Instrument Pannel Changes and preparing for hydrogen

[ToyotaBuba]

Since I'm posting some updates, thought I'd share what I found works on upgrading/changing out instrument gauges etc. If you're stuck with a corolla or prizm with just a speedometer, don't loose hope... Even some models with all power options seem to be lacking the tach which was the case with mine.

In some reading on various blogs/forums, it sounded like some were swapping out instrument clusters successfully, so I thought I'd try. I found a 99 corolla that had an instrument cluster with the tach and removed my speedometer from my old cluster and installed it into the cluster I got from the 99 corolla and everything turned out to be an exact swap and connectors on the back of the instrument pannels were the same. Just be gentle when removing the hardware that holds the speedometer onto the cluster housing as you don't want to damage the flex circuit. Oh, you do have to take apart the cluster housing to get to the speedometer, so do go easy with that too, as the plastic tabs etc. aren't very sturdy.

I found that it was good to check all bulbs to make sure ones that were burned out or dark, were replaced with good bulbs. All the different indicators seem to all work and function normally. The tach works fine, and the only thing amiss, was the digital display under the tach showed something like an '-E' which after much research, found out that display was outside temperature display, and without the outside sensor, get's an error reading.

It turns out that there's a connector with nothing attached in front of the radiator and behind the grill where a short plastic sensor about 1 1/2" long plugs into that connector which then sends temperature readings to the instrument cluster. Once I found that out, went to a junk yard and found a prizm/corolla with a tach and sure enough, there was the sensor plugged in. Got the sensor and plugged it into my car, and now I have outside temperature being listed on the replacement instrument cluster. All is now working and complete with the upgraded cluster. I think I spent about $15 for the instrument cluster with the tach, and a few bucks for the sensor. Having a tach makes working on an engine much easier as well as being able to get a feel for what rpms are giving you the best fuel economy etc.

Adding a scanguage that plugs into the OBDII connector just under the dash on the left, that fits nicely in the little vanity drawer in the dash on the left by the driver door without having to hard mount it or velcro it somewhere ON the dash works great and gives all kinds of additional real-time data about what's going on in the engine, shift points and rpm levels, and how that affects fuel economy. I originally was hoping there would be a nice fit putting the scanguage inside or along side of the instrument cluster, but no such luck. Having it to the left and kind of down and slightly behind the steering wheel makes a person have to lean over to see some of the readings, but if your car has the little vanity drawer that opens up, it's an almost exact fit and you can route the cable through the opening and then into the OBDII connector so that there are no cables hanging down which is nice.

The only thing at least the scanguage or maybe the OBDII system is lacking, is reporting the air/fuel ratio. The ECU has to be keeping track of that in some manner, so it sure would be nice if the OBDII system would also report that. I did find an external air/fuel ratio guage that I think hooks up to the before cat O2 sensor, but that's just one more thing to have to hang inside on the dash. A scanguage does show open or closed loop status, and was helpful in finding out that the pre-cat O2 sensor was bad. No engine codes were being reported, but the O2 sensor was very slow to cycle etc. From what I've read, the pre-cat O2 sensor is supposed to have about a 1 second cycle back n forth on it's waveform, and open/closed loop status of the ECU should change very quickly i.e. in the milliseconds, not take seconds to switch from open to closed loop.

The next step, now that I have a tach and realtime monitoring, is to look into adding hydrogen... I may have made a mistake on planning to do the hydrogen on a post 1995 vehicle (wanted the OBDII data), as the pre OBDII cars had less computer controls and are supposed to be easier to fool/program the ECU when modifying the air/fuel mixture, and of course going back to non ECU cars with carbs and no ECU would probably be much easier. Was hoping to do some serious volume with hydrogen systems, but not sure I can be successful in over-riding the ECU and the air/fuel mix to where substantial mileage gains are able to be realized by trying to add substantial hydrogen volume.

Hope this feedback on upgrading the instrument cluster helps others out. If anyone has had any experience on adding hydrogen on these 8th gen engines, do let me know.

Thanks!

[fishexpo101]

Not with hydrogen - but previous experience with propane enrichment systems on diesels and gasoline cars. Regardless of what enrichment gas you add, this will be a non-trivial system to setup - depending on how you are going to source and store the enrichment source on-board.

In any case, the only way to really fool the computer and be able to tailor your air/fuel and ignition timing maps is with a standalone or piggyback EMS system. As they are named - a standalone system will replace almost all the base functionally of the OEM EMS system, the piggyback system works in conjunction with the OEM system by intercepting signals and fooling the OEM system. Only drawback with the piggyback setups, are the built-in failsafe parameters in the OEM ECM - some cases, the OEM ECM will automatically drop to a failsafe run mode or "limp" home mode if they get vastly different readings than way they expect (ex. you intercept the injector duration, but not the O2 sensor - computer sees a condition that should not be possible, defaults to a failsafe operation). Much if this issue is dependent on how the piggyback is setup and how much it is able to control. Some of the more advanced piggyback systems are more like standalone setups. Generally can tell by the costs - most piggybacks start out in the couple hundreds to several hundreds of dollars. Standalone system will easily be in the thousands of dollars.