I've seen so many posts on "running rich", and everyone says "better than lean" and "a PFC will fix it" and all that...

i guess what my question is...did the FD's come STOCK running rich?

i just had a BRAND NEW reman from Mazda...new vacuum lines, new battery, new plugs, new Koyo radiator, new plug wires, newer WORKING ECU (after the recall and it doesnt throw out CELs like my old one ), year old wire harness (not crunchy whatsoever) new turbos, and all of that (list goes on)....

im not boosting...but theres a mp/dp on there to try and lean things out...and its STILL running rich. other than the full 3" exhaust (which is bein swapped next weekend for a set of stock cats...only have 300 miles on the Reman...so im not boosting at all), engine's stock!

 

Yes, the stock ecu is very rich under boost. The A/F ratio dips below 10:1 at around 3500-4000 rpm and stays there until redline. Timing is also conservative. There is nothing wrong with running 10:1 other than it sacrifices some power.

 

im not boosting

 

^^

 

The basic FD and with your mods (non ported engine) if it ran clean or cleaner prior to the engine replacement its likely something which was installed incorrectly during the engine R & R. Sure it could be a skewed 02 sensor aside that its likely a vacuum line issue. Again there are a lot of things which factor in, but I would look at the installation of the engine, assuming it ran good prior. There are a lot of subsystems which must be just right. of course no mechanic ever screws up right or they would never admit to it. They are taught this or they learn along the way.

 

the rotary doesn't need to run pig rich all the time. It only throws fuel under boost to keep it safe.

at cruise and idle it shouldn't be clogging up the spark plugs.

boosting should help them clean off the plugs.

on the older FC's u could manually adjust A/F ratios at idle.

TPS would play a big part in this. I would check that out.

on the FD it's pretty straight forward as far as adjustments to the engine goes.

they wouldn't run pig rich all the time for emissions and gas milage reasons.

 

When you say the car is "running rich", are you just determining this from the exhaust smell?

 

well...exhaust smell, backfire (but thats expected with a 3" turboback), A/F gauge reads it, and worst of all....12mpg!
what could be wrong!?

EDIT: stock injectors are 550cc and 850cc, right? im not runnin too big of secondaries am i? i just replaced those too!!!

Im well aware that FDs run rich, and that backfire is usual....but it shouldnt be THIS rich

 

The A/F gauge is pretty useless if it's not a Wideband O2. As far as the gas mileage, 12-15 is about the norm for city driving. It will be on the low side the more you boost.

You won't do any better (without adding more highway miles) unless you get a programmable ECU and program for better fuel economy rather than power.

 

im not boosting and that was freeway miles!!! THATS why its bothering me so much...im still breaking in the engine, so i havent boosted yet at ALL

 

Who installed all this stuff for you?

 

friends shop
they did a couple guys's stuff who are on here
(dont remember their names) but they do good work from what IVE seen
any ideas what it could be? loose vacuum line, etc?

 

My advice is to go back to the shop, tell them your concerns and see what they say. IMO, not boosting but driving highway miles should do better than 12mpg.

 

^^ i know

 

If it's any consolation, my dad's brand new RX-8 with about 1500 miles is still getting only 16 mpg on the highway.

I got about 14 mpg in my RX-7 on the last tank, but it got driven pretty hard. The stock injectors are 550cc (primary) and 850cc (secondary), so it sounds like you have the right sizes.

Does it stink of fuel?

Sonny

 

I bet you cant boost at all and have a nasty leak somewhere, causing your MAP sensor to read wrong pressure and thus running pig rich.

What does your vacuum gauge say at idle ?

 

it has a pretty bad rich smell (not from engine...out the back...and its pretty bad when im just sittin at a stop light or something. im tryin not to drive it until i can figure out whats wrong.

vacuum is at 19psi
i havent TRIED boosting yet...still breakin in the engine

i looked as best i could (havent pulled the UIM yet cuz i dont have my tools with me) to see if there were any loose lines, but couldnt see any.

 

Vacuum seems fine.

I had bad fuel smell when my MAP sensor hose got disconnected, accompanied with very bad fuel smell.

But my vacuum was reading 10-11.

 

Interesting problem.. My FD is in great shape, with a reman, as yours is. I see just over EIGHT miles per gallon..

 

^^ yea im prob gettin that on city miles if not worse
need to figure out whats wrong!!
any other experts have any clues?

 

If the shop did the work, take it back to them and have them investigate if there is a problem. This way if it's something they messed up, they can't blame it on you after you tinker with the car.

If there is no warranty on their work, well, break the tools out and start looking around.

 

its pretty hard to NOT BOOST AT ALL on a stock setup. . . itll boost while driving around with the cruise control on. if you arent seeing any boost. . . you have an issue. boost leak. . . something like that.

paul

 

^^ ?.....just drive like a granny
i seriously havent been boosting....i dont think the pedal has been depressed more than halfway to the floor yet...not even merging (pissing off enough people...but hey, for a $4000 job to get a new reman in there adn all the work i had done...im not about to just throw that away)

 

dude, it seriously takes very little load to get the primary turbo goin!!!!

paul

 

^^ yea, but still...i SHOULDNT be getting 12mpg on a BRAND NEW reman w/ all the stuff i had done ON freeway with no boost (or very little to save argument)