Hondata tuning for 2005 Civic Si - worth it?

[bartine]

I have a 2005 Si.

I have a really good performance shop right down the road.

I went in today and asked about modding the car for better fuel economy and the guy knew exactly what I was talking about.

They suggested doing the Hondata K-series ECU refresh with economy settings.

The one time flash would run $295, which isn't too bad at all if it works, plus around $150 to install a cold air intake. Right now I average on my longer trips around 29 Mpg driving between 65 and 80.

Has anyone else out there done this mod? Anyone have any actual results from tuning their EP3 Si?

Thanks!

Ben

[some_other_dave]

Offhand, I'd say that it's not worth it.

In general, FE mods just from changing the "programming" in your car's computer will not be that large. It needs to run right around a specific air-to-fuel ratio (14.7:1) to keep the catalytic converter working, and the ECU in the car is set up to do just that. You can potentially cut down on some things (in general, that cuts into whatever "safety margins" the factory built in) but the gains will likely be small.

The cold-air intake will not help your FE. In fact, there's a decent chance it will reduce it! Most engines are more efficient when they are pulling in warm air, though there is definitely a point at which it gets "too warm". In the winter, it can be better to pull air from right next to the exhaust manifold!! Search "warm air intake" on here for examples and discussions of why.

I'm thinking that the pay-back on the $300 re-flash will be on the order of many years, unless fuel prices go through the roof. If they do, and if it really does improve your mileage, it might pay itself back eventually.

How you drive has a larger effect on your mileage than computer chips or air intakes. Read up on "eco-driving" or "hypermiling" to see the hows and whys. I've gone from 30 MPG to 47-48 MPG in my CRX Si, which is more than you'll see from any mod.

-soD

[cycleguy]

That is actually a pretty good price for the K-Series re-flash. Back when I bought my 2002 Civic Si the cheapest option was like $800 and they didn't have any real good maps for it so you had to figure it out on your own. On one side, I would say 'go for it' but then again I think it is funny to de-tune a car designed to be sporty. I got about 30mpg in my Civic when I drove it (right now it is in the garage getting a very slow valve adjustment as I have time available). I imagine you would have to pay for another re-flash if you were unhappy with the performance of the car so maybe you should either buy the full K-PRO setup or just leave the computer alone.

[cmj]

I've successfully and SAFELY tuned my vehicle to ~9mpg better simply by getting rid of excess fuel under 20% load. As far as catalytic converters, I dont know. An "economy" flash isn't necessary going to be specific to your vehicle tho. If you are interested in tuning as a hobby, buy a hondata setup, get a wideband, and READ READ READ, if you're interested in picking up 2-3mpg on a lightened generalized fuel map, go for it. If 2-3 mpg isn't worth 300 to you, I would just work on the driver mod. I picked up about 6mpg on this mod alone.

[sarguy01]

bartine, is this shop going to use a canned tune or are they actually going to put your car on a dyno and then tune it?

If they aren't going to dyno it, I would not bother. I think you could see gains in mpg, but only if your car was dyno'd. Every car is different even though they could be the same exact model. Canned tunes are usually a good starting point.

Like mentioned, the gain could be really small and not worth it. If they dyno tune it, the price may increase.

Like cmj wrote, mod the driver first.

[bartine]

And by "Mod the driver" - we are talking about me - correct?

I drive a bit of miles for work - business trips from Atlanta to Washington DC.

I have read that the K20A3 can be tuned for high efficiency, but haven't found a lot of details yet.

I'm hoping that others who have had a K20A3 engine can chime in.

[sarguy01]

Originally Posted by bartine

And by "Mod the driver" - we are talking about me - correct?

I drive a bit of miles for work - business trips from Atlanta to Washington DC.

I have read that the K20A3 can be tuned for high efficiency, but haven't found a lot of details yet.

I'm hoping that others who have had a K20A3 engine can chime in.

You got it!

I would suggest a Scangauge II. I got one on Ebay for 130$. I have used it on 3 cars now and it has paid for itself. It will be like a little girlfriend/(boyfriend? - trying to be politically correct...) that will nag you to keep your foot off of the right pedal, among other things.

I would still put the tune off for a while.

[user removed]

Bartine, for that kind of driving, your greatest disadvantage is the overall final drive ratio of your performance Honda.

Both my old VX (now sold) and my current 2008 Altima Coupe ran Fairly low RPM at higher sustained speeds.

when you can go 72 MPH at 22-2400 RPM the engine has a fairly low but decent load and efficiency is greater.

Most of the performance Hondas have gearing that would have the RPM ranging from 3200-3600 and even higher at speeds above 70 MPH, which is less load and lower efficiency.

My old 76 280Z, built for performance had a .75 5th gear overdrive, and originally had a 3.54 rear axle ratio. It worked out to about 85 MPH, at 3000 RPM in high gear with a 5 speed out of an 82 ZX. I later changed it to a 3.90 which helped performance but cost me some MPG, which at that time (15 years ago) was not the priority it is today.

It was a best of both worlds compromise, with 30-60-90-120 max speeds in 1-4th gears, while 5th added 33% to the 4th gear top speed. In reality it probably would not go any faster in 5th than in 4th, but the low RPM high speed cruising capability was good for close to 30 MPG as long as you kept the speeds close to the 65 limit in Va.

regards
Mech

[NachtRitter]

Definitely agree with SoD and sarguy... for less than the cold air intake, get a ScanGauge II and use that to improve your eco-driving skills... it's incredible the difference it makes to get that instant feedback!!