does octane affect pops and bangs?
Discussion
Hi All,
I raise this issue/question having read some posts about how to get the most fireworks from the exhaust.
So, if the pops and bangs are caused by unburnt fuel being dumped into the exhaust which did not detonate from the spark under throttle or the compression in the cylinder and then being ignited in said exhaust- will using higher octane petrol increase the fireworks?
My sugestions that it would, is based on the fact that high octane fuel better resists detonation caused by pure compression which would leave more unburnt high octane fuel to enter the exhaust compared with normal 95 octane.
Does this theory hold water??
thanks for your thoughts
I raise this issue/question having read some posts about how to get the most fireworks from the exhaust.
So, if the pops and bangs are caused by unburnt fuel being dumped into the exhaust which did not detonate from the spark under throttle or the compression in the cylinder and then being ignited in said exhaust- will using higher octane petrol increase the fireworks?
My sugestions that it would, is based on the fact that high octane fuel better resists detonation caused by pure compression which would leave more unburnt high octane fuel to enter the exhaust compared with normal 95 octane.
Does this theory hold water??
thanks for your thoughts
robsco said:
Forgive me if I'm wrong, but shouldn't you be using 98 or 99 octane fuel anyway, or does the Speed 6 have mapping which adjusts to both?
Rob,My Tuscan handbook specifically states that 95 RON is OK for 'normal' use, but reccomends that 98 RON is put in for track use - I guess to address the detonation issue with a very hot/loaded engine.
Sticker adjacent filler cap reiterates above.
Nick
I've never used 95 fuel, but I always use super plus a healthy does of Millers additive in my Chim. It snaps, crackles and pops like it's the 5th November when lifting the throttle. I can pop 'on demand' when going past an appreciative crowd. Works especially well in a low(ish) gear down a steep hill 
Terribly childish I know.
Terribly childish I know.finestjammy said:
I've never used 95 fuel, but I always use super plus a healthy does of Millers additive in my Chim. It snaps, crackles and pops like it's the 5th November when lifting the throttle. I can pop 'on demand' when going past an appreciative crowd. Works especially well in a low(ish) gear down a steep hill Terribly childish I know.
Do you have to remove cats etc to get noises from the RV8 exhaust? or can a standard set up produce some noises? I can hear a few barbles within my car on overrun, but when I ask people who are following there there is no sound from outside the car (mine is totally standard). Terribly childish I know.quattrophenia said:
Do you have to remove cats etc to get noises from the RV8 exhaust? or can a standard set up produce some noises? I can hear a few barbles within my car on overrun, but when I ask people who are following there there is no sound from outside the car (mine is totally standard).
As far as I know my car just has a sleeved silencer modification. Looking at the latest MOT emissions it appears that there air is probably getting into the exhaust. I can only assume that this is the reason, intentionally or not, that I get the pops and bangs. I know that the main cat is in place but couldn't confirm if the pre-cats are still in or not. The main cat/y piece has been wrapped though, which I'm guessing transfers more heat toward the rear of the exhaust to help ignite the unburnt fuel.
Here is a little clip, not very good quality, where you can hopefully hear the pops when I back off the throttle: http://www.youtube.com/watch?v=_p_yUY003hQ
It does it a lot more when actually driving, and even more so since changing the HT coil, ignition amp, dizzy cap, rotor arm and stepper.
nawarne said:
Rob,
My Tuscan handbook specifically states that 95 RON is OK for 'normal' use, but reccomends that 98 RON is put in for track use - I guess to address the detonation issue with a very hot/loaded engine.
Sticker adjacent filler cap reiterates above.
Nick
Aah right, I see. I was being presumptive really, as my AJP's sticker states not to run the car on anything short of 98 RON.My Tuscan handbook specifically states that 95 RON is OK for 'normal' use, but reccomends that 98 RON is put in for track use - I guess to address the detonation issue with a very hot/loaded engine.
Sticker adjacent filler cap reiterates above.
Nick
robsco said:
Aah right, I see. I was being presumptive really, as my AJP's sticker states not to run the car on anything short of 98 RON.
I think you will find TVR put 95 and 98 stickers on depending which sticker came to hand as for every owner with 95 there Is one with 98 no matter the engine. 
C3BER said:
robsco said:
Aah right, I see. I was being presumptive really, as my AJP's sticker states not to run the car on anything short of 98 RON.
I think you will find TVR put 95 and 98 stickers on depending which sticker came to hand as for every owner with 95 there Is one with 98 no matter the engine. 95 RON for normal use, but for trackdays use 98 RON....or words to that effect.
Nick
still can a 
long time no see
I still remember seeing pics of your flame thrower lol I heard a Cerbera a few months ago make what I could only described as a detonation!. I was in my car about 50 yards behind and as he slowed at about 30mph the noise made me jump from inside my car! SP6 sports exhausts do certainly seem to be more theatrical,shall we say, than the RV8.
I would like to make mine a little noisier, but for every car that sounds better for the mod, there seems to be other cars that sound OTT and even agricultural!
I would like to make mine a little noisier, but for every car that sounds better for the mod, there seems to be other cars that sound OTT and even agricultural!
MPoxon said:
I believe it does make a difference. I definitely notice a marked increase in pops and bangs running on Shell V-Power (99RON) compared to BP Ultimate (97RON)
I agree but I'm no chemist to explain why but I get more of a rumble and soft pops and bangs with BP. With Shell its more of a crack, bang, staccato effect.Which is better for the engine?
C3BER said:
I agree but I'm no chemist to explain why but I get more of a rumble and soft pops and bangs with BP. With Shell its more of a crack, bang, staccato effect.
Which is better for the engine?
I can only assume the difference is due to the higher RON of Shell. I wouldn't have thought the different detergents would produce different sounds.Which is better for the engine?
quattrophenia said:
Do you have to remove cats etc to get noises from the RV8 exhaust? or can a standard set up produce some noises? I can hear a few barbles within my car on overrun, but when I ask people who are following there there is no sound from outside the car (mine is totally standard).
On the RV8 it is the older 'flapper' AFM (earlier Wedges) that give the pops and bangs.None of the Wedges had cats, but later ones had 'hotwire' injection systems like Chims, and no pops and bangs.
Flapper system 400SE:
http://www.youtube.com/watch?v=ZeQQwsgy8kg&fea...
Hotwire 400SE (mine):
http://www.youtube.com/watch?v=w8pByU4LWFI&NR=...
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