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[FreshDA9]

I dont mess with ignition tables as much as i should since i cannot actually see much change like in a wideband while street tuning. im working on my buddys B16 and he has crower stage 2-3/4 cams in this  ... i notice with a stock map it idles at 13inv i have got it to sit at 16-17inv with 22-25 degrees of timing. my balls dropped a little more and i uped some more and got it to move to 19-20inv i didint save that map but i be leave i was at 36-38 degrees and feel im playing with fire. this is all at idle. i raised his vtec to 5800rpm but when we actually get to the dyno we will see where that sits. how should i set up the mid range ignition timing, any pointers. And no i didnt post on PGMFI because RHMT is the shit and faster with results 

[FreshDA9]

Also here is a screen shot of the cam card that crower directed me to. we dont have the tools to degree it but crower said these cams are best at 4degrees advanced on the intake and 4 retarded on the exhaust so we split it in half and did 2 degrees on the cam gears advanced and retarded. (Crower said we could have them at 0 degrees and the would be fine so we just choose to do 2 degrees instead of the 4).

[98vtec]

what is the base timing?

[FreshDA9]

ill take a screen shot on my laptop when i get home and post it. this is a stock bre map i went off of and then started advancing.

[Joseph Davis]

Pics don't show up on my phone, but what's a Crower 2-3/4 cam?

[98vtec]

Lol.  No pics here either

[dvst8r]

The picture shows the cam specs, says part number: 63402-2, Grind number: special.

[FreshDA9]

The picture is of the Crower Cam card. it cannot be a special grind because its offered on their site with those specs on the cam card. they are NA cams with the crower valve train to match.

When i get home and get onto my laptop ill post some screen shots of ignition and even post maps and logs for you guys.

[98vtec]

Stock compression?  At low loads you can typically run a much higher ignition advance even with higher compression than stock.  Keep your ears open, watch the plugs and the torque graph for losses and gains.

[lilpooh21186]

What type of dyno will you be using?

[FreshDA9]

98vtec thank you for some input i didnt here any signs of knock i do need to pull the plugs and examine them. it wont hit the dyno for a little bit im trying to street tune it before we get to the dyno. i am using a Dynojet 2wd non load bearing so im trying to fill in some of the map during the street tune. but when im on the dyno i can actually overlay the runs and watch the tq graph.

yes car is stock compression. here is a screen shot of the map timing table i beleave this one is sitting around 16-17inv. i did not save the other map but when i go back over to do some more street tuning ill save it.

[HiProfile]

At idle, bigger cams basicly exhale intake charge before the ex valves seal, as well as a bit before in valves seal. The much lower V.E. at low speeds means much less air is in the cylinder when it compresses. Thus the extra timing, since a less dense charge requires more timing to get the peak cyl pressure you want/need.

At higher speeds you've got a whole shitload of things happening that the cam oddities now work with. Pulse waves, scavenging, etc - they all lead up to >100% VE in some cases. In layman's terms, it's using the intake and exhaust gasses as rubber bands to pull more air in.

[Joseph Davis]

At idle, bigger cams basicly exhale intake charge before the ex valves seal

Nope.  If it did that, then intake manifold vacuum would be higher.

Think about it.  What's happening here?

[jabberwock]

Pistons are dwelling without valve sealing, some gets blown back up the intake, vacuum suffers!


?

[HiProfile]

At idle, bigger cams basicly exhale intake charge before the ex valves seal

Nope.  If it did that, then intake manifold vacuum would be higher.

Think about it.  What's happening here?

Okay I messed up there, it's injesting exhaust instead. The extra overlap/cam timing leads to reversion, so it pulls even less air from the IM. [/quote]

I didn't read the rest of the crap you just typed, but that's it right there.   :yes:

[Joseph Davis]

Okay, I just screwed up and edited instead of quoted?  Sorry about that, but you get the idea of what I meant to say even if all that other crap got accidentally deleted.     

[FreshDA9]

So your saying or meaning the exhaust is bleeding back in because of the more duration. so more advancing would fix this problem by letting more air in from the intake manifold.

[BangBusMaster]

Slam dizzy to firewall. Go WOT.

[runsfromdacops]

Slam dizzy to firewall. Go WOT.

that shit didnt work on my car

[HiProfile]

Okay, I just screwed up and edited instead of quoted? Sorry about that, but you get the idea of what I meant to say even if all that other crap got accidentally deleted.   

wow. epic quote fail. 

The rest was a continuation of what I said earlier. I was mixing up why huge amounts of overlap were bad for blowers, as I thinking how I could use that for comparison.

So your saying or meaning the exhaust is bleeding back in because of the more duration. so more advancing would fix this problem by letting more air in from the intake manifold.

Advancing the CAM timing would lead to less intake charge bleed-off, but then you'd be losing one of the cam's reasons for making upper-rpm power. Depending on the cam, it would also open the exhaust too early after advancing - you'd be letting exhaust out before it's done pushing the piston down.

That's why dohc vtec actually helps with crazy cams - you get a cam profile that idles and another that screams to redline.