Megan Header Dyno Results

[Fastnx]

Right, but it is important to know what final drive is and how a transmission works.

According to chinocharles, the engine's power goes through 4th gear, the speed is multiplied by 0.9xx and that's it. This is not correct.

The power goes through the clutch to the input shaft, then through a gearset to the output shaft. This gearset is different for every gear. The output shaft then travels through the differential, which reduces the engine's speed once again. Most final drives are in the 4:1 range.

So if your first gear ratio is 3:1 and the final drive ratio is 4:1, the wheels are actually travelling 1/12 the speed of the engine.

If your fourth gear is 0.9:1 and the final drive is 4:1, the engine is still travelling 3.6 times faster than the wheels.

The assumption that you have to dyno in the gear closest to 1:1 is false, since the power is going through a final drive, the wheel speed will never be close to the engine speed. If your dyno guy is telling you this, he is wrong. Just because you own and operate a dyno does not mean you know the science behind how a dyno works.

At a dyno I went to, the operator did not even know the fundamental relationship between horsepower, torque and RPM which is HP=(Tq*RPM)/5252.

[ChinoCharles]

I will definitely be going back to the dyno to retest the header. Right now my car is stock, as I have the header off to save me some work when I do go back. If the pulley is delivered before the dyno is fixed, I will be testing that too.

Since the dyno was just reading heavy, I am looking at the graphs now and thinking that if you reduce the numbers by about 25% it should be somewhat accurate. Knowing that, the header does so little on its own that I don't see much of a point in testing the car with the stock header and pulley. Whatever the pulley does with the Megan header on is going to be on par with what it does with the stock header, and that saves me having to put the car on the lift twice.

[Fastnx]

In 8 posts on these forums, you haven't posted one bit of usable information, so you have no room to talk about facts

So the only thing i know about cars is from the time I have spent at yarisworld?

I am not the typical Yaris owner. I have been involved with cars for more than two decades. I race Nissan NX2000s, I build our motors which make 270hp from 2160cc. Before that I was a race mechanic on a Formula BMW that my brother raced.

I just happen to be an environmentally responsible consumer, and consequently have an interest in Yarii. I'm on this site to find out about what is available for this car and what others have done.

Heres a pic of my racecar

[Russelt3hPirate]

Originally Posted by ChinoCharles

Whatever the pulley does with the Megan header on is going to be on par with what it does with the stock header, and that saves me having to put the car on the lift twice.

so, you really think that pulley is going to make power to help negate the loss else where in the power band from the improperly design'd header?

wouldn't it make more sense to just buy a header that makes real power instead of trying to cover an open wound with a bandaid?

you're claiming 10hp from a pulley right?

[acrbill]

A quick google search.

http://www.awe-tuning.com/pages/faq/...ain.cfm?FAQ=22

Gearing: a chassis dyno is susceptible to gearing bias. Recorded power can be affected on a dyno graph by simply running the test car in too low or too high a gear. Dyno operators should pick the trans gear that is closest to a 1:1 ratio to avoid gearing bias. This ratio is 4th gear in most cars. In a 1:1 ratio, the two gears that make up a gear set are the same size. When one is larger than the other, either in a lower gear than 1:1 or a higher gear than 1:1, there are frictional losses that translates to less power put to the wheels. Also, too high of a gear that causes the test car to go to a top speed far greater than the available fan cooling capacity will produce invalid results.

http://www.bristoldyno.com/info/procedure.htm

Many dynamometer operators go right for the gear that is the closest to a 1:1 ratio as it has the lowest drag in the gearbox and therefore the highest horsepower reading (usually) on a vehicle that is properly sized to be tested on this dyno.

There is dozens more hits that back up that being close to 1:1 is important.

[ChinoCharles]

Originally Posted by Fastnx

According to chinocharles, the engine's power goes through 4th gear, the speed is multiplied by 0.9xx and that's it. This is not correct.

DEE DEE DEE!

When did I say that? Let me make the font bigger so you can read it.

My dyno tech told me that we need to test the car in a gear with a ratio as close to 1:1 as possible.

I don't even know enough about engines to say what you quoted me as saying, so please, don't put words in my mouth.

I edited the rest out because acrbill was nice enough to quote those pages for me. I knew I had read articles online backing up my tech's statements, but I couldn't find them again, so thank you Bill.

[acrbill]

Originally Posted by Fastnx

So the only thing i know about cars is from the time I have spent at yarisworld?

I am not the typical Yaris owner. I have been involved with cars for more than two decades. I race Nissan NX2000s, I build our motors which make 270hp from 2160cc. Before that I was a race mechanic on a Formula BMW that my brother raced.

I just happen to be an environmentally responsible consumer, and consequently have an interest in Yarii. I'm on this site to find out about what is available for this car and what others have done.

Heres a pic of my racecar

Oh man! If you would have mentioned this earlier it would have saved some misunderstanding. Instead of thinking you where a moron we would have had proof of it.

Your obviously full of shit, and you thought you could come onto a site and pull the wool over our eyes with your supreme knowledge of all things automotive.
What you failed to realize is that we are not little kids enamored with pictures of "race cars".

Do everyone a favor and buy a Honda Fit.

[Fastnx]

A quick google search.

http://www.awe-tuning.com/pages/faq/...ain.cfm?FAQ=22

Quote:
Gearing: a chassis dyno is susceptible to gearing bias. Recorded power can be affected on a dyno graph by simply running the test car in too low or too high a gear. Dyno operators should pick the trans gear that is closest to a 1:1 ratio to avoid gearing bias. This ratio is 4th gear in most cars. In a 1:1 ratio, the two gears that make up a gear set are the same size. When one is larger than the other, either in a lower gear than 1:1 or a higher gear than 1:1, there are frictional losses that translates to less power put to the wheels. Also, too high of a gear that causes the test car to go to a top speed far greater than the available fan cooling capacity will produce invalid results.

http://www.bristoldyno.com/info/procedure.htm

Quote:
Many dynamometer operators go right for the gear that is the closest to a 1:1 ratio as it has the lowest drag in the gearbox and therefore the highest horsepower reading (usually) on a vehicle that is properly sized to be tested on this dyno.


There is dozens more hits that back up that being close to 1:1 is important

Hey, anyone can post anything on the internet, that doesnt mean it is correct.

Here, check out the flat earth society's webpage:

http://www.alaska.net/~clund/e_djubl...rthsociety.htm

[Fastnx]

Oh man! If you would have mentioned this earlier it would have saved some misunderstanding. Instead of thinking you where a moron we would have had proof of it.

Your obviously full of shit, and you thought you could come onto a site and pull the wool over our eyes with your supreme knowledge of all things automotive.
What you failed to realize is that we are not little kids enamored with pictures of "race cars".

Do everyone a favor and buy a Honda Fit

What, are you calling me a liar?

[largeorangefont]

Originally Posted by Fastnx

What, are you calling me a liar?

Hes calling you dumb. So am I.

[ChinoCharles]

Originally Posted by Russelt3hPirate

so, you really think that pulley is going to make power to help negate the loss else where in the power band from the improperly design'd header?

wouldn't it make more sense to just buy a header that makes real power instead of trying to cover an open wound with a bandaid?

you're claiming 10hp from a pulley right?

With numbers that were inflated about 25%, the graphs only showed 2 HP and 3 ft/lb losses. Assuming peak HP numbers will drop from 105 HP to around 80 HP after the dyno is fixed, the losses will be minimal... a little more than 1 HP and about 2 ft/lbs.

I don't see that as a huge tradeoff considering...

1) This is still an N/A car, and the 2.5" diameter piping on the Megan header will probably do more for the car with forced induction.
3) After 5600 RPM I'm gaining more than what I'm losing in the rest of the powerband.

Sure, my lofty hopes got shot down a tad. Lesson learned... when dealing with low displacement econoengines, don't expect much from simple bolt-ons.

10 HP from the pulley... I'm not that dumb, haha. Judging from what I've seen from the dyno results from other cars, I think 2-3 HP is a good estimate. Considering the piece is a tad over a hundred bucks and you see that 2-3 HP from 0 to 6500 RPM, I'm happy NST decided to make it.

[ChinoCharles]

+8 to the first person that finds out the final drive ratio for the NCP91.

[largeorangefont]

Here are the transmission ratios for the 5MT

Manual five-speed transmission with shift lever on floor,
3.545:1 first gear ratio,
1.904:1 second gear ratio,
1.31:1 third gear ratio,
0.969:1 fourth gear ratio,
0.815:1 fifth gear ratio
3.25:1 reverse gear ratio manual

Final drive ratio, 3.941:1

[acrbill]

tree'd

1st-3.545:1
2nd-1.904:1
3rd-1.31:1
4th-0.969:1
5th-0.815:1
final drive-3.722:1
reverse-3.25:1

[largeorangefont]

Originally Posted by ChinoCharles

With numbers that were inflated about 25%, the graphs only showed 2 HP and 3 ft/lb losses. Assuming peak HP numbers will drop from 105 HP to around 80 HP after the dyno is fixed, the losses will be minimal... a little more than 1 HP and about 2 ft/lbs.

I don't see that as a huge tradeoff considering...

1) This is still an N/A car, and the 2.5" diameter piping on the Megan header will probably do more for the car with forced induction.
3) After 5600 RPM I'm gaining more than what I'm losing in the rest of the powerband.

Sure, my lofty hopes got shot down a tad. Lesson learned... when dealing with low displacement econoengines, don't expect much from simple bolt-ons.

10 HP from the pulley... I'm not that dumb, haha. Judging from what I've seen from the dyno results from other cars, I think 2-3 HP is a good estimate. Considering the piece is a tad over a hundred bucks and you see that 2-3 HP from 0 to 6500 RPM, I'm happy NST decided to make it.

2.25 piping is going to be the best for this car unless you are going for all out HP or forced induction.

[largeorangefont]

Originally Posted by acrbill

tree'd
final drive-3.722:1

Not saying you are wrong, but we found different final drive #s. I got mine off some canadian site. Where did you get yours? Just want to clear it up so we aren't posting misinformation.

We could figure it out mathamatically I guess but I'm too lazy, and don't have a car to veryify it yet :)

[ChinoCharles]

largeorangefont, +8. I don't know what the points means either... you'll have to ask Bigsky2. I got it from him.

To get an idea of how widely these ratios vary, a Cadillac STS-V's final drive ratio is 2.56:1. I wanted to assume most cars had a final drive ratio near 4, but that would obviously be wrong.

Now that we know this, fastnx... what the hell was your original arguement? It seemed like you were trying to say that the idea behind a dyno is to get the engine speed to match wheel speed, but there is no gear on a Yaris that comes even close to this. The closest you will come is in fifth when your ratio is 3.212:1. I'm trying to understand where you were coming from.

[largeorangefont]

Originally Posted by ChinoCharles

largeorangefont, +8. I don't know what the points means either... you'll have to ask Bigsky2. I got it from him.

To get an idea of how widely these ratios vary, a Cadillac STS-V's final drive ratio is 2.56:1. I wanted to assume most cars had a final drive ratio near 4, but that would obviously be wrong.

Now that we know this, fastnx... what the hell was your original arguement? It seemed like you were trying to say that the idea behind a dyno is to get the engine speed to match wheel speed, but there is no gear on a Yaris that comes even close to this. The closest you will come is in fifth when your ratio is 3.212:1. I'm trying to understand where you were coming from.

It depends on the torque of the engine. Smaller displacement cars have gear ratios near 4:1 to get them up to speed better. Consequently, they run at a higher RPM on the highway.

My mustang has a 3.55 final drive, and a 6 speed transmission and at 80 MPH it is doing 2200 RPM. A Xa I test drove was doing well over 3000 RPM approaching 80 MPH.

I will explain more about how a dyno works and how gearing can affect the results after I get some lunch.