Hi all, could a worn dephaser pulley cause knock to be detected? I'm close to completion of fitting an RS250 engine into an R26. The R26 cannot manage the VVT so it's all unplugged/dormant. it's currently being mapped and the mapper is getting a good bit of knock/detonation which he thinks is possibly related to the VVT system being inactive. His opinion is the VVT could be varying in an uncontrolled manner and may be advancing too much. This is my poor paraphrasing of his feedback! I doubt this from my reading online but i'm beyond my level of understanding with it all. I dunno what could be causing the detonation/knock he is getting Have been wrecking @ianplymouth head with this recently! Some other relevant facts: RS250 Engine Rebuilt head, new valves, seals, guides etc.. New TB and pulleys but not dephaser (thought it a waste for something that I expect is not active) New TTV SMF Help me please!
This is the reply from the mapper just now "there is a lot of knock ie detonation not a noise. This is most likely due to cam timing which is possibly causing high egts, it's not breathing. I have removed a decent amount of ignition timing in the map that it shouldn't need. Unless the head had a lot taken off it and the compression is lot higher than expected" So when he said this it reminded me. The head was rebuilt and skimmed ever so slightly by me but it looked like it may have been tampered with previously too. Maybe it was skimmed already and we not alot taken off? I don't think we'll be able to prove that without removing the head and measuring it. Big issue is I'm in South of Ireland, mapper may be a little outside his comfort zone
Another quick update. Head was not skimmed when the valves were replaced so unlikely that we've a significant compression change...
Thanks Brigsy, Is it possible if a dephaser pulley is. Adult worn that it could allow it to move? Could it be locked in the advanced position? Lastly, could a solenoid be faulty allowing pressure through to vary the VVT? I'm trying to gather as much info on it all. I think he's concerned about how much timing he's had to remove to get it safe. I must clarify if he's managed to get it to run safely with no det by removing loads of timing or if it's still knocking
Chawkie What exhaust do you have ???? I did have a problem with my 225, couldn't put the amount of advance into the timing due to what we thought was a restrictive exhaust (Scorpion 2 3/4") changed it for a Pure motorsport system as the Scorpion gave me 4psi back pressure. It Helped but still not what it should have been, we put it down to the head being skimmed too much, it gave me 312hp and 360ft of torque, was happy with that.
I have a scorpion exhaust funnily enough. I think I can possibly get my hands on a milltek handy enough but there's only so much throwing parts at this car, it's bleeding me. The head rebuild was a complete surprise and if I had known all that, of have simply forged the engine I had. Hindsight eh!
The problem with the Scorpion system, is that there is one pipe going into the back box and 2 coming out, there is no direct path for the gasses, all the other systems i have seen have the one going in and one out but then splits. As for the head are you sure they haven't skimmed it, i knew mine was because of the damage, by all accounts they didn't take much off but it made the difference
Dephaser should be locked in position at stock timing. Id doubt the solenoid is causing it to move when not connected. As for dephaser moving, it would need to be checked i guess. Correct thickness head gasket fitted when rebuilt?
Comp might be up if its had a couple of skims, depending what you want a thicker headgasket might be advantageous. Has it been on the dyno
