VitR — Scraping the Bottom of the Barrel

No the title isn’t a shot at the car — I’m finding it to be a great car and the motor is turning out to be pretty solid. There’s just one thing that’s quite annoying — Honda gimped the potential of the motor with the fuel system. The D/I fuel pump is pegged out very easily once you turn the power up, which in fact leaves you literally scraping the bottom of the barrel to make a clean power curve as you’re riding a very fine line with the fuel system.

This turns out to be even more true once we put on the PRL Motorsports Intercooler on the car and found out it improves cooling efficiency to a point we were making the power we had before while running less boost. Of course we wanted to make more power and run more boost — which proved futile given the limitations we kept hitting in the fuel system.

The car is 100% OEM aside from the PRL Intercooler and we used E35 blend fuel for this test (as we wanted to see how much more we could push the motor).

Intercooler

So what did the results look like? We were able to make a clean power curve and pick up more power before the fuel system maxed out — and make roughly the same top end with less boost.

But that’s not good enough! Let’s make more… and we certainly tried. The motor wants to make power — but takes a slump after 6000 rpm. Why is this?

Well here’s why — in our MoTeC programming we’ve added code that estimates how much injection time you have left before your spark event. You need a certain amount of time left over for a clean mix in the combustion chamber before the fuel is ignited. Do not leave enough time for this to happen the engine doesn’t make power or even worse — misfires. It appears that on this motor we want at least 1.5ms of “Injection Time Remaining” to get a complete mix.

But as fuel demand on the D/I pump goes up it skips a beat and we see a large fuel pressure drop — from a target of 22.5MPa to 16.6MPa (a 6MPa or almost 900psi drop in fuel pressure). As a result of the pressure drop the injector pulse width has to increase and now we’re running out of injection time!

Really Push It

How bad does it get if you REALLY push the D/I fuel system? Well take a look at this. Wow it’s just a roller coaster ride after 5500 rpm — we were making over 390whp and would of made well over 400whp if we had the fuel…

 

You can see how tapped out the D/I fuel system was on this 29psi pull as we dropped 8MPa of fuel pressure.

Injection time remaining was super low… and the motor even misfired at 6600 rpm.

 

 

So Did the Intercooler Help?

Absolutely. Here’s some useful data from actual hard acceleration runs on the stock intercooler and with the PRL intercooler. You should note — we actually used a bit less boost on the stock intercooler runs and the stock intercooler had colder ambient temperatures versus when we ran the PRL intercooler test. However the stock intercooler still heat soaked rapidly. For comparison are runs at WOT from 1st to 3rd gear.

First on the left is the stock intercooler. Note the following — “Airbox Temperature” is the temperature sensor in the intake BEFORE the turbo and the “Inlet Air Temperature” is the temperature sensor in the intake manifold. The sensor in the intake manifold tends to heat soak at idle/low air volume conditions (not much fresh air flowing through the intake manifold).

 

On the right is the run w/ the PRL intercooler. You can note that with the stock intercooler the Inlet temperature never touches the airbox temperature and in fact starts to climb almost immediately after dropping. With the PRL intercooler the aircharge is rapidly cooled and comes down to match the temperature at the airbox — and stays steady all the way through 3rd gear and would *maybe* start to slowly climb in 4th gear.

Clearly the intercooler upgrade is worth it — especially for our road course folks.

Some Fun

After having the car for a while and getting more comfortable with the clutch — I wanted to see if it would hold a bit more torque. I brought in 23-24psi earlier in the powerband, held 24psi through the top end — and made ~390hp and just a hair shy of ~400tq.

Is there more potential there? I believe so — I think we can probably make 450wtq quite easily — if we had reliable fueling. We had a 6MPa pressure drop and the fuel pressure just did not look that great.

 

 

Some Thoughts

Yes — this is E35 fuel (we had made 360whp on 92 previously), but there will be comparable gains from this intercooler on pump gas as well. The E35 actually doesn’t bring up fuel demand *that* much over pump gas (which is E10 to begin with) — it’s about 10% more fuel. So what’s that tell us? Where the hard limit is for fuel volume with this D/I fuel system.

How much can we do on just pump gas? Maybe 400whp before we need to do secondary injection. Maybe less, maybe more. We’ll find out once we have a the PRL downpipe on the VitR!

The other option is to use a race gas that reduces fuel system demand over pump gas….

 

 

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