Tial 38Mm Mvs Boost Creep When Trying To Tune The S15

[Mr. Pav]

Hey guys, I posted this on nissansil but i seem to find a lot more people using sau, a lot more mature readers to.

Basically went to get my s15 tuned today, sr20 standard bottom end all the fruit, high mount steam pipe manifold td06sl2 20g 10cm (kando in t2 platform) tial 38mm mvs gate.

Issue is, using a .6 bar spring, as it ramps it's ramping to about 1bar of boost then as it increases from 4grand to red line it boosts to around 18 psi.

My theories are - wastegate size could be to small but from everything i have read, there is no issues using a 38mm wastegate to control 18psi on a turbo of that size (very similar to a 3071r if your not familiar with mitsi ranges)

- wastegate is fingered or fake - did pull it apart, diaphram looks legit and paid quality money for it.

- position of wastegate on manifold isn't getting a decent amount of flow to the actual wastegate

- scrap car and buy an r35 gtr

sorry for the novel, help me sau!

here's a pic of the manifold i got made for an idea of what the gate position is like - doesn't look to bad to me

[HYPED6]

It should work, ish

Gate pipe positioning is not great, what is the transition like inside the manifold.

Imagaine how hard it is for poor old cylinders 1 and 4 trying to muscle through cylinders 2 and 3 to get out the screamer.

Can you just run 18 PSI? Or run the engine with no gate. I have seen 10 psi doing this on crappy manifolds.

[KiwiRS4T]

^^^like he said gate is supposed to get priority over turbo - like this:

[GTScotT]

I responded to you on NS, DVS JEZ on here might have some input.

Where he at

[Mr. Pav]

well i want to run 18-20 psi... but im only achieving that by 7k. if i add more boost to actually get a nice climb in 18psi around the 4-5k mark.. by the time it's reached redline it's creeped to about 24+ psi

[Simon-S14]

Id say the gate is too small

[Mr. Pav]

this is a thought... the screamer pipe actually snapped off before the tune so it was only about 10/15cm long instead of the 50cm off length in the picture. would that play a part in the equation at all

[Simon-S14]

Nope.

What sort of power its it making?

[Mr. Pav]

230kw with a shotty boost graph that ramps to 14psi and creeps to about 17-18+ by redline with very few degrees of timing

[scotty nm35]

Lack of timing and gate too small = overboost.

[Mr. Pav]

never thought the timing would of been an issue... reason i pulled some timing out was because it was knocking with all the boost creep

[scotty nm35]

As i'm running an auto I sometimes hit the limiter, so my tuner gave me a soft limit between 7 -7.5k. Every time I hit it my turbo overboosts to over 30psi.

Ethanol is your answer.

[SimonR32]

First, as other have said primary pipe 90deg to the gas flow is not ideal

Secondly, looks like the primary pipe for the gate is smaller than the v-band and then the screamer pipe is smaller than the v-band?

So while you have a 38mm gate, you are putting a restriction before and after the gate.

I would start by getting a bigger primary pipe and screamer pipe to actually the same size (or slightly larger) than the v-band

Edited November 22, 2012 by SimonR32

[Mr. Pav]

it's the same size as the resessed part of the vband that i normally see welded to. i don't know.. im thinking if i take the manifold off and have to weld it i will just sell up the 38mm and try a 44