i have a percision 67/76 on my b18 using a neukin ram horn mani. with a 38mmtial wast gate. trying to just run 15lbs for right now & with a 10lbs spring it wont even hold that. it slows down the spool but the higher u rev the boost goes up. im thinking of cutting off the pipe comming off the mani & putting a 46mm on. i would think that would hold up?

 

when does the turbo start to spool/hit max boost? the 38mm should be fine. the larger wastegates allow for better boost control like preventing boost creep that sort of thing

 

are you using a controller? if so FIRST, run the gate directly to the compressor. see if that helps, if thats the case it is the controller. if it still creeps, you may need a larger gate.

 

what kind of manifold u have?

 

i'm confused on what the problem is exactly. is the boost creeping or are you not hitting enough boost?

 

sounds like creep.. try what boostedcivicsir said and report back

 

yes it would hold up with a larger gate

 

its usually a manifold design problem, seen it 69087987 times. a larger gate wont help much if the exhaust isnt getting TO the gate. 2 wastegates is usually the easiest solution.

 

im trying to keep boost at 15lbs. i have a controller but im not using it. im letting the spring open as soon as it can witch should be 10lbs i can take the hose off the top of the wastgate so its just on the spring u can hear the gate open cause its loud as hell. but the higher u rev the higher the boost goes up. spring in thier .im only reving to about 8g. the boost comes on around 4500rpm. it just seems like the turbo has 2 much voluve for a 38mm. as if it cant get ride of the air fast enought. i called precision they said that i sould use at least 44mm. i didnt tell them im trying to systain 15lbs but u would think the 38mm would hold at leats that.
heres a vid on the dyno u can hear the gate open. ( good rims are getting powdercoated )
its a neukin manifold i thought they made good ram horn mani.
http://s45.photobucket.com/alb...6.flv

aslo just running on the 10lbs spring it has crept to 17lbs then we got off it.

aslo a pic of my setup. the wast gate comes right off the collector & thiers only 3/4 gap between it & the man



Modified by ALL IMPORT at 3:57 PM 8/7/2006


Modified by ALL IMPORT at 4:04 PM 8/7/2006

 

my 38mm wastegate is doing the same thing

8psi spring in, and it creeps to 10-12

 

your going to need 2 gates

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C1CYA &raquo;</TD></TR><TR><TD CLASS="quote">your going to need 2 gates </TD></TR></TABLE>
Negetive- Everybody and there mother has a ram horn manifold with a single wastegate these days and has no problem controlling boost. Try upgrading to a Tial 44 or equivelent, using a better boost source, and try something different with the dump tube.

 

exactlly you just need a bigger gate... that turbo wants to make more than 15 psi. you need to gate that extra energy. if you were running 25-28psi that gate would prollly work though. Step up to a 44

 

ya thats what we were thinking, the turbo is just starting to come alive around 15psi & thats why it wont hold it wants more. i orderd a 46mm tial it should get 2 us by thursday. so do u think i need to just change the flange on the manifold or should i change the whole piece comming off the manifold & make the hole bigger all the way. does that make since? its only about 3/4 inch long comming out the mani.

unfortunatly this puts a big dent in the moroso event plans. i wanted to go to the track friday & see how the car acts, but hey i guess thiers always next week. just wont be in the 10sec area.

 

with a turbo like that 2 gates would be better , the exhaust wheel is so effecient that it flows more than the gate will , + to buy another 38mm it will be cheaper than buying a 44mm

 

I'm wondering if you really have a 10psi spring in there.

I was running a T4 Ptrim with my old SC61, and my 38mm would hold 8psi just fine. I was using a lovefab minime manifold.

 

just change the flange since you prolly have a v-band now.... At the shop we had a 35r on a 2.0 ls/vtec and we could not tune it on pump gas with a 38MM gate it kept creeping to high. We got a 60mm hks gate and all i did was cut and change the flanges on the manifold.. Works fine now car holds whatever boost you want..

 

isnt the flang hole going to be to big it will slide right over the pipe. but i guess is u put a 60mm on a 38 hell 46 aint no prob. just hpoe it will still flow.

already orderd a 46mm so thats whats going on now.

 

The bigger gate might help. I'm not sure why, but i've seen boost creep more with Neukin manifolds than any other. I've never seen the inside of one, but i assume it's how the hole is mated to the collector, or how high up on the collector it sits. I tuned a car with a neukin top mount and it boost crept really bad. Tial 44mm gate, SC61 and open 4" dp. With a 10lb spring it would hold it until around 7k and then it would just go crazy, it was hitting 24psi by 9k. No boost controller, gate directly to manifold pressure. It has to do with the design of the manifold and the air not wanting to make that turn into the gate.

 

I agree with Tony, that it is the fault of the gate. But don't let the 38mm number fool you. It comes down to the amount of lift that the valve has. Turbosmart claims a high lift valve. Someone might want to call Tial and Turbosmart and ask them what is the maximum lift of their valve. At least if you don't have to re-weld a flange, you can just buy a different gate.

 

i hear what u say about the mani not flowing. the wast gate is right on the turbo flange just like other mani. im going to cut the mani open to 46mm & put a 10 degree pitch going down so it flows in a little better. i cant see 3/8inch making that much diff in diameter but i guess it does.

i already fabed up the new dump tub & have the new spacer peice made for the mani. just waiting on the new flanges.the tial 46 is in rout if it ships today we will have it tomrow. cars going up today.car should be back together friday if it goes as planed

 

Larger gates are better at controlling lower boost pressures. BUT if your 38mm WG isnt controlling 15 psi then you have to much manifold pressure, Are the runners small in diameter inside? Is there any blockage in there? What a/r turbine housing are you running? What exact turbo is it ? My buddy runs a 35mm WG on 9 psi and NEVER has a problem with it. hold 9 psi steady through the rpms. really sounds to me like way to much pressure in the manifold.

 

i think with a pt67/76 it doesnt want to make anything lower than 18-20lbs period. its perty simple i guess if u think about it. a turbo this size u got to think of volume of air your moving at even 10lbs. 38 just cant keep up.i think with the new setup it will at least get me to 18. i wouldnt care if low boost is 18lbs as long as it stays thier. but at 7500rpm its up to 17 1/2 & i dont want to figure out the hard way

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ALL IMPORT &raquo;</TD></TR><TR><TD CLASS="quote">i think with a pt67/76 it doesnt want to make anything lower than 18-20lbs period. its perty simple i guess if u think about it. a turbo this size u got to think of volume of air your moving at even 10lbs. 38 just cant keep up.i think with the new setup it will at least get me to 18. i wouldnt care if low boost is 18lbs as long as it stays thier. but at 7500rpm its up to 17 1/2 & i dont want to figure out the hard way </TD></TR></TABLE>

This is true, id say try out the larger gate. Keep your eye on it and if you still experience boost creep then your manifold pressure is way high and you need to get a different mani. But the pt67 is large BUT should still be able to flow lower boost pressures with no issues

 

Doesn't work that way man, boost creep happens when ex manifold pressure is too low. With high backpressure, the air will be more likely to make the turn into the gate because there's more of a pressure differential.