4722 replies to this topic

[Ormes]

How much does the pulsing account for the noise at idle?  Can other things such as the map and/or cams be changed to help without too much compromise?

 

 

[Nev]

How much does the pulsing account for the noise at idle?  Can other things such as the map and/or cams be changed to help without too much compromise?

 

 

 

Good question, not sure really, but I suspect quite a lot (the peaks anyway). Unfortunately the lolloping idle is a physical manifestation of the cams, neither the CS map or the new map and ECU have been able to tame it. The only way would be to put verniers on and fiddle about but that might negatively impact power (and I can't be arsed!).

 

 

[Nev]

I've just got in from building design #3. Couldn't test it as it's a bit late and it would have been a bit un-neighbourly of me.

 

I built this step quite restrictively, but it can be de-restricted by replacing some of the solid sheet with more perforated sheet. At the moment the section is held with a few bolts and is a "cartridge system" that I can pull out if I want.

 

I need more HSS drill bits, they don't seem to last long! Also all my welding today was without gas, not easy to arc up and quite messy, gotta wait till Monday to get some more.

 

The bulk of the work is done now though. Hopefully tomorrows idle test will drop to 100 dB on C filter. *fingers crossed*

 

I've spent ages on this, probably something like 30 hours in the garage now and about the same planning/buying/designing, it better bloody be worth it !

Edited by Nev, 03 December 2016 - 08:21 PM.

[The Batman]

do you have a target dB nev?

[stu8v]

You need to use a slow speed for drilling stainless. Lots of cutting compound and don't let the drill bit skid.

[oblomov]

Haulfrauds were selling cobalt sets quite cheaply recently Nev. I bought a couple of sets which I've just used on 4mm stainless and they were OK slowly with plenty of of Trefolex.

[Nev]

do you have a target dB nev?

 

Hmm, well being able to pass the 105 dB noise test at Castle Combe would be the main thing (and not getting kicked off on drive by). It's local to me and would suit Nipper to some extent. To achieve this I think my idle needs to be around 100 dB.

 

If I think it's quiet enough I will install it in the car (just tack welded) and limp the car over to CC to be tested. If it passes (with a bit of margin) then I'll weld it all up.

 

If it passes the static test then the neighbours will breath a sigh of relief too and maybe I could drive without earplugs.  

Edited by Nev, 04 December 2016 - 08:06 AM.

[Nev]

You need to use a slow speed for drilling stainless. Lots of cutting compound and don't let the drill bit skid.

 

Thanks.  

[Nev]

Haulfrauds were selling cobalt sets quite cheaply recently Nev. I bought a couple of sets which I've just used on 4mm stainless and they were OK slowly with plenty of of Trefolex.

 

I've just bought some Heller 4, 5, 6mm ones off eBay as they are the ones I predominately use. Thanks.  

[Ormes]

You need to use a slow speed for drilling stainless. Lots of cutting compound and don't let the drill bit skid.

  Thanks.  

I've been doing lots with the drill press of late and only in the last session did I use cutting compound for the first time ever. I'll never go back to dry cutting/drilling!

[FLD]

I use carbide drills on a slow speed. Works a treat but the drills are expensive. Sent from my iPhone using Tapatalk

[stu8v]

It would be more realistic if you revved it to 2/3 of your rev limit and tested at 1/2 meter.

[The Batman]

Yeah, list then you will know if you pass static test 100db on idle seems unlikely to pass that Although I have seen a load of really loud cars on idle that suddenly harness the power of the noise gods and are quiet at 2/3rds!!!

Edited by The Batman, 04 December 2016 - 12:57 PM.

[Ormes]

It would be more realistic if you revved it to 2/3 of your rev limit and tested at 1/2 meter.

Bear in mind that half of Nev's battle is keeping the neighbours happy... "Will you stop revving the hell out of your car on the driveway please?..." "I'm doing it for you... to make my car less noisy" <Punch>

[Nev]

It would be more realistic if you revved it to 2/3 of your rev limit and tested at 1/2 meter.

 

Yep you are right, once the glass wadding arrives I will install it and then get the g/f to rev it up a bit with me at the back end taking readings. I did blip the throttle a bit today (and the noise seemed ok at 3500 (by ear)) and the burble and pops sounded lovely, nicer sound than the old exhaust.

 

Today I installed some turbulence strips due to my findings from the wool strand test: https://sites.google...gn/05-build-log

 

Getting some argon tomorrow so I can actually weld without splattering my jumper in molten metal !

Edited by Nev, 04 December 2016 - 07:44 PM.

[Nev]

Although I have seen a load of really loud cars on idle that suddenly harness the power of the noise gods and are quiet at 2/3rds!!!

 

Nipper is one of those cars I think, mid RPM noise is usually not much more than static, 6500 RPM+ does get a bit worse though (historically anyway).  

Edited by Nev, 04 December 2016 - 07:33 PM.

[Nev]

 

 

You need to use a slow speed for drilling stainless. Lots of cutting compound and don't let the drill bit skid.

  Thanks.  

I've been doing lots with the drill press of late and only in the last session did I use cutting compound for the first time ever. I'll never go back to dry cutting/drilling!

 

 

What cutting compound do you guys use? Up to now I've just been squirting the drill hole + bits with WD40, which is probably not the best thing.  

[The Batman]

Although I have seen a load of really loud cars on idle that suddenly harness the power of the noise gods and are quiet at 2/3rds!!!

  Nipper is one of those cars I think, mid RPM noise is usually not much more than static, 6500 RPM+ does get a bit worse though (historically anyway).  

It happened to me at sNet a while back, couple of race cars pulled up that where stupidly loud idling and got passed no problem so at this point I was like ah no problem then... I was 1db under the static lol! I then changed to single exit (1 dummy for looks) and it knocked 3 or 4 dab off

[Nev]

I think wild (long duration + high lift) cams is what makes a lot of idle noise. Strangely my turbo seems to do little to albeit the noise either. I was told that when I was going round Llandow at full pelt that I wasn't any noisier than the Caterhams.

 

Makes me wonder if my tail pipes will add noise, I should really install those on the next noise test to see. I am hoping the wadding will cut the higher/mid frequencies a good bit, though I hope it can survive all the explosions I get on overrun, so I don't have to keep replacing too often.

Edited by Nev, 04 December 2016 - 08:01 PM.

[The Batman]

If you fitting 3.5" pipe just have one single 3.5" pipe