The compression ratio of a standard 2.5l is 8.8:1. The super eta is at 8.5:1. Mathmatically, if you drop the 2.5l down to an 8.5:1 compression ratio, you will only loose 1% of your max hp, which equates to around 2hp if using stock figures.
If you mate the more aggressive cam of the 325i and the ability to reach 6900 rpm's, these engines become much closer to each other in terms of performance if you ignore where the max torque kicks in.
The super eta stroker in most cases doesn't necessarily produce more hp or torque than a 2.5l, it just moves the power band to a more desirable location. If you're running the car on the street, having torque available much sooner is very nice. If you're on a track with sharp corners that require the engine to drop below 4500 rpm's, again, the stroker is nice to have.
However, if you're driving on tracks that have long sweepers or use it on the drag strip, I'm not sure the stroker is a great choice. I think to some extent, the reason for building one of these should be its use, not so much that you want to create more power, since it really doesn't unless you buy a kit or have significant machine work or customization performed.
There are many other options to consider when building a stroker from stock parts if you're willing to spend some time doing calculations and spending money on machine work. There are other pistons that will work if shaved, that can be used in combination with other rods to achieve similar results.
If you mate the more aggressive cam of the 325i and the ability to reach 6900 rpm's, these engines become much closer to each other in terms of performance if you ignore where the max torque kicks in.
The super eta stroker in most cases doesn't necessarily produce more hp or torque than a 2.5l, it just moves the power band to a more desirable location. If you're running the car on the street, having torque available much sooner is very nice. If you're on a track with sharp corners that require the engine to drop below 4500 rpm's, again, the stroker is nice to have.
However, if you're driving on tracks that have long sweepers or use it on the drag strip, I'm not sure the stroker is a great choice. I think to some extent, the reason for building one of these should be its use, not so much that you want to create more power, since it really doesn't unless you buy a kit or have significant machine work or customization performed.
There are many other options to consider when building a stroker from stock parts if you're willing to spend some time doing calculations and spending money on machine work. There are other pistons that will work if shaved, that can be used in combination with other rods to achieve similar results.
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