A Chad 18 Report post Posted May 27, 2021 (edited) So, As of yesterday my M52B28 powered BMW is running one of the Link G4X ECUs. It was dyno and road tuned and is currently running quite well. Plenty of torque in the low RPM range (pulls strong from 2000RPM) and a nice linear power delivery to redline. You might ask, "what do you want from us then?"... Well, take a look at the dyno printout below, specifically the comparison between the two curves, one curve is with VANOS engaged, one is with VANOS turned off. What we are looking at here is a significant reduction in power and torque with VANOS ON! I have my theories, please provide yours if you don't mind. - Could be that the intake cam is an aftermarket item? -Could it be that the intake cam has been set to be advanced even with VANOS off by previous owner? [Strange as I would expect to lose a great deal of low end torque if this is the case) FYI: VANOS unit was recently reconditioned and it is clearly engaging as we are seeing SOME sort of response on the dyno curve. Operation was also checked at time of reconditioning. The intake cam does not align with the cam lockout tool when the engine is at TDC. Edited May 27, 2021 by A Chad Quote Share this post Link to post Share on other sites
M3AN 4016 Report post Posted May 27, 2021 (edited) When the VANOS was rebuilt and reinstalled were the endpoints and starting angles checked using BMW's software (or something that can do the same)? If it's out by a few degrees it could have the affect you're seeing. Other than that I really couldn't speculate. Edit: my only experience is with dual VANOS S50's, disregard the above if timing the VANOS isn't applicable to the M52. Edited May 27, 2021 by M3AN Quote Share this post Link to post Share on other sites
jon dee 500 Report post Posted May 28, 2021 (edited) Because this stuff is kind of interesting, I had a bit of a poke around to learn what VANOS actually does And found this... Quote Electric Control: The engine control module is responsible for activating a VANOS solenoid valve based on DME program mapping. The activation parameters are influenced by the following input signals: • Engine speed • Load (intake air mass) • Engine temperature • Camshaft position • Oil temperature (MS 42.0 only) And a bit more... Quote The point is that there are no "fixed" rpms for Vanos to enable. It depends on the temperature, load (how much air is the engine sucking) and the RPM, and, under heavy throttle also depends on vehicle speed. Of, I forgot, it also depends on if you have a manual or auto transmission. So, quite complex. In general, with a warmed up engine (85+ degrees C coolant) and manual transmission, and light throttle: it should turn on between 1250 and 5200 rpm. With heavy throttle, it will disable at 4000 rpm if you're driving very slowly (+/- 10 kph), and at 4992 rpm if you're driving at 120 kph or higher. This probably is to prevent giving you too much torque at lower speeds/gears (wheel spin, safety measure).. And now I'm still leaving out some variables. But you get the feeling. M50TU and M52 Vanos is 100% identical, mechanically-speaking, but the rpms at which it enables and disables are probably slightly different due to different flow/torque characteristics. Basically, as a total novice to this kind of VVT, it seems to me that Vanos ON is good (except at idle) to improve cylinder filling through the mid-range. Somewhere around 4500- 5000rpm Vanos switches OFF to improve VE. So I would say that leaving Vanos ON through the full dyno pull does hurt your torque compared to turning it OFF at (say) 4500rpm. VVT is designed to improve torque at lower rpm's by reducing overlap on longer duration cams. However, for maximum performance at high rpm's you need the overlap to take advantage of better cylinder scavenging. Perhaps some experimentation with the Vanos switching point is in order to get the best of both worlds ? Cheers... Edited May 28, 2021 by jon dee Bored... Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2132 Report post Posted May 28, 2021 in my experience, it is easy to misalign the vanos on reinstall. there is no "keyway", presumably for balance reasons. it is a 5 min job to pull off, or 15 if your rocker cover and coils are in place. would pay to crack it open and check its all in order. what crank angle sensor are you using ? me and Chris Stoss's racecar has a link in it, there was a bit of faffing around to get a crank angle sensor that was compatable with the Link ECU. Quote Share this post Link to post Share on other sites
