hey guys the shop finally got the headers, 3inch y-pipe and cat on my car and thats all i'm running right now till I get the new muffler and rest of the pipes made for it tommarrow. But I was driving it back form the one shop and its really really loud as I anticipated it would be but not really as bad as I thought it would be. But the car feels like it has lost alot of hp, I figured I would loose some to not having any back pressure but not this much. Is this real normal, I'm just getting paranoid cause i spent all this money and I hope I'm in good hands. But anyways, I have a 40 series muffler 3" in and dual 2.5 outlets, I plan on running it directly straight out the back, I know it will be kinda low, but the 3" y-pipe and 3" cat are sitting low as is.

Or alternative 1: I go and try to trade out for a 3" in and dual 2.5 inch outlets 80 series muffler.

Or alternative 2: I go and just have him run a 3" pipe with no muffler and split it in dual 2.5's and run it out the back stock style, so the cops wont notice as much when I drive. But it will be still loud.
Your input is much appreciated

 

Since when is back pressure a desirable thing to have?

 

Well dont i need some back pressure? Why is it running so slow not than after jus the headers are installed with the y pipe and catco convertor?

 

Plus I forgot to mention, the 02 sensor I believe thats on the cat is not installed cause the shop could not give a lip to it since they had no way of heating it.

 

When I was running 2055's with an open y pipe, the car felt like it had lost alot of torque.


All I have to say is floor the car Although it felt like I had less torque, it pulled VERY well through all the rpms! It was awesome!

As soon as I connected my exhaust back up, it "felt" like I gained all my torque back. But the car still pulls really nice though the rpms thanks to the headers.



You only have one o2 sensor. It should be attached to your driver side header.

 

With the open Y pipe you are losing low speed torque due to poor exhaust scavenging. I gaurantee you that you are gaining both HP and TQ above 3000rpm though. Back pressure is bad, exhaust scavenging is good, those are the two major things you need to aim for when peicing together an exhaust system.

Once you have a catback hooked up, you will probably gain a little low end due to the better scavenging...but will lose in the higher RPM's due to the increased back pressure.

 

you arent lacking back pressure, you're lacking delta pulses. just attaching a cat to the end of it should probably bring back your torque. The delta pulses are what help the scavenging effect btw (if i recall correctly).

 

Everyone pretty much nailed about why your butt dyno is off. Remember, now would be a good time to get into chip work. Going from the stock tiny exhaust to a 3" exhaust has dramatically changed the volumetric efficiency of your car. Chip work will only make the most of your new found power. Some people make up to 10% changes in the VE tables on full exhaust 305 TBI's. Also, get that 02 plugged in so that you can run in normal closed loop.

 

I think I should clear some things up for u guys, I do have a cat convertor on the car that is attached to the y-pipe. But that lil tube that comes down that connects into the convertor is not connected. I dont know the car feels really sluggish. A chip is next on my list of mods also, hopefully a nice xmas gift Anyways whatever is wrong hopefully tommarrow when i take it into the shop and get the rest of the exhaust on, that will fix it. ANd he will be worth allm the money i put into this car.

 

Amke sure Santa Cluas brings you the equiptment to burn your own. Off the shelf chips will cause you more headaches. Besides suspension mods, chip work should always be on top the of the list for TBI cars.

 

I have a 305TPI not a 305TBI just so u know

 

To correct what tude i was talking about on my cat. conv. i guess its the egr valve that not connected.

 

All that tube going to the converter is for the air pump. It just puts extra air into the catalytic converter. Not having it hooked up will not cause the car to run sluggish... it will run fine.

 

Floor it

 

Got the car back today, feels awesome. Like Its right off the show room floor, i cant beleave it. I guess the reason it was running so sluggish was cause the spark plug wire were mixed up, so after we got that handeled it ran like a dream. I had them go ahead and install the new plug wires with the chrome brakets on the valve covers which also look great. the guy made the exhaust from the 3 inch cat 2.5" till it got to a 3 inch 40 series flowmaster muffler with dual outlets on one side. The guy did a great job, not too loud but not too quet. Beware **** burners for a muai blue formula :lala: :lala: :lala:

 

...so you had it converted from 3" to 2.5" ?

Please no heh. I'm glad things got straightened out with your car.