Boost could only be holding it open if there is a pressure difference....there wont be when its open because pressure is equal across the blade. When it goes to close there will be aerodynamic lift generated on the blade creating a moment trying to keep it open, but this should be far less than the moment of the spring trying to close it. Have you adjusted it in any way? I think chris is right and if it is opening the full 90* it could stick inside the tb. The difference in area of being opened 85 degrees versus 90 degress is only 0.4%

 

Hmmmm... well, like I said, it's a POTZ ported TB, with the little tab cut out. Their ad says, "Bump stop cut for a fully open throttle blade at wide-open-throttle." See Picture below....



As you can see, next to her right.... uhhh, thumb... it's notched to let it open more. I wonder if a quick 10x wrap of electrical tape around her bump stop would tell me if that's the problem....

Probably a good thing for NA where there's vacuum, but not so good for FI... hmmmm. Will try wrapping it tonight.

But wait, I don't think my friend's TB bump stop was cut. Will have to ask him.

 

I was going to ask if you did the bumpstop mod, btw i see no tb in the above pic!

 

Hahaha... I thought you guys would enjoy that. What were we talking about again?

I'm going to wrap the bump stop and maybe tighten the spring. The wire spring on the POTZ TB is a little thinner, not necessarily lighter, but maybe tightening it up a wrap or two will help.

 

was she an escort at one time in vegas. please just answer me that.

 

Hey Fella! That's my wife!


(Hahaha.. Just kidding! Don't I wish I had access to that!)


UPDATE: Just txted friend. His TB is all stock, not ported, no bump stop mods, etc. When we swapped his on last night, it still did it.

 

Hmmmm.....

Did you try removing a piece of piping or removing a coupler to see if the problem stops?

 

get it on a dyno with HPT so you can safely play with it.

 

Yeah, that's the next step. Otherwise, I'm out of ideas... other than get the BOV back on.

Dyno too... eventually.

 

My idle air control valve was causing this same concern when it went bad. try unplugging the TPS and idle air sensor on TB...turn the key to on position for about 30 sec, turn off and plug the stuff back in.

 

Throttle body blade is probably opening more than 90 degrees and being held open by all the velocity of the air moving through it.

 

I did not read all the comments in here but I can assure you its your lack of a bov
I had the same exact ussue when my bov took a crap on me for about 2 sec the throttle would stay wot

Not very fun when you a twisty tight canyon

 

do you have any holes in your carpet under the pedal? you never know

 

This is one of the largest misconceptions in the world of turbos , running w/o a bov will have minimal effect to a turbo, almost every race car or factory produced turbo car did not have bovs instill the early 90s when maf sensor became put into use , in which compressor surge would cause the maf to freak out causing fuel management issues
Go look under the hood of a grand national and see for yourself

 

Will try to get the BOV back on this weekend. Also, no carpet issues. Checked that already. Also removed the floor mat to rule that out.

Will let you know how things go once the BOV goes back on.

Thanks for the input guys. Not a lot of fun when you can't stop when you want to.

 

If you can reproduce it, a quick log file on the laptop will show us what the computer see's.

 

Hey Joe... good idea, lets get together this weekend and see if we can do that, before I put the BOV back on. Data = knowledge.

 

It ended up being the black cruise control throttle union piece @ the battery. When the car built boost the pipe was flexing and hitting the black casing, the cable guide is mostly circular but there is a part that is slightly flat that was getting bound up. Upon dissemblance, we could actually see a slight groove in the plastic inside where it was hitting.

 

Yup. I have my methanol injection nozzle mounted right next to the cruise control module. That put pressure on the housing and pinched the housing to the "cam" of the cable assembly. Freakiest thing. One of those 1 in a million freak things. If I'd have mounted it 1/2 inches closer to the TB, it would have been a non issue. I'll get some pictures up soon. Thanks for your help too Joe. Appreciate it!