Strange Flat Spot Between 4000 And 6000 Rpm

[wallas]

Hey chaps. Im trying to narrow this problem down, let see if you have any more ideas. Basically under full throttle the car will pull like normal up to about 4000 rpm then continue smoothly but slowly and with a lot less power up to about 6000 rpm then kick in like normal again after that. Its relatively standard with a fmic, exhaust and pod, but it did the same thing slightly more noticeably when it was standard. New spark plugs didnt help. I believe its an air flow related issue maybe the a/f meter giving false readings forcing it to r&r? Not completely sure on the r&r situation as theres so much conflicting info about it. Also as u can imagine its alot more noticable in higher gears. Let me know your thoughts, cheers.

[SECURITY]

thats r&r, time for a new ECU or turn the boost right down.

[MESSED]

ive heard that if you regap the plugs it should fix the problem if you already havent tried that, if not it sounds like you may need a new ecu good excuse to upgrade

[simpletool]

It's the standard ignition curves. The ECU has load maps (actually airflow maps which relate to boost pressure) that go past the stock boost pressure to about 12psi. At stock boost pressure running up the revs (down the rev table) the ignition numbers are roughly :

4000 20

4400 21

4800 21

5200 21

5600 22

6000 22

6400 23

At the highest boost (airflow) ~ 10psi point the maps look more like this:

4000 14

4400 6

4800 4

5200 4

5600 8

6000 14

6400 14

so as you move towards this over-boosted load section of the ECU maps then you get massive drops in ignition timing - hence the slow response. It's called R&R and it's most noticeable around the 4 - 6k revs - it does pick up a lot after 6k. Totally normal for boosted R33, get an aftermarket ECU, SAFC or remap.

Edited May 25, 2009 by simpletool

[wallas]

Champions... ill take it all on board. One thing though its not boosted. I thought It could be a boost soleniod problem so i rigged up a manual controller but it did the same thing and i hadnt even started to play with the boost. Do you still believe its r&r? (Boost gauge in back seat not yet wired up so not sure of actual boost im running but it doesnt go like my mates boosted skyline with almost the same mods.

[wallas]

One other thing, who does remaps? Does anyone know of anyone selling one of those blitz, mines or tomei ECU's? Preferably tomei, I believe they still incorporate a rev limiter.

[NisGTR]

hey peeps i have the same problem on my r32 gtr for about a month now and my Apexi PFC is new, does this mean the ECU is faulty?

[paulr33]

hey peeps i have the same problem on my r32 gtr for about a month now and my Apexi PFC is new, does this mean the ECU is faulty?

no it does not, it means get your tune checked

the PFC is completely different to the stock ECU

[mad082]

i love how everyone's first thought is rich and retard even though he says it was worse when the car was standard. when i experienced rich and retard when i first put on my boost controller and it was set to 14psi, it wasn't like a slight flatspot. it was like the key had been turned off then back on. it was a violent cut of power.

there is usually a bit of a flat spot around 4500rpm when the vct switches off. i used to notice it most in 3rd gear or in second gear going up a steep hill, with both a remapped ecu and stock ecu

[ClutchBurndout-:(]

i also have a similar problem, mines straight to the actuator and is around 8psi, but at around the 5k mark the psi boosts way over 8psi to more like 14psi, can this be fixed with a slight clamping of the boost hose from the intercooler or the one to the actuator?

[paulr33]

again check the tune (he said he has a PFC?)

ive never seen or heard of flat spots on a programmable ECU

[simpletool]

I stick to my ignition curve data - which is not exactly as it appears on the map but easier to understand. It does not explain why it is doing it stock. Cam timing does play a role here. My car even with timing taken 2 degree out (less timing) around VCT change-over gets a kick at ~4800rpm and above. Might just feel flat at it builds boost until 3500rpm, then flat, then cams give it a kick at top end. Normal RB25 behavior see website HKS GTRS maps.

[mad082]

i also have a similar problem, mines straight to the actuator and is around 8psi, but at around the 5k mark the psi boosts way over 8psi to more like 14psi, can this be fixed with a slight clamping of the boost hose from the intercooler or the one to the actuator?

does it stay high until redline or is it just a spike? if it stays there then i'd say you have an issue with your dump pipe or the wastegate flap. something is going on where it isn't able to flow enough air through the wastegate so it is going through the turbine wheel and creating the extra boost.

there is a small chance it could be something kinking/squashing the wastegate line though.

also i had issues with spiking just after i put my fmic on and i had the wastegate hose running from the bov line. i was getting issues where it was spiking to 14psi (was running 10 at the time) for a second when applying the accelerator after changing gears. and it wasn't holding boost that well at high rpm. i ended up cutting the boost nipple off the old intercooler piping and welding it into the pipe from the turbo to the cooler and never had an issue after that.

[RB JET]

I had the same problem in my series 1 r33. I tried everything you could possibly think of that could contribute to the problem with no success. So i purchased Power FC with Handcontroller and got that tuned and my car runs like a dream now. Thats how I fixed it, mine was r&r, but could be different for yourself, but the symtoms sound pretty much identical to what i had. Retune will definately fix it up for you.

[wallas]

trying an ecu, lets see how we go...