Last night I put my 3 inch downpipe on the car and made a full 3 inch exhaust... Removed the cat as well. The car runs unreall I can not belive the power the car has.. the Problem is that the car shuts down in 3rd gear at around 6k.. Almost like it on the limiter. Do I need a new ECU more fuel or both? What do you guys think is going on. I do not want to drive it this way for the fear of breaking something..... Only other mod is a blitz air intake rest of the car is stock....

Thank you,
Craig K
Drivinhard.com

 

You are going to blow your motor!

You are hitting the overboost fuel-cut. You need to spend some time reading this forum for modding advice. Do not drive the car again until you put the main cat converter back on.

A midpipe (removal of main cat) is a MAJOR modification to these cars and should not be done lightly.

 

I agree with rynberg..

The reason you felt bigger pull is because you are running higher boost..

I would first get a boost gauge, boost controller, and upgraded ECU.. You will blow your engine.. Just just went full exhuast and neither my PFC or AVC-R is controlling it correctly... but just creeping a little.. i cant imagine with out one..

Do a search and read about adding midpipe..

 

thanks for the imput. This is what I thought was happening. What ECU do you guys think gives you more bang for the buck. I will probablly one day rebuild entire mottor and go single turbo Is there an ECU I can keep and use for that application or would I have to buy another one...?

Thanks,
Craig K
drivinhard.com

 

There are so many mods required to safely support a midpipe. Please just spend some time reading/researching. It has all been discussed many times.

You will need a stand-alone ecu to run a single turbo, such as an Apexi Power FC, Haltech, or AEM EMS. These will require tuning by an experienced tuner with a wideband o2 sensor (unless you want to pick up a wideband and tune it yourself...).

 

if you don't put the cat back in you'll be rebuilding the entire motor and turbos next week - seriously, no BS.

 

If I do not want to go with a stand alone like the power FC or the AEM. What are my other options. I can always sell what I have when it is time to upgrade..

Thank you,
Craig K
drivinhard.com

 

Power FC is the best ECU you can get IMHO. You can view the boost, knock, water temps, battery power, and more from the commander. Also you can set the boost and use it as a boost controller as I do.


BTW...rynberg is right.

 

You could go after a PFS purple box (am I saying it right guys?). They've been out long enough to be readily available used ... about half the cost of new. I use one and am perfectly happy. However, I have to agree with everyone. The fact that you have pulled you main cat and are talking single turbo says stand alone ECU. The piggy back ones (like the PFS) just won't cut it with your proposed mods.

 

I agree with others.. U definitely need ECU upgrade.. Only few will handle midpipe and all.. You need to get PFC.. not PFS (peter Ferrel (sp?) purple box)..

Just as others said.. do a "search"... It located top right hand corner of this page..

But to save you some time.. as others have answered my question when I first join this forum... PFC (PowerFC by Apexi) will be more useful in the future.. But you need to know not to mess with it.. Even experienced FD owners who **** with it blows their engine.. Make sure you get it tuned by an expert.. Not some shop you never heard of.. I'm completely serious and don't take this lightly.. And I'm sure most PFC owners will agree with me..

PFS purple box is piece of crap.. my opinion but others might disagree..

Bottom line.. If you have a good tuner in your neighborhood... use what they are using... If you have a good tuner who only tunes AEM.. get tthat.. if they only tune PFC ... get that.. I hope you get this point.. Otherwise, You have to willing to drive someplace to get it tuned.. DO NOT attempt by yourself.. Unless you're willing to make mistake and learn from your mistake..

Hope this helps.. If you want more detaild to what each does.. do a search.. there are ton of info and someone has asked the same question you have.. and been answered..

 

powerFC is good you can plug and go and see what is going on

 

Don't skimp out on the ecu. Definitely get the Power FC. It has been out a while so people know it well enough to help you with any problems you have/tuning you need. And it can control the twins while you have them, and the single when you get there. It's $1300 from rx7store.net (sometimes $1250) and worth every penny.

But, like herblenny said, get one that people in your area are familiar with. The AEM ECU is just as good if not better than the PFC, but it's pretty new so not as many people know the software inside and out.

 

put the main cat back on for now and see if the car cuts out.

 

Again I just wanted to thank you guys for your imput I did a lot of research on what you guys what you guys said. Please excuse my ignorance but i am used to working traditonal motors but the RX7 is the one car that I always wanted. I understand why my car is doing what is doing.. What I do not uderstand that if the car is making too much boost and shutting down. Why do I need a ECU.... Why can I not just adjust the boost with a controller? Also if it needs more fuel why cant we just add more fuel (IE) bigger injectors, fuel pump, adjustable regulator... Just asking please again any help is great thanks guys...

Thanks again,
Craig K
Drivinhard.com

 

It sounds a little like you're looking for an excuse to run the midpipe without an ecu. I think that would be a mistake.

The danger is detonation due to running lean. i.e., you're getting too much air (or not enough fuel - same thing). A boost controller will lower the pressure to stock levels (maybe), but you'll still be flowing way more air than stock, hence the danger of running lean, even at stock boost levels.

I believe adding fuel hardware may not be enough - you need the ecu to control the fuel (correct me if I'm wrong guys)

Good luck, and please listen to these people. They know what they're talking about.

 

here is why you can't do it

A) Stock ECU cuts fuel above 12psi, that is the hesitation you are getting!

B) Stock turbos boost control SUCKS! hence you are getting over 12psi with full exhaust

C) Stock Fuel and Ignition map are ok for stock boost but above them you should have an remapped ecu or PFC

personally its cheaper to buy an ecu than it is to blow the engine and replace it and then have to buy an ecu. why make the mistake the first time ?

 

I think the deal is that even though you limit the boost PRESSURE to 10 lbs with the Profec, you are running a higher VOLUME of air through the engine than the stock ECU is set to handle due to the higher flowing mods you have. Recall that the stock ECU delivers a set amount of fuel for a given pressure at a given RPM, with other factors thrown in as well such as intake temp, fuel temp, engine temp, and so on, all based on the stock system's pressure AND volume. You probably CAN just up the fuel with one of those suggestions you mentioned. But you cannot be SURE that the right amount of fuel is being added at the right time... you're just guessing with the fixes you listed above, and if you guess wrong, well that's $7000 (or more!).

Further, the increased air volume, which requires the fuel increase you are rightly guessing you need, does not address any ignition timing changes that may need to be dealt with to handle the increased flame front travel that occurs due to the higher amount of air (higher cylinder pressure) and subsequent fuel mixture. And if you do spike the turbo, the extra fuel may not be enough to allow for quenching the possible too fast flame front, and you rattle, and you spend $7000.

So minimally, to be SAFE with your engine, then both interactive fuel control (not just blind fixes that might work) AND properly tuned timing maps are required. Some ECU upgrades are designed around your mods, and shooouuuuld work out of the box. But if they don't, OR you didn't give them all of your mods, OR you change your mods (and once you start, can you EVER really stop?), then the reprogrammed chip will no longer support your system, you overboost or hit fuel cut, and you spend $7000.

So ultimately, buying a programmable ECU and having it tuned properly (and the two are REALLY BOTH required, near as I can tell) allows you peace of mind, the best power (your solution above might easily run rich, and you won't get as much power as you think you will ), and should cost less than $7000. Besides, after you pay the $7000, you will have to buy an ECU anyway so you don't KEEP paying $7000.

But what the hell do I know? I'm still running stock-ish, though the DP and RB cat back are allowing a leeetle more than 10 lbs. Hmmm...

 

ahhhhhaaaaaaa Vosko thanks that is the answer I was looking for.. that is the information that I did not have... Now I see why I can not.. Looks like I wil be ordering a power fc in the morning.. It is not that I am trying to cut corners or be cheap money is no object. It is more that I am trying to understand what is going on here.. Again thank you for the help.. you guys have been great.. Now I have seen that the power fc is not really great for controlling boost and some peolpe recommend a different boost controller. How do you feel about this?

Thanks,
Craig K
drivinhard.com

 

PFC can control boost pretty well on the stock twins as well as any other boost controller

 

Yep, you need to upgarde your ECU or get a PFC. Otherwise, you will need to get a new motor.