Is there any negative consequence to running an open header (thread http://forums.maxima.org/showthread.php?threadid=63592) at the drag strip? I heard (yes the infamous "heard") from people up there that it is bad for the engine. Some people told me valves would get over run, others tell me that pistons... My take on it, is how could running an open exhaust hurt anything just by having zero back pressure? It obviously changed my torque/hp curve. And its not like I was running a turbo or a S/C or No2. I also figure that Nissan built this engine to be very strong and running it hard with open exhaust/no back pressure wouldnt do anything. So far the car has not exhibited signs of motor failure yet, but whats the real scoop here?

 

I used to have an exhaust cut-out, and I thought it was the holy grail of mods, until my engine started to feel it. Now everyone tells me that Nissan designed the engine to run smooth with the backpressure, that's what makes the vq run so nice. I don't know if the open headers would hurt the engine too much just running them on the drag, but the noise is crazy, and it's not good for your engine in everyday driving. I recommend you go with a dump valve so that you have the choice of open or closed, it's better for a drag/ regular driving car. Just my 2 cents... good luck.

 

I think your biggest problems would be with your O2 sensors, your engine relies on them a lot and you're not getting good readings with them flapping in the breeze. Probably stand a pretty good chance of killing an O2 sensor for that matter.

 

Let me get this right, you dropped your whole exhaust (y-pipe, cat, b-pipe, and muffler)? So technically you're running with no O2 sensors, right? If this is correct, your car has to be insanely loud. With no O2 sensors, the ECU has no way of correcting fuel to air ratios. The ECU throws a code (like yours did) and then selects a preset program that use air/fuel ratios. This is kind of a limp home mod that keeps the engine running, but not quite efficently nor at max power. At full throttle, the O2 sensors aren't monitiored so it's not really a factor.

Backpressure is NOT GOOD. Simply put, you don't want it and Nissan didn't design it into the engine and exhaust. The reason your engine "curves" have changed is because the flow characteristics have changed. The exhaust flow is very turbulent and is not direct. Simply put, your exhaust velocity has gone to ****. There is absolutely no exhaust scavenging which is needed to produce torque. Backpressure doesn't produce torque. It is very possible that you could screw up your motor running like this (valves, rings,etc).


Dave

 

wow.
so reducing that "back pressure" that doesn't screw it up? Doesn't freeflow exhaust and y/b pipes do just that?
I thought that they were performance mods and all.
I'm not trying to create an argument... I'm just interested

 

I dropped the Y pipe, Cat, and B pipe, but the muffler remained on the car, just cause I just got a Stillen B pipe I'm in the process of putting on. So yea it was running open manifold, and the O2 sensors were tied to whatever was close by just so they wouldnt bang around.

I wish someone had gotten it on camera. It was LOUD alright! It wasnt so bad in the car with the windows up while I was going down the track, but I dropped the windows and sunroof as soon as I crossed to the other side so I wont die from carbon monoxide.

I'm not following here... are you saying back pressure is not good and on the other hand you're saying running open manifolds (which is probably the least amount of back pressure aside from open block) could damage the motor? I'm not by any means trying to start a fight, just trying to get a better understanding.

I honestly think I can do even better then a 14.6, had my clutch not been slipping. If I had unlimited passes I would toy with shift points, shift style, launching, etc etc etc. So many variables..... but I'm happy I finally got into the 14s.