Boost rises then falls? October 03, 2009, 10:22:25 AM What I have:1988 Thunderbird Turbo Coupe5-speedStock IHI TurboGillis Valve3" ExhaustBosch Bypass ValveWhat it does:When I floor it, boost rises with a corresponding increase in acceleration. Then, after it reaches a good 18psi (on the stock gauge), the boost then starts to fall. While boost falls, there is a corresponding decrease in the acceleration rate. If I adjust the Gillis lower, the boost rises and falls just as before, though the upper limit will be lower. I'm thinking that the wastegate doesn't close once it has been opened due to the pressure in the diaphragm not being able to bleed off. Any other thoughts? Where does the pressure in the wastegate diaphragm bleed off? Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #1 – October 03, 2009, 10:30:45 AM Not sure but i think the regular gillis is speced to around 18 or so psi.Gillis sells a higher pressure one that you may need with a stronger spring.You may also as you stated have a problem with your wastegate. Quote Selected
Boost rises then falls? Reply #2 – October 03, 2009, 11:24:17 AM There should be a bleed hole somewhere on the boost valve. I know on the DIY valves they specify a really small hole be drilled towards the outlet of the valve to bleed. Quote Selected
Boost rises then falls? Reply #3 – October 03, 2009, 11:53:47 AM Quote from: bhazard;293565There should be a bleed hole somewhere on the boost valve. I know on the DIY valves they specify a really small hole be drilled towards the outlet of the valve to bleed.I will take the valve off and have a look. Thanks!Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #4 – October 03, 2009, 12:25:23 PM Disconnect the Gillis and just jump the connections together on the turbo... If it still looses boost, at least you know it isn't the controller... Quote Selected
Boost rises then falls? Reply #5 – October 03, 2009, 12:34:43 PM Quote from: TurboCoupe50;293570Disconnect the Gillis and just jump the connections together on the turbo... If it still looses boost, at least you know it isn't the controller...Couldn't I blow something up this way? Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #6 – October 03, 2009, 01:07:45 PM Nahhh the boost MAY go up to around 18-19Lb, but won't be a issue unless it goes into detonation... I ran mine that way before I installed the 5.0, but because it was a automatic and had the fast bleed fitting on the turbo, still only made about 12psi(did 8psi prior)... We also ran the daughters 5 speed this way for a couple years and it'd make 17-18 Lb, would hit the over boost buzzer quite regularly... Quote Selected
New Problem! Reply #7 – October 03, 2009, 08:24:56 PM Ok, seems the hole in the Gillis (and I am assuming it was a genuine Gillis as it came with the car) was about 1/32. I enlarged it to 1/16, and the boost problem is solved. It now holds boost quite nicely.On to my new problem! It breaks down at higher RPMs under full boost. Back off to approximately 3/4 throttle, and it runs fine. As I have just recently tuned it, and I am experiencing no pinging, I am thinking it is the coil not putting out enough current to fire the plugs at high boost.Any recommendations on a coil?Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #8 – October 03, 2009, 09:03:05 PM Try a lower plug gap first? Quote Selected
Boost rises then falls? Reply #9 – October 03, 2009, 09:10:38 PM Quote from: bhazard;293604Try a lower plug gap first?I think I'll change the plugs as the ones I put in it are fancy-schmancy platinums, and cannot be re-gaped. As the coil looks original however, I would like to replace that as well. I was thinking of using a MSD# 8227 "Blaster TFI" coil. Anyone had any experience with these?Other than this little problem, it runs like a top, and handles quite nicely. I cannot believe I've never owned a Turbo Coupe before now that I know what I've been missing! :burnout:Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #10 – October 03, 2009, 10:14:59 PM I have a tfi coil on my 5.0L and it works well.Really sounds like a plug gap issue though.You may also want to look into an msd ignition(not as the problem,but an upgrade). Quote Selected
Boost rises then falls? Reply #11 – October 04, 2009, 09:30:48 AM If it has the stock fuel pump and over 80K mi, you may be running out of fuel due to a weak pump... When I was buying and selling TCs regularly, the pumps were my #1 problem... Quote Selected
Boost rises then falls? Reply #12 – October 04, 2009, 04:56:22 PM Ok, replaced the coil and the plugs, and now it goes like hell! It does run a hint rougher at idle however. I gaped the plugs at .026, so I may move them up to .030 and see if that helps.Thanks Guys!Shiny Side Up!Bill Quote Selected
Boost rises then falls? Reply #13 – October 04, 2009, 06:11:21 PM Throw those platinum plugs in the garbageno place in a turbo motor they cause problems. Quote Selected
Boost rises then falls? Reply #14 – October 04, 2009, 06:41:51 PM Quote from: SLEEPER T-BIRD 87;293672Throw those platinum plugs in the garbageno place in a turbo motor they cause problems.Which seems very odd to me... but I cannot argue with what I observe, and replacing them with Motorcraft Copper plugs definitely eliminated my problem.I do think I will re-gap the Motorcrafts to .030 and see if that improves the idle.Shiny Side Up!Bill Quote Selected
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