Moving the cam timing means a change to fuelling and burn requirements to optimise to true torque of that configuration. Of course it can be experimented with until there is no benefit. In your case the area you could customise was the fuel mixture requirements with the global 1.8 litre spark table shifted by dizzy movements. This is not ideal to get the engine running to its optimum. From what I can see the engine is naturally running out of torque past 5000 rpm. Spark tuning would have helped to slow this ramp down and say at 138bhp where the engine was achieving 127lbft@5700 of twist. Tweaks to spark timing if its was short of MBT may have meant a torque increase to 131lbft. You then be boosting your engine had 142bhp@5700rpm. This still may not be a good reason for installing a standalone as a stock ABF engine will be significantly stronger at this point. But imagine being able to optimise the whole calibration like that...
..so an hour on the rollers would be enough to balance cam and spark whilst maintaining AFRs I have to add that i am more than happy with the service and results achieved by Vince @ Stealth...i am just anal and feel there might be a "little" more in there but i wouldnt want it to be to the detriment of torque
No... not with that much mileage... that's an old wives tail.. unless it was very tight to start with. Yeah I'd imagen it felt strong low to mid, and similar to a KR 16v near the top but with less rpm.
It maybe worth a try. But as you say... as long as the torque is strong...which it is... you are only likely to improve the top end torque/power. . . I doubt the mid range will pull up much if at all.
Assuming the max VE was achieved, I am of the opinion that the torque can be plateau'd from 3000 to 4500 or so. To do that you need customised spark adjustment to further optimise cylinder pressure. With the cams in the same position I would not expect a characteristic change in torque post 5000rpm but there maybe a few torques hidden in there with further tuning. My thoughts are focused on these plots only. The profiles post 5000 rpm could change if tested elsewhere even though the car's acceleration in real life would not.
we ended up 6 degrees retarded from equal overlap on no4 and couldnt go any further on the vernier scale......leads me to believe the cam is a tooth or 2 too advanced as equal overlap was 12 degrees retarded on pulley so i would also like to adjust that to give me an equal swing on the pulley
thats what i needed to hear ......i had no real experience of the 8v prior to buying this mk2 as all my previous vags have been abf/kr/1.8t....i could only go on what TSR quoted as what they can achieve "if set up right" which worries you to thinking its not set up right ....i am not unhappy with the engine more the 20 or so bhp that engine builders over quote by....surely that would need open induction to hit those kind of figures?
do you think a modded airbox would yield me more with a high flow panel filter in there?...is the k+n cone likely to be insufficient?...it is shrouded well with a cold air feed although the inlet tube is a little longer than standard
The AFM is the single biggest restriction on that configuration especially at high engines speeds. If the air box is not already de-restricted I would also try this, something I am sure the Stealth crew should have picked up instantly. It still would not be an ABF beater, but there is a possibility that the midrange could be enhanced and the torque ramp down slowed down as the engine runs out of pumping efficiently.
...so its probably at the best balance within the limits of the digi system..albeit with higher flow injectors
Digifant 2 is controlling and engine with a cam and cc increase which is unique both in its efficiency and the way it pumps air. This is assumed to have gone up from the spec found on a std 1.8 PB. The G60 injectors ensured you could not 'run out of injector'. The ECUs fuel table would have the injection duration reduced to run modified injectors as well as re profile the duration to meet target AFR. The target would be based on the tuners knowledge of engine combustion and experience of the specific engine. However optimum torque will be to greater extent affected by spark angle settings and in the case of digi2 I know of none who can make changes to the CPU cache, where the spark tables are stored. You need to adjust this to suit your new custom engine. The custom fuel curve is not enough and spinning a dizzy only takes a non matching spark table and make it match to some small speed load areas and mismatch everywhere else and we are only talking about WOT conditions. So yes you may be at the limits of the control configuration but the engine even with a fully programmed system will still be an 8v in its torque delivery give or take some trimming and smoothing here and there.
..yeah vince did say the spark tables were an innaccessible code that made no sense are there no OEM ECUs that can be utilised with a MAP sensor to remove the restrictive AFM? i know there was also talk of the BMW afm off a 530i but i found no definitive proof that it worked or could be calibrated to a smaller engine creating less vacuum pull than 3ltr 6 cylinder
BMW E34 AFM I have tried and did not work. There was a mismatch with the resistance card and the flow character of a bigger hole. OE ECU yes a Digi1 or G60/40 unit.
hmmm...so a G60 ecu, engine loom and throttle body with TPS at the right price could solve any breathing restrictions eh would it need mapping or could i utilise the stealth chip for fuelling?
Well there's 2 probs to start with... sounds like the basic cam timing is as you say out s tooth or so. Plus, from the split / equal lift point you should only ever need to advance.. sometimes this picks up just the mid range. . . sometimes I'll pick up mid and top end.
