Well I emailed tdi & got an answer back quickly from Sam who mapped the car.
In plain english the combination of mods I've chosen produce this small dip in performance at that particular rev range.
Sam noticed it but there's not much you can do about it.
Maybe a different cold air intake would help?
Anyway he says the car is perfectly mapped & after a little play about today I have to agree.
It really does fly of the mark & it's a massive diffence from what it was.
I've just got 3 niggles really
The bonet doesn't shut flush because of the rbc & you can't fit the plastic cover
The rbc make a hell of a noise at speed, I mean hurt ears loud...
Vtec crossover is extremely low so I'm wondering about mpg
Anyway here is Sams reply for all those tecnically minded.
I hope he doesn't mind me posting this
The first thing I’d like to absolutely assure you of is that despite what has been suggested on the forum your fuel delivery tables, ignition advance tables and intake cam angle tables have in fact all been set perfectly optimally. This is to say that fuel mixture is on target at all points, the ignition advance is on target at all points and moving the intake cam advance targets fore or aft at any point would result in a loss of output, the mapping work is not “bad”.
There is however a noticeable dip in your engines volumetric efficiency through the range of engine speeds where this “dip” can be seen in the graphed results, we noticed that during the course of a constant acceleration test when on the dyno we could hear a distinct change in the intake and exhaust notes precisely accompanying the dip in the engines output. At this point I really don’t want to bore you by slipping into a science lecture about the mathematics of acoustics in pipes, but suffice to say that intake and exhaust system harmonics together both play a very important role in the ability of our engine to generate the high levels of volumetric efficiency necessary for really good torque production, the fact is that it is possible for harmonic resonances to very much help airflow through an engine at one point in the rev counter but to then hurt airflow at another point.
It became obvious very early on in the tuning process of your car that with your specific hardware combination the engine was able to tolerate the VTEC cam profile at a very early point indeed, choosing to be a little conservative we eventually picked 3200rpm to engage VTEC which is still very much earlier than the far more typical 4500-5000rpm found on with an N/A setup. It’s a good bet that this exceptionally good “low end” performance owes itself to a strong “positive” harmonic being generated at these lower engine speeds, this is further born out when you look at the graph of another of our customers who has posted in your thread as when you study it you’ll see that from 3000-4000rpm your engine is able to generate significantly more torque than his. Unfortunately this gift of an early positive harmonic appears to come with some unwanted baggage in the form of this negative harmonic resonance which would seem to be present at engine speeds around 4500rpm, fortunately by 4750rpm the harmonic effect has dissipated and the engine returns to its very strong operation from that point right the way through to the 8400rpm rev limiter.
Intake and exhaust acoustic tuning on high output N/A engines is a weighty subject even amongst professional engineers and reading this email back I can imagine that this might be a tricky subject to get your head around at first encounter, so if you have more questions about it or you would prefer me to run through the subject with you in person I’m more than happy to do that.
I wouldn’t agree that we can lay the credit/blame for either positive or the negative harmonic effect on the RBC component alone, as in order to generate harmonic effects of this magnitude multiple components will all need to resonate together.
NHB 06 Prem ~ Mugen Airbox ~ Fujitsubo Legalis R ~ JDM Rear ARB ~ RBC ~ KPRO ~ Wavetrac!