How much boost should I have? Only 7psi?

[Shytheed Dumas]

I just finished my KS rewire thanks to Shaeff's rewire kit and expected to see my boost come up beyond about 7psi max but didn't see much of any improvement. Here are my mods:

1. Apexi intake
2. Custom 3" elbow
3. Custom 3" downpipe
4. Magnaflow 3" Hi Flow Cat
5. 2.5" Flowmaster Delta 50 Muffler (to knock the noise down for the wife. :icon_conf )
6. Bosch 110 BPV

Given these mods, shouldn't I have pegged the stock boost gauge? I was really expecting to see 9 to 11 psi. Sound like something's wrong to you guys? If so, where should I start looking?

Oh yeah, check engine light is off so I believe I should be code free.

 

[Joel W.]

It's always good to check your codes even if the check engine light is not on.. Some codes will not trip the check engine light.. Check your timing while your jumpered also..

Why did you go with a 2.5" muffler when everything else is 3"?? That could be the reason for the boost level staying steady and not increasing...

It might be worth testing without the muffler installed to see if that helps.

 

[92turbo4life]

are you auto?
does it spike into 2cnd if you are. like 7 to 10 then a steady 7?
if not id say check for a booost leak...lol hmmm

 

[MDCmotorsports]

Kurt: I think it has something to do with the crush bent 2" exhaust you recently installed. (or so I heard)

:-(

 

[Shytheed Dumas]

Joel - I will check codes tonight and see what shows up. As for the muffler, I allowed myself to be talked into a 2.5" muffler by the dingdong who sold it to me. He was convinced he couldn't hang it under the car right with 3" pipes. Since then I've come to my senses and I'm a little irritated with myself for listening to him - of course there are 3" muffler that are hung up under the car in the right place, but I wasn't thinking at the time. :nono: Next year I'll make it right - just as soon as my 5 speed swap is done.

92Turbo - I am auto - for now. I haven't seen any spikes - just a steady 7 psi. I'm thinking of building a boost leak tester, but I thought a leak would throw a CEL. Based on what Joel said, I will run codes and see if anything comes up.

 

[Shytheed Dumas]

Kurt: I think it has something to do with the crush bent 2" exhaust you recently installed. (or so I heard)

:-(

I really regret jumping to a quick fix on the decible thing. Normally I take my time to make sure I do things right, but I didn't this time. Shame on me, but I will make it right. BTW, it's 2.5" for whatever little help that does.

Forgive me Jon! :cry:

 

[lagged]

but I thought a leak would throw a CEL.

no it wont. boost leaks can cause a premature fuel cut however. but that is sometimes, not always. so you can have a boost leak with no other indications.

 

[Joel W.]

BTW, it's 2.5" for whatever little help that does.

If it is 2.5" crush bent pipe, then it is actually about 2.25" after it's bent.. I had to swap to mandrel bends to get past 10psi on my car.

no it wont. boost leaks can cause a premature fuel cut however.

I agree if it is a big enough boost leak and fuel cut is tripped, it should set a code 34, no?

 

[lagged]

whatever the fuel cut code is. i dont remember off the top of my head.

 

[NickSupra]

shim the wastegate a bit.

 

[92turbo4life]

i heard that just makes u run lean^?

 

[NickSupra]

If it causes you to run lean, then you have other issues. It simply puts more tension on the wastegate and allows it to hold boost a bit higher.

 

[92turbo4life]

lol i figured wat i heard was wrong..
kid was talkin bout to much air going in and leaning this out.., im like wtf

 

[Joel W.]

A higher boost level means greater air to fuel ratios.. That can cause it to lean out and cause detonation at some point. Mine runs lean over 14 psi but fuel cut should protect you to a point..

 

[thevork]

Can anyone please explain to me why the boost levels should go up by just replacing/upgrading the intake and exhaust?
How does it affect the wastegate actuator (and thus: boost) ?

afaik nothing happens to it? To up the boost you should either shim the wastegate or install a boostcontroller (manual or electronic).

 

[billspreston01]

because it takes away pressure on the compressor and turbine thus letting it spool quicker and spin faster creating more boost (somebody correct me if I'm wrong)

 

[NickSupra]

Basically. It just is less of a restriction and allows the air to move more easily. A slight increase can be seen with intake nad exhaust, however, usually the biggest gain on the stock system is an upgraded ic and pipes.

 

[Shytheed Dumas]

Just ran codes, and got the all's clear. That is, if a continually repeating quick blink means I'm code free, which is what I understood from the SOGI website.

I just don't get it. Must be restriction due to the 3" to 2.5" muffler, but in all honesty, I remember a very similar boost level prior to putting the flowmaster on, even though I only had the wide open exhaust for a day and a half... Really Jon, I'm really really sorry, forgive me please!!! :cry:

I will go ahead and put together a boost leak tester this weekend and see what happens.

 

[jdub]

A slight increase can be seen with intake and exhaust,

:withstupi The operative word here is "slight"...and Nick, you're not stupid

On a stock CT26 (not shimmed or no MBC), the most boost I ever saw was ~6 psi...the intake, Defcon downpipe, and 3" CAT back exhaust on my former set-up did increase it "slightly", but it still did not peg the stock boost meter. It did help with spooling the turbo up faster due to less restriction. BTW...you are negating a lot of your downpipe mod by using 2.5" exhaust tubing

Boost on a stock CT26 is controlled by the wastegate actuator, so unless you shim it or install a boost controller, boost is going to be in the 6-8 psi range. You may have a very small boost leak, but what you're describing sounds pretty normal to me.

 

[Shytheed Dumas]

Thank you Mr. Dub, and to you NickSupra. I'll have to consider shimming the wastegate, but I'm going to research it a bit first and make sure I'm not really doing something stupid. Like restricting things with 2.5" tubing in a moment of stupidity that I now have to fix and don't have the money for, and so will need to live with for the next year and suffer through months of embarrassment over. :cry: