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Discussion Starter #1
Has anyone collected dyno-backed HP/Torque information on the various exhausts? My understanding is that is basically impossible to improve power with an exhaust on the Elise. The same was true on the Boxster S; every aftermarket exhaust lost power compared to stock.

Are exhausts mainly for sound? Weight loss? Any power improvements?
 

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This seems to be a common problem with many cat-back exhaust systems: difficulty reproducing dyno data. Maybe some statisticians out there could tell us how many dyno runs are needed to acheive statistically significant data, ie, "n" for p<.05.
My guess is that if you are looking for a difference of less than
5% in rwhp (plausable) that "n" would have to be very high in
order to exclude the effect of random variability. In other words,
buy your exhaust system for the SOUND!
 

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I'm fine with break-even on power, but 10 lbs lighter and the beautiful sound! :D
 

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I tend to be more comfortable with calling a gain or loss when you do some thing more than simple A/B testing. Something like A/B/A/B for example. If B is the mod and each time you put it back on the output changes the same amount and in the same way then this can be considered more credible than if you just do a before / after. As you dyno a car with no other changes you will find some variations. The idea is not to call the normal variations the change. It can get considerably more complicated than this, especially with adaptive ECUs such as OBD2 styles.

I did an A / B / A on the Elise with an airfilter swap with A being K&N and B being stock. But this was over time! FWIW the K&N gained a small amount of HP, about 1-2 HP. You can't feel this.

Sometimes you can call a "winner" in other ways even if output is not measured. For example you may find that a car with a mass air sensor can have the sensor outout logged (stand alone or via OBD2 logger) and if more air goes into a motor after you make a mod then that part might be considered better, even if the output was not measured or the setup tuned. Sometimes when you do this you can be misled. Or you find yourself wanting to do some more testing...

Stan
 

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I posted the other QS dyno comparison. Just because the "peak" HP was a little less on the QS doesn't mean it lost power. I think across the toque range there was just a marginal gain, but the variation in each dyno run is greater than the differential of the QS and Stock.
Although I didn't do it for the sound, I really like the QS now, very much deeper.
 

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I've been under the impression (possibly misguided) that altering
the stock exhaust manifold is more important than altering the exhaust can for most modern cars in terms of horsepower gain.
Is the Elise's exhaust manifold different than the Celica's? Has anyone fabricated headers or cat bypass pipes for the Elise?
 

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Discussion Starter #10 (Edited)
JimK said:
I've been under the impression (possibly misguided) that altering
the stock exhaust manifold is more important than altering the exhaust can for most modern cars in terms of horsepower gain.
This my understanding also. Exhausts are mainly for sound and reducing weight. So, I just want to see dynos that show the exhaust does not lose power that counters the loss of weight.

The Arqray system can be purchased with a bypass pipe.
 

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>>>I've been under the impression (possibly misguided) that altering the stock exhaust manifold is more important than altering the exhaust can for most modern cars in terms of horsepower gain. Is the Elise's exhaust manifold different than the Celica's? Has anyone fabricated headers or cat bypass pipes for the Elise?<<<

Our cars use stock Toyota headers which have a cast flange with welded on tubes. Various aftermarket headers for the Celica can be used on our cars. One costs only $250 and apparently gives decent gains. Some folks apparently port the stock headers to get comparable to aftermarket header gains. The cast/fabricated/welded joint portion obstructs flow a bit and can be die ground to clean things up. Our catalytic converter setup is different from the Toyotas but someone could make a bypass and find a way to deal with the CELs. The stock header used a bifurcating insert to help with converter warm up issues. Toyota admits that this is not the ideal exhaust approach for output. A more conventional header set up would tend to help the car but would need all of the follow on elements to be designed for it.
 

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sleepless said:
This my understanding also. Exhausts are mainly for sound and reducing weight. So, I just want to see dynos that show the exhaust does not lose power that counters the loss of weight.

The Arqray system can be purchased with a bypass pipe.
The Arqray system can also be bought with SS headers.

Shinoo, any info on the headers?
 
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