nlc1179

i picked up some greddy 720cc injectors to run as secondaries and i need to know what else i need so i can run them fine. in the near future im am getting full 3" exhaust and a walbro 255 fuel pump. oh...its for my '88 TII

Evil Aviator

First of all, you need to know if the GReddy fuel injectors are the same impedance as your stock injectors. See Tech/Injector Information on this site:
http://www.rotaryresurrection.com

Next, you will need some type of fuel injector controller. You can use a simple injector controller like an S-AFC, or you can use a full standalone EMS from Haltech, Microtech, Wolf, etc.

Besides the upgraded fuel pump for the exhaust, if you retain the stock ECU, you will also need a fuel cut defenser (FCD) and an aftermarket boost gauge. If you use a reprogrammed ECU or a standalone EMS, then you may not need a FCD or boost gauge. Depending on your boost level, and how you drive, you may need to port the turbo wastegate to avoid boost creep.

nlc1179

thanks for the help. im not going to worry about the fcd though. i planned on porting the wastegate anyways and i am going to get an aftermarket boost gauge sometime in the next few days. im probably going to make a boost controller too. i shouldnt have to worry about boost creep. any ideas on where to get a nice s-afc that isnt going to cost an arm and a leg.

Evil Aviator

I that case you can save a lot of money by not buying anything that you have mentioned, and you can also sell those 720cc injectors.

It's probably better to put your money in the stock market or real estate right now, anyway. That's what I am doing.

coldy13

As I see it, all the fuel cut defensor does is cut off fuel if the boost creeps too high. If he ports the wastegate then he shouldn't have boost creep, so why would he NEED a fcd?

nlc1179

thank you, at least someone sees where im coming from. there is no need to waste money if you dont need something.

BASTARD

iTrader: (4)

Things to get

1 - 680cc primary injectors from 85 GSL-SE

2 - put 720cc in secondary position

3 - Get Fuel cut defence (so you don't run lean and blow your motor)

4 - Cone air filter (use the K&N FIPK for the non turbo. it is CARB legal sticker)

5 - Boost controller (manual one works fine, you can use a air compressor pressure control valve from Home Depot)

6 - Get the bigger replacment BOV (I think Mazda Trix sells it...it looks similar to stock but it's a little bigger)

good power for minimum cost

BDC

This whole thread makes me shiver both from the technical standpoint as well as the financial (personal) standpoint.

I've been through all of this concerning the base-line modifications. I wish I knew then what I know now about this stuff and what some of the more wise options there are available for the FC.

The FCD is a very bad idea. To quote Bastard, "3 - Get Fuel cut defence (so you don't run lean and blow your motor)" -> My point isn't be glaringly disrespectful, but I have to say that the majority of the FC community out there seemingly believes and adheres to this idea although it's technically backwards. The purpose of the FCD is quite misleading although it does alleviate a short-term, more of an "in your face" type of problem: One, it leads people to a false sense of security through their lack of knowledge on the subject about the nature of how fuel works, how spark ignition works (and when), as well as what's demanded of both of those under higher engine loads. The ECU sees a false pressure signal and will retain certain leading advance (and trail-split timing) as well as fuel injection output according to the lower-than-real boost level. While the ECU is correcting for, let's say, 7.5psi, the engine is sometimes seeing as high as 13, 14, and 15psi. In this instance, grossly speaking fuel injection should be up by about 20% while leading advance should be *retarded* by as much as 7 to 8 degrees.

We wonder why so many FC's blow up that use the typical intake, exhaust, and FCD time-bomb combination -> they're ripe for pre-ignition failure.

Friend, it's my suggestion that you stay away from the cheap things and add-on boxes and, instead, thoroughly plan out exactly what you want your car to do and how you would like for it to perform. A standalone system such as a Haltech E6K is more than adequate for everything you'll ever need if you wish to march away from the stock engine/stock turbocharger platform. Otherwise, keep the stock injectors, stock FPR, and stock fuel pump, and never boost over the fuel cut limit (~8.6psi).

B

rotarysc

I learned the hard way too, EMS really is the answer. Assuming its tuned close enuff, "If it saves the motor once" its paid for itself.

S-AFC = $300
FCD = $100
3" exh = $400
720's = $100
EBC = $300
Btl o Tums = $5
Total for all the bandaids for the car and you = $1205

Save yourself $5 and start with an EMS

E6X = $1200

nuff said, plz don't hurt another RX7. Your right in asking for advice, so don't get offended, just soak it in and think it over.

Evil Aviator

... and why would he need the 720cc injectors, S-AFC, Walbro fuel pump, boost controller, and aftermarket boost gauge? There is absolutely no reason for these items unless the boost is increased. For that matter, why not just save some time and money and forget about the 3" exhaust and wastegate porting? Do you see my point?

As to why an FCD would be needed to go along with the larger injectors, boost controller, and fuel pump, it is because if these items are installed, it is assumed that the engine will be boosting over the stock level since there is no other purpose for these items.

Yes, I see where you are coming from, and there is no reason to buy any of those items, and like I stated earlier, you can sell those 720cc injectors to save some more money.

I would also suggest this. However, although I don't like them much, I am not totally against the cheap add-on boxes if they are applied correctly. My main problem with the add-on boxes is that they are not worth the money when you compare them with a budget standalone EMS.

Good advice.

scathcart

To continue on what BDC said...
It is a common misconception that the FCD causes the engine to run lean. When the fuel is cut, it cuts the injector completely. It can't run lean; there is no fuel injected. NONE.
Mazda put the fuel cut in to prevent overboosting and thus prevent detonation. Do you really think they would be so stupid as to put on a product that would cause the very problem the spent money engineering a solution for?
And for those who claim Mazda was idiotic about everything they did, and didn't know what they were doing: try it. Blow your engine by fuel cut. I have porven this on several occasions first hand. The engine WILL not detonate from fuel cut.

BASTARD

iTrader: (4)

i just want to say that i removed my FCD from my car to loan toa friend...i then drove my car , i was coming down the 405 into Van Nuys... WOT in second gear when "cink cink a little hesitation and then it all made sense when i got off the freeway and pulled up to the stoplight and my engine stumbbled and died...hmmmm i don't think it was coincidence , but maybe i am wrong

RETed

Lots of misinformation in this thread...

Our testing shows that the boost sensor does NOT affect fuel delivery.  The PRIMARY sensor for fuel delivery is the airflow meter.  We're looking to thoroughly breakdown the stock ECU code (see thread in FC section) to get a definite on what exactly what all the sensors do.  Henrik claims the boost sensor does affect fuel delivery, but he's doing a raw datalog of a running engine, and I find too many flaws with his testing.

Thus, the FCD is a compromise device that DOES work.  There are limitations on what it can or cannot do.  Running up to 10psi should NOT be a problem with an FCD.  I have NOT heard of someone running just 10psi with an FCD that has blown their engines YET.  I do not recommend running 15psi+ with an FCD - that's just asking for trouble.  If you want to argue about an FCD's effectiveness, go argue with Racing Beat, HKS, and GReddy - all of them STILL sell FCD's (clamp-type) for FC's to this day; I tend to believe those manufacturers that people spouting off their misinformation online.

Not all FC owners can afford a stand-alone EMS AND installation costs AND tuning costs.  Even a bargain basement Microtech is going to cost over a cool grand when you pay for the unit AND installation AND tuning; don't assume people can install and tune one of these things.  I've seen too many screw-up's with the install and tuning that will sometimes end up in dead engines.  I feel confident that an FC owner can purchase and install an FCD unit though...

And, if you don't believe banging off the stock fuel-cut will not hurt the motor.  Why don't you explain to me what I blew my 60k miles 1987 Turbo II banging off the fuel-cut twice within 10 seconds.  Mods were STOCK everything with the exception of pre-cat and main cat both gutted.  I hit a slight hesitation on the freeway, and I wanted to make sure it was the fuel-cut or not - twice in 10 seconds, and I was only into the fuel-cut for a split second.  Came to a stop after getting off the freeway, and the car would barely idle.  Compression check 10 minutes later confirmed blown apex seal.

I have recommended FCD's to several people, and they have all been happy - their engines are all still running.  My stipulations were that they run a rewired fuel pump circuit and a Walbro 255lph upgrade fuel pump.  The FCD does work, and it does it's job well, IMO.

I can't change what other people think, because this difference in views on FCD's has gone back for AGES.  There's a lot of BS out there, so be careful on what you read.  I think I state my case pretty effectively, as I am able to present evidence and examples of all my argument points, while others just claim vice versa without offering proof of such wild theories...

This is the internet; you can believe what you want...


-Ted

nlc1179

there will be boost increase. why the hell would i get that stuff if i wanted to keep my car a stock boost for racing. im not that much of a dumbass. you need to quit being such a dick about everything. i dont even know exactly what i am buying yet and you are acting like i have everything writen in stone. i made this tread so i could get some suggestions on what i should do and so far you have been the least help out of everyone. you just keep arguing with me. i might just get a microtech to start off with instead of the exhaust and s-afc. i dont know right now.

scathcart

Well, I can report the opposite from experience (bounced my shitty-engined TII off the stock boost cut to check if it would kill the engine... I could not do it), so in that we differ.
Can you explain how detonation occurs when all fuel is cut?
Can you explain why Mazda would engineer a device that was meant to prevent detonation, yet would actually cause it?
I am surprised, Ted. You are normally so hype on providing a technical reason for why something occurs, not just "this occurs b/c I said so".

j9fd3s

iTrader: (3)

i think his point was that if the stock fuel cut is around 8.6psi and the stock fuel system is good to 10psi, why are you buying a fuel system for 15psi when you arent going over 8.6 with the fcd?

decide how much power you want and the path to getting it will become a lot clearer.

RETed

Oh, I have an explanation; it's just I'm tired of repeating myself everytime I go through this whole explanation...

When you bang off the fuel-cut, the fuel-cut drops load, which drops the RPM and boost.  Once the boost level drops under the fuel-cut level, the ECU starts shooting fuel back into the engine again.  Now, maybe my age has slowed my reaction time, but I doubt anyone would be able to react on the first cycle of the fuel-cut?  This causes the lean condition, which skyrocket EGT's.

I can't speak of Mazda position in this, but I've heard too many people (including my direct experience) blowing their motor hitting the fuel-cut.

If your experience runs counter to this, I would peg you as lucky.

There are people who say FCD's are evil, but yet offer no real alternative except for "go stand-alone EMS".  This is not a practical option for a lot of owners.  Even reprogrammed ECU's, which cost several hundreds of dollars, are rather pricey options versus the FCD.  If the FCD works, why look elsewhere?  These people are implying you should stick with the stock ECU with fuel-cut versus run an FCD???


-Ted

-Ted

nlc1179

you arent talking about me are you? because i never said i was going for stock boost. i will be running stock boost for the street most the time, but when i am racing, i will run 13-15psi probably.

hondah8er

On a sort of different note....what would happen (bad or good) if instead of getting a FCD you just disconnected the boost sensor?

$150FC

the vast majority of stock cars still have original injectors.

our cars flood because these old injectors leak.
edit: that's not the only reason, but it still affects the situation.

parhaps when fuel cut occurs, injectors leak fuel into the combustion chamber? that would obviously cause a lean condition, because it would not be very much fuel injected at all.

just a thought. because i don't think that mazda would add a system into a car that would blow seals. on purpose, anyway

j9fd3s

iTrader: (3)

ok you lost me, how are you gonna do that without the fcd?

coldy13

Ok, I'm a carb guy, I hate stock ecu systems, but I think I'm starting to get this.

There is a stock fuel cut at 8.6 psi. So, if you try to turn up the boost with a boost controller, the ecu will cut off fuel when it hits 8.6 psi. The FCD is made to trick the ecu into letting it boost higher.

The thing I don't get is, if you know the fuel system and injectors can support 15psi, then why can't you just remove the fuel cut completely, and never boost over 15psi? Is there just no way to remove the fuel cut without switching to an aftermarket ecu?

RETed

In fact, that's what the Japan guys do when they can't get an FCD...
When disconnected, the ECU defaults to a 4.x psi setting.


-Ted

RETed

My experience shows the stock fuel system can safely support only about 12psi and 250bhp.

Without an FCD, they only way around the stock overboost fuel-cut it to go reprogrammed ECU or standalone EMS.


-Ted

Evil Aviator

You shouldn't volunteer your time to point out things like that or he will call you a "dick".

Ways to remove the fuel cut:
1) Standalone EMS
2) Reprogrammed ECU
3) FCD

Example of Reprogrammed ECU:
http://www.pocketlogger.com/index.php?pid=rtek7feat

FYI, just because the fuel system can handle more boost, it doesn't mean that the rest of the engine can. There are still detonation, pressure, and heat issues to deal with.

BTW, your carb experience still applies to an EMS. If you just realize that an EFI EMS is a simpler form of a carb that doesn't need vacuum, you will be fine. Everything is digital, and there are hard numbers (although relative instead of finite) instead of vague screw and spring settings. However, they do the same thing for the most part. You know how you increase and decrease various carb settings (trends) to yield the best results? The same thing goes for an EMS, but most of the inexperienced tuners don't understand that because they like to chase numbers that they read on the internet (to their peril). You have a huge advantage over the high-tech newbies, trust me.