Fluttering at 8-10 PSI

[Razor]

Try to help a bud out.. car has a TE44, THDP integral, 50's, ext, LT1 MAF w/translator, 65 MM TB, etc.

Problem is if you hold the boost at 8-10 PSI, the engine sputters..like pops.. At WOT 25 PSI it runs perfect. At idle/vacuum driving it runs perfect as well. BL's are normal and within normal ranges. Doesnt knock retard either.

My first suspicion was a bad wastegate. He replaced the actuator with a HD one, still same problem. Runs recorded on DS show the MAF and Load dropping out big time when it exhibits the problem.

Does this with or without the alky. So its not an alky issue. Thought i'd add that as well. Disconnected the alky and still at 8-10 PSI flutters.

What other things could cuase this other than MAF/chip/electronics.

Havent tried replacing the MAF with a GM one and regular chip yet.. trying to see if its something else so he doesnt have to drive 50 miles to get here.

Hows that..hummm

Thx..

Julio

 

[TurboBob]

send me a DS file

bob [at] bailey [dash] eng [dot] com

 

[Razor]

Sending ya the kitchen sink

Thx..

Julio

 

[turbo buicks]

julio, back when i was 10 psi limited for like 6 months i tried everything but it would still miss and sputter anyhting over 10 psi. replaced coil pack/ign module with a red regal special and BAM it worked.

 

[UNGN]

Are you sure it isn't compressor slam?

You aren't supposed to hold 8-10 psi with a wastegate setting of 25 psi. This is an unstable flow regime caused by a partially open throttle blade and a turbo trying to spool to 25 psi of boost.

Does it sputter or does it go wham, wham, wham, surging violently?

 

[TurboBob]

it's not part throttle surge, your MAF signal is bouncing badly even at WOT.

At WOT the anti-dropout software is covering up the symptom.

There is something else afoot.

Look for bad/loose hoses, plug wire, ground wire, ignition components......

Bob

 

[turbo buicks]

i highly doubt a 44 would surge at part throttle at any boost. i can hold my 49 on the hiway in OD at like 5 psi with abrely any gas and it wont surge. now a T-70, thats a whole nother story.

 

[UNGN]

Originally posted by turbo buicks
i highly doubt a 44 would surge at part throttle at any boost. i can hold my 49 on the hiway in OD at like 5 psi with abrely any gas and it wont surge. now a T-70, thats a whole nother story.

With my TA49 set on 23 psi, trying to hold 8-10 psi will shake me out of the car. Pretty embarassing when trying not to "waste too much gas" when a honda challenges me to a highway race. I just let them go.

 

[turbo buicks]

do you have heads/cam/FM, etc? whats ur mods?

 

[UNGN]

Originally posted by turbo buicks
do you have heads/cam/FM, etc? whats ur mods?

Stock, Stock, Stock intercooler with a neck, TA49/bluetops. Car ran 11.50's@118 before and after surging so nothing was wrong with the car

 

[turbo buicks]

haha oh well maybe ur cars just weird. mine dont flutter.

 

[KillrV6]

im willing to bet on the cp/ign modual

ive had it happen to me on my past two cars, happens fairly comonly

 

[TurboBob]

part throttle surge is common, but is dependent on car and combination. There are ways to reduce or eliminate it.

But,

THIS car (Razor's friend) may or may not have part throttle surge, but it IS experiencing surge/crap/wierdness/whatever at FULL THROTTLE. Its in the DS files.

Time to dig further.

B
(and that's all I have to say about that.... F. Gump)

Turbo is as Turbo does.

 

[TylerDurden]

this sounds EXACTLY like what i have, which is known as compressor surge (or slam), its caused like someone said earlier, throttle body partially open but the comp is trying to push more air thru than the engine can handle so the solonoid pulls boost and everything catches up with itself, and repeat....mine does it 3-5 times a second at part throttle,
one thing that i have heard that can fix it possibly is electronic boost controllers but i dont know that for sure,
for anyone who needs/wants more info or a better explanation call john craig at limit engineering, he will explain it to you, and btw
IT IS VERY COMMON ON TE44'S like the one i have....

 

[83ttypecooled]

10 psi miss

Have you checked the tps? Is it possible you have a dead spot in the potentiometer? Just an idea.......

Dale

 

[vitaman2]

coil pack/module is brand new-tps is brand new, replaced all silcone hoses & vaccum lines, spark plug wires are brand new- flutters badly when trying to run @ 8-10lbs of boost, WOT is fine, even put hercules tension on wastegate via actuator rod & also ran vaccum hose only from actuator to compressor & still have same problem- very annoying!!, is this problematic w/te-44's??

 

[Razor]

Originally posted by KillrV6
im willing to bet on the cp/ign modual

ive had it happen to me on my past two cars, happens fairly comonly

Could be, but WOT is working 100 percent. If it was popping..then I would have looked for electrical.. I doubt that a bad plug/wire would have an issue at 8 PSI and not 25 PSI. When its electrical, it happens at all loads.

TPS stays rock steady, you can see that on the DS recording stays constant. Doesnt drop out.

Yes on the wham wham wham. Feels like its losing pressure then getting it. Like when you blow off an IC hose but then reconnect it. Actually pretty violent.

Bob.. thanks.. dunno bout the dropouts. It happens to work that way..pretty strange. At first I thought may have been alky since we just noticed it after starting to tune the car. But killing power to the whole setup, and the droputs continuing... dunno. I will try and see if a GM MAF and generic 50lb chip changes readings. Only way I know to test those things.easily anyways.

Will try and do some more diagnostics on the dropout issue. Dunno if its related.

Another thing that had occured to me was EGR possibly fluttering, but its blocked off in the intake..so..

 

[Razor]

Originally posted by UNGN
Are you sure it isn't compressor slam?

You aren't supposed to hold 8-10 psi with a wastegate setting of 25 psi. This is an unstable flow regime caused by a partially open throttle blade and a turbo trying to spool to 25 psi of boost.

Does it sputter or does it go wham, wham, wham, surging violently?

It feels like what your describing, but I have been in a multitude of Buicks with these turbo's using stretch and FM IC's and never experienced this. My car with a PT51 you can hold it at any PSI without issue.. more diagnostics to follow..maybe a call to limit??

Thanks..

 

[TurboBob]

not to repeat myself, but....

Originally posted by TurboBob
THIS car (Razor's friend) may or may not have part throttle surge, but it IS experiencing surge/crap/wierdness/whatever at FULL THROTTLE. Its in the DS files.

The reason it's pulling ok at full throttle is the anti-dropout filter in the Extender activates at about 3/4 throttle and is smoothing the fuel & spark.

It could be the ignition system, funky MAF, air filter/hose sucking flat, intercooler hoseclamp loose, or ....

perhaps undoing/re-doing the last mod would be prudent....

Bob

 

[Razor]

Originally posted by TurboBob

It could be the ignition system, funky MAF, air filter/hose sucking flat, intercooler hoseclamp loose, or ....

perhaps undoing/re-doing the last mod would be prudent....

Bob

Bob the whole car is a mod .. that would definetely cure all..

I'm suspecting MAF, the IC hoses and clamps are all new. If there were to be a leak/loose one..it wouldnt go to 25 PSI. boost at 25 is rock steady.

Another thing is unhooking the plug from the alternator and testing to make sure its not some garbage coming from the charging circuit. Run the car on straight battery at 8-10 PSI and see what happens. Swap coil pack ign module, and the air filter setup on the car is a solid Pipe with a K&N going to a Kenne-Bell ramair thingy.

Plugs are new, the denso iridiums..

Anyone know a good witch doctor , or exorcist

I'll post what I find.

Looks like more diagnostics needed.. oh well..

Julio