CA18DET Trouble: Wide open throttle, engine will not pull.

[Buddyworm]

So I'm tuning a friend's engine. Freshly built, forged internals. Beautiful rig with the 10.whatever lift Tomei procams in a 260/270 split, adjustable cam gears, Z32 MAF and 550CC injectors, Greddy TD05-18G.

This thing will NOT rev above ~5500 RPM. It'll drive and accelerate like a limp noodle but it just doesn't have any real pull anywhere in the rev band.

It'll go pig rich with the throttle matted, but it seems like the engine just refuses to suck in any more air. I know the turbo is pushing because the profec B reads roughly 13 psi. The engine doesn't buck and the exhaust doesn't pop or spit all that much (for a straight piped car) but you can hear the combustion quality is suffering.

At idle, once warm, the AFR will bounce between 12 and 16 randomly. Under low load cruise I can dial the K constant in but I'm still chasing a stable idle AFR with this thing. The idle control accessories are removed and idle is set with the throttle body screw, which could cause that problem... Consult shows TPS idle when foot is off the gas.

I've tuned several of these engines with similar turbos (TD05-14b, TD06-17c) and one with only slightly smaller cams (HKS 264's IIRC) and all of those engines screamed effortlessly to redline on conservative base maps.

So, I have two major suspects for this problem:

1) His cam timing is out. Way out. My thinking is that since they actuate and time the valve opening events the essentially dictate how much air the engine can pump at any given RPM. But here's where things get a bit beyond my ken. I do not know how to degree bumpsticks like these procams, much less diagnose the exact problem if these things actually are the cause.

2) The TD05 hot side with the 18G cold side is the wrong turbo for this engine. Keep in mind that's not a typo, typically the 18G compressor wheel comes with the TD06 hot side, which is larger than the TD05. So maybe the TD05 turbine housing is too restrictive for this kind of setup? Especially since the 18G wheel is good for ~400hp on these engines, properly tuned.


That's about all I can think of. His CAS seems to read fine, MAF reads properly, timing set to 10* BTDC. Anybody got any ideas??

Any leads we can start chasing down would be very much appreciated. The current basemap is attached.

[Zenki]

hi,

can you make a screenshot from
the inition map -value-> filtered value
the fuel map -value->AFR

My laptop @ work has no nistune

[Matt]

My only thoughts are to check for any potential exhaust (cat converter or muffler) or intake restrictions (collapsing intake piping or filter)

Watch the timing gauge at the point where you are having the issue