Some of our best blogs are inspired by the questions asked by our readers. One question that we get asked regularly is: how much power can the stock engine and transmission in a tenth-generation Honda Civic equipped with the L15 turbocharged engine handle?

“I’m looking to upgrade to a W1 turbocharger on my CivicX and I want to know if it's okay to run it on a stock engine. I don’t want to blow up my car.”

It’s a bit of a broad question, but a good one. For many people, the car they mod is also the car they daily drive so it's important to keep reliability at the forefront. 

How much power can the stock l15 engine handle?

Well, there are a lot of variables and we will dive into a few of them soon. For the engine, our general answer is about ~375 wheel horsepower. This is around the max safe limit for a stock L15B7 engine. This is by no means a hard limit. We have seen some engines let go before reaching that power level and we have seen very few of them surpass that threshold. The best we saw surpassed 425 whp. That’s a bit of a unicorn. From hundreds of our own dyno sessions and thousands of tuning iterations/parts combinations, we arrived at ~375 hp which is the level we suggest that you start to have a serious conversation about the next phase of your build.

Now, let’s be clear, at 375hp the engine is not necessarily going to blow immediately, but it's more of a “Hey don’t be surprised if that thing pops”.

We suggest that if you plan to push the car past 375 or want to keep it at this level of power for a long time you start piecing an engine together on the side. You can start by locating a spare L15 engine block. Source rods, pistons, bearings, etc. Get all the guts you would need for a more robust bottom end. Find a machine shop that you can use to do your honing, boring, and assembly if you are not comfortable with doing it yourself. Another option is to save up for the purchase of an assembled short block. Either way, it’s a good idea to have a bit of reserve in case of such emergencies when pushing the L15 to 375 and beyond..

What sort of things dictate the longevity of your engine? Lots really.

The quality of the parts installed on the car. How aggressive or pulled back the tune is. How your tuner ramped the torque in (down low or does he have it coming on like a light switch at 3000 rpm?) How well are you taking care of the engine? Are you changing your oil in a timely manner? Did you bump up to a 5W-30 weight synthetic oil when you upped the boost? More power means more heat and you can help counter that with a heavier weight oil to keep the critical fluids in check. Also, be sure that if you are running ethanol-blended fuel you are changing your oil more frequently. Be sure and check out our oil blog for more info on that here. 

Let’s now switch gears to the transmission side of the equation. How much power can the CivicX CVT transmission handle? What about the 10th generation 6-speed manual?

Unfortunately, CVT owners are more limited.

We find that around 260 wheel torque is the limit for the stock trans.

More than that and we start seeing the belt slip and you won’t be going anywhere fast. The bad news is there are not really any CVT upgrades available. A CVT cooler will help some and prolong the life of the CVT, but you don’t have anything to beef up the internals and so hit that ~260 wall. 

Manual trans owners hit a stock clutch limit at around 280 wheel torque.

But no worries, there are tons of aftermarket clutch upgrades available that will take you further. Our rule of thumb for the overall limit of the stock tranny (gears, internals, etc.) is about 400 wheel torque. That's the “get prepared” zone. Just like for the engine, it's not a hard stop, but it's the point where you start getting prepared for a new tranny and should not be surprised if/when it lets go.

Your driving style will dictate what gear goes first. If you are a drag racer then 1st and 2nd take most of the abuse from the launching and hard shifts. Road race guys will see 4th gear being the one to give out the first. 

Case in point, don’t be afraid to mod some with the guidance above. Your stock bottom end can max out a larger turbo like our W1 and support some extra power from a W2.

Good maintenance and good driving habits go a long way toward the longevity of your engine and transmission. Throw on a cold air intake, bolt in a turbo inlet pipe, and go ham with more bolt-on mods and start pulling on those V8s.

Thanks for tuning in,

-Vincent