I was looking up info on this mod, which I seriously want to do, and I've read from one person that it took a while for his engine to "break in" and start to really scream with the S50 camshafts and a JC custom chip installed. According to this report, the cams fill in the higher RPM power drop where the VANOS system on the stock cams starts to lose it's juice.
I've also read that the stock fuel system on the 325iS isn't beefy enough to keep the car from leaning out on the M3 cams once the revs get close to the up rated 7k rpm fuel cut. So long track days see alot of heat and obviously there is a decent amount of lost horsepower. I've only found a single post about this so I don't know if it was specific to this one guy's car, if it was just because he didn't know what he was doing (unlikely since he fixed the problem with uprated injectors and a SMT-6 on a dyno) or if this is something I really need to be concerned about when I do this mod on whatever 325iS I end up finding.
I also haven't found a single dyno chart to show the difference between stock cams and M3 cams. One of the symptoms that I'm reading about consistently is that the horsepower really doesn't want to continue to climb past 6500rpm or so, so the uprated fuel cut doesn't do much good unless you really need to hang onto a lower gear.
I just started looking for info in earnest, and I'm going to be performing this as my first mod, so I want to ensure that it's done right. If I am going to need M3 injectors and an SMT-6 to fill the fuel gap and keep the a/f optimal, I want to know now so I can do research on other fuel hungry mods to think about doing...
Addicted to Speed Since 1997 Founding member of the GreenDragon Poo Flingers Club
Founder and Double Member of the 150mph club
Hmm interesting. I've not done much research into cam swaping on a vanos engine so I can't help you out much.
What I can tell you is that the power DEFINETLY runs out at 6500-6600 rpms and that the chug to 7000 seems almost painful with the stock 92 cams. Perhaps I'll look into bigger injectors but anything I've read about them is there's more than enough fuel to fill the camber with the stock injectors. Perhaps it's just the combination of the cams with the smaller valves?
Now I think I'll do some research into this.
__________________ Kevin (President TBEA)
"WAAAAAAARRRRRIORS, come out to plaaaaay."
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