ECMlink Choppy MAP boost readings at WOT- Resolved

[ist dwa]

I am open to any ideas on how to fix this, the boost reading is oscillating/choppy ~4 psi through out the pull.

I am using an OMNI 4 BAR, it is bolted to the back of the 1g intake manifold. There are no "T"s used, it has a dedicated 1/4" line that is about a foot long and the port I am using is the one next to the brake booster port on the plenum.

I am going to switch the port location to the end of the intake plenum. I don't feel the MAP is bad but I know it isn't right, want to get this fixed.

Here is a screen shot of 3rd and 4th gears.

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[DSMPT]

I don't know what setup you use. But to me, it looks like you are reaching the limit of gate spring rather than a bad MAP. Would you get more steady boost if lower the boost a little bit?
If I were you, I would try a higher pressure gate spring and make the controller/solenoid setup milder. and of course just in case, would make sure if there is no boost leak.

 

[ist dwa]

I am peaking 40lbs of boost. I am running a genuine TIAL 38mm gate. I was running a single 12psi spring last season and changed them to 2 springs that totaled 20 psi which is right on par and it made a slight change to what you see now. I just checked a previous log running 32psi and it was doing the same thing, maybe a tad worse.

I also put in a stronger MBC spring as well with no avail.

I suppose I could do another boost leak test but that was already performed and good.

 

[DSMPT]

I am peaking 40lbs of boost. I am running a genuine TIAL 38mm gate. I was running a single 12psi spring last season and changed them to 2 springs that totaled 20 psi which is right on par and it made a slight change to what you see now. I just checked a previous log running 32psi and it was doing the same thing, maybe a tad worse.

I also put in a stronger MBC spring as well with no avail.

I suppose I could do another boost leak test but that was already performed and good.

As we assume there is no boost/exhaust leak at all.
Can you still go higher boost than 40 psi? I mean, not peak number, a steady 40+ psi. And without the MBC, do you have less oscillating?
If you can go higher boost than now and if you have less oscillating without the MBC, my guess would be, that MBC works like that way. An electric solenoid would adjust more finely.
In case if you can't have higher steady boost than now, my guess would be, it needs higher pressure gate springs or/and higher pressure valve springs.

 

[ist dwa]

Problem solved, made several hits tonight. Just changing the vacuum port location solved the issue, I just swapped my FPR and MAP vacuum lines and it is soooo much smother. Car felt great, and the A/F ratio also got more clean and consistent as well. BTW I got this idea on a post on the ECM link forums, Dave or Tom suggested this when a choppy signal is present.

"It may have to do with turbulence in the intake manifold near where the MAP sensor is connected. You might try a different source.

Dave"

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[DSMPT]

Glad to hear that it got better. Of course, choosing a stable pressure source is critical... Even the hose diameter, too. And it should be as close as possible to the source for FPR and the hose should be as short as possible. Many people are saying that using a "T" is bad. But many people misunderstand. In some case, yes bad but It is not always bad. This is why actually Japanese aftermarket manufacturers recommend to take a pressure source for a MAP sensor from the hose for FPR by using a T. Because it should be the most stable place to take and those should read the same pressure numbers.

 

[ist dwa]

That's irony of this, the location is even further now and I used a smaller hose ID extension to reach the new further source because that's all I had. Cars!

 

[DSMPT]

That's a recommendation for finding a stable source. It doesn't mean it has to. If you find a stable source then that's the same thing, it would work. The point was to find a stable source.