Flames/backfire high revs
Discussion
The scenario
Accelerating hard in 1st or 2nd gear then as I'm changing gear at 5500/6200 revs there's a huge backfire and flame out the exhaust,
Is this just unburnt fuel or something more sinister.
It's not something I can replicate at all times but I've often heard it, someone else mentioned flames!!
I honestly don't need flames out the back so should I be talking to my mapper about it.
Oh running aftermarket Ecu so trigger wheel and bespoke ignition timing / fuelling etc.
Just some technical thoughts on exhaust flames and in my case a very prounounced bang that feels like it will rip the exhaust off or blow a hole through it, it's like the explosion happens as it exits the exhaust rather than earlier in the exhaust system. Sleeved pipe too!
I learning as I'm writing, so if it's in the exhaust it can't be timing now can it, that's ok then
I'll have someone going over it but just wondered if all this flames crac is a good or bad thing
Cheers for any thoughts in advance
Accelerating hard in 1st or 2nd gear then as I'm changing gear at 5500/6200 revs there's a huge backfire and flame out the exhaust,
Is this just unburnt fuel or something more sinister.
It's not something I can replicate at all times but I've often heard it, someone else mentioned flames!!
I honestly don't need flames out the back so should I be talking to my mapper about it.
Oh running aftermarket Ecu so trigger wheel and bespoke ignition timing / fuelling etc.
Just some technical thoughts on exhaust flames and in my case a very prounounced bang that feels like it will rip the exhaust off or blow a hole through it, it's like the explosion happens as it exits the exhaust rather than earlier in the exhaust system. Sleeved pipe too!
I learning as I'm writing, so if it's in the exhaust it can't be timing now can it, that's ok then
I'll have someone going over it but just wondered if all this flames crac is a good or bad thing
Cheers for any thoughts in advance
6200, yeah it catches me out every now and then as the rev counter catches up with the engine speed, Hmmm,
So maybe I've just touched the limiter as I hit the clutch, I'm sure I've done this without hitting the limiter though.
The BBWF this year,,, there's a video of all the boys leaving for the run down to Topcats, I've sat at tickover for a good few minutes then we leave, I do the obligatory race start for the camera and listening to it later you hear the backfire and someone else mentioned flames,
It's when I change gear and could well be me just tickling the limiter that day too.
I hardly ever get it as I don't drive that hard but that video has always bugged me really.
Jason will put me right but as the weathers so crap for driving thought a thread about flames might lighten the gloom a bit
So have I just got a monster engine and should like these flames or should I be getting something done about it.
I bet it doesn't do it on a rolling road for a start!
ETA II've been using a lot of 95 Ron,,,,,
My car is mapped for higher octane but can be fine on 95 but not full revs!!
Maybe I still had residue 95 in the tank.
I've been back on higher octane for awhile now so I'll try and see if I can get these backfires with the higher rated fuel.
So maybe I've just touched the limiter as I hit the clutch, I'm sure I've done this without hitting the limiter though.
The BBWF this year,,, there's a video of all the boys leaving for the run down to Topcats, I've sat at tickover for a good few minutes then we leave, I do the obligatory race start for the camera and listening to it later you hear the backfire and someone else mentioned flames,
It's when I change gear and could well be me just tickling the limiter that day too.
I hardly ever get it as I don't drive that hard but that video has always bugged me really.
Jason will put me right but as the weathers so crap for driving thought a thread about flames might lighten the gloom a bit
So have I just got a monster engine and should like these flames or should I be getting something done about it.
I bet it doesn't do it on a rolling road for a start!
ETA II've been using a lot of 95 Ron,,,,,
My car is mapped for higher octane but can be fine on 95 but not full revs!!
Maybe I still had residue 95 in the tank.
I've been back on higher octane for awhile now so I'll try and see if I can get these backfires with the higher rated fuel.
Edited by ClassiChimi on Sunday 4th December 17:46
Apart from intentional mapping, I found two ways of getting this effect:
1. Faulty exhaust silencer box
2. Pull a plug lead off.
However, I have also noticed that with a hot engine it is easy to get this effect by the simple expedient of suddenly lifting off the throttle at high revs.
Mat Smith was following me round Cadwell Park on a track day and commented that when I backed off from 6000 rpm in 2nd for Barn Corner, I nearly singed his eyebrows. With a little practice one can also provoke screams amongst the kids in the cafe, as the lift off point for the Hall Bends is bang outside the corner of the cafe
1. Faulty exhaust silencer box
2. Pull a plug lead off.
However, I have also noticed that with a hot engine it is easy to get this effect by the simple expedient of suddenly lifting off the throttle at high revs.
Mat Smith was following me round Cadwell Park on a track day and commented that when I backed off from 6000 rpm in 2nd for Barn Corner, I nearly singed his eyebrows. With a little practice one can also provoke screams amongst the kids in the cafe, as the lift off point for the Hall Bends is bang outside the corner of the cafe
tvrgreg said:
LOL.Nowt wrong with a tiny bit of flame now and again, Heres one i did a while back https://www.youtube.com/watch?v=6URIwjMAutY
I can't open this Greg. https://www.youtube.com/watch?v=6URIwjMAutYAir leaks, but I haven't got any, only today I was secretly admiring its purring qualities when walking around the front of the car, no air leaks Peter, no soot or anything, it's very quiet at the front with the cat in, it's different around the back mind.
I can't remember if it did this with the standard pipe so you might have something there Anthony,
Fully sleeved at the mo, coupled with MBE it's the nuts.
It's not effecting the engine as in pinking but it's like a build up of gases them boom, or crac and you feel the pressure change!
I might get Jason to map out the overrun pops and bangs,,, or maybe ask for more
Ok I can relax then, I'd imagine my rev limiter is ign controlled Richard, it comes in like switching the car off, good point, I'll ask ?
Hi Al,
I have that as well. http://www.pistonheads.com/gassing/topic.asp?h=0&a...
It does make me smile!
I have that as well. http://www.pistonheads.com/gassing/topic.asp?h=0&a...
It does make me smile!
ClassiChimi said:
I'd imagine my rev limiter is ign controlled Richard, it comes in like switching the car off, good point, I'll ask ?
Do you really need the rev limiter feature Alun?I haven't activated it on my Canems system, I just change up when my ears and mechanical sympathy tell me to.
I guess it could help if say you went from 5th to 4th but accidentally found 2nd, but that would be a very rare scenario, disastrous miss shifts aside at all other times its my experience the old Rover V8 will do an excellent job of letting you know when it's time for the next cog.
If you find your rev limiter is the source of the issue get it deactivated and use your ears instead mate, you're a motorcyclist after all, and no one has better ears for revs and shift points than an experienced motorcyclist
The system works like this....
Dave your entirely right, the Tvr still sounds like it's on tickover compared to a bike screaming and asking for another gear,
I'm ok on track as I get the vibes sorted in my little head
Dom set the limiter,, I wonder why
The truth is I've had these flames and the Big Bang without hitting the limiter.
Hi Graham, as TV8 thread shows, I'm not the only one who's had this effect, but Peter hasn't
Talking with a very friendly mapper who always finds time to answer my questions has confirmed it's just a dollop of fuel as I shut off the throttle and dip the clutch it then ignites and in my case right as it comes out the pipes which is why I'm getting such an unsilenced and prounounced crac/Bang. Now I know for sure it's not effecting the engine, brilliant, it's way out there
As Anthony mentioned he can induce a similar effect by just shutting off at high revs, I'm pretty sure mine will do that also but I hardly ever run at high revs for very long so I'll do some tests and find out. If I've got flames I've got to see them,
Best set up the video camera
phazed said:
Apparently mine shoots flames on decelerating at the end of long straights!
I've not seen any, your to far away by then It's clearly something to do with the sleeved exhaust as I remember it doing the same thing with the standard box but it was below me and not the nicest feeling, like something hitting the car floor and my ears would feel the pressure change.
Having had a quick chat with Jason at Powers I'm now right into it
The pop & bang brigade and worse still the flame thrower gang always make me chuckle .
Because the truth is you only get pops, bangs & flames if the the ECU is over-fuelling the engine, and if you're over-fuelling your engine you're only unnecessarily wasting fuel, accelerating engine wear, and costing yourself money.
Back in the day you might use an over-fuelling strategy to cool a turbo as with the Audi Quatros we saw in the earlier video link, but even in the world of forced induction this is considered a very crude old hat strategy these days. On a normally aspirated engine running a decent engine management system with the right transient fuelling settings throttle response will be instant and there'll be absolutely zero benefit in shoving all that raw fuel straight into the exhaust.
Flames look impressive but they most definitely don't make you faster, quite the opposite in fact and here's why. Flames may be sexy but they really only say one thing.. "Inefficiency", keep in mind fuel is weight and weight is directly related to performance if you are shooting flames your wasting fuel so when you hit the track you'll need to carry more fuel (more weight) just to impress your mates with the flames.
As a consequence of this additional fuel weight you're now carrying onto the track you're lap times will be slower, so I guess it depends if you're happy to go slower just to make those very inefficient flames
. A really efficient modern race car on injection won't make flames (or very very few flames), but it will be lighter than the over-fuelling competitor carrying more fuel (weight), it will therefore win the race.
Once you've accepted these impressive pops, bangs & flames only shout "Inefficiency"
out the back of the car, you'll never view them the same again, you'll be chuckling to yourself with me as they go by in a cloud of misplaced testosterone
Get it fixed Alun, its a fault not a sense of pride mate
.Because the truth is you only get pops, bangs & flames if the the ECU is over-fuelling the engine, and if you're over-fuelling your engine you're only unnecessarily wasting fuel, accelerating engine wear, and costing yourself money.
Back in the day you might use an over-fuelling strategy to cool a turbo as with the Audi Quatros we saw in the earlier video link, but even in the world of forced induction this is considered a very crude old hat strategy these days. On a normally aspirated engine running a decent engine management system with the right transient fuelling settings throttle response will be instant and there'll be absolutely zero benefit in shoving all that raw fuel straight into the exhaust.
Flames look impressive but they most definitely don't make you faster, quite the opposite in fact and here's why. Flames may be sexy but they really only say one thing.. "Inefficiency", keep in mind fuel is weight and weight is directly related to performance if you are shooting flames your wasting fuel so when you hit the track you'll need to carry more fuel (more weight) just to impress your mates with the flames.
As a consequence of this additional fuel weight you're now carrying onto the track you're lap times will be slower, so I guess it depends if you're happy to go slower just to make those very inefficient flames
. A really efficient modern race car on injection won't make flames (or very very few flames), but it will be lighter than the over-fuelling competitor carrying more fuel (weight), it will therefore win the race. Once you've accepted these impressive pops, bangs & flames only shout "Inefficiency"
out the back of the car, you'll never view them the same again, you'll be chuckling to yourself with me as they go by in a cloud of misplaced testosterone Get it fixed Alun, its a fault not a sense of pride mate
And now for the opposite view. 
You only live once Al and lovin your dream machine as you do, who cares about pops and bangs. Its a TVR after all, not a Lexus
Plenty pops, bangs and flames from the WRC at night.
https://www.youtube.com/watch?v=TOoXoCLDc8M
You only live once Al and lovin your dream machine as you do, who cares about pops and bangs. Its a TVR after all, not a Lexus
Plenty pops, bangs and flames from the WRC at night.
https://www.youtube.com/watch?v=TOoXoCLDc8M
Richard 858 said:
Hmmm, perhaps it's just that you can't get them running on LPG!.............aha, perhaps there is a down side after all!! 
(Sorry dave, couldn't resist)
No mate, if you really want proper pops and bangs LPG is where its at.. (Sorry dave, couldn't resist)https://www.youtube.com/watch?v=PcdLA4uNGN4
Flames too...
https://www.youtube.com/watch?v=5uvXtlxzZTg
Gassing Station | Chimaera | Top of Page | What's New | My Stuff