SVA problem: really need some HELP !

[Cobra power]

Hi all,

Last item on SVA failure list: noise level. I have side pipes from shiny bitz, they have already been back to Roger on the first failure, he prepared them for low noise. Run 400hp SBC.

At retest: left 103.9db right 101.9db (unclear what causes the difference). Measured at 3225rpm (max power stated at 4300rpm). If I understand the difference this might help reducing the left enough. Any ideas?

I have outsourced the whole procedure to a kit car workshop because I live in the Netherlands.

Just got an email how I want to proceed. My problem:
- quoted max power RPM's seem high, but nothing i can change right now
- roger (shiny bitz) tells me he has restricted the sidepipes as far as possible and cannot believe the pipes are this loud
- kitcar workshop can stuff the pipes some more but expect that this will not reduce the noice enough wihtout choking the engine

So now it's up to me! Change timing? Change mixture? What causes the difference?

Really need some help!

Thanks

[Grease Monkey]

Mine SVA'd the first time at 102db, just over the limit.

I shoved some wadded up GRP matting rolled into chicken wire up the pipes and it dropped to 94db.

Drove like a pig and stalled each time the tester did the brake tests, but it passed and as soon as it got home i whipped the crud back out.

[rich427]

Hi
If you have an electronic rev counter adjust it so that it reads higher revs that way when you stick it on the itstructed rev speed at test it is actualy runing slower therefore quieter.:thumb: :thumb:

[Cobra power]

Originally Posted by rich427

Hi
If you have an electronic rev counter adjust it so that it reads higher revs that way when you stick it on the itstructed rev speed at test it is actualy runing slower therefore quieter.:thumb: :thumb:

Hi Rich,

That's an idea. I have an electronic rec counter, SMiths Classic. If i can recall correctly I can program number of cylinders. 4-6-8. Not sure if setting to 6 will increas or decrease RPM?

Could you help?

[Syholl]

Dropping it to number 6 will increase the reading, which is what you want, but it will be very noticeable that this is what you have done, especially at idle...

[dave]

Good idea, only if they do not suspect and use their own means of measuring the revs.

[Cobra power]

well than that's not the solution.

I'm still very surprised that the sidepipes are so loud. testing 3225rpm might not be the lowest, but I'm told the pipes have been prepared to be very very restrictive and therefor very quite. Still the db have not dropped significantly.

Any other idea's? timing?

[rich427]

Hi
I to have smiths clasic rev counter there is a adjusting screw by all the switches don't change it to 6, all you need to do is adjust the screw with the engine running keep it mid rang and just adjust it so its recording slower..:thumb:Hope all goes well.:drive: :drive: :drive:

[TINKA]

Your problem is you have given a max power RPM far too high. You are going to have great difficulties getting any exhaust through at that rev's. You need to claim ignorance and say you have spoken to the engine builder and the max power is at 3,500rpm. This is what I and most other people quoted and means the test is done at about 2,000rpm. If they wont accept you gave them the incorrect rpm power ratio not sure what you are going to do.

[Cobra power]

Originally Posted by TINKA

Your problem is you have given a max power RPM far too high. You are going to have great difficulties getting any exhaust through at that rev's. You need to claim ignorance and say you have spoken to the engine builder and the max power is at 3,500rpm. This is what I and most other people quoted and means the test is done at about 2,000rpm. If they wont accept you gave them the incorrect rpm power ratio not sure what you are going to do.

As I understand the SVA has become much smarter and does not accept unreasonbly low RPM figures and used their own material to find the correct numbes. I just got of the phone with performance unlimited (engine builder) who's telling me that 4300 rpm is already conservative (which I didn't want to hear)