Let's talk about ECU's... I may buy one.
 

First of all, 1990 S5 NA Vert is what I am rolling in.

A forum member is selling a Jam Performance flashed N374 ECU. Obviously it was originally a turbo ecu, but it has been reflashed and apparently can run NA AND Turbo. The seller ran it in his NA vert for several years without issue.

So of course, I am contemplating tossing this into my NA vert. He did tell me I would need to upgrade my injectors from the stock 460cc to 550cc. Either that, or get an adjustable fuel pressure regulator. I am leaning toward the regulator because I do not want to remove my intake manifold.

So for the questions. First off, do you guys think I HAVE to upgrade my fuel system? I would imagine so, but I want to just verify. Second question. What pressure would my fuel rail need to be at to mimic 550cc injectors?

there is no reason to run that ecu...or a turbo ecu for that matter. NA's run rich stock, leave your 460cc injectors unless you have some heavy modifications to your engine.

I do not have heavy modifications, no. Obviously, I wouldn't upgrade my injectors just for the hell of it, I am very aware of the rich running NA.

But why not run the ECU? I understand you say no, but I am curious as to why not. You also didn't really answer my second question. If i decided to try that ECU out, would I neccesarily need to upgrade my injectors/fuel pressure.

you have to upgrade you injectors or you're going to run lean and blow your engine because the ECU will expect the injectors to be bigger than they are.

also, I wouldn't run that ECU either. why not just get an rtek or something reputable? the NA and TII engine are far to different to run well with the same ECU.

I've never heard of an N/a engine running lean and blowing, if anything it would lack power...

because your NA doesn't boost and doesn't need tuned the same as a turbo car. its a waste of money and will probably hurt performance.

If you're going to run an upgraded ecu, I'd recommend a full stand-alone, or at the very least a piggy-back system rather than a reflashed stock ecu. The reason I say this is that you can then tailor the fuel map to fit your application rather than trying to adapt your application to the ecu. No matter what you do, you'll be fighting the ecu the whole way. At least the stocker with, say, the S-AFC piggyback would be a huge improvement over stock because with a wideband o2 sensor, you can dial in your car for much better fuel economy, and the closer to stoichiometeric balance you get it, the more power your car will make.

On the flip-side of the coin, a stand-alone ecm would be a good option as well, albeit a more costly one, as you can set the fuel map as close to perfect for your engine as you can get, plus allow you to grow on to bigger and better things. Long story short, you can tune for peak fuel economy, torque, and horsepower due to the ability to tune your fuel AND ignition maps radically from stock if need be, and get the best out of your engine possible.

I agree with the others though, that running a reflashed turbo ecm is not a very good option for an essentially stock engine, as the n/a cars were kinda rich, but turbo's are pig rich in comparison, plus have a lower rev-limiter than s5 n/a cars.

As pointed out, there'd be no gain and likely even a power loss. The stock TII fuel maps are probably pretty close to that of an NA when not in boost (vacuum to 0 manifold pressure), but the other factor is timing. The timing maps are all LOAD based, which means it doesn't care if you're in boost or not. You'd be running some serious retard on timing to compensate for boost that isn't there. This would be a major factor leading to a large power loss.

Alright, fair enough, I appreciate everyones input.

So now how does one go about reducing fuel pressure? I know I'll need an adjustable FPR, but do I have to then somehow bypass the stock FPR?

Dare I ask why you are reducing fuel pressure?

Also, the stock FPR would have to be eliminated, so basically you'll need some billet fuel rails installed. Plus it eliminates the pulsation dampener, which isn't as much of an issue on the s5's, but can still fail.

I am not reducing it really. I knew I would get an answer to my question immediately if I said I wanted to lower it. If I said i wanted to raise it, the first responses I would have got was "why? the NA runs rich anyway". I just wanted to know how to install an aftermarket regulator is all.

Custom rails since it's an S5. S4s can get away with threading in new fittings and removing the stock FPR, but you can't use S4 rails on your S5 either (won't fit).

Really, I'm not sure why you'd want to go that route. An SAFC & wideband or an Rtek 2.0 & wideband will give you the ability to tune a little fuel out safely, and pick up some more power at the same time. Check out C. Ludwig's results on an S5 NA using the Rtek 2.0 to bring AFRs up to 13s: http://www.pocketlogger.com/index.ph...age=2&ecu=S5NA

leave well enough alone, the car is practically bulletproof as is, why mess with it for no gain?
you know how long it takes to get the driveablity of the stock ECU? the cold start, etc..

what is the attraction to this project?

Just for future reference, the person who told you this meant that the ECU is calibrated to deliver proper fuel assuming a flow rate comparable to 550cc injectors operating at the stock fuel pressure (37psi average). To emulate 550cc injectors, the 460cc injectors would need to run at about 53psi average. To achieve this on your S5, you would need aftermarket fuel rails, an aftermarket fuel pressure regulator, an upgraded fuel pump, and lines and fittings.

However, as mentioned earlier, a TII ECU probably isn't optimized for an NA engine anyway. If you want more power, just install a good aftermarket exhaust system, and your stock ECU will auto-compensate just fine.

Attraction? None. I am not going to buy the ECU. I also know how hard it is, I had to do all of that when I bought the car. :)

exactly. Ditching the stock ECU comes with a price.

I think the OP should look into getting an Rtek 2.1 . It will let you adjust fuel and timing which is enough for a nonturbo.

the pulsation dampener is on the other fuel rail... why wouldn't you just replace the secondary fuel rail?

Why are you hawking the Rtek man. I know what you run... or are you a traitor?

;)

lol, bottom line, I don't trust most people to tune their own engines :)

I've heard of an NA running lean and melting stuff because of hi EGTs and then never running right ever again....

Speaking of which, is there a functioning exhaust temp sensor on the floor pan in my vert? I know the turbo's had it, but I didn't know if the verts did too.