Part 3 – Engine Healthcheck….and more…
The delay in proceedings and having to wait until after the dyno cell upgrades were finished actually turned out to be extremely beneficial. With the mileage on the rebuilt engine, it was a good time for Matt @ Fearnsport to inspect the engine and do an oil change. In fact, my ask of Matt was more than that…
1. Leakdown & compression test the engine
2. Set valve gaps
3. Check head stud torque
4. Change the engine oil
5. Send an oil sample away for analysis
6. Fit new smaller injectors. I hadn't actually ever got around to selling the original set of Siemens Deka 630cc injectors from Engine Build #1, so I thought I'd send these up to Northampton for cleaning and swapping into the car. Unfortunately they wouldn't clean up well enough despite many cycles. The closest they'd recover to was with a delta of 6% across the set. Nowhere near, which was a shame, as they certainly delivered the numbers many years ago and were practically new. Northampton Motorsport, by coincidence, had a set of 8x Bosch injectors in stock, that had been measured on their injector rig. By selecting the best 6, we had a delta of <1%.
There was also one more interesting additional job…..(prepare yourself, it's another anecdote...)
When Chris (Northampton Motorsport) was solo driving the car down to Fearnsport (Silverstone circuit, about 10-15miles away) he was able to reconcile some thoughts on how the engine was driving, without interruption from somebody wanting to do live calibration tweaks. Apparently, when he arrived at Fearnsport and chatted with Matt, he queried the eThrottle pedal and whether it was perhaps broken. When Matt then informed him that the car didn’t have an eThrottle pedal but was still running the OE cable throttle, the lightbulb moment happened.
As long time readers may remember, many years ago I swapped out the Porsche throttle linkage on the engine for one I fabricated myself. It took many days to build and weld, and was done to accommodate an Audi eGas potentiometer, a rotary device operated by a short cable. I spent a lot of time getting the leverage ratios correct and bushing the pivots to make it as slack-free as possible. Way-back-when I do remember having a conversation about trying to use a BMW eThrottle pedal but dismissed it as looking too aftermarket and possibly not even fitting.
Consequently, I’ve always used a setup thus:
OE Pedal >>OE (and original) throttle cable to engine bay >> Actuating my home-brew linkage >> In turn actuating the Audi potentiometer >> Then the electronic signal from pot to ECU to 997 throttle body.
With the lengthy cable, throttle linkage “play” and then the short Audi cable, it’s little wonder that Chris described the driveability being like the engine is disconnected to whatever his foot was doing at the throttle pedal. Kind of kicking myself now. Like everything, hindsight is 20/20 and a wonderful thing.
As it happens, Matt had also investigated using a BMW pedal in another customers car (a lovely “Altzen” 964 RSR). I don’t mind admitting that I rather too hastily dismissed the use of said pedal back in the early days of this project. It looks absolutely stock when mounted correctly, as Matts other customer will also attest. So….Job #7 for Matt was to mount an E46 BMW pedal that I sourced, and get it wired up to the ECU. This was done, and I think you’ll agree, looks “factory”…..
Wiring is actually run back from the new pedal to the engine bay and interfaces to where the Audi unit was connected previously. If starting again with a new harness, then obviously we'd keep it inside the cabin and directly into the ECU, but at this stage that would be really messy, hacking the Raychem boots around and then "orphaning" the part of the harness that runs to the engine bay. Plus, it gave us a backout plan should the BMW pedal not work out for us. (spoiler alert, it did)
The leakdown numbers were exceptional (cold engine, obviously):
Cyl 1 = 2%
Cyl 2 = 1%
Cyl 3 = 1%
Cyl 4 = 2%
Cyl 5 = 2%
Cyl 6 = 1%
Not sure which cylinder this is, either 2 or 3.
Valve gaps were reset, and none of the headstuds required tightening. Inspection of cam lobes also done, with Matt also being very happy with them.
We’re still waiting for the oil analysis to be formally returned; Opie Oils, who are doing the testing, ran out of consumables to do spectrum analysis on metal contents, and being Xmas period/Brexit/blah blah blah, we’re just waiting for that to complete. Informal feedback from them though, is that all other parameters are fine and nothing to worry about with the exception of the fuelling being a bit high….but we knew that anyway and was being worked on with the dyno session.
With the installation of the Bosch 630cc injectors, the next job was to try firing it up and make any calibration changes that would enable Chris to drive the car back from Fearnsport to Northampton Motorsport.
Encouragingly, it burst straight into life, no changes needed and idled just fine. Chris them remoted-in via Team Viewer to the Syvecs and pre-emtively made some fuelling changes in advance of travelling across to collect the car.
At this stage we’ve got a clean bill of health and we’re all set to go onto the dyno up at Northampton Motorsport the following day.....