Testing Speco boost gauge

[equipt]

Hi Guys, I just finished installing a Speco boost gauge, I have never had one or even really seen one in action so I am not sure if it is working normally. I have made a vid of it in action on the road (filmed under controlled conditions on a closed road of course) It only starts to move once it gets to just over 2000RPM in 1st gear, but in 2nd it seems to be a bit higher at 2000RPM. then to confuse things even more when in neutral sitting in the drive way the needle doesn't move till almost 3000RPM, is this normal or is there something wrong? the only thing I can see that may be an issue is there is a chance the hose going to the gauge may have gotten a little kinked where it go's into the gauge pod.

Any feedback would be appreciated.

[YT]http://www.youtube.com/watch?v=3nXN0Oaj3WA[/YT]

 

[tweak'e]

sounds roughly right.
i can't see the numbers on the gauge to see if its reading right, but the lack of boost in low gears and neutral is typical of turbo engines.

 

[shaggy]

Hi Fella's

I have a speco boost gauge too.I will check it tomorrow to see if my one does the same

Cheers
Shane

 

[equipt]

OK cool, the 1st number is 5psi, then 10psi and 15psi is at the top (12 o'clock)

 

[bods]

Looks about right, 15psi at 3000rpm. As above it won't generally move sitting in neutral revving because there is no load on the motor. For a zd30 I'd say it looks normal. I get 15psi at about 2500rpm in mine depending on how hard the foot is down, but mine is a yd25.

It should spool a little quicker if you do the egr mod, unless you have done it already

 

[equipt]

Should have mentioned I have EGR mod, 3" Tiapan exhaust with 3" dump pipe and a snorkel if any of that makes any difference. But by the sounds of things it is normal.

 

[rabbit-chop]

it looks almost as if the needle is sticking and is reluctant to get off zero, but after that seems ok. You're right, there should be some small amount of boost virtually off idle and when revving the engine in neutral. The guage should work as well at 1 or 2 psi (for example) as well as it does at 10 or 20psi. Id check the hose if you reckon its kinked. otherwise could be a dicky guage and need to exchange it for a good one.

 

[equipt]

I will have a look at it and may have to cut a couple of inches off the end and re fit it and see how it go's.

 

[rabbit-chop]

Also, though, turbo pressure relies on throttle input as much as rpm, so its concievable that you could feather it gently up to 2000rpm and make very little boost. Try tramping it off idle, and see what the guage does then.
is it a zd30 or a yd25? mines a zd30 and i virtually cant drive it without reading some boost even at the smallest throttle input and have never seen it run vacuum.

 

[the_bluester]

You will pretty much see zero boost free revving it, then basically nothing until whatever point the boost threshold is (2000 RPM sounds a touch high, my D22 used to light up at about 1600rpm, indicating that was about the boost threshold) But the video makes the gauge look like it might be a little sticky at zero boost the way it twitches off the stop. You could really feel the boost threshold in mine, nothing nothing nothing and then a step in power as it came onto boost, but I would still expect to see the gauge come off the stop smoothly.

Seeing more boost in second than first is pretty normal. You may not have enough load on the engine in first to get to full boost. Try doing it again towing and see if you see more boost in first.

 

[equipt]

After having it on for a week now it seems to be a bit more "normal" it is still a little twitchy down low but what everyone has been saying makes sense about no load on it. It boosts earlier in 2nd and 3rd than it does in 1st. I am happy with it all for now.

 

[the_bluester]

An idea what a boost curve normally looks like, this is from dynoing my track car so a bit different to a ZD30, but you can see that the boost threshold is actually about 2000 rpm on this one but it really lights up between about 2200 and 3500 rpm. My car has a pretty small turbo on it to suit the type of event I do and a lot boost up much more quickly when they hit the threshold but you get the idea.

 

[rabbit-chop]

yeah, there isnt much below 2000. I just did a couple of roll-ons in my nav (2004 zd30 with digital auber boost guage standard except full exhaust, blocked egr and swirl mod)
free rev- negligable - a few points of a pound until 2000rpm, then maybe 2 or threepsi , maybe more.
1st gear roll on- negligable amounts untill 2000
2nd and 3rd gear- 1.5 - 2 psi from 1000 rpm, rising steadily upto about 7-8 untill just before 2000rpm. At 2000rpm, whammo, pretty much getting the bulk of it- low teens and still rising. Wasn't really giving it much doing these tests, just driving normal apart from starting at low rpm.
So my opinion is, your guage works, but is useless below 5psi. And i evidently need to get a life!

 

[big zetor]

I've got one on my d40 and its the same. twitchy that is' needs about 4-5 pound to move it then its ok.

 

[equipt]

Cool, thanks for all the feedback guys.