I started tuning the car this weekend. Running blended TPS and MAP. This means two tables (one is TPS versus RPM, the other is one is MAP versus RPM) that are multiplied together to determine the fueling. This is a quirk of ITB, as for many installs that use a single throttle body the MAP provides all the information needed. I guess that the flow isn't well formed after the ITB, so it isn't a simple relationship between the MAP and the amount of air going into the engine.
Anyway, tuning blended is tricky as all the tools assume a single table. Not impossible though.
So, I started with some kind of credible table.
Then Ran autotune on the MAP vs RPM, which improved things. Then I did the same again using more throttle and rev range, and things got better. Then I collected a datalog and used MLV (megalogviewer) to optimise the TPS vs RPM table.
All was reasonable. Then an autotune of the MAP vs RPM, and finally things were running nicely. It seems that I keep trying to change up to a higher gear. The car pulls nicely at 2kRPM and I get positive boost at 3kRPM even on a closed throttle, so the cruise is quite relaxed. There is a nice chunk of power at 4kRPM which builds in a quite scary fashion from 6kRPM.
I have put an dB killer into the exhaust. Two reasons. 1) neighbour annoyance reduction device 2) increased backpressure in exhaust. The second of these is counter to turbo logic, but it means that the previously inadequate wastegate now manages to control the boost almost adequately. Previously I was getting 0.7atm boost at 8kRPM, now I am getting 0.5atm of boost. In theory the spring should limit this to 0.33atm, but at least it is sensible.
The other thing that I wanted to do was to draw cool air into the intake. The intake is adjacent to the exhaust, and although the airflow should steer hot air away from the intake, it was always a worry. Now I have boxed in the filter and it only gets air from the outside (behind the front wheel, which isnt' ideal, but at least its cool). It turns out that this makes no difference at all!! The turbohousing itself gets pretty hot, and the pipework in the engine bay is aluminium and also seems to collect lots of heat, so although nicely made it seems to offer no benefit! According to the logs I was getting air temps of 58deg before and now they peak at 61deg. I am running a bit harder now, but either way it is rather disappointing. C'est la vie.
Back to the tuning. Car is now running like a demon to 7kRPM. Clearly I am a bit intimidated because the logs show me backing off the throttle as the revs rise. The problem is that at around 8.3kRPM things go a bit ugly. Stuttery with reduced power. Even the MAP drops off sometime. I tried adding more fuel. I don't want to lose the engine to detonation and there were some lower AFR readings, although they were all over the place.
Next I tried reducing the advance by a further 3 deg. At the moment I have it taking 5deg when at 8psi, and the base table is retarded by a couple of deg versus the NA set-up.
Here is a screenshot from Megalogviewer
The RPM gauge is wired into one of the coil channels (low tension) and it doesn't stutter. I don't know about the other channel.
The sparkplugs look alright, slightly red for 1 and 4, not sure what this is from (slightly worried because the anti-freeze is red) but hoping it isn't from that! The leads measure 16kOhm from spark plug to spark plug (dyna green 3Ohm coils) in both cases.
I tried increasing the dwell from 40% to 50% and that made no big difference, maybe some of the changes improved things a little, but nothing massive in any cases.
So, not sure what I have to do to fix this problem. I think it might be the spark blowing out, so have replaced the plugs with Iridium plugs, and closed the gap down slightly. But haven't tested that configuration as yet.
While I think about it I think I will fit an intercooler. From the Stoneleigh show I realised I could copy the way that Raw-Striker had fitted the intercooler to their show car, that is, it can be wider than the chassis at the front, which will make sourcing an intercooler much easier.
Also I need to fit heat shielding to the bonnet and paint the bonnet on the underside. Quite a bit of tidying to do here, but I measured the temperature at 96deg C (stopped after a run) which is scary hot and I don't want to burn my bonnet (or any of the car).
Car started reliably. Idled nicely. Didn't overheat. Really feel like I've turned a corner. Slight oil-leak, but it looks easily fixed! Happy days.
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