What causes this dip in power between 3.5-4.5? Shitty tune? Too much fuel? Not enough timing?

 

igition sucks *******, whoever tuned that ...must suck big time, either that or those wheels are spinning on the dyno, what sur setup i'm sure i can help u.

 

WHat a horrible tune! Do you have a chart of your AFR as well?

What is your setup BTW?

 

where is your vtec set at?
you really have to try to *** up timing like that
post ig timing maps

as per fuel; to create such a power drop, the AF woul have to change DRAMATICALLY at that point in the rpm range.

 

Where is you vetc crossover set?

 

my setup is:
2nd gen b16a, milled .030", crane stage 2 cams and valve train, cam gears at +2, -2 (which is really 0,-4, but has been changed to +2,+2 to help it idle), crappy DC 4-1 header, stock cat and 2.25" exhaust. Tuned with a chipped p28 (unknown program w/vtec at 4800rpms?!?!?!) but the vtec x-over is set to 5200rpm and tuned with the vafc2.
I've since added an AEBS IM, fakedata IM gasket, 64mm t/b, 4-2-1 header w/2.5" collector, 2.5" high flow cat, 2.5" exhaust. It pulls much harder and all the way up to 8500rpms now.
I've also got a PLX M-300 b/c i suspected a shitty tune, and sure enough it was running an unsteady 12-12.5 afr from about 2000-5000 where it leaned out a bit to around 12.9 all the way to 8500rpms. So in a sucessful attemp to lean it out a bit i changed the vafc settings down a bit to only about 3-5% increase on the wide throttle and its pretty close to 13-13.3 and it feels like it pulls a little better, especially up top.
I've also got a BURN1 and spare chipped p28 with a DKU-5 (but not hooked up yet, because i don't have a laptop) to datalog with.
So what i was thinking was just burning a p30 bin w/5-7% more fuel in 8,9,10 (crome) and going from there. Anythings got to be better than the unknown chip in my current p28.
And what do you guys think of maybe advancing the ignition timing a bit at idle to help it idle a little better. Its kinda lumpy, but i've heard other people complain about the idle with crane's stage 2 cams.

 

bump for some input.

 

well in all the years i've been tuning i've stuck to alot of different things, one is, when advancing your timing on street tuning wise, make sure ur dizzy is first set at 16 degrees, i have mine set at 18, i like that top end vtak, secondly just advance ur timing by 2 degress, make a second gear pull down some lonely street and se ehow it feels, the more you advance it, the more fuel u should burn but u should first get your fuel maps set str8 at 12.9, which is th emost ideal fuel AFR for all motor cars, that AFR is pretty much universial, but i'd say after u get ur fuel maps, start messing with igition, but tune your low / High cam at different times, i'm sure ur learning so i'll explain, make sure to disable vtec or set vtec to like 11k, while your tuning low cam so u can completely tune it out, its safe to tune low cam up to around 6k, then engage vtec at 3000, and tune your high cam all the way to redline, after you've done that, switch back over to low cam, disable vtec, and start ur advacing of timing, the more ur burning of fuel the more power you are making, however you may make great power, but listen for tinks, or valve tap and what not dont adjust too much, if you hear those noise, dont sweat it, just back your timing off 2 degrees and your set, i'm running my dizzy set at 18 degrees and 28 degrees advanced timing on my ecu using crome, i make great poewr i believe i can take it up to 30 and see how i do.. but thats just some more info, if u ned naymore walk threws with crom elemme know i'll be glad to help you out.

 

when you say "the more you advance it, the more fuel u should burn" does that mean that when i advance the ignition timing the afr will lean out a little?
Also, i have adjustable cam gears and right now they're just set to +2 +2 (0 0 really since my head is milled). When adjusting them, do i just advance the intake 1 degree and retard the exhaust 1 degree and see if it gains anything? And repeat until the gains stop?
Will adjusting the cam gears affect the afr?
I know i will need to adjust the dizzy if i advance/retard the intake cam gear to set it back to 16.
Now, advancing the intake cam and retarding the exhaust cam will creat MORE overlap correct? And more overlap is desirable on N/A engines, right?
But doesn't more overlap mean a lumpier idle? And more fuel consumption?

 

if you set the vtec to high or to low you can damage the enigne due to oil pressure or screwing up the rocker arms

the smoothing setting ont he dyno can also cause that choppy **** on the chart... its not always a misfire

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">when you say "the more you advance it, the more fuel u should burn" does that mean that when i advance the ignition timing the afr will lean out a little?
Also, i have adjustable cam gears and right now they're just set to +2 +2 (0 0 really since my head is milled). When adjusting them, do i just advance the intake 1 degree and retard the exhaust 1 degree and see if it gains anything? And repeat until the gains stop?
Will adjusting the cam gears affect the afr?
I know i will need to adjust the dizzy if i advance/retard the intake cam gear to set it back to 16.
Now, advancing the intake cam and retarding the exhaust cam will creat MORE overlap correct? And more overlap is desirable on N/A engines, right?
But doesn't more overlap mean a lumpier idle? And more fuel consumption?
</TD></TR></TABLE>
yes, when you advance it although u've already tuned your fuel maps, you should start to lean out..and since we're talking about cam gears, i dunno about anyone on here but i've seen alot of big numbers come out of +1 on intake and -1 on exhust, and your goin to have to fool with it bro, cause it will effect your AFR, its goin to exhust how much you actually burn or how much fuel and air mixture happens..it means more fuel consumption, that lopey idle is base about the duration and lift of the cam, what cams are u running..nm i naswered my own question you might some wha tof a lump idle wiht stage 2's nothing like stage 3's tho..u'll be run.

 

so after i get a steady AFR and tune the ignition maps, should i go back and make sure the afr is flat or is it ok to leave it where the afr leans out (due to advanced ignition timing)?

 

do not leave it to lean out u gotta add fuel if the igition is making u burn more fuel add more to even out the AFR u gotta keep it flatten.

 

cool, thats what i figured. Thanks for all of your help.