3.2 Wot

[BlueMax]

Can anyone tell me why I don't seem to see WOT fuel enrichment? See following:

1. Tested throttle switch - ok, signal changes at approx. 70% throttle.

2. Mechanically checked linkage, I do have full throttle.

3. Wired a Fuel ratio meter into oxygen sensor. DEM seems to hold A/F ratio very steadely at 1.0 lambda.

4. Full throttle, A/F does not go full rich, for that matter it does not seem to change much towards rich.

5. Interestingly. on throttle overrun, Fuel Ratio meter indiactes a full rich condition ??? What gives?

6. For testing purposes, loosened tension on air flapper (AFM). Result. car does accelerate "seat-of-the-pants " more strongly, but as above no change indicated on Fuel Ratio Meter.

Car has a no-name chip, euro-premuffler, all else is stock. Could the DEM be fried or the chip? Any other tests I can run.

I'm confident the Pelican community has some help. Thx in advance Pelicans.

Paul

[Steve W]

There could be a few of reasons why you don't see the enrichment you are looking for. First, use a meter to make sure the box sees the wot switch signal on full close. Second reason could be the no name chip. Chips could be mapped any variety of ways, and who knows how yours is programmed without making a dump of the eprom. The other reason could possibly be the way your air fuel ratio meter is tapped into the O2 sensor circuit. If the impedance of the meter is not high enough to isolate itself from the Motronic input, the box could go into limp home mode and any variety of things could happen. Best way is to use measure O2 sensor voltage with a quality DVM such as a Fluke or disconnect the O2 sensor from the plug while reading the output voltage.

The Porsche chip has a specific 1x20 array for full throttle fuel and ignition. When the full throttle switch is activated, the O2 sensor and flapper door outputs are ignored and these fixed maps are accessed. Different aftermarket performance chips increase the hexadecimal values here anywhere from 1 to 8%, depending on the manufacturer. If loosening the flapper door increased your power, it is possible that your chip may not be programmed aggressively enough for your car. Loosening your door has no effect on wot fuel delivery, and only affects part throttle conditions.

Using a wideband O2 exhaust analyzer on my car, I measured and programmed a chip to deliver a 12:2 to 12:6 afr at wot, 14.7:1 at steady state mid throttle, and as lean as 16-17:1 on light steady throttle. When the throttle is closed and the engine is decelerating from high rpm, fuel is practically shut off, until the rpms drop below 3000, at which point, only enough fuel is injected to keep the motor at/just above idle. Quick throttle jabs indicate afrs dropping to as low at 11:1 for a momentary half second, a bit too rich, but that is an inherent flaw of the flapper door meter design, which tends to overswing under such conditions. Hope that'll help with your diagnosis.

[BlueMax]

Steve,

Thx for the informative reply. A firend of mine build the A/F monitor according to a thread at nriedel@nextek.net. Impdance matching may be the problem. We will try to measure again with a quality meter like a Fluke. The chip may be at fault. Care to do a dump on it if I mail it to you. Also, how much would you charge to burn a more aggressive one?

Thanks again

Paul

[Steve W]

Not a problem at all - just mail me the chip. I'll do a dump on it, analyze and email you the maps, and return the chip to you. If you would like a different or more aggressive chip mapped out and burned for you, that's also not problem. Contact me off list at stevekw@pacbell.net