straight pipe for the 4cyl

lmayoral2191 · Dec 21, 2014

So I've had one on my car for a while, noticed some faults too having a straight pipe.. crappy idle, lacked power of the line ( lower power till like 3k ) and the best one... gas consumption. Dropped my gas mileage like 3mpg. Alright now the reason for my post, I bought the 02 sensor spacer that is straight plug and play. I checked 02 activity and the pattern is almost like I had a catalytic converter. Nice square wave on the primary and flat line on the secondary with the ocasional spike under wide open throttle. So I think it's safe too say that the spacer actually works, bought it on eBay for 4.95$ and my check engine light hasn't come back on. I don't know.if anyone has posted about this but I figured I would if anyone was curios. Here's the spacer I bought

Ty92x · Apr 5, 2015

You could be experiencing a lack of back pressure in the exhaust you wanna have a little bit of back pressure in the exhaust for the engine to run efficiently 3 psi at the most is about it... How big is your exhaust piping and is your engine NA or Boosted

Aman · Apr 6, 2015

^ I'm interested to hear what your exhaust diameter is as well.

Also, how does that O2 spacer fit? I'm thinking of getting one myself (cat is out), as a temporary CEL satisfier.

dwills1992 · Apr 9, 2015

Yeah, I did that to my 02 accord. Ended up getting a full cat back system and made my own de fouler to attach to my test pipe. Make sure you keep the resonator on or get an exhaust with a resonator. It will give you a beautiful sound and give you the back pressure to keep you car moving properly.

akoutmos · Apr 9, 2015

The loss of power and adverse affects I would say are from the measures the ECU is taking after seeing secondary O2 sensor readings. If the motor was tuned with a programmable ECU which doesn't make fuel and ignition adjustments for the sake of fuel economy and emissions, i would think your results would differ.

That said, it is still important to know what diameter piping you are using for your exhaust. I'll leave this tech article here from Cobb on exhaust system design: http://www.cobbtuning.com/Technical-Articles-s/70676.htm

The point to highlight is:

One thing I do want to explain before I get too far into this is backpressure. I hear "You need backpressure to make torque." all the time. And it even comes from "tuners" as well as customers. This is flat out not true. Before I arrived into the company of true tuners I fell into the same trap myself. The reality is that backpressure is the enemy. You want to keep it as low as possible. What you do want is to keep velocity up. However doing the things that keep velocity high involves slightly more backpressure under some conditions. You want to keep the gasses moving as quickly as possible to make both good torque and top end power. The perfect exhaust system would keep the gasses moving as fast as they did coming out of the cylinder and have zero backpressure. However this is impossible to achieve in the real world.

Ty92x · Apr 9, 2015

akoutmos said:
The loss of power and adverse affects I would say are from the measures the ECU is taking after seeing secondary O2 sensor readings. If the motor was tuned with a programmable ECU which doesn't make fuel and ignition adjustments for the sake of fuel economy and emissions, i would think your results would differ.

That said, it is still important to know what diameter piping you are using for your exhaust. I'll leave this tech article here from Cobb on exhaust system design: http://www.cobbtuning.com/Technical-Articles-s/70676.htm

The point to highlight is:

That quote is true if he has modified thing's to increase velocity out the exhaust that is why I asked if it was turbo or NA... But if you were to install a straight pipe with a larger diameter piping on a car that doesn't have much work done to increase velocity out the exhaust you are actually hurting your torque and hp by decreasing the velocity of the exhaust stream by increasing the piping diameter by to much

akoutmos · Apr 9, 2015

We'll have to wait and see what the piping size is, but my argument is that the stock ECU and it's fuel economy and emissions controls are what yielded these results. Seeing as the OP says that the spacer fixed the issues.