boost flutter

[rick13]

If I let boost increase gradually, no problem. Maximum boost (set at 15 psi by manual boost control) . She's a demon! However, when I punch it, boost spikes at around 14-16 psi, I experience some "flutter". I have shims on the way for stock waste gate. Any other thoughts?

[ERAU944]

when you say 'flutter' do you mean actual variations in boost, or just sound (like the wastegate is 'fluttering')?

i'm curious because i have some funky sounds happening as well...

[rick13]

Minor variations in boost with some hesitation. Wierd because when I "baby" the boost up and then nail it , all is good. And yeah, I'm thinkin waste gate.

[rick13]

2 stainless linsey racing shims on the way.

[rick13]

Oh, I forgot to mention. When the car reaches "full operating temp". The symptoms go away. That is another reason I think it is a weak waste gate. When she gets hot, the spring must expand, thereby making it more likely to hold boost. That's my theory anyway. Somebody back me up here

[rick13]

more data. 2nd gear 3500 rpm to 5000 rpm, full throttle: wouldn't hold 10psi. 4th or 5th gear 3000 to something reasonable: held 15psi no problem. very interesting. god i hope these shims do the trick. i know wastegate removal is tough work. oh, and temp isn't as relevent as i thought.

[rick13]

well i shimmed the waste gate with two lindsey stainless shims. plus or minus 3/16 of an inch. NO CHANGE. DAMN! so, i disconnected the vacuum line to the bypass valve (she started running a bit weird so i plugged the line). i was just curious. anyway, i went for a test drive, boost climbed slowly to 7psi...that was it but no flutter. so i turned up my boost, on the test drive i noticed boost went to super slowly to 10psi. at that point sympyoms returned...a bit of hesitation/flutter (but not as dramatic). HELP!

[ERAU944]

hmm... very strange. I honestly haven't played with taking the wastegate out yet, or really any other mods (all i have done is replace the recirculating valve with the billet aluminum one). I vaguely recall my roommate in college having similar sounds/issues with his 951, but he did shims/chip/MBC and it was a totally different beast, it made a bunch more power. i don't really recall having any issues after that, but then again he drove the car a lot more than i did ( i reall only borrowed it a few times and swore i wouldn't ever buy one because i'd get in so much trouble).

anyhow, i'm looking forward to someone else chiming in on this.

i'd ALSO like to hear what wasteage will BOLT ON with no mods and work well. i know there are several aftermarket ones available but i have no idea which to buy or how to hook it up...

[rick13]

strange it is. especially when you "slowly walk the boost up" it goes like a bat out of hell!

relevent mods:
some chips...8 years old (i forget which kind)
turbo compressor wheel upgrade, and "shaved turbine" (stock housings)
manual boost control
stainless headers
shimmed wastegate (just last night)
3 bar fuel pressure reg.
billet aluminum bypass valve

rebuilt motor

before the rebuild all was well. everything worked as it should, with each other. compatability is not an issue. at the time i was running 18psi with no problems.

[wild man]

Originally Posted by ERAU944

i'd ALSO like to hear what wasteage will BOLT ON with no mods and work well. i know there are several aftermarket ones available but i have no idea which to buy or how to hook it up...

The OBX dominator is a direct fit for the 4-bolt flange. But quality lags far behind tial, which does require adapters. I am currently running stock, but "might" consider going with the dominator, at a buck-30 for the done deal. But I'd like to hear from others how well it works & holds up first. Would anyone running one be willing to chime in?

[rick13]

i haven't gotten alot of feedback from ya'll so i'm guessing you need more info. here goes:

1. i tested throttle position sensor/switch, it checked out o.k. i made a small adjustment in order to hear "click" hopefully that fixes my "hanging" idle. i cleaned outside plug contacts.

2. i tested air flow meter. all values check o.k. i cleaned contacts inside and out.

3. cycling valve gave me a nice "click" when i put 9v battery to contacts. i read besides bypassing, that is the only way to check. i will bypass if neccasary.

4. if this doesn't work, then i'm thinking weak fuel pump (i just changed fuel filter)

5. bypass valve holds vacuum. it is a billet aluminum type. just a couple of years old. when i blow into side it doesn't leak. ( is there a better way to test bypass valve)

6. i have new fuel dampner, i got it because i saw fuel leak out of bottom. i never installed it because it never leaked again.

7. my "J" boot is old and brittle. it has cuts and scrapes ( noththing "through and through")i should probably replace. (or should a go with MAF ? ) there is a bit of play in 3/4 inch hose leading to idle control vavle. the 1/4 inch hose that leads to cycling valve has a bit of a crack, but it is not "through and through"

8. the shims in the wastegate had no effect.

9. i noticed a couple of my plug wires were pinched against head. perhaps they are shorting out?


i know there is much to check i just want to know if there is anything else i am missing. typing this is a bit of therapy and ya'lls input on whether or not i am on the right track would be much appreciated.

please read entire thread...i will keep posting with my progress (or lack there of )

[Pete R]

Any chance you got a batch of bad gas? Maybe it picks up a knock at wot and the ecu changes the timing (just a theory) I had a similar issue when I got my car, fortunately I was low on gas and filled up before I started messing with stuff. A fresh tank of gas fixed it for me.

[rick13]

Funny. I never cleaned my tank after sitting for a four year rebuild. I have heard of different additives (sea foam er something)? But come to think of it, it does perform properly on occasion. Maybe some water remover and some octane boost will do the trick. Probably couldn't hurt. Thank you. I hadn't thought of that. Please advise.

Rick

[wild man]

One thing that you might want to look into is the possibility of a boost leak. Make sure that all of your clamps are tight.

As for "should go with a MAF? ", unless lots more power is something that you do NOT wish to have, my "unanimous" answer is: DEFINATELY!

[chip18]

MAF is fine but...you need to fix what's wrong now before you start adding more parts! I believe
the Lindsey Dual port waste gate is a direct bolt on. Kinda pricy though,
maybe a used waste gate?

[rick13]

Well we have a winner! BAD GAS. Thank you, Pete R ! I put in a half gallon of Sea Foam, and voila. For two days I have been driving my engine clean. This morning on my way two work everything went perfectly. 14psi of Boost in 3rd gear. 16psi of boost in 4th gear, and 18 in 5th. (Lots of load).

The throttle position adjustment fixed my high "hanging idle".

Wow, This car is fast.

Thanks again to all of my fellow "pelies".

Smith out

[chip18]

Wow great find! Congrads!