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Ecky 06-24-2018 08:16 AM

Honda Insight w/Acura TSX engine - Ecomodding
Lately I'm seriously considering doing a K-series conversion to my Insight. My logic: at some point the IMA battery will need to be replaced. If I lived somewhere more flat it wouldn't be a big deal to just bypass it, but Vermont's mountains make the car a bear to drive without assist. I'm approaching 250k miles on the engine with zero problems so far, and have no idea how many miles I can put on it. My transmission needs a "tabectomy", it grinds when downshifting into first and second. Undoubtedly the least expensive option is to just keep it running with factory parts, but I can't help but dream and it might be best to do this while the components I'm taking out still have value.

My ideal swap would be the drivetrain from one of Honda's more recent hybrids. However, nobody knows how to do this. :rolleyes:

Next best would be a modern L15B out of the 2015+ Fit. This is the same motor as is in the 1.5T Civic, just without the turbo. These have an offset crank and a lot of low friction technologies. Despite the gearing they're pretty well tuned for economy. I could re-use the really tall ~3.2 final drive out of my Insight's transmission, or the entire transmission, since the Insight's engine is secretly an "L" engine too. Unfortunately the L motors are quite tall, the intake manifold tilts upward and sits on top of the engine (making it even taller!) and there are virtually no aftermarket options. So, I'm probably going K as I won't be able to make it fit under the hood.

My idea: Obtain one of the higher compression "K" engines with integrated exhaust manifolds which nobody wants. The king of K motors in my opinion is the K24W7 out of the 2015+ Acura TLX, with a mouth-watering 11.7:1 compression ratio and 182 ft*lbs of torque at 3900rpm, but the K24W out of the recent Accord and CR-V (at "only" 11.1:1) can run on 87 so that would be a decent option too.

Undecided on a 5 vs 6 speed. Weight and size may dictate that. However, whichever way I go, I'll likely have a custom ~3.4 final drive made for it, which would bring 65mph cruising RPM down to ~2200 with the Insight's stock tire size, lower if I go a hair bigger.

A shop in Florida has successfully tuned the older K20A2 motors to run at 19:1 AFR at part throttle, and reports in excess of 50mpg highway in the Insight body.


Well, The K-Sight is a pretty nice car and we're not really drag racing it. But we have logged a couple of low 3 second 0-60 times using the Hondata K-Pro.

We have took it to some local shows as well as SEMA and have managed 57mpg without any issues.
^ Mind you their low-3 second 0-60 is with a turbo, which I would not have.


I have my K24 insight running at this point and have taken it on longer trips. The best I have gotten on a base map is 49MPG at an honest 85MPH for a 5-hour trip. This is with a custom final drive and the longest 6th gear available which drastically improves cruising rpm from 3700 to 2500. It was also on snow tires, haha. I plan to lean burn tune it soon to see if I can improve from there.
49mpg at 85mph is actually quite close to what the Insight's stock engine gets, probably because it's running outside of peak BSFC at that speed.


Dry weight of the car is ~1850lbs with A/C.
Insight engine - 128lbs
IMA battery - 95lbs
Insight manual transmission - 56lbs
MDM + DC-DC - 20lbs? estimated
Total: ~300lbs
57:43 weight distribution

K-series 6 speed weight: 89lbs
K-series 5 speed weight: 87lbs
K24 engine - 283lbs
K20 engine - 275lbs
Total: 360-375lbs, plus maybe a bit more in brackets and alternator

I'd be adding ~100lbs to the car. More importantly, this will throw off the weight distribution, adding ~200lbs to the front and subtracting around 120lbs from the rear. Ideally I'd re-use the IMA power cables and migrate the 12v battery to the back of the car, maybe switch to an AGM battery for safety (and efficiency) reasons.

I've exchanged a few emails with a shop in NYC with a lot of experience with K swaps. We'll see where this goes.

California98Civic 06-24-2018 10:55 AM

Sounds great. You could develop the kind of project pgfpro had here on EM. Before his Talon, which was amazing, he had tuned a three-stage Civic for fuel economy in a specific RPM range and throttle position (IIRC) and power under some other conditions.

The weight distribution problem sounds kinda, well, dangerous maybe. Traction on the power wheels would be fine, but how would braking and especially cornering be affected?

The power/weight ratio, tho! Fun.

We could think of it as an ecomodded K series, lol.

Ecky 06-24-2018 11:06 AM

I've made a mistake, the weight I listed was for engine and transmission. Edited post. ;)

California98Civic 06-24-2018 11:33 AM


Originally Posted by Ecky (Post 572761)
I've made a mistake, the weight I listed was for engine and transmission. Edited post. ;)

So migrate the battery to the trunk and get a big ass and cheap lead acid one that you plug it at night, running the car mostly without the alternator like I do.Throw like 80-100 amp hours back there at maybe 70-80 lbs. That's 20 lbs reduced from the front and 80 added to the back. ??

Maybe add rear disc brakes since you have so much more power? That also will put a little more weight in the back.

You'd still have a really great weight/power ratio and somewhat more even weight distribution.

MetroMPG 06-24-2018 11:34 AM

If you could gear down the engine for top-gear cruising, sounds like it'd still easily beat Geo Metro MPG on the highway. Neat trick.

Of course you'd throw some of the tank average away having fun in the lower gears. Compromises, compromises!

Ecky 06-25-2018 12:09 PM


Originally Posted by California98Civic (Post 572759)
We could think of it as an ecomodded K series, lol.

Yeah I wonder if I should call this a "TSX heart with an Insight wrapped around it", or a an Insight with a TSX guts. :D

Anyway will update as I go.

After thinking on it, aftermarket fuel management and then getting a good lean burn tune on an engine with several cam profiles for both intake and exhaust plus variable timing might be time consuming (read=expensive) because of all of the factors involved. I might just go with a factory ECU and give it reeeeaaaally long legs to start with. Swapping the ECU later doesn't require I put it up on a lift.

Ecky 06-27-2018 07:55 AM

I'm guessing few to none here know much about different versions of the Honda K20 and K24, but I figure I'll throw this out there anyway, in case anyone has any useful feedback:

My understanding:

+ high revving, slightly lighter, shorter engine (fits better), barrels of fun, short runners (fits better), well understood and relatively easy
- expensive, less torque, probably worse gas mileage (all else equal)

K24A2 (pre-2006)
+lots of torque, probably better gas mileage, less expensive, well understood and relatively easy
-lower rev limit (still plenty), heavier, probably hard to find one without a lot of miles, long runners (might need to cut radiator support)

K24Z3/Z7 (~2006-2012)
+ probably cheapest of all since nobody wants integrated header, easy to find low mile, wider powerband
- Aftermarket engine management might be absolutely necessary, since it's DBW. Adds cost overall, unless I go with an aftermarket ECU to begin with

K24W/V7/W7 (2013+)
+ Most torque of any K engine by a lot, probably best fuel economy, easy to find cheap low mile engines, crazy high compression ratio
- I have no idea about DI, probably would need entirely new fuel system? Probably not a well understood swap even if it can be done, so $$$$$

Not currently considering the lower revving, lower compression ~160HP K20's and K24's.

Some questions I have rolling around in my noodler:

Are the mounts the same on the newer W and V Earth Dreams motors? Should I rule those out entirely because of direct injection? Has this ever been retrofitted before? This is probably too ambitious, but I'm curious about them at the very least.

What are the major hurdles of keeping the factory ECU to save money? I'm willing to bet I can get away with this with the early K20A/K24A, but I don't know if it would be possible on the newer K24Z, due to drive by wire.

Are there any engine and transmission mount differences for the various K engines and transmissions? Are they all interchangeable? Does any transmission mount to any engine?

Am I correct in thinking the K24A's have VTEC on the exhaust cam, whereas the Z's do not?

I'm undecided on whether or not to go with aftermarket engine management, because I don't know where I'd find a tuner who knows how to tune for lean burn and fuel economy. On an engine with VTEC on both intake and exhaust, AND variable timing, AND variable length intake runners, trying to tune it myself sounds... difficult.

ksa8907 06-27-2018 08:42 AM

As for direct injection, from what i have seen, the high pressure pump is mechanically driven from a cam shaft. It may not be difficult at all if it is stock parts on the engine/ecu.

Baltothewolf 06-27-2018 12:59 PM

My question is, do you have 5-10,000$? Everyone says it's cheap if you DIY, but in the long run they just lost count of how much money they really spent, due to the fact the projects take so long. That or they give up.

I'm not trying to discourage you from doing it. Just being real.

Also, get a K20A motor. 8600rpm redline. Yummy.

Whatever K motor you go with(unless you get one with a redline above 7250). Use the accord manual transmission. It's got tall gearing and it shifts so, so SMOOTH. If you get one that redlines at 8400-8600, just go with a shorter geared trans (about 3500rpm at 75). Otherwise it will be an absolute dog off the line because those engines make no torque below 2000rpm.

I just read the questions about the DI motors. Unless you have experience and training I would not recommend you even attempt it. You are talking about 5-900PSI pressurized fuel lines. Not worth the risk.

Ecky 06-27-2018 01:05 PM

Yeah, I set aside $10,000 from my checking account to cover this. Hopefully it comes out to less, but I'm prepared for it to go a bit over.

I figure if I can get a low mile engine (let's say 40k) it's a lot less expensive than a car with that many miles.

Currently looking at auctions for things like TSX or newer Si (K24) which have been in collisions. K24's, even the nicer ones, seem a fraction of the price and are much easier to find with low miles.

Definitely planning on a custom 3.4 FD, even if it's $$$$. Even with that crazy tall gearing, it's still going to be geared shorter than the stock 1.0L.

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