Best economic way lean out mixture to increase power?
 

Hi,

I have been reading for a while about the mechanical aspects of my RX7 to improve it for the 2013 rally season.

I have read than other than porting, the only methods to increase power are intake (little change) exhaust (bigger upgrade in numbers) and leaning out the mixture.

I have been looking at standalone ECUs and piggy backs but they are quite pricy. That without taking into consideration dyno times....

Is there anything that can be done? Like flashing the stock ECU that would improve the mixture safely?

Thanks!

You'll need a wideband before you start fiddling with air/fuel ratios.

The 2 cheapest ways would be either to get a piggyback fuel controller, and a little more precise would be to get an Rtek, which is the stock ECU with a programmable feature. The stock ecu can not be flashed.

if you have an S4, you can always try messing with the spring tension in the AFM to lean it out. you will need a wideband though

fixed :)

There has been no evidence that the aftermarket chips do anything significant for an FC RX-7. The Rtek chips do work, but it sounds like you do not have the money for professional tuning right now. I would stick with what you have, and then get a good standalone EMS and professional tuning once you have more money. I think you will find that racing is much more expensive than you thought, and experience will give you more insight into what you really need vs. what you read on the internet. ;)

Also, you do not need a wideband for tuning, so don't waste your money on one unless your professional tuner says that you need to buy one (or two). Most real tuners will use their own equipment, which may or may not include wideband O2 sensors. My RX-7 race car was tuned by ear and by driving, and my friend's was tuned with a narrowband and by driving, and both cars worked just fine.

We just went over this. There is no chip for the ecu. The rtek mods work just fancy if you don't have the bread for stand alone. And who seriously talks someone out of buying a wideband?!?! Go tell a professional tuner you don't need a wideband! Good luck with that...

I'm pretty sure he was getting at the idea of "Why spend $400 bucks on a wideband yourself when a professional tuner has one."

Thanks all for the input.

I already had a wideband on my to do list. Well, actually two because the RB header splits both rotors all the way to the end.

But again, I was trying to find a brand that is trustworthy but cheaper that what we usually buy since we will need two... And Bosh or VW A/F sensors are expensive by themselves.


Yeah, I already experienced all that. I have already run rally sprints with NASA and Latinamerican Rally, as well as a full couple of rallycross and autocross seasons with SCCA.

The problem I have is that after adding about 200-250lbs of cage on it, and a co-driver, the car tips over 3,000lbs.

You all know that this small N/A engine has more than issues moving that mass :) So any little thing I can do to push it harder for a modest price will help. (That is why I stay away from porting or other more expensive options).


My family friend, who is helping me with my car, has built plenty of race cars along the years. Right now his family has a 240sx race car a Mazda Drift Truck with a Mustang V8 in it and a Laser AWD with more than 350whp.

(First three on the list. My RX7 is at the bottom of the list)
Bilbo Automotive

He recommended the same thing you just did Evil Aviator. To keep it the way it is until I have the money for a stand-alone or piggy back with a full tune.

I just wanted to see if there was anything more affordable, since at this rate I would do best getting a entire turbo drivetrain and swapping it to this car...

Again, Thanks! :)

By the way, AGreen.

Your signature picture is disturbing O.o

megasquirt is cheap and can be piggy backed.

True. When he says he tunes by "ear" and "driving"... Well u know... That's all I saw in that post.

if you're just doing an S-afc there isn't a huge need for a wideband, after its tuned.

fixed for you. :)

n/a cars will tell you when you have gone too far in taking fuel out. advancing the timing a few degrees will also help to a much lesser degree, unless the timing is retarded you won't gain much from adding timing beyond factory spec.

turbo cars are quite different, unless you like rebuilding engines.

widebands never hurt though, sometimes lean mixtures can resemble other issues and helps narrow down problems much quicker.

Yea, you would probably notice the car running like complete shit before you blew anything up on an NA.

Doin it in the dirt! Nice!
My vote is to isntall a SAFC (used around $100), take it to a reputable shop, have them dyno tune it, and call it a day.
The shop will have the wideband and know what they are doing. They can set the timing as well, since as the SAFC adjusts the AFM signal the ecu will adjust the timing.
About $100 for the SAFC, maybe 200-300 for the tune, and you are set. It has been an excellent solution for my setup.
Aftermarket EMS are IMHO way more $$ and effort than it's worth for mild n/a unless you are dedicated to sqeezing every last drop out of the engine.

well sometimes you can find older EMS out there for less than 5 bills and can be used for upgrades and will make more power than tweaking the stock system, which has undesired side effects.

that is the best way, i use it more just to have a butt dyno reference. its so easy to get wrapped up in some number that comes from the internet, like 13, that you totally miss the part where you really should be making max power, and not making some digital display show a specific number.

the goal of tuning is to give the engine what it wants. just picking an AF number is like you telling the engine what it wants, and this doesn't work

yep, a dyno can easily substitute a wideband for naturally aspirated cars(but can easily put you in a money hole quicker). with a turbo though you can keep making power until the engine decides it can't take it any longer and makes you walk home.

my butt dyno is skewed, anything below 250WHP all feels the same to me now unless the changes are dramatic. an easier way of calculating things for free is a timer and doing runs through a particular gear(like 3rd) from a set RPM to a set RPM(3k to 8k for example). just like running on the track the quicker your times the more you know you are going the right direction.

agreed, with a turbo we are not tuning for max power, we're tuning as rich as it can go and not misfire! big difference. actually its not a bad idea on an NA to find max power and then richen it up a tad either.

i've never done the stopwatch thing, although its probably a better way to do it than the butt dyno alone, the shape of the curve can throw off the butt dyno. a good example is a stock FD, it feels faster than it really is.

Chips are available from Re-Amemiya (Redom), PCN, Gforce, Jet, and probably a hundred other vendors.
Re-Amemiya
PCN
MAZDA RX-7 GF Peformance Chip
Import Performance - JET

A guy who knows something about engines, personal finance, and how marketing gurus lie in order to sell their product.

Yeah, I would pretty much stick to what he says. However, you are right, it never hurts to check out other sources. Dang you for posting that link! A friend of mine has been bugging me to build a rally RX-7, and the video sure looked like fun.

You also did not see the credentials of the tuners. ;)

No need for fixing when I already know what kind of engine he has. ;)

Widebands hurt wallets, and if the OP thinks that a piggyback is expensive, then he certainly doesn't need to waste money on something that is of absolutely no use to him. A wideband is of absolutely no use to the majority of the people on this forum, but somehow advertising hype has convinced them otherwise.

Leaner is better right? For power on turbo cars. Until it blows. I'm a na guy. Just checking.

I appreciate all the help and comments from everybody.

It is taking me a bit of time to answer because I go post by post reading and then googling anything I do not know (like safc and such).

First of all, I will install an A/F gauge with a good sensor before playing with the numbers (if I decide to do them myself).

I think that a full custom ECU would be too much for me to handle at the begining. Maybe using the safc would work since I just want to tone the fuel trim a bit to lean it out since everybody on these forums says that it helps a lot with the engine ouput numbers.

Could you please elavorate on those side effects? I have been looking for them but have not found any specific one.

This is one of my problems. Last time my friend took a customer car to the dyno, the bill for the customer went up to more than $1,000.

You can never tell how much they will charge you. And again, you can never tell if the guy with the dyno know what a rotary is....

I see your point here. To tell you the truth, I know what numbers are safe for an N/A engine, but I have no idea on what numbers are best for an N/A rotary engine under different loads. I was hoping to get some base numbers I could start working from.

My main idea at the moment was to get the original numbers and lean it up a bit to see how the car starts responding.

Aviator, thanks for the time you are taking to answer.


I will check those and see what do they offer.


The car is great. But every Rally RX7 I have seen are 1st gen. Mine is the only second gen I have seen.

If you can do a turbo, do a turbo. The N/A with a full cage feels heavy as hell (unless you only do suspension and other stuff and minor reinforcements like a roll bar and harness bar).


I just saw an AEM wideband gauge and sensor for $100 on craigslist (locally). But I have never trusted AEM too much.... Besides, I do not know what sensor is using.

I think the wideband would only help if I play with the fuel trim myself. Otherwise, if I get something pre-mapped or tuned, there would be no need for the sensor.

It's becoming very rare to see those who know what ratfink is :(

Rat Fink - Wikipedia, the free encyclopedia

I saw it a few times on car magazines "driving" cars. But I never knew it was a Mikey Mouse antagonist O.o