Investigation after dyno session. No power after 4500RPM ? S124 V8 Turbo
The questions. What is wrong, There are a few things that i’m considering. And also a few that where not visible. We had a stable lambda value also after 4500rpm also boost was stable . only the Power output was going down and was unstable.
What am i going to check. First get the downpipe of to get roo. Also Lambda sensor needs to be changed. All plugs out. The plugs look more colored to enough other so no real difference between bank 1 and 2.
Next is to check if TDC cyl 1 is real what the pulley is telling us. This marking is correct so alos the ignition timing is correct. To take the valve covers of i need to remove the turbo to get the bank 1 side of.
Both covers removes. everyting look nice and clean just like when i assembled it. First check the base timing setting so crankpulley on 40 degree after OT1 and both cam gear markings are correct.
Second is the opening and closing of the valves, On this ZAS engine there is on very strange value .. That is that the left cam so that is driverside cam. The intake valve is closing at 14.8 degree after BDC this is almost 14 degree earlier then on the right cam. so the conclusion is these 2 banks are breading different from each other.
So i think the problems that we have are from a few things together. Then cams difference. Backpressure been over 2 times the boost pressure already. so turbo size for this setup. and because of this i think i already had some valve float.
I design and build this turbo system for 500HP on pump fuel so higher rating then i now tested. but not for E85. So for that power level this would be good enough. maybe turbo still a little small but with normall 5.0 cams and double springs the backpressure would not have been a problem i think.
But because i made the choice to go for flex fuel. This system is on the tight side. and also the turbo.
Things to consider now are. Upgrading the turbo system including manifold up to the turbo. Bigger. Bigger turbo that can flow upt 800-900HP. so i can get in the ballpark with the 750hp crank. Bigger downpipe up to 4″. this needs to have so mods in the engine bay to get the 4″downpipe through.
This is it for now. lot’s to think about
JMSpeedshop.com