How much power does a STD backbox sap?
Discussion
The car has been mapped with linked de-cats and a straight through exhaust system and made just shy of 420bhp. I've put the STD back box on to preserve what’s left of my hearing and the car feels slower, not sure whether this is physiological. I’m going to get the car put on a dyno, at some point, but I was wondering what to expect? Is it that restrictive that the car is going to lose a lot of power?
As long as you have a 4.5 box with its larger pipe then the std tvr back box IN GOOD INTERNAL CONDITION is an excellent box for hp. At your power levels you'd be losing maybe 10hp over something like the SP box, but if you had poor quality cheap sports pipes on before chances are the std tvr back box is performing better. I suspect if it feels down on power then the back box has collapsed internally, but only a dyno run would tell you for certain, or some stopwatch times of one spec v the other..
It was a new STD backbox so it should be ok internally. It may be that the quietness is whats making me think its down on power. I'm fortunate in that the rolling road 2 miles from my house is the same one that you use so I can get pretty reliable comparisons. Fingers crossed its quiet enough for spa next year 
MackemPete said:
It was a new STD backbox so it should be ok internally. It may be that the quietness is whats making me think its down on power. I'm fortunate in that the rolling road 2 miles from my house is the same one that you use so I can get pretty reliable comparisons. Fingers crossed its quiet enough for spa next year
ooh, Where did you get it from and ££? Probably worth measuring the dB before travel. Maplin do a dB tester that is not too expensive.southendpier said:
MackemPete said:
It was a new STD backbox so it should be ok internally. It may be that the quietness is whats making me think its down on power. I'm fortunate in that the rolling road 2 miles from my house is the same one that you use so I can get pretty reliable comparisons. Fingers crossed its quiet enough for spa next year
ooh, Where did you get it from and ££? Probably worth measuring the dB before travel. Maplin do a dB tester that is not too expensive.I'm still trying to find out how strict they are at Spa, as previously they had no noise restrictions
I've got a radioshack DB tester that I "aquired" from the last pub i worked in. I've tested the car with the straight through pipes and it goes off the scale at 126db at about 3/4 rpm. I havent got round to testing the STD backbox yet.
You might have a bit of an issue with Spa. 
http://www.pistonheads.com/news/default.asp?storyI...
Neil
http://www.pistonheads.com/news/default.asp?storyI...
Neil
neilus said:
You might have a bit of an issue with Spa.
http://www.pistonheads.com/news/default.asp?storyI...
Neil
Oh c0ck!http://www.pistonheads.com/news/default.asp?storyI...
Neil
jesfirth said:
at 2/3 revs at 3/4m at 45 degress a cerb 4.2 or 4.5 with a decat and standard back box (most sprinters use this format by default) tends to be about 100dB. It is alot more on a drive by on fullthrottle though such as goodwood etc
My 4.2, straight through pipes, 4.5 backbox measured 101dB at 5,250 rpm at Snetteron this year. Which ties in with the above 
. But the chap doing the soundcheck just arranged his face to resemble a wall, so I decided best shut up jesfirth said:
at 2/3 revs at 3/4m at 45 degress a cerb 4.2 or 4.5 with a decat and standard back box (most sprinters use this format by default) tends to be about 100dB. It is alot more on a drive by on fullthrottle though such as goodwood etc
Thats good news then. Should be ok for spa if they do sort out the current situation. I'll get some of those inserts from TVR Car Parts to be on the safe side though.
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