chironwsc

Hi Guys



I am new to the forum and what a fantastic forum it is so much information on here!!



We would like to fit a 3 or 4 rotor engine into a road race car but I am worried about the noise problems associated with the rotary engines.

Not only would the engine be a 3or4 rotor but also peripheral port just to add to the noise issue!! Most of the championships in the UK now have noise limits, we would need run the engine to a 102dba noise limit. The noise test is done 20inch at 45deg away from the silencer exit.



Now my question is will this be possible to silence a non turbo 4 rotor race engine to 102dba without losing lots of power? Are there any tricks that people have found to help quieten rotary engines for racing?



We normally build our own silencers they are the typical race type re-packable straight perforated tube type fairly free flowing. Would 2off 7"x22" straight perforated tube type silencers do the job?

We did make a silencer a while ago for a customer which had an 80deg bend in the perforated tube this made a massive difference to the noise approx 12dba but we have not checked what power loss having the bend in the tube caused. Would a similar type of silencer with a bend in the perforated tube be too restrictive for a Rotary engine?



I would very much appreciate any thoughts and comments or just throw some ideas my way.



Kind Regards

Henry Nickless

Chiron WSC

Lynn E. Hanover

In the US that requiement is at 50 feet from the track centerline on the outside of the track (where it would affect those folks on the next property) and at a place where full throttle is typical. And then the level is 103 Db.



So, is your measurement on a dyno at full throttle? at idle, or come other situation?



I have a big Borla 4" ID stainless packed perf tube muffler, with the outlet on the right side of the car to the inside of the track, and pointed at the ground. We make 103 easy with this setup with a 2 rotor 12A engine.



With a three rotor it would be a problem. At least another muffler beyond the perf tube job, perhaps one that breaks the stream into two elements and has them run into each other, along the lines of a Flowmaster. A big suitcase looking thing used on street V-8s. Would need to be at the very end of the system to keep the heat down, and the hammering of the supersonic pulses dropping to subsonic. The tip pointed at the ground is a big help as well. Possibly a copy made in stainless.



Use NA rotor housings and leave the splitter in the exhaust ports.



Lynn E. Hanover

Lynn E. Hanover

In the US that requiement is at 50 feet from the track centerline on the outside of the track (where it would affect those folks on the next property) and at a place where full throttle is typical. And then the level is 103 Db.



So, is your measurement on a dyno at full throttle? at idle, or come other situation?



I have a big Borla 4" ID stainless packed perf tube muffler, with the outlet on the right side of the car to the inside of the track, and pointed at the ground. We make 103 easy with this setup with a 2 rotor 12A engine.



With a three rotor it would be a problem. At least another muffler beyond the perf tube job, perhaps one that breaks the stream into two elements and has them run into each other, along the lines of a Flowmaster. A big suitcase looking thing used on street V-8s. Would need to be at the very end of the system to keep the heat down, and the hammering of the supersonic pulses dropping to subsonic. The tip pointed at the ground is a big help as well. Possibly a copy made in stainless.



Use NA rotor housings and leave the splitter in the exhaust ports.



Lynn E. Hanover

chironwsc

Hi



Thank you for your reply.



The static noise test is at 3/4 revs so approx 7000rpm needs to be 102dba. We also have to meet the 102dba on drive by they don’t give a distance from the car for the noise meter.

What are the approx dimensions of your silencer, length and diameter?

Would a 13b make much more noise do you think than a 12A?

Also the exhaust port splitter is this part of the housing or a removable part we have very few non turbo 13b engines in the UK so don’t have any experience of the exhaust port splitter. Does the splitter affect engine power very much if used?



Thanks

Henry

chironwsc

Any one any experience of the Spin Tech mufflers for racing use? They seem to work ok on 20b engines used in aeroplanes.



Henry

Maxt

If you choke a p-port with to much muffler, power falls off like a cliff.. From playing with my own p-port car, the very end muffler and opening has the most effect on the overall noise. Adding presileners midway with perforated cores did nothing to the noise of the motor, absolutely nothing. I have a pop in silencer I drive with most of the time on the street, sometimes highway I take it out.

I think you may be wise to go 4 rotor, then muffle to meet track levels.Once you choke down the 3 rotor you may not be competitive power wise, if you read some of the older articles on the Mazda race cars in Gt and Imsa, they had a very difficult time meeting track noise levels, and making enough power to compete.

The scoot car runs cats, air injection, and met Japans street noise level, all corked up it did 370 rwps, it would probably do 425ish at track noise levels, figure on 100-115 rwhp per rotor with a muffled p-port.

chironwsc

Hi



Thank you for your reply.



Do you know what the IMSA /GT noise limit was in the day? What engines ran in the IMSA/GT cars are we talking 2,3or4 rotor?

That’s interesting what you say about the pre silencer. So for the 4 rotor maybe it would be an idea to split the 4 pipes in to 2 silencers not sure how this would affect power that’s something for the dyno I guess.

Are you talking about the Scoot 4 rotor car?



Thanks

Henry

scot62

Hi Henry,

Welcome to this forum as I'm from UK, what kind of model is your a FB,FC,FD or FE?

Mine's an FC with13Bpp motor( still building it up) as prevouis with13Bbp with 2" dual header/pipes all way from the engine to driveshaft then joining into one trumpet 3" to4"( aboot 12" long) then single muffer 24"x10" diam(95db to 105db depends on near building or in open area) and lynn 's right about tailpipe pointing to the ground to dump its sound

The splitter's better to leave it in the engine, very small number of hp's loss and it's aid to cut sharp sound.

your's best bet is go and see Pip from WGT or Carl from Haywardrotary.

REgards

Ian

Lynn E. Hanover

The splitters take off about 3 HP per housing. They are removable with difficulty, as they are pinned in with a double roll pin. Removal from a junk housing is easy, as you just drill a groove down to the pin and drive the liner out with a punch. To install the liner in the race housing you would want to remove the roll pin from the nonsplitter liner, so as to protect the housing. You can also do both the same way, and the header flange will hold the liner in place. Or, once you have the roll pin out, you can replace it with a length of drill bit shank, that will be held in place with silicone, and after assembly the irons will prevent the pins from moving. You can sort of drill out the pins with a concrete drill that has a carbid tip.



It actually breaks the pin into tiny chunks, but the hole is empty when you finish. The splitter takes out about 3 Db right at the top, so it makes a big difference on the sound meter. The 102 figure is actually down quite a bit from our 103 and 105 Db. You are on a nearly vertical line on an exponential graph.



The Borla is 22" long and has a 4" perf tube in the center with 5 smaller perf tubes packed in the 4" tube. The car is making only 100 Db with the Borla and the exhaust outlet away from the sound meter.



Before the Borla we had a number of mufflers, and two tail pipes that we could switch, so the outlet could be out either side of the car depending on where the track had the sound meter set up.



Borla does not make this one any more, and deny that they ever made this one, maybe just the 4" pipe size.



The Flowmaster was very effective as long as it is at the end of a long system. We melted the first one when it was mounted about even with the driver location wise. It held up fine just behind the rear axle.

You can hammer one to death, and all of the baffles will end up in the rear of the shell blocking the outlet. The shell swells up like a giant pillow.



In this picture you can see the 4" outlet just ahead of the rear wheel.



Lynn E. Hanover

j9fd3s

check out pix of the 787b. i'm not sure if its 102db, but it does have mufflers, and its not really loud