onefastmx5

iTrader: (6)

Well last night I got on it and saw 4psi (no idea on rpm but not redlined) and I backed off because i'm still on stock injectors. It started chirping the tires

Now its time to put in my 42lb greentops and start tuning/datalogging!!

Vetal

iTrader: (3)

so what pressure drop do you measure now?

onefastmx5

iTrader: (6)

I'm can't say exactly for sure, but I would guess 1-2psi. Once I get started datalogging and ensure I have proper fueling, I'm going to know exact numbers. My eye is more focused on the wideband now, rather than the boost gauge because 24lb inj isn't enough fueling for it.

Vetal

iTrader: (3)

onefastmx5, update on this?

Vetal

iTrader: (3)

A little update. Tested again tonight. Upped the boost a little, at the turbo it shows max 16psi dropping to 15psi at the top, while in the manifold I get max 13psi at 3200rpm dropping to 9psi at 5700.

Vetal

iTrader: (3)

Any comments on these strange results? Look TOO bad. Any other way to test intercooler?

Fb0dy0nly

iTrader: (10)

Its gotta be leaking somewhere, that pressure just cant disappear in the piping...either you have it escaping somewhere, even hairline cracks, or your WG spring isnt holding tension enough for the boost. Wish I could be more help. Hope you figure it out.

Monte4ever

iTrader: (2)

Looks like you're getting close to the same results with two different intercoolers. There has to be something else going on. I have not fired my car up yet but I went with the cxracing intercooler. I've heard nothing but good things about them.

Vetal

iTrader: (3)

it's directly rpm related so not boost leak, it holds 13psi in manifold on low rpm but only 9 at the top

Monte4ever, it's still the same cooler. Didn't change it yet, spent this season swapping 4L80 in

Monte4ever

iTrader: (2)

[QUOTE/] Monte4ever, it's still the same cooler. Didn't change it yet, spent this season swapping 4L80 in [/QUOTE]

Oh ok....my fault. If or when you change it out try the cxracing one. Most has had very good results with it.

Vetal

iTrader: (3)

I've drilled ports directly on the pipes going in and out of IC, today I'll try to test once again. I might even put differential pressure gauge on it if I have time

Old Geezer

iTrader: (3)

"while in the manifold I get max 13psi at 3200rpm dropping to 9psi at 5700."

Have you checked back psi? [Ideally, should be <2X boost]
Could be: @ 3200 the exh volume is producing close to 2x, and at 5700, the ratio is well beyond 2X...

Also: I always check the w/g to see if it's working correctly. I have an adjustable regulator, an accurate gauge and a simple hose setup.
Using shop air, I "run" the w/g to see if it stays seated up to set boost...

Vetal

iTrader: (3)

I did check the WG when installed it (when on first boost it kicked out 23 psi LOL)
Didn't check backpressure, but in my experience boost pressure doesn't drop when backpressure raises...

JAX04

iTrader: (17)

i might have missed it, but are you using the 1.15 A/R TC78?

SPRAYED 01

iTrader: (22)

Yes it does. I had 4:1 back pressure vs intake pressure. Could not get over 11 psi with an 18psi wg spring

Nitroused383

iTrader: (10)

Excessive back pressure will cause the wastegate to open earlier. I ran a TC76 with a turbosmart 38mm with a 7 lb spring. I could hear the wastegate open really early and it would run 6-7 lbs of boost. I swapped to a PT76 which has a 83mm inducer / 75mm exducer turbine wheel compared to the 68mm exducer of the TC76 and boost would hit 15lbs past 5000 rpm. With the high back pressure of the TC76 it would flow enough volume of air out the wastegate to maintain low boost. Once my back pressure dropped the wastegate no longer could support my turbo.

I bet your back pressure is through the roof with that tiny 68mm turbine wheel on your 383. You need to be in the 87+ mm size.

Vetal

iTrader: (3)

Well, turbo specialists recommended me this TC78 for up to 900 crank HP, now I'm not even at 600 and you're saying my turbo is tiny and backpressure is over the roof? Not sure.

Yesterday did one more test. This time WG signal right on the first pipe coming from IC, and boost gauge directly before IC. Torque curve was much more linear this time.
What's more, I've put differential pressure sensor on both sides of IC piping, and it indicated 6psi difference before pipe blew off at 5000rpm, with only 9psi in manifold. Damn I love testing

JAX04

iTrader: (17)

900hp, sure, on a small cube motor, i was having back pressures issues on a 6.0 with 12lbs of boost, i cant imagine yours.

Old Geezer

iTrader: (3)

"and it indicated 6psi difference " DAMN!!

I haven't reviewed the entire thread, so this may have already been posted....
Bypass the IC, and see what happens.
If the 6psi IC pressure drop is accurate, it's time to pull it off and see wtf is going on inside.

Vetal

iTrader: (3)

Well, what could happen? I would not have pressure drop any more And 200F degrees IAT
I will dig out my runs without IC installed