This past Saturday I brought my car with installed VAFC (I mounted myself in radio door w/plug & play harness) to a DC area tuning shop (www.alteredatmosphere.com) for proper tuning. I have never done business with them before but I chose them because they had a strong reputation in the local import community. They work on some pretty high-horesepower Supras and have made their mark in the 3000GT/Stealth world.

Other than an Import-Development CAI scoop (and VAFC) - the car is bone stock on the engine side. I am by no means an expert in the ways of the VAFC but I can say that I have a reasonably strong knowledge of it based upon the following:

1) Reading each/every thread on this board with regard to the unit and its parameters/installation.
2) Reading the manual multiple times and speaking with folks within the community about what it can/can not do.
3) I understand that on any given day the same car will give different results on a dyno based upon the dyno's margin or error, atmospherics, and other unquantifiable inputs.
4) I understand enough about the VAFC to raise proper questions and to have a sense of if the tuner is giving me a line of BS or not.
5) I understand why the % mismatch setting is important and that dynoing the car doesn't accounting for performance in a solid state setting. IE: holding the car in 3rd or 4th at steady RPMs waiting to exit a corner.

In the DC area - the weather this past Saturday morning was about 69 - 71 with very low humidity - pretty good conditions.

Before getting started, I asked the tuners repeatedly (to the point of annoyance) if they had tuned S2000s with VAFCs. The answer was a resounding yes. My first baseline run had peak HP of around 185 and I was disappointed. Like many others, I was expecting/hoping to get in the 195 - 200. A red flag was immediately raised when the tuner said he thought it was great 'cause our cars "usually get in the 165 - 170 range"

The second run hit about 201 and I was getting happier. I asked him what his tuning methodology was and he said that the first thing they do is nail down the VTEC engagement point and dial in the air/fuel from there. Sounded reasonable to me. After a few more runs and some jiggling of the fuel curve (repeated runs), I began to notice that the VTEC Lo/Hi switchover was occuring about 5000. Now, this struck me as being kinda low for the F20c and I pointed that out to them. It was their belief that the quickest/easiest way to get better #'s out of the engine was to lower the VTEC point.

From this board - again, I know that all instances vary - the general trend of VAFC tuning that the L/H VTEC engagement point is rarely, if ever, below 5700/5800. In fact, there was some disagreement as to whether 5300 was even on the bounds of acceptability. At NO TIME, have I ever head of someone setting this below 5000.

When examing the dyno charts (which I will post soon), the reason why my car baselined low was because they let off the gas at 7400 - WAY below peak. When I told them their baseline was off they looked at me like a fool and shook their heads. "Oh you want us to run your car over 8000?!" The next run - where all they did was move the VTEC point to 4900 - yielded 201. Of course, I noticed that the engine was revved out to 8700. They attributed the 16 hp gain to the VTEC point change, not the fact that the car makes peak hp over 8000! I questioned them on that - more circular reasoning.

To make a long story short - I bit my lip for a while hoping for better results. I was very patient because I didn't want to get in their way. They said they raised the VTEC engagement point to 5300 to satisfy me and contined to dial in the fuel. I asked them what the VTEC Hi/Lo point was set at and the % mismatch. It was clear that they had no clue about these settings and I began to worry. As the fuel curve was improved, the peak HP rose to 211.9 with torque at about 138.9. While this was looking good on paper, their non-answers were beginning to annoy me and I began to lose my temper. I don't want people f%&ing with my car if I don't trust them, especially when manipulating fuel curves. I asked them to show me all their settings - when I went through it, I saw that the VTEC engagement point was still at 4900!! The Hi/Lo was at 4100!!! They "explained" that since the VAFC was a piggyback system, the true engagement point was actually higher. Huh? Again, to "make me happy", they set the L/H engagement point at 5500. But now the fuel was dialed in for 4900 so eveything had to be done all over again. To make a long story shorter, I had enough. I was certain that the little I knew was enough to know they were FOS. I paid my $165 and left might mad. I've decided not to go after them for the $. No harm was done to the car and my time is too valuable to puruse this. I've just decided not to ever do business with them and that is that.

Conclusions & Questions:
1) As soon as I got in the car I re-initialized the system and set it back to stock.
2) Am I out of my skull to think a sub-5000 VTEC engagement point is a bad thing?
3) Just as much attention should be paid the VTEC Hi/Lo and % mismatch, correct?
4) I will post the charts I have when I have more time.
5) My basic feeling is that most tuners have a basic knowledge of the VAFC to be dangerous enough to think they know how to tune our engines with it.

 

EJ,
I'm sorry to hear that your experience with AA turned out like this. I can't believe this is the end result after waiting so patiently (also parting with $165) to get your VAFC tuned by AA. I was hoping that you would post positive results of your car gaining 20+ HP after the tuning session but I guess AA wasn't up to the task. I hope you find a knowledgeable tuner to get this working for you.

 

I would demand a refund, they are incompetent!

1. S2000's usually get in the 195-205 range, stock.
2. You should run the car all the way to redline on the dyno! I think the numbers on the tach are optimistic. If it shows 9000RPM on the tach, the V-AFC will read 8800RPM or so. However, the AFC is showing the true reading because the input pin comes from spark timing pulses. The dyno is using an inductive pickup to measure RPM so it is also a true measurement. In other words, them explaining that "since the VAFC was a piggyback system, the true engagement point was actually higher" is BS!

Let's see the curves. With such a low VTEC engagement point, the high cam will be making significant less power, and you should see a big dip in torque.

 

AA did a great VAFC tuning on my car! Who did your tuning???

Mine is SC'd but shouldn't make a difference. My vtec low hi is at 5300 and hi low is 4800?? I think?

 

There were two guys who did it. Randy and Mike. I know there are multiple guys named Mike running around there. It was the one with the red '97 Supra. Randy is the one that reminds everyone of Kramer with lousy conversational skills with the monster Firebird As it was Saturday morning, there were not many people running around there. Regarding the S/C tune, they said for cars with S/C or Turbo (they just did CBender's on Thursday) they set the VTECH L/H higher than for the NA cars. So, your settings would jive with that theory when comparing the 4900 which they initially tuned my car.

What did they set your % correction and throttle positions at? Randy seems to be very good at understanding fuel maps. However, not in regard to VTEC engagement and the F20c. Also, Mike did not engender much confidence with his VAFC/F20c knowledge.

Anyone with a shred of a clue would know that the baseline of our cars is reasonably in the 190 - 200 range, not 165 - 170. Also, if we assume they had a clue, they would know that peak hp is made at approx 8300 and that by cutting the baseline off at 7400 gives you a "false" starting point for comparative purposes. I understand not wanting to overdo it, but claiming a 16 hp improvement on nothing but VTEC L/H point manipulation is bullshit.

BTW johev - you may want to go back and check your settings.

 

They ran mine up to 8700 or there abouts. Randy is pretty knowledgable about cars. I'm trying to think about my % would 15 and 55 seem right??? maybe that was throttle positioning or something

 

Changing the setting in the VAFC will alter the signal from the ECU to a different specific point. It's not adding or subtracting the stock signal. So the comment about it beign a piggy back and therefore the VTEC engagment is a bunch of crap. I have read that the optimal VTEC engagment for an NA car is 5600.

Also, they should run the car to 8900 as with a VAFC you can make power up to redline, it doesn't taper off like the stock fuel map.

You were right about the sub 5000 rpm VTEC engagment.

Chris

 

Let me know if you go to another tuner and what they say.

 

BTW - thank you all for your responses. I am working with some other folks in the DC/MD/VA to locate other tuners with VAFC experience on S2000s.

 

Cool, let me know....have Rick and others gone to AA yet/?