Larger intercooler = running lean?

[Jim_rx7]

Me, you, Mike... cups of tea... my shed. lol.

[interloper393]

cups of tea??!! fook that i drink jack daniels man lol

[m4drx]

dont understand the intercooler propblems you guys talk about. larger normally means a slight drop in boost pressure and its just like a cooler day so whats the problem?

the air temp sensor in the plenum will surely realise when its colder outside?

[Jim_rx7]

Mmmm... yeah. Good point.

Surely the ECU can somehow compensate if it\'s really cold outside? Ie, more boost. Or the fuelling is adequate enough for when it is very cold outside.

I\'ve never heard of a car having issues because it was boosting when the air was really cold (more dense - ie, same as having larger IC).

Any thoughts?

[Red and Single]

Any thoughts?

Seriously, you\'ll get a *MUCH* better performance increase from the ECU than any other mod you have, AND it will add safety.

There is only one logical peth here, buy your ECU (Apexi??) when you can afford it , and then fit the IC at the time of fitting / mapping.

2p  :WaveBye

[michaelb]

I have decat zorst, bov,  induction kit and about to fit a large smic.

I will be getting a PFC about June and a remap.

What are the possible implications of running the mods without remap?

Hi

Have a look at this link and get the Apexi PFC asap

http://www.mazdarotaryclub.com/forums/showthread.php?t=37184

You will have to get one before the smic, I personally would not take the chances you take - driving with out a PFC and a map...

Regards,
Michaelb

[Jim_rx7]

A larger SMIC cools the air better, therefore you get desnser air, which means your getting more in so if you have more air you need more fuel, e.g you\'ll run lean.

A

I had a wee think....

Surely all a larger IC/SMIC does is help keep the intake temps lower, then in thoery allowing you to run more boost as long as you have sufficient fuelling.

So running stock boost with a larger SMIC/IC, I don\'t see where the problem would lie? No more fuel would need to be added, hence you shouldn\'t run lean???

Might be wrong though.


PS: I am on the hunt for PFC.

[strange_days_uk]

OK Jim,

Cooler air is denser air, more oxygen contained in the same volumetric space, so therefore cooler air is more air.  If you put more air into the engine, you need to inject more fuel also.  Otherwise, the mixture is too lean and will pre-ignite.

Really and truly there would not be a particular problem sticking on the smic and driving about, because yes the stock ecu will inject more fuel as the charge temp comes down.  The point is, with your current setup you are getting a larger volume of air flow already, which the ecu will not be allowing for, so to further push the limits you are treading a dangerous line, already you are running a risk of det without further modifying the car.

Play safe, think with the head not the heart on this one :o

[n4bes]

Hi Jim,

I am no expert mate but I can only advise you follow the advice of guys who have owned these, some what tempremental, cars for a period of time mate. They have all have a knowledge of what can go wrong, and it does not sound too good. You should defo fit the PFC before you do owt else to it, better safe than sorry mate.

My 2p\'s worth.

[Jim_rx7]

Another question.....

Alot of problems in other cars arise when you fully decat etc, because due to less exhaust restrictions the boost pressure rises. At this point, more boost would mean more fuel required. Although there\'s usually always a safe limit you can get to without needing a mappable ECU. Usually the fuelling is good upto a certain point.

Is this not the case in a Rx7? Has anyone wired up a A/F gauge on a slightly modded rex with a stock ECU?


(not trying to argue with anyone here.... just curious)

[n4bes]

Another question.....

Alot of problems in other cars arise when you fully decat etc, because due to less exhaust restrictions the boost pressure rises. At this point, more boost would mean more fuel required. Although there\'s usually always a safe limit you can get to without needing a mappable ECU. Usually the fuelling is good upto a certain point.

Is this not something to do with the Fuel Cut Defencer......??

It will stop the engine from cutting fuel in a "safe Mode" idea....

[interloper393]

The stock ecu can only handle air filters and a backbox bud, anything else you`ll be running lean, dosnt matter what other cars cn do and let you get with.. rotarys are very unique and tempermental, they dont like to be messed with unless done right
These engines are all rubber seals n paper gaskets lol.. fairy fragile..
Your new to the rx7`s, all the advice above is spot one, as Neil says these guys know there stuff.. iv been reading everything i cn get ma hands on about these cars for the past 2 years, still sh!t loads i dont know n understand.. if you want advice phone a engine rebuilder/tuner like WGT, reworx ect.. ask your questions n they`ll answer in great detail lol

Cheers
Craig

[strange_days_uk]

FCD is a way of bypassing boost limit.

A lot of Jap cars are set to run at a set max boost, say 7 psi.  The FCD is effectively a resistor which you splice inline between the boost sensor and the ecu.  The ecu then thinks the car is only boostin 4 psi when you are actually boosting 7, and so you can run say 12 psi instead of 7 limit.  The big prob here though is that you will run 12 psi but only be injecting fuel for 7psi.  FCD like this is a big nono on Rex.

[Jim_rx7]

Yeah, normally you would also fit a FCD. But again, the fuelling would usually be good upto an extra point. Then it would run lean unless controlled.

Which leads me back to my previous post.

[interloper393]

most other cars if you fit a exhaust, decat or filters, just dis-connectin the battery, press the brake to totally drain the car and re-connect the bat and the ecu will learn the new mods..usually warm the car before hand then red line in most gears to get a newish map.. well thats what i was telt lol