Possible detonation, causes?

[Razak]

My cars currently at Whifbitz getting the bottom end sorted (which is painfully expensive [sHOCK][/sHOCK] ) and while thats shocking enough for me, he told me that it might have been caused by detonation. Now since ive got the car its been on a strict diet of V-Power or above and hasnt even been driven that hard alot. Now im no expert in this sort of thing but its not even BPU, its conpletely stock aside from an Apexi exhaust system.

 

I was just wondering what might cause det in a stock TT?

[Tricky-Ricky]

Base ignition timing wrong and det sensor fooked, fuel pressure regulator fooked, partially blocked injector/s,

possible problem with crank angle sensor.

[Terminator]

Previous owner/s ragging the nuts off it, messing with it, decat exhaust no restrictor ring running silly boost and putting it back to stock to sell.

[Razak]

Thats quite a few things >_

[Terminator]

They are reliable when stock and well maintained/serviced. They go for several 100,000's miles.

When I got mine, I thought it had been only used as stock, when the cabin shine crap faded I found evidence of adhesive residue between the driver seat and the centre console, it only showed up when I put the seat all the way back, about two years after I bought it. This was a favoured position for a boost controller in Japan.

 

Yours may well have been stock all its life, and the cause could just be a glazed injector or two, duff fuel pump and all that has been mentioned.

[Morpheus]

Yeah what they said but what exactly is wrong with the bottom end Razak? Just worn out bearings from dirty or contaminated oil or a catastrophic failure from bent rod/s, broken cap bolts or broken crank etc? Bearings only spin when seized from lack of lubrication and heat buildup and/or not enough clearance when installed.

 

Excessive coke/soot deposits in the combustion chambers might do it, as will an excessively rough surface or sharp chamber edges (ideally the cylinder head around valves should be lightly arrissed or dulled, just inside gasket ring) but practically every car of this age with a normal mileage has all of these potential issues. Is the head off? Might want to do a decoke while you're at it (more £££'s I know) and check the piston tops for gouges or damage.

 

Serious detonation under boost would likely bend a rod and/or break the crank/block unless 'they' just got away with it without destroying the engine.

 

More likely I reckon, is that it might have been allowed to overheat, as that will cause detonation in any engine, no problem, as well as plenty of wear, a warped head and still allow it to run fairly normally when it cools down.

 

My old MKIII radiator gave up once and it took three hours to get home from work one Sunday afternoon, stopping every few hundred yards to refill the rad, (not much fun!). When the coolant boils from a lack of system pressure (unless you use £50 non-boiling coolant), you'll hear the engine 'pinking' (detonating) and crackling (sounds like it's going to explode any second!) if you continue to drive it long enough. I didn't have much choice,

 

At the same time the ECU will retard the timing, (spark later than normal to avoid sending the piston/crank backwards when pre-igniting), so that you'll not be able to drive it hard and damage it too badly. It would eventually seize anyway if it got that hot, as mine nearly did.

 

So apart from the previous good advice regarding thrashing/overboosting, (let's face it, quite likely!) or improper timing, (much less likely as would cause starting problems galore and the ECU would probably retard or prevent knocking anyway but still possible), maybe check the radiator and see if it's leaking or perhaps brand new, indicating a blown old one (easy to do if it was original copper with plastic tanks) and also if there's evidence of coolant all over the engine from such a bad leak. Should be red Toyota coolant btw or the aluminium head will corrode if not correct formulation.

 

So what happened to get it in the garage?

Edited November 26, 2010 by Morpheus (see edit history)

[Razak]

Thats alot of information there but as far as i know its not that serious at all, it was jsut a theory by paul, but he could be wrong, ive not seen it myself, i dropped it off at the garage and all i know is the bearings needed replacing, though its costing me alot more money then i have, its gotta be done. Honestly it got to germany and back on a road tip months ago fine, then i jsut hear a light knocking last friday, drove it to the garage on tuesday and he diagnosed a problem with the bottom end and thats really the last ive heard of it. I can only hope that it was just wear or something though bad maintainance in the past and now with the bits changed, fresh fluids and alittle tlc i wont have any more problems. Ironic i brought one because they are known to be very reliable as stock

 

Only good things to come from it is that the timing belts now new and they noticed the crank pulley was in desperate need of replacement so that wont be an issue after either

[Morpheus]

Sounds like you caught it all in time then, like my truck. Ran ok-ish but bearings worn out and back again!

[Razak]

Well lets hope i did, it ran okay, it was only a light knocking, so light i thought it was tapping form the head (was praying loose tappets)

 

So lets pray for the best in the future

[jagman]

Its a long list for detonation :

too lean -

too rich-

timing error

too much compression

carbon -see above

plugs

poor cooling system

pre ignition

carbon -see above

poor fuel mixing atomisation -intake valves/injectors

oil mist from valve stem seals

oil mist from piston rings

too much boost

poor oil cooling

poor engine scavenge

high intake temps -intercooler

oil mist in intake air

poor quality fuel -low octane

plus a few more obscure things !!

 

Driving like miss daisy is probably the worst thing along with short cold start trips (read super low mileage) -as carbon build up is greater , using cheapo supermarket fuel wont help either - funny how these are considered the ideal buy !! , upping the boost or bolt on boost now can cause the dreaded detonation ,,,,

The answer is to eliminate the causes and means head removal and inspection = money

The cars are now old and the days of simply decatting and or pushing boost numbered , now there must be a few checks and inspections carried out or just spin the coin and hope , but expect wallet death

 

"Ironic i brought one because they are known to be very reliable as stock :P" --- They were once upon a time !!!

[Terminator]

 

The cars are now old and the days of simply decatting and or pushing boost numbered , now there must be a few checks and inspections carried out or just spin the coin and hope , but expect wallet death

 

Very good point. In the early days of the forum, the MKIV was 5 year old, the cars we were working on were pretty fresh, so the majority of engines were running sweet as nut. 10 years on things are very different, certainly food for thought especially for those considering going single.

[Tricky-Ricky]

So is the engine apart? or is the det theory just that? i would wait and see before starting to worry what else is wrong.

[Chris Wilson]

If detonation is bad enough to cause big end shell damage there will be obvious piston damage too.

[jagman]

http://www.mahleclevite.com/publications/CEB-1-1208.pdf

[Chris Wilson]

Page 17 of the guide, or page 22 of the .pdf shows detonation damage to shell bearings, good post jagman, a nice guide!

[Morpheus]

http://www.mahleclevite.com/publications/CEB-1-1208.pdf

 

An excellent find!

[jagman]

Interesting that nearly 50% of failures are due "dirt" followed by missassembly as second cause, TBH with the amount of potential failures with high time older cars now , if seeking higher outputs than stock ,lets be fair we ALL want that !! then it really makes sense to simply replace the short block and fit a properly sorted head (dont think toyota do a long block)

You now have a factory fresh unit , and can recondition all the external moving parts and have clean oil ways,water ways,zero wear , THEN bolt on your power .

Easier for install with engine out and save a great deal of time and money and effort .

If seeking specialist use Drag,race,speed events etc - Then a specific build is needed and the coin to fund it!!

Im sure the value of a car with brand new Factory engine , would be lots higher than an old unit fitted , buyers are scared of potential future costs with old performance cars ,enthusiasts will pay a premium , the wannabes wont !

[Morpheus]

Indeed, it's usually cleanliness and basic attention to detail that causes problems.

 

Time and patience, in a nutshell, which very few people have.

 

As the old saying goes, "If a job's worth doing, it's worth doing well".