exhaust noise levels
Discussion
I'm about to have the Offord box change and thought I'd record and take dB reading of before and after.
I have a completely standard exhaust and have the following (very quiet) dB reading so far: -
Idle 98dB
2000 RPM 105dB
2500 RPM 106dB
3000 RPM 105dB
4000 RPM 107dB
All measured at 45 degrees and between 0.5m and 1m
As you can see 2.5k has a resonance that pushes the level up slightly from 2k & 3k.
Question for those that have the Offord box, do you feel the levels have this same trend at 2.5k?
PS For those that are interested I'll be posting the video recordings of before and after next week.
Edited to make more clear.
I have a completely standard exhaust and have the following (very quiet) dB reading so far: -
Idle 98dB
2000 RPM 105dB
2500 RPM 106dB
3000 RPM 105dB
4000 RPM 107dB
All measured at 45 degrees and between 0.5m and 1m
As you can see 2.5k has a resonance that pushes the level up slightly from 2k & 3k.
Question for those that have the Offord box, do you feel the levels have this same trend at 2.5k?
PS For those that are interested I'll be posting the video recordings of before and after next week.
Edited to make more clear.
Edited by davetherave1970 on Wednesday 3rd January 13:09
The idle is spot on the same as mine (well during a impromptu test with a decible meter outside the pub with Mr and Mrs MadMark)
Can't say about the other readings other than its bloody loud. As mine is off the road for the winter I have been running it up to temp for 20mins once a week and i will be amazed if I get through the winter without the neighbours complaining
Can't say about the other readings other than its bloody loud. As mine is off the road for the winter I have been running it up to temp for 20mins once a week and i will be amazed if I get through the winter without the neighbours complaining
clive f said:
don`t worry, daves a very technical guyHim or me?
puffsorted2 said:
Can't say about the other readings other than its bloody loud. As mine is off the road for the winter I have been running it up to temp for 20mins once a week and i will be amazed if I get through the winter without the neighbours complaining
So no regrets then
clive f said:
don`t worry, daves a very technical guyHe means me...
If you only tested once at each point, then there will be an amount of error associated with each reading. For instance (just to pick a couple of random things) a misfire or over-fuelling pop could interfere with what you're really trying to measure, or the meter reading could be laggy etc... I wondered if this sort of error could account for some of the differences in readings, meaning there is much less (or more) resonance than you think there might be.
This is usually where I get told that this is the average readings from 10 runs so any errors have been minimised...
dnb said:
clive f said:
don`t worry, daves a very technical guyHe means me...
If you only tested once at each point, then there will be an amount of error associated with each reading. For instance (just to pick a couple of random things) a misfire or over-fuelling pop could interfere with what you're really trying to measure, or the meter reading could be laggy etc... I wondered if this sort of error could account for some of the differences in readings, meaning there is much less (or more) resonance than you think there might be.
This is usually where I get told that this is the average readings from 10 runs so any errors have been minimised...
I see. Makes sense.
The meter was on fast / c weighting and only one reading was taken over 10 secs (for each RPM)
Over the 10 secs the meter settled on the figures so not exact.
Best I could do at the time.
davetherave1970 said:
clive f said:
don`t worry, daves a very technical guyHim or me?
puffsorted2 said:
Can't say about the other readings other than its bloody loud. As mine is off the road for the winter I have been running it up to temp for 20mins once a week and i will be amazed if I get through the winter without the neighbours complaining
So no regrets then
lol no, but am shocked by the noise when I stand behind it with the engine spinning at 3000RPM - doesn't sound that loud from sitting in the drivers seat
I have read this post with interest. I have removed the baffels from my exhaust and replaced them with 2 cherry bombs. It now sounds amazing from within the car and friend who has followed me has likened it to a Spitfire on full chat. The only problems I have are that it now sets off car alarms and my neighbours though it was really nice at first but I now have to leave the village on idle until on the country roads. The exhaust note was one of the many reasons for buying a TVR in the first place.
My Griff is in Offords having the conversion today 
although on the way up there this morning it missed a beat three times 
Twice on the M11 and once just 5 mins from Offords. It was like switching off then straight back on again about a second later. No dash lights came on and all electrics stayed on ok.
They will be looking at this as well today but first thoughts are ignition amp
although on the way up there this morning it missed a beat three times Twice on the M11 and once just 5 mins from Offords. It was like switching off then straight back on again about a second later. No dash lights came on and all electrics stayed on ok. They will be looking at this as well today but first thoughts are ignition amp
crackedfinger said:
Mine is standard too - had a reading at Goodwood (who were being quite strict) and got 99dB @ 4500-5000 RPM. Bearing in mind all the varing factors which can affect noise readings, I do find it amazing how varied standard exhausts are.
As the std. test is at 2/3 revs and the max revs on the RV8 cars is around 5,800 then you don't need to rev beyond 3,800 during the noise test. Well i made it home. Didn't miss a beat on the return trip. Ignition amp was replaced so hope this was the problem. Time will tell.
As for the noise from the modified exhaust.......brilliant. The note is soooo much better and to the ear it's not too loud (can it ever be?). I'll have to meter the sound levels at the weekend to see exactly how much louder it is!
I'll also record the noise then post before and after recordings for interest.
Can't believe how cheap this mod is!
As for the noise from the modified exhaust.......brilliant. The note is soooo much better and to the ear it's not too loud (can it ever be?). I'll have to meter the sound levels at the weekend to see exactly how much louder it is!
I'll also record the noise then post before and after recordings for interest.
Can't believe how cheap this mod is!
Edited by davetherave1970 on Thursday 4th January 21:51
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