Flames Flames

[LotusGTR]

Now i never thought the day would come but......the old girl keeps throwing flames and I'm not sure if it's right as it's happening too often. I think that over time it is getting worse. Symptoms. You do redine gear changes and everything is hot, it blows flames when you lift to change (I'm not unhappy with that). The bit that concerns me is that some mid rpm gear changes it still carries on. Even when it's not blowing flames (big ones) I've had feedback (not from the law TG) that there are little flickering ones visible within the pipe. On a light throttle, tipping in or out, there's a lot of popping and banging going on from the pipe. It all sounds like unstable and incomplete combustion.

Now, I've replace the coilpacks (Splitfire) about 9 months ago and it is making plenty (more than ever actually) of power with no misfire under boost and acell. I run a high flow cat (or at least I've been charged for one), stock dumps and a 3.5" SS system and about 25lb of boost. It's a built engine running forged pistons with about 15k kms on it.

Any qualified people want to give me a steer as to what's happening.

I used to love it and try and make the car do it for my own fun, but now it seems it's happening no matter what....

Thanks.

[Adriano]

What ecu? Sounds like overfuelling and retarded timing. Possible cam timing issue, atmo bov?

[LotusGTR]

ECU is powerfc, BOV is stock, stock cams with adjustable wheels. Engine builder has the PFC unit so can't do (nor would I want to) self diagnostics.

[Merli]

Disclaimer: I am NOT qualified to reply to this thread, but I'm waiting for my morning coffee so that I can be productive.

Obviously the root cause if your engine overrunning it's fuel, fuel hitting the red hot exhaust and causing the pretty orange lights.

I assume it's not tuned to run stupidly rich? Your injectors aren't leaking are they? They could be dumping fuel on the exhaust combustion stroke.

The first thing though, is that your cat usually blocks any visible flames, so if you're seeing flames out your exhaust, I'd check that your expensive high flow cat hasn't melted into a molten mess.

[LotusGTR]

Thanks Andrew. Disclaimer noted. It is tuned to run rich cos it has lots of boost, but stupidly so?.....I'd have to ask the tuner and I doubt he'll say it is stupid. Injectors are new 2 years ago (Tomei 700cc - I think) so I doubt they're leaking.

I'm suspecting it's over-fuelled and possibly ignition retared. If you were an engine builder would you under-fuel and advance ignition under 25lb.....? 305 RWKW isn't that much for my set up considering the boost, so that also leads me to the same thought....

How to check for melted CAT? More to the point, what CATs do not melt? Maybe another question is under what conditions do CATs melt and are there CATs out there that handle tuned GTRs.

More hypotheses please!

[Merli]

You're running 25psi and only making 305 rwkw?

Obviously there are many, many factors involved, but as a rough guide, that seems a little low to me.

Even with tiny GT-SS turbos and stock headwork (260 poncams), running 20-21psi, my old GTR made 320awkw (340rwkw?) on CRD dyno (not known for reading stupidly high)

Engine tuners will make an engine run rich to use the fuel to cool down the cylinders and control detonation, at the expense of fuel consumption and reduced power.

[nfi]

In my experience...

The most common causes of flames I have seen (in order) are:

1. No cat (track days destroy cats.. (I had one blow out the exhaust down the straight a flaming molten lava)

2. Injectors aren't switched off on decel

3. Exhaust leak- because you need oxygen and the engine has used up most of it when it combusted it not as easy for it to ignite and hence only happens at full noise when the car isn't using every last bit of it and the exhaust is red hot. When you have an exhaust leak, on decel the engine goes into vacuum and the exhaust sucks (through the gasket leaks) fresh air.. combine that with a red hot exhaust and you get flames even at partial/mid throttle. (in addition obviously to the fresh air (hot once its gone through the motor) being sucked through the engine on decel).

I would put my money in your case as being likely being a combination of all three. Cats don't last long when you are making big power (1.6 bar +GTSS's suggests to me your making a bit ;-) ) as they just get too hot and I wouldn't be surprised if your injectors are not turning off.

Diagnosis

1. Stick your arm underneath the car and give it a good bash with your fist. If it rattles then its obviously self explanatory, its a dull sound then might be all good and if its sounds empty then that would suggest you no longer have one. Otherwise just take it out yourself its really easy. Alternatively, take it to an exhaust shop. Shouldn't cost much at all for them to take it out and put it back.

2. Easiest way to check this is accelerate to 80km/hr on a straight road with decent revs and then just back off. Watch the duty cycle on the power FC. If it doesn't go to 0% within a few of seconds then that will be a large contributing factor.

3. Minor gasket leaks you might not even hear. I had one that you could barely hear when under the car. Jack the car up on stands and then start the car (make sure its stable) then carefully put your hands round each gasket without touching the exhaust and feel for exhaust escaping. Only guaranteed way I have found to do it.

Edited April 26, 2009 by nfi

[LotusGTR]

Yes to everything you said.

You're running 25psi and only making 305 rwkw?

Obviously there are many, many factors involved, but as a rough guide, that seems a little low to me.

Even with tiny GT-SS turbos and stock headwork (260 poncams), running 20-21psi, my old GTR made 320awkw (340rwkw?) on CRD dyno (not known for reading stupidly high)

Engine tuners will make an engine run rich to use the fuel to cool down the cylinders and control detonation, at the expense of fuel consumption and reduced power.

[LotusGTR]

Thanks for that. A small correction, I'm running Garrett 2860 -7s (pretty sure)

Re the cat out the back, that would not surprise me with the amount of kabooms and lighting up the darkness I've had.....Exhaust leak sounds like a biatch to diagnose. I guess the injector thing can be sused by the tuner.

In my experience...

The most common causes of flames I have seen (in order) are:

1. No cat (track days destroy cats.. (I had one blow out the exhaust down the straight a flaming molten lava)

2. Injectors aren't switched off on decel

3. Exhaust leak- because you need oxygen and the engine has used up most of it when it combusted it not as easy for it to ignite and hence only happens at full noise when the car isn't using every last bit of it and the exhaust is red hot. When you have an exhaust leak, on decel the engine goes into vacuum and the exhaust sucks (through the gasket leaks) fresh air.. combine that with a red hot exhaust and you get flames even at partial/mid throttle. (in addition obviously to the fresh air (hot once its gone through the motor) being sucked through the engine on decel).

I would put my money in your case as being likely being a combination of all three. Cats don't last long when you are making big power (1.6 bar +GTSS's suggests to me your making a bit ;-) ) as they just get too hot and I wouldn't be surprised if your injectors are not turning off.

Diagnosis

1. Stick your arm underneath the car and give it a good bash with your fist. If it rattles then its obviously self explanatory, its a dull sound then might be all good and if its sounds empty then that would suggest you no longer have one. Otherwise just take it out yourself its really easy. Alternatively, take it to an exhaust shop. Shouldn't cost much at all for them to take it out and put it back.

2. Easiest way to check this is accelerate to 80km/hr on a straight road with decent revs and then just back off. Watch the duty cycle on the power FC. If it doesn't go to 0% within a few of seconds then that will be a large contributing factor.

3. Minor gasket leaks you might not even hear. I had one that you could barely hear when under the car. Jack the car up on stands and then start the car (make sure its stable) then carefully put your hands round each gasket without touching the exhaust and feel for exhaust escaping. Only guaranteed way I have found to do it.

[nfi]

Thanks for that. A small correction, I'm running Garrett 2860 -7s (pretty sure)

Re the cat out the back, that would not surprise me with the amount of kabooms and lighting up the darkness I've had.....Exhaust leak sounds like a biatch to diagnose. I guess the injector thing can be sused by the tuner.

No worries.

Exhaust leaks I have a passionate hate for... SR20's sound like tractors enough already without leaks

I would check the injectors yourself because the tuner might not even be aware of that feature since its a bit obsecure. He may have left it on to cool the bores but I think its very unnecessary given it compromises response quite heavily as the engine is super rich when you get back on the throttle after backing off and has the potential to actually cause detonation and also wash the bores (of oil) which is really bad. Just literally look at the injector duty cycle and watch the real time readout after backing off. It should go to 0.0%.

[R31Nismoid]

It'll be in the tune Nick - id be surprised if you had a CAT and its flaming... usually a CAT will stop it

Mine rarely flames, Although Snowys car flames a tad more than most for some reason... oh and i dont have the above problem on line one

But most GTR's i know about dont shoot flames all that often

[femno]

I used to have flames Now I get them only sometimes. That changed with the tune.

While cruising no flames or spluttering but just as I open/close the throttle on cruise i have a little bit of spluttering, its only sound though, you cant feel the car jerking or anything.

Who tuned it?

[joeyjoejoejuniorshabadoo]

my old racingline tune did exactly this... including getting worse over time... went to created and it was sorted.

[joeyjoejoejuniorshabadoo]

what CATs do not melt? Maybe another question is under what conditions do CATs melt and are there CATs out there that handle tuned GTRs.

decat

[LotusGTR]

I'd say based on the feedback that I have something that needs attending to, rather than it being 'me' or 'just how they are'. Re the cat, when this was discussed, in context of the whole exhaust that was to be fitted, my tuner was adament I needed one (I was challenging him to go de-cat) due to the potential EPA ramifications. Most if not all my mods are done there and the paper trail would lead straight to him. He said the fines for me are large and for him, larger again and far too large to take a chance on. I'd be 99% sure I have one but what condition it is now in would be my concern.

I'll be checking the tune out I reckon, though that may not be easy for various reasons.......

It'll be in the tune Nick - id be surprised if you had a CAT and its flaming... usually a CAT will stop it

Mine rarely flames, Although Snowys car flames a tad more than most for some reason... oh and i dont have the above problem on line one

But most GTR's i know about dont shoot flames all that often

[LotusGTR]

decat

On the track maybe, but on the road = too risky I'd reckon.

[joeyjoejoejuniorshabadoo]

i run a 3" decat pipe that has a cat shell welded around the outside of it... we welded it right on the flanges so it looks 100% if you tap it it sounds like a cat and it sure as shit looks like one.

[badgtr34]

niiiccee

[Johnny]

Hey man, ive got the same issue with the flames; rarely am i on full throttle but it still pops flames even at 3-3500rpm.

im running a cold (gap whatever: IRITOP7) sparkplug, would that be a cause? anyone

[TiTAN]

if your cat is functioning as it was designed it wont pop flames, my ignition cut shifting while making quite a few loud pops and bangs doesn't shoot any flames just big clouds of carbon.