Spider Monkey

Hey guys, I'm pretty new here so I'll start out by saying I have an 88' TII.
My question (and im sure it has been covered before; I just want a clear answer/explanation) is that I'm looking at 2 different fuel cut defense systems, the RacingBeat FCD, and the Rtek 1.5; I want to know the advantages and disadvantages of both.
I'm planning on getting the full RacingBeat exhaust, an hks SQV3 bov, and an hks high flow filter. With these added which of these systems will be better suited?

RotaryRocket88

iTrader: (7)

An FCD like what RB sells is a device that intercepts the boost signal to the ECU, and fools it into thinking boost is below the cut level (8.6 psi). This is a bad thing. The boost signal partly determines fuel delivery, so if you trick the ECU into thinking boost is lower, it will not delivery as much fuel as it should.

There's little point to an FCD these days. An Rtek chip just removes the fuel cut code. It has side effects that could blow the engine, and has other benefits like lowered secondary staging.

If you get a full exhaust, you'll end up with boost creep (spiking due to small wastegate). With an FCD or chip that removes fuel cut, you'll overboost and blow the engine. Check this link for some info on porting the wastegate to reduce or eliminate creep: http://fc3spro.com/TECH/HOWTO/ZWG/zwg.html.

If you're going the Rtek route, I'd suggest the 1.7 chip and a pair of 720cc secondary injectors. Add a better fuel pump (such as from an FD), and you'll have a cheap setup capable of 10-12 psi on the stock turbo.

Spider Monkey

Ok, so the basically the 1.5 is inadequate if I'm planning on getting the full exhaust so I should go with the 1.7 and bigger injectors? Can you tell anymore about the 1.7? Also how much will the bigger injectors/fuel pump effect mpg (average)? thanks

RotaryRocket88

iTrader: (7)

A 1.5 chip will technically work, but you'll be hitting the max safe duty cycle of the injectors. I see 72% max duty cycle with a 550/720cc combo, so 550/550 would be right around 85% d/c, which is the limit for an Rtek chipped ECU.

720cc secondaries aren't really going to have any impact on mileage. The 1.7 chip will run them at lower duty cycles to match the fuel delivery the 550cc injectors had, but you'll have more headroom when you floor it (before they hit max duty cycle of 85%). Same thing with a fuel pump, as long as you avoid something like a walbro 255, which will drive fuel pressure up. An FD fuel pump is perfect for modified stock turbo setups.

Spider Monkey

Ah I think I understand, so with the 1.7 and the bigger injectors you're basically lessening the load on how hard they have to work? (more or less) Also would I have to increase voltage to the fuel pump or anything like that?

RotaryRocket88

iTrader: (7)

Yes, essentially you lessen the load on the injectors, but running an injector at max capacity also means you can't deliver any additional fuel past that point. A little room to work is a good idea.

Search thread titles for "fuel pump rewire" in the 2nd gen section. You don't have to rewire the pump in every case, but a TII does use a resistor/relay combo to reduce voltage to 9v at idle and low load. There have been cases where this failed, and the pump stopped switching back to 12v+. Old wiring will also increase resistance & lower voltage.

Spider Monkey

Sweet, thanks for clearing this up for me. I'll definetly do the search on the fuel pump rewire.

Also, I would like to message you the setup that I'm planning so I can get your opinion on it; of course, this is if you have time.
thanks again