Another mcxpress? *Updated please look*

[zross1]

So I've only been able to build about 14-15 psi with my mcxpress kit on a Apex. I started with the basics and checked for boost leaks, found a few and fixed them. I then went to the exhaust. One of the bellows was blown out, and both rear exhaust doughnuts were toast. Fixed all of that and replaced all bellow doughnuts and rear header doughnuts. Checked my wastegate and tightened it about 3/4 a inch (really tight) and the made sure the wastegate was mated and sealed properly to the turbine housing. Used two different boost controllers. Pulled the line off the westgate so it would stay shut, no dice... Basically I've checked and fixed everything I can think of that would case the turbo not to build boost.

Now, what is wierd is at about 8,000ft I can build 17-18 psi. BUT when I get to 9500 ft or above I only can make 14 psi??? The only thing I thought was maybe the 16t turbo is only capable to make 14 psi at high elevation. The compressor map has a 3 pressure ratio which theoretically should support 20 psi at 10,000 ft. Has anyone else had this problem that rides high elevation? PLEASE ANY ADVICE OR IDEAS? Will a 19t solve the problem?

 

[snowy1]

I have made over 20 lbs with a 16t at 10,000 ft no problem, you have a problem some where, do a pressure test check with soapy water, check turbo see if there is any play in the shaft make sure its spinning free, make sure compressor wheel is not rubbing on housing.

 

[zross1]

Thanks. I thought I should be able to get that kind of boost. I've done a boost leak test and eleminated the boost leaks. I have my wastegate pretty tight at least tigher then I ever had my gt2871. But maybe it is comming open. I'm going to try to wire it shut and see if that is the problem.

I've checked my turbo numerous times, no shaft play, both compressor and turbine wheels look great and neither are rubbing. I'm going to replace the headers and see what happens.

 

[PwdrNut]

Has this been an issue since the build?
If so, have you checked the timing. If the cam is a tooth off, it will still run although the idle will normally be off. It could be possible this is your problem if it has been an issue from the beginning and not recently happened.

 

[rxrider]

Have a AFR? What's your AFRs at higher altitude? Going too fat could bring power and pressure down, maybe.

 

[zross1]

Has this been an issue since the build?
If so, have you checked the timing. If the cam is a tooth off, it will still run although the idle will normally be off. It could be possible this is your problem if it has been an issue from the beginning and not recently happened.

Good thought. I bought it used but know from the guy I bought it from this hasn't always been a issue. It idles great, so I don't think it's a timing tooth. I should mention compression is 120 psi dead on for all 4 cylinders at 4700 ft elevation. So I think the motor is ok.

 

[zross1]

Have a AFR? What's your AFRs at higher altitude? Going too fat could bring power and pressure down, maybe.

Stock regulator. I thought about that and on the hill I've added and pulled fuel, but nothing changes. I'm seeing high 12's on my a/f.

 

[zross1]

I think I may have found it. I replaced these exhaust doughnuts on the headers 2 rides ago Did I put them on backward? They are burnt out again already after 2 rides...At least it looks like they are to me? Could this be causing me to only build 14 psi?

 

[rxrider]

Yes you did, they're backwards, no doubt about that. They may not seal up very well like that.

 

[zross1]

Thanks, hopefully that was it!

 

[zross1]

That was it! Thanks for the help.

 

[rxrider]

Glad it was an easy fix

 

[zross1]

Ya, me to. What sucks is I didn't put them on right the first time.