saeedm

The owner before me gave me a problem list and one item was: SEQUENTIAL TURBO SYSTEM DOES NOT FUNCTION PROPERLY (NO CHARGE OVER AFTER 4500 RPM). So, I raced over to Kragen this morning (first time driving it ) to buy a boost gauge -- I don't care about looks or fit at this point, I'm just looking to get some readings and diagnose my 2nd turbo trouble. 1 hour and 5 different rubber fittings later I found a snug fit between the included vacuum line and the once-capped nipple on the manifold. I routed it through the hood/windshield crack and into the passenger window where my brother held the gauge for me. Then it was off to get some readings...but traffic made it tough to get any. First thing that surprised me (at first): At idle with the car warmed up, I was getting -18psi -- VACUUM. I was expecting the needle to never drop below 0...But then it made sense once I realized that the gauge is hooked up to the part of the engine that sucks in air. 'OK, well as soon as the turbo spins up I should be getting some positive psi values....' Well, after some pretty rough driving I was lucky if I got the needle even up to 0psi...It just hung around the vacuum area the whole time. I'm sorry I can't get exact readings, my brother paid little attention to the gauge and I was having too much fun...Tomorrow I'll get some real readings.

Well, here come the questions:
How come some gauges have a vacuum reading and some don't? Will both work on this car? Is the nipple on the manifold the correct spot? I've seen people install gauges along the lines of the actual turbo system, with a T connector...what's the difference?

grimple1

iTrader: (1)

I can answer one of your questions. The nipple on the manifold should be ok. As long as it's getting pressurized. There should be a few locations you could plug into on the UIM.

saeedm

Would a gauge without a vacuum reading work from here? I assume it would simply stay at 0 when vacuum occurs.

proz07

iTrader: (6)

simple answer is YES you can use just a boost gauge... BUT most will tell you to have vac/boost for the reason of trouble shooting IE: low vac may be weak engine----no vac eratic idle could be vac leak
i would have a mix gauge but your choice.
one other thing i would recommend for you seeing you know almost nill about turbos would be the book MAXIMUM BOOST by corky bell. but that will only help with basics on turbo systems. a good source for all the rotary related problems is well here of course just try to search before asking most ?'s have been answered here already.
later
z

grimple1

iTrader: (1)

it wouldn't show anything.. just stay at 0. so you're correct again.

saeedm

I got some boost numbers:
18-20in/hg Vac at idle (depending on how warmed up the car is).
1st turbo works great, shoots up to 10psi right away on WOT (3rd and 4th gears).
Just before 4500k rpm it dips down to 8psi and then sort of trails off to ~5psi.
I can definitely tell theres no action from the 2nd turbo...driving at 70mph in 3rd gear with WOT gives little to no boost (~3-5psi).

*The only mods to the car are a downpipe and exhaust

alexdimen

iTrader: (13)

There is no way you are pulling -20 psi unless you have a clog in your air inlets/filter. Inches of mercury is probably what the guage is reading. ~17 in/hg is normal vacuum.

saeedm

^ my mistake, you're right

alexdimen

iTrader: (13)

As far as the secondary goes... I've rebuilt mine, but have not had the luxury of diagnosing boost issues, so I can;t help.

This site has some good stuff. http://www.wrex-racing.com/web/fd/info.htm

...and this diagram will probably be helpful.

jmadams74

Your problem is a very typical one. It could be anything as simple as a bad check valve or more complicated as in a bad TCA/TC solenoid(s)--there are two, CRV, Charge control actuator/Charge control solenoid. This sounds intimidating (at least it did to me) but there is plenty of material on how to trouble shoot and fix all of these items on our site. Start with the "T" section in the FAQ's. Good luck and welcome to the wacky world of our twin turbos (which are fantasic when working properly)!
--Jeff

grimple1

iTrader: (1)

here's a single turbo setup: