cjb80

Last night I took my car in for some dyno runs at a local performance shop. My best run was during the air/fuel test which yielded 204 hp in 4th gear. Other runs were peaked around 197 and 195 in fourth, and around 175 in third. The air/fuel test showed that the car was running "extremely rich", and they firmly believe that the engine is capable of at least 20 more hp with fuel tuning.

They are a distributor for a part called the Uni Chip which is made in South Africa. I did a little research on the product and it looks good. Basically the concept is that it's a chip that takes the stock fuel mapping and adds or removes fuel depending on RPM and throttle position. There are 5 wires that tap in to the ECU wiring harness, then there is a cable which connects to the tuning part of it. He says that it takes about 20 runs on the dyno to get it tuned correctly..

Anyways, the air fueld test showed that my car was running approx 11.6:1 and he mentioned that 13.5:1 is about optimal power.

Anyone have any comments or thoughts about this product? The web page is located at ...

http://www.dastek.co.za/

S2kRob

The Scooby WRX guys have used it to very good effect - particularly in Britain.

marcucci

I don't know anything about this product, and the website wasn't exactly informative, but it sounds like a V-AFC with fewer features. I'd recommend the Apex'i V-AFC without even seeing this one. The AFC is a great product with extreme adjustability, and it's well-known by tuners around the country. I'm not sure I'd trust a product coming out of South Africa, especially one unproven.

cjb80

Well There are a couple things that I think are good with the Unichip, one of them is that you can tune fuel based on throttle positon.. Is this possible on the VAFC???

Also, there is a data connection to the dyno which allows for exact tuing as opposed to someone pushing buttons on the VAFC..

Anyone else have any thoughts???

Penforhire

Why the low HP rating in third gear? All the Dyno runs I've seen posted so far, and mine, were done strictly in 3rd gear.

cjb80

I am not sure exactly why, he said that usually he dynos 6 speeds in 4th gear, and he expected 3rd gear to produce less power.. it's not actually making less power, but rather showing up different because of gear ratios??

ultimate lurker

I recently had my first experience tuning a car with the VAFC. I was impressed. Some of the features that I used were:

1. Variable VTEC crossover - you can vary activation point in both directions. IOW, you can create a hysteresis in the activation parameters. For example, VTEC can activate at 5000 rpm on the way up, but when decelerating not shut off till 4800 rpm. This is particularly helpful on road courses where you may drop just a touch below VTEC in a corner, but don't want the switch to occur.

2. Unmatched VTEC fuel correction - When you change the VTEC point, the ECU will still be expecting the change to occur at the normal rpm. That means it will alter fuel for the expected change. Thus, you need to alter the fueling to compensate. The VAFC knows where the stock VTEC point is and where you've set it, and allows you to enter a fuel correction factor (determined by tuning).

3. Hi/Lo throttle fuel correction. The VAFC allows you to set up a part throttle and full throttle correction map. This is particularly useful with the full throttle stuff since the ECU won't "learn" to circumvent your mods there. You can also control the throttle position (in percentage of full throttle) where the Lo and Hi modes work. In between those percentages (lets say you chose 50% for low throttle and 80% for hi) it will interpolate between the two maps you chose.

The VAFC also allows you to watch a variety of sensor outputs (TPS, manifold pressure, rpm, etc.) and even datalog them, which is cool. For $300 street price, its a decent alternative until we can get a fully programmable ECU.

UL

marcucci

... and to add to UL's remarks, the V-AFC specifically allows for hi/lo cam (VTEC and non-VTEC) maps AND wide/narrow throttle input maps. 4 distinct maps, though they are focused at the 4 ends of the RPM band (with some overlap). Neither the Field AFC or any othe AFC I've seen do that.

for some basic info on the Apex'i unit:

http://www.ntpog.org/mods/fifth-afc/afc.shtml

and some more detailed info:

http://www.members.aol.com/ryoucold/prelud...apexi/apexi.htm

Luder94

So what are the effects of a VAFC run in conjunction with a Mugen ECU?

In fact, is Mugen ECU's function negated with the VAFC?

tze

Unichip is more powerful than VAFC

If my reading is correct, VAFC has hi/lo maps. Hence at any variation other than full throttle it will be runing a lo map.

The unichip allows programming of timing and fuel based on throttle positions. Hence quite a few more than VAFC.

In Australia, it is distributed by aps. http://www.airpowersystems.com.au/unichip/unichip.htm

The problem that s2k owners face is that the vafc/unichip operate by modifying the exisitng fuel/timing map.

For example say at 5000rpm the stock map says 20units of fuel and 15deg timing.

You modify via chip, -10% fuel, and +2 deg timing. Hence 18units fuel and 17deg timing.

But since the bloody s2k will change its stock map and retard timing where there is heat/pressure changes - the fuel and timing will readjust itself again.

you can disable them ala mugen, however, the question really is whether you are damaging the engine everytime you go out in really hot weather etc.