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M2 Clone / Turbo Setup Diagnostic Question


burndog
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Here we go, I am new to the turbo field, so I am going to be posting a lot more questions...

 

I recently purchased a car with a Holset 35 turbo setup, Megasquirt IIXD and MSD 6 ignition through a distributor.  Besides the some of the popping, farting and flat spot at opening of throttle I seem to have a strange symptom.  The symptom is that around 5500 RPM I am building to the magic 1 Atmosphere of 14 PSI and the seems to pause, like taking a breath, the RPM's drop a little and the PSI falls off, suddenly it wakes up again and I am thrust back into my seat up until 14 PSI.

 

My first inclination is that I need to pull the Megasquirt map and look for a software rev limiter.  Second, am I losing my boost in the system due to leak or crack in the intake system?  Lastly, am I simply floating the valves and losing boost out the exhaust?

 

Thoughts?

 

BURNDOG

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You didn't say whether you were getting past 5500 or not. 

 

Electronic possibilities:

 

Bad spot in the fuel map

Bad spot in the spark map

Rev limiter in the MegaSquirt

Rev limiter in the MSD

 

Mechanical possibilities:

 

Loss of fuel pressure

Blowing out spark

Injectors maxed

MAP sensor fail at that point

 

I doubt you have a leak as it would probably show up even at lower boost. Any engine hesitation is going to temporarily stall the turbo.

 

As mentioned above datalogging is your best bet to see what is happening and where on the maps it is happening.

 

Rob

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Loss of fuel pressure

 

was what I was thinking too.

 

What does the wideband say?

 

Also, what does the Megasquirt say?  If it's losing tach for some reason,

cutting fuel, blah blah blah it will tell you...

 

t

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was what I was thinking too.

What does the wideband say?

Also, what does the Megasquirt say? If it's losing tach for some reason,

cutting fuel, blah blah blah it will tell you...

t

Megasquirt will not tell you directly if you have no fuel pressure. If you do something dumb like run out of gas or have your fuel line pop off, the car just sputters, and the a/f goes off-the-charts lean. I know from experience. Ask about my Sunday!

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