don't know how you run the higher gears . I was out of gear in my nova with 3.42 gears at 150 mph . with a 1.76 glide. was about to go back to 3.23. on a side note I did help a guy with a ls3 turbo build and he had a 5.13 gear and 28" tire and it dynoed like ****. barely cleared 600 hp on 23 psi boost. he said it felt way faster with 3.23 so he swapped them back to 3.23 and ran 5.80 at 118 mph . couldn't even get 118 mph with the 5.13 gear at 7400 rpm.

if the converter is right it will 60' even with 3.23 gears.

 

How much back pressure with additional muffler? Gonna need more dome pressure to achieve same boost pressure with increase in back pressure. How much dome pressure for 6psi boost?

 

6 PSI at 6300 RPM? My 5.3/S480 combo was making more than that more than 2000 RPM sooner in first gear.

 

im wondering what the t56 guys are using for rear ratios

 

3.42-3.50 is what I usually see. Sometimes 3.73.

 

I don't run any dome pressure at the moment , just boost pressure to solenoid to gate .

is it common to need dome pressure to see spring pressure ?

 

Wrong thread.

 

If you were out of gear with a 3.42 your converter was slipping like crazy! lol. with a 28" tire that should net 170 at 7k'ish! losing 20 mph to slippage is terrible! I just trapped 158 about 7k with 3.6x gears. Which also happens to be in a 4.8 with the big 1.32 T6 S480.

As far as the OP goes... This setup just screams something is horribly wrong. You have the Baby T4 S480 on a 5.3. You should be able to make 20lbs b4 6k. Go back to the basics. it's not your gearing or your baby straight through muffler causing the main problems. You likely have a monster leak in your WG or plumbing. That and likely some serious tune issues. Not ot mention your Hotside is WAY oversized for what your doing. You could redo it in 2" and you'd be light years ahead.

I'm at 12lbs at 3400 on the 2 step and 21lbs in 1.2 seconds after I release the brake. That's on a 4.8... First I'd try removing the lower line on the WG completely. If there is no change, Try a block off plate on your waste gate. Obviously lift if it starts making moon boost fast. But I bet it's a whole new animal. If it still doesn't make boost address your charge pipe and Blow off valve. Do a pressure test and ensure they aren't leaking.

If your converter is setup loose enough down low, and if you plan on revving the motor high enough to take advantage of the short gear, I believe you'll basically pick up every time going to a shorter gear. But the car HAS to be setup for it. Generally taller gears favor a converter thats loose down low (to get into boost quick), yet "locks up" at a relatively low RPM as well. Generally these converters are 9.5" or smaller and expensive! Cheap 10" and larger converters don't generally lockup tight till 7k+. And at typical LS turbo power levels... some don't ever really "lock up" as they should.

My "street/strip" car runs a 2.73 gear and TH400. So I basically use it as a 2 spd glide at the track or when "racing" and just use 3rd for OD. Another great option IMO for a street car.

In the "Race car" I started with a 3.10 and 30" tire and shifting at 6500 or so. This combo worked great. but was harder on the engine loading it up with tons of boost at low RPM IMO. But it still squeaked into the 8's and I got 16-18 mpg. It was great on the highway! (glide) Every time I went to a smaller gear and coupled it with a looser converter, I went quicker. The car took less boost/effort to launch hard as well. I went to a 3.25, 15 stator on a 28" tire... Now I'm on a 3.64 gear and 28" tire with a 17 stator 9.5" PTC. I already wish I went with more gear and a looser converter...

IMO you have a good gear in it now for a street car. Address your boost issue and you can bring in more power than you'll ever use, quickly.

 

Crossover is 2"
Dump 3.5"

charge pipe checked for leaks all good. The cold side is very big I think.
3" out turbo into 3.5" ic tanks are 3.5" then Into 4" to TB.

how far can tune be out though. It's running 11.0 ish AFR through the boost. And timing runs from 20 at 0psi maybe to 14*@14#

 

That's much better hot side wise I just read 2.5" in your original post. That tune doesn't sound horrible but you should basically be on the NA tune up to 5psi or so. I won't tell you to push a pump gas setup as I don't want to be responsible! lol but read your plugs... Id bet you could lean that out and add quite a bit of timing. Then pull it out quick once it's "lit".

But again, something sounds way off. Pull the vac ref to the bottom port and just see if it makes a difference.. Try blocking off the wastegate too.

 

That's running e85 atm

 

Ok so put 26* in it to 5psi and lean it out to 12.0 in that area and see if it improves a ton.

 

Just to clarify

0#-5# 26degrees

5#-14# evenly drop to 12degrees

 

Ok so I have plugged the BOV , and ran gate direct to manifold.

@ 5800rpm
9psi boost gauge

ecu measured 9.4 on my data log
11.0afr
19* time

looks like it fell off but could just be a delay after taking foot off pedal..

I put some eboost control into that 30/100 to the solenoid and got 9.1psi on the gauge

 

So you ruled out the BOV leaking, thats good. Should still try to rule out the gate IMO. Did you install the "seal ring" under the WG valve? Verified the valve is 100% closed and opens with shop air around spring pressure?




11.0 is likely overly rich. ESP. when your trying to build boost quickly. In my experience the turbo basically needs to be hit hard initially to get it "lit" then you can taper off the timing and richen the fuel back up. Once it hit about 5-6psi, boost basically takes off like a rocket. You aren't likely to hurt anything at low boost on E85, so you can *usually* get as aggressive as needed with an "NA like tune" till 5lbs or so. I can't say what your combo wants... It may want 11.0 or 12.5... It might like 19* or 32*... I target 12.5 up to 5psi and run 26* Then I taper back down to 12* at pk torque and interpolate between the 2 for a nice even ramp down. Then I ramp back up to 16* at red line and interpolate between again.

Do you have a 2 step? CAn you attempt to start building boost from a stop?

 

thanks for the help.

i think the gate is fine to be honest , zero boost leaks to 15psi on compressor now . bov ruled out . and manifold pressure no real drop.

im thinking maybe its just the backpressure opening it up sooner than it should. al though i would have thought the boost controller would have helped there. i could try up the gate spring to maybe 20psi and see what happens , i doubt i will get that high so shouldn't be an issue .

yeah have a 2step an tbrake i could try also . just need some time cant do to much in surburbia here after work.

 

With the T-brake and 2 step it makes it ALOT easier to see where your "Sweet spots" are. I'd get that down first. Then work what you found it into your base tables for initial spool up from a roll. Takes me about 2 seconds to see positive pressure and I'm at 8-9lbs in 6 seconds where I launch at. That's a T6 S480 and a mild 4.8. Stalls NA to about 3500 and once boost builds it hits my 3900 2-step pretty quick. I honestly don't understand where the problem is, a mild 5.3 should light off a T4 S480 no problem. What "3500" converter are you using?

 

still haven't tried the brake just yet .
but.. .
so first I tried running the boost control to top and bottom ports with no luck , but I think my wastegate has leaking issues.
then I ran the gate disconnected from everything , so just spring pressure made around 9psi 5900rpm
so im thinking backpressure is def opening up the gate at 9psi.

so I ran a direct line from turbo comp to the top port on the wastegate and hit 13psi @ 5800 . so im on the right track here.
while on that , I always get a boost spike after I let off the throttle , that one got to 13.8 . is that an issue ?? set BOV to open earlier or no dramas.

ill do some more testing on the gate later .
its a brand new turbosmart 60mm, seems weird that it would leak

 

7 psi spring 0/100 ebc 6psi
7 psi spring 70/100 ebc 6psi
14 psi spring 0/100 ebc 9psi
14 psi spring gate d/c 9psi
14 psi spring compressor port to gate top port 13.3psi
14 psi spring ebc to top&bottom ports 50/100 & 90/100 solenoid around 9.8psi

im not 100% sure the wastegate leaks , plumbing into the cold side with my a/c compressor and turbo to w/g plumbed the system will hold 10psi without really any drop.

could this be high backpressure, the manifold has the exhaust coming forward , the gate is about a 45* angle and a 60mm valve from that and the turbo is at a 90* angle which makes me think the valve is recieving a lot of pressure.

im thinking more spring will make more boost, but putting 20psi seems a worry in case something does eventually work and hold closed.

 

Did you post a pic of the WG installed in the hot side?