Advice please (Boost probs)
10 October 2002, 11:12 PM
#1
Scooby Regular
Thread Starter
Join Date: Feb 2002
Posts: 369
Likes: 0
Received 0 Likes
on
0 Posts
What boost?...fitted a defi boost gauge today and carn`t get my head round the result it shows and it makes me wonder wether I have fitted the take off from the manifold in the right place!
On tick over (600 rpm) it reads 550 of vacuum. What I would expect.
If I rev to 3000 or exceed that I get no boost showing. I thought I had wired the gauge wrongly or had tapped off the manifold in the wrong place. Then on making a journey I noticed the gauge showing (at max throttle) 0.9 kgf I think this equates to 13.05 psi (ill stand to be corrected)this proves the turbo is working but it does not seem to be dependant on engine revolutions as I would have expected? Am I just stupid or just missing the point? Advice from you learned gentlemen please.
On tick over (600 rpm) it reads 550 of vacuum. What I would expect.
If I rev to 3000 or exceed that I get no boost showing. I thought I had wired the gauge wrongly or had tapped off the manifold in the wrong place. Then on making a journey I noticed the gauge showing (at max throttle) 0.9 kgf I think this equates to 13.05 psi (ill stand to be corrected)this proves the turbo is working but it does not seem to be dependant on engine revolutions as I would have expected? Am I just stupid or just missing the point? Advice from you learned gentlemen please.
11 October 2002, 01:32 AM
#2
In psi here is what you might approximately expect to see in a standard car. (14.5 psi = 1bar)
T.O. 7psi. Over run 10psi dropping to 8psi vacum. Tick over 7psi.
Level road light throttle cruise vacum 1 to 4 psi vacum. Light accn boost up to 4psi say or high speed cruise. Hard accn and WOT up to 14psi boost. Only very approx as I do not have a standard car but this should give you an idea.
T.O. 7psi. Over run 10psi dropping to 8psi vacum. Tick over 7psi.
Level road light throttle cruise vacum 1 to 4 psi vacum. Light accn boost up to 4psi say or high speed cruise. Hard accn and WOT up to 14psi boost. Only very approx as I do not have a standard car but this should give you an idea.
11 October 2002, 04:27 AM
#3
Scooby Regular
Join Date: Aug 2002
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Turbos utilise engine LOAD to make boost not RPM. Yet most times RPM is the best indicator of engine load - expect at when revving the engine while the car is stationary, etc. This is because turbos are driven by air (exhaust) expansion due to heat - which is produced by engine load.
Hope this helps.
Hope this helps.
11 October 2002, 08:54 AM
#4
Guest
Posts: n/a
Hmmmm, the 2 posts above confused me even more.
A.F.A.I.K, you will get a vacuum at ticker. Revving the engine while not moving will not produce +ve boost figures (correct me here if I'm wrong), you need load i.e. you are driving to see this.
Assuming standard car, in 4th gear you should see the boost gauge dial up approx 14 PSI momentarily (peak boost) at about 3K revs ... then drop approx 1 PSI (boost held) until about 5.5-6K where it will tail off again.
Light throttle will see the gauge mostly in vacuum. A bit more right foot and you'll see anything from vacuum to the 13-14 PSI mark.
Any help?
Doofus.
A.F.A.I.K, you will get a vacuum at ticker. Revving the engine while not moving will not produce +ve boost figures (correct me here if I'm wrong), you need load i.e. you are driving to see this.
Assuming standard car, in 4th gear you should see the boost gauge dial up approx 14 PSI momentarily (peak boost) at about 3K revs ... then drop approx 1 PSI (boost held) until about 5.5-6K where it will tail off again.
Light throttle will see the gauge mostly in vacuum. A bit more right foot and you'll see anything from vacuum to the 13-14 PSI mark.
Any help?
Doofus.
11 October 2002, 04:10 PM
#5
Scooby Regular
Thread Starter
Join Date: Feb 2002
Posts: 369
Likes: 0
Received 0 Likes
on
0 Posts
Doofus, thanks........you hit it on the head, exacly what I am reading and your comments explains it all. So boost is not dependant on revs more on engine load! Thanks for your comments!
Bob
Bob
Thread
Thread Starter
Forum
Replies
Last Post
Sam Witwicky
Engine Management and ECU Remapping
17
13 November 2015 10:49 AM
hedgecutter
General Technical
3
25 September 2015 02:35 PM