Last summer I lent my Impreza STi to my brother for a couple of days after he'd killed a wheel bearing in his van. Unfortunatly during the time he had it he managed to blow the engine, putting a hole through the side of the piston!
As a result, I had the engine completely rebuilt (at considerable expense). But when it came back it was boosting a lot higher than it should - to about 1.4 bar in fact when the normal boost level should be 1 bar for my model year.
So I thought I would have a look at what was happening and see if it was coping OK with the extra boost, or if something needed to be done, and to do this I chose a VEMS AFR and EGT gauge.
When the unit arrived it looked OK, but there were a couple of things I didn't like.
On the plus side its all nice an compact with long cables, which have nice protective boots on. Also the price is obviously very attractive considering the functionality. Much better value than the competition. The case and bezel are very nice, and the lens has a nice etched VEMS logo - but why is there no faceplate to cover up the PCB? I think its a real turn off for anyone wanting to install the unit permenantly in their car, as it looks untidy, and dare I say - cheap.
The other thing was the the main sensor power lead and the fuse blocks and connectors. These looked like an afterthought, with the power lead (in blue, the same as the main earth cable) running outside of the main cable to the sensor, and the fuse blocks connected with cheapo crimp connectors, which were not sufficiently insulated. Although these items are functional, it let down the product, and so I did what I usually do in these cases and started 'improving' it
For my install I didn't need want it to be permanent, so I installed the main unit in a pod, which protects the unit and looks a bit tidier. It also allowed me to temporarily stick the gauge in my glovebox, but fixed (fairly) securely so it pointed the right way and didn't move about.
Next I extended the sensor main power feed wire and fed it up through the sheath that goes to the sensor Yes this was a pig of a job - but it worked. This meant I had just one cable running from sensor to gauge - much neater.
Beacuse the unit uses the 15 pin connector for the additional signals, you need to solder some wires on to this in order to get the signals in and out. Personally I don't see the need for this connector. Automotive stuff tends to be chunky 'electrical' wiring not that flimsy 'electronics' type stuff. I also wanted to protect those fuse blocks better.
So I mounted the whole thing in a small box with cables exiting through grommetted holes, paired off into power/ground, NB0"out/NB0" ground and rpm/boost in. In fact I hd anted to use a connector block mounted in the side of the box with standard blade terminals, but maplins didn't have any nd I couldn't be arsed to order just one by mail order
With this in place, final touch was a bit of cable wrap to keep some of the wires bundled together, and this was the result
I would have run the cable wrap all the way to the gauge, but this was all I had lying about.
So with the unit tidied up, it was time to install it. As mentioned, I only wanted it fitted temporarily, so after a quick look at the size of the holes in the bulkhead (too small) I decided to run the cable externally and in through the door seal. A word of warning here. When it rains, water will now creep along the cable and down to the lowest point, so either make sure the cable turns up or don't go out in the rain. My glovebox ended up a bit damp.........
I had to pull the ECU cover off in order to get to the loom anyway (to install the HKS AFR and FCD - I know they're bodge devices but they suit my purposes for now) and so I mounted the box down here also. This made it easy to tap into the lamda sensor signal (to feed the NB02 output into the ECU) and pick up the rpm and boost signals if I wanted to. I then took the power feed from the main ECU feed so that the gauge came on and off with the main relay. Finally the gauge itself was mounted in the glovebox with some double sided pads, et voila a temporary install. (Please excuse the dodgy crimp connectors - i ran out of nice ones at this point but wnated to get it finished so used what I had about the place. Oh the shame....
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A couple of hours of thrashing about then confirmed my fears - the fuel system was not keeping up with the boost being achieved. The engine would hold about 0.88 lambda from 1 to 1.2 bar, but then lean off up to lambda 1 at 1.4 bar. Not good at all. This makes me think its actually getting to the limit of the injectors, but it may have just fallen off the end of the map. Either way, it needed sorting, so back to the house.
In the process of testing this, the exhaust fell off. Well, not off exactly, but it split one of the welds on the downpipe. This meant I hd to remove the downpipe and re-weld it, so while it was off I took the opportunity to add an EGT boss. Its post turbo, so only of limited use, but at least gives a better indication of whats heppening than no EGT at all.
I then trawled the web and discovered my problem was most likely the boost control solenoid having got full of oil when the piston went, and not operating properly. A bit of time spent with brake cleaner along the signal pipes and through the valve, and it did indeed sound like it was working better (the clicking from the valve was more pronounced, and not dull like when I started cleaning it.
So with it all back together off I went for another few hours of testing, and sure enough problem solved. Boost back to sensible levels (about 1.1 bar at 4000rpm dropping back to 1bar at 5000 and holding to the redline) and fuelling about 0.88 lambda. Post turbo EGT's never got past 550C, and it was interesting to see that under normal cruising conditions they tend to be about 300C, which is a bit on the cold side for catalysts to work.
So that was that. The units now back out again until I either use it for the minor or install VEMS in the Scoob. Which will happen first I wonder??
