no longer a cam virgin :)

[The Alchemist]

hey there people, exciting times this week at work as we have installed our first cam upgrade on a VY2 LS1.
The cam installed was a Crow cam number 871275 218/224 0.525 lift 114 lobe centers. We also installed new springs
http://www.crowcams.com.au/templates...amshafts.shtml

Anyway, not knowing what to expect we got stuck in tuning the VE with ben factor overlays and sorting timing etc etc.
Power went from 220 kw (dyno dynamics) to 238kw with a solid 10% torque increase across the entire RPM range.

Fuel was 98 Octane. Peak torque timing was only 14.5 degrees and peak rpm timing was 17 degrees and that was all it wanted. AFR's 12.7:1.

Now, question for all the non cam virgins out there :
Is this a reasonable or expected gain from such a cam upgrade? Nothing else was changed on the engine except the tuning of course....

[ringram]

That timing is weird dude. Whats the dynamic compression with that cam?
Id have expected at least 20* timing.
What intake and exhaust are you running? If its stock that might explain the timing its probably hardly breathing at all and charge is full of hot exhaust gases. Get a nice OTRACI on there and a full set of headers and catback (or even better lose the cats). You should double your gains and more. I made 290rwkw with a 220/224 cam.

[The Alchemist]

Hi Ringram, howsit goin?
This car already has a full set of Remus headers and twin 2 1/2 inch exhuast and a OTRACI with K&N filter. T/B is standard, manifold is standard.

I see other similar cam packages on the net making 250+ on Dyno dynamics dyno in Aussie and I must say I thought the timing low as well. The car used to like 17 deg at peak torq and 22 deg in the top end before the cam upgrade

But its the net increase of 20 kw which I thought seemed a bit low but hey Its the first one I've done so what would I know

I am logging knock retard at present as a guide but also noting the tractive effort during the dyno run.
Could the knock be over sensitive with the cam change? Do any of you detune the knock during tuning?

cheers Mike

[johnv]

Are you tuneing Mafless ?
My 224/224 made 270rwkw with maf and aroung 290 mafless with all the boltons and would take 25 deg timing wot no probs

[The Alchemist]

Hey John, thats wot I wanted to hear
its a weird conumdron
I am tuning mafless with the OTR intake > MAF long gone mate
Was that with a dyno dynamics dyno ? If not I can't compare the figures fairly.......but the 25 deg has got me interested!
Maybe its false knock? I'm going to zero the knock retard tomorrow and do full throttle loads at fixed rpms and use the delta spark to check tractive effort.
Mike

[The Alchemist]

Well I tried turning knock retard off and nailed it at 3000rpm and funnily enough I wound another 7 degrees into it and the tractive effort went nuts > damn the false knock !
Ended up at 20.5 degrees at peak torque with another 3% torque gain BUT the 238kw top end didn't budge even when I gave it 25 degrees. Had the knock ear phones on, it didn't knock, just made no more power. Ended up at 22 degrees at 6000rpm with no change.
There seems to be a restriction from about 5000rpm onwards where the torque just starts to drop away and is unresponsive to timing or fuel changes.
Any ideas what this could be. The engine has headers with 2 1/4 inch out, gutted cats and the HSV twin 2 1/2 inch exhuast, an OTR CAI with K&N, standard T/B & manifold.

Cheers,

Mike

[ringram]

Did you change valve springs? What intake have you got? You could port your stock TB and probably help breathing at the top end. You will need better springs to control higher rpm too.

Torque will drop after 5000rpm anyway. Peak is probably around 4700 with that cam. Try leaning WOT out to 13:1 the US guys say thats the best AFR for max HP. Perhaps a touch richer at PK TQ though, 12.8:1 etc.
And definately port your TB if its a stocky. It shoudl gain you something up top for sure.

Timing sounds better. You can zero Burst Knock Retard, like most of us do. Id keep the normal knock tables in there though. Take a look at some of the various years knock tables, you might be able to slightly detune them. Say a 300kw GTS and an 05 SS Commodore etc.

Dont worry, it takes a while to get the best out of it. My cam install started at 260kw and over a year of messing about with headers, fast90 intake etc, etc I finally arrived at 290kw thats on 97 octane. I should try 99 shell stuff, but its way too expensive here. I already pay near to $3NZ a litre (£1). Higer octane is like £1.20L !!

You can tell if you have an intake restriction if you MAP at key on is more than your MAP under full throttle. (ie) if MAP is 100kpa on ign (no engine running) and only 95kpa at WOT then you should gain another 5% power when you get that missing 5% air into the engine via a better intake or throttle body.

[johnv]

That cam dosent have alot of lift at .525" but I would def expect closer to 250 rwkw out of that combo.

power falling off early sounds like valve float but I see you changed springs!

Ported throttle body may gain 4 or 5 rwkw and improve throttle response (I port them by the way) but there must be a restriction somewhere still.
What sort of headers ?
Not sure the HSV exhaust is doing you any favours either !

[GMPX]

That is the same as my cam (it's a Crow too), mine made about 270RWKW (On a Dyno Dynamics) a few years ago, but it also has had some mild head work too and a Starr TB, but a pretty crap exhaust (but maybe not as bad as a HSV one )
On the street it pulls pretty strong everywhere and makes power all the way to the limit.
PM me your Email address and I'll send you my tune, mid 12 AFR's at WOT all the way, 0 knock on 98 (Mines a auto with 3.73's too).
In the end, if the AFR's are good and that is all the timing it can take then that might be it (assuming the engine is mechanically sound).

Cheers,
Ross

[ringram]

Could be a case of a bit here and there adding up. (ie) Headers+Throttle+Intake Manifold+something else=missing power...
If you advanced the cam on purpose or mistake more than normal, that might also explain it.