Laying Into the 2017 Honda Civic Si

Well now that I’ve changed out the clutch on our test mule 10th Gen Civic Si I’m able to lay into it and see what this baby turbo with the 1.5L motor can really do. Thank you to ClutchMasters for providing us with a very strong clutch — it held up through all the abuse I just put this car through.

I am currently using KTuner on our test vehicle as this is the only software available to me that provides me with all the necessary control to really work on the innards of this ECU and dig deep into what this motor, turbo and ECU can do. Big thank you to them for providing the software we needed to get some serious testing under way.

Shut Up and Tell Me How She Did Already?

I have to say I am very pleased with the way this car not only drives, but makes power — it’s a VERY broad power curve and this is very noticeable when driving the car. She laid down over 255whp and 320wtq, and you can see the power curve is quite “fat”. This power was still made running quite an aggressive tune — but nowhere near any ECU or software limits.

However — for the sake of longevity I dialed the car back into the ~240-245whp and ~290-300wtq area for myself as I want the car not to just “make power” — which is something people tunnel vision on — but I also want it to be reliable. This car is our test mule and we have some more plans for it.

What About These Limits You Mentioned?

This was actually quite fun — in the ECU we’ve already raised all sorts of “limits” to allow us to make power (no throttle pullback, increasing boost targets, etc). However there’s always *something* lurking when you really push things. Which is exactly what I did — I went all out on the baby turbo to see what she could do, and sure enough, I clipped a very brutal boost “limp mode” type situation in the ECU that you can see killed power quite aggressively after 4500 rpm.

There’s two things we can discuss and analyze from this.

First — clearly the baby turbo can do LOTS of boost in the mid range — which continues to make a LOT of torque. As a result, our peak HP spot goes down in the powerband (and I drew in what a potential curve without the limits would look like given what I already know about the turbos capabilities after 5500 rpm). But as horsepower is just a function of torque — if you make enough torque you can make “more horsepower”. As you can see — we’re in the 270whp area! The side effect of this is you have to run the motor with a LOT more torque as your usable powerband for best acceleration actually goes down.

Which brings us to the second point — do you really want to be laying 340wtq into this motor? I think it’s very cool from a testing perspective to see what we can do — but may not be practical for day to day use or the longevity of the motor.

 

 

 

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.

Prologue

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!

http://vittuned.com/2016-civicx-1-5t-3-downpipe-front-pipe-combo-pre-order.html