Does anyone know an proximate relationship of CR and ignition timing increase/decrease assuming all other engine specs are same other than CR changes?
I am looking at using a very well developed ignition table from VP engine on my VR with basically the same mods as a base map to massage when I hit the dyno this weekend. Would be far easier than trying to fix that awful stock table
How much should I decrease the table by % in order to be close to optimal but still safe enough?
Table is from 8.5 CR going to a 9 CR engine with virtually same mods.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
i''d say compare a stock VP and VR timing map and see what the average differences are, that number might be as much as 4-6 degrees to account for the increased compression.
No matter what the question is, the answer is always more horsepower!
its hard to compare. factory maps are all over the shop and spiky as! the APNX and BLCD I have compared before, were there is a trough in one, its a spike in the other.
I have the greenfoam one out of my VP, I took a read the other day and its excellent! smooth as and good timing everywhere.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
Do the VP and VR have the same cams and timing set ? There's more than just compression that effects timing. Auto v manual, diff gears, weight of car etc etc dictate how quick u can feed the advance in. Make sure you don't forget fresh fuel as well !
had a look at the vn map verse vr its about 5º less in the VR but the greenfoam's one is about 5-10º more in the mid and cruise areas over the VN one and up to 20º more than the VR ones in the same areas.
high load area are similar from VN to greenfoam and even almost the same as my tweaks to those areas on the VR.
I reckon I should get very good ball park with all of this.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
no, I found legit cam specs for both and VN is more lift and duration, but the VP onward has more aggressive ramp rate so the lob profile area is larger somewhat in the later cam.
Those specs were total duration iirc not the .050 duration? So Im guessing later cam might have slightly more duration when measuring from 0.050"
VN definitely has more lift than later cam, thats for sure.
Last edited by vlad01 on Thu Feb 26, 2015 8:45 am, edited 1 time in total.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
