Looking for opinions on how people are handling running big cams. I have JUN 272's in there now and idle is pretty bad. I'm messing around with MIVEC settings a little and idling them at 1100 RPM. Still not consistent. It is a blow through setup and vacuum jumps around quite a bit despite not finding any vacuum leaks. Anyone offer some advice on improving idle quality?

 

you have your stock MAF in blow-through, or using a GM maf? (hey that's a good idea, wiring in a gm maf, are they compatible?)

Try adjusting other things besides mivec, like timing and afr. A lot of evo8 guys switch to open-loop idle so they can run the car at, say, 13:1 to help smooth it out. 1100 isn't bad, but the jumping around is what sucks.

 

Minimize overlap in the MIVEC tables in the RPM range where you are idling if you haven't done so already. The main advantage of MIVEC is aiding in the spool up of the turbo. In my case on the stock Ralliart turbo and aggressive MIVEC mapping I was getting compressor surge from hell... so I have my MIVEC tables damn near zeroed out with good results on the Cosworth cams. I have no doubt if I had a larger turbo I would need much revamping of my MIVEC tables

Keith

 

Thanks Keith. Yes I tried dialing out some overlap but doesn't seem to make too much difference. I have added and take out advance on intake cam and added and taken out retard on exhaust cam with little improvement.

 

Try 13 deg at idle and -5 ext retard in the area where u iidle. So between 500 to 1500rpm and 10 to 40 load.

 

ext retard?

 

Yeah, exhaust retard the mivec cam...

 

Tried -5 and -10. NO go.

 

Did you install the cams correctly? Have to ask...

What is the issue? Rumbling? Or what? The RPMs are dipping up and down?

 

Did you add timing to the timing map as mentioned above (several times)? Again focus on the top left corner of your maps: from 0-1500 load, 0-40 load (maybe 50 or 60? log the car and see where you're hitting)

-intake mivec: 0
-exhaust mivec: -5 to 0, try a few
-timing bump it up to 13-15 (stock is 10)

 

Yeah, that's what I told him... dunno what he did. Maybe just the MIVEC...

 

What year is your car? Are you using Cobb or Tactrix to tune?

Edit: In fact all your mods would be nice to see. It may help figure out what is wrong.

 

I'm at around 40 load at idle trying to idle it at 1200 now. It is lower load site due to larger MAF housing (3 inch blow through). I did change to the timing map before I posted which is identical to suggestions. I have intake cam at 0 and playing around with exhaust cam to no avail. I checked for vacuum leaks today and nothing found. Vacuum hovers around 14 inches but idle is inconsistent and car just doesn't sound right (actually pretty terrible). I now suspect perhaps the chain jumped a tooth on the crank when we turned it over (to start). The reason I say this is at random times today I did get codes P0011 and P0014 which is intake and exhaust cam too advanced. Also the fuel map is quite wild and all over the place and am having difficulty smoothing everything out both in terms of fuel trims but also transition from light to heavy load. Oh and I am using ECUflash with Tactrix cable to tune and datalog with Evoscan mode 23.

 

Here is list of mods:

GT35R HTA with Tial Stainless housing (vband)
Peak Boost manifold
Tial 44mm wastegate
Custom downpipe, upper IC piping (2.75 in), and 4 inch intake
AGP lower IC pipe 3 in (with MAF plate welded on there)
4 inch Garrett core
3inch exhaust/test pipe
HKS SSQV 3 on upper pipe
DW 1300cc injectors
Agency Power Fuel Rail
Ported and Polished cylinder head fully cc'd and 5 angle valve job (stock valves)
JUN 272 cams and valve springs

 

Ditch the blow-through setup man, that may be causing you problems. First though, double check your timing.