Cam choice - Too Small?

[Jeda]

I got my car back on Monday night.
Went for a short drive to just to see how it drove. I kept it under 2800 rpm as it was raining heavily and didn't want it to catch me out unexpectedly.

With this cam, the car rocks. Literally. At idle in park, and more so in drive when stopped. A bit too much for me to be perfectly honest, but can probably be tuned out.
When driving, a little flat spot around 1200-1300rpm, but after that it's business as usual and drives well.

There's another thread about excessive fuel smell after cam upgrade, and mines no different. I've spoken to the tuner who says it's not running rich, with a target afr of around 14.7 at idle, with +-5% after it's at operating temp.
Don't know if that's correct, and I haven't put my scan tool on it to check if that's the actual afr, but I will.

Given that I run GMM triple stepped headers, 100cel cats and 3" system, I did expect the additional funk, but definitely underestimated it.
I'll have it retuned later on as I do believe it can be better.

The surprising thing that I noticed was that the drone I used to experience at just under 2k has all but gone.

The afm was deactivated in the tune last year when I had the bolt on mods done, but the DOD hardware was still there. Somehow the characteristics of the new valve train/cam have deleted the drone.

For those who are interested in dyno numbers, the car dyno'd at 276rwkw with bolt on mods, and 321rwkw with the cam upgrade.

Now, I didn't drive the car properly until yesterday and still can't say if any of the numbers above are anywhere near actual or accurate.

I can say that this is now a completely different car and certainly feels like it's a heap more than a 45rwkw difference.

Either the initial dyno reading where i had the bolt-ons done was way too optimistic, or this latest dyno under reads. But once it grips, it pulls so bloody hard.
The downside is that the car is now WAY under tyred.

 

[07GTS]

the issue with camshafts is that there is now unburnt fuel when it gets injected a small amount (because of overlap) at low rpm gets sucked straight out the exhaust port, this dosnt affect the afr as its unburnt fuel and 02 sensors only sense oxygen not raw fuel but by the time is thru the exhaust it smells, so ur not ''rich'' as such just a different affect from the camshaft as factory injects to the closed intake valve so soon as it opens with camshaft u now have the smell issue

 

[Deuce]

the issue with camshafts is that there is now unburnt fuel when it gets injected a small amount (because of overlap) at low rpm gets sucked straight out the exhaust port, this dosnt affect the afr as its unburnt fuel and 02 sensors only sense oxygen not raw fuel but by the time is thru the exhaust it smells, so ur not ''rich'' as such just a different affect from the camshaft as factory injects to the closed intake valve so soon as it opens with camshaft u now have the smell issue

Is it possible to delay the time of fuel injection by say 10° with these?
Hopefully finish the overlap cycle before injection starts.
And hopefully still have good air/fuel mixture.

 

[losh1971]

321kw is about right for the average cam.

 

[07GTS]

Is it possible to delay the time of fuel injection by say 10° with these?
Hopefully finish the overlap cycle before injection starts.
And hopefully still have good air/fuel mixture.

yep thats the EOIT that is sometimes mentioned ''end of injection target'' it can help more then some think even better drivability and torque, gen3 is hard to use but the gen4 it works quite well, u can see when u start to delay it the fuel trims or wideband start to go richer meaning more of the injected fuel is getting burnt in the chamber, once u have that at its richest point then adjust the fueling tables (also cruise and all light to med throttle will have to be checked) then its good to go, i saved about 13% fuel at idle just by adjusting it with my old camshaft, u just dont want to delay it too much as with camshaft u also get the piston on way back up pushes some back out the intake valve before it closes as well as it not mixing in as well if its too late

 

[Jeda]

321kw is about right for the average cam.

Thanks losh.
To put what i said earlier into context regarding dyno numbers, the seat of pants feel going from stock at around 220rwkw to 276rwkw is nowhere near as profound as the jump from 276 to 321.
This is why I believe the first dyno reading must've been on the happy side.

Whatever it is, aside from the smell and the flat spot, it's powerfull enough.



















For now..

 

[losh1971]

Yeah my cam starts to come alive at 3300 thereabouts, and gets really lively from about 4000-5000. I haven't tried it out properly as the road is not really a place to do that. Plus I still have the weak link in the "drive chain....."