121 replies to this topic

[MAXR]

My exhaust was repacked by BOT last week & they found the flexi was broken internally. That's now been replaced and Vibra engine mounts fitted plus an enclosed air filter system in an attempt to get my car Bedford friendly again.

[swast4]

Let me know how you get on at Bedford, is be interested.
Which enclosed filter system did you get?
R u running a 3"or 2.5"?



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[CHILL Gone DUTCH]

Cheers Chill,
Looks like I'm still going to struggle, I've got Donny on 18th of June which is 98db drive by, so will get a pair of bends made and point towards the track.
When you do your static test, do you do it at 4.5 or 5k?
Also have you got an enclosed air filter or cone type?

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sound limits are at 3/4 of rev limit and at 45 degree from exhaust at 1/2 metre at most places 

enclosed air filter really helps things on drive by 

[swast4]

Yeh, I did mine at 5k but wasn't sure if I could get away with 4.5 as on the tacho it red lines at 6.2k, but that doesn't help with drive by.

Which air filter box have you got?

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[MAXR]

Let me know how you get on at Bedford, is be interested.
Which enclosed filter system did you get?
R u running a 3"or 2.5"?

I'm running a 3" system. Not sure what they fitted as the car is still having other work being done. But, I was told it was good for 600bhp & has a cold air intake.

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[CHILL Gone DUTCH]

Yeh, I did mine at 5k but wasn't sure if I could get away with 4.5 as on the tacho it red lines at 6.2k, but that doesn't help with drive by.

Which air filter box have you got?

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how much power are you running in this car now 

[swast4]

Yeh I don't know what happened to that previous post, it has quoted something I didn't post?!?

As its on water only inj and not water /meth, I'm guessing at 430?

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[MAXR]

Yeh I don't know what happened to that previous post, it has quoted something I didn't post?!?

As its on water only inj and not water /meth, I'm guessing at 430?

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Lol! No, just 300. I think it's a standard large induction enclosure & cone that's good for 600. I'm not running any WI. I don't really want anymore power. Been there, done it & it's no more fun. Big BHP = inadequate driving skills. I also consider myself in that catergory. I should have put the money into proper tuition & much more time on track.

[swast4]

Thanks MAXR, I know what you mean about big bhp, but I'm hoping to grow into it. I've had a 200hp mx5 on slicks which was keeping up with a 250hp SC vx, so I wanted a step up, to warrant the extra money.
Lots of learning to do first though, until I can use the ponies properly.

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[MAXR]

Thanks MAXR, I know what you mean about big bhp, but I'm hoping to grow into it. I've had a 200hp mx5 on slicks which was keeping up with a 250hp SC vx, so I wanted a step up, to warrant the extra money.
Lots of learning to do first though, until I can use the ponies properly.

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It depends on who was driving the 250 BHP SC... Look up Elliot Firth on YouTube. He's on 250 BHP SC.

I've overtaken a radical on slicks...but it was driven by someone who wasn't very effective behind the wheel! Whatever you do, I'm sure you will have fun!

[swast4]

Thanks, will do, if I can ever get on track........

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[swast4]

The next step is to get some bends made like the photo below (I'll probably make them a bit longer so they clear the diffuser)

I thought I could get 2 made with reduced diameters, which will still give the same volume as the 3"exhaust as I have a 3"exhaust into 2 x 3" tips. Ive worked out that I could go as low as 2.12" exhaust tips and still have 97% volume of the 3" exhaust and so it shouldn't cause any extra back pressure probs and help with dB. Does this seem plausible or am I missing something?

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Edited by swast4, 07 June 2018 - 12:50 AM.

[CHILL Gone DUTCH]

You should of booked on the national at Anglesey
They rarely sound test there's

[Jetpilot]

There was a trackday at Oulton Park today, so I thought I'd pop down and get sound tested and hopefully get to go out for 20 mins to do a drive by.

My static was 103db and they wouldn't let me out, as they had alot of people out. (it was 4pm and I know alot pack up by then, but rules is rules)

Did anyone know what that, would equate to on a drive by with a Harrop SC?

Adam


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My Tullet was circa 96-98db static dependant where i was, still 102-103db driveby so still got black flagged.

 

I also dont subscribe at all as others have suggested that the supercharger whine peaks the drive by db's, Atoms whine like a b*tch and they dont get black flagged.

 

The Atom box might be a good place to start with some adaptation if it fits, but it will be baffled so you will loose some hp, but if the car is a track car that you cant use on track, personally a few hp loss may be worth it.

[Nev]

You asked about measuring back pressure... The way I did it was to weld in a standard lamda sensor bung into the exhaust and then screw a male nipple fitting into that. I then connected some silicone vac tube from that all the way back into the cabin, where I installed an analogue PSI gauge on the dash.

 

For reference, normal road cars create approximately 7 to 10 PSI back pressure at the red line. Mine creates about 0.5 PSI and it's one of the key reasons my car runs so cool, as back pressure has to be worked against:  more work = more heat.

 

If you pursue your logic of multiple separate expansion chambers, each one will contribute by approx 1 to 2 dB(A), some angled perforated sheet in 1 or 2 might help diffuse the pulses too.

 

GL with not getting booted off track for noise.

Edited by Nev, 07 June 2018 - 06:10 PM.

[Nev]

You asked about measuring back pressure... The way I did it was to weld in a standard lamda sensor bung into the exhaust and then screw a male nipple fitting into that. I then connected some silicone vac tube from that all the way back into the cabin, where I installed an analogue PSI gauge on the dash.

 

For reference, normal road cars create approximately 7 to 10 PSI back pressure at the red line. Mine creates about 0.5 PSI and it's one of the key reasons my car runs so cool, as back pressure has to be worked against:  more work = more heat.

 

If you pursue your logic of multiple separate expansion chambers, each one will contribute by approx 1 to 2 dB(A), some angled perforated sheet in 1 or 2 might help diffuse the pulses too.

 

GL with not getting booted off track for noise.

 

That was aimed at Swast4 BTW.
 

[swast4]

Thanks for the feedback Jet pilot, it looks like I'm still going to struggle, I'll get these tips made with 2.25 ends in them and see how I get on at Donny. Worse case I will have to lift off on the start stop straight, or short shift until I work out a solution.

I wish I was at the national, it would have been good to meet up and see what these cars can do, but I book my track days at the beginning of the year when I had my shift pattern.

Nev, it's a Shane I didn't get an extra bung welded into the exhaust when it was off as I don't fancy taking off the exhaust again, if its not a nesessity. It's a shame I can't use one of the 3 lambda points on the exhaust and a tyre guage, the ones that record max pressure.

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[MAXR]

I've used a big wad of coarse rock wool shoved down the tail pipe in the past, folded over the lip of the exhaust then with a large hose clip to keep over the edge to keep it from ejecting out the back. It worked a treat! It's a good back up plan. Brillo pads work too!

[swast4]

I got my tips made, with reduced ends.

Interesting to here about the rockwool, with the kind of pressure kicking out of the exhaust I would have thought they would be blown straight out.

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[swast4]

Tips

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