Was having a slow puncture repaired on my S yesterday afternoon and went to a place locally who quoted a good price to my previously on SO2's but who weren't as cheap as Bracknell.

I pulled up and noticed next door that there was a shed load of TVR's parked in the car park. Left my car in with the tyre place and had a wonder over. In turns out that it was a tuning place and I went in and started talking to the owner.

Mentioned that they mainly tuned TVR's but could tune an S with a Unichip map and I wondered if anyone had any experience with Unichips.

Said that it was

 

I`m unconvinced. A lot of re-mapping work is discussed on the other forums and it seems its not just a swap of a chip and mode some air/fuel intakes - its a whole component swap alongside to get sig usable gains.

 

If they can really get *another* 20 bhp out of this engine, I'd be very surprised. Generally, N/A cars will give a far more modest return that SC or TC cars, which can get pretty massive power increases from a simple chip. (A friend's Leon 1.8T went from around 200bhp to 245bhp with just a chip)

I suspect that if they did improved absolute top power, it will be at the expense of flexibility/low rev performance, which will make the car harder to drive on a day to day basis.

If they want to try it on mine for free though...

 

From the way the chap explained it to me is that the Unichip is a piggy back ecu as opposed to a new chip.

He went on to explain that you are never going to get the sort of gains that you would out of a turbo or turbo diesel. I used to own a Leon Cupra R before the S and after a remap, the R was up from 210 bhp / 199 ft/lb to 280 bhp / 286 ft/lb and I always knew that I would never get anything remotely similar out of the S due to it being NA.

The way he explaind it is that where they get the gains from are through the mid and low range. Said that most NA engines were usually quite well tuned on full throtlle and that gains were easily possible from any other throttle position ie 6/10ths or 8/10th's throttle which is where they tend to do the majority of the tuning. He mentioned that they can very slightly improve on full throttle performance but not by a lot.

Cue a techie like Brian Marshall or anyone who has had this done.

As it is a piggy back ecu, it makes you wonder if it is possible to get the same gains out of the Apexi VAFC

 

It's been a long day, so I can't be bothered to do a long post. While there have been a few Unichipped S2000's (In Aus, and perhaps elsewhere), I'd recommend not having one fitted on the S2000.

-Brian.

 

Cheers Brian,

VAFC any good instead and what sort of power gains could you expect ?

 

It's a new day, I've had some coffee, so here's a longer post.

The Unichip is a piggy back - and advanced one. It allows for changing fueling, ignition timing, vtec point. They can also be setup to control boost in forced induction cars, and nitrous if you're going FATF.

The base Unichip uses modules to add capabilites. For example, there's a vtec module you'd need that allows it to control the vtec solenoid which adds a bit more cost.

Unichip's are installed only by Unichip vendors, who are the only people who have the software to set it up - they don't allow end users access. Generally, they splice into the loom rather than using a harness. But you'd have to check with the specific installer.

For fueling changes Unichips can alter the map sensor signal seen by the ECU, or they can take more direct control allowing for different injectors (only really an issue for forced induction.).

For ignition timing, again it's getting the right module. The F20C in the S2000 runs coil on plug - it's easier to blow the coils if you get the setup wrong. If they've experience with coil on plug, then there's more chance of them getting it right. If you do go for a Unichip, make sure they agree in writing to pay for any damage like blown coils - I'd imagine they'll have a big disclaimer along the lines of "every effort is made to tune safely, however your engine may blow up anyway".


V-AFC is another piggy back. It works be altering the map sensor signal the ECU sees, to adjust the fueling. (Note, only really good for leaning out, not adding fuel). You can get pre-made harnesses that fit between the ECU, and the wiring loom allowing you to install the V-AFC without cutting. Makes it removal should you want/need to. You can make harnesses for other piggybacks like the Unichip or Greddy E-Manage, but they're not so much an off the shelf item. Note that there are two versions of the V-AFC. The newer V-AFC2 has finer adjustment points - IIRC every 200rpm instead of 500rpm. That's a small advantage - so if you're buying new it may be worth going for the newer version. The older V-AFC's turn up second-hand quite a bit, so could end up cheaper.


Now to understand where the gains can come from, and what the pitfalls are, you have to understand a little about how the standard ECU works.

For ignition timing, the ECU has a map so it can lookup the rpm, and the load and gets a figure back. This is the figure used, asside for two corrections. One for temperature, if the coolant, or air intake temperatures get too hot the ECU starts to retard ignition. And if it senses knock, it retards. When the ignition is retarded because of knock, the ECU gradually tries to increase the timing back to the value that's in the map. It does not advance past the value in the map. There is no learning, only corrections to protect the engine.

For fueling, things are a bit more complicated. The ECU runs in two modes, closed loop and open loop. Closed loop is used during part throttle (Map sensor values also affect it a little, but treating it as throttle only is enough for this discussion.).

When running closed loop, the ECU watches the reading on the O2 sensor. This is a narrowband, so can't give an accurate value outside of stoich (~14.7:1 AFR), but what it can do is say if the car is leaner, or richer than stoich. Stoich is the value where the cat works, giving best emissions and good economy. So using the O2 sensor readings, the ECU constantly tweaks the fueling try try keep it at stoich. Since the sensor is only saying 'too rich' or 'too lean', the actual air/fuel ratio constantly bounces around stoich. Now the ECU has two fuel trims - short term and long term. Any corrections the ECU is making to try keep stoich are fed into the short term correction. (Both corrections are +/-20% in range.). Then, the short term correction is fed into the long term correction. So for example, if you've been running +5% short term, it gradually increases the long term correction. This is the learning that goes on. Fueling is also corrected for coolant temperature (both for speeding up warm-up and for cooling the engine if the temps gets too hot.).

Open loop is a little different. When you get past a set point (quite low, and variable with map, so I won't quote a figure), the ECU goes open loop. In open loop, the ECU ignores the O2 sensor readings. Remember how the O2 sensor could only tell if you were richer or leaner than stoich? Well, for power (and in open loop you've some throttle on so you want power), you want to run richer than stoich - somewhere in the 12.5:1 to 13.5:1 range on most engines. So the O2's information is no help. (A wideband O2 can be used to run closed loop at full throttle, but that's more something for the likes of a MoTeC ECU...). Instead, the ECU simply looks up in a table (called a 'map' hence, 'mapping' an ECU). The table lists rpm vrs load (which is calculated from the throttle position and the map sensor reading.). The ECU interpolates a valve from the nearest entries in the map to get a base value for fueling. Then it applies the long term fuel correction to this - only the long term, the short term fule trim is ignored when running open loop. This gives it the value to use. So, it applies the correction it's learnt from closed loop when running open loop, but doesn't learn while running open loop. (Slight aside, this is why when the map sensor is playing up and needs tapping, that you get crap running around 7,000rpm or higher. With a dodgy reading from the map sensor, the ECU ends up in the wrong place in the map, giving the wrong fueling/ignition.)

With the standard ECU, both fueling and ignition are set conservatively. The biggest example of this is between peak power (~8300rpm), and the redline (~8900rpm). Here the standard ECU runs very rich (around 10.5:1, to 11:1 - remember the range 12.5:1 to 13.5:1 is where you want to be for safe power.). The ignition timing is also backed off. There are gains to be had in most of the rev range, below and above vtec, but the most dramatic are post peak power.

For fueling, both the Unichip and V-AFC can leans this out a bit, to give gains. The problem comes from closed loop and learning. Say you lean out the fueling a little. The ECU then sees this when running closed loop, and uses the short term to correct for your changes, and get back to stoich on closed loop. These changes to the short term fuel trim, feed into the long term fuel trim then undo the change's you've done for open loop. Not what you want. you can't just increase the change either - if the ECU hits the 20% correction limit, you get a check engine light and it goes into a 'get you home' mode. Definately not what you want. However, remember that the ECU doesn't learn at open loop, it only applies the long term fuel correction. So, if you only make changes that affect the fueling when running open loop the ECU doesn't 'see' the changes, so can't learn it's way round them. So, you can make gains for open loop without problems. You can't tweak the closed loop (which can help with pickup and drivability) as the ECU will correct them out and mess up your open loop settings.

Now, a Unichip can potentially adjust the ignition timing which allows for a greater gain than fuel tuning only. So that's a plus if it's set right. However, recall that due to the learning, it's only practical to make fueling changes for open loop running. Now you can (AFAIK - I've never setup a Unichip), make ignition timing changes at both closed and open loop. Open loop, you can set both fueling and timing so get the best gains. Closed loop, you can only tweak the ignition, so you're more limited. And the transition between open and closed loop makes a difference in drivability, so you're limited how much you can improve that.

With Unichips, they're normally sold as a package with install/setup included - around

 

possibly the longest post ever

 

If Brian didn't exist, we'd have to invent him!

Lord knows how long it took him to type all that. It's nice to know that there's at least one person on the UK board who knows what they're talking about, rather than just regurgitating something they might have read elsewhere or heard from someone previously........!

 

I am trying to think of a way of avoiding like I am taking the pi55.........but Brian rocks!!!!!!!!!!!

That gear shift ringing advice really helped me....most probs Honda would have taken the friggin gearbox out or something

question.........When is Brian going to publish a book?