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Need help with choppy power curve, 2004 CC Coupe, graph.....

2629 Views 5 Replies 3 Participants Last post by  Andrew
Hi Everyone,
I got the 2004 back on the dyno this weekend and the results were the same as before.
Previously, I thought the dealer had put in some low octane fuel as the car did drive a lot better with fresh premium gas.
Below is a dyno graph from about a week ago (600 miles on it) and this weekend with 750 miles and new gas.
The car does have a "new" or "reflashed" factory PCM (label from under hood is below).
The dyno pulls were in manual shift mode with the MSP off. I did runs in between in Sport mode, but it changed nothing on the power curve.
Are there any technical people with advice, or has anyone seen this before?
Once I get this taken care of, I can get the exhaust on it.
Any advice or input is appreciated.



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If I understand you correctly, you have only run 150 miles with the premium gas. If this is so, then there are two explanations:
- due to some old volume left, the petrol in the car is still a mix between old and premium, i.e. still has a lower octane spec
- engine settings are quite quick at adjusting to low quality gas (well, otherwise they might be damaged), and then only slowly adjust themselves to higher qualities.

Hi Martin,
Thank you for the reply.
I recently talked to the dealer the car came from.
Their service guys are not familiar with looking at dyno graphs, so they could not offer much input.
If the problem is the result of a bad "learn" by the ECU, I'll follow the normal procedure of resetting the adaptives.
Hopefully, that will take care of it as I've found nothing "wrong" with the car.
My "day job" is testing and developing automotive parts , but I'm very unfamiliar with the Maserati (this is my first one). This is something I've never seen on US domestic vehicles (we have a dyno at work and the computer equipment to link up to most all cars, including the Maserati).
I look forward to modifying it, but just have to get it to where it has a normal dyno curve first
I will post if the results are positive or not.

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after disconnecting the battery...

I had the car sitting in the garage a couple days with the battery switch off.
While I haven't had it back on the dyno yet, my wife and I both noticed that the tarnsmission shifts much smoother in auto mode than before. Where it used to have a delay (you'd feel the car stocp accelerating when shifting), it's now more like an automatic and very smooth.
Could be the ECU just needed a fresh reboot.
I'll get it back on the dyno this week.

Well, I got the car back on the dyno and the results were the same, so I began some testing.
We typically pull cars in 4th gear, but you can run other gears also.
So, I tried, 2,3,4 and 5th.
5th had the cleanest curve and the overall values were the same.
I then bumped the tire presure from 31 to 42.
If anyone else ever runs into this, have the dyno shop bump the rear pressure to 42 psi and do the pull in 5th gear.
Hope that helps anyone in the future.
Now I just have to find the time to add the exhaust and other mods I have planned.

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Thanks for the useful info. When you do find that time be sure to have the car dyno tested again to see the improvements and let us know what you did to get those improvements.

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