Need help on flat spot

[me2kimi]

Hi all sifu,

I got a problem here with flat spot. My current setup is silvertop engine with balcktop ecu, bigger fuel pump and adjustable fuel regulator.

The flat spot occur when pedal suddenly press during idle or at low RPM. Notice it during 2nd gear.
At higher RPM the problem is not noticeable.

When this problem occur, I can heard 'singgghh' sound from engine bay.

Try to set the fuel regulator at 38 and 42 psi, but not make any difference.

What should I do and what should I check?

Thanks in advance.

 

[xtremeleo]

sounds like a tuning issue jer, maybe its ignition related?

 

[me2kimi]

ignition related?
Mind to explain about that sir?

 

[levin818]

Your TPS setting is out.

 

[me2kimi]

bro levin, I've check TPS setting by referring service manual.
Everything is in correct range.

 

[xtremeleo]

have u checked what is ur ignition timing now?

 

[jimmyae101]

have u checked what is ur ignition timing now?

yalor,what timing?d ur spark plug okay?use platinum one from denso

 

[Captain Fast]

original timing should be around 10 degrees with a variance of -+2

 

[me2kimi]

Thanks for all replies, yes it about the ignition timing. I've advance the timing by myself for a while. Will send to tune the timing with timing light later.

 

[levin818]

Have you solve your flat spot?

 

[me2kimi]

Bro levin, I've already done tuning the timing. It's better than before. But still not perfectly eliminate the flat spot problem. Sometime pinging occur.
I've also changed AFPR vacuum from single throttle to common vacuum.

By the way, what is suitable AFRP pressure? some said set at 38 psi, 40 psi or any pressure.
Is the pressure is set during WOT or vacuum on?

 

[xtremeleo]

set the fpr pressure during vacuum off sir, 3bar shud be good enough for an na. preignition is caused by too much ignition timing in ur case. r u sure its flat spot dis time?

 

[pcmoddingmy]

I think the ECU retards the timing to reduce pinging, which could explain the flat spot. Check ur plugs to see what color they are. Or you might want to get AFR checking via wideband 02 sensor. U can contact bro Ryzal 0122800058 for AFR wideband analysis & advice.

 

[chinozie]

error code > tuning > check O2 sensor > TPS > ECU ...normally will end up with Wong... :D

 

[levin818]

I still suspect that its TPS's setting out.
When you check your TPS's range, did you apply vacuum to the Throttle Opener?

 

[me2kimi]

I think the ECU retards the timing to reduce pinging, which could explain the flat spot. Check ur plugs to see what color they are. Or you might want to get AFR checking via wideband 02 sensor. U can contact bro Ryzal 0122800058 for AFR wideband analysis & advice.

I'll looking forward to that.

Bro Levin, I did check TPS setting by measuring voltage across the terminal.
I'll try to check the TPS by measure the resistance.

BTW, forgot to mention that I am using open pod air filter.

Then funny thing happened yesterday. I've refill half ron95 to a half ron97. As a result, I feel the power output from the fuel mixture are better than full tank of ron97. hmmm :stupid:

 

[levin818]

That is not enough. What you need to check are:
1) IDL-E2 is shorted when the throttle stop screw is at 0.8mm or less from the lever
2) IDL-E2 is open circuit when the throttle stop screw is at 1.0mm or more from the lever
Above test must be done with vacuum apply to the Throttle Opener.

A bad setting, for eg, if IDL-E2 is open circuit only when the throttle stop screw is at 2.0mm or more from the stopper --> you will have flat spot when the throttle stop screw move from 1mm to 2mm from the lever.

 

[me2kimi]

Owh with vacuum on..
I've tested with vacuum off.
Will re-test it later bro.
Thanks...

 

[me2kimi]

Bro levin, I've carried out test the TPS setting today. It seem's to be ok as your guide.

There's one more thing that I noticed is the flat spot occured when gas pedal hardly pressed and when the time VVT engaged, fuel start to lean. After about 2-3 second, it went back to normal.

I think the problem might caused by insufficient fuel while VVT engaged.

FYI, I'm using AFR and VVT indicator.

 

[pcmoddingmy]

There's one more thing that I noticed is the flat spot occured when gas pedal hardly pressed and when the time VVT engaged, fuel start to lean. After about 2-3 second, it went back to normal.

I think the problem might caused by insufficient fuel while VVT engaged.

FYI, I'm using AFR and VVT indicator.

Hey, AFR was tested using wideband o2 sensor or narrowband? Well, its common that AFR will tend lean during sudden WOT where VVT kicks in as well. This can be reduced by airflow map tuning (piggyback/standalone) and increase the fuel press. However, if you noticed the AFR will change from very lean to very rich as you floor it towards 8000rpm.
Try to check your fuel press to see if its sufficient at WOT.

Cheers