Tested: PRL Motorsports CivicX RACE Downpipe

Well, after not getting any results worth talking about using my high octane fuel PRL has dubbed as my “secret sauce”, it was time to go back to low octane fuel and see what this downpipe could do — if anything. As much fun as it is to just push the motor and turbo to it’s full potential using the best stuff you can throw at it — testing on the average every day fuel most people will use is more realistic. And well — nothing gets more real than running this car on 87 octane, probably the lowest octane you can get in the USA (I’ve seen a few remote locations with 85 or 86 octane, but that’s really rare).

The results were pleasing.


I feel that I have to explain a little bit of the innards of the ECU here, so some of the results will make sense. For anyone installing the PRL downpipe and expecting some results with either the factory tune or one of the basemaps with their tuner of choice, you need to understand where some of the “gains” are coming from.

The CivicX ECU doesn’t use a standard turbo wastegate for boost control — it uses an electronic wastegate run by the ECU. This is more complex and actually very cool. Most “standard” boost control systems use a boost solenoid (mac valve or similar) and when you ask for, say, 20psi, it tries to target that immediately and let the turbo wind up as fast as it can.

This is not the case with the CivicX. Honda uses a “slope” or “ramp” style boost control. Essentially it knows “X” wastegate position means “Y” boost and will actually “ramp” or “spool” the turbo at a fixed rate to get there. This induces artificial turbo lag. I believe this is done in part to protect the CVT trans and possibly to protect the motor — as this little turbo has the potential to “wind up” (spool) VERY quickly if it’s unleashed.

So why is this distinction important? Advertising that anything will make “peak torque sooner” is actually not quite true. In repeatable and consistent tests peak torque is always the same spot as that is where the ECU finally lets the turbo reach it’s target boost. If we didn’t have this control in the ECU I can imagine peak torque being 2200-2500 rpm on this motor with this downpipe.

However, since the ECU is programmed for a STOCK downpipe, when you install an aftermarket downpipe (PRL’s in this case), the exhaust flows more freely and as a result the turbo will TRY to make more boost than the ECU wants and at potentially a little different “ramp” as the wastegate control in the ECU isn’t compensated for this new part.

So what did I find? When I tuned the car stock on 87 octane bone stock, I targetted 18.4psi and the boost level stayed very close to target boost. To try and give us 1:1 results at the same boost level, I actually had to target 17.5psi to get the same boost level I had before installing the downpipe. You can see this in the side by side comparison in the image to the left. I forgot to get this dyno comparison off the dyno computer before I left the shop, but keeping boost the same we saw 8-9whp on the top end and 10-20wtq gained. Keep in mind this is over our “stock tuned” 87 octane test — so we’d already worked on the timing map and fueling a bit as well. You’ll also note as we put load on the car before starting the pull — the turbo was already making almost 2psi more than before the downpipe — this will come into play later.

What does this mean to YOU? If you’re running the same tune with a freer flowing downpipe you will artificially increase the boost level a bit. This will have gains on lower octane fuel as you’re not at peak turbo performance on the stock downpipe on lower octane fuels. Just understand where those gains are coming from — it’s not all just the “tune” at this point. The ECU *will* try to normalize the boost control and bring it back down to the target as the pull goes on (as you can see it happening).

The Install

The PRL items, as always, are quality pieces. Very well done items and fitment on our car was like a glove. No rattles, no rubbing. If you don’t have a lift the install will be a bit more entertaining. On my lift it took about 2 hours to get the stock items off and this one installed. The studs in the turbo can be interesting — PRL broke theirs. I managed to get mine off without any breakage or stripping with the use of some magic lube.

Some pics, of course.

So What About The Toon?

Note: blue is HP, yellow is TORQUE, orange is BOOST.

So let’s try to give it a bit more boost and see what happens? Increased the boost level about 1psi (don’t want to go crazy with 87 octane) after adjusting the timing map and such — and the results were nice. 20whp and 30-32wtq gained.

Torque came in sooner too, right? Of course — if we didn’t have the “ramp” based boost control it would of come in even sooner, but we got maybe a 200-300 rpm improvement because the turbo just wants to GOOOO with the free flowing downpipe, even if the ecu doesn’t want to let it! Peak torque however — was still the same spot. This should never really change as long as the load & ramp rate of the pull is consistent (not all dynos can control this — and certainly load will vary on the street).

But hey, let’s try to give it a little bit more. In the dashed line we increased boost a bit more (with a few other changes), and as you can see the gains were marginal — a bit more torque, but top end HP actually suffered a bit. We’re now at the limits of the fuel and I was starting to see the knock limit approaching very rapidly — don’t want to run here long term at all for reliability’s sake. But hey, overall we still saw 5-8wtq more which amounted to 35-40wtq through the mid range and we still picked up 20wtq up top.

So if you want to run on readily available fuels and not go hunting for race gas or some sort of “secret sauce” (lol), then PRL has a great RACE downpipe. Expect to see diminishing returns in how much HP you can make with better fuel — on 93 expect maybe 8-10whp more with this downpipe. Of course more torque as well — if your clutch can take it.

Vs Bone Stone?

Don’t really need an explanation I think?

87 octane fuel.





Where can you get all these goodies? Right here, along with tunings and custom tuning!


Project Civic X — Bone Stock on High Octane

Just days after tuning the Civic EX-T bone stock on 87 octane I’ve managed to get the tank low enough for some high octane testing — still completely stock. Wasn’t an easy task running the tank low when it gets 40mpg on the highway!

But here goes… the results are FANTASTIC!

High Octane Vs 87 Octane

This doesn’t take a whole lot of explanation — we picked up as much as 60 ft.lbs. of torque more on the high octane fuel — and almost as much as 40-50whp more through the curve.

How’s this stack up against completely stock? Here you go — something like 80-90 ft.lbs. of torque more over stock.


Versus 8th and 9th Gen Si

Since we were having a bit of fun comparing the results of the Civic X vs the previous generation Si — might as well keep going!

Versus a bolt on 8th gen.


Versus a bolt on (RBC swap) 9th gen.




I could of actually made more power (especially more torque) on the Civic X on the high octane fuel — but I was cut off at the knees by the software currently available to tune these cars. So take these results as “software” limited. It is very early in the life of these cars and once we get more ECU development for the platform a lot more potential will be unlocked.

And keep in mind — this is still BONE STOCK. Time will tell what a few bolt ons will do (especially a downpipe).

Project Civic X Begins

Ever since the announcement that the new generation of Civic was going to be turbo we have all been anxiously waiting to see what Honda had in store for us. Turns out it’s a 1.5L turbo engine which the factory reports is “only” 174 HP and 162 ft-lb of torque. And this engine is also being released in the Si — with some cosmetic upgrades, transmission upgrades (limited slip — we’ll get to that later) and *maybe* a slight turbo upgrade.

The announcement of the 1.5L was met with a lot of criticism, as the aftermarket and enthusiasts are used to B18 and K20 style engines dominating in the four cylinder market making absurd power figures (1k+ hp). Hell, I like making that kind of power too and support quite a few people in their endeavors to chase big power goals in the Honda scene. But we need to step back and look at the actual market segment that these cars sell to — even the Si to a big extent.

So just take a deep breath…. and imagine you’re an average Civic buyer. What do you want? If I had to take a wild guess from years and years working with customers tweaking their rides — and you certainly have the folks throwing superchargers and turbo kits on the cars — the vast majority (by a huge margin) just want a peppy economical car. So where do most stop? Just simple bolt on modifications.

How much power do bolt ons pick up on a naturally aspirated Civic? Not a ton. How much do bolt ons pick up on a factory turbo car? Well from having done quite a few factory turbo cars on another platforms (Mazda, Subaru, Mitsubishi) I can say it’s a lot more than an N/A Civic, regardless if it’s a 2.0 or 2.4 motor in the N/A Civic.

Dyno Disclaimer

Before I get to the cream — I have to do this as this is just a never ending battle. “Bro your dyno reads high”, blah blah. Right, sure. Magically reads high for just one specific car and not a single one of the other ones we’ve baselined completely stock and are either right on the money or slightly lower than the average power figures we see elsewhere. I personally won’t claim a dyno reads “high” until it’s consistently high, over and over, across multiple platforms (you know who you are).

Bone Stock, Not a Single Mod

This little guy showed up today, fresh from the dealer (they even delivered it!). I drove it around and got some grub to get a feel for the car — it certainly felt peppier than a stock 9th gen Si.

It went on the dyno, bone stock, no mods. Just a Hondata FlashPro to get some testing under way… and a bit of tuning. A whopping 196 miles on the car.


What did she make stock? 181 wheel horsepower and 188 wheel torque. Wait… what? Yes I was a little surprised, I expected 160-170 area. This is also on 87 octane… not the best fuel. Of course I wanted to see if there was more in it. I proceeded to frantically smash on my laptop keyboard and I managed to pound out 192whp and 235wtq out of a completely stock 2017 6MT Civic EX-T on 87 octane.

I really can’t hate on these results. The “hp” is decent and the torque is fantastic — and this was only peak. Through areas of the curve we got as much as 55wtq and 30-35whp over stock. Not bad at all — for just a tune.

Comparing To The 9th Gen Si

This is going to go quick and easy. I’m not going to say a whole lot as the graphs speak for them selves.

First, a completely stock 2015 Civic Si and the stock 2017 Civic EX-T.

Then to the left, a fully bolted on (even RBC swap) 2015 Civic Si and a stock tuned 2017 Civic EX-T.

To put the picture in words: even stock the Civic EX-T makes more power through the whole power curve over the 9th gen. Almost as much as 80wtq more than the 9th gen Si. This makes for some great get up and go.

Comparing To The 8th Gen Si

Same idea here…

A completely stock 8th gen Civic Si and the stock 2017 Civic EX-T.

And then a fully bolt on 8th gen Civic Si (your typical quality bolt ons — nice 3.5″ CAI, Skunk2 RH, 3″ exhaust, etc) and the stock tuned 2017 Civic EX-T.

Historically the K20 has never been big on torque (well, until you slap a good turbo kit on it — but this isn’t what we’re comparing and that’s a whole other discussion). Almost 110wtq through most of the low end.

What Next?

Well as you see these results for the Civic EX-T were on 87 octane. Next up is some tuning on a higher octane fuel — 92 octane. Then possibly either 100 octane or some ethanol!

We also have some additional bolt ons coming soon for more and more testing…

The car definitely needs a limited slip! Maybe we’ll be able to snag one from the Si that is coming out?

What about a turbo upgrade? Yup, already doing some scheming here too.

And of course, we have our renowned  FlashPro + Tune combo offer you can take advantage of. For $800, it’s the best money you can spend on your car. I’ll make sure your Civic X is dialed in to suit your mods, your needs and the fuel you are using — and make sure it continues to run smooth and reliable for a long time to come. And as Hondata adds more features I’ll make sure your calibrations stay tweaked and up to date with the latest and greatest in the software — something I’ve been proud to do for customers on all the platforms we support.