Speedsterclub.nl

markv schreef:In de bergen wordt dan de brandstofdruk idd terug geregeld. Maar, is dat nou eigenlijk nog echt nodig met een dergelijk motormangement? Ik bedoel, dat ding zit toch continue bij te regelen via z'n lambda metingen. Als hij ziet dat het zaakje te rijk aan het lopen is doordat er in de bergen wordt gereden, dan stelt ie dat toch automatisch bij? Klinkt een beetje dubbel op dit.
Alhoewel het terugregelen van de brandstofdruk natuurlijk wel helpt als de ECU in open-loop draait..

Mark

I suppose I will jump in and answer everyone's questions here haha. Yes, if you increase the fuel pressure at the injectors the IDC usually drops down under closed loop conditions. Now it's been several years since I have played with the GM reflash so I can't remember what the open loop power enrichment AFR was set at (Not that it really matters for this discussion). I remember it being rather rich but my point is that the IDC will typically go to those set parameters (PE AFR) to achieve that AFR with much less IDC change in reference to fuel pressure. Essentially in open loop (WOT) the IDC is typically less affected than it would be in closed loop. Did I lose you yet haha? The GM 36lb injectors are actually rather impressive when it comes to handling extreme fuel pressures (trust me I have put them to the test). They do not clip even well beyond their max duty cycle limits however, this is not to say that the spray pattern doesn't begin to deteriorate with extreme pressures and max duty cycle. You can get those GM 36s to perform pretty close to 42lb norms with fuel pressure manipulation.

In regard to the normal fuel pressures it will range from 50psi to 60psi (idle) depending on several factors but primarily the pump itself.

The stock GM FPR has a 10 psi sweep in vaccum from absolute to atmospheric however, have you guys ever noticed where the stock vacuum line runs on the factory intake system? This is where it gets somewhat comical and I haven't entirely determined if this was a design hiccup or what but the "vacuum" reference is pre-throttle body on the J-bodies. In other words there is NO vacuum reference to the stock FPR even though there is a dummy vacuum line connected. One might ask, well if that's the case perhaps the stock air box is just so restrictive that perhaps it still sees vacuum. Well this is not the case, the stock FPR NEVER sees vacuum on the factory fuel system. The FPR is simply in place to maintain a static pressure at the rail at all times at atmospheric fuel pressure conditions (approx. 60psi) regardless whether you are at WOT or idle. One might now say that can't be! There must be vacuum at that reference under load then, again the answer is NO there isn't. The FPR on a stock J-body fuel system literally does nothing but maintain a static pressure regardless of vacuum reference haha!

Now, for those interested in what the stock FPR does under atmospheric plus conditions (boost). The stock FPR is actually a 1:1 FPR that will increase fuel pressure 1 psi for every 1 psi of boost. I have tested the stock FPR up to 20 psi which actually ends up dead-heading the stock fuel pump. For those not familiar with the term "deadhead" in regard to pressure and fuel pumps, this means the pump reached it maximum pressure limits.

For those who were curious about bigger injectors and the affects on the fuel pump. This is a volume issue when it comes to bigger issues and stock pumps. The stock pump has a limit as to how much volume of fluid it can pump which in turn directly affects rail pressures as well.

Chris the rail and most every other fuel system component I have personally tested over and over to well over 120 psi (not that you would ever need to go that high nor do I condone it but it answers your question as to whether the system can handle the increase). Putting that system at the pressures you want is not an issue.

Alan - CaliforniaDomestics