Motor blown on dyno tune...??

[Roscos]

Get over it you have rebuilt the bloody thing and when you are pulling 194 rwkw's, its not going to last that long and l know the motor has been put back together, and thats what it was pulling before it let go.


Roscos

[TheToyman75]

YelloRolla, I guess we are both correct because each combustion chamber may not be symmetrical to each other due to the mirror image effect, however they are all symmetrical with respect to the spark plugs location in each combustion chamber.

Dick,

I think what is clear is that is does matter which spark plug you choose to fire should you decide to only fire one per cylinder (For whatever misguided reason).

Some Alfa Romeo's do fire there twin spark ignition one after the other for emissions reasons and they typically used a smaller spark plug as the trailing spark. Not all twin spark alfa motors work this way as some of them have the spark plugs symetrically located in the hemisphere and fire them simultaneously. These symultaneously fired Alfa engines were quoted by Alfa as making 3% more power (than there single spark equivelants).

Twin spark upgrades are also common place of the more serious older porsche 911 engines, they too fire the plugs simultaneously and its a recommended upgrade for high compression porsche engines with a large cylinder bore.

Like porsche, Toyota went twin spark for the performance gain (4T-GTE uses same head as 3T-GTE and both were competition engines in their day) and they DO fire simultaneously (You own one, go to the garage and take a look, I know you have the tools to check it ).

Installing 2 spark plugs per cylinder increases combustion efficiency and reduces the time it takes for complete combustion to occur, This means ignition timing advance can be reduced because the spark can be fired closer to top dead centre. Reducing the ignition timing advance can also reduce the opperating temperatures of high compression engines. More importantly reduced ignition timing (And still allowing for a complete burn) provides a performance gain due to the reduced amount of the combustion process happening BTDC. (Ie less power pushing back on the piston as it approaches TDC)

For further support take a look at the 126E, The 8 valve 2TG Race engine,
http://www.toymods.net/~rod/2TG%20Pi...26E%20Cams.jpg

Do you think they made the race only head twin spark for emissions ? The 16V 151E head did go back to a single spark plug but thats purely a space issue. I am pretty sure Alfa are the only manufacturer to do a twin spark 16V variant but I am getting side tracked again.

[TheToyman75]

Get over it you have rebuilt the bloody thing and when you are pulling 194 rwkw's, its not going to last that long and l know the motor has been put back together, and thats what it was pulling before it let go.


Roscos

Rosco,

What makes you think it won't last long at that sort of power ? If its assembled right with quality components, Tuned well (not just making a number), well maintained and fed quality fuel why shouldn't it last ??? Jason's 3T-GTE has been making figures bigger than that for quite some time and his engine has probably done a good 80'000K's !

[kojab]

Dick,

I think what is clear is that is does matter which spark plug you choose to fire should you decide to only fire one per cylinder (For whatever misguided reason).

Some Alfa Romeo's do fire there twin spark ignition one after the other for emissions reasons and they typically used a smaller spark plug as the trailing spark. Not all twin spark alfa motors work this way as some of them have the spark plugs symetrically located in the hemisphere and fire them simultaneously. These symultaneously fired Alfa engines were quoted by Alfa as making 3% more power (than there single spark equivelants).

Twin spark upgrades are also common place of the more serious older porsche 911 engines, they too fire the plugs simultaneously and its a recommended upgrade for high compression porsche engines with a large cylinder bore.

Like porsche, Toyota went twin spark for the performance gain (4T-GTE uses same head as 3T-GTE and both were competition engines in their day) and they DO fire simultaneously (You own one, go to the garage and take a look, I know you have the tools to check it ).

Installing 2 spark plugs per cylinder increases combustion efficiency and reduces the time it takes for complete combustion to occur, This means ignition timing advance can be reduced because the spark can be fired closer to top dead centre. Reducing the ignition timing advance can also reduce the opperating temperatures of high compression engines. More importantly reduced ignition timing (And still allowing for a complete burn) provides a performance gain due to the reduced amount of the combustion process happening BTDC. (Ie less power pushing back on the piston as it approaches TDC)

For further support take a look at the 126E, The 8 valve 2TG Race engine,
http://www.toymods.net/~rod/2TG%20Pi...26E%20Cams.jpg

Do you think they made the race only head twin spark for emissions ? The 16V 151E head did go back to a single spark plug but thats purely a space issue. I am pretty sure Alfa are the only manufacturer to do a twin spark 16V variant but I am getting side tracked again.

Toyman75 good to see you are looking for answers by searching on the net as I do.

Used this string from your previous post "ignition timing advance can also reduce the opperating temperatures"

Found this

http://books.google.com/books?id=83H...PjJOU8QXleZGqU

Good info here and some that also supports my theory.

Quoted from Wayne R. book
" To reduce cylinder head temperatures and reduce detonation, I recommend that a twin-plug ignition system be installed if your compression ratio is higher than 10:1. In addition twin-plug ignition systems should be installed on engines with piston diameters greater than or equal to 98 mm."

It goes on to talk about ignition flame front taking too long to propagate across the combustion chambers with engines of larger cylinder diameters. The 3T-GTE uses 85 mm pistons and if we are going to fire both plugs simutaniosly we are certainly going to have to flame fronts colliding and possible causing detonation as the cylinder size is smaller than the 98 mm talked about above.

What this thread is all about is possible causes that lead to GW's engine detonating and it could be because he is firing two plugs simultaneously with high boost.

Just adding that it wasn't exactly untuned before he took it there, it was running the maps from his old 3T-GTE, and only running a 3 psi spring before we fitted the 17 just before taking it there.

Who runs high boost (15 - 30 PSI) on a 3T-GE engine firing both plugs simultaneously? I know YelloRolla doesn't as he is not using the 3T-GTE head.

[kojab]

Rosco,

What makes you think it won't last long at that sort of power ? If its assembled right with quality components, Tuned well (not just making a number), well maintained and fed quality fuel why shouldn't it last ??? Jason's 3T-GTE has been making figures bigger than that for quite some time and his engine has probably done a good 80'000K's !

I defiantly agree with you here.

[TheToyman75]

Toyman75 good to see you are looking for answers by searching on the net as I do.

Used this string from your previous post "ignition timing advance can also reduce the opperating temperatures"

Found this

http://books.google.com/books?id=83H...PjJOU8QXleZGqU

Good info here and some that also supports my theory.

Quoted from Wayne R. book
" To reduce cylinder head temperatures and reduce detonation, I recommend that a twin-plug ignition system be installed if your compression ratio is higher than 10:1. In addition twin-plug ignition systems should be installed on engines with piston diameters greater than or equal to 98 mm."

It goes on to talk about ignition flame front taking too long to propagate across the combustion chambers with engines of larger cylinder diameters. The 3T-GTE uses 85 mm pistons and if we are going to fire both plugs simutaniosly we are certainly going to have to flame fronts colliding and possible causing detonation as the cylinder size is smaller than the 98 mm talked about above.

What this thread is all about is possible causes that lead to GW's engine detonating and it could be because he is firing two plugs simultaneously with high boost.




Who runs high boost (15 - 30 PSI) on a 3T-GE engine firing both plugs simultaneously? I know YelloRolla doesn't as he is not using the 3T-GTE head.

Dick,

Jason (YelloRolla) Ran high boost on the 3T-GTE head for a good few years with no trouble at all - from memory he was running 25psi. The move to a 2TG head was purely based on port design and not to reduce the number of spark plugs. I should know I'm the one who did all the flow testing for my own T series engines. Further to that I know Jason has done extensive Dyno testing running single and both spark plugs with no down side to running the twin spark set up. He can comment further on that of course as second hand info is never the best.

The 98mm piston size (For Porsche's) is the point where they recommend you should deffinatly have two spark plugs, not the minimum size. The twin spark Alfa's run a smaller bore than the 3T-GTE.

I have heard the arguement re the twin flame fronts a few times over the last 16 years that I have been working with the T series Twin cams. Mostly its from people who's "mate Said" tho and is therefore not worth discussing. I think if nothing else Toyota's Persistance with the twin Spark in High boost and high compression race engines (The 4T-GTE and 126E for example) is reason enough to discount it as an issue. If It is a reliable and desireable characteristic for a competition and factory backed race team I think its probably not a bad idea.

[ONCE-NA]

Being that the damage from detonation was most prominant on cylinders 2 and 3, (it was evident but to a lesser extent on 1 and 4) i was thinking that maybe those 2 cylinders were running leaner due to the factory plenum design flowing more air to those at high boost levels, We didn't end up using the plenum I had been using in my car due to the shortcommings of the early Haltech. -Couldnt get rid of the dizzy.

[o_man_ra23]

This bites nutsack... and unfortunately you will probably be up for the whole cost.

HOWEVER... with only looking at what you have presented, there was an obvious issue noted in the second last run (and probably in earlier runs too, but have not enlarged the dyno graphs to look) which means the tuner should have STOPPED and re-assessed the map before continuing, to minimise damage. Also they should have stopped as soon as they got a bad dip in the output... obviously a sign of a problem, and you dont go boosting and revving a motor when the map has a problem... its negligent.

So, I think you may be liable for some of the damage, but the tuner did seem negligent, and the liability waivers you sign DO NOT cover them for negligence. So I think that
a) you should not be charged for the work provided
b) they should be contributing to the cost of repair. How much is their responsibility will be determined by how much damage would have been done if they stopped when they first noticed a problem (when the normal risk stops and negligence starts) and how much damage was actually done. This will be difficult to assess and prove, so having a realistic figure for them should aid in getting back some of your hard earned.

Thats just my advice, and the path I would take. Either way, your up for a rebuild, so heres hoping you have learned all the lessons you will need to learn this time around.

[rms]

Just downloaded the gasket pic to have a close look.
The dents in the seal ring are not from detonation.

The gasket was damaged from the original build !

[thechuckster]

this bit

It goes on to talk about ignition flame front taking too long to propagate across the combustion chambers with engines of larger cylinder diameters. The 3T-GTE uses 85 mm pistons and if we are going to fire both plugs simutaniosly we are certainly going to have to flame fronts colliding and possible causing detonation as the cylinder size is smaller than the 98 mm talked about above.

is contradictory...

The two sparks enable you to control flame fronts rather than have a detonation event.

It short-circuits the "flame front taking too long to propagate" by starting the fire in two locations.

a better defintion? ... Having a long flame travel in a less-than-satisfactory combustion chamber shape (e.g. poor squish) makes it prone to detonation, thus the twin flame fronts reduces the risk of the charge furthest from the spark/flame-front detonating before the flame front reaches it.

[YelloRolla]

Thanks for your input Toyman75.
With regards your response "Actually the stock system fires both spark plugs simultaneously." From my experience the conclusion I have drawn is such that I disagree with you and the reason the plugs are fired one after the other is to aid in emissions and efficiency, however after saying this I am open to changing my opinion provided suitable documentation supports the alternate opinion.

I just placed the timing light on #1 front spark plug lead and then on #1 rear. I could see no apparent offset in the ignition event.

[YelloRolla]

FWIW Johnnies engine made 185kw everytime it hit the rollers with ~20psi and using both plugs.

I agree with you Dick about that it is about why GW's engine may have blown, and this whole discussion should perhaps take place elsewhere. I don't think that GW is running a lot of boost though (15psi). I ran 23psi with no intercooler on a stock bottom end, firing both plugs....

[thechuckster]

re: non-simultaneous firing - only rotary engines do the staggered firing events (also known as trailing spark).

[kojab]

I just placed the timing light on #1 front spark plug lead and then on #1 rear. I could see no apparent offset in the ignition event.

Thanks for that YelloRolla. At least we know at idle (I presume with your test) both plugs fire at the same time. Next step is to see what happens at high boost. Would need a dyno to check this out.

What was the highest boost you had on your KE20 with the 3T-GTE head firing both plugs simultaneously before you used the 2TG head?

Edit Sorry just read your new posts.... I took too long to post mine.

[YelloRolla]

Kojab - the rotor button is fixed, that is there is no way to change the event of one spark relative to the other.

The maximum boost that I ran with the twin plug head set up was ~28psi. This was with the CT 26 and JMR intake manifold. 28psi was recorded early in the rpm band (around 4000-4500 rpm) which is incidentally where these engines are most detonation prone.

I am going to start another thread titled 3T GTE tech.