here is my hardware:

4B11 2.0 built engine, with cosworth piston, conrods, bearings, etc.
full-race exhaust manifold
FP Green turbo with stock position
Tomei expreme Ti exhaust
walbro 255 pump
AMS fuel pressure regulator kit (acutally fuellab)
Injector dynamics 1000cc
and Kelford 272 cam, with cosworth springs and titanium retainer

The problem is, at around 2000rpm, when I push a little bit on the throttle (around or slightly higher than 100% load), the car/engine just starts to shake and won't rev up. if i push it just a little deeper, there are then some bursts of gas going out of the exhaust. It just sounds like the air on the exhaust side of the engine is going way messed up.

If i let it slowly go through to 2200rpm (with just little throttle), it then all goes good.

The problem gets more severe with higher gear, i.e. if i use the same amount of throttle, it can rev through on the 1st gear no problem, but a bit shaky but will eventually pass on the 2nd, but won't go through that 2000rpm rev at all on the 3rd.

I tried around with many many types mivec, and it doesn't seem to be affecting the problem much, even by zero out all in/ex mivec maps.

Also tried leaning the fuel at this range, and it doesn't seems to be helpful much at all.

This is driving me crazy now, since the car is still supposed for day to day street use, but a problem at a 2000rpm range makes this impossible or a very big PITA.



okey ... maybe it's not a perfect title, but i doubt that the problem is most likely coming from the cam, since i tuned several other evo x with similar setting but just lower degree cams, and doesn't have this problem at all.


Please please help ...

 

Sounds like an exhaust leak to me

 

Let me elaborate I had a similar issue with my evo x check your plugs just to be sure but I had an leak before my turbo on my mani...

 

thanks for the idea!

it's a brand new mani, and i replaced the older one partly because i wanna see whether it's caused by the mani or some leak. the previous one also had a same problem ...

 

and who did the Tune?
Cause its the tune...

 

i did it myself ...

can you please be more specific?

 

needs more fuel or timing. whats the cam phasing in that area?

 

Interesting thread subscribed.

 

tried leaning or riching the fuel, none seemed to work...

timing idea makes sense, would try that ...


not sure about the phasing

thanks for the ideas

 

Sounds like too much cam timing overlap. The kelfords need alot less MIVEC timing in the low load areas.

I would drop both MIVEC advance and retard and make sure there isn't too much overlap. You should notice the rev range cleaning up as you do it...