Rarity- Accord V6 6MT Hypermile/Build Thread

[serialk11r]

Forgive me if you mentioned this already, I haven't gone through this thread in a while, have you thought about ECU tuning? You're lucky you have a Honda (can use Hondata Flashpro), it's not like Toyota where you need to use piggyback or a crappy standalone like an Apexi PFC.

Right now there's a chance you're sending a little extra fuel out the tailpipe when you step harder on the throttle (from what I can find on Google images, your engine seems to activate open loop enrichment at low speeds). If you get a flash you could get rid of that. You can also add enrichment and then use a narrowband emulator to run lean and get a 5-10% boost in fuel economy. On these bigger engines it should really help a lot.

[Daschicken]

Originally Posted by serialk11r

Forgive me if you mentioned this already, I haven't gone through this thread in a while, have you thought about ECU tuning? You're lucky you have a Honda (can use Hondata Flashpro), it's not like Toyota where you need to use piggyback or a crappy standalone like an Apexi PFC.

Right now there's a chance you're sending a little extra fuel out the tailpipe when you step harder on the throttle (from what I can find on Google images, your engine seems to activate open loop enrichment at low speeds). If you get a flash you could get rid of that. You can also add enrichment and then use a narrowband emulator to run lean and get a 5-10% boost in fuel economy. On these bigger engines it should really help a lot.

Nope, haven't mentioned tuning previously. I know there is plenty of ECU support for K engines, haven't heard much of tuning J engines. I'll have to look it up when I have time, right now aeromods take priority because my commute is 90% highway, and I have a family road trip coming up. I used the scangauge to see when open loop occurs on my old 4 cylinder accord and it was only during warmup and above 90% load I think, have not set the loop gauge to monitor the V6 yet. I'll try it out. As for running lean...Ehh...I would rather add ignition advance before trying to run lean. I don't like the idea of increased NOx emissions either, but I would be all for removing fuel enrichment below 80% load.

[serialk11r]

Originally Posted by Daschicken

As for running lean...Ehh...I would rather add ignition advance before trying to run lean. I don't like the idea of increased NOx emissions either, but I would be all for removing fuel enrichment below 80% load.

The thing is, on the highway your engine is at low load and that's really when lean burn will help a lot. The other situation is idling, but a real hypermiler turns off the engine :P

The issue with enrichment is that the throttle is configured so that you get a lot more load with a small press of the pedal at low rpm, and you could be inadvertently going into enrichment. It took me a while to discover that despite my best efforts I was still hitting enrichment at 80% load. I have since calculated what the mpg meter should say at the highest load it won't go rich at, and am retraining my foot to step to that way.

Increasing ignition advance isn't going to do jack, but you're right, NOx will increase. If you don't like that, you can still benefit from tuning by increasing EGR or at least knowing about the EGR valve. My wild guess is that your EGR flow rate is knock limited so you can consider modding the valve or something and adding some cooling to it.

My view on NOx is that a large diesel garbage truck or semi or street cleaner is causing way more health damage than a bunch of lean burn passenger cars. If you tune the engine to run a bit richer at high load while maintaining EGR at low load, again, miniscule NOx compared to a diesel truck.

[Daschicken]

Originally Posted by serialk11r

The thing is, on the highway your engine is at low load and that's really when lean burn will help a lot. The other situation is idling, but a real hypermiler turns off the engine :P

The issue with enrichment is that the throttle is configured so that you get a lot more load with a small press of the pedal at low rpm, and you could be inadvertently going into enrichment. It took me a while to discover that despite my best efforts I was still hitting enrichment at 80% load. I have since calculated what the mpg meter should say at the highest load it won't go rich at, and am retraining my foot to step to that way.

Increasing ignition advance isn't going to do jack, but you're right, NOx will increase. If you don't like that, you can still benefit from tuning by increasing EGR or at least knowing about the EGR valve. My wild guess is that your EGR flow rate is knock limited so you can consider modding the valve or something and adding some cooling to it.

My view on NOx is that a large diesel garbage truck or semi or street cleaner is causing way more health damage than a bunch of lean burn passenger cars. If you tune the engine to run a bit richer at high load while maintaining EGR at low load, again, miniscule NOx compared to a diesel truck.

I'm new to the whole tuning thing, previously I have worked on carbs, so I have an idea what is rich and what is lean, but my knowledge ends there. I have no experience messing with fuel injection (because it WORKS!), so forgive my ignorance. I looked at the price of a tuner, and it's $900. No thanks, too pricey.

I went out and tested what load open loop happens at, it is at 93% load, damn near full throttle. I also looked to see how long it stayed in open loop after restarting the engine, its about 8 seconds.

I also got a new best trip! 42.3 MPG! It was almost 43 mpg, but a stupid stoplight was tripped by a truck, and I had to stop. Also installed a new undertray panel, which may have helped, but I am almost certain the extra MPG was due to the fact that the car was already warmed up.

Will post about the new undertray panel and my plans after I get some sleep.

[Daschicken]

More progress on the underside today, 2 more panels added on.

This area of the underside already had some aerodynamic panels on it, but it still had plenty of room for improvement.


New rear wheel spats! The new undertray panels presented a flat surface for me to mount spats to. My previous spats were pretty bad, Never tried them out because they didn't look beneficial. Mounting the spats required machining L brackets, including drilling new holes and cutting off excess material. Just eyeballing them, I think the spats are mounted too far away from the wheel, looks like they should be an inch closer.

I have driven the car with one panel on it, and no rear wheel spats, haven't noticed a clear improvement. With two panels and the rear wheel spats in place I expect to notice an improvement on my next drive.

[Daschicken]

With the two new panels and rear tire spats there was a definite improvement in coasting. My trip to school yielded 41.2 mpg, it could have been almost 43 without traffic. I had one big slowdown moment, from 65 down to 20 mph, other than that, I drove a little faster than usual.

I will go ahead and move the tire spats back a little bit, and maybe make some side deflectors for the rear wheels as well. I think these new mods will secure 40+ mpg on my commute regularly!

[Joggernot]

Hey, I just re-read your first post. Don't get discouraged; we're following silently! You've done great so far. I'm envious of the 6MT you found. I was told they didn't make that combination when I bought mine.

[Daschicken]

Originally Posted by Joggernot

Hey, I just re-read your first post. Don't get discouraged; we're following silently! You've done great so far. I'm envious of the 6MT you found. I was told they didn't make that combination when I bought mine.

Good to hear.

It sure took a while for me to find mine. Accords didn't get a V6 6 speed manual till 2003, and that was for coupes only. V6 6 speed sedans only existed in 2006 and 2007, newer v6 6 speeds are only for coupes. If you really want a 6mt, then you could always do this: How To Make The Honda Accord V6 All Kinds Of Awesome

[Joggernot]

Originally Posted by Daschicken

Good to hear.

It sure took a while for me to find mine. Accords didn't get a V6 6 speed manual till 2003, and that was for coupes only. V6 6 speed sedans only existed in 2006 and 2007, newer v6 6 speeds are only for coupes. If you really want a 6mt, then you could always do this: How To Make The Honda Accord V6 All Kinds Of Awesome

I have never seen one, but am about to replace this 2000 V6 EX-L that I have. It's gone through three transmissions and 275k miles. The first transmission was after two weeks, and on warranty recall because it was one of the transmissions they forgot to put a necessary part into. Thus, it didn't sound good when shifting.

Thanks for the link!

[Daschicken]

Another new best trip, only things changed were a slight modification to the tire spats, and more likely the source of improvement, the car being warmed up before from a short trip. The short trip had the same route as my normal commute, so it was just as if I had reset the current trip once the car got warmed up. But since I consider both trips as legitimate trips, I'm going to consider this valid. More stoplights than usual, and one slowdown moment during the trip. I saw as high as 44.9 mpg right before the slowdown.


Including both trips, the avg was 40.7, but i'm going to enjoy my new highest trip mpg.

I moved the spats back about half an inch, so they matched up to the rear wheel well better.
Before
After