BTW, the solenoid controlling the vacuum signal the fuel pressure regulator (FPR) is not present in the S2000, I was using that as an example. The big picture is to be able to control the amount of fuel during hot starts which is different from cold starts.

In the rx7, the stock FPR is connected to a solenoid. The solenoid essentially allows the FPR to see vacuum or boost from the intake manifold...just as we have in the S2000 or just like any car for that matter. During hot starts though, the fuel in the rail or lines could boil from heat soak. This turns the liquid fuel into vapor. In vapor form the injectors really have no fuel, that's why often people say "I have to wait for the car to cool down".

Anyway, back to the FPR solenoid. So most of the time the solenoid just lets the vacuum or boost travel through it. However during hot starts it switches and sends 0 psi (atmosphere) signal to the FPR instead of the vacuum signal. This does 2 things:

- it increases the fuel pressure pushed by the in-tank pump.
- it forces cool fuel from the tank and sends the vapor back.

I have not studied the S2000 carefully enough to see how it deals with vapor lock. If AEM said they need to add a resistor, I assume this must be a way to trick the ECU in thinking more fuel is needed. This could be added to the MAP signal possibly or to the injector signal. I don't know, if they told you any more specifics perhaps we can figure out how they intend to get over that problem.

On the subject of fuel. The S2000 does have a very odd fuel rail setup. Typically the FPR is on opposite ends of the rail from the Fuel Feed Line/Pulsation Damper, however in the S2000 both are side by side. Not sure if this has anything to do with the vapor lock problem or not, but its just something I noticed.

cheers

W

 

Sorry, one more note...next time the car is hard to start hot, pop the hood, pull the vacuum line at the manifold that goes to the FPR, then start the car. If it starts just fine then you know it was vapor lock...connect the vacuum line and drive away.

cheers

W

 

Cool man thanks for all the good info!! O I love your avitar, my roommate has a Rx7 FD so he would get a kick out of it.

 

I know this is a very, very old post but it sounds like something that happened to my 05 the other day in a bad spot. Stalled the car backing up a gravel drive by being too careful with spinning on the gravel. The car wouldn't start. It would barely turn over a few times like the battery was dead. I was on a very slight incline and bumped it off on the gravel, much to my disbelief....and my wife's.

Anyway, got home and it has been starting okay the past few weeks. Just exactly where is that line to pull?