Nelson Peltz is a rabble rousing investor.

When he buys a stake in a company, it can lead to the ouster of a CEO. Often he will demand a board seat and then push for a break up of the company.

But his massive investment in GE (GE) comes with no such demands. At least not yet, even though the $2.5 billion stake in the iconic blue-chip company is his biggest bet ever.

So far, the activist investor is taking a decidedly gentler approach to General Electric.

Instead of rebuking management, Peltz chastised the stock market for failing to appreciate the turnaround GE has embarked on.

"Management has taken bold steps to reshape the company," according to a white paper published by his fund Trian Fund Management. "We believe management must be given credit for the transformation that is now underway."

So far, so good. Shares of GE soared 4% on Monday on the Peltz investment.

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Good riddance to GE Capital

For the most part, Peltz and Immelt -- who have a cozy history -- seem to have a similar vision for GE's future.

Peltz applauded Immelt for his plan to jettison much of GE Capital, the conglomerate's finance arm. GE Capital created huge problems for its parent company during the 2008 financial crisis and would have been a burden in today's tougher regulatory environment.

The thinking is that instead of worrying about Dodd-Frank, GE and investors will now be free to focus on the company's industrial business. GE is already the world's leading maker of many things, including gas turbines and commercial jet engines.

GE sells GE Capital unit for $26.5 billion

Immelt in the hot seat

Even though it's starting on a friendly note, Peltz's big investment in GE adds pressure on Immelt to energize the company's lifeless stock price. And even though Peltz is not seeking a board seat, he warns that he "expects management to deliver on its commitments."

The activist even pointed out how GE's stock has gone nowhere since Immelt became CEO nearly 14 years ago. It's actually down 33% over that span -- even after accounting for Monday's big rally.

"We believe investor skepticism towards management has created a mispriced security," according to Peltz's firm.

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Peltz says GE could zoom to $45/share

Peltz has a track record of brawling with CEOs. He recently waged a long and ultimately unsuccessful battle with DuPont (DD) aimed at forcing the company to break up its chemical empire.

Now Peltz is turning up the heat on GE to execute on its turnaround. He believes GE could be worth $40 to $45 a share by the end of 2017. Peltz believes GE can get there if it accelerates plans to cut costs, dumps even more of GE Capital and ramps up share buybacks by taking on debt.

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GE welcomes Peltz

GE seemed to embrace Peltz's involvement. Immelt said in a statement that he welcomes the investment and Trian's "strong track record of working with companies to build long-term shareholder value."

GE actually considered Peltz for a board seat in 2007 -- before the financial crisis hit and increased the need for directors with strong regulatory backgrounds.

Peltz even called Immelt in April to congratulate the GE CEO for his plan to exit GE Capital. Immelt told Peltz GE "would love to have" the activist in the stock.