Engine feels very restricted - Any particular reason?

I’m relatively new to the ZX2. I made my first post in the General Discussion board: http://forum.zx2ms.com/index.php?topic=1727.0

After driving the ZX2 for a few days, I’ve noticed that the power curve is very strange. It seems to pull well until about 4500 or 5000 rpm, and then it just flat lines. Instead of continuing to pull well, it seems to just level off. Revolutions go up, all the way to redline, but it just doesn’t accelerate well until I shift to the next gear. This doesn’t seem right, because I use to drive a 2002 Focus ZTS with the 2.0L Zetec and a 5-speed, and that car pulled hard (well, as hard as a 130hp I4 will pull) all the way to redline. Is the ZX2 geared terribly? Is there some sort of serious restriction in the intake and/or exhaust? Or is there something wrong with mine? Thanks.

no it’s just tunning… pure and simple.

If you could get a video of inside the car, that would be awesome. I think it might something to do with your car, because my ATX Zx2 pulls hard after 3k all the way to 7k.

I’m just wondering…Does it flatline at 70mph? Because I know what it is if it does.

Video of inside the car? I don’t have a camera to get a video, but is there something in particular you’re looking for? I know my way around a car, and if there’s something you can tell me to look for, I’ll check. See, my brother has a 2002 ZX2 ATX, I’ve driven it once and thought it pulled all the way to redline, unlike my MTX.

I’ll take it for a spin this evening and see if it flat lines at 70. I can say that it flat lines at around 4500-5000 RPM in 1st, 2nd, and 3rd.

If in 1st, 2nd and 3rd then you might want to check MAF. Perhaps even a vaccum line.

:? Not sure about this one. :?

Well, I checked to see if it flat lined at 70 while accelerating, and I wouldn’t say it does. After looking at some specs, I see that the torque peaks at 4500 and the HP peaks at 5300…So, maybe I’m just feeling the drop off from after it hits peak? I would kind of like to do some simple mods, intake, exhaust, UDP, but I’m not looking to put a lot of money into this car, and I would like to keep the exhaust as quiet as possible.

in terms of exhaust and keeping it quite there are plenty of options.

There is the Borla Exhaust which was made for the zx2, thats a quite one, or you can go the Trubendz route with a magnaflow muffler (I run this setup). Its not loud at all and gives the car a nice tone to the exhaust, while letting people know when you open her up.

Quiet? Yes. Mean sounding, oh hell yes. I’m going to add a 2.5 exhaust to it soon.

hey bro i had the same problem with my zx2. what i did was i cleaned out the MAF sensor and the throttle body and disconnected the noc sensor because the ecu is programmed to have the timing retarded until 3,000 rpms and thats when the timing becomes regular. if you have an aftermarket air intake the noc sensor senses extra vibration so it makes the engine feel restricted so if you disconnect the sensor from the back of the engine it will have normal timing all the way through the rpms. i did all those steps and my engine runs way smoother.

Has this car had the timing belt replaced? Many tech.s make the mistake of just lining things up, marking the gears and hanging a new belt. I have tried doing it that way as a shortcut and then went back and performed the factory procedure of loosing the cam gears, setting the belt and then tightening the gears with the cams held by the special tool. Believe it or not, this one step means quite a bit to the upper end of the power band. Also, have the oil pressure checked with a mechanical gauge, if you cannot maintain 50+ psi from 1500rpm on up, the VCT will not act properly and you will loose ooomph in the upper rpm range. My trusty rusty Mexican Mazda pulls all the way to the rev limiter now that my belt is set properly. As mentioned before, a fouled MAF sensor and or restricted air filter can also affect things. A quick indicator of MAF/air filter trouble is to have the scan data checked paying particular attention to the assumed baro value. Down here at sea level I want to see 101-103 kpa depending on the weather. If yours is reading 95 or less below 2,000 feet of elevation then you will be lean and lacking power. Sometimes this is typified by persistent detonation when holding steady cruise to light acceleration.