The V8 Owners Forum -

After running a safe map while on boost which was a flat 11.4 deg adv from 2500 up to 6000rpm ran a 12.38 1/4 on this setting,
we have now started upping the advance and testing in between,

currently we are now at 14.0 deg adv at 2500rpm climbing to 14.9 deg adv at 6k and no det so far, just wondering how far I can really push it,
not been to the track yet with the current settings.

hi Tony
what is the static CR are you running? what is the cam timing, particularly when does the inlet valve close? how much boost are you running at peak torque?
Best regards
Mike

good question Mike,
its a decked 4.6 block with 4.0 high comp crowns on 4.6 rods, 30cc chamber heads and comp head gaskets, (I measured them so maybe 33 lol)
cam specs: http://www.crower.com/camshafts/buick/2 ... 0-hdp.html

boost is progressive but max boost at 5.9k was 14psi.

Hi Tony
I would think a starting point would be 17 degrees @ 2500 rising to 21 at 4500 then up to 23 at 5200 then hold it a that to 5400 then advance it to 26 degrees at 6500.
I think that should be a good starting point without it pinking, I would be careful adding timing between 4300 and 5500 unless you have access to detonation detectors in your block.
You could always stick the timing curve out the slingshot into yours just run it on Meth, I run a fairly "conservative" 11.6:1 cr and 36 degrees of advance at 5200 rising to 39 at 8000
best regards
Mike

im running dual knock sensors if that helps?

Hi Tony
I think you are running about 10.2:1 CR and about 6.5 PSI boost at 4400 to 4600 revs, at a guess around peak torque and best Volumetric efficiency. with that cam you should have a little in hand at peek torque before it starts detonating, but I would be careful.
best regards
Mike

cheers Mike,
im going to slowly add 1 degree at a time like we have been doing now,
will take a while but safe way of doing it,
will get a screen shot of my boost ignition table,

OK Tony,
I presume you can log the knock sensors?? you could stick a pair of Exhaust gas temp sensors in the exhaust headers and see what temps they are running at. It would tell you if you are running too retarded, the knock sensors would keep you safe on the advance and home you in on the right advance a bit quicker.
best regards
Mike

if knock is detected it takes 10deg out straight away then feeds it back in 2 degrees at a time

Coops wrote:After running a safe map while on boost which was a flat 11.4 deg adv from 2500 up to 6000rpm ran a 12.38 1/4 on this setting,
we have now started upping the advance and testing in between,

currently we are now at 14.0 deg adv at 2500rpm climbing to 14.9 deg adv at 6k and no det so far, just wondering how far I can really push it,
not been to the track yet with the current settings.

I assume you're making almost no boost at 2500rpm ?

If so, then you should be running close to n/a timing there which could easily be 28-30deg

You could leave the high rpm/boost at around 15deg for now, but low down and mid rpm needs a huge bump, and it will make a huge difference to how the car feels.

There really is no reason to be running such low timing at low rpm/boost.

it was a safe thing stevie to make sure everything was ok,

what would you change then?

Exactly what I said.

Low-mid rpm sites circa 100kpa can easily be 28-30deg, as per n/a engines, because at that point is is a normally aspirated engine..

Then as boost rises you can tailor it down to your current 15deg at the same max rpm and boost.

Also...I know it's only a screenshot...but I assume you do have load sites below 100kpa ?

If we ignore rpm for a second and keep it very simple..From say 2500rpm upwards

Say row 100kpa 29deg, 110kpa 27 deg, 120kpa 25, 130kpa 23, 140kpa 21, 150kpa 19, 170kpa 17, 180kpa, 15.

Higher rpm sites may be able to take a little more timing, simply because of the higher rpm.

High vacuum, cruise sites etc could easily be into the 40's

Say 1000-2000, 2500 could be from say 15-20deg around or just off idle, rising to the aforementioned numbers.

Most engines will have all the timing ramped in by 2-2500rpm anyway

upload or email the map file.

Might be easier to do that so it's displayed on same format etc

will mail you the msq file later mate,
I run split maps by the way, on fuel and ignition,
one map goes from 10kpa to 100, then second goes 100 to 190 so have mainly a start idle and cruise map and one that runs around on boost,