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Only 9psi from 404 w/D1sc...NEED MOAR BOOST!

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Old 04-01-2010, 12:55 PM
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Default Only 9psi from 404 w/D1sc...NEED MOAR BOOST!

So I finally got everything up and running with my procharger build. Got it to the dyno last week. And it was only making right at 9.5psi of boost. It was only turned to 6k RPM the first pull, and second pull the clutch started slipping, as it was making a good bit more power from the first pull. Now if I take it on out to 6800 or so, I know it will make more boost but will it make a huge diffrence in power?

The pulley combo is the 3.4/7.65 with the stock tensioner setup and a super tight *** belt. There was no slip at all. Would it be possible to get a bigger crank pulley to make more boost? I know you can get custom blower pulleys, but from what I've seen it takes months to get them and hard to get a hold of the people to do it. Just seems like adding a crank pulley would be a lot easier as well lol.
Old 04-01-2010, 01:56 PM
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Wow, that seems low. Mine made 15 psi at 6600RPM with a 7.25 and a 3.2 pulley config. Are you sure the belt isn't slipping? I have free flowing exhaust and a good intake set-up with decent size cam.
Old 04-01-2010, 02:24 PM
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Do you have the "big" filter on there? It's well known that the small filter that comes with the kit costs a few pounds of boost. Also, do you have the 4.5" twin intercoolers?
Old 04-01-2010, 02:59 PM
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Sorry I didnt post everything I guess.

Motor is a ls2404 with 10.8:1 compression
Patriot stage 3 heads
FAST 92/92
Pat G 254/257 .621/.624 111+2
Kooks 1 7/8"-2" headers and kooks y-pipe with 4" outlet to a 4" mufflex. Pulls were made with cutout open
80lb injectors
Nasty N8 line and fitting kit
twin walbros
8 rib kit
Custom FMIC
stock procharger hat with big filter, but pull was made with no hat on at all.

I think thats all...I know I have a free flowing setup so I wasnt expecting to make 16psi. Its still making good power for only 9psi...very first pull and a way conservative tune, with 14* of timing it made 660hp/600tq at 6000 rpms. Next pull the tuner added some fuel and tweaked a little bit and it picked up a solid 40hp on the bottom, but it blew through the clutch and couldnt get any more good pulls in. I think it was on its way to 700 on the 9psi. Also I have meth installed but wasnt using it yet. Trying to get some baselines before I turned the meth on.

I'm almost 100% positive the belt wasnt slipping, because on the dyno graph it showed boost to hit 9psi and it stayed there until the end of the pull and never dropped.
Old 04-01-2010, 05:17 PM
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that cam ... i bet it has something to do
Old 04-01-2010, 05:36 PM
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Currently getting blown


LMFAO!!!
Old 04-01-2010, 07:36 PM
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+1 for the cam being the issue..
Old 04-01-2010, 08:04 PM
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Ummm I'm registering boost befor it enters the motor lol. Maybe I don't understand completely but how would the cam bleed off boost before it goes into the motor?

Also I've read that more overlap int actually all that bad.
Old 04-01-2010, 11:18 PM
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Boost PSI is just a measure of restriction. That cam has quite a bit of overlap and is bleeding boost pressure out. Switch the cam and I bet you'll pick up a bit of power. It may not make more "boost" but more of the CFM will remain in the cyls to make more power. Have you looked into the aster bracket or the SDCE setup? You could pulley down the blower and see where she goes from there. Try the 3.4 but remember to watch your blower rpm. Your setup is pretty efficient and flows well. Good numbers for only 14* on 9psi. I'd suggest one of the better brackets and pulley her down to a 3.4. Nice numbers though!!
Old 04-01-2010, 11:38 PM
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I'm goin to get the clutch fixed first and see where it goes from there. I think 700 will hold me over for a while. I'll swap it out one day...
Old 04-02-2010, 07:24 AM
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Originally Posted by blk00ss
Ummm I'm registering boost befor it enters the motor lol. Maybe I don't understand completely but how would the cam bleed off boost before it goes into the motor?

Also I've read that more overlap int actually all that bad.

I was under the assumption you need to reference boost from after the TB otherwise you wouldnt get a correct reading.
Old 04-02-2010, 08:07 AM
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Originally Posted by BIG_MIKE2005
I was under the assumption you need to reference boost from after the TB otherwise you wouldnt get a correct reading.
yes, that is typically how its done. Not sure when he says "before it enters the motor", means before the TB or before the valve?
Old 04-02-2010, 10:22 AM
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Before the vlaves. I am refrencing from the brake booster hose.
Old 04-02-2010, 11:10 AM
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Your cam has 33 degrees of overlap. My little emissions legal PatrickG cam made 620 on 9 psi. It has -8 degree overlap or as I like to call, under lap. So the cam might bleed off some boost, but you're still making really good power. I'd focus more on how much power you're making over how much boost.



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