Chief_Yota

good point there buddy,but first i dont have no cat cause i want more power,haha,its cause i dont have 150 bux to spend on it.now I FOUND THE PROBLEM LADIES!! it was the tps i adjust it carefully this morning and rechecked my timming wit a timming light gun,10 btdc advance,cause i run high octane gas,and voila! it takes me almost half of what it took me before to get from one point to the other. and im thinking to replace that O2 sensor soon too and see if its even better.

Jay351

.....

Plus currency conversion
Plus shipping (minimal)
Plus border fee's

Its just cheaper overall if you buy one in canada if you live in canada.

Bumpin' Yota

That is the stock set timing and is suitable for 85 octane. Only get enough octane to prevent pinging, and use only Teir 1 gas.

I run 17*btdc and run 93 octane.

Jay351

I use nothing but 87 octane!! Never had any pinging

elripster

You can check the O2 sensor with a meter. When O2 sensors stop sending a signal, the ECU interprets that as a lean condition and enriches the mixture accordingly.

Back pressure affects the frequency of an exhaust system's scavenging and very much affects the performance of a 4 stroke engine. Unless the engine is built to rev extremely high, back pressure is necessary to scavenge within the engines mechanical operating limits.

More pressure will lower the frequency and you will experience low RPM scavenging and corresponding torque. Pressure will build quickly and typically sap higher RPM torque and thus power. (power = torque * RPM)

Less back pressure conversely increases the frequency thus scavenging at higher RPM's. As you have guessed this means more power.

All things equal, pumping and friction losses are higher at higher RPM's so producing power at a lower RPM is better for fuel economy because those losses make up a smaller fraction of the total engine power at the point. This will make your truck slower.

All that said, it is highly unlikely your Y pipe mod and lack of catalytic converter have reduced back pressure to a point the engine is scavenging at an RPM it cannot reach.

When my cat was stolen, I was very curious to see the effect on engine performance. The effect was pronounced, the engine had very little torque; acceleration was terrible. This lack of torque was evident throughout the RPM range. Not only is scavenging affected but EGR is as well increasing the likelihood of knocking and resulting retarding of the timing. The addition of the high flow cat and more free flowing cat-back exhaust increased engine performance over stock and yielded a 1.5MPG increase in economy.

Frank

Stomis

I never said the engine needed backpressure. A properly setup system with the correct backpressure will allow for a better low end torque range. A fully free flowing exhaust will knock that low end torque down and up high end horse power. I know that for a fact cause I did it to my camaro when I put headers and 3" tubing all the way back on my 305. It had an exhaust to handle 500hp on a 250hp car.