS. Its just to help you try and picture what it is.

Im no engine expert, im only relaying what ive been reading about at work

This is just my understanding of it.


In regards to modding. Anything which increases power is going to mess with the temps, fuel delivery, ignition etc etc. Tbh im not sure if there is a single reason or a single fix for det with a remap.

Hopefully someone can shed more light on how mods Cause det. And how a remap reduces this Det. I.e. chaning fueling ignition etc??

thesyn

Reminds me of when I used to shoot and load my own ammunition. In general terms the more propellant in the cartridge when ignited by the striking of the cap it burned from proximal to distal and quickly produced a large amount of gas which expanded and propelleed the bullet down the barrell. As you increased the propellant more gas was produced and bullet velocity increased linearly.
However if too little propellant was put into the cartridge case it did not burn in a linear fashion but all burned simultaneously exploding producing a much higher pressure within the breech and running the risk of the firearm exploding in your hand.
You see the similarity

Evolution Stu

iTrader: (2)

What your describing there is actually pre ignition. Whilst Detonation can certainly follow pre Ignition, it isn't actually the same thing. Worth bearing in mind.

Jolly Green Monster

iTrader: (4)

if you have had an engine failure and the pistons had melted then it is mostliekly running lean.. I would get it checked else you'll do the next engine.

lean running will also cause detonation.

regardless it needs checking with wideband and detcans..

Simon

scoobyc

iTrader: (2)

Jolly Green,

Would you mind expanding further on how the affects of DET are overcome by a good map. And perhaps how the mods cause this to happen in the first place?

I myself am not really sure the causes/solutions.

Evolution Stu

iTrader: (2)

Detonation has a multitude of causes that can be caused by and thus overcome by mapping.

The most common by far is running too lean.
The second most common is incorrect spark advance.
Boost is relevant, but its relevance is tied quite closely into the two points above.

In my experience, the most common problem is an inexperienced mapper can easily map your car and test it with wideband and det cans, finding all ok so you pays your bill and it seems to be a smile a mile, then you go and destroy it with det some weeks later on the M6 by doing some unsympathetic driving.

The reason for this is essentially bad thermal management and your mapper should have taken into account the effect of multiple sustained hard runs on the EGT's and associated hardware. (Exhaust valve heads, Piston Crowns etc)

Actually, this has made my mind up to do my next technical article on detonation so I can get my teeth back into it as I havent had to explain it to anyone in years. LOL.

The rookie

iTrader: (1)

Det is caused (primarily) by running lean (chamber temps get too high and auto ignition temperature is lower) or the ignition being over advanced, so mapping those faults out fixes it.

Det is either ignition of the mix before the spark arrives (hot spots or auto-ignition) (that is pre-ignition and what used to be common in crummy old iron headed engines all carboned up) or due to pockets of mixture exploding ahead of the arrival of the flame front that originated at the spark plug (more common nowadays and indicative usually of over advanced ignition for the conditions the engine is running under).

Simon

scoobyc

iTrader: (2)

Yeah id love to see a huge article which is very detailed and technical regarding this.

Wiki is ok but it seems that some terminology is used and over look which is relevant. Like they have just wrote it in without understanding it .

thanks for the info.

Coffin Dodger

Beggars belief really that someone will spend £3500 on a rebuild most likely required due to detonation but then not do the subsequent investigation as to why it was detonating in the first place.

On a unadulterated UK Scooby it should not det on normal unleaded let alone super, if it is then something is wrong. Usually attributed to something quite simple, MAF sensor being on of the primary culprits, also possible that the knock sensor isn't working properly so the ECU isn't retarding the ignition correctly, fuel pump could be on its last legs, injector not working properly, etc. The list goes on......

But for you engines sake get it checked over to make sure it isn't running lean, any specialist preferably with a rolling road, should be able to tell you if it's ok in minutes and if not with the help of something like delta dash point them to the broken sensor fairly quickly.

scoobymyster

£3500 on a replacment engine not a rebuild.

Coffin Dodger

Either way if the previous one blew up due to a faulty £90 MAF sensor then the replacement will go the same way. The MAF sensor is not attached to the engine

Evolution Stu

iTrader: (2)

Well, I will have one published soon. Wont be excessively technical as i need to write so the average petrol head can understand and digest it instead of scanning it and thinking its too much, but I can usually squeeze the meat in there somewhere.

Wont be available for web use for many months though as my contract with the publisher gives them exclusive rights to it until the magazine is out of print.

Evolution Stu

iTrader: (2)

This is a very valid point and something so many people just overlook. Often a simple clip missing from the FPR pipe can destroy an engine in seconds. Seen it so many times.

Kieran_Burns

iTrader: (1)

I lost an engine due to a melted piston. My old Calibra Turbo... the bottom line was that I spent all my time focused on sorting out the air and boost and neglected the fuelling.

On the A50 booting it past a fiesta (21psi held) and whump. Oil, smoke, odd noises. New engine

I should've uprated the FPR and injectors but didn't and paid the penalty. Everything is about balance and if you get it wrong you lose out.

scoobyc

iTrader: (2)

Ok so fuel wise what is suggested to delay the on set of a big boom?

Fuel pressure regulator? I mean. Is it the fluctuation in fuel, lack of ability to pump the fuel in, or two much fuel being pumped in or the way in which its pumped in? There are loads of different fuel related mods. Would be interested to hear the low down on each.

My only opinion previously (im new to modding) would be to uprate the fuel pump so more can be pumped at higher pressure(?) and larger injectors to physically inject more petrol. With other modifications?

I guess fitting a det sensor device would be an idea to give me early warning and also a RR trip.

I guess some of the things which happen fall under the "unlucky/**** happens" category. But for the sake of a few quid if its a preventable measure it could be worth some wonga.



Stu if you need anyone to "proof read" your document pre-publish feel free to drop me a pm/email

Evolution Stu

iTrader: (2)

Fuel wise its all about controlling combustion temperature. Too many DIY Tuners see the figure 12.6 gives best power and thinks great, I'm tuning for 12.6 then. You simply cannot do that without modern management that incorporates some decent thermal management systems.

The FPR issue is the fact that most are rising pressure and some even rising rate (Subtle difference) and in a nutshell for every 1bar of boost you run, you get 1 bar extra fuel pressure. This is required to keep the differential pressure across the injector correct and linear. If you lose any of that differential pressure at the nozzle side, the engine will likely melt down. So many people think that all FPR pipes are actually for vacuum, they are not, they also carry a pressure signal, so tapping your boost gauge off it with its leaking pipes may well cost you an engine. Yes, thats a £3500 hose clip there sir. Please ensure its tight. lol

Given the way this conversation is turning, two documents you chaps may find of interest are as follows:

Unlucky 13. (This is the 13 biggest Cosworth problems, but can be applied to most turbocharged motors really)
http://www.motorsport-developments.c...AF257.tech.pdf

Under Pressure. All about Fuel Pressure.
http://www.motorsport-developments.c...AF242.tech.pdf

I am no Subaru expert by any means and do not profess to being one, but i have been tuning and mapping cars all my life and the principles remain the same no matter what your tuning.

scoobyc

iTrader: (2)

Wow this is really good information Stu.

I shall ingest these documents tomorrow at work

Where did you learn all this information? Years in the industry? Unfortunutly im in IT but this is the stuff im really interested in, and wish i could earn a living from it.

Evolution Stu

iTrader: (2)

Thanks. I am a level 5 FI tech by trade, but the usefull knowledge is all self taught after many painfull years in the industry.

dazdavies

iTrader: (22)

Moral of the story don't use BP Ultimate. Its crap.
V - Power or tesco 99 and a Proper remap.

I used Ultimate once and got more det on my PFC than I did when the time I got caught short and had to use Esso 95!!!

biggazvr6

iTrader: (8)

Id never use BP again, Like said above, if you have any mods, likely hood is parameters have changed. Take it easy for now and get car booked in with a mapper asap. They'll look over the car, poss put wide band on and have a check for little money. They'll then be able to advise you as to the cure. every car reacts different to mods so the only person who will no whats going on with yours will be the guy who looks at it.
Remaps with ecutek which i think is the software they'll use to map you ecu start at arround £500 ish give or take with most mappers.
Once its mapped you've got the peace of mind that its right then if its from a reputable mapper.
Bear in mind, once the mapper has found out whats going on, if you have no mods but want a little more power,to save you cost in the long run get a decat exhaust system and pannel filter before you get the mapper to map it, that way you'll say the cost of another mapping session. Plus you should see a little over 260bhp from those two mods. If you want details of a decent mapper i use just PM me ill give you his details. He lives up in lancs but will travell and im sure you could sort a deal for the mapping with him too. He's a great bloke and knows his stuff, did wonders for my car.

biggazvr6

iTrader: (8)

Nice wagon BTW! another wagon owner on board, some of us have to i supose!

+Doc+

I noticed that I only get the sign of knock (one amber light on the knocklink never been into the red) when my fuel is low, normally it barely moves off green on max settings. Is this just a coincidence?