SaabGuy

My ecu log shows boost fluctuating all over the place. It jumps 3-5 psi up and down. For example, one tick shows 9psi, while the next tick shows 15psi. My autometer boost guage stays very steady at whatever boost. (creeps but does not jump everywhere)

Ignition timing is also spoofed by these pressure ratings since timing retards and advances with boost pressures.

I know the stock setup uses a very small PILL right up near the boost sensor, its about a 5$ part from mazda. I have not done this step yet.

I was also recommended to use the smallest, hardest, silicon vacumm line I could find, and also reccomended moving the map sensor (inside ecu) as close to the engine as possible. i have replaced the supplied black rubber vac line with a very small silicon (hard) line.

What the heck is this fluttering all about??

Attached is a log taken from when on the dyno. Look at LOADs.

Josepi

I think it's kinda odd that the timing is varying with the same sensed pressure.

Example:
Lines 45 v. 63 v. 73

Or maybe I don't have a clear understanding of reading it. In any case, I'll save a log tommorow and show you how mines acting...i'm seeing steady boost...but it maxes out at 2-3...

No7Yet

I suspect that's wastegate flutter. You have a stock turbo with a ported wastegate, yes? Try adding a pill to the wastegate line.

I've cut the idling out of the end of the log, and reattached it. It makes it easier to see the fluctuation.

About the timing; that's just how the timing in the Microtech works - t*rpm + t*map.

Brandon
BR7 Racing

No7Yet

Whoops.

10sec rx7

is that off the dyno or the computer?

i would say you have it hooked into a bad boost source or have something Teed off it ie BOV??

where is the map sensor connected??

SaabGuy

I have it hooked into the stock boost sensors location. I also had the BOV T'd off it. I'll have to try a few things and see if it get any better.

10sec rx7

Dont T a BOV off it, they leak causing the problems you are having, i always hook up the map sensor by itself and nothing else on it,

Dale

SaabGuy

HA!!

Bad BOV. Bad. Go home! PSSstst

10sec rx7

you can never get a perfect seal on a bov,

SaabGuy

ok well Im getting a turbo xs bov soon anyways. it will be lined to some other vac nipple.

Josepi

I have a type S and like it.

SaabGuy

I have applied just about everything I could. Pills in the w/g, pills in the map line, pills in my stomach, and oh boy now the room is spinning. The map sensor line is really hard silicon, very small, and is on a dedicated possition on the manifold. The vac line is just under 3 feet long.

Well Im still getting boost fluctuation, but I have another idea. The map sensor is connected to a vac nipple right above the BAC, and my BAC is still allowing slight ammount of air to pass through.

Perhaps the pressure just after the turbo is at a much higher pressure than the rest of the system, hence pressure drop from the intercooler.

Maybe the MAP sensor is sensing this slight mixture of 2 different pressures; variation in manifold pressure since before intercooler pressures are higher than after intercooler. Seems logical because the vac line is sooo close to the BAC's inlet to the upper intake manifold. I'll try blocking that POS off.

Josepi

Somewhat related:

My BAC is blocked off and I'm using the nipple (capped from factory below the BAC) for MAP. At idle, I get a variation of about 2" in vacuum. 20-18-20-18-20-18...obviously, this then affects the fuel, then the idle itself. Vacuum leak somewhere?

Piranha

Even if air was going in through the BAC it wouldn't effect the reading on the MAP sensor unless you had it plugged into the BAC itself.

SaabGuy

well im trying to find a solution for the problem

No7Yet

Okay, Eric...

Hook your map sensor up to the bottom nipple on the front of the UIM - that's the one closest to the throttle plates. Hook everything up elsewhere. Hook the wastegate line up to the old air supply valve line (on the back of the IC). Make sure it's alone, just like the MAP line (save for a boost controller).

Keep us posted.

Brandon
BR7 Racing

SaabGuy

Problem solved. Thanks Brandon for the idea. SO I wonder if I can run it the other way if I block off the BAC.

chris_stampe

Havin the same problem. My boost is solid at 15, then goes to 3psi then my fuel leans out b/c of the drop, then the boost goes back up and the car starts hesitating because of this ****. Can I adjust the microtech to somehow fix this?

10sec rx7

if your boost is going from 15psi to 3psi you have a problem some where, like a split vacuum line etc,

Dale

chris_stampe

Still dont know why it did that, but it's fixed now. It still does it a little bit, but only by about 1-3psi.