What range does VTC kick in?

[justified2.4]

I am doing some brainstorming, trying to see what may be causing my hesitation at 4k-4500 RPM, thinking maybe VTC is part of the problem.

When exactly does it kick in on the RB25det Series I?

Cheers.

Justin

[Jay95R33]

It's a bit wierd really.

I think it's something like on at idle, then turns off at around 1100rpm, then turns back on at 4500rpm. Maybe to give better emisions at idle?? I have no idea....

That flat spot is well known, and it's the stock ECU pulling timing for some reason.

J

[justified2.4]

My other hypothesis was that it is the ECU pulling timing, but I need to verify that to know what to start replacing or rewiring.

[Steve]

http://www.tomei-p.co.jp/_2003web-catalogu...haft-specs.html 4500rpm is where the NVCS turns off.

How is your fuel? 4-5k is peak torque. I had troubles with mine, as AFM had reached max voltage, and I was using stock fuel pump which just wasnt up to the task.

this was with only FMIC and Power FC running 12psi on stock turbo.

Good luck

[Steve]

Oh, and the AFM hit full (5.1V) at 4500rpm:)

[justified2.4]

here you can see where my power drops near 4k

Help!

[Steve]

What sort of management are you running? What were your AF ratios? have you tried disconnecting the VCT, or NVCS as nissan call it? Plugs? Also, what boost are you running? if its over 12psi, you will hit fuel cut.

What mods have you done?

[R31Nismoid]

that's way worse than it should be.

it should drop down around 4-4.5 and then pick right up till 7000rpm.

It's the ECU. Your correct. I think it fuels up a bit/timing and thats the falt spot.

All R33's i've seen have it.

I'll check the graph on a mates R33 with a PFC... might confirm?

[justified2.4]

What sort of management are you running?  What were your AF ratios?  have you tried disconnecting the VCT, or NVCS as nissan call it?  Plugs?  Also, what boost are you running?  if its over 12psi, you will hit fuel cut.

What mods have you done?

Just running stock automatic ECU with S-AFC, waiting for the shop to email me the A/F ratios, they said they were fairly steady, but need to see them for myself. I was only running around 9 psi. I am going to try disconnecting NVCS, although I think maybe it is not working at all sometimes and that could be the problem. Plugs are Autolite, gapped down low where everyone recommends for SR and RB.

[Steve]

Another one, have you cleaned the AFM?

Have you tried doing a reset on the ECU lately? If you have detonation it will retard the hell out of the timing and start to run like a dog. Perhaps it detected trouble when the SAFC was being tuned, compensated and needs to be reset (disconnect battery) then take it out for a flog so it can retune. I used to do this regularly when I was running stock ECU or it would loose power up top (but not nearly as bad as your dyno is indicating)

Sorry if it sounds like I am guessing, but I am:) gotta try all the common problems.

[dajorad]

Justin,

looking at your dyno curve, the problem starts at 3500 RPM, not 4500 where the VCT kicks in. In fact the power starts increasing again at 4500.

Have you checked AFM voltage and injector duty cycle.

You may have hit a limit of one of these.

[Guilt-Toy]

the problem is the standard computer retarding the timing

[justified2.4]

the problem is the standard computer retarding the timing

I am still having the problem, I am using Techtom to monitor and it shows that timing is not being pulled. It is almost as if there is no spark where it cuts out.

And it is not leaning out either. Checked spark plugs and gapping and they are fine. Not sure where else to look.