stauren1203

iTrader: (1)

I am currently in the process of trying to sell my 1993 FD, but as long as I still have it, I will still be upgrading it, very slowly.

Since I bought the car in August of last year, I have installed a Power FC (stock tune), an HKS Hi-Power 80mm exhaust, and an aluminum AST. I removed the AST because it wasn't a direct fir when I bolted it to the original holes for the plastic AST, so I threw it out. Financially stupid, but I was frustrated. I have also had all of the vacuum lines replaced because I was having a boost issue with my secondary which was caused by a leak somewhere.

I have also purchased a downpipe, but I have not yet installed it. I would like to do so soon, but as I've been searching for an answer to my specific question, I have found many other arbitrary (to me) threads about how much you can modify/upgrade before potentially causing harm without a custom tune.

One thing I have noticed, and I am not sure when this started, my 10-8-10 is actually an 11.4-8-10. This bit of reading I did on this sounds like that isn't a big deal, and apparently the stock setup is safe for like 12-13psi if I remember correctly.

Now, the question I have is: Is it safe for me to, with my current mods, replace the stock downpipe with a catless one WITHOUT having to have my ecu tuned or having to add/ modify anything on my turbo system?

fendamonky

iTrader: (6)

Do you still have your main cat in place? And are you sure that you don't already have an aftermarket DP on the car??? I find it VERY hard to believe that an FD is still running around with a pre-cat installed..

stauren1203

iTrader: (1)

Still have stock main-cat. I am POSTITVE original DP is in place. car has 37k original, 5k since I bought it. I am second owner, original owner was elderly (73 when he sold it to me). He told me there were 0 modifications ever, and it appears to be true

BLUE TII

iTrader: (9)

In my opinion if you want reliability you should remove the Power FC computer and put the stock ECU back in.

The PFC does not have the factory safeguards of the stock ECU such as knock control.

I have seen PFC cars blow engines from various scenarios where the stock ECU would have saved the engine.

I have been racing for a couple years now with-

Uprated ND pump (Supra)
K&N drop in air filter
Enfini "Y" pipe
Downpipe
Highflow cat (or stock, or resonated mid pipe with 2" restrictor at end)
3" catback
Hallman Pro RX manual boost controller on wastegate and prespool actuators for 10-10-10 boost pattern.
colder heat range stock plugs.

It does run much leaner than the 9:1 AFRs of the stock ECU (as lean as low 12s).

but

When I get a bad tank of gas with this car (often) it just hesitates as the stock computer pulls timing with knock. I can keep racing and fix the gas situation at the end of the day.

When I get a bad tank of gas with my stand alone ECU RX-7 it loses an apex seal (often as well).

I did put closed loop knock control on stand alone ECU one too, so last time it did hesitate as I raced, but still cracked the rear plate. Aftermarket knock control (with the traditional acoustic knock sensor) is not a viable solution as it won't be tuned precisely enough for the engine as Mazda did.

You will be limited in power on the stock ECU due to the 10psi boost. My car runs 109mph in the 1/4 mile (stock weight). Not a real powerhouse @ ~300hp.

airjordan223

iTrader: (8)

I'm in the same place as well with the K&N drop in, 3" DP, midpipe, and HKS hi power exhaust.

I've been looking for a power fc, maybe splurge and get the adaptronic that is starting to become more popular around here, but I haven't really seen any solid data/reasons why a PFC is required with these mods.

Maybe someone can drop a bomb of knowledge on us.

stauren1203

iTrader: (1)

AARGH. This is honestly the MOST challenging vehicle I have ever come across when it comes to differing opinions on what is "good" and "bad." I really, truly appreciate all of the help here, but how is it that nearly EVERYONE says that a PFC is basically the FIRST thing you should get for your FD, while others (seemingly as reliable sources) suggest you stay away? Anyway, the stock ecu doesn't work when the OMP is disconnected, and a good friend of mine is a technician and HIGHLY suggested disconnecting the OMP and premix instead for the health and longevity of the engine.

I'm not looking for monstrous power or anything crazy, I'm just trying to makes check marks on the list of "reliability" mods but I don't want to do things the wrong way or in the wrong order, so if a tune is necessary with the DP, I will skip it.

stauren1203

iTrader: (1)

airjordan223, you DO have the dp installed already? Do you get any boost spikes?

airjordan223

iTrader: (8)

Yes I have the DP installed. I just finished my 5 speed swap so I'm still on the auto ECU.

Still fixing some vacuum leaks and waiting for a boost gauge, so its hard to tell how everything is running. I need to replace all the vacuum lines since most of them are hard and not sealing very well. I have noticed that under WOT in 4th or 5th gear (higher boost) it sometimes cuts out, feels like a fuel cut or something for maybe a second, and then it keeps going. Not sure if this is result of a boost leak or this is a boost spike.

stauren1203

iTrader: (1)

Anyone with my exact setup including PFC have any information?

XLR8

iTrader: (52)

You should read the PFC FAQ. Depending on what model or release PFC you have, depends if you are running a "base" map or a "base-mod" map. The "base-mod is more flexible.

http://www.xsadclan.com/files/PFC/PowerFC_FAQ.pdf

Towards the bottom it will show you how to decode your PFC serial number and determine what you are working with. There is also a link in the document to a site that shows you what is relatively safe for each version of the "base map".

http://opus.bloomcounty.org/~patrick/pfc/

No matter what you do, I would consider rewiring your fuel pump, or even switching it out with a Bosch 042 or Supra pump.

BLUE TII

iTrader: (9)

I have noticed that under WOT in 4th or 5th gear (higher boost) it sometimes cuts out, feels like a fuel cut or something for maybe a second, and then it keeps going. Not sure if this is result of a boost leak or this is a boost spike.

Boost creep is causing the ECU to cut fuel. The stock ECU allows for boost over the stock 10psi around the 2ndary turbo transition at 4,500rpm, but the allowed overboost tapers down in stages toward redline to 10psi.

With my set up listed with resonated mid pipe I found I needed a 2" reducer to stop the boost creep. I found the stock cat or "highflow" cat will also provide this exhaust restriction and keep your car less stinky.

I found service records with my car from '97 where the straight pipe 3" cat back was causing fuel cut and when I bought the car in '08. The car was raced in stock class since at least '97.

I reverted the car to true stock class (previous owner fixed overboost with boost controllers and put a downpipe on it the year before I bought it) and continued to race with fuel cut for over a year.

I think its safe to say the factory fuel cut will not kill your engine, but it will drive much better without it.

fendamonky

iTrader: (6)

That *should* provide enough restriction that you won't have too much issue keeping boost levels down.

The stock fuel setup can provide enough fuel for about 13psi if I remember correctly, however you'll be pushing towards the ceiling of what you can run reliably at that point so I wouldn't try to do that for too long..

He's both right but also partly wrong on this count... The OMP as it sits from the factory isn't the best because it's injecting used engine oil into the engine. The engine oil will work for lubrication, but it isn't designed for that.

The OMP does a great job of lubricating the engine at all times, where as running premix alone can actually lead to under lubrication of the engine (in the case that you aren't injecting much fuel, like a long deceleration).

The alternative/best of both worlds is to keep the OMP just have the OMP feed from a separate reservoir that you keep full of a good ashless pre-mix.

If you were to do that, and run a low to moderate amount of premix (say 1/2 oz per gallon of fuel) you'd be absolutely set!

Even if you aren't looking for crazy power, a good tune is *always* a worthwhile investment. It allows you to get the most effective use out of your other modifications both in regards to power, drive-ability, and economy. You might not "need" to get it tuned, but you should certainly want to get it tuned.

stauren1203

iTrader: (1)

Funny you mention the deceleration because ive wondered about this but havent really looked into it. I assumed, because the injector duty goes to 0% when decelerating in gear that there would be no oil as well so I went ahead and made a habit of NEVER coasting while in gear.


How confident is your "*should*?" I have no problem leaving the stock one in, I just want to do what's best for the car.

Im not opposed to getting a tune either, I just am assuming that whoever buys my car when they do will be modifying it further so if the stock tune is satisfactory for me then I would rather keep it stock for the sake of knowledge to the next owner.

fendamonky

iTrader: (6)

The PFC is capable of still injecting fuel on decel, but I guess most tuners turn it off.

I've never run a stock cat in my car. When I got my FD it already had a 3" DP and a high flow cat. I added a PFC and a Greddy SMIC almost straight away. After that I went with an Apexi N1 Dual cat back.

My car ran pretty well like that, but I also got it tuned shortly after putting that stuff on. The next step was for me to upgrade my injectors, my fuel pump, add a free flow midpipe, a Profec B SpecII and tune for higher boost.

When you say "if the stock tune is satisfactory" do you mean the stock ECU, or the base map on the PFC? A PFC map specific to the modifications on your car will ALWAYS be preferable to the base map, even if you've only got an intake installed.

SA3R

This.

The stock ECU has knock-retard control, and the PFC does not. Under full throttle/full boost, this could be the difference between BOOM and er, nothing happening.

There are too many stories of these cars going pop and the owner comes and posts in here, and notes he has a PFC as well. I'm not saying Power FC's are bad, but I believe that on the street, in all varied traffic conditions, there are too many chances for knock detonation to kill an apex seal or damage the internals.
Example- you're in traffic, its a hot summer day, and you're in 4th or some gear too high for the speed. Rather than change down and accelerate, you're lazy, so you put your foot down and make the hot engine lug under a high gear at low speed. Perfect situation to induce detonation under load.

The stock ECU would sense the knock and pull the timing back, listen for 10 seconds and monitor for further knock.

The PFC would not give a ****. It doesnt care. It would continue on and detonation would continue.

Consider this, before you pull the trigger on a PFC or any programmable ECU you intend to run on the street. None of them have knock-retard. You will be exposed to detonation, no matter how good you think your "tune" is. The "tune" will not minimise detonation for every single situation, of which there are thousands of possible scenarios. The stock ECU can.

People dont want to listen and think I sound crazy when I denigrate the PFC, because the PFC makes you go fast and feels like a super duper feel good performance addition. So many people use them, what could possibly be bad about something that was never tested or endorsed by Mazda, and never helped the 787B win LeMans, right?

adam c

iTrader: (2)

Spending money on upgrades to the car will not increase its value. If you are going to sell it, leave it stock. You are throwing away money.

stauren1203

iTrader: (1)

Im not planning on buying anything more. I bought this before I intended to sell it. I just havent installed it. After all of this cross information I will probably not install it and just include it with the sale

Tem120

iTrader: (5)

After about 12 PSI of boost you will need a tune , if you are hitting 11.?? psi as it is now if you remove the cat , add a downpipe you will need to adjust the boost / duty cycle. as it is . and you will more then likely need a Wideband . to make sure. you aren't going lean.