List of basic design goals

[drivetrainUW-Platt]

We had the same suzuki stock all aluminum muffler that everyone runs...we didnt pass sound the first time till we baffled it.

It has a lot to do with your headers to. Also, our engine wouldnt quite rev to redline due to lack of tuning, so that prob made it run rough and make more noise.

[Chris Allbee]

I feel sorry for those teams who think that designing your own is a waste of time. Seriously, if you have everything else taken care of then feel free to dabble in designing your own muffler. You will learn a lot and last I checked that was the point of this competition.

As far as your decade of sports bike expertise, did you ever look up the procedure by which those mufflers are assigned a 85dB rating? Its not like the sound test we go through at competition.

And again the tuning aspects are different as well. Have you looked into the effect the restrictor has on volumetric efficiency at high RPMs? Given that, did you then consider the effects of the exhaust "back-pressure" on trying to improve that VE?

Next, what is the exact set-up you are running? Engine? Runner lengths? Exhaust configuration? Plenum size? any head modifications? These all play a part in the sounds emitted from the engine (i'm sure there are others).

Point is, just because it works on one application doesn't mean that it will have the same effect on another system. So don't feel bad for the rest of us.

[afroney]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">For all you naysayers that want to build your own muffler, or use a Yoshimura muffler, bring a stock muffler as a backup. It'll make you life a LOT easier at competiton </div></BLOCKQUOTE>


Also, take into consideration things that aren't directly muffler related, but can cause a team to fail noise. Our aluminum firewall last year rattled pretty badly against the chassis, causing us to nearly fail noise. We even had a nice stock Yoshi muffler

[Mechanicaldan]

Chris -

You make a LOT of valid points, but my original point of the post is for a SIMPLE and BASIC design list for 1st year teams. I would think that on a list of 50 important items to a judge, that designing your own muffler is pretty low on that list. Yes, you need to understand what the lengths and diameters of the exhaust system have to do with the curve of your powerband. If designing your own muffler were a TOP 10 item for the design judges, then more top placing teams would do so, but they don't, they buy one.

Mike - I'll take your word for it, but I find it really difficult to believe that a stock multichambered muffler (Honda F3) won't pass the noise test. Of course, that's a steel muffler, not an aluminum one, and you said it might have had a lot to do with your header and tuning. I've been to competition and talked to other teams that have been very happy when they passed noise with a stock muffler. One team I remember used a 600RR oval undertail muffler. Anyone else NOT pass noise tech with a stock muffler? Mike, I think your team is the one exception.

I understand that there is a LOT to consider. I was trying to make a basic list for 1st year teams to consider. The point is to get a car built from scratch. No starting point other than a blank screen and an empty chassis table. Team members that struggle with the difference between caster and camber. THAT'S A HUGE UNDERTAKING. It's easier when you have a car that has been to competion, and you can refine it. Members then understand concepts and can apply them more thoroughly for improvements.

I am VERY open to suggestions for a 2nd year team list. I would agree that designing a complete exhaust system would be on this list, along with a MegaSquirt ECU, or any other fully adjustable ECU.

Regarding building on concepts, I will point to my team specifically from 2002 when I joined in the Spring semester to last year. We did not have a running car at competiton for 2002. It was a 600 lb beast with a lame attempt at aero. It sucked. I helped my team work on the car for 4 days trying to get it to run. We placed 1XX something, as I don't even remember. Our team pledged to never have that happen again. We went back to basics. No aero. No traction control. No electronic shifting. The next year I was engine team leader, and our team finished 22nd. The next year's car was even better, but DNFed endurance because of a leaky differential. (Design with o-rings to seal it!) The following year ISU placed 18th. Last year ISU placed 7th. Building and improving upon concepts that work, instead of going crazy with complicated systems. Last years team still didn't have aero, or electronic shifting, or traction control. They did have a team that understood concepts, and could drive a car well.

I feel that if a 1st year team were to follow this list and score in every event, then they would have been one of only 44 teams at the 2006 FSAE competition to do so.

Why aren't there more teams finishing every event? It's because there is so much to do in so little time. So, for a 1st year team, I think SIMPLE and BASIC is best. Slap a stock muffler on the car, and tell the judges you justified the decision for it because it didn't break and allowed the few remaining members in the Spring to learn to test and drive the car weeks before coming to competiton for the 1st time.

[Biggy72]

We couldn't pass with a suzuki muffler.... we were anywhere between 115 and 118 db pretty much no matter what we did. A super trap system is great for a 1st year team because it is adjustable if you can't pass sound.

[Mechanicaldan]

OK, I was wrong, and wasn't specific enough. Let me restate number two.

2. Fuel injected 4 cylinder motorcycle engine with stock muffler (steel, multichamber, ie Honda F3) to pass noise tech on first try. Don't use stock aluminum Suziki mufflers as teams have failed to pass noise tech with these mufflers.

[Chris Allbee]

Missing the mark again there Dan. It wasn't about just the Suzuki being insufficient to pass tech. The argument revolved around the complex interactions of the entire induction and exhaust systems and how those affect the final sound pressure levels of the system. If your system is different from stock then your noise levels and spectra will be different as well. It may so happen that the system you guys came up with still worked well with the stock system, but that doesn't mean it will work with everyone else. There is more than one way to approach each problem. Your way isn't the only way.

2. Fuel injected 4 cylinder motorcycle engine with stock muffler (steel, multichamber, ie Honda F3), Iowa State's intake, exhaust, fuel/ignition map, frame (and anything that would rattle because of the motor), and the exact weather conditions on the day Iowa State passed tech to pass noise tech on first try. Don't use stock aluminum Suziki mufflers as teams have failed to pass noise tech with these mufflers.

That should just about cover it. you're welcome for the clarification.

[mtg]

I think Dan's on the right track- his point was to suggest first year cars are ridiculously simple and use general design basics that have a high probably of working on the first try.

On the subject of details, I'll vouch for a stock Suzuki muff by itself not necessarily passing tech. It seemed to me that there is a strong correlation between exhaust loudness and the length of pipe between the collector and the muff.

[Buckingham]

From my experience the Suzuki engine itself is hard to pass sound with. When our team switched from a FZR to GSXR many years ago we were amazed at how the GSXR was 10-15 dB louder across the board (with no muffler, the same muffler, just about every combination we measured).

[Hot Rod JayRad]

I also think Dan has the right idea. Our 2nd year car has been hard to pull off because we tried too many design improvements for the number of people on the team.

Regarding the mufflers:
I suggest using the stock muffler because it was originally tuned to the motor headers/exhaustpipe. If engine hasnt undergone much change it makes alot of sense to use the stock chambered muffler.
But yes, you will usually have to modify your exhaust a bit to pass sound. Muffling can be simplified by the understanding that the more material there is to absorb the energy of the exhaust, the less energy it will have when it leaves the tailpipe; therefore, quieter exhaust readings. Use this to come up with a simple solution for your first year or even second year car. Bill, I completely agree with you as well, but I think there is an easier, quicker solution for teams that have different design priorities (i.e. getting a first running car by comp.)