Loud BANG on ignition
04-15-2005, 07:57 AM
#1
Moderator
Thread Starter
Loud BANG on ignition
My S has the Comptech SC with 8lb pulley, AEM EMS, 550cc injectors and AEM FPR.
Sometimes when I turn the ignition on there is a fairly loud and deep bang from under the bonnet. It sounds like ignition in the intake manifold or perhaps the sudden release of pressure.
My car was idling high today (around 2000RPM) and a quick look under the bonnet showed that the vacuum line from the intake manifold to the Idle Control Valve and FPR had come off. I wonder if this was caused by the bang.
I seem to remember a post about this previously but my searches revealed nothing. Does anyone have any experience with this issue?
Sometimes when I turn the ignition on there is a fairly loud and deep bang from under the bonnet. It sounds like ignition in the intake manifold or perhaps the sudden release of pressure.
My car was idling high today (around 2000RPM) and a quick look under the bonnet showed that the vacuum line from the intake manifold to the Idle Control Valve and FPR had come off. I wonder if this was caused by the bang.
I seem to remember a post about this previously but my searches revealed nothing. Does anyone have any experience with this issue?
04-15-2005, 09:39 AM
#2
Registered User
Its because the startup table in the basemap for the AEM EMS, has an "all on" parameter meaning all of the injectors are open for a few miliseconds for a "quick" startup. Simultaneously, your coils are charging; when they release, well, you get spark. The extra fuel in your motor/IM then ignites.
Ive seen this probably 25 times in 6300 miles; all "bangs" yield around 6psi on the boost guage, so it cant be that serious(you see 240-260psi on the compression stroke, while testing compression).
I asked my tuner why the basemap is like this, he said its because the S2000 is a "hard starter", meaning its a PITA to get it fired up; apparently the Evo8s are like this too.
I havent unchecked the "all on" parameter yet, but Ill work on it, see if it helps any.
So in a word, dont worry about it! Just make sure your foot is on the clutch at all times when touching the key
Ive seen this probably 25 times in 6300 miles; all "bangs" yield around 6psi on the boost guage, so it cant be that serious(you see 240-260psi on the compression stroke, while testing compression).
I asked my tuner why the basemap is like this, he said its because the S2000 is a "hard starter", meaning its a PITA to get it fired up; apparently the Evo8s are like this too.
I havent unchecked the "all on" parameter yet, but Ill work on it, see if it helps any.
So in a word, dont worry about it! Just make sure your foot is on the clutch at all times when touching the key
04-15-2005, 10:07 AM
#3
I have experienced the same symptoms. Good point about the clutch. Without touching the start button, I have had the car jump about 6 inches when turning the ignition on. Freaky since I didn't expect it at first. 
.
04-17-2005, 04:05 PM
#7
Originally Posted by AusS2000,Apr 15 2005, 10:57 AM
Sometimes when I turn the ignition on there is a fairly loud and deep bang from under the bonnet. It sounds like ignition in the intake manifold or perhaps the sudden release of pressure.
Glad this one got figured out...
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04-18-2005, 05:41 AM
#8
Check that your injectors arent leaking down. Had this Bang on a car with a leaky injector and it knocked out the head to inlet manifold gasket and blew off lots of vacuum hoses.
Best way to check this is to pull the fuel rail back from the inlet manifold after shutdown and see if any fuel leaks. Fuel pressure gauges can be misleading as the pressure can also leak back through the fuel pump.
Another give away with a leaky injector is if the engine runs rough for the first few seconds. One spark plug gets saturated with fuel on startup. If you pull the plugs immediately after startup you should be able to tell which injector is leaking.
When you turn on ignition, depending on the timing of the ignition and boot up time for the ECU the igniters may fire once. Many ECU's have a function that triggers and holds the igniter trigger low to avoid overheating the coils/igniters if the ignition is left on. When they switch to low the igniters will file the coils.
I would also check the start settings for the AEM. I'd be surprised if it pumps in fuel before the engine rotates. Normally ECU's put a little extra fuel in on cranking to assist starting. I havent checked if the AEM does this before cranking.
Chris.
Best way to check this is to pull the fuel rail back from the inlet manifold after shutdown and see if any fuel leaks. Fuel pressure gauges can be misleading as the pressure can also leak back through the fuel pump.
Another give away with a leaky injector is if the engine runs rough for the first few seconds. One spark plug gets saturated with fuel on startup. If you pull the plugs immediately after startup you should be able to tell which injector is leaking.
When you turn on ignition, depending on the timing of the ignition and boot up time for the ECU the igniters may fire once. Many ECU's have a function that triggers and holds the igniter trigger low to avoid overheating the coils/igniters if the ignition is left on. When they switch to low the igniters will file the coils.
I would also check the start settings for the AEM. I'd be surprised if it pumps in fuel before the engine rotates. Normally ECU's put a little extra fuel in on cranking to assist starting. I havent checked if the AEM does this before cranking.
Chris.