Supertrapp silencers, power robbers?

[Al Weyman]

My car failed the noise test at Brands but they let me race as I bolted on a Supertrapp I carry with me. However in identical conditions to practise I was amazed that my lap times came down nearly 3 seconds. I thought these things were not meant to effect power much but I could actually feel the thing was down on performance and sounded crap, anyone else tried these as I was very disappointed.

Also I have a very restricted route for my exhaust system and have had to siamsese it into one 3" pipe which is obviously not helping. Now I need to get the decibles down a bit do you think it would help performance and decible readings if just before the single rear silencer I was to branch off and have an identical silencer on the other side of the car also exiting from the rear.

[graham bahr]

i know several competitors who claim a big drop in power and i seem to remember reading the same by some well known tuners.

Al could your reduction in lap times be partly due to better circuit familarity?

i often go better under race conditions when i have cars to race against, rather than in practise when effectily your racing against yourself.

with exhausts i take the same view that john cross does, the more holes in different places the noise is coming out the less the sound meter will meassure, which is why my exhaust splits with one out each side of the car.

[Dex]

I would definitely say that two silencers is the way forward. Look at it this way - if you have two exits then each is only having to deal with half as much gas - so each silencer can do half as much work (hence they can be half as restrictive)

[Notso Swift]

You say your lap times came down, but are compaining?
Do you mean came "off" by 3 sec, so slower, then I could understand.

I would go for the twin system, with a couple of nice large expansion boxes to help cool the gas. 2x2.25" will be about the same flow as one 3", but there is less turbulence as the two steams try and come together.
I would also try it with and without a balance pipe, to see if it fattened the power band or not.

Besides all of that , twins are the business on a V8

[Eric Falce]

Originally Posted by Al Weyman

My car failed the noise test at Brands but they let me race as I bolted on a Supertrapp I carry with me. However in identical conditions to practise I was amazed that my lap times came down nearly 3 seconds. I thought these things were not meant to effect power much but I could actually feel the thing was down on performance and sounded crap, anyone else tried these as I was very disappointed.

Also I have a very restricted route for my exhaust system and have had to siamsese it into one 3" pipe which is obviously not helping. Now I need to get the decibles down a bit do you think it would help performance and decible readings if just before the single rear silencer I was to branch off and have an identical silencer on the other side of the car also exiting from the rear.

Get rid of the Yank tank and buy a Fiesta,they are nearly as fast and use a lot less fuel. and make a better video platform as well.

[Al Weyman]

Yes yes sorry my times increased by 3 seconds in the race, what am I on! I got it down into the 56's Eric can you better that in the Fiesta and this was with the new suspension literally bolted on and not set up and 200 kgs to get off yet.

I cannot run a twin system rightthe way through unfortunately or I would have done, the Spohn special crossmember and Torque arm get in the way and those pieces are fundemental in getting these things to work. I'll have another look later maybe a side exiting twin system but even that is gonna be awkward.

[Eric Falce]

Originally Posted by Al Weyman

Yes yes sorry my times increased by 3 seconds in the race, what am I on! I got it down into the 56's Eric can you better that in the Fiesta and this was with the new suspension literally bolted on and not set up and 200 kgs to get off yet.

I cannot run a twin system rightthe way through unfortunately or I would have done, the Spohn special crossmember and Torque arm get in the way and those pieces are fundemental in getting these things to work. I'll have another look later maybe a side exiting twin system but even that is gonna be awkward.

best time I have done in the Fiesta is 56.4, but there ,I can give you a few years,maybe I will put the single downdraught on and come and have a go in your series.

[Eric Falce]

You can tell our age,we finish at eleven o'clock and come online from 6am onwards, mind you I find it hard to last through to eleven now!

[Al Weyman]

You are right Eric, sad isn't it? I still have to get up for work though. Incidently slightly off topic (but to hell its my thread ) we tried find you my mate still needs those TC fast road cams if you have sourced any.

Got more to come with this car now it is starting to go around corners, got a programmed electronic dizzy on order (its still on coil and points!), a larger capacity alloy rad, going to remove the 9mm glass hatch that weighs over 150lbs and replace with polycarbon, lighten the doors or go glass fibre if I can afford it (but they want $540 plus shipping form the USA) and change glass to polycarbon. Set all the corner weights and suspension ride height, improve the exhaust system then I recon I may start to get it on the pace. The car felt that much better I am encouraged to take it further now.

[greenamex2]

3 seconds sounds quite a lot to lose round Brands.

I was losing around that at Cadwell with my stupidity induced 7500RPM rev limit. That represents a reduction in BHP of about 10-15% plus a top speed down from 120ish to 100ish

Given that Cadwell is about twice as long that would mean you would be down 20-30%

[Al Weyman]

There probably was a bit of 'Ive got this in the bag no need to push too hard' creeping in once the field had settled as I new the rest of class B was behind me (mind you I nearly come unstiuck when that storming Capri caught me napping) but it was definitely down on power, even David Howard said it sounded well off. I think it was probably exaggerated because the exhaust system is marginal anyhow and this just strangled it. Look at the times on MST.

As Cadwell has more straight bits that top end loss probably really hurt you and may not have been so bad at at Brands, who knows. What year is the car Dennis?

[carsreunited]

What was the actual db reading Al? I was suprised that my new side exit system was reading 105db (up from 99db last year when it was pretty much a standard janspeed system). I took mine to custom chrome in Nuneaton who built it to whatever I required. They turned it around in 2 hours as well.

[Al Weyman]

It was 109 decibles prior to Supertrapp fitting. thing is the car has absolutely no induction roar, has a deep pleasant rumble and was not at all noisy on the track, I really wish they would come up with a better idea than this. I discussed the matter with the scrut, a very charming man who went to great lengths to help and also explained they had tried drive by but unless the cars were exactly in the same positions at the same throttle openings a camparison was impossible.

[carsreunited]

I run a TVR Cerbera as a road car and I know other owners who have had to fit the track day silencers which bring the reading down from 115db's to 102ish. They also notice drops in power of roughly 15% as someone took the trouble to test it on a dyno. Don't know if it was a supertrapp but I'm sure the same principles apply. I know it's not comparing eggs with eggs but it gives you an idea. Split system has to be the way forward I would think.

[greenamex2]

Originally Posted by Al Weyman

As Cadwell has more straight bits that top end loss probably really hurt you and may not have been so bad at at Brands, who knows. What year is the car Dennis?

1984. Why?

[zefarelly]

For the record I ran a 2 1/2" supertrap on a test day at Goodwood . . .it only reduced the noise by 3db and felt like it was holding the engine back from revving . . . . waste of money IMO

[Al Weyman]

Thats exactly what I felt, it just would not go, Zef sorry I forgot agian to bring that clutch disc in I must do it tomorrow

[Al Weyman]

Originally Posted by Denis Bassom

1984. Why?

Just wondered if it could race in the Pre 83 Post Historics or Classic Thunder. You would not be up against some of the later FWD lightweights then.

[greenamex2]

It is too modified for pre-83, and they started in 83.

Classic Thunder looks interesting but it would cost more with slicks or track day tyres, dry sump, plastic windows, plastic body panels etc just to not have a chance of beating any competitive car in class (the front running 205's in our series would be in my class).

Still this may all have suddenly become irrelevant as my dad has just found some metal in the bottom of the sump

[Al Weyman]

They have an intersting little rule introduced for 2006 that allows you to drop a class if running on list 1a or 1b which is how I managed a class B win on Sunday much to the annoyance of one of the Capri guys till I pointed out he should have been in class C as he was on !b's as well (read them rules guys) I have a well designed sump and an Accusump so do not need dry sumping, if you do by evidence of metal in your oil then it may be a worthwhile investment and at least the rules allow it.

There were two notabable quick cars out there sunday, a droop snoot Firenza and a 1602 BMW, the BMW is probably on par with your car and it was flying, I could not catch him!

[greenamex2]

Unfortunately that still means a 2.1L 240BHP 170ftlb 700Kg Pug 205 runs in the same class as a 1.6L 218BHP 125ftlb 800KG Corolla!

I have an accusump but if I fit list 1b or better tyres I still need dry sumping (I know, I tried, I blew up). In short, my engine is one big design fault, the result of the Japanese copying a BDA and then thinking they knew better.

My dad has just finished check the bearings and they look fine, sounds like he didn't clean the engine out properly after the Mallory blow up. 'Phew'.

Back on the subject of the thread, I have an inverted holed cone arrangement in my tool box for when I fail noise testing. It takes a couple of minutes to swap over (two bolts), reduces noise considerably and can be 'tuned' with the aid of a hacksaw/angle grinder. It's main benefit over the supertrapp arrangement is you can control to amount of 'straight through' gas rather than having the whole lot have to do a 90 degree turn to exit the exhaust.

I guess you could probably tune the supertrapp similarly with the aid of a battery powered drill!

[Al Weyman]

No i doubt you could as it works as a series of discs, the more you put in the noisier it gets.

[greenamex2]

Even with lots of discs the gas still has to to an abrupt 90 degree turn to get out of the silencer, and has a wall right at the end of the exhaust bouncing the sound waves back in.

I am just suggesting that perhaps there is a more 'elegant' and efficient way of meeting the 105dB.

Out of interest, what was the figure WITH the supertrapp fitted?

[Paul V]

Have you got any pictures showing your current set up?
I would give some idea as to what could be tried.

You can always pop it on its side if doing it from underneath is too tricky...

[Al Weyman]

The sound man who incidently was very helpful, said he was happy to see the Supertrapp on and would not bother to retest so I don't know. I am sure it would have met the test though as it was definitely quieter.

I will do a sketch later Paul.