Interesting Result Losing Muffler

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Mako Koiwai
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Interesting Result Losing Muffler

Post by Mako Koiwai »

This weekend at Buttonwillow was my first chance to drive the ex-Philip Royle SCCA ITA prepped '96 Miata. I was running on new 205/50/15 Goodyear RS DOT R-Tires, but the harder RC compound, on 7" wheels.

Philip had been running a RacingBeat muffler, in deference to his neighbors when he was garaging the car. I wanted to see if it made any difference power wise running without the muffler. Being in the ITA class, the car has a straight though header/exhaust, no CAT. Car has a MegaSquirt ECU/Tune, and runs on 100 octane.

On Sunday we ran track configuration 1, clockwise, 3.1 miles in length; the longest configuration.

I pretty much went faster on each lap, starting at 2:34 and ending up at 2:27:031 by the end of the 2nd Practice. For the 2nd Practice I removed the muffler. It probably weighs around 20 lbs. (btw. that 2:27 time would have qualified me in 18th out of 22 car in the IT/SSC/SSB Touring Car race. I was only doing the Time Trial Practice; no races for me. The fastest Spec Miata in the field was 11 seconds faster then me! But he was 3 seconds faster then the next Miata.)

For the third and last Practice I put the muffler back on. By now I was definitely feeling more comfortable with the car, keeping my foot down in more places, getting into the next gear sooner and getting into 5th gear in a couple of places (4.77 rear end). At 4PM it was pretty much the warmest it had been all day, but not hot. I figured I had probably dropped my time another 2 seconds.

So I was very surprised when I got my times. I was about 2.5 seconds SLOWER each lap for my string of four hot laps and my fastest last lap was still a good 2 seconds slower then my fast lap without the muffler. Losing the muffler definitely seemed faster.

But, I didn't have a turn down and melted the rear bumper. That fellow that was in the fastest Miata had the tiniest bit of a turn-down at the end of his exhaust, ending just past the rear A arm, and he wasn't suffering from any heat damage.

I HAD a turn-down made for Karen's Miata, but it got cannibalized to attach her Supertrapp muffler to her car.

So now I'm looking for a replacement RED rear NA bumper! :(

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Mako Koiwai
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Re: Interesting Result Losing Muffler

Post by Mako Koiwai »

Melted bumper or not ... the car still puts a big smile on ones face!

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Oli Thordarson
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Re: Interesting Result Losing Muffler

Post by Oli Thordarson »

I can only speculate on what HP and torque variances there are for your car with and without the muffler so I won't comment on that. It is not unocommon though as the day warms up to lose 1 to 1.5 seconds from a 10 am-ish qualifying time to a 3 pm race. Of course the race is always a bit different. It is not run for the absolute fastest lap time, but to make the car and tires last for the fastest overall race time... often Lille with defensive lines, etc.

Your tires, the ambient air temp, the track temp and the track (oil residues, et-al) all could have conspired to slow you down a couple of seconds. Were you tiring out? Or maybe losing the back pressure hurt your torque pull out of the corners?

I think it is tires and air temp mostly and track temp second if it got warm at all.

But what do I know. I am just a dumb Corvette driver. Now where did I leave my gold chains and chest wig...?


Oli
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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

I would agree with Oli. I doubt you could make 10hp more on Philips
car no matter what you did to the exhaust, and 10hp would not make
a 2sec difference. There is much more at work there, weather and track conditions are going to make more of a difference. With so many
newbies in the dirt that track was a mess.

You want to know if there is power left in the exhaust? Dyno the car. No doubt that is a conservative exhaust, but you won't find any big numbers left in that car.
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Re: Interesting Result Losing Muffler

Post by Mako Koiwai »

I would also find it hard to believe that losing the muffler would make that much of a difference, but the fact is that at this early stage of the game with me getting use to the car, there is no doubt I was steadily and consistently improving on my times. That's in Black and White. It's cool driving on a road course and measuring one's progress by how much sooner one shifts up as one gets out of the corners faster. I thought that with the warmer weather I was finally getting some decent heat into the tires, and remember, these are the harder compounds. Like running R6's instead of A6's.

By the time we ran our third practice, dirt really wasn't an issue. I was pulling more rev's through Riverside then during any other time of the day. I was finally keeping my foot in it going around the Kink before Phil Hill. I was progressively and consistently feeding in the power through the Esses. I was taking Sunrise, Sunset and Bus Stop faster but perhaps the new tires had lost their "magic" after 25 laps?

I'm just going to have to decide on having another turn-down made and taking the RB muffler on and off, or do we add a SuperTrapp muffler, that's straight through with a surrounding of baffling and then have an easier/faster time of just taking off the end plates when at an event. I too have neighbors to consider.

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Re: Interesting Result Losing Muffler

Post by Mako Koiwai »

With the cool down lap at the end of Practice, how should one measure tyre temps? Should one "sacrifice" a practice lap and come in during the middle of practice to take measurements?

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Re: Interesting Result Losing Muffler

Post by Mako Koiwai »

Another nice image from http://vanhap.com/" onclick="window.open(this.href);return false;

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Re: Interesting Result Losing Muffler

Post by Mako Koiwai »

A newbie funny ...

I had a flat battery earlier on Saturday, so when my car wouldn't start while in Grid, I yelled out to Renee that I needed a push start. Renee didn't hesitate to push, and a few fellows jumped in to help. After a couple of failed attempts, I realized I had forgotten to turn on the Kill Switch! I should have waited to start the car while they were pushing. Instead I started it as they pushed me back and I had come to a stop. :oops: :lol:
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Re: Interesting Result Losing Muffler

Post by KJ Christopher »

Mako to wrote:I would also find it hard to believe that losing the muffler would make that much of a difference, but the fact is that at this early stage of the game with me getting use to the car, there is no doubt I was steadily and consistently improving on my times. That's in Black and White.
30 minutes on a dyno will give you a definite answer. I agree with the others, no way losing the muffler was worth 2.5 seconds. Even if it felt faster or if you were pulling more revs in certain sections. Best bet is to take it to a dyno and get real data so you don't go chasing rabbits!
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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

The car has data in it, what does it show?
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Re: Interesting Result Losing Muffler

Post by Oli Thordarson »

I hate the Hoosier R6. If the Goodyears are anything like the R6 there first session is OK and it is all downhill from there. By the third session they are dead in my opinion. You can easily lose 1.5 seconds from the first morning session to the third or fourth afternoon session just in the R6 let alone the other possible factors.
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Re: Interesting Result Losing Muffler

Post by Oli Thordarson »

PS. Get A6s and burn them down to cord and they are still faster than R6s. Did I mention I hate R6s?
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Re: Interesting Result Losing Muffler

Post by Oli Thordarson »

PSS. Did you know that their are new Hoosier A7s and R7s due later this year. All new compounds that are much more resilient like the compounds on slicks. Better heat cycling and better wear. New lighter tire construction, too, I am told. The tread wear rating, i.e. Tread wear rating 40 is going to change to a different numbering system that won't match what you are used to now. The net result is a tire about a second faster on a 1:30 track with better lasting performance.

...so that is what a little birdie told me.
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Re: Interesting Result Losing Muffler

Post by Steve Collins »

I think what we've learned is that the louder the car is, the faster Mako drives. We need to get him one of those vroom vroom things that plugs into the cigarette lighter.

sc

And some headphones.
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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

Mako to wrote:I would also find it hard to believe that losing the muffler would make that much of a difference, but the fact is that at this early stage of the game with me getting use to the car, there is no doubt I was steadily and consistently improving on my times. That's in Black and White. It's cool driving on a road course and measuring one's progress by how much sooner one shifts up as one gets out of the corners faster. I thought that with the warmer weather I was finally getting some decent heat into the tires, and remember, these are the harder compounds. Like running R6's instead of A6's.

By the time we ran our third practice, dirt really wasn't an issue. I was pulling more rev's through Riverside then during any other time of the day. I was finally keeping my foot in it going around the Kink before Phil Hill. I was progressively and consistently feeding in the power through the Esses. I was taking Sunrise, Sunset and Bus Stop faster but perhaps the new tires had lost their "magic" after 25 laps?

I'm just going to have to decide on having another turn-down made and taking the RB muffler on and off, or do we add a SuperTrapp muffler, that's straight through with a surrounding of baffling and then have an easier/faster time of just taking off the end plates when at an event. I too have neighbors to consider.
First, don't let the fact that Goodyear is releasing an "autox" tire fool you into thinking the RC is like an R6. We have done back to back testing with a number of brands and I can tell you on the road course that is not the case at all. The tire is fast and consistent to the end. That car on four race old RC's will beat that ITA Honda (the one that dogging the T1 newbies) and even the quickest SM in the area. With the amount of time you were dropping per session it is clear you did not have the track down - and being your first time in the car I doubt you were running it within 100% of its limit.

Rather than using your butt dyno for the exhaust comparison, and speculating at the tires falling off in a short 20 min session (when these same tires have been used in 40min natl races without a problem) pull your data. Lay up your fastest lap from each session and we will definitively see where the time was lost.

You may have improved sections only to toss it all away in others, the data will show you. I am at a loss as to why you would be putting a wrench on that car, when it is a proven winner that has beaten every car you saw in that run group. :?:
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Re: Interesting Result Losing Muffler

Post by Bill Martin »

Would your in-car data show max speed achieved at the end of the longest straight? I would think that would be a better measure of power than your lap times. Fewer variables. Wouldn't address mid-range benefits for exiting corners though.
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Re: Interesting Result Losing Muffler

Post by Don Salyers »

I really think that if Mako was given a Brand New Formula 1 car, fully prepared, he would still take out his tools to improve it... }:) }:) :D

Don
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Re: Interesting Result Losing Muffler

Post by Will Kalman »

Mako, if the car has data acquisition equipment, take a series of first-gear rolling starts and graph the acceleration (or derive it from speed). Given that aero drag at the maximum speed of first gear will not be significant and a Miata isn't going to have wheelspin, you'll essentially have a dyno chart covering your full RPM range. Use the same pavement and in the same direction for each run, ensuring that conditions are the same (wind, ambient temp, engine temp, etc).
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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

Here is another thought.. Have Philip do a session in the car next time.
You can compare the data from him and you.
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Re: Interesting Result Losing Muffler

Post by Jayson Woodruff »

Regardless of the back pressure. 20lbs is nothing to brush off. I think Mako's got the right idea with a light weight supertrapp.

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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

Jayson Woodruff wrote:Regardless of the back pressure. 20lbs is nothing to brush off. I think Mako's got the right idea with a light weight supertrapp.

Jay W
Keep in mind when this car ran a race in ITA trim (just a month ago) it had 100lbs of ballast, a cool shirt system, a full tank (at the start) and the muffler to make minimum weight. It ran on four race old tires and beat all of the cars that were well ahead of it this past weekend. Is weight and a few HP the issue here, or is it familiarity with the car and the track? Learn both before chaining either.

I am not trying to beat up in you Mako, it is just a fact that you are not going to hit the same level as Philip you first time in that car on that track. Our Yaris was about 6secs off of its normal pace this past weekend, the only thing I am changing before the next race is the nut behind the wheel.
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Re: Interesting Result Losing Muffler

Post by KJ Christopher »

Don Salyers wrote:I really think that if Mako was given a Brand New Formula 1 car, fully prepared, he would still take out his tools to improve it... }:) }:) :D

Don
:lol:
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Re: Interesting Result Losing Muffler

Post by Jason Isley BS RX8 »

Oli Thordarson wrote:
I am just a dumb Corvette driver. Now where did I leave my gold chains and chest wig...?


Oli
They were being shared by the T1 guys that thought a NASCAR side by side restart was in order after the caution. :lol:
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Re: Interesting Result Losing Muffler

Post by Philip Royle »

I don’t think the tires are the reason for the 2 second drop in time. At the Willow Springs Double National last month in that Miata I ran the same set of Goodyears all weekend -- they had 3 races (meaning 3 sets of practice, qualifying, and races -- on them going into the weekend. Saturday qualifying I ran a 1:39.950, and during the Sunday race (one 40 minute race and a qualifying session later), with unknown changes in ambient and track temperatures, I ran 1:40.419. With all those laps and all those changes in conditions, I was within half a second of myself during the course of the entire weekend.

Now consider that Todd Launchbaugh, who was driving the #13 Miata that was on the ITA pole this past Sunday at Buttonwillow, also ran at the Willow Springs race. He ran a 1:40.337 in Saturday’s qualifying at Willow Springs and a 1:40.956 in Sunday’s race. Our drop off over the course of the entire Willow Springs weekend was about the same -- in fact, mine was 0.15 seconds less.

It could be all of our tires were fading and that’s why we all went slower, but they were all doing it at the same rate, and they certainly weren’t doing it by 2 seconds over the course of one session.

I also doubt the 2 seconds was from pulling the muffler. If I thought there was 2 seconds in changing the muffler, I would have done that 5 years ago.

Pull the card on the data system and email me the files from this past weekend and I’ll tell you where the 2 seconds went.

Philip
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Re: Interesting Result Losing Muffler

Post by Steve Ekstrand »

Mako-

I know you like to tinker.

My suggestion. Test at the dyno. Change there, change back. Keep a detailed notebook. Be able to return to baseline always.

And for tinkering.... Work on the trailer. No, seriously. Get that trailer in shape. Get that tow vehicle in shape.

For the race car? Maybe work on the GoPro camera mounts???
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