V6 Discussion and questions about the base carbureted or MPFI V6's and the rare SFI Turbo V6.

Vacuum Readings

Thread Tools
 
Search this Thread
 
Old 04-21-2012, 03:57 PM
  #1  
Member
Thread Starter
iTrader: (1)
 
XxXChrisGXxX's Avatar
 
Join Date: Feb 2008
Location: Connecticut
Posts: 463
Likes: 0
Received 0 Likes on 0 Posts
Car: 1987 Chevrolet Camaro
Engine: 2.8L V6 MPFI
Transmission: 700R4
Axle/Gears: 10 Bolt
Vacuum Readings

I hooked a vacuum gauge up to my Camaro, I am getting 15" of vacuum with a slight needle movement between 15-16". Where is all my vacuum going...uh..
Old 04-21-2012, 04:48 PM
  #2  
Supreme Member
 
ex-x-fire's Avatar
 
Join Date: Jan 2011
Posts: 1,727
Likes: 0
Received 1 Like on 1 Post
Re: Vacuum Readings

2.8s make less vacuum then typical sbc, looks like your reading is close to stock.
Old 04-21-2012, 05:01 PM
  #3  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Vacuum Readings

yeah thats pretty much right on, iirc my old 2.8 made 18inches of vacum when it was stock
Old 04-21-2012, 05:03 PM
  #4  
Member
Thread Starter
iTrader: (1)
 
XxXChrisGXxX's Avatar
 
Join Date: Feb 2008
Location: Connecticut
Posts: 463
Likes: 0
Received 0 Likes on 0 Posts
Car: 1987 Chevrolet Camaro
Engine: 2.8L V6 MPFI
Transmission: 700R4
Axle/Gears: 10 Bolt
Re: Vacuum Readings

I thought stock was between 17-21" vacuum? Isn't 15" too low, and a needle movement between 15-16" a bad thing?

I was curious so I performed a compression test in PSI,
1-160
2-170
3-165
4-160
5-170
6-170

This is a dry test. Didn't do a wet test (Didn't have any oil on hand)
Old 04-21-2012, 05:05 PM
  #5  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Vacuum Readings

the needle moves from the pulses in the intake thats normal, with normal wear and tear over the last 20 years 15/16" is quite an acceptable number

a much better test would be to do a compresison check and a leakdown test on all 6 cyls and see what u come up with
Old 04-21-2012, 05:11 PM
  #6  
Member
Thread Starter
iTrader: (1)
 
XxXChrisGXxX's Avatar
 
Join Date: Feb 2008
Location: Connecticut
Posts: 463
Likes: 0
Received 0 Likes on 0 Posts
Car: 1987 Chevrolet Camaro
Engine: 2.8L V6 MPFI
Transmission: 700R4
Axle/Gears: 10 Bolt
Re: Vacuum Readings

Originally Posted by project89
the needle moves from the pulses in the intake thats normal, with normal wear and tear over the last 20 years 15/16" is quite an acceptable number

a much better test would be to do a compresison check and a leakdown test on all 6 cyls and see what u come up with
Really? Car only has 80K on it. Huh...I believe I am getting poor gas mileage around 11-12 or so in city. I put 5.19 gallons in, and with the fuel needle were it was previously (before 5.19 gallons added) on flat ground engine running, I drove about 65 miles. Which is low, compared to the stock mileage at around 17 according to others.
Old 04-21-2012, 05:18 PM
  #7  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Vacuum Readings

recent tune up?
is the cat on the car starting to get cloged?
have u ran seafoam threw the engine ever?

seafoam is about 9 bucks a can and u get 2 uses out of it, i personally love seafoam as ive torn down an engine after using the seafoam and seeing how well it cleaned everything up inside

so if u have recently done a tuneup and all that and everything is in good shape i would do a half can of seafoam in the engine and the other half in the gastank to clean out the fuel lines and injectors and i bet ur milage will go up a good bit
Old 04-21-2012, 05:24 PM
  #8  
Member
Thread Starter
iTrader: (1)
 
XxXChrisGXxX's Avatar
 
Join Date: Feb 2008
Location: Connecticut
Posts: 463
Likes: 0
Received 0 Likes on 0 Posts
Car: 1987 Chevrolet Camaro
Engine: 2.8L V6 MPFI
Transmission: 700R4
Axle/Gears: 10 Bolt
Re: Vacuum Readings

Originally Posted by project89
recent tune up?
is the cat on the car starting to get cloged?
have u ran seafoam threw the engine ever?

seafoam is about 9 bucks a can and u get 2 uses out of it, i personally love seafoam as ive torn down an engine after using the seafoam and seeing how well it cleaned everything up inside

so if u have recently done a tuneup and all that and everything is in good shape i would do a half can of seafoam in the engine and the other half in the gastank to clean out the fuel lines and injectors and i bet ur milage will go up a good bit
More then a tune-up...New timing chain, new cap, rotor, distributor, new spark plug wires, new plugs, new carbon filter, new MAF, new air filters, new oil/filter, new EGR, new ignition coil.

I just ran seafoam through it last week, both gas tank and brake booster hose.

I don't think the cat is clogged, it was recently changed within 3 years or so. I would have to check (Real PITA without an oxy torch).

One thing I do notice is an occasional code 32 but I believe it is being caused by gasket material getting into the vacuum lines from my stupid old EGR. I did run compressed air in the vacuum lines, hoping that will fix it.
Old 04-21-2012, 05:33 PM
  #9  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Vacuum Readings

try changing ur driving habbits, most ppl forget that driving habbits have the biggest impact on fuel milage
Old 04-21-2012, 05:34 PM
  #10  
Supreme Member
 
ex-x-fire's Avatar
 
Join Date: Jan 2011
Posts: 1,727
Likes: 0
Received 1 Like on 1 Post
Re: Vacuum Readings

Make sure you have a good 195* t stat, a cooler running efi engine will use more fuel then a hot running one.
Old 04-26-2012, 07:54 PM
  #11  
Member
iTrader: (1)
 
Cadaver Puncher's Avatar
 
Join Date: Dec 2011
Location: under the hood of my car in Massachusetts
Posts: 179
Likes: 0
Received 0 Likes on 0 Posts
Car: 92 rs daily driver work in progress
Engine: 3.1 , 204/214 cam
Transmission: 700 r-4, b& m megashifter
Axle/Gears: I want a posi with rear discs
Re: Vacuum Readings

I have a 160° thermo in mine and it still gets way over 220 almost pegged. While running dual fans, new water pump, new radiator and timing set at 10°.
I wanna get a fuel pressure gauge, and vacuum gauge. I already have an air/fuel ratio gauge and it where it's supposed to be.
I can Only imagine how hot it would get with a 190° thermo.

And yes there is antifreeze in the radiator and half way up in the resevior.
Old 04-26-2012, 08:04 PM
  #12  
Supreme Member

iTrader: (2)
 
fasteddi's Avatar
 
Join Date: Mar 2011
Location: Northwest Ohio
Posts: 6,274
Likes: 0
Received 25 Likes on 19 Posts
Car: 1991 Camaro RS
Engine: BBC 509 Merlin ii 9.6:1 pump gas
Transmission: ATI pro th350 sfi case. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: Vacuum Readings

Originally Posted by Cadaver Puncher
I have a 160° thermo in mine and it still gets way over 220 almost pegged. While running dual fans, new water pump, new radiator and timing set at 10°.
I wanna get a fuel pressure gauge, and vacuum gauge. I already have an air/fuel ratio gauge and it where it's supposed to be.
I can Only imagine how hot it would get with a 190° thermo.

And yes there is antifreeze in the radiator and half way up in the resevior.
I guess this is off topic but how is your car putting out 220+f coolent temps with a 160* t-stat and dual fans? Do the fans come on??
My car for example has a 180* t-stat and if I leave the single fan on it will never see 190 degrees even on a 85 degree day and beating on it in town or outta town.

Im thinking your fans are coming on at the stock tempeture?? IIRC 225 or so was in the stock bin file?? You might wana change that or piggy back the relay on the fire wall so that you can override the relay and turn it on when you want to, if you want it to run cooler.

Last edited by fasteddi; 04-26-2012 at 08:08 PM.
Old 04-27-2012, 10:18 AM
  #13  
Supreme Member

iTrader: (16)
 
Street Lethal's Avatar
 
Join Date: Jul 2003
Location: NYC / NJ
Posts: 10,464
Received 174 Likes on 152 Posts
Re: Vacuum Readings

Originally Posted by XxXChrisGXxX
I hooked a vacuum gauge up to my Camaro, I am getting 15" of vacuum with a slight needle movement between 15-16". Where is all my vacuum going...uh..
Followed by...

Originally Posted by XxXChrisGXxX
I thought stock was between 17-21" vacuum? Isn't 15" too low, and a needle movement between 15-16" a bad thing?
Followed by...

Originally Posted by XxXChrisGXxX
I believe I am getting poor gas mileage...
If your vacuum gauge is reading too low, and your engine compression is good in all cylinders, either your idle RPM is set too high, you have a vacuum leak after where the vacuum gauge is connected, or your air/fuel mixture is bad (needle movement). Being that your saying that your getting bad fuel mileage, it very well might be the latter. Check your fast idle screw and IAC and make sure they are set to where they need to be, check for small vacuum leaks after the vacuum gauge port, and check your BLM's...
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Hotrodboba400
Firebirds for Sale
3
12-10-2019 07:07 PM
83 Crossfire TA
Suspension and Chassis
36
01-03-2016 01:26 PM
86CamaroDan
Engine/Drivetrain/Suspension Parts for Sale
2
09-29-2015 10:08 PM
IROCtometal
TPI
3
09-09-2015 10:01 AM
Vassago
Convertibles
15
09-04-2015 09:37 PM



Quick Reply: Vacuum Readings



All times are GMT -5. The time now is 12:01 PM.