My cousin is thinking about installing the HKS 264 cams on his Z33 and we would like to know if changing the stock cams with the HKS cams (or any other more aggressive cam) would make the car run richer or leaner? The reason why I'm asking is because his car already has the TS flash for his mods and he would like to know if the car would run fine w/o a retune. Thanks.

 

retune would always be better. but im not sure if its needed. depends on the size

 

Well, to go to the expense and trouble of installing cams, your cousin should definitely get a BEFORE and AFTER dyno with AFR measurement, the cost of dyno is nothing compared to cams and install.

Chances are yes the AFR will change quite a bit.

 

We definately are going to do this. We are just wondering if the cams will make the car run pig rich or dangerously lean before we tune it.

 

My guess is more rich if anything, as you are allowing a longer duration for gas to enter.

 

Im guessing here , but isnt the injector pulse width set ? And going to a longer duration with the same injector pulse width , allow more air and the same fuel ? This would cause a leaner A/F ?

 

sorry, my knowledge doesn't extend this far into the 21st century. I need a carb to be in my element.

 

How long do you plan on driving the car before getting it tuned?

 

You are correct; a longer duration cam will allow more air which will cause the A/F ratio to become leaner. The 02 sensor will sense the leaner mixture and adjust the fuel parameters, but it won't be enough. So the OP should definitely get a retune before or shortly after installing the cams.

 

The last time he dynoed his AFR was @ 13 from 1.5k - redline. Would it be safe to assume that going to a 264 deg. cam would raise his AFR @ 1/2 a point higher?

 

Not more than 2-3 weeks.

 

Only in closed loop. In open loop, the ECU usually just goes off preset maps and ignores the o2 feedback since it becomes unreliable and cannot be trusted at mid and high loads.

My guess is that extended duration and/or lift will not make much difference. Why? Because the ECU meters the air entering the engine using the MAF. If you extend the duration or lift, whatever extra air you take in, the same amount of air must flow past the MAF sensor and the ECU will know about it. The ECU should adjust the IPW and it should be close to correct.

If you're running with a MAP sensor, then yes, you'll need a retune since your volumetric efficiency has changed and MAP calibration is greatly dependent on correct VE table.

 

I see. Hyopthetically speaking would the ECU be able to adjust IPW in open loop (WOT runs)? Thanks.

 

im untuned right now on tomei 264 cams and im lean till 3k and rich (11.5-12) after that. i would suggest tuning as long as you spend the money to put cams in (tomeis run 1000-1400 depending on what deal you find, then another 1000-2000 for install, and another 1000 at least for tuning and software). i know im running like a slug ~255whp now as compared to 268whp when i was tuned but un cammed.

 

I remember your thread. Aren't you on your stock maps?

 

im running NISMO 264 cams untuned and running alittle rich

 

yes sir i am! i am running the 0 map or base map. i know its hard to blow a n/a z up but i figured my safest bet is to let the stock ecu do its thing until it gets tuned. the car has been driven about 700 miles since the cams went in and as long as i dont go above 3k i get GREAT gas milage (i average 27 mpg on the hwy). but since i do ALOT of city driving being that my school is next to the capital building i average 16 mpg. hopefully my shop will pull through this time and ill be tuned next week. and i hope so for my wallets sake

what did you do after you got your cams in? and what gains did you see?

 

It should. IPW is calculated based on how much air you're taking in.

All of this is what I think will happen. Based on some feedback, sounds like results may vary. There could be other factors at play here as well. It's not un-usual that certain cylinders get more or less air than others and some run richer/leaner than others. Sometimes factory programming is done account for these variations. Changing cams may change this behavior and could upset that balance.

 

Unfortunately, I didnt do a before & after after I got the cams installed (I have been using them for almost two years). I baselined @ 210whp (at sealevel) stock and I got 248whp (1200ft above sealevel) untuned with cams/headers/exhaust/Testpipes/K&N filter/Spacer.


How do your Tomei's idle? Did you have to bump the idle?

 

they idle nicely, you can hear a slight lope but nothing major(hopefully the bf will let me take the camcorder to the shop next wed when i tune so i can get some sound clips of my Z and ch@dbee's), def doesnt sound much like the Z she started as. i didnt have to bump my idle.

i dynoed 240 untuned with boltons and 255 untuned with cams. ill be bumping my redline up a lil so well see what all happens. thanks for the info