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I was excited to have the opportunity to get my car on a dyno last weekend and did a couple of baseline pulls. I was generally happy with the results, but I had one area of concern. On both pulls, there was a noticeable dip in the graph/drop in power at approximately 4300 rpm and then it resumes its upward trajectory again. Assuming this is not normal, what might be the cause? On my twin (sequential) turbo RX-7, there was a similar dip as the car transitioned from the smaller primary turbo to the larger secondary turbo, but that was a known phenomenon easily explained. I'm a big believer in dyno testing (and a real mechanical boost gauge) to reveal potential issues like this, but as I'm new to this car, I'm still learning what is typical and what might be problematic. Any thoughts or ideas would be greatly appreciated.
It should't dip like that. You really need to get it dynod again somewhere else to rule out operator error on the dyno and if there is still a dip maybe get it to the best Indy near you
There are lots of things that dip could mean. Without further information and more data it is impossible to answer, but my guess would be an issue with the variocam....just a guess at this point however without knowing more.
Data Log your Camshaft Deviation and Actual Camshaft Angle.
I had this exact same problem it was the Variocam Solenoid. As the engine RPM's and load increase the valve timing advances (Sort of like Honda Vtec) I cant remember the exact values but I believe that at 3600+ RPM the timing advances by about 30deg my Solenoid was in bad shape, so when I hit about 4000RPM under full throttle the Solenoids would disengage and the timing would retard giving it a hesitation.
This was only between 4-5000RPM in 3rd and 4th gear and only under full throttle. if I wasnt full throttle or in a different gear the the symptoms would not be there. Also there was no check engine light
edit: actually lots of times it can just be the bracket that holds the solenoid in place as it will corrode and the increase in load the oil pressure will "push" the solenoid out. There are two solenoids one on each bank in between two spark plugs
I have attached screen shots of my data logging for reference
So this is a bummer. Went for a short drive last night to see if the dip in the power band at 4300 rpm was noticeable under part throttle and noticed I now can't get more than 10-11 psi of boost in either normal or sport mode.
Boost leak??? or temperature correction "Limiters"?
Have you datalogged a 3rd to 4th gear pull?
I still have 100 octane in the tank from the dyno session. I'm guessing maybe I've developed a boost leak, although I don't hear any noticeable hissing. When you pull on the y-pipe in the engine compartment, how much wiggle-room and movement should I expect? There was more than I was expecting, but I've never yanked on it until yesterday. I guess I'm going to have to pull a bunch of things apart to check for leaks or come up with some kind of boost leak/pressure test. Given how much I've recently spent in upgrades (yet to be installed), I'm hoping I can track this down myself without having to pay a lot to a shop to troubleshoot.
I still have 100 octane in the tank from the dyno session. I'm guessing maybe I've developed a boost leak, although I don't hear any noticeable hissing. When you pull on the y-pipe in the engine compartment, how much wiggle-room and movement should I expect? There was more than I was expecting, but I've never yanked on it until yesterday. I guess I'm going to have to pull a bunch of things apart to check for leaks or come up with some kind of boost leak/pressure test. Given how much I've recently spent in upgrades (yet to be installed), I'm hoping I can track this down myself without having to pay a lot to a shop to troubleshoot.
I had a leak once when the diverter valve hose on one of the turbos popped off.. symptoms were similar to yours (boost tailing off at about 13 psi with no "noises" while driving and a slightly sluggish feeling). Easy to check before pulling everything apart.. also check the host to the FPR.
Bringing this back from the dead... Sorry for the noobie question. How do i data log? With a Cobb AP?
I used Durametric software, I am not sure whether you can datalog with accessport, but I am sure google can answer that question for you.
If you search the forum there are multiple threads on how and what to Datalog. Basically you have the cable, plug one end into your OBD2 port, the other end into your computer, put the car in the on position, launch the program, start the car, select datalogging from the options on the computer. select the sensors that you want to log, then go out for a drive
I just had Porsche of Hawaii test the Variocam and they say it looks to be within spec. I have no clue what i'm looking at, curious if anyone can clue me in. Their test seems much less thorough than the datalog pictured above. I am also trying to diagnose a very intermittent power dip similar to the one described in the OP.
I would say that those are snap shots that dont identify the RMP that they were taken at. Like I said in my original post over if this was on full load and over 3500RPM these are not good values, they should be in the neighbourhood of 30Deg. if these values were at idle with no load then they would be acceptable
I would say that those are snap shots that dont identify the RMP that they were taken at. Like I said in my original post over if this was on full load and over 3500RPM these are not good values, they should be in the neighbourhood of 30Deg. if these values were at idle with no load then they would be acceptable
I should've re-read your post again. The dealership does not have the capability to test under load at all RPM's since they do not have a dyno.
I'd hate to unnecessary new parts into the car, but if the Variocam solenoids are not too expensive, i guess i wouldn't mind. Do you know how much both solenoids will cost me?
you dont need a dyno to test under full load. I hooked up my data logger and made a run from a stand still on a freeway entrance up to freeway speeds under full load and was able to capture the problem.
Either way I dont think the cost was too bad, I cant remember and exact figure off the top of my head. Labour was the same cost as doing spark plugs, there are two sensors each was about $300 I think. Another possibility is the mounting bracket for the solenoid. It seems to be a frequent problem as well. where the bracket corrodes and breaks, then under full load the oil pressure will push the solenoid back and give false readings. I think the brackets are $12 each.
Did you bring it to and independent shop or dealership? This may be the instance where it is worth spending the money at a dealership to have it properly diagnosed
08-03-2017, 02:33 PM
Baseline dyno - power dip at 4300 rpm?
