434josh Posted March 6, 2019 Report Share Posted March 6, 2019 Is there a way to setup a safety around fuel pressure? I would like to have a safety that says if fuel pressure drops during wot acceleration i would experience an ignition cut or reduced boost. Possible? Quote Link to comment Share on other sites More sharing options...
Ducie54 Posted March 7, 2019 Report Share Posted March 7, 2019 Not sure others have done there's but i set the Map limit table with temp on one axis and differential fuel pressure on the other. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 7, 2019 Report Share Posted March 7, 2019 Depending on how many other safeties you want there are various ways to do it. The most important thing is as per Ducies example - use Differential fuel pressure rather than just fuel press so you dont need to complicate things with boost. The simplest option is one of the GP limiters. Example below would be for a normal target FP of 300KPa. If we have more than 275KPa, the ECU is not going to take any action (limit 10000RPM), if FP drops below 274KPa it is going to limit the engine to 2000RPM. Between 274 & 275 the limit will be interpolated between those values. The RPM axis is not normally needed for electric fuel pumps. Some people get more creative with MAP on one axis to allow more tolerance at low boost pressure etc but this is up to you. Quote Link to comment Share on other sites More sharing options...
434josh Posted March 7, 2019 Author Report Share Posted March 7, 2019 Thanks all. This is perfect. I didn't have a ecu read fuel pressure until this week - just a dash gauge. I run staged dual walbro 450 pumps and had an incident last week where a ground wire was pulled loose and well..one 450 is only good for about 660 whp on e85 as I found out on the dyno. The operator got out of the throttle when lambda reached .906 at 6500 rpm and 13 psi. Its impossible to watch everything all the time so I wanted a built in safety for just this reason. I always know if my main pump is working since the motor won't run otherwise but the staged pump is a crap shoot. I will set it up as a map limit instead of rpm. My base pressure is 300 kps but it idles at 255 because I have decent vacuum and on decel it can get as low as 220kpa so I would be afraid an rpm limit might be harder on the motor but I could be wrong. Thanks again! One more question though.. My "fuel system" was setup as map referenced before today. If I change to FP Sensor will that alter my ve table fueling any? (provided things were setup correctly before) Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 7, 2019 Report Share Posted March 7, 2019 2 hours ago, 434josh said: My base pressure is 300 kps but it idles at 255 because I have decent vacuum and on decel it can get as low as 220kpa so I would be afraid an rpm limit might be harder on the motor but I could be wrong. Thats why you use differential pressure, not gauge fuel pressure. It should remain close to constant regardless of vacuum or boost. Quote Link to comment Share on other sites More sharing options...
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