boost creep

[doelcow]

Currently I'm running mystery cams (allegedly 275 duration... not sure of the brand... came in the car)manley springs, afpr, 720cc injectors,2g head, big intercooler, e3 turbo manifold, big e3 turbo, 3" turbo back exhaust, and a blitz ebc.

If I use more than 50% throttle I go from 10 psi fairly rapidly up to 20+ psi. I took off the waste gate actuator and verified it was working properly. I bent the arm on it to get an extra 1/8 inch of travel without taking tension off of the flapper arm at rest. I disconnected the ebc and hooked the wg directly to boost and still 20+ psi! Is there something I'm missing? Am I going to have to use an external? How suck are the ebay ones

click

...(asking people about personal experience... not friends of friends)? Can it be swapped on with the turbo in the car?

 

[grocery_getter]

You can't run 10psi on an evo3 16G with the stock internal wg. When you hooked up the vacumm line straight to the wg its running 20psi because that is the lowest it will run with your 3" free flowing exhaust. You can make the wg bigger by running an external 38mm w/g off the manifold or off an o2 housing with a 10psi internal wg spring. Or make the exhaust more restrictive. With the regularly run 3" turbo back no cat exhaust the stock-as-it-comes-from-mitsu evo3 16G IS an 19-20psi turbo.

 

[alansupra94]

What about for a small 16G? I have a full 3 inch exhaust as well /ubbthreads/images/graemlins/grin.gif

 

[doelcow]

I get that but... she doesn't seem to want to stop at 20 and starts to bog and act funny...

it could be my tune but watching a/f and timing it looks about right...

(using ecmlink, an innovate LC1, a wally 255, with a peak of 81% injector duty)

 

[Adorsey]

Im running into the same problem.(not that its really a problem running 20~psi)
But he does have it right, I cannot run stock boost pressure whatsoever with my E3B16g. Even without a mbc.

*If your tune is ok. then I wouldnt change it because of the situation. Try a Forced Performance 17lb acctuator, or set you mbc to 10~11psi and try to dial it in.
I have to get seals for my boost controller, but my plan was to try and dial my mbc in at around 10 psi and with stock boost @10-11psi,I should be able to have no boostcreep and full boost(20+psi)around 3500rpms. With stock acctuator and 3" o2 housing, 3"tb.

That is what I hope!

 

[Diego]

I find this odd...

But for comparison purposes..

577 runs a 20g with 15psi stock exhaust no creep
On the S16g he pulls 15~18psi

My E316G on 1309 with no cat and 3" CMP exhaust I hit 15psi and hold... /ubbthreads/images/graemlins/dunno.gif


Maybe you have a massive leak on your mani, dp or somewhere exhaust wise,
Does it go faster when the boost spikes or is it a gradual go?
Cause if you see the boost spike and you don't move, that's a major leak you need to find.

 

[thecman02]

You have to do mega porting to the turbine housing waste-gate area. Once that is enlarged enough exhaust gas can bypass the turbine.

 

[Adorsey]

check my edit. sound okay?

 

[doelcow]

side note... what's everyone seeing in terms of airflow at 20 psi... I just looked at my logs and when I hit 20 psi I'm seeing 3+ gm/rev which seems unrealistic....

 

[boostedinaz]

Quoting thecman02:
You have to do mega porting to the turbine housing waste-gate area. Once that is enlarged enough exhaust gas can bypass the turbine.



Supprised it took this long for someone to post this. With enough and correct porting you can run a 14b or 16g with a very large exhaust. Just going to an external gate may not fix the issue and the issue is in the turbine housing not the size of the gate itself.

 

[belize1334]

I've tried different combinations of exhaust systems, o2 housings, exhaust housings, etc. With both my 14b and my s16g I get creep. The only sure solution is to enlarge the wg passage. The 34mm flapper mod will work if you bore out the hole to match. If you have an E3 housing the flange isn't as big and can't be bored out to appropriate diameter for the 34mm. The very best is to run an external wg either off of the manifold or as part of the o2 housing. In the latter case the wg passage should be bored out to 40mm or so.

 

[pmp285]

im also running a e3 16g, holding at .7 bar of boost... my WG actually is threaded so you can adjust it... tried adjusting it to 1bar... works great.. i believe you can also get boost creeps with small cracks in your exhaust mani... happened to a friend

 

[doelcow]

So here's my theory... I checked my base timing (I know I'm a jerk ... I should have checked it wayyyy long ago) and it was retarded 10 degrees and my initial tune was way on the safe side... (read rich). Basically, I was almost set up like an anti-lag system (tons of unburnt fuel igniting through my turbo). Just to be on the safe side I checked my plug gaps and 3 of them were gapped to .024 and one was gapped to .026. With all of that corrected and my EBC set to 48% I now hold exactly 20 lbs without a problem.

Out of curiosity... those of you who tune with a wideband, what afr are you running on a wot 3rd gear pull and with what timing?

 

AFR depends on a lot of different things.

What type of fuel? Compression? Turbo? Boost? Intercooler? How far are you willing to push your setup?

My current setup on 91 octane I run 10.8-10.5 afr. That's with a 68HTA at 27 psi moving 42 lb/min of air. Timing is 6 degrees at peak torque climbing to 12 degrees at redline.

Once I get the meth injection dialed in I'm hoping to to run 32 psi, 11.0 afr, and 2-5 degrees more timing throughout.

When I ran e85 and a small 16g a few years ago I ran 25 psi, 11.5 afr, and saw 20 degrees peak timing at redline.