I am running a Vortech Mondo Race valve. There was no issue with the BO valve until I swapped to the MB throttle body.

When the rain lets up, I will swap TBs and see if this helps. Pretty clearly the BO valve adjustments are not helping. I hope the other MB works, as I hate to give up on the larger TB all together.

I have some work to do on my end before I can accurately say it is the MB or something else. Thanks for trying to help.
Aaron

 

I remember telling John Meaney that I had bought a mono blade from ASM; and, he made the comment that he didn't care for them. It seems like lots of people (at least in this board, including myself) have had problems with them. Something I didn't think about... but maybe the 58mm is best under boosted conditions since it has support in the middle of the shaft between the butterflies. The monoblade has a pretty long shaft that may be more prone to bending with boosted applications. Just a thought.

 

I think your on to something, Tony. force = pressure * area.
say it has 10 square inches of throttle bore. Slam the throttle shut on 20 psi and there is 200lbs of force on a 8mm throttle shaft, Until the BOV alleviates it. For that instant there's pretty good force on it, Perhaps enough to wedge it in the bore.

 

BTF,
Yes, I understand the boost situation. But... this occurs at barely any throttle with vacuum in the intake tract.

Well I spoke with AS&M, and they suggested the MONSTER return spring. Huh????

I swapped MBs today with a spare MB. It seems to not stick as much down low, but hangs at WOT. I mashed the throttle in 2nd at 1800 with the datalogger recording. Instant tirespin, let out of the throttle at 4K, but the engine just hung there and actually climbed to 5K before I hit 3rd. Then it blew the lower hose at 10 psi. This sh&% is getting old!

I am boxing the powdercoated MB up to send to AS&M. They are going to change the bushings and verify that the shaft is straight. They said turn-around is less than 1wk. In the meantime, I am going to put a large throttle spring between the throttle lever and the throttle cable bracket. Hopefully, this will at least solve the part throttle sticking issue with the spare MB.

Not sure what I can do about the full throttle issue. The MB is ~11.25 in2, while the old 58 billets that have not been an issue are ~7.95 in2. The force acting on the blade is roughly 40% greater with the MB. I am thinking this may be more of an issue with flexing of the "smallish" throttle shaft.

Tony,
How much boost are you pushing against the throttle blade? And you are having no issue?

Thanks for all of the input guys.
Aaron

 

So far I have run 15 or so PSI. The thing that made the difference for me is simply backing off of the bypass valve. I had the same problem as you (scared the heck out of me). I would check to make sure that you do not have a crack in your bypass line (is the manifold vacuum able to hold the bypass valve open at idle?), check your bypass diaphram (does it have a crack?). Take a look at your fuel pressure regulator.. are you getting a fuel referenced pressure as boost rises? You've definately got a back pressure problem in the manifold. I'm sure you monoblade isn't helping the situation any, but mine caught itself a few times (and I have the stained pants to prove it!) and it still seems to be working fine. Start over and check every detail. I guarantee you it is something small you are overlooking. Do you have your ECU set up to trim out the fuel immediately upon letting out of the throttle? Do you have your fuel tables set properly so you are not dumping too much fuel as the rpms rise... Check your data log to make sure in fact your throttle blades are in fact staying open (Sticking) for a brief moment. I'm not trying to be a pain, just work shopping a few random ideas..... Good Luck!!!!

 

AS&M has received and replaced the bushings on my powdercoated MB. They felt that replacing the throttle shaft bushings was unnecessary, but did it anyways due to my problems that I had experienced.

They did say that in high vacuum situations that the MB have shown a tendancy to "hang" open. I installed my spare MB (painted unit) with an external throttle return spring. It hangs open just as before. But... I did notice in response to another post on this board that I steadily pull 22-25" Hg when the throttle is snapped shut. I believe this may be part of the issue (very high vacuum). The throttle still takes ~6/10 of a second to return to 19% throttle position (idle setting).

I would suppose that my next step will be to move to one of my old billet twins. I would expect that all problems would be gone with the MB removed.

I just do not understand how others have been able to make this work. My BO valve is working because it instantly drop psi in the intake tract when the throttle starts to close. Unfortunately, that is a few tenths of a second after the throttle is released.

How much vacuum are you guys running MBs seeing at part throttle and when you quickly slam the throttle shut?

Any other ideas are welcomed. This still sucks!

Aaron

 

I only run 10 Hg at idle... I had to install a remote vacuum canister.

 

Steady 15" Hg at 875 RPM (17"-19" Hg at cruise of 1600-1900 RPM) . Ample vacuum for the brakes and everything else. This cam with just over 0.650" lift and 246/254 duration at 0.050" is amazingly well mannered. But it also pulls well past 6500.

I am thinking that today I may add a 2nd BO valve (w/ a 2nd vacuum feed nipple just aft of the TB) to see if I am just not relieving enough psi. I do know that at idle, there is a serious amount of air coming out of the 1.5" line (ducted right in front of the passenger front wheel, like a yard blower at idle when someone gets near). Maybe I just do not have enough volume releif.

The thing that puzzles me is that all of this (TB, BO valve, etc) worked prior to swapping to the C4SP intake and the MB.

Aaron

 

I wouldn't do that if I were you. I had the exact same thoughts of doing this when mine was acting up. There are guys making over 2000 hp that only have one of the large Procharger Race Bypass valves. If the Mondo you are running is anywhere near that capacity I think it is ok. I think your problen is elsewhere..

 

Oops, too late. I installed a 2nd BO valve in the downpipe off the compressor. This unit is the Vortech MaxRace valve.

One thing I did do different, is I pulled the upper half of the intake and drilled and tapped another nipple (5/16"HB x 1/8" NPT). I ran a direct 5/16" line to the new BO valve.

I also tightened the outer spring on the MB by one full turn. That baby snaps shut now. I will finish reinstalling the ducting and find out if this has made a difference.

My budy running the 8.90 LT1 Camaro was running twin Mondo's on his 1200HP ProCharged 383. He said it would not vent enough on the single and was causing compressor wheel shutter.

I will definitely let you know. I hate for the car not to be driveable. I missed an arranged meeting with a SC'ed Z06 last weekend due to this crap.

Aaron

 

Aaron,

Let me know it that works and I might just put another on my car just to be safe...I suppose it doesn't hurt anything to have two.. maybe just overkill in some cases...

 

&^%$%^&*#$

This is getting so old! Both BO valves are working. The throttle seems not to stick so bad at part throttle conditions, but still hangs wide open when you are above 4K. Next step is to go back to the billet 58 twins.

I suppose if this works, then I will have to seriously re-evaluate the intake configuration that I am currently running. I will probably look at one of the 90MM units and see about making a new transition from the 4BBL intake to the 90MM TB. I think sloRvette is running one of these.

I am so disheartened with this project. Today is my 38th, and I had really high hopes that these changes would fix the problem. Oh well, had a good dinner with the family and fixing to have cake.

Tomorrow is a new day!

Thanks for all of the help along the way.

Aaron

 

I have similar part throttle issues with my arizona speed and marine tb. When I'm cruising for any sustained period on the freeway or around town, when I let off the gas then it stays at speed like cruise control. I don't notice the full throttle thing too much because I have an auto. But since my car is meant to be driven whenever possible, the part throttle thing is irritating and a hazard. I'll have to take a look at it this weekend and see if the possible fixes make more sense. I'm only running a "puny" s trim and it's not even spinning hard when I"m cruising at part throttle. I also have the mini race bypass valve from vortech.

 

Sounds like the makings of a good class action lawsuit......

 

if they would just fix it i'd be happy. How much did it cost to get serviced?

 

If you are speaking of replacing the bushings, that was supposed to cost $40. But they are talking about doing it under warranty. I have no thoughts that this will fix the issue, as I am currently running a second unit that has not been powder coated. Brand spanking new. I would bet this would be a problem NA as well, pretty much anything that draws decent vacuum.

I just do not understand how anyone is making them work. Tony, you are still running the MB? You were running the MB for the past 1000 miles with no issues? If you (and others) are able to make the MB work, that kind of negates a CA lawsuit.

If this is a design defect, I will definitely go back after AS&M. I gave them full disclosure on the details of my combo when I bought the MB, and they said it would work fine. They had no issue charging me for the MB.

Tomorrow, I will be swapping to the billet 58MM with all intents of having full driveability returned. I will keep the group informed.

Aaron

 

Is there anyone who has been able to make the MB work? If so, please provide high level details of the package (i.e. F/I or na, intake, ~RWHP, and vacuum at idle/cruise/and rapid deceleration.

Thanks in advance,
Aaron

 

Have you checked over your throttle follower settings ? Any chance the IAC is sticking in the TB ?

 

Mine did not work until I fixed the throttle plate as described in one of our other threads. After I backed off on my blow off valve I've not had any problems.......yet...

 

Yes, you can see in the FAST data logs that it takes 5-6 tenths of a sec for the throttle to close at lower RPM, and at higher RPM, the throttle will close slightly, but pretty much just "hangs".

That is one of the great things about logging is that you can see what is actually happening vs guessing based on "feel".

Aaron