First off let me say that I am a car enthusiast and electrical engineer in my mid-thirties. I "cut my teeth" on Muscle and Imports growing up and subsequently became a huge Honda fan. I loved (still do) the B series, then K series, but have had a sad, Integra shaped hole in my heart since 2001. What a fantastic platform that was! I think the current Fit might have the right ingredients to fit, pun intended, that hole. Maybe.

The GK platform has successfully remained lightweight. It weighs less than a DC2 and about the same as an EK, but with two more doors. It isn't as pretty as either, but that's OK. Being lightweight is absolutely critical and that's part of why the GK has so much potential. Who cares if a Mustang has 412 hp when it weighs as much as a small country (to be clear, I like 412 hp, I don't like heavy cars).

The newest L15 gives us DOHC. And not only DOHC, but VTC on each cam! That's fantastic! We also have a rod/stroke ratio of 1.67. That's better than the B18C5 (1.58) and nearly as good as the B16 (1.74). This has a very important implication: the L15 should be able to rev to 9000 RPM. As long as the head can be ported to support the required CFM, cams can be designed to make power up that high. Aftermarket rods already exist. There's no reason this engine shouldn't be able to make 180+ hp naturally aspirated. It's like the B series days all over again.

The other exciting engine alternative is the turbocharged L15B7 from the new Civic. The new Civic with that engine out-accelerates the previous generation Civic Si. That engine belongs in the GK! We know the engine mounts are in the same place. We still need confirmation that the 6MT will mate with it, but that sounds more like a software issue than a hardware one. The aftermarket is already showing signs of supporting this engine which is also a good sign. If a tuner built a "kit" to enable this swap, they would come. I would come.

This is a platform for today's tuner crowd that, for the first time in a long time, I'm pretty excited about. It's been a while. I hope those younger than me recognize this. I want to applaud those already taking risks like Myxalplyx and cleangd3.

Since this is a technical forum, I'd be glad to discuss specifics to achieve either goal (i.e. NA power or Turbo swap).

 

Welcome to the board! I'm right there with you on all of your points. Sticking to N/A for now myself. Just waiting for tuning to be complete for the GK5.

I'm just kicking rocks waiting for the next item to mod. Can't move without tuning. I'm all ears if you have suggestions. The GK Engine Modfiications forum is in desperate need of some enthusiasm. Thanks!

 

It's kind of sad, but I've been trolling for nearly 10 years here.

Believe it or not, it has a lot to do with the lack of tuning options available. Hondata has had FlashPro for the GD for the longest time, but KTuner didn't show up until 2014 or so. It's a HUGE disincentive to own a car that will trim out any aftermarket add-ons. I'm really excited KTuner has stepped up! And it wasn't until last year that we had a DOHC L15. There's a lot of pieces that are finally coming together which is quite encouraging.


It is completely dependent upon when you can get a tune. If your engine looks anything like
this dyno then I'd say you have a lot more revs available, hence more power. I'd 1) spin only as high as your comfortable, and 2) spin until you stop making "more" power. It's more a function of where you land in the torque band after shifting than anything else.

I don't know what wheels/tires you have, but I've always loved the Spoon SW388s (15x6.5, 8.6 lbs) with Toyos (one of the lightest tires you can get). A lighweight flywheel and new final drive are other N/A mods that improve performance. But you have a CVT so that doesn't really apply.

As you already know, reducing the weight of rotational components pays dividends. Depending on where the moment is (the rotational equivalent to mass) can directly affect it's equivalent, translational mass. In other words, your crank pulley may be 2 lbs lighter mass wise, but it probably sheds an equivalent 30 lbs translationally. Wheels not so much. As a side note, I know that a final drive is not a weight saving measure, but it improves your power density (the amount of power you have divided by your usable top speed).

I tend to overthink things so forgive me if I start to ramble.

 

No problem! Ramble on!

My modifications have been centered around the CVT with great results.
The wheels and tires I have are here --> https://www.fitfreak.net/forums/fit-...imax-rt43.html

I have a custom Deltacam 272 grind but Ktuner is not yet comfortable with raising the rpm limit due to how the CVT may interact with the 6500rpm rev limit. I'm interested in a 6800 minimum to 7200 maximum rpm limit. I can't remember where I read about that 7200rpm limit but I thought it was on a J's Racing website through interpretation. Some info on the specs I posted are here --> https://www.fitfreak.net/forums/3rd-...deltacams.html Not too much interest though.

I believe a lightweight pulley is beneficial with acceleration. My cams dropped my 1/4 mile by 6/10ths of a second but after installing a custom NST lightweight pulley, I regained that 6/10ths that was lost. Runs were run one week apart between modifications. I posted info on the NST pulley here --> https://www.fitfreak.net/forums/3rd-...nk-pulley.html It didn't seem like there was much interest though.

Curb weight when I take the car to the strip is just under 2360lbs. I weighed it on a truck scale. This is with the rear seats removed. It's light for what it is.

I made the intake to take advantage of off idle torque and top end only (SRI but it's cold air). I based how I made this intake off testing several intakes from this thread --> https://www.fitfreak.net/forums/3rd-...take-test.html
but used information from several sites that talked about intake design with the main one being this article I purchased --> Influence of intake pipe length and diameter on the performance of a spark ignition engine

What do you have in mind? I'm very interested to see where your journey takes you.

 

I usually think in terms of manual transmissions, but the CVT offers some unique advantages. I spent some time pondering this and ran some 1st order simulations of the differences. What is really interesting is that if you want to accelerate as quickly as possible (with a CVT), you accelerate to peak HP and keep the engine operating there. The power applied over a quarter mile run looks very different than that of a 6MT:



Because of the gearing of the CVT, it takes longer to get to peak power when compared to the 6MT, but from then on it maintains it. The average power between each over a quarter mile run is about the same. I could expect that from Honda (the CVT and 6MT have the "same" performance). There's something fishy going on though. The theoretical maximum speed from gearing of the CVT is around 215 mph. Why so high? Why not make the final drive something much numerically higher and improve the power density? Here's a graph of a Fit with a CVT final drive of 9.5, compared to the stock 5.44:



This yields about a 15% improvement in average power over the quarter mile run (about 0.5 seconds improvement) with no loss in efficiency and possibly gas mileage. I haven't researched this and I suspect that there are good reasons to not do this other (than marketing), but I don't know what they are. And 9.5 is arbitrary. I think it could go as high as about 10 and keep the 118 mph top speed.

So in your case, you actually care about peak power because you can park your transmission there and not need to worry so much about the broad band performance. It would be interesting though to research CVT final drives.

I like your wheel/tire combo. Very lightweight! Another not too expensive weight reduction technique is a new battery.

Also, and I didn't mention this before, but another limiting factor in revving to the moon is the oil pump and possible cavitation at high RPMs.

 

But then there's the issue of a very un-tunable torsion beam suspension

 

If Spoon can race it, it's capable if "un-tunable." Would I like a fully independent suspension? Sure. Is it necessary? I don't think so.

 

I love the graphs you posted. Thanks for putting them up. I tried to explain to someone offline about the CVT's peak power under-the-curve over time vs a manual but they didn't quite comprehend what I was getting at. The graph nails it visually. Beautiful! How you do that btw?

BTW: There is a to get the CVT rpm to peak out much earlier than normal. I gave it a name called 'Myxal Two-Step' because I couldn't find a name for it on the net but people have been doing it for some time now. You pump the gas pedal 5-6X while accelerating, either from a dead stop or while moving. It makes the rpm jump up in stages rather than slowly climbing. I made a video to demonstrate this and it took about 4 seconds to get the rpm needle up to 6000rpm. This could in affect simulate the 9.5 gearing to reach peak rpm sooner. See this video I made to demonstrate.



You can compare that to the normal acceleration of the Honda Fit CVT. **Skip to 4:48**

You can actually play both videos a the same time (Top video at 0:05 and bottom at 4:49) to compare the acceleration.


I took your idea about gearing towards the tires and am using 185/60-14's (Instead of the 185/60-15s). This reduced the overall diameter of the wheel for better/lower gearing (Right in line with what you are talking about).

Also accelerating in 'L' gear vs 'D' holds the lower gear longer before 'shifting' up to 2nd gear. 'D' shifts to 2nd gear around 32mph or so while 'L' gear shifts to 2nd gear at 40mph. I could only see this when datalogging with the Ktuner. We discussed 'L' gear (Thanks Eigenmeat) acceleration here --> https://www.fitfreak.net/forums/3rd-...er-l-gear.html

 

My CVT will "auto shift" at 6800 (paddles). It won't bounce on the limiter. Bumping the redline up without a CVT reflash is pointless. You'll never get there.

Also, if the CVT program has its sweet spot at say, 5800 and you mod up top to add hp above that, you'll never use it because the CVT won't let you unless you use the paddles to control rpm. Straight CVT mode won't go above wherever it's programmed.

The CVT needs a reflash developed to coincide with any engine mods you make

 

Understood!

 

Excel. I model systems by trade. This is a simple approximation.

Unfortunately the 5.44 vs. 9.5 is a hardware problem entirely. The Fit cannot physically gear itself to run the engine at redline without going 30 mph (a little lower in your case). But if you could change the final drive to 9.5, then you could run the engine at redline at 17 mph. And you could still go 118 mph. That's exciting to think about.

I would like to see a software mode where you can say, "At WOT, I want you to gear yourself to put my engine at peak power, independent of how fast I'm going." No "L" drive stuff or pumping the accelerator. This Fit does this already with peak torque for maximum efficiency. Why not peak power for maximum acceleration? This could be an ECU reflash option, possibly something KTuner should look into.

 

I forgot to add that I have been trying to do the reverse until something is able to be done with a TCU ECU reflash. I am not including my camshaft modification because I had this installed in December with the expectation that the Ktuner would be ready in January sometime.

Instead of doing modifications 1st and changing the peak rpm the CVT operates, work with what you have already and try to capitalize on that.

What I mean is if your focus is on maximizing acceleration, try to modify your vehicle to maximize horsepower at the power peak. Make an intake to make more horsepower at 6500rpm. And do the same thing with the exhaust. Work with what you already have. And do any other modifications that will help accelerate these cars as quickly as possible (lighter weight and lightweight rotating mass). I even have some Japanese synthetic oil to put in for a test run when the Ktuner tuning is complete.


CarGuy, I quoted you earlier about lighter weight battery but never did make a statement on it. The battery I have been using is an Evolution Ballistic battery. It is 2-3lbs in weight vs the stock battery weight of 22lbs.
https://www.ballisticparts.com/category.php?cPath=141


Seems I've been rambling enough in this thread but this is the only forum I hang around in really. I'm really interested to see what you are up to if nothing else.

 

I went a different route and I only swapped my rear pipe with a Bisi because it's really the only place I'm willing to change. It freed up the flow slightly at the cost of more noise. This is understandable because no old lady would buy this granny car if they all were as loud as mine. The air box already is a CAI. The only way it's really going to flow any better is if you reduce its dirt filtering capacity. Honda did a pretty good job with the OE air box.

This engine has a bottle neck that is going to prove challenging to tuners: it has an integrated exhaust manifold and direct injection. if there's any risk at all with direct injection coking, leaning it out further with a reflash will intensify the issue. I'll let you all be the lab rats for this test.

I believe engine designers are deliberately making it harder for tuners to modify these things. Fuel efficiency is the priority, not HP.

I've thought about it quite a bit and the truth be told the biggest performance upgrade you can do to a Fit is select a different car. :-)

 

I hate to disappoint, but remember earlier when I said that I was a troll? I'm afraid I don't own a Honda Fit. I seriously considered getting a GD, especially for its K swap potential, but I never pulled the trigger. So I've been waiting patiently on the side line for the right Fit to come along. I think it may have just arrived. That being said, I don't buy new cars. I can't stand the depreciation drop. So I suspect in four years, I'll finally get one. Maybe sooner if my current ride dies. In the meantime I'm happy to offer my enthusiasm and technical advice. I strongly believe this is a great platform (in case I didn't make myself clear on that point earlier).

I love the battery. Great choice. Next, I would consider aluminum rotors. They don't have the thermal mass of steel, but they weigh much less. For reducing rotational mass, I'd keep the rear drums. While not so good on a race circuit, for drag racing and daily driving they're fine.

The sky is the limit for weight reduction. I used to be able to drive around in a hollowed out tin can, but I can't do that anymore. Everyone has their own threshold. I try to think of creative ways to reduce weight without me noticing. Coinciding with that, I make a list of everything that I can do to reduce weight and sort it by $/lbs. That helps me prioritize and just makes sounds financial sense.

Of the many weight reduction items to consider, take a look at MR10 Lexan for some of the windows. It's lighter than glass and also scratch resistant (something Lexan is prone to do). Lightweight racing seats are good because you get the added benefit of a really comfortable, sporty seat to sit in every time you go for a drive. I spent a little time researching reducing the size of the A/C system (say, from a 1st gen Insight) and reducing the thermal load by applying clear, UV film on all the windows. This moderately expensive process can save around 12 lbs, but I'll have to find my original analysis on that. And yes, I'm past the age where I can get by without A/C. I'm starting to feel old. Carbon fiber is sweet, but it almost always lands at the end of my sorted list. It's just too expensive for such a small, incremental reduction in mass.

On a completely different note, I may reach out to LHT Performance and suggest the L15B7 swap to them. They're just the kind of shop that would do something like this. If you are unaware, they swapped a K20A into a 1st gen Insight with full A/C. The car runs a mid 12 1/4 mile and gets 45 mpg. If someone like LHT finds the swap very doable, then it will garner a lot of attention for new tuners. Since I'm so conservative, that's exactly that kind of path I want to follow: tried and true.

 

I've been thinking about the integrated exhaust manifold too. We should get a competent engine builder (like Endyn) to work their magic on a stock head and see what can be done. This sets the real potential for the engine. As a crazy outside-of-the-box idea, we should persuade a Mechanical Engineering masters student to design a brand new, performance oriented head that we can have 3-D printed.

Don't give up yet! Once Myxalplyx gets his tune and recovers his lost 0.5 sec from the cam swap (and probably more), he'll have successfully tuned a 16.2s car into a something that runs high 14s. And that's without head work or boost. I think this is great.

 

I was gonna PM this Cojaro fella but he hasn't been on in some 6 years or so.
https://www.fitfreak.net/forums/off-...-up-lines.html




We may potentially already be there with someone that has a manual transmission. I was running 17.1-17.2 @ 81-82mph fully stock vs a manual running at 16.2@86mph. With a muffler change (Only), intake and some weight loss is how I manage a 15.2@90mph. Nothing extreme! I'm sure a manual with the same modifications and maybe a tune could tick off a very low 15 and possibly a high 14. Unless I'm giving a manual tranny too much credit. It feels like people are still being affected by the performance of the previous generation Fits. This generation Fit is performing like an HKS turbo'd Fit even while it's stock and suffocating N/A.


I have been up for a better part of last night reading up on that LHT K-Sight. I never heard or seen that vehicle. At 1880lbs and 450whp (Potentially 500+ engine) AND AWD is INSANE. It had a full interior and fully functioning A/C AND was tuned to get 48mpg. THIS is my dream car. That's a power-to-weight ratio of a Bugatti. All I was wanting to know is how much it would cost to purchase one. I'd need nothing else.

 

Anybody thats played with drag racing snowmobiles or Polaris quads knows why you don't pull that CVT gearing in too early.. The CVT is a torque multiplier if you move the shivs later,, the torque hits harder,,, exponentially harder.. IE my Polaris will literally do an uncontrolled wheelie with any throttle at all if I hold the shivs out too late with the wrong weights. I foresee twisted drive shafts when folks learn how to tune the CVT controller.. Or amazing throttle oversteer.. Or just tires going up in smoke ..

 

I'd love to see a Fit do a wheelie. But I don't think that's going to happen any time soon.

I don't know much about CVT gearing in ATVs or snowmobiles, but the Fit will never have outrageous torque abilities without a mechanical change (i.e. a new final drive).

 

Please let us know if anything comes of this! Loving the exchange here on this thread and I'm also really anxious to hear these guys' take on the GK's potential with its current motor, or what they have to say about a L15B7.

Cheers

 

Sheesh!

http://www.apexatv.com/techsupport/apexclutch.pdf