Megan Header Dyno Results

[ChinoCharles]

Thank you largeorangefont, I'm looking forward to it.

[acrbill]

largeorangefont,
when I google the transmission ratios I get hit for 3.722:1 and 3.941:1.
Perhaps

[largeorangefont]

Originally Posted by acrbill

largeorangefont,
when I google the transmission ratios I get hit for 3.722:1 and 3.941:1.
Perhaps

If you have access to a tach, get a RPM reading at 80 mph in 5th and we can figure it out. My guess is 3.9.. but I could be wrong.

[Russelt3hPirate]

Originally Posted by largeorangefont

If you have access to a tach, get a RPM reading at 80 mph in 5th and we can figure it out. My guess is 3.9.. but I could be wrong.

I has access to a tach :)

Defi Concept HUD in my yaris FTW!

[largeorangefont]

Ok here is a quick and dirty version of how the dyno figures out horsepower. A dynojet is the simplest, because there is no load. The dyno takes the known weight of the roller(s) and derives hp based on how long it takes the car to get the roller up to speed. So if you have the car in 2nd for example, the roller is going to spin up faster, relative to a 4th gear pull. It is just like doing 30 on the street in 2nd gear vs 4th gear.

In real terms you *should* have the same horsepower either pull, but the curve will be very different looking. Think how the car pulls from 30 mph in 2nd vs. 4th gear, and how that will translate to a HP curve.

Some dynos will measure more horsepower just from switching a lower final drive and some don't. You arent gaing HP, but you are spinning up the roller(s) quicker. You can see how the dyno could then traslate that difference into more HP. I have personally seen this happen, and it is obviously incorrect. Alot of newer dynos are calibrated not to do this, but just be aware that is can happen.

The reason you want to use 3rd or 4th gear on a dyno pull is to put more of a load on the car. For tuning, you want to see what happens with the air fuel ratio and timing high in the load range. Tuning in 1st and 2nd does not give you an accurate picture of how the car will run in higher gears with more load.

Depending on the dyno operator and the car, sometimes shops do their tests in 3rd gear because speeds are too high in 4th on some cars. For seeing gains of a particular part, as long as you can eliminate every variable possible, you should get an accurate picture. Dynos, their calibrations, and HP numbers can vary greatly so it is not valid to compare numbers from dyno to dyno. Just think of the dyno as a tool to check gains. I would always try to go to the same dyno facility, and make sure that all calibrations are as close as possible each time you dyno for the best result.

Hope all this helps.

Ashley

[ChinoCharles]

Thank you Ashley, everything makes a bit more sense.

Mustang Dynos apply a small amount of resistance and use that load and not the mass of the roller to determine horsepower. Got it.

Russel, how do you like that HUD? It has to take some getting used to...

[largeorangefont]

Originally Posted by ChinoCharles

Thank you Ashley, everything makes a bit more sense.

Mustang Dynos apply a small amount of resistance and use that load and not the mass of the roller to determine horsepower. Got it.

Russel, how do you like that HUD? It has to take some getting used to...

You got it. A mustang dyno is much better for tuning because you can simulate driving conditions with more realistic loads on the car, and do steady state tuning, That is more effective and accurate than using a Dynojet and doing WOT tuning.

[Russelt3hPirate]

Originally Posted by ChinoCharles

Russel, how do you like that HUD? It has to take some getting used to...

I love it. it doesn't take anytime to get used to.

the shift light and audible beep is awesome :)

[Yaris TTE JWRC]

Originally Posted by ChinoCharles

WEEEEEEEEE

Attachment 2663

What a fun experience man... I got to shoot the shit with the guys from Twisted Innovations and talk about this car and other cars. I learned a lot.

As far as the results, their printer was down so they are e-mailing me the sheets tomorrow. The gain was 3 or so horsepower, but that doesn't tell the whole story of what the header does. There was also a steady 3 ft/lb gain in the torque curve that came on quick and stuck around for a few thousand RPM. There was no net torque gain though. We did both runs in third gear.

It was funny... we first ran the car in fourth gear and got a whopping 125 HP to the wheels! I was so confused! As the boys said, though, "the dyno doesn't lie." It was even calibrated a couple of weeks ago, so for a second we were stumped. Then one of the guys in the shop said that some of these fuel efficient pump gas cars have two overdrives to save some MPG's. Anyone know if that is the case with the Yaris?

The third gear runs had us in the 105 HP range. I'm sure if we had done the tests in first gear we would have been in that 70-80 WHP range that is documented. Either way, we got the gains.

The guys at TI seemed excited about the prospect of having the car in their shop, and hopefully I will be working with them to develop some more parts for the car. You'll see threads popping up in the appropriate forums meant to gague interest in certain parts. If you see something posted that you would like to be on the market, post in the thread, because they're watching.

I'll post the actual sheets tomorrow.

Where's the pic of your header that's installed on your car?? Can you take some pics of it installed on your car??? i really want to see it, cause im thinking to get a header too .

[Chris07LB]

Here's some for you... Search for my How_To if you need more info.

[Doc Zaius]

Alright... I started doing a bit of poking around and reading online as to the relationship between "backpressure" and torque, and why free-flowing headers and exhaust systems can decrease the amount of low/mid torque. People assume that since a more restrictive muffler/header/whatever has higher low-end torque, then it must be because of increased backpressure. Right? Wrong! Its b/c with a smaller diameter exhaust system, the exhaust gasses move faster. These faster moving gasses produce a slight vacuum behind them, which actually helps to pull the remaining exhaust out of the cylinder. This process is known as "scavenging". Otherwise, these gasses would be left in the cylinder, displacing new, fresh air/fuel, and thereby producing less power. As the engine speeds up (higher RPM), the scavenging effect is less pronounced, and the exhaust system's ability to flow gasses makes more of a difference, which is why the megan header works very well at very high rpm.

For some better information on this, please check out the following two very good quick-reads: Exhaust: The straight scoop on backpressure and Exhaust system backpressure.

Any thoughts/comments?

[Moose]

Originally Posted by Doc Zaius

Alright... I started doing a bit of poking around and reading online as to the relationship between "backpressure" and torque, and why free-flowing headers and exhaust systems can decrease the amount of low/mid torque. People assume that since a more restrictive muffler/header/whatever has higher low-end torque, then it must be because of increased backpressure. Right? Wrong! Its b/c with a smaller diameter exhaust system, the exhaust gasses move faster. These faster moving gasses produce a slight vacuum behind them, which actually helps to pull the remaining exhaust out of the cylinder. This process is known as "scavenging". Otherwise, these gasses would be left in the cylinder, displacing new, fresh air/fuel, and thereby producing less power. As the engine speeds up (higher RPM), the scavenging effect is less pronounced, and the exhaust system's ability to flow gasses makes more of a difference, which is why the megan header works very well at very high rpm.

For some better information on this, please check out the following two very good quick-reads: Exhaust: The straight scoop on backpressure and Exhaust system backpressure.

Any thoughts/comments?

You beat me to it.