Hey everyone,

Ive been holding off making a post about this but I can’t seem to figure this out alone. I’ve just finished building a S4 Full Bridgeport NAT FC rx7. When it’s cold it will start off the key, maybe a little finagling with the accelerator and it’ll light off no problem. When it’s hot however, it’s a beast to get started. Fresh engine so I know compression isn’t an issue. Messing with the tune myself and using fc tweaked lead me to good cold starts. But now I’m stumped with hot starts. My second issue is the car won’t hold an idle after it warms up. Cold, no problem it’ll pulse away, even warm is meh, but hot no chance. I can hear the BAC trying to keep up but the rpms just drop. I tried adjusting the throttle body to let more air in, but that seems to make starting the car more difficult, and throws my tps beyond where I can adjust it to spec. I even went the distance and built a 2kw starter and installed an optima red top battery. My most recent discovery is I’m able to get it started again hot after adjusting the cranking ms to 40ms! I know Bridgeport’s are thirsty, but damn….

if anyone has any insight or tips for me to try I’m all ears. Thanks everyone!

 

it kind of sounds like its too lean? on my car, hot start is like a point AFR leaner than when its running. couple reasons for it, the intake temp sensor heat soaks for one.
i added fuel in the idle cell, and all the cells below it. so like N2 P5, N2 P4, and then N1 P1 to N1 P10. this worked for me, but i'm also stock port/stock fuel

also if you go into the commander you can use the temp +/- fuel screen.

 

Can you elaborate a bit on what you mean by a hot start? Like for example, you shut down fully warmed up, leave it for XX minutes, and try to restart? If XX = something between 15~30 minutes, and it's also a hot day, is it hard to start? What about if XX = only 1~5 minutes, does starting get easier then? If XX = an hour or more?

^That's what I'm thinking as well, and why I asked the OP to clarify the hot start symptoms. Does the Power FC offer something like an IAT fuel trim table? I'm on a Link G5, and am using an IAT fuel trim (3D table, IAT vs. Time elapsed after Engine Start) to richen up the fueling specifically to deal with heat soaked IAT sensors on hot start situations. Since I'm running a modeled fuel equation mode, if IAT is reading higher that reality (because sensor body is heat soaked, and air is not flowing thru the manifold yet to cool it), the ECU will make the fueling leaner than it should be. So the fix for me the fix is the IAT Fuel Trim table below:



As you can see, this table richens the fueling by up to 20% at the hottest IAT's, and only for the first few minutes of engine run time after starting. These fuel trims progressively null out to zero after a few minutes of engine run time.