K.ronic

I want to put a new full exhaust system on my car (turbo back), but it's my understanding that if I do this I run the risk of detonation due to it running lean. I've been told that to do this I need to either get a stand alone ecu which will mean that I have to have someone with a dyno and knowledge of how to tune the ecu for my application or get a piggy back which requires basicly the same thing because I have no idea how to tune these things. I guess what I'm trying to figure out here is if there is any way around this or am I stuck with dumping a bunch of money into the ecu just to install a new exhaust?

My other question is about injectors. In the future I plan on running a larger turbo which will mean that my fuel system will need to be upgraded to handle the extra air comming through the system. At this point I may have a problem with leaky injectors (it still has the original OEM injectors) so what would happen if I installed larger injectors now with the stock tuning? Would they work correctly just not to their full potential or would this cause me flooding problems? In my mind if the ecu is telling the injectors what to do it shouldn't matter if their bigger because they will only inject as much fuel as the ecu tells them to. Am I totally off base on this or no? I figured that if I have to buy new injectors anyway why not get the ones that will be used when I get a larger turbo if, in fact, I am correct.

rotary emotions

What car do you do have? (FC, FD?)
As far as I'm aware, just installing a different exhaust won't need a fuel system upgrade. If you own an FC TII, a fuel cut deffender might be a good choice though.
Once you go for a bigger turbo, you'll need more fuel though.
The ECU does not tell the injectors how much fuel they need to deliver. It just tells the injectors how longe they should open. This means that when a stock ECU controls larger injectors, it will open them for just as long as the stock injectors. As a result, when you'd use injectors double the size, they'd inject double the fuel under the same condititions.
So you'd run way too rich at low(er) rpm. You can upgrade the fuel pump, but if the pressure at the rail is higher then stock, with stock injectors, you again get too much fuel at low rpm. Normally the pressure regulator can deal with this, but with my car I believe the FPR actually can't lower the fuel pump pressure enough.
The best bet (when going for a bigger turbo) is to install a piggyback ECU that can adjust injector timing both ways (less fuel when running at low rpm, more when the revs go up) This way the larger injectors will give the same amount of fuel as the smaller stock ones did at the lower boost levels, keeping the engine under same conditions as before the mods. Once the revs and boost go up, it'll be able to deliver the richt amount of fuel.
You'll need a good dyno to make the most of it though.
A stand alone ECU seems a bit over it, allthough it would give you the most flexibility. You should consider the route you plan to go first I think. If you plan to keep the modifications coming one step at a time, you should consider this before buying the parts. If you only want an exhaust, there's no point in buying expensive aftermarket ECU's.
Rotary tuners are few and far between, even in Germany. But a good dyno and tuner can give good results.

K.ronic

Thanks for the input. I posted this way late last night and I forgot to mention that it was a 1989 (S4) T II. I do plan on doing many mods to it one step at a time (as the money becomes available), so from what you said my money will probably be best spent with a stand alone because thats what it will have in the long run anyway. With that said, as far as the larger injectors are concerned, if I do go that route then I will need something (piggy back or stand alone) to make them work correctly with a stock tuning if I understand you correctly, right? And as far as the exhaust is concerned, if I have that HKS air flow kit I mentioned in my other thread and a new larger exhaust you don't think I will run into problems with a lean condition? From what I understand to be true, if you add more air then you must add more fuel correct? Or is that what the fuel cut defender is for? I am just a little scared that if I don't do things in the right order then I could be causing myself a major problem. And on the subject of rotary tuners and dynos do you have any suggestions as to where to go for this? I visted Mireck a while back and he suggested taking my car to England to have this done, but I'm not sure if I have the money or the time (My car is a daily driver) to do this. Is there anyone maybe a little closer where I could get this done? Again thank you for responding, I'm trying my hardest to learn all the things I need to learn to make my car as nice as possible so any help is greatly appreciated!!!!!

hIGGI

iTrader: (7)

http://fc3spro.com/TECH/FM2W/power.htm

if you read all this and something more, start asking questions

K.ronic

Awsome...Thank you Higgi. I sometimes have a hard time finding things like this.

hIGGI

iTrader: (7)

well, bookmark fc3spro.com then, as it have most information about your car you could ever find at on place, sorted out...

rotary emotions

eh, yep Higgi got it all right there...Should have mentioned it. I have been searching that site often enough
Nevertheless, tuning in England seems a bit over the top, don't you think??? As long as you keep te engine stock inside, tuning is tuning. As long as you keep a bit of a safety margin, and make sure there are no lean spots in the mapping, any good tuner will be able to handle rotaries just fine. Basicly, the same values matter for a rotary as for a piston engine. Fuel to air ratio is the main thing. As long as you keep it just a little richer then needed you'll be ok.
The real deal starts when you need a proper engine builder: not many pro's around that can do a rebuilt for power.

K.ronic

Mireck seems to be the man for that job (engine builder). I have the upmost respect for his abilities. That man lives and breathes rotaries!!!! In fact, I think he has rotors where his heart should be!!!!!!

rotary emotions

You ain't saying Mireck hasn't got a heart do you? Well, of course he is indeed a rotary maniac (and that's, of course a good thing to sy about someone overhere )