R33 Boost Problems

[adikt]

S2 R33 GTS25t

So ive done a few basic mods:

FMIC, boost controller, fuel pump, pod filter.

Ran mint after being tuned, no worries at all, reasonable power.

Running 10psi boost, stable & good.

Then i went & did the exhaust (yes i know i should have done it first, had cat back before, did front pipe & dump pipe (with seperated wastegate pipe) this time).

Now its boosting to almost 1bar, about 13-13.5psi i think.

Tested wastegate, its holding boost/vacuum fine, opens at about 7psi, gradually opening wider until its open fully at 13psi.

Hooked wastegate directly to manifold vacuum, no boost controller in the loop, boosts faster/higher than with boost controller.

My intercooler piping doesnt have the nipple to plug the wastegate line into.

Also, it worked fine plugged into the manifold before i redid the exhaust, so i dont think thats the major issue at the moment.

This is on a stock turbo/ECU/wastegate/bov.

Now ive been told a few different things in the last couple of days, ive been told that

1) sweet as, everything can handle that boost fine, but with no boost controller, wastegate hooked to vacuum, should boost to about 7-9psi (which it doesnt).

2) i need to get the boost lower so the turbo doesnt fly to bits - possibly solved by external wastegate, or a restrictor after the dump pipe (which completely defeats the purpose of putting it in in the first place).

Now, heres where i need the help. Any ideas what the problem could actually be? And what i need to do to fix it?

If i need a new ECU, thats ok, but i dont want to get one only to find out i need an external wastegate/new exhaust/whatever as well.

I regapped the plugs (to about .78), took it for a drive & managed to blow an intercooler pipe off.

put that back on, and now it doesnt boost as high, so maybe that was the problem all along. will have to do some more testing later.

altho i always thought that a big airleak like a blown IC hose would lead to loss off boost, not increased boost. its a bit weird.

also noticed the timing is dropping RIGHT back (like to about 8deg) when under heavy boost (but only boosts to about 0.7bar now).

Thanks all

[adikt]

no ideas anyone?

this is driving me crazy, meant to be going to a dyno day in a couple of weeks, but doesnt look like ill be able to go atm

i found a wastegate calculator on here somewhere that says i should be running a 38mm wastegate.

anyone able to tell me what size the factory gate is?

[mad082]

i'd check that the wastegate isn't slightly grabbing on the dump pipe which is making it sticky and open later.

also i'd borrow someone elses gauge to make sure that your gauge isn't faulty.

and also get a nipple put into the cooler piping.

[WogsRus]

I have thesame issies on my car now. I got a gizzmo to try and fix the issues, as i had only a bleed valve before, but it seams there is another problem.

read this:

http://www.skylinesaustralia.com/forums/in...howtopic=146323

When i get any info i'll help you out

[adikt]

ive used my boost gauge + both vacuum gauges at work, they all read the same.

ill have to get a nipple put on the piping at some stage soon i think.

and re the wastegate opening, when i use the pressure gauge, it opens at about 7psi, so pretty sure its not grabbing, but might pull off the exhaust & have a go at the divider with the die grinder

[WogsRus]

Well i took my car in to have a look see into the problem. AND it the stock wastgate. What happens with my car is that at low rpm the car boost to 7psi and at high rpm it works its way up to 10.6 psi. With the gate fully open, i get thesame, this means the gate is too small.

SO i need to take the rear housing off and machine it. YEEHHHAAA. Dam it.

It's a common problem as hell, many people just don't warry about it, or their exhaust is not free flowing enough etc, etc. There are many such problems.

[adikt]

so you're going to machine out the wastegate housing? does that mean you need a bigger wastegate valve as well?

or are you just going to block off factory wastegate & go to an external wastegate?

i figured that was the problem, let me know how it works out.

[WogsRus]

juts machine the stock one. the issue is called boost creep. Think of the exhaust gas as watter, it is going to find the easies path out of the exhauts, so a tiny wastgate is not as easy as a free revving turbine, hence the creep problem. I am going to atemp and port mine, but if not, it cost 380 for a new housing ect to get done, and if that is the case pay an extra 400 and get a new turbo. I might just have to put up with 12 psi.

Edited December 8, 2006 by WogsRus

[adikt]

i was thinking id just fork out $600 & get an external wastegate & a new dump pipe. that would definitely solve the problem im sure, plus that will set me up for a new turbo in the future too.

altho i may have to spend an extra few hundred & get a new manifold too, which ive been trying to avoid so far.

would be good to see how you get on tho, as that might be the easier/cheaper way to go for now