I had a post recently about my car not boosting with the intercooler hooker up. I pressurized my intake manifold with an air compressor and the only place air leaked was out of the air filter. So now I ask, what sort of problems can prevent my car from making boost? I'm pretty sure it's mechanical because to prevent my car from making 1 psi even if I punch it in first there has to be a big hole.

I'm almost thinking that there is something wrong with my bypass valve. The intercooler tubing changed the way the bypass valve pointed if that makes any difference... I just can think of what could be wrong here.

 

I agree that your bypass valve is a likely culprit. I don't think mounting "direction" is an issue. The bypass valve is a spring and a diaphram. The spring holds the valve open during non-boost driving. The diaphram, actuated by the vacuum/boost line, overcomes the spring to close the bypass valve under boost applications.

Your previous post stated that your car makes boost without the aftercooler, therfore your bypass valve works. If you don't have a leak in the ducting, verify that the vacuum/boost line to your bypass valve is connected and not pinched.

 

Thanks for responding Obe-Wan

I just checked and it was fine, no pinches... what I don't get is how it will work with the vortech discharge tube hooked up to the blower. But when I hook the intercooler tubes back up it's 0 psi all day long. I hooked up the air compressor to the brake booster hose and held the throttle body open and the only place air came out was from the filter, nowhere else!!!! I'm almost thinking it HAS to be some issue with the bypass because a hole preventing from making boost would have the be the size of the grand canyon and I think I would notice that...

Does having a longer stretch of tubing have any effect on the bypass valve???

Keep in mind that the first time I took the car out I made boost but I blew the discharge hose off the blower (it put in on kind of quickly). And the car makes boost without the intercooler hooked up. So experts, SOLVE MY PUZZLE!!! =)

 

IT makes boost without the aftercooler, but none with the aftercooler? Did you check to make sure that someone didn't stuff a rag or something in the aftercooler and that it is free flowing? Didn't you buy this second hand, maybe somone stuffed something in there to prevent anything from getting in there during shipping. If the blower makes boost and all you do is put the aftercooler on and nothing leaks, it obviously has something to do with it. CHeck it out!

 

It is an air/air intercooler. Thanks for responding bill... I don't think anything was stuffed in there but I will ask the shipper. The thing I don't get is that it made boost on the first run (about 4-5 psi) and then it blew that discharge hose off the blower and after that it won't make boost with the IC hooked up. When I put the regular vortech tubing, voila I have boost again. I will double check if anything was stuck in the IC. Even if there was, wouldn't that help the blower build pressure???

 

Sure it would, but remember where your boost gauge is hooked up to. The intake manifold. If there is a huge restriction in the aftercooler, the blower itself will build boost before the aftercooler, but the pressure will go down due to the large Differential across the aftercooler. Something just doesn't seem right here.

 

I'd try pulling of the bypass and pluggin the hole... just to rule that out.

I think if there was a restriction in the intercooler, your car would run like crap... since it still needs to get air from somwhere to run, when not in boost.

Anyways, If you have the maf right before the TB, then just unhook the pipe from you intercooler to the MAF, start the car, feel for air coming out of intercooler. (may want to rev it a little) Of course you will want your bypass to not be open on this test.

 

Will the car be able to run without a bypass hooked up??? I'd like to rule that out. Also about plugging in the intercooler, I will peform that test too.

I somehow have a feeling that it is something mechanical like the bypass. Regardless I think it's about time to pick up the vortech race bypass.

As a side question, are there any negative effects to venting the bypass to the atmosphere? What does it sound like?

 

Yea car should run without the bypass, but IMO its harder on the blower, I wouldn't do it long term. What I usually do when checking for boost leaks is seal off the end of the pipe wherever your air filter is, then pressurzie everything. This way you can actually get it to hold pressure instead of "just leaking out thru the air filter". Of course, use a regulated air supply, and start at real low pressures. On a 3000GT i once I had, the intake had gotten twisted and caught on a mounting bracket when i installed it and basically left a 1/16" gap between it and the heads...not a good thing for boost Not sure if you tried this or not, but you may want to pressurize the intercooler itself and make sure you didn't somehow blow a hole in it...I've never seen that happen but its worth a shot at this point. Given how big this leak or whatever it is must be, you should be able to find it pretty easily.

Carson

Edit: I'm not sure how it'll sound vented open atmosphere...although similiar to a blow off valve, I imagine it'll be a little different. Some open atmosphere'd blow off valve'd imports do some weird things if you go from WOT to idle real quick (cut off) but it doesn't bother others

 

Is the bypass valve the same or different when you swap over to the Aftercooler?

 

this might be a dumb question, but are you using the stock plastic bosch? any chance you are putting it on backwards? like ya said, its not big enough in itself to leak off that much boost. but just let your car idle...the blower will be pushing plenty of air...feel around all the piping, couplings, and around the intercooler, you could possibly have cracked the core of it somehow.

 

To answer that question and sneakin deacon, the bypass stays in the same position, and yes I'm using the stock bosch bypass. Also I'm not using an aftercooler, it's an air/air intercooler.

I'm almost sure it's not an air leak... I just have one of those feelings that it's a mechanical problem. I'm going to do some investigating when I have time either tonight or tomorrow.

My car makes 0 psi, consistently. An air leak big enough to not allow any boost in the system would be audible I think. I know the intercooler is not clogged because I can go WOT and spin the tires in first with no air starvation problems.

Anyway, if anybody has any other suggestions that would be great. I will post back when I have answers/results.

 

How can it be a mechanical problem if you go back the the stock configuration with the SAME bypass valve and it makes boost? I think you've answered your question, it has to be an air leak!

 

I agree...only thing mechanical that can be wrong basically is the blower itself or the bypass valve. Since both of these work with the old setup, them being the problem doesn't make much sense. I still say do my method of pressurzing (not just blowing air thru) the intake and all tubing, if you can't find a leak then then something really weird is going on. Are you sure your boost gauge is hooked up right? I wasnt sure if you were moving it or something when you swithced setups, oh well...worth a shot anyways.

Carson

 

Try taking a pressure reading upstream of the intercooler if possible. The discharge pressure of the blower may be unchanged but there is a pressure loss through the cooler with the net result being a low boost pressure downstream. You may have to do a pulley change to get your boost numbers back up.