fuel cut on stock engine with DDP?

[Rennat]

so i just installed a BIC DDP thats vented, made a custom 3'' cat-back. finally went about 3/4 throttle, and i hit fuel cut hellla hard out of no where... but im only hitting 9 psi... not 12... or 14... just 9.
i'll try another boost gauge from my friend, but, its read fine all this time.

my fuel cut in 3rd gear is at 4000rpm~
but why?

engine specs:
.40 probe's
eagle rods
titan MHG
stock rebuild turbo @ 9psi
stock IC pipes and IC
bosch 110 bov
new vacuum lines everywhere

would my motor being .40 over lower the threshold for fuelcut???
i really dont see why its hitting fuel cut... on my stock exhaust i was running 8psi to redline no problem... i really dont want to go lex afm and 550 on a stock turbo!!!!

 

[Poodles]

Boost leak...

Also, make sure the wastegate can open all the way, I don't get fuelcut on mine because it can open fine...

 

[speedfreak426]

I have a big mouth downpipe, 3" exhaust, stock internals, 2.5" intercooler pipes and not much else.....

I hit fuel cut at 9.5psi, normally around 4000rpm, especially in 3rd and 4th gear (but my 7m is in a 1977 celica if that matters)

No boost leaks.

 

[Rennat]

Boost leak...

Also, make sure the wastegate can open all the way, I don't get fuelcut on mine because it can open fine...

so you think i may creep really fast and it causes me to hit cut then?

 

[Poodles]

if you have a boost leak (even a minor one as it will get worse with more pressure), the AFM is still seeing hte same amount of air...

I get stock PSI on my setup, no boost creep, but i think my wastegate is a bit tired...

 

[Zumtizzle]

Boost leak...

Think smart. It can leak in some nice fun places, Tanner.

 

[GrimJack]

Boost leak is the number one cause of premature fuel cut. Build the tester and do the test.

 

[rtrdpenguin]

I have a big mouth downpipe, 3" exhaust, stock internals, 2.5" intercooler pipes and not much else.....

I hit fuel cut at 9.5psi, normally around 4000rpm, especially in 3rd and 4th gear (but my 7m is in a 1977 celica if that matters)

No boost leaks.

I have similar mods (3" turbo back exhaust, cone filter intake, 2.5" hardpipes and aftermarket IC, .020 over pistons) and hit fuel cut at 10 psi also with an HKS EBC.

I can run to redline at WOT in 1st and 2nd at 10 psi w/o cut but 3rd always gives me problems wen the rpms get above around 5k. 4th seems fine but I haven't gone up that high in 4th :icon_bigg

 

[Racer-X]

I head a boost leak after installing my 3" turbo elbow. I was just checking a couple of things directly after install (accordeon hose etc.). In the end the a-hose wasn´t tightened the way it should have been and when pulling hard it just felt like the typical fuel cut.

I fixed the hose clamp and solved the problem.

So, I would say you must have a leak somewhere.

 

[Rennat]

i see... i didnt think about how a small boost leak would become much worse with the DDP...

i'll go throw the tester on...


but on a positive note, on the way to work i raped a 5.0 mustang... was like a 99ish... he didnt want any after that though. hahaha

 

[s383mmber1]

Hows that downpipe sound? Must make hell when that wastegate opens, huh? :evil2:

My money is on a boost leak....is your wastegate shimmed?

 

[iMike_G.]

yea i think his wastegate is shimmed a lil

 

[Zumtizzle]

you might wanna get a little crazy and pull your intake cam off and open the Throttle body.

theres a few more fun places boost can leak. (yes the egr cooler is one)

 

[SupraCorwin]

Yeah the BIC ddp is pretty loud when your wastegate opens, you will know exactly when and if it does.

 

[Rennat]

i only have about 3-4mm of shims... like 2 washers?... was just to raise boost from 6 to 8psi...

and yes, i know EXACTLY when it starts to open... kinda fun to only "crack" the vent tube so you get a neck snap reaction from people... haha

im some what sure i may know where i have a leak... but i did notice that with the downpipe i have just a tid bit more vacuum at idle... and my engine also pulls like 22-23ish now when im decelerating... i use to pull like 21. to me its a noticable difference on the gauge. but im still going to try another gauge while im at it.

i'll do the boost leak test thursday when i dont have work...

 

[Rennat]

Hows that downpipe sound? Must make hell when that wastegate opens, huh? :evil2:

My money is on a boost leak....is your wastegate shimmed?

i cleaned quite the layer of "exhaust gas" from under the donwpipe... its now fully coated with at least 8 layers of VHT flame proof, wrapped fully, and then another can and a half of vht flame proof... cant even tell its a vented downpipe by looking at it! and with the heat shield on, looks "stock" if thats what you wanna call it... hahahahaha

 

[Poodles]

Yep, heat sheild is over mine and it passes inspection...

Take out the shims :rofl:

 

[Rennat]

Yep, heat sheild is over mine and it passes inspection...

Take out the shims :rofl:

even if i remove the shims... that'll just lower the boost and mask the problem... having shims vs. a MBC shouldnt be any different...

although i think i might remove them anyways if i slap on the MBC that i have...

 

[Poodles]

I had to remove my shims when I went from stock DP to DDP...

 

[black89t]

shims are ok until you take them out.


then you'll have a stretched out wg spring thats even weaker then before. i say boost leak too. but i could be the hose to the wg. do you have hose clamps or zip ties on there? if not check that hose. it helped with the creep on mine.