Fluttering at 8-10 PSI

[TurboBob]

could be the MAF

The translator output connector pins are slightly thinner than the stock MAF, so there has been one time that there was a bad connection there.

The MAF circuit receives ground from the back of the passenger side head, and the +12 is fed thru a harness splice that is subject to some corrosion....

If it were ignition then it wouldn't pull strong at WOT, so it's something air related.

Bob

 

[alb84]

Soungs to me like the rod on the waste gate needs to be lengthened. If you are running 25 psi by adjusting the rod, there is not enough(rod length) to open it enough when there is soo much extra capacity at low boost. You can adjust the rod out, and use external springs to achieve 25 psi at wot. So just adjust the rod out, and tell me what you get. Later....Danny

 

[Razor]

The motor is new in the car, turbo, etc etc..is all pretty much new. I been working on getting all the drivability stuff aired out on it. So experience with this car to me prior than Oct 2003 is ??? The wastegate rod was put on the car by hand initially, whereas it had zero tension. An ATR bleeder was being used to regulate boost.

For the last couple weeks a high blm condition was being chased down on the car. While the BLM's were pegged, I never got on the car. Along with a lot of other stuff that was wrong, now the drivability is great. So on went the alky kit..dialing the kit in, is when I noticed this condition of the 8-10 PSI surging. I thought..too much alky .. So after powering down the system come to realize it does it also without the alcohol..so its not a fuel issue.

Thats where it was left..so I was thinking wastegate issue. Another wastegaste was installed, a HD one, and this time tension was put on it.. since no tension had cuased this..lets try some tension. Same deal.

Bob.. will try the different MAF, probably be a couple days tho till I can get to play with it again.

alb84, I have read about the external spring. can you elaborate a little further. What kind of spring, where to mount, what tension, etc.. I've only used stock and HD style WG diaphrams. So I assumme the spring goes from puck arm to WG diaphram?

thanks guys..

Almost there..car is at 90 percent

BTW Bob..aside from the MAF dropouts..pretty awesome stuff 25 PSI on 93 with zero retard.. I love the way the translator/exctender controls the O2's whereas you dont have that huge spike in O2's and keeps them flat..really nice curves. good Work ... appears to be an excellent match with my alky kit.

 

[TurboDave]

Razor,

Your symptoms sound exactly like the problem I chased for several months.

Finally decided to try another MAF just for nothing better to do.
Walla, problem solved. My LS1 MAF had gone belly up, and the symptoms I suffered were exactly as yours.

I'm now running on my spare LT1 MAF, looking for a replacement LS1 MAF.
(shhhh don't tell anyone, but I had forgotten that I dropped my MAF a few weeks before my symptoms started )

 

[UNGN]

Originally posted by alb84
Soungs to me like the rod on the waste gate needs to be lengthened. If you are running 25 psi by adjusting the rod, there is not enough(rod length) to open it enough when there is soo much extra capacity at low boost. You can adjust the rod out, and use external springs to achieve 25 psi at wot. So just adjust the rod out, and tell me what you get. Later....Danny

If the wastegate rod is set at 25 psi, the wastegate should be welded shut during this whole deal. Trying to hold 8-10 psi with your foot is regulating boost on the compressor side and has nothing to do with the wastegate (turbine side).

Trying to regulate turbo boost on the compressor side will cause unsteady intake flow, so the MAF readings will be whacked. If the MAF is malfunctioning, the readings will be even more whacked.

 

[alb84]

The external springs are a patch, and I probably should not have mentioned them. Years ago people would buy a different WG to acheive a few more lbs of boost. The difference was just a stronger sping in the WG. Then we started shortening the rods, and then along came the adjustable rods from the factory. My point is that it is preferable to increase spring resistance rather than shortening the rod. The shorter the rod, the less the WG can open. At part throttle the WG is not welded closed, it is modulated by the selenoid and ecu. A weak selenoid could cause the same kind of problem. If you look at the after market boost controllers you will see that they have some major ecu brain power dedicated just to the modulation of the WG selenoid. Oh well, Just wanted to give you some ideas on things to check. Later....Danny

 

[Lee_Burough]

What would Tonto say?

If Tonto and the Lone Ranger wanted to know which way the wind was blowing, Tonto would lick his finger and put it in the air to test the wind direction....

If you'll allow me to play Tonto's part here, with my finger in the air now....Yes, yes, its prolly the MAF, or a ground for the MAF: Meaning, when TurboBob and TruboDave speak on these and related subjects, I'm all ears

I'm also a satisfied customer, using the MAF extender and translator plus. Bob's customer service and product support (fixing it when I did a dumb thing during my translator plus install) are first class No disappointments here.

In a related, but new direction....I know informed old timers conclude that our cars do not need a BOV. Could a BOV absorb the peak compressor surges in this case and serve as a wastegate of sorts to protect the compressor bearings and other components of the supercharger system from premature failure?

 

[TurboBob]

Re: What would Tonto say?

Originally posted by lburou
............... Could a BOV absorb the peak compressor surges in this case and serve as a wastegate of sorts to protect the compressor bearings and other components of the supercharger system from premature failure?

Generally, a closed loop bov can lessen part throttle surge.

This case is different, the DS files show a very chattery MAF signal even at WOT. The dropout filter in the extender chip is masking the bad MAF signal at WOT which explains why it runs better at WOT.

Bob

 

[Grandnat]

I am going to have to second what UNGN is saying.

This is very common. It happened to me ALOT when I had the TE44 and a FMIC. Once I went to a PT54 this problem went away.

It is simply compressor surge. Probably no real need to look any further.


the car is not designed to see that kind of boost when the throttle blade is just cracked (cruise conditions.)

and the larger the intercooler volume, the more it exacerbates the problem (more area to compress air.)


the MAF problem Turbobob is talking about might be a seperate issue.......but maybe not.

just throwing in my 2 cents.

 

[UNGN]

Originally posted by alb84
At part throttle the WG is not welded closed, it is modulated by the selenoid and ecu. A weak selenoid could cause the same kind of problem. If you look at the after market boost controllers you will see that they have some major ecu brain power dedicated just to the modulation of the WG selenoid. Oh well, Just wanted to give you some ideas on things to check. Later....Danny

No, the Wastegate IS welded closed at 8-10 psi boost if the rod is shortened to maintain 25 psi max boost. The Wastegate is opened by boost pressure. At boost pressures below those required to open the wastegate, the wastegate will remain closed, no matter what the ECU or the Wastegate solenoid are doing.

The Solenoid could be fully closed (max boost pressure to the wastegate) and the wastegate still won't open. Tighten Your wastegate to maintain 25 PSI Max boost, then cap the open barb on the solenoid to take the solenoid/ECU out of the equation.

You'll see how much above 8-10 psi it takes to open the wastegate.

If Boost was being controled by the ECU and the wastegate, he wouldn't have a flutter problem.

 

[boostcreep]

At part throttle, aren't you reading the *intake* manifold pressure, and doesn't the wastgate see the turbo output pressure? Just how much of a difference is there at part throttle? Is this something that's overlooked, or maybe I'm missing something?

Nick

 

[turbo buicks]

the psi drop across the i/c at stock boost is like 2-3 psi so at low flow rates and super low, part throttle boost the psi difference isnt much at all.

 

[boostcreep]

I'm talking about a partially closed throttle plate. Doesn't pose a significant restriction?

Nick

 

[UNGN]

Originally posted by boostcreep
I'm talking about a partially closed throttle plate. Doesn't pose a significant restriction?

Nick

Yes it does. And if his boost was set at 15 or even 20 psi, the wastegate would open a little when the throttle blade closed and reduce the flutter.

This is why it won't flutter on the highway at reasonable max boost levels and small thottle openings/partial boost.

With the Boost set at 25 psi, the wastegate will not be opening in part throttle situations.

 

[boostcreep]

So if your are seeing 8 to 10 intake psi at part throttle, just exactly how much boost is the turbo putting out. I try to keep notes on this kind of stuff and this would be a nice addition.

Nick

 

[TurboBob]

Originally posted by boostcreep
At part throttle, aren't you reading the *intake* manifold pressure, and doesn't the wastgate see the turbo output pressure? Just how much of a difference is there at part throttle? Is this something that's overlooked, or maybe I'm missing something?

Nick

This is the exact condition of part throttle surge.

The wastegate is connected to the compressor.
Your boost gauge is connected to the intake manifold.

you can have 8 psi in the intake, a slightly opened throttle, and 25 psi in the turbo+intercooler+up-pipe.

Depending on lots of things, (intercooler,turbo,whatever) this situation of high pressure (25 psi in the turbo) and low flow (throttle partially opened) will cause surge.

Now, if the wastegate/solenoid/whatever is set lower, you will get 8 psi in the intake (controlled by your foot), and less pressure in the turbo/intercooler/up-pipe. Once you have the wastegate set low enough, the surging will stop.

But, Razor's friend's car has a DIFFERENT problem, since the surging / spiky MAF signal is still there at WOT.

I'm done talking now.

B

(I think the laws of physics are unfair, and I'm going to sue!)

 

[y-hate]

Check his muffler bearings

 

[alb84]

Yes of course you are absolutly right. You have the files and the knowlege to say. I was just enjoying the spirited discussion on waste gate theory while waiting for another MAF to be tried. I will respectfully back away from the subject, as I would not want it to turn into an argument of any kind. I hope the flutter problem is corrected soon. Later.....Danny

 

[Razor]

Originally posted by y-hate
Check his muffler bearings

We did those..the headlamp blinker fluid was also topped off, the kneuter valve tightened, and the glass packs shortened.

Actually it turned out to be the NUT behind the wheel

 

[Razor]

And a new q-tip filter added to the alky container

hehehe.. touche