I heard a theory once about wires:
If you put two wires on the floor, (side-by-side) and leave them overnight – when you come back in the morning they are twisted together. Wires have a life of their own. It must be true because I see so many cars here with wiring problems. For example: a wire has to run from A to B. It starts out at A, but somehow ends up at C. The car’s owner swears it was all wired correctly so obviously the wires are moving about in the night; there’s no other possible explanation.
Having established that wires love to move about, what is it that they hate? It seems they hate being connected to anything. A classic example was the car with a bad misfire that came in about half way up the rpm range. This coincided with the speed and load point where the outer injectors were supposed to come on. Since you can see the injectors on this particular car it wasn’t hard to establish that the back pair were not spraying any fuel, whereas the front pair were. Aha…obviously an injector driver failure because everyone knows that the injectors share a common feed. Except that is, in this case; where two separate feeds had been used. A quick check showed that one of the feeds was broken at the connector…obviously the wire had disconnected itself.
Mapping continued until we got above 5000 rpm when the engine began to misfire again. A look at the logging trace showed that the engine rpm signal was disappearing. A quick tug on the crankshaft sensor wire resulted in no rpm signal at any revs so off it came to reveal yet another break in the wiring. These things don’t take long to find but they are a pain. My job is supposed to be mapping of the engine, not re-wiring and fault finding.
This one had me worried because the owner had taken another ECU off the car to fit our system. The worrying thing is that all aftermarket ECUs work, you might not like how they work but they should work. It seemed to me that there would be a problem with the car rather than the previous ECU and that problem would end up with me - it proved to be the case.
The throttle pot on the bike throttle bodies gave no reading that you could make any sense of. For a start it was wired wrong but sorting that out left me with a problem. I could not get the tongue drive on the butterfly shaft to operate the pot correctly. It appeared to be a left hand pot on a right hand spindle. I had to fit the pot so that it was fully against the return spring when closed. That was the only way to get a reading and then the single retaining bolt did not line up! I have to confess I bodged it with a cable tie because my job is to map cars and I was up to me neck in “problem” cars.
It may not have been an elegant solution to the problem but as a temporary repair it worked and the car was mapped up okay. I have talked in the past here how I dislike bike throttle bodies so I will not go over it again, they work, but not very nicely.
Problem car number three in a single day was this Audi powered Elise: misfires and rough running. It had been mapped previously but not by me. The first thing I do with any new installation is go though the map looking at all the settings. It all looked okay apart from the fuel numbers seemed a bit strange. Then I discovered that the engine had 800+ cc/min injectors which explained a lot.
Looking at the map sensor settings they were set up for a Weber/Marelli 3 bar map sensor but on the live mapping screen it showed 92 Kpa with the engine not running. According to my baro reading on the rolling road computer we had near as damn-it 100 Kpa pressure in the cell. Closer observation of the reading showed that it was actually floating about, anywhere from 90 Kpa to 96 Kpa. Basically it was on the way to failing, if not totally failed already. A quick phone call revealed all: the sensor was not an actual Weber/Marelli part but an Ebay Chinese copy!
I can’t see the sense in this; you have a massively expensive engine yet you fit a safety critical part from an unknown source in order to save £40. Is it really worth the risk of losing an engine that cost thousands of pounds in order to save £40? The Chinese rip-off merchants strike again it seems. While I am on the subject can I also warn readers about the cheap pressure regulators from China, the shiny ones with the little pressure gauge on the side. Yes, we have seen them fail on the rollers too.
LS V8 Mazda
I have to confess to liking these “Batmobile” RX7s. Not with the rotary engine but with the big V8 LS motor. I have done quite a few now and this one was pretty routine at just 6.0 litres. There’s only one word to describe the sort of power these engines make: “lazy”. It’s all so easy; applying a little throttle you tap the keys and look up to see 200 bhp at the wheels.
For the engine size the bhp/litre might not be that impressive but at the end of the day you still have massive lazy torque under your right foot. I can’t wait for our own project car to hit the road. As I write Craig Taylor in Birmingham is putting the exhaust system on the car and it’s real close to firing up for the first time. I am not holding my breath or making any promises but we just might make Mallory Park for the PPC day...
MGB K 1800
Last issue (or the one before) I talked about young Ollie and his K Series 1800 MGB. The caption on the picture told the story of how Ollie came real close to winning his championship. However, if you read the copy it tells you that he did actually win it, a close run thing but he was the championship winner.
The car was back this month for a re-map on a new engine, in fact I do all three of the Neaves family cars, all MGBs and all 1800K Series. If you look at the cost of fitting a 190 bhp K engine compared to running a full race B Series engine it makes a lot of sense to go with the K motor. Surprisingly the original MGB engines are actually a bit faster over a lap but the cost is prohibitive compared to a K Series. Luckily the organisers recognise this and allow the MGBK into the series.