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Discussion Starter · #1 ·
This weekend we played around with my buddy's car , he just got his RR 2.75 upper on, Diablosport Chip, and 100mm idler and 74.5 gates belt, he also has full bassani exhaust, Accufab T/B, and Amazon CAI. We took his car out and doing a 3rd gear pull the car will make 14 lbs or a hair over of boost but as soon as the tach hits a little over 5000 the boost starts to drop and eventually drops to a little over 12 at redline, we know he is not getting belt slip, so what else could it be, it seems as if the boost pressure is being bled off or something, its supposed to have the boost bypass incorporated in the chip, I dont have the aftermarket guage like my buddy does so I cant tell if mine does this. There has got to be a fix for this since I have heard people say that there car holds boost up top, either they are fibbing and their car does drop boost or I am missing something, whats the fix? Is the Nitrous Pete dump valve mod the same as the boost bypass mod or just unplugging the sensor??
 

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The Ubiquitous Jimmy V.
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You can pull plug..Use Pete's Bypass mod..(HE WELDS IT SHUT) Either way your 14lbs boost will be 12 at redline anyway...
 

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Discussion Starter · #3 ·
Then how do people like Harry (With his old 03 setup) claim to hold boost throughout? It seems several people say they can hold X amount of boost all the way thorugh while others say they are losing boost!! I am just confused I guess??
 

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The most anyone can hold all the way to 6K is 13lbs, 99% of the cars will start bleeding boost levels due to belt slip or whatever around 5500 from what I have seen. Lower pullies you are almost guaranteed some belt slip while uppers only dont see it as bad from my experiance. I have seen cars peg 18lbs at 4K but are back at 12lbs by 6K. THERE IS NO CURE (eatons only here)
 

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I'm with you. I'm not sure what the mod to the valve is supposed to do.

I had boost drop from day one. One of the first things I did was check out how this valve works. The valve is normally closed, as in when the car is off, the boost bypass valve is against a stop on the blower, in the position that prevents bypass. When the car is started the valve opens to the bypass position, it is pulled open by vacuum applied to a dashpot.
When under load, vacuum goes away, and the spring closes the valve again against the stop allowing boost to build. I videotaped my boost bypass valve while doing a dyno pull. The valve lever went agains the "stop" and stayed there until we shut it down.

If the valve is closed against a stop, and stays there, as mine does, how can that situation be improved?
 

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Discussion Starter · #6 ·
Good point JT about the stop, unless pressure could be escaping around the valve??? I have just seen several people say they can hold boost all the way to redline, I just dont understand what anyone would have to gain by saying there car holds boost when in actuality is doesnt, but as you and Tommy state the one I have seen with a guage that reads higher than stock sure enough showed noticeable boost loss, most notably in 3rd gear and stayed fairly steady but dropped a tad in 4th.
 

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JT said:

If the valve is closed against a stop, and stays there, as mine does, how can that situation be improved?
I think the concept (i'll fated or not) is to increase the spring constant so that when vacuum is not present (WOT) the butterfly stays completely closed even under high boost.

MJ
 

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Here is a link of the pic of the mod....
ADMIN NOTE: link to missing attachment removed



1-856-697-5254 is Pete's shop number....I think... Nitrous.com is the website.

The mod helps and works....

22 lbs of boost till 6k rpms, where I shifted. After 6k the boost would drop another 1 or 2 lbs. With my setup that is on my webpage in my 2003 Cobra area. yes..I was crazy for pushing that kinda boost maybe.....but it worked and ran incredible...I lived that route and know what it was all about....fun fun fun :shocked :D Its not bull....Pete even on numerous ocassions showed video of 21 lbs of boost...before we had better belt wrap mods and non slip blower pullies. One thing may not work by itself...but when joined all together...they make a family of form and function.
 

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And HotRodHarry, what times and MPH were ya running with all that boost may I ask?
 

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I really never had the time to get her to the track as much as I would have liked too....with my six kids and wife and my parents probs..it just didnt happen. With a lean tune and very very slippery track the run is on video it did go a 12.14 her first time out ever at a track. Its on my webpage...I granny shifted big time and road the clutch out of the hole all I could to keep some sort of traction. After I got the currect tune for my 6lb lower and 2.80 upper...she was just incredible! Pete knows his stuff when it comes to the Eaton and high boost with nitrous. Sorry I wasnt able to get a video run at the track after that...wish I had. But there are tons of things to do in life first....I will try and get my Mach 1 soon too....I love racing! You go gettem for me solidsnake...the Cobra's are awesome. My mods did work..and thats all I have to care about.....she was one awesome car!
 

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Discussion Starter · #11 ·
I'll get a price and go from there, MJ's statement makes some sense.
 

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I have a Pete modified valve w/ the extra spring, a 2.93 no slip pulley, all 3 billetflow idlers, and a Gates 74.5" belt. My boost hits 14 or maybe 14.25lbs and starts to drop around 5000/5500rpm and slowly falls to 12lbs (could be 11.75lbs) by redline. I didn't notice any difference w/ the modified valve.

Jerry
 

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redaddiction said:
Anymore info on this maybe a write up ? I guess this looks like a worthwhile mod.
Who was that addressed to? My personal opinion was that the modifed valve wasn't worth anything so therefore wasn't something worthy of a writeup. The picture in the link Harry provided has a great pic of the modified valve. The spring in the pic is what Pete added, the before pic would look the same w/ no spring at all. Read the description again of how the valve works and Mark's description of what the spring is purported to do and you'll have the whole story. Sounds like Harry and Pete's results were different than mine, don't know what to tell you there.

Two other ponits maybe not touched on already are as follows:

1. It was the thought early on that there was some adjustment possible with the valve. This is done with the two bolts that secure it to the supercharger case. The shaft rests on a stop cast on the supercharger. It is possible that you can get the boost to come on slightly sooner (measured in tenths of second probably) depending on where you had it secured.

2. Rick said he could do some tuning in the chip to allow the boost to come on sooner. Don't know anything about that since I don't have one of Rick's chips. He said it was worth a tenth or two in the quarter mile..

Jerry
 

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Discussion Starter · #15 ·
Jerry great info I as well as others appreciate it! You have every possible thing out there to eliminate boost drop and its still present, I'll keep my combo as is until someone can come up with something to make these Heatons hold boost if possible. I'll get me a good A Pillar pod with a guage this weekend @ the NMRA's in Bowling Green and see how much boost I am losing!
 

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One little trick that does also help, but gets alittle messy, is some VHT traction compound applied to the blower belt. It works...
 
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