Hi everyone, My car has abnormal high torque but low horsepower - and I don't know what could be wrong anymore. Dyno figures: 354 engine hp @ 7200 rpm 409 nm / 301 ft-lbs @ 4900 rpm I find the shape of my dyno curve unlike any other 360 dyno sheet I have see. A sharp peak in torque, and a drop-off at high rpm - not making peak power in the 8000 rpm+ range. I can also feel the drop off whilst driving. List of mods: - Tubi headers - 200 cell high-flow cats (quite new) - Tubi sport exhaust - Trev360 tune Recent maintenance: - Spark plugs - Coils - o2 sensors - oem air filters - cylinder head revision (lower dyno #'s are from before revision) This almost makes me think there is a mechanical restriction of any sort. Ideas? Image Unavailable, Please Login
First thought was advanced cam timing but it makes peak torque at the correct rpm. So, I would guess the butterfly's are not opening in the intake runners so it's staying on the long runners.
Make sure when they disconnected the exhaust valves they plugged up the vacuum hoses. It's the same pneumatic/vacuum system that operates the exhaust valves and the intake compensator valve. If there is a leak anywhere in the system, it won't operate properly. Image Unavailable, Please Login
Thx @sammyf and @INTMD8 for pointing in that direction. Indeed, the hose before the actuator was just lying there not plugged off. Would it really be that simple? I plugged it off, waiting for a dry day now. Also, should the electrical plug be disconnected from the solenoid? I indeed have a Tubi without valves Image Unavailable, Please Login
With the valves connector not connected, plugging or not the hoses will make no difference. With no power the valve is connecting the open hose to the open metalic port, and is closing the 3rd port coming from vacuum tank.
Thanks Eric. My only other option if it's not the intake would be the exhaust and too much backpressure, or the variable cam timing?
It could if there is any leakage at one or both exhaust valve solenoids, especially being a 3 port solenoid. Cut the hose after the hard lines that go to the solenoids (and back to vacuum canister) and plug them. Or pull them at the canister and block with vacuum caps. And/or pull a line off the canister to see if it stores vacuum. Or record the linkage to valves with your cell phone and see if it moves. Don't think it will.
Trev’s tune yields higher torque, and your horsepower really isn’t that low, if at all. I think my CS dynoed 370/270 at the wheels with tune and mods.
Check if the cats are clogged. I had dislodged a piece of an aftermarket cat that restricted breathing.
These are engine HP numbers, unfirtunately there is a problem. Today I made an exhaust back pressure sensor. I think its safe to rule out backpressure as a problem - i get a max of 2psi whilst driving till redline. As we can also see, I compared power with a stock 360. There is really something that restricts the power up top it seems. If exhaust side is not the problem, I think I have to look at the intake side again. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Got the MAF reading from the obd reading of the dyno. Looks like no more air is coming in after 6500rpm. Image Unavailable, Please Login
Ok, been busy today and have some updates. I started by placing my DJI camera next to the intake to see whether the butterfly valves open to switch from the long to the short runners at high RPM. @INTMD8 was right, the runners are not operated. Also found a loose screw, tightened it. I put 0.5bar vacuum with a mitivac on the actuator and went for a testdrive, to test whether the actuator leaks. Pressure stayed stable for an hour, and car felt much stronger at peak RPM. I then tested the solenoid, at least to see if it got power. There are two solenoids, they look identical but one has a brown plug and the other white. Im not sure which one goes where, as i found pictures online with the brown plug towards the back of the car and the white one towards the front. On my car they are reversed. I switched the plugs around, but only saw the actuator for the runners move once very briefly and directly go back. Next i checked vacuum coming from the vacuum canister. It holds -0.3 bar, which immediately disappears once I touch the throttle or shut down the car. My theory is now that the solenoid works, but it's fed with insufficient vacuum to distribute to the actuator operating the intake runners. I'll need to look into the vacuum system. Image Unavailable, Please Login
Here we go. What an unbelievable feeling after 15.000km of ownership to have the car working as it should! Finally i have top end power, and it feels like a completely different car. What I did to troubleshoot, was to mount a small vacuum pump and feed the actuator directly. The vacuum coming from the intake is low, but also doesn't hold vacuum when going on the throttle. I have ordered 2 new check valves, which hopefully solves the problem.
Ordered 2 new Febi Bilstein check valves...problem solved. A stark reminder that working on the car myself vs going through shops and specialists is still the way to go for me. This has been a very,very expensive journey.
@INTMD8 Mainly new valve guides, valve seats, clean the valves, head flattened, gasket refresh, rebushing of inlet manifold against rattling/play, etc.
