Boost Gauge w/Procharger?
 

Has anyone used a Gaffrig boost gauge on a Procharger application with the gauge plumbed into the manifold?

I just installed a gaffrig 0-15 PSI boost gauge and it occurred to me that since I plumbed it to the manifold (instead of the carb box) that the gauge would likely be seeing vacuum during idle.

Does anyone know if the gauge can take the engine vacuum? I have not run it yet but I didn't want to ruin the gauge.

thanks, Paul

I do not know about your gauge. I would call manufacture. I have Vac-boost gauge plumbed to the intake. With this I can see exactly what motor is doing. Plumbing to the box will not give you reading what motor is doing. I have gauge in box & in intake. When crusing intake will show 6-5" vac but box will show 3 lbs boost.

The correct place to check boost is in the intake manifold. You have it in the right place. If you had it in the box before the carb it would not be accurate.

Thanks guys,

Yeah I really want to watch the manifold pressure. I just checked the Gaffrig website and they have a combo gauge. The only drawback is that it is 0-30" vac/0-30 psi Boost. On a 2" face, that will translate to pretty hard to read and not so much resolution.

Have not run it yet (just got the motor back together w/procharger kit) but I'm guessing that I'll be looking at less than 5 PSI max pressure in the manifold so I'll be in the bottom range of the gauge.

The Procharger Stage II kit is belted to run @ 5 PSI. I'm sure that meand 5 PSI in the box!

I'll call Gaffrig this AM.

Paul

Just got off the phone with Gaffrig and they said that the vacuum will not hurt the 0-15PSI boost gage.

So I'm off to splash it on Wednesday!:D

My guess is 5 lbs in manifold, 6-7 in box

turbojack,

Hope you are right. I have no experience with the Procharger yet but I was expecting the 5 PSI to be the max pressure in the carb box. I'm going to prop the boat for ~5200 rpm. I don't have any idea what the boost profile is like for my set up, but I think they rate the M1-SC at 5 #'s at 4800 engine RPM's. I'll let you know.

More is better!

thanks for the info!

Paul

This is my first year with procharger but good buddy of mine is on his 4th year. I am suprised his motors are still togeter since he runs wide open all the time.

Most important thing if you are setting up is get jetting right, This means on rich side. Check plugs at a number of different rpms to make sure you have jetting right at part & full throttle. If wrong motor will detonate itself apart & you will be doing motor work real soon.

Paul,
Not sure if anyone has mentioned this yet, but you might want to consider running the boost gauge to the box, and not into the intake manifold. The reason I say this, is because the boost reading from the intake will have an air / fuel mixture. If the line pops off the gauge while running under boost, there is a potential for air / fuel mixture to escape into the helm area. Also, in the carb box, there won't be a (significant) vacuum to worry about. But like Turbojack said, expect 1 - 2 psi drop across the carb.

As for gauges, I would not hesistate to look at (dare I say it...) Automotive style gauges. I went with a set ot Autometer "Classic Rod" boost gauges. Haven't had any problems with them. Also, the vacuum goes to 30 in/Hg while the Boost only goes up to 15 psi. Plus, the gauges don't look like your typical Autometer gauges. They actually fit the Gaffrig Speedo and Tach better than the other Gaffigs. I've been thinking about swapping out the oil, water, and voltage gauges with matching Autometers for better looks and accuracy.

-Bayley

Wooaah Bayley,

Nice instruments! Quite the contrast to my 1990 Baja. Those look great. I wouldn't expect you to have isues with the automotive gages anyway. When you think about it, you can have plenty of humidity locked up in a car and besides, who puts as many hours on their boat as their car?

On the gauge plumbing/fitting, you have a good point with the air/fuel mixture. I ditched the 1/8th line that came with the gauge and used 1/4 Polypropylene with high quality stainless fittings (Swagelok) with tubing barb inserts to support the tubing where the compression ferrule locks onto the tubing. It's pretty secure.

What are you guys running for Timing? I just installed an MSD system with the pro-billet distributor. I have the black bushing in it with one heavy and one light spring. The advance curve looked pretty linear right on up to 5000 RPM. Do you have to check the timing @WOT? Or can you just set timing @ idle and count on the bushing stop to limit timing? I was told to run 30 deg total advance. I saw some posts that indicated 28-29 deg. total timing.

I also bought and had the carb. set up by Dean Nickerson and he said that the jetting should be OK. We'll see.

Man, I am hoping I don't have to keep pulling plugs to look at them bacause it is a royal pain in the a..... to get at the starboard side ones. I'm geting ready to put the back seat in and I can't imagine getting at those plugs once it is back together!

What motor is that 7.4L or mag?

I also used a gauge in the box and the manifold.

I referenced the fuel pressure regulator of the box. That is a necessity.

The boost gauge in the box I could cross reference with the fuel pressure guage. (Boost + 8)

The gauge in the manifold was what mattered for real boost in the engine. So, I wanted to know that also.

I used an 800 Holley also set up by Nickerson.

Timing is a delicate issue. It depends on your set up, ie; plugs, T-stat, heads-and work done to them, cam, etc.

If your motor is basically stock, stay with the timing marks you've mentioned.

DAVE

I thought timing should be at full advance by 3000 rpm. Not still advancing all the way to 5000...

mcollinstn,
You are correct on the timing. I looked at the profile last night on the MSD info. The mechanical advance is fully out at about 27-2800 rpm.

Fasterdamitt (like that screen name)
The motor is a 454 MAG w/competition valve job, custom roller cam & rockers, ARP stud kit, Stainless Marine manifolds and risers, MSD ignition, and corsa quick & quiet plus (6.5" silencer tips). It was bone stock with S/M manifolds prior to Procharger and ran 64 mph.

Dave F,
I am running boost referenced fuel pressure (aeromotive set up) as well. It sounds like a 2nd gauge watching the box pressure is a good idea. I'm tapped out for room on the dash for gauges (older boat) but I think I'll drill & tap a hole inthe box cover and screw a gauge into it so I can at least have someone watch the pressures on a trial run. The t-stat is the 140 deg. one that comes with the Procharger kit and I drilled the (3) holes in it based in the instructions.

I set the timing last night to 10 deg BTDC at idle. With the MDS distributor using the black bushing (18 deg max), I should be at 28 deg total advance. Nickerson said to run 30 deg but I figured I'd start a bit on the conservative side. comments?

Thanks for all the input guys. I'm throwing this thing in the water on Thursday for the first time in 2 years! It has been a loonnggg spring! Hope all goes well!

Paul

Paul,

I've sat in Dean's shop and talked to him for well over an hour on several occasions. I've had my carb up there for a "freshen up" so I get to talk to him when I drop it off and pick it up. Got the shop tour and checked out all his toys. Good guy.

We had lengthy discussions on timing and fuel delivery.

He's not a big fan of increased advance. He, (in my opinion) is the leading Pro Charger carb. set up guy, in the country.
Most of the dyno testing he does is with roots style blowers and he talked about the motor going into detonation fits after/during a run. Thats why he likes to keep the timing cut back.
On the other side of the coin, I think that there are benefits to the centrifugal/inetercooled compressors and the cold charge they allow to also guard against detonation.
I have on many occations felt the discharge pipe to the compressor before the cooler and it being very warm. After the cooler was actually cold, and I mean almost refrigerator cold.
Now, obviously that depends on raw water temp, but you get my point.

I've discussed with him the different variables of spark plug, cam and T-stat settings to stay out of detonation.

Like I said, with your motor being basically stock, using T-stat and stock plugs, keep it between 28-32*

A local guage isn't gonna help you much. You really need to see it.
If your guage panal screws into the dash, you could rig it some how.
Example: you could fab and bend some aluminum sheet, screw it into the dash using existing screw holes and mount the guage in the aluminum. Hey, just a thought. Just trying to give ya some ideas, ya know?
As far as drilling into the box, there should already be two holes in the back of the box. One for the regulator and one for your guage.

Keep me posted
DAVE

Nevrenuff,
Your pkg sound close to mine. Was a 454mag.Now I have a 224-236 @50 .540 lift roller. Rec port heads, rockers ect. Pro Charger 7lbs at 5100 rpm. Carb done up by the Carb Shop in Ontario Ca. Timing was at 34 when installed by American Offshore in 97. Now running 30 deg but think it can handle more since the pistons looked good at 34 on a Pro charged 454 mag.