Another S/C'd member worried about his AFR

[HTM Yaris]

I think you peeps are looking in the wrong place . I bet if you put your stock exhaust back on you will find your HP and torque . Remember that thing called "back pressure" . You peeps have opened your exhaust too much , IMO .
Opening an exhaust too much will result in a loss of HP and torque . Either you need more airflow to fit your exhaust or you need to downsize your exhaust to create the proper back pressure .

Want proof ? Just check out Noogie vs Poop setup . Poop has the larger exhaust and lower numbers .......

[LtNoogie]

Originally Posted by HTM Yaris

Want proof ? Just check out Noogie vs Poop setup . Poop has the larger exhaust and lower numbers .......

Ooo... don't remind him of that more that three more times!

[PETERPOOP]

Originally Posted by HTM Yaris

I think you peeps are looking in the wrong place . I bet if you put your stock exhaust back on you will find your HP and torque . Remember that thing called "back pressure" . You peeps have opened your exhaust too much , IMO .
Opening an exhaust too much will result in a loss of HP and torque . Either you need more airflow to fit your exhaust or you need to downsize your exhaust to create the proper back pressure .

Want proof ? Just check out Noogie vs Poop setup . Poop has the larger exhaust and lower numbers .......

I think you are wrong. You also forgot that my dyno run didn't go to 6500 RPMs like noogie's. You can see in my chart that the HP was still rising at a strong rate. It stopped at 6200 RPMs. Also, I was on a dynapack, not dynojet. Dynos are different.

I am going to dyno on a dynojet soon, run it to 6500rpms, and I can guarantee you it will be higher than 117hp on the dynojet.

I do agree that my larger exhaust lost torque, but HP, especially in the higher RPMs, naw.

But I am going to be running a 2" 24" resonator and a hi flow cat soon, so that will probably bring me some back pressure/torque back.

[dallas]

I agree that a smaller pipe diameter may help, like 2 inches, but your terminology is wrong. Backpressure is never a good thing, you do not want back pressure for ultimate horspower. What you want is no back pressure but fast exhaust gas velocity, if you go too big on the pipe diameter you loose the exhast gas velocity and the coresponding hp and torque.

Originally Posted by HTM Yaris

I think you peeps are looking in the wrong place . I bet if you put your stock exhaust back on you will find your HP and torque . Remember that thing called "back pressure" . You peeps have opened your exhaust too much , IMO .
Opening an exhaust too much will result in a loss of HP and torque . Either you need more airflow to fit your exhaust or you need to downsize your exhaust to create the proper back pressure .

Want proof ? Just check out Noogie vs Poop setup . Poop has the larger exhaust and lower numbers .......

[HTM Yaris]

Back pressure is a good thing . Some not alot . Without Backpressure(BP) there isn't any exhaust gas velocity . If no BP was a good thing all the real race cars would have exhaust gas being released straight from the exhaust port . ( Yes I realize that exhaust pipes also evacuate heat )


Try this , go turn on your garden hose . See how it flows ? To increase the velocity of the flow you can do 2 things 1. increase the volume of water or 2. partially cover the end of the hose with your thumb (creating BP) .

[dallas]

Backpressure does not create exhaust gas velocity, if the pipe diameter is too big the air moving down the pipe slows down and cools down which in turn makes the air molecules less active slowing down the flow. The reason race cars don't release at the exhaust port is because exhaust velocity actualy help draw air out of the cylinder head, but to get that you need the right diameter and length of pipe to create the exhaust velocity, what you don't want is any back pressure to slow down the flow, You have the right idea just not the right terminology, there are some really good papers on exhaust design and performance done by ASTM I belive, that tell you exactly that.

Originally Posted by HTM Yaris

Back pressure is a good thing . Some not alot . Without Backpressure(BP) there isn't any exhaust gas velocity . If no BP was a good thing all the real race cars would have exhaust gas being released straight from the exhaust port . ( Yes I realize that exhaust pipes also evacuate heat )


Try this , go turn on your garden hose . See how it flows ? To increase the velocity of the flow you can do 2 things 1. increase the volume of water or 2. partially cover the end of the hose with your thumb (creating BP) .

[largeorangefont]

I didnt read the entire thread but think I have a decent idea of what is going on.

Here is the first thing I will say here:

Comparing results from DIFFERENT DYNOS is not accurate and a waste of time.

Different dyno manufacturers read differently, and ambient conditions change from day to day. If you have dyno results before and after a mod on the SAME dyno, generally the gain (or loss) you see is close to accurate.

At this point, it looks like that if you want to fully realize the gains from a blitz SC, you will need addtional tuning.

A fuel controller may work, but if timing is still retarded, you are only going to LOSE more power. We need to find out what that box does. Lets say all it does is retard ignition timing. Then I would say remove the bot, get a fuel controller and adjust the fueling curve, run cooler spark plugs and always run premium fuel.

Adding a rising rate FP regulator is NOT a solution for a returnless car. There is really no mechanical fix to solve this particular problem. You are going to want a piggyback ECU or a reflash.

You guys are not going to fix this with fuel system mods. I assure you, you are not running out of fuel with a ~30 HP gain.

Peterpoop,

Your exhaust is fine, I would not worry about it. If you can get something to view your ignition advance in the meantime, do so.