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Crap dyno numbers-car won't hold boost

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Old Oct 25, 2008 | 05:03 PM
  #31  
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did you read the review on those 9 cams from hks, because every review i read they didn't make that much power before and after.I'd do my own boost leak test, check the mbc and or put new zip ties hm..... and then go from there.
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Old Oct 25, 2008 | 05:22 PM
  #32  
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I doubt its the cams . I'm betting its a boost leak or the dyno reads really really low. But the tuner already said it won't hold boost sooooo.. Why did they only tune for 22psi?
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Old Oct 25, 2008 | 06:31 PM
  #33  
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Originally Posted by gsrboi80
Boost Leak. Could be an issue with the boost controller as well. ECU controlled boost really holds boost much better


be sure to t-bolt clamp the $hit out of everything. Like everyone said take some time and re-tighten all your hoses and check to see if the MBC was properly installed.

You may want to go ahead and install the the aperture throttle body seals. You can get them off of worksracing

I have mine sitting in my desk, been to lazy to install.

Good luck Broseph!!!

Last edited by huevosrancheros; Oct 25, 2008 at 06:36 PM.
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Old Oct 25, 2008 | 06:34 PM
  #34  
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From: lowell,MA
yea something fishey there check my sig out i did 320 on a mustang dyno u should deffiently be much higher than mine
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Old Oct 26, 2008 | 12:55 AM
  #35  
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Isn't the cobb dyno at 4000 + ft elevation as well?

Although I guess if they are saying the boost drop isn't normal there, then it isn't...
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Old Oct 26, 2008 | 01:37 AM
  #36  
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sounds like a boost leak to me as well.
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Old Oct 26, 2008 | 07:49 AM
  #37  
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From: Maryland
Originally Posted by speedypollard
well if you dont have an upgraded wastegate actuator then you wont be able to hold that much boost...duh...and why the hell did you spend $1600 on cams?! ARE YOU DUMB OR WHAT? LOL
sounds like your the one thats dumb. get out of here if you have no idea what your talking about..

you dont need a upraded wastegate actuator until you run higher boost. even then, you can usually controll it very well with a ebc. mbc's tend to drop off at high rpm's.

check to see if you have a boost leak. sounds like you do
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Old Oct 31, 2008 | 02:49 AM
  #38  
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Originally Posted by gdup
i had the same problem when i got my car tuned and it all went away when i changed my mbc. the car built boost better and didnt taper off as much. i had the exact same problem
What MBC did you have???
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Old Oct 31, 2008 | 02:52 AM
  #39  
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So Solid Auto Works (the cam installers) and Cobb talked and they don't think it's "acting" like a boost leak. They're thinking what some others have mentioned... that the actuator is the problem. I'm still gonna check for leaks. This is just depressing. So, check for leaks, then maybe replacing the actuator. Wish me luck.
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Old Nov 5, 2008 | 09:56 AM
  #40  
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From: Slc Utah aka SL,UT
Originally Posted by cheesehead713
I don't, but it seems pretty clear from the posts that I need to check for leaks. I'll pm the guy above to see how to do it.
Dude I'm 30-40min away from you. I'm not sure if you have a tactrix cable or not but I have one and can hook my laptop up to it and check it out for you as well as see what's going on with your car so pm me and I bet you paid a ****load for your cam install..I could've done that for you too. Anyway pm me
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Old Nov 5, 2008 | 10:40 AM
  #41  
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check for leaks and tighten the wga
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Old Nov 14, 2008 | 02:08 AM
  #42  
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UPDATE: Got back from Vegas last weekend. I did some more tuning and went to get the actuator put on. The tuner there did a baseline pull (on a mustang) and the car was at 258 whp. Suck! Anyway, he put on the actuator. It did hold boost a little better. We ruled out any boost leaks. Also, the MBC seemed good. he tuned me a little better and we got it up to 291 whp. Better, but still short of where I should be. He said that I was getting back pressure and he thought it could be a problem with the cat. Then, some other guys pull up after. They've got similar mods, but stock FMIC. Before the tune, they do a pull of 305! Damn I was pissed. What is wrong with my car! Well, today, I went to Tunex to see what they could see with my cat (Cobb high flow cat). Sure enough, they found that i was getting 3 psi back pressure and that's probably fighting the turbo like the guy in Vegas said. So, I put on the Cobb test pipe instead. Tunex found zero back pressure with the test pipe, so they concluded that the Cobb cat was hurting. I drove away and felt a huge difference. I'm off to Vegas again Saturday and we'll see how it does. I'm guessing that was the problem and I'll be around 320 whp on the dyno there. Wish me luck.
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Old Nov 14, 2008 | 12:34 PM
  #43  
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yea backpressure will kill your power

glad you found the problem. let us know what she puts down
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Old Nov 15, 2008 | 12:57 AM
  #44  
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From: over there
Do you still have the plastic DV?

Usually the stock plastic DV would be ur best bet for 22psi .. and has excellent drivability.

I had an issue with my car not boosting over 25psi even with my boost control (greddy profec) maxed out .. it would spike to 25 and at redline drop to 19psi.

Changed to aps twin vent and now at 25psi .. my boost drops to 23psi only!

swap with a friend a DV for the day..make sure its recirclated .. and see what happens..

with my plastic DV, even though i hit 25psi, i could not find a boost leak..that's one area you can check.
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Old Nov 15, 2008 | 01:08 AM
  #45  
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Originally Posted by cheesehead713
I asked about that. Cobb said that if it was a boost leak, the boost wouldn't hit 22 psi in the first place and it does. It hits 22 psi, but then drops steadily after 4500 rpm. I guess it's possible, but the Solid Auto Works that did the cams tested for leaks before the tune and they said they didn't find any.

I am sorry, but if Cobb told you that, that is just not true. A turbo can overspin to meet a boost target, so saying you don't have a boost leak because it hits 22 psi is not necessarily true. If you do have a boost leak, you could certainly hit 22 psi.

Now, if you were using a Cobb metallic cat, there shouldn't be that much back pressure...unless the cat was clogged (a pretty easy thing to see). Of course, a 100 cell cat can flow more but normally a metallic cat isn't a huge backpressure creator (compared to ceramic cats).

Last edited by Erik@MIL.SPEC; Nov 15, 2008 at 01:11 AM.
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