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Author
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Topic: Supercharger questions
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cheap
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Member # 858
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posted
 
 
Ok, just got the SC on a little bit ago and just finally started to romp on it a bit, and I have a few questions about things I noticed.
First off: I have a pretty bad surging problem when Im in first and second gear, especially it seems when the car hasn't warmed up yet. Im talkin BAD. Any thoughts?
Second: When I exit the freeway, I have to downshift or else my car will straight-up die on me. It's happened twice now, the two times I DIDNT downshift. I tested it out and the same thing happens when I am cruising at freeway speeds and put the car in neutral. Only happens at freeway speeds, though...
Third: My SC is a Vortech, which I know is a centrifugal supercharger. The unit makes boost based on being spun by the crank. Well the question is this - I don't see boost unless I floor it, which obviously doesn't increase RPMs right away, especially in 4th and 5th. The SC isn't spinning faster right away, so how come the boost shoots up quicker? Im guessing it has to do with the vacuum line connected to my blowoff valve, but how does the vacuum system read more suction when I floor the gas as opposed to when it's at 3/4 throttle, and at what point does the system decide that I am indeed at full throttle and close the blowoff valve?
Fourth: How can I tell if Im detonating when I already have a valve ticking, and a loud-ass stereo and exhaust on top of that? Any other indications other than audio?
Fifth: Will my engine run lean if I am at 4k RPMs and put it in neutral because I instantly lose my boost and go to vacuum? Is it like a momentary thing, nothing to worry about, because the blowoff valve is opening and will reduce the amount of air goin into the engine?
Thanks for any input, I'll be checking back here tomorrow afternoonish to see if any of ya know wtf is wrong with my shizzle
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1965 Spyder GT
Posts: 1358 | From: Maine | Registered: Feb 2002
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91GR40LX
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Member # 1329
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posted
Check to make sure all of your hose clamps are tightened down. It sounds like your not getting a proper reading to your computer from your MAF because air is bleeding off somewhere. A leak before or after supercharger will cause some of your symptoms.
Your bypass valve is held open by vacuum. Once you have positive pressure(acceleration) it closes to build boost in the engine.
What MAF are you running?
Posts: 340 | From: East Bay | Registered: May 2002
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cheap
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Member # 858
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posted
I've got an 80mm Pro-M. I might have a leak where the maf is mounted to the inlet ducting, because i had to ghetto fab up an adapter for my big maf. I will probably just wrap up the joint with saran wrap and a couple of zip ties, to try to make a better seal. Thanks for the idea.
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1965 Spyder GT
Posts: 1358 | From: Maine | Registered: Feb 2002
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UNLUCKIER
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Member # 435
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F4 Tape !! You KNow where you can get it ![[Wink]](wink.gif)
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The great pleasure in life is doing what people say you cannot do.
AND YES THE RAMS FAN
Posts: 1023 | From: ODENTON MD | Registered: Sep 2001
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Member # 858
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posted
Heh now that u mention it, I have the GOOD stuff - Speedtape...
Posts: 1358 | From: Maine | Registered: Feb 2002
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JohnB
Tech Moderator
Member # 969
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posted
Cheap- here's my view on the problem. It's cuz you've got a V6..j/k! Anyways, here's my thoughts..
First: the surging is because it's still got the stock parameters in the computer. I suggest a tune ASAP on the car. The cam you have coupled with the SC is causin' all sorts of havoc on the stock computer. It's probably confused as f%ck right now. Also, you may need to "index" (rotate) the MAF to where it runs the best. I've been playin' with Robs 347 doing this...it is crazy what a lil air turbulance does to the MAF. I guess I got lucky the first time with the Cobra..
Second: sounds like the bypass valve is hooked up to a seriously strong vac supply...OR...the MAF is causing it. Elwin had a problem similar to this...that was the prob. Does the car exhibit a seriously rich condition when it does it? Or just flat dies? If it's seriously rich..the FMU could be to blame. Have the correct Cal kit in it?
Third: my only guess..your vac line is downstream of the throttle body. You're only going to read as much boost as what's in the engine..ie..the throttle is open.
Forth: turn your stereo down and get the valve fixed. You'll know then. ![[patriot]](graemlins/patriot.gif)
Fifth: in a perfect world, it'll never happen- that's what the FMU is for. Also, you have plenty of injector, I don't see lean being an issue. If anything, I'd think you're a lil on the fat side..36's are alot for a 6. ![[Whoo Whooooo!]](graemlins/woowoo.gif)
Like I told ya earlier, disconnect the vac...put it at the discharge. Let it read straight boost. disconnect the FMU vac. Take it out for a spin... ![[Big Grin]](biggrin.gif)
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Member # 858
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posted
John -
First: I do have a chip, that is supposed to be tuned for my cam and everything, but it hasn't been dyno tuned for complete accuracy yet. Im waitin on Fordchip to come out here on the 26th (?) of April. Is your MAF sticking directly into the airstream like mine? If so, I wanna see how you indexed yours, and I'll try to rotate mine accordingly. I still gotta wrap the connections with saran wrap, but at least the car is in Davis now *in my GARAGE* so I can get started on that and the motor teardown, again... ![[Frown]](frown.gif)
Second and Third: Yes, my vacuum line is spliced downstream of my TB. Good thinking, that didn't even cross my mind. Won't I want to leave it there for my FMU, Bybass valve, and BTM?? I'd think it would be better for those to read how much boost is actually getting into the engine.
Fourth: I can't turn down my stereo!!! I've missed it soooo much lately! (Even tho the piece of shit keeps cutting out on me... ![[Mad]](mad.gif) )
Fifth: Good.
The car is done now for a while, I wanna try to get those heads up to Yuba City before my leave ends. Im gonna shoot Mikael an email to see if he has another set he can swap me one-for-one with, but I kinda doubt it since those heads have $600 worth of machine work into them, plus the porting on top of that.
Thanks for the input. Oh, lemme know when you're free next so we can move my tools from Bill's garage up to Davis.
Posts: 1358 | From: Maine | Registered: Feb 2002
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JohnB
Tech Moderator
Member # 969
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posted
The MAF on the Cobra is actually REALLY far downstream of the filter. I've seen so many probs with turbulance, mines literally right on the inner fender- with an elbow extension on it that goes to the filter..which is at the bottom of the front bumper. Take a look at it the next time the car is at work.
As for the vaccum issue, I'd say the closer to the manifold, the better. Lower than the upper plenum though..
Lemme know when you need to move them (tools). I'm probably going to have a short day sometime this week...if not a whole one off...or a day after work, you know my schedule
[ March 31, 2003, 05:19 PM: Message edited by: JohnB ]
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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PumaFiveOh
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Member # 2322
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Just wanted to say that you seem kind of confused on what the propose of the BOV is. It does not stay open to relieve boost or let pressure out while you are under boost. I think you are thinking of a Waste Gate on a turbocharged system.
The BOV usually has a vacuum line which runs to the intake manifold and the pressure actually keeps the BOV closed, not open as you thought. When you let off the gas....the TB closes and all of a sudden the pressurized air is stuck in the intake pipe and has nowhere to go, so at that point the BOV opens and relieves the pressure instead of it getting pushed back into the blower and slowing it down....which could cause un-needed pressure on the blower and it's bearings.
Also if the BOV is stuck open or leaking you could have issues, make sure you do not have any intake leaks. If you have any intake leaks the MAF is losing air counts and could cause it to die or just run like sh!t.
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"Pain is temporary, Pride is forever!"
"The object of war is not to die for your country, but to make the other bastard die for his."
-Patton
Posts: 718 | From: Bay Area! | Registered: Jan 2003
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