This have been going on for so long it's starting to feel like a constant change going nowhere. And it's time to consolidate my issues in one thread.
The car is a NB which started it live as a one-make race car built in Belgium for the Mazda Belgium 20 year anniversary.
It's a EU 99 taken directly form the boat to Kronos Racing which made very minor modification to the chassis (hopelessly stiff Bilsteins and 90/50 N/mm springs) and added a cage.
When i got hold of it in 2005 the odo read 8700km (5400 mi), track only, so it was just run in.
The stock engine served me well during the 2006-2010 seasons (just about 8 hours of track time per season) but in the Autumn of 2010 I got a VVT engine which I planned to get the most out of to move up a class.
I added a DIYPNP for the 2010 season 99 + DIYPNP 1.5 build comments/questions
to enable future enhancements.
The rules (written partly by myself) use levels of weight/hp and the power is either estimated based on stock spec or calculated using an empiric formula and some tables.
For me 1883cc and 7500rpm would be calculated as 195 bhp giving 1065kg (2348 lbs) min weight including driver (7kg/bhk, 5% extra for ABS), which is exactly where I'm at with close to empty tank.
If someone want to get a brain freeze the formula (for 4valve injected engines) is: 14.5 * ((Volume-1.1)*0.92+1.1) * ((MaxKRpm-6.9)*0.79+6.9) * (MaxBar * 0.6 + 1) = predicted bhp
For the 2011 season the plan was to port the head with +1mm intake valves, MS SUBs and run with the stock 10:1 pistons and stock cams.
The chambers were balanced at 52.5cc (not much unshrouding)
The flow values are at 10" water, CFM wet air followed by dry air.
Intake Port Original Intake 34.0mm
1.0mm 16.2 16.4 19.7 20.0
2.0mm 35.7 36.3 41.0 41.7
3.0mm 51.4 52.2 59.3 60.2
4.0mm 69.8 71.0 75.3 76.6
5.0mm 84.8 86.2 91.1 92.6
6.0mm 99.6 101.3 105.6 107.3
7.0mm 108.8 110.6 117.1 119.1
8.0mm 114.9 116.8 126.2 128.2
9.0mm 118.1 120.1 133.2 135.4
10.0mm 120.7 122.7 138.0 140.3
11.0mm 122.3 124.3 141.7 144.0
12.0mm 121.4 123.4 145.0 147.4
13.0mm 121.5 123.5 145.6 148.0
Exhaust Port Original Exhaust ported
1.0mm 12.5 12.7 12.5 12.7
2.0mm 27.0 27.5 29.3 29.8
3.0mm 44.3 45.0 48.0 48.8
4.0mm 60.5 61.5 65.1 66.2
5.0mm 77.8 79.1 82.5 83.9
6.0mm 89.8 91.2 92.2 93.8
7.0mm 95.9 97.5 98.0 99.7
8.0mm 99.1 100.7 102.8 104.5
9.0mm 100.9 102. 105.7 107.5
10.0mm 102.7 104.4 109.9 111.8
11.0mm 104.1 105.8 113.3 115.2
12.0mm 105.2 107.0 115.9 117.8
13.0mm 118.2 120.2
After three race hours a lash cap collapsed (at 7300rpm), then the retainer split, followed by the valve dropping be snapped by the piston
Dropped valve head repair
After this the old trusted unopened engine went back again and the full VVT build started.
The whole 2012 was run on the old engine due to waiting on all small parts that I continuously forgot to order (gaskets, o-rings, piston rings etc etc).
When I got the engine in October 2012 the energy was not there to get it done so it was sitting in the engine bay until late April.
When I was ready to start it up using the same settings as when the valve dropped (same intake, same exhaust, same injectors) it sputtered and was only able to get started on three cylinders once.
Custom VVT cam on a new build, startup problems
After verifying all (so I though) mechanical things I started to wonder about the decoding
How Retarded can a NB intake cam be for decoding to work?
But that was also OK.
Then i started to verify the builders work, trying to trace things backwards, and one intake valve on no3 had zero lash. Being unsure of my measuring method I did not think that much about it at first.
Missing out on the first race of the year I got some inspiration (while assisting an a number of late night teardown/rebuilds of heads and gearboxes).
So i strapped the belt onto the wheels, loosened the cam belt adjuster and pulled the intake cam and there it was, the suspected lifter sitting 2-3 mm higher than the rest.
Lifting the bucket and putting the lash cap back in place made everything as it should be (lash of about 0.2mm as all the other valves).
While it was sputtering on three cylinders I noticed the vacuum at 70kpa, which made me investigate Alpha-N (obvious but...).
After a couple of attempts I was able to get it started and also get a raised idle of 1800rpm, time for break in.
Breaking it in worked, but the idle was crap when warm (kind of disturbing in traffic) and it starts to get "on cam" at 5000rpm. Final max vacuum became about 60kpa at 2000 rpm, too little for MAP control and the VVTuner can work with load independent advance (pulling from low rpm will probably suffer if the whole low-rpm columns look like idle/startup values).
All starup and break-in was done with the VVT OCV disconnected, how it will handle the tougher ST springs will be interesting (others have probably done the exercise, but I have not found any reports).
Track time possible on Friday, more mapping (preferably all the way to 8000rpm) before then, it's not raining at least.
Dyno time sometime during the summer, maybe.
The Jenveys will have to wait since there isn't space and it require change to throttle placed injectors (the connectors collide with the flange), proper airbox, ...
Longer intake, shorter throttle bodies and curved trumpets would be a better solution, meaning selling off every part of the current Jenvey kit...