Toxindude

I am a newb to this site but it seemed the best place to ask a question about my RX-7 . So I have an 86 RX-7 I have been told latley that the exhaust smells rich . The O2 sensor in seized in the manifold and the wire is busted to it so that sucks and I know you may smell rich if its not hooked up . Somtimes the car seems to loose RPMS in second and third gear around 4 grand. I have searched the site already but didnt find the answer I was looking for .

Here are some of the things I have done to it engine wise.

New TPS, New K&N cold air kit , New upgraded Higher pressure fuel pump, New Venom 880cc fuel injectors,

Do I need to upgraged my exhaust system or am I not getting enough spark I dunno whats the deal .

Thank you

13b4me

WHY on earth are you running an upgraded fuel pump/injectors on an N/A model? You should be trying to remove fuel, not add it! And you HAVE to get a new 02 sensor with pigtail, or you are in for some serious issues.

Toxindude

Well it wasn't getting enough fuel the filter was dirty the fuel pump was bad the old injectors leaked causing it o flood out everytime I started it . Ever since I replaced that stuff its been running way better .

What would you recommend I do any suggestions other than the O2 sensor that thing is seized in the manifold .

13b4me

You definately gotta lose the 880's and fuel pump. Get a stock fuel pump from the forums, as well as the appropriate 460cc low impedance injectors. You can pick the pumps up for around $20-25, and the injectors can be found dirt cheap as well. You can also send them off to a company like Witch Hunter Performance to be cleaned. Costs about $35 to have them cleaned, and flowtested. Replace the fuel filter. Get someone to drill the 02 sensor out, and retap the threads, or simply buy another used manifold. The 02 sensor is a must have item, and the fuel upgrades are a must not have item. If ya get my drift.

NZConvertible

Completely untrue.

That's you're problem; you're overfuelling the engine, and the rich mixtures will be killing power, economy and emissions, and casuing the smell. Take both of those out and replace when with stock items. You'll have more power and use less fuel as a result.

If you haven't even upgraded the exhaust, you can't be making much more than stock power, making your fuel mods even more ridiculous. And no upgrading the exhaust won't help at all.

"Better" is a relative term. It'll run much better again with the right injectors and pump. It wasn't getting enough fuel because the original stuff was bad, not because it wasn't big enough.

Absolutely wrong. Other than slightly increased average fuel consumption and probably failling an emissions inspection, there are no problems at all with running without an O2 sensor.

Toxindude

Why is it bad to have bigger injectors and fuel pump for more fuel . Sorry I am kinda new to the rotary still .

Toxindude

Okay ignore my last question

Toxindude

How am I supposed to increase my power ?

NZConvertible

Because the stock EFI system cannot compensate for the changes, so the engine will simply run very rich. This has nothing to do with the rotary, it applies to any engine.

By increasing airflow, i.e. intake, exhaust, porting, etc. Up to certain point the EFI system will easily compensate for increased airflow, and NA's don't reach that limit without major mods.

Toxindude

Okay so I need to decrease the amount of fuel I am putting into the engine go back down to 460cc injectors and increase my airflow

Hecubus84

iTrader: (1)

First off, rotary engines run rich by nature. That said, replacing your o2 sensor, exhaust gaskets, and possibly your cat (the honeycomb shoud be intact) would help the rich exhaust smell. The rpm drop you are experiencing is commonly known as the 3800 rpm hesitation, a simple forum search will yield information on how to quell that problem. A new tps isn't necessarily a bad idea but I would definitely check that your current one is working properly.

There is a excellent write up on how to tune the tps here.

As far as the quest for more power I would start with a full exhaust from a good manufacturer like racing beat. The stock fuel system is perfectly capable of handling nearly any bolt on modification you can shake a stick at.

All newbies must throughly read the faq and heavily research any questions before posting them on the forums. If this warning is not heeded, the OP will face extreme beratement at the hands of the senior forum members. This is a friendly warning.

My advice for you is to sit down, invest some time, and learn as much as you can about your car, there is a ridiculous amount of free information about these cars floating around on the internets - all you need to do is find it.

-Hec

Toxindude

Noted

NZConvertible

If by "turbo it out" you mean add a turbo, yes that would do it, but also the more extreme types of engine porting (bridge, J and peripheral ports) are beyond the stock system's abilities.

Replacing the O2 sensor won't do anything for exhaust smell, because the only time the sensor is only used duing loight-load cruising. Unless you're drviing along with your head hanging out the rear hatch, you ain't smelling the exhaust no matter how bad it is.

Hecubus84

iTrader: (1)

So you're saying that it's better to leave his busted up o2 sensor as is?

Bosch o2 sensor: $30.00 u.s. - tops

o2 sensor socket: 10.00 u.s. - tops

Time to complete job: half hour (given you don't run into any major problems)

I fail to see the issue here.

Toxindude

Okay well thank you guys for your help I am gonna see what I can do here . How do you know they are 460cc high impedence . Also I already have the 02 sensor sitting here its just the old one wont come out so im gonna have to have somone drill it out or somthing .

Hecubus84

iTrader: (1)

I wouldn't give up on the o2 sensor just yet. Go get yourself a propane torch and a good quality penetrating oil like PB blaster. Heat up the manifold around the sensor and douse it with pb, repeat. With enough persistence it should come loose. A big breaker bar helps. Also, you may find that some of the threads in the manifold are garred up when you finally get the sensor out, a good auto parts store will sell a thread chaser specifically for this application.

Mechanic

torch the ****** out.... or ... maybe if u run the car hard and then try to pull it out, but i dunno about the second one... never tried it, possible equal expansion rate.

Toxindude

I have had the O2 socket heated it up hit it with penetrating oil had a big breaker bar on it even had an impact on it never gave .

SpeedOfLife

iTrader: (16)

well the exhaust will be flowing through the end of the sensor, and just across the inside of the exhaust, I highly doubt running the car hard will loosen it for you. torching is a good idea.

SpeedOfLife

iTrader: (16)

well no, there's no guarantee, but it's worth a shot. that way he might at least not have to have it completely retapped.

Hecubus84

iTrader: (1)

I'd still keep at it until you have no choice, there's still a chance it will come out - and thats a hellava lot better than drilling, tapping, and helicoiling that work-hardened manifold.

NZConvertible

Absolutely not, when did I say or imply anything like that?

I recommend anyone with a broken or old O2 sensor replace it with a new one, purely because of the small fuel economy benefit. But it won't cure bad mileage, it won't fix smelly exhaust, it won't improve performance and it won't have any noticable effect on the way the engine runs.

In this particular case, it's the least of his problems.

Toxindude

well i know what my money is going toward on payday i am glad i came here it seems i have caused my self more problems than i fixed .

misterstyx69

iTrader: (142)

OK..My Look at things...Since he Still has a Stock manifold and the O2 sensor is Toasted in there anyhow,Why not Get an Aftermarket Header??..Two Good things Come out of this..#1/he gets more Exhaust Flow,and #2/he gets a nicely threaded Place to Put a NEW O2 sensor in!(just need to extend the Wire on the O2 sensor so that it plugs into the harness connector.)..so there we GO!( www.racingbeat.com for the Aftermarket header!,and you may want to Beef up the Exhaust too!),..Screw the Tapping and Retapping,on 20 year old a Twenty Year old Manifold!..by the time you get the Damn thing all fixed up,and if Say,Your Time is like 20-30 Bucks an Hour,you got that Header Paid for already!~..

Hecubus84

iTrader: (1)

Quote:
Originally Posted by Hecubus84
...replacing your o2 sensor, exhaust gaskets, and possibly your cat (the honeycomb shoud be intact) would help the rich exhaust smell.

Replacing the O2 sensor won't do anything for exhaust smell, because the only time the sensor is only used duing loight-load cruising. Unless you're drviing along with your head hanging out the rear hatch, you ain't smelling the exhaust no matter how bad it is.

Quote:
Originally Posted by Toxindude
The O2 sensor in seized in the manifold and the wire is busted to it so that sucks and I know you may smell rich if its not hooked up .

Completely untrue.



Surely you can see that someone could infer that you thought it unnecessary to replace the o2 sensor from these posts.

Regardless, this is hardly a issue worth debating any further - thank you for clearing up my misinformation in my post.