.Boston.

Just sharing my thoughts and experience.
I know gernby isn't active on here anymore. But I'm sure there are cars with his tune running around.

After owning my 06 for about half a year, I felt like the powerband was off. It felt great down low but you could tell something was fishy in the midrange.

I had the gernby etune on my 06. I purchased the car with the tune already flashed on the ecu via hondata.

IMO gernby capitalized on owners butt dynos.. Reviewing his tune on the dyno we found out what was actually going on with the power curve.
Since his vtec engagement was set to 3,600rpm, you feel the torque come on low and ramps up.
The drop in power after vtec was massive. So after this tq/pw loss, feeling the curve up makes it artificially feel faster..

We spent 20 mins on the dyno and smoothed out the curve. Made power everywhere.. I think we ended up making +11whp up top and 15-20tq mid range, mostly by increasing the vtec engagement point..
The 3,600rpm vtec was causing A LOT of loss in the mid range. It was clearly too low.

Do yourself a favor and take your 06+ car to a proper tuner.

Car Analogy

I am legitimately interested in this topic, bc I also have a Gernby tuned '06. Berk hfc is my only real mod.

But not sure I followed the post. What I think I read:

With a Gernby tune you legitimately feel the torque come on with his low vtec rpm. You feel it ramp up from there. But its not really ramping up from when you first felt it, its actually a massive drop.

Not sure how to reconcile that, as it sounds contradictory. Plz elaborate.

Also, if raising vtec rpm to 3,900 was the main contributor to the dyno fix, wouldn't that be right around where the Gernby had a massive drop? How does this tune manage to start making gains right around where Gernby had its big fault?

I know that a huge part of the Gernby research (which was significant and impressive) was discovery of the impact of exhaust resonance on vtec range.

For example, on stock cat, lowering vtec produced exactly the sort of massive drop you describe. His findings were that a hfc or tp were requirements to successfully lower vtec rpm.

Not bc of flow, but bc of change in resonance occurring within exhaust system.

I also understood Gernby didn't universally lower vtec rpm to the same amount in each tune. Each one was customized to what worked best with that car. Its engine, its exhaust, its cat. How these all combined to create that cars unique resonance pattern, and how tune could best optimize for that environment.

That would mean that changing anything in exhaust system post tune could have significant impact on effectiveness of his tune.

Changing from tp to hfc, hfc to tp, hfc to different brand hfc, changing catback, changing diameter of anything within exhaust (tp to different diameter tp). Maybe even hfc becoming slightly clogged over time could be enough.

Any of those things would require retweaking his original tune.

I'd love to hear from others that can provide additional facts (not just butt dyno feel, which is all I personally have). People who got a Gernby road tune, then later had car on dyno. Like maybe a cheap dyno day, or someone that later decided to go fi, and had their Gernby tune dyno'd as a baseline before making any of their mods.

What does dyno graph show? Is there a dip, or is there a steady climb once Gernby vtec rpm engaged?

Is OP an outlier experience, due to environmental or other factors (an isolated bad job by Gernby), or evidence of Gernby fraudulence (intentional or otherwise)?

We need more dyno graphs to get to bottom of this!

Slowcrash_101

I personally would NEVER put VTEC that low. It's too close to BMEP which means you are raising the probability of knock or detonation. There's a reason Honda put VTEC at 6k rpm.

.Boston.

l also have an HFC. I wish i saved the graph from dyno when we tested the tune.. Yes there are multiple variables but this was how the previous owner had it tuned by gernby. I did not add or remove anything that would have affected performance.
Stock there is a dip after vtec but comparing it to my gernby tune the dip is much larger. It felt faster because the point where it starts to climb is much lower.

I'm interested in others dyno graphs.

Also, how does you cars powerband feel? Where does vtec engage?
Best way to describe my experience is -
1) strong initial torque around 3,600-3,800
2) slightly flat around 3,900-4,300 (dead spot)
3) power feels strong again 4,400+

Don't take those numbers as exact. That's going off of memory.

Smoothing out the vtec crossover showed us gains everywhere.

Car Analogy

My Gernby tune vtec engages just under 4k. At around 3,800 I think.

There is a constant, pull from that point on. It feels like a larger, but more traditional redline engine. Like its gonna have a 6k rpm rev limit or something.

Meaning at that point it doesn't feel like this party could possibly last to 8,400 (my current rev limit). But it does. Just keeps going faster and faster.

So at vtec engagement, it feels like a torquey 3.0 that you assume is gonna run outta breath soon. But that never happens. There is no perceptible dip.

But butts lie. Dyno doesn't (well, at least the shape of graph doesn't lie, even if numbers often do).

That's why we need more data points.

Car Analogy

You have a point about 3.4k, but I don't think that point applies to 6k.

Gernby proved that even trying to lower vtec to 5.8k with stock cat causes a significant dip. It really feels like Honda choose 6k simply bc it was lowest rpm that worked for performance.

3.4k vtec probably is some concern regarding engine pressure. But knock is one of the core things Gernby tuned around. Carefully checking logs to make sure knock wasn't an issue.

A manufacturer has to worry about what fuel an owner might use, and how they might neglect maintenance. Gernby had the luxury of counting on his customers exclusively being enthusiasts that would always use high octane fuel from high quality sources, and perform maintenance like plugs on time or before using OE quality parts. He could push boundaries that Honda could not.

A good question would be what rpm would Honda have chosen if cat resonance didn't affect vtec performance? Probably lower. But surely not below 4k. Difficult to say where they'd have landed.

But again, Gernby had luxury Honda did not. So understandable he'd land lower than Honda. If he pushed his boundary too far, well we'd be seeing cars with his tunes having knock issues and the failures associated with that. So far (and its been a while), we haven't learned of evidence to support that concern - potentially its out there but hasn't been reported, or people linking knock issues to their Gernby tune hasn't happened. But we make conclusions on the evidence we do have.

Slowcrash_101

Personally for safety I would not lower VTEC below 4,800 rpm, you're well past max BMEP at that point, and shouldn't cause too many issues. Remember, higher piston speeds mean faster combustion, having too much valve lift at too low RPM affects the quality of combustion, there's not enough piston speed to turbulate the air fuel mixture. This is why at low RPM you're on the low cam, the venturi formed by the valves at max lift doesn't need to be big, so you get good combustion at low rpms.

Slowcrash_101

It's helpful to understand how valve area affects air velocity entering the combustion chamber. Low valve lifts act like putting your thumb on a garden hose, this is good at low rpm, when the volume/mass flow is low. High valve lift is like taking your thumb off the hose, this is fine once you have a lot of mass/volume flow, because then your thumb is actually choking the flow back.

Chuck S

I'll let y'all read and comment. This tune transformed the car. Highly recommend something like this.

Here's the Mustang dyno data for my 2006 Gernby tuned car. (Green line.) 2015 single pull. And a stock 2002 (2003?) AP1 car (red line) we tested at the same time. Both cars have the same intake, cat, and exhaust.

Berk high flow cat.
Tanabe Medalion Touring exhaust
K&N FIPK intake.
3600rpm VTEC on my car, 6000rpm on Ryder's.

No VTEC Yo! in the tuned car as the power just rolls on at 3600rpm. Exhaust sound makes a fairly dramatic increase at VTEC engagement. Been 9 years so I don't recall any Butt Dyno impressions but a couple other owners of AP2V2 cars have driven mine in the past few months back-to-back with their own cars and are impressed.

The AP1 car was supercharged shortly after these tests but I've not seen (or don't recall) the results.

(Sorry, I don't recall Ryder's user name right now or I'd tag him so he sees this and fill us in on his supercharger.)

-- Chuck

Car Analogy

Thx for posting!

Kinda blurry, can't really read any of it. Ok, so just look at graphs. That's all we need in this instance.

But there are 3 of each. HP, torque, and?

Also, not seeming to make sense.

Looking at what I assume is the two torque curves, would expect to see clear evidence of an early, large advantage for green, where vtec engages earlier (and you can feel the torque pulling). Then see where red finally starts to catch up, when its vtec engages. But from there expect green to stay slightly above red (larger displacement) but stay locked together as revs increase.

I don't see anything like that.

If these were both just untuned ap1 and untuned ap2, it would make a lot more sense.