I have a friend who run with 9L and it say to me that the 7XL is a little weak for an e-maxx...

Weak?!? The 7XL is longer than the 9L, so it can't be weaker. It is slower, but it makes up for that with its higher power capabilities.

a 7xl is stronger than a 9l and geared right will toast a 9l.

The lehnher XL 2800 or 3100 is also a good choice or not ?
What is the better between the feigao 7XL, 9L, lehner XL2800, XL 3100 ?

In terms of what? The 7XL is the most powerful, but the XL 3100 is the fastest. The 9L might have a little more torque than the XL 2800, and it has a 5mm shaft (the XL motors have a 3.17mm shaft).

In effect, I want to buy a motor which have a good compromise between speed and torque (fast and many torque)

I say the 7 xl is a good motor. Weak i don't think so. It would pull wheelies at 50+ mph. That is how i crashed mine. I run a 14 l and it don't have near the power the 7 xl had. If you get the 7xl and run it with a 7020 the control will hold it back some. The controller will not last but so long because of over load.

7XL get's my vote..

I would say dafni's to there serum.

For ultimate reliability, the 7xl, warrior controller and rc-monster heatsink/clamp is the best dollor for dollar performance buy, in my opinion(I do have a bit of experience:)). The Lehner basic xl motors are also excellent motor, with impressive runtime and power output. They will run a bit warm in a particularly heavy truck, though, while the 7xl can handle the heavy trucks much easier. On 14 cells, the 7xl is very happy to deliver power and speed(as much as the batteries can deliver) without overheating. There are better motors and better controllers (BK has several upgraded controllers, and Lehner has many high end motor in their line), but none that offer the price/performance ratio of this combo.

Amen..

I go along with that as well. amen

thx for your answer mike !

Right now i'm using an HVmaxx setup with two 6cell 3300gp's. My truck weighs a tad over 9lbs with batteries installed. I've been racing it a bit at the local track but I have only Nitro's to compete against. The A mains run 15 minutes and what i'm wanting to know is what would be a better brushless setup to compete with these nitro guys. If i gear the HVmaxx for longer running, i can't keep up with them, especially on the straights. They get to pit but if i pit to change batteries, i lose. Is there a system i can replace the HVmaxx with that will give me the runtime I need for the A main and the speed to keep up? I'm soon going to be getting a set of the Intellect 3800's and will most likely use 14cells. I'd like to stay around $300 -$400 mark for the brushless.

I don't know why people are so obsessed with the Maxximum? They are way too expensive for what they deliver.

I am also suprised no one said anything about the Hacker C50 range, I know someone with a C50 10L on 16 cells it beats any nitro! So much power and so much speed, although low runtimes.

I think the 9L is good for 14 cells. :)