Fabrik8

Bigger fuel lines never hurt anything, and the stock pump should be able to handle a decent amount of flow. If you want to get a different pump, think about getting a modest sized Walbro or a B16 pump (99-00 Civ Si, etc). A gauge would help, but if you don't have an adjustable regulator, don't get one. All the fuel tuning you need to do (for the boost range you need) should be done in the ECU, not by messing around with an adjustable fuel pressure regulator. The higher the fuel pressure from the pump, the higher the pump load and the lower the flow.

troy2003

i follow all the advice, i am running the aem fic, and im tuned at 10 psi....im just going to drop the new diaphragm and spring in and monitor the boost during a drive tommorrow, if its not a boost spike issue then it is a fuel delivery issue, thanks for all the input.

troy2003

ok, so i swapped to the new 38 mm wastegate with an 8.7 spring and im holding good at 9 lbs of boost, and i spike to 14-15 psi after about 4500......im lost with this.



p.s. no longer are the boost lag issues, im boosting fine, but after a certain rpm my wastegate is leaking way too much boost...., any help?


p.s. again, i also swapped the wastegate diaphragm with the tear out with a brand new tial wastegate diaphragm.

Fabrik8

I'm confused.. What do you mean by "leaking too much boost"? Do you think that you're having a problem getting the proper signal to the wastegate? I'm not really sure what you're saying. So you have a Tial 38mm wastegate, and you've just replaced the diaphragm, and you're still having boost spike problems above 4500 RPM at full throttle? When are these spikes happening, and are they actually short spikes or are they just the boost climbing too high and staying too high?

Are you using anything other than the wastegate to control the boost pressure, such as a boost controller, etc? What's the rest of the setup?

troy2003

no boost controller, just the wastegate with the 8.7 lb spring, and i am spiking around 4500 to 15 lbs.......as far as how long it holds 15 i dont have the balls to find out on a 2azfe....., my engine platform is a bit weak ya know, so i get off as soon as i see 15.

Fabrik8

That doesn't really answer the question. Is it gradually climbing to 15 psi, or does it just snap to 15 psi very fast?

troy2003

it holds steady at around 10 and then snaps to 15

Fabrik8

Hmm. Well, did you get your wastegate from a reputable place so you're sure you have a real Tial, not a fake one? I don't know enough about the fakes to spot them, so don't ask me for help on that one. I've heard all kinds of stories of fakes being manufactured badly, and not performing properly at all or not performing properly with genuine parts. That's what happens with fake parts though. Probably not the problem, but worth mentioning I figured.

So there are a few things that could be happening when boost climbs that fast. Where do you have the boost reference line coming from? Is is coming from the turbo, from the intake piping, from the intake manifold (after the throttle), etc...?

Also, what type of manifold is it? If the wastegate port (from the manifold) is not able to flow enough, or the wastegate exit (to the exhaust/downpipe) is not able to flow enough, the wastegate may not be able to control boost properly. I'd look really hard at your manifold design and downpipe design, and see if there are any easy to spot problems.

There are usually good reasons that a wastegate without a boost controller is unable to regulate boost, and most of them are fairly easy to pinpoint just based on installation. I doubt that you need a wastegate with more flow, because you don't sound like you have that big of a turbo. Unless there is someplace where the flow is going supersonic or the turbo is surging, there shouldn't be a boost spike problem caused by wastegate flow. A wastegate not getting controlled properly is a different story. A boost creep problem can definitely be caused by wastegate flow.

I would say that you might have a vacuum leak between the wastegate and whatever the wastegate is referenced to, and that would mean that the leak is somewhat pressure dependent (which is fairly common). That's very easy to just replace the vac line(s), obviously. Otherwise, I would look at things that can cause boost creep.

I guess what I'm getting at is that you most likely don't have a boost spiking problem. You likely have a boost creep problem, or maybe a boost spike followed by boost creep. Boost spiking is a transient condition, and usually only very short (it only lasts until whatever part of the system is reacting slowly catches up).

What size/type/flavor or turbo is it, and what engine?

troy2003

it is a mitsubishi td04 .60 trim, and its on a 2azfe scion tc engine....i will inspect the manifold and vacuum lines today, thanks man.