rootsgroup

Been reading for quite sometime, haven't searched, but what would be the opinion, or experience. Would using standalone be justified from a mileage standpoint as the major advantage?

Sure, I wouldn't ignore the performance increase, it's just that everything I read on here is telling me that NA's run "pig rich" and I'm curious, could an aftermarket fuel management system make a difference mileage wise? Worth the outlay?

diabolical1

iTrader: (3)

that's probably the best attribute of a standalone - it's versatility. to a certain extent, you can tune for whatever you wish, tailoring fuel and ignition for YOU and your wishes. whether or not it's worth ultimately lays on your doorstep, but now that i've crossed over to the land of aftermarket EMS, i'm not going back to stock.

Evil Aviator

My friend got over 30mpg highway with his 86 Sport fitted with a Wolf EMS, K&N filter, and Bonez catback exhaust. He drives about 80mph on the highway, but he is also an excellent tuner with many years of experience, so I am not sure if the average person on this forum would be able to achieve those results.

Unfortunately, the math doesn't show a standalone EMS as much of a benefit for economy alone:

Average mileage = 15,000 mi/yr
Stock EMS = 15,000 mi / 24mpg = 625 gal/yr * $1.75/gal = $1,093.75 /yr
Standalone EMS = 15,000 mi / 30mpg = 500 gal/yr * $1.75/gal = $875 /yr
Savings = $1093.75 - $875 = $218.75/yr

Typical budget standalone EMS = $1,000 to $1,800, plus about $500 for tuning.

Time to recover cost of standalone EMS = 7 to 11 years.

peejay

You can also get 30mpg with a stock FC and an exhaust.

I haven't seen better fuel economy with a standalone, but I don't exactly have a control set

IMO standalones are hampered by the fact that few can control EGR, which is a wonderful thing to have if you want good fuel economy.

rootsgroup

Thanks guys, for your replies. My 87 GXL would get 21.5 on my to work and back trips, which is 36mi one-way. 60% interstate, 40% county road stop and go.

I did coax 26 out of it on a 400 mi total interstate trip though, so I can envision the 30 deal with some basic tricks w/o resorting to the standalone setup.

I didn't think of how egr plays into the deceleration process, so yea, I see your point there, too.

My starting thought on running one was to clean up the a/f ratio across the board, which is the intent to increase performance. So how could it not help mileage as well? But is it worth the outlay?

I bought my 7 with the intent to convert it to Honda power to just use it as a hi mileage fun to drive car. But in the 2 weeks I was able to drive it before I tossed an apex seal, I also tossed the Honda idea. Rotaries are just too cool.

Would I be equally sold on the standalone installation once it was tuned? Ask you guys who have 'em I guess.

It's up on stands now waiting on a multitude of fixes, so it's given me time to think myself into a quandary, I suppose.

That's pretty much my deal, so you guys chime in if you like-

Evil Aviator

I much prefer the engine tuned with a standalone EMS from a performance aspect. However, the downsides of the standalone EMS are the initial expense, initial labor, inability or pain in the rear to run secondary functions like knock control, air conditioning idle, etc., and unlike the stock system it needs to be retuned as the engine wears.

If your current system is running well, I would only recommend converting to a standalone EMS if you really want to tweak the performance. Otherwise, it is a lot easier to just leave it stock. I do not think it is worth the time and money if your only focus is gas mileage. In my particular case, I have a 'performance' RX-7 with a standalone EMS and a ton of performance parts (over $35K invested so far), and I also have a 'cruiser' RX-7 with the stock system and very few performance parts (under $2,000 invested so far).

I have never seen a stock FC with only aftermarket exhaust get over 30mpg at 80mph. Which exhaust did you use?

peejay

Not my car - I don't fit in FCs and they aren't my style. I don't recall his username on this forum, but he bought a Series 5 in Dayton and drove back up to Cleveland. I forget what exhaust he had, but it was not quiet... might have been a "catback delete" for all I know!

I don't know how fast he was going - probably 65mph or therebouts, given that they were travelling in convoy and the speed limit in Ohio is 65mph for the most part. I have averaged close-ish to 80mph on that trip, but fuel economy in my normally 35-40mpg VW drops down to below 30 when I do that My record is 225mi in 2:57 and I do not intend on trying to better it! It requires lots of time on the car's top speed interspered with endless minutes stuck behind some yahoo from Indiana driving 55 in the left lane...

But anyway he did something like 31mpg on the trip...

The stock ECU runs stoich *under 3800rpm*. Keep it under 3800 and there is little benefit to a standalone re: economy.

EGR is not a benefit under decel, it's a benefit under *cruise*.

philiptompkins

iTrader: (4)

Can someone explain how EGR can help fuel econ? I thought it was only an emissions thing.

peejay

It takes energy to create a vacuum in the intake manifold. EGR introduces an inert substance in the intake, displacing some of the air, reducing vacuum. The throttle needs to be opened more to compensate for the lower pressure drop into the intake manifold, reducing vacuum further still.

Engines are most efficient at WOT, EGR helps you get closer to WOT while maintaining efficient ignition timing and fuelling. Allows even more ignition timing, actually, before running into detonation or high combustion temps, which is where the emissions benefit comes into play.

It's not evil, although it can be finicky to set up if you don't have an OEM's resources.


My late 80's Nissan saw a roughly 12% increase in MPG if the EGR solenoid was actually plugged in.

Evil Aviator

http://autospeed.com/cms/A_110577/ar...popularArticle
http://www.autospeed.com/cms/A_110581/article.html

Also, if you search the internet for "SwRI HEDGE" you can see many new developments in this and other similar areas.

What? In that case I'm not interested! Hehehe.

lupin

iTrader: (3)

With my e8 I'm gettin about 18 in the city. But then again I'm don't have a lot of exp and i'm still tuning her slowly but I am enjoying every minute of it.

JFixer

The fact that the stock computer runs at stoich is a limiting factor in fuel milage. Stoich is just were you have the best emissions. You can run leaner than that on the highway and increase milage you just also increase NOx emissions. Also is very easy the make a purely mechanical vacuum controled EGR system if need be.
Joe