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Lazy R33

R338OY

By R338OY,
in Engines & Forced Induction

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R338OY Veteran

R338OY

Posted
Posted

Hey all,

Had my RB25 exhaust manifold repaired recently (broken stud) and a boost leak resolved.

But with the boost cranked to about 8-9psi i find there's no 'kick' and less response when i floor it. It used to launch hard before, but since the boost leak began and even after repair, the power has not returned.

My mechanic said i need to fix my timing. I.E. get an ECU retune/piggyback/PFC?

If it helps, my boost gauge under-reads at idle. It used to sit on -0.5 BAR all the time, but since then it's always sagged less than that. Even AFTER the repairs.

Any recommendations here?

Cheers :)

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R33fourdoor Enthusiast

R33fourdoor

Posted
Posted
"Had my RB25 exhaust manifold repaired recently (broken stud) and a boost leak resolved."

"My mechanic said i need to fix my timing. I.E. get an ECU retune/piggyback/PFC?"

Howdy R338OY,

Even someone with the most basic mechanical logic would be scratching their head at what your mechanic has suggested!

You told us that it went in for a basic stud replacement and to resolve a boost leak, however prior to this the car performed well. Now the stud is repaired but the car doesn't "go". All the mechanic can suggest is that if you want it to go again, you have to alter your timing and buy a replacement ECU!?????

Here are two suggestions for a start:

1/ NEVER go back to this mechanic.

2/ Let us know what area you live in and someone from the forums could suggest a REAL mechanic in the vicinity that can quickly diagnose your car and get it sorted once and for all.

I can't see, based on the repairs you had done, how the problems you were experiencing have anything to do with a fault in your ECU or your timing, otherwise your car would never have driven properly in the first place. Besides, the repairs you had done would have been accomplished without the need to touch either the ECU or timing.

The first thing that springs to mind from my limited knowledge together with the explanation you've given, is that there could potentially be a vacuum problem. If this fool has accidentally disconnected/crimped/blocked a vacuum line as a result of his fooling around, it could be messing with your wastegate actuation or the ECU could be responding to a lack of vacuum elsewhere and its interpretation of this could inadvertantly be causing the poor performance.

Have someone who knows what they're doing check out all of your vacuum lines first. It could potentially be the quickest, easiest and cheapest fix. If this isn't the problem, then work through the basics as there would be a simple explanation for this and it should be directly related to the repairs that were performed. By fixing the stud, the mechanic may have had to remove the entire manifold, which of course has the turbo and exhaust attached. If he has reassembed this incorrectly or forgotten to reattach something, the car could perform poorly as you would expect.

Don't look at anything else until you've checked these BASICS first (vacuum lines, sensor connections, mechanical connections..etc).

Hope that this has been of some help.

Cheers, Mike

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R338OY Veteran

R338OY

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Thanks for the responses fellas.

Yes i'm no expert, but i always thought the wastegate/actuator had an issue with building boost pressure. That's just the feel i get from driving it. It makes full boost but is lazy from low RPM's, i.e. it used to 'launch' when i floored it, now it's not that responsive. I can feel the lack of pressure from mid-->high RPM's too so it's obviously a small percentage of power being lost, but affects overall performance.

I'm sure it's not a complex problem. I'm going to have someone diagnose the issue, and someone who knows what they're talking about :devil: .

Cheers

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alwaysdreaming Proficient

alwaysdreaming

Posted
Posted

hey guys im new to driving skylines as i have bought my first just recently (r33 gtst s1). the one thing i need to do is replace the exhaust manifold, but i need some advice as i dont want mine to lose power after some mechanic plays with it.

1st question is should i go all out and get an aftermarket manifold such as a hks one or just replace it with stock?

2nd question is could any1 give me an idea of how to replace it myslef?

thanks in advance!

ps... good luck with fixing the problem R3380Y

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R338OY Veteran

R338OY

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hey guys im new to driving skylines as i have bought my first just recently (r33 gtst s1). the one thing i need to do is replace the exhaust manifold, but i need some advice as i dont want mine to lose power after some mechanic plays with it.

1st question is should i go all out and get an aftermarket manifold such as a hks one or just replace it with stock?

2nd question is could any1 give me an idea of how to replace it myslef?

thanks in advance!

ps... good luck with fixing the problem R3380Y

IMO you need a mechanic to replace it if you're not experienced. The mechanic took pics of mine and there's all these wierd studs to move, and you need to know how to remove the turbo, plus intercooler piping, without damaging anything. Plus if you do up the manifold studs too tight they can break off and you're screwed again.

From what i know the stock manifold is top stuff for being stock, and you won't need an expensive HKS one unless you want to A) Run massive boost B) Install something lighter. It's effective and solid.

r33boy, maybe check the tension in the wastegate actuator.

How do i check it? Thanks for the advice.

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Adriano Grand Master

Adriano

Posted
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I would disconnect the wastegate arm from the flap pivot on the exhaust housing, you need to check 2 things, the preload(how far you have to pull the "arm " out of the wastgate can to hook it on) it should be about 2mm. The other thing to check is the tension of the spring in the wastegate can, pull the arm away from the can, you should be able to move it 12-15mm but it should be quite hard to do so. Some other potontial problems with the wastegate can be a badly cracked exhaust housing/wastegate flap or a wastgate flap not seating properly, all these problems will cause slow boost build.

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R338OY Veteran

R338OY

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lol you need a mechanic to take a turbo off and intercooler piping what a joke

The dude i replied to just bought his Skyline. Not everyone is as expertly experienced as you mate so, like i did, give out sensible advice that will help other drivers maintain their cars.

I would disconnect the wastegate arm from the flap pivot on the exhaust housing, you need to check 2 things, the preload(how far you have to pull the "arm " out of the wastgate can to hook it on) it should be about 2mm. The other thing to check is the tension of the spring in the wastegate can, pull the arm away from the can, you should be able to move it 12-15mm but it should be quite hard to do so. Some other potontial problems with the wastegate can be a badly cracked exhaust housing/wastegate flap or a wastgate flap not seating properly, all these problems will cause slow boost build.

Thanks for the explanation, i'm going to investigate it asap and forever bury this problem! :D

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75coupe Grand Master

75coupe

Posted
Posted
hey guys im new to driving skylines as i have bought my first just recently (r33 gtst s1). the one thing i need to do is replace the exhaust manifold, but i need some advice as i dont want mine to lose power after some mechanic plays with it.

1st question is should i go all out and get an aftermarket manifold such as a hks one or just replace it with stock?

2nd question is could any1 give me an idea of how to replace it myslef?

thanks in advance!

ps... good luck with fixing the problem R3380Y

use a stock manifold making sure it aint cracked and change it yourself, its not that hard.

locate manifold and remove. replace manifold, if your worried about breaking studs use a torque wrench ($50). just be gentle don't use to much force on anything.

Make sure you are careful undoing the manifold as this is when you are more likely to break studs. use alot of wd40 when engine is cold and do a couple of time over 30mins to let it soak in before undoing the manifold...

you will learn alot and feel good when you finish and if you stuff up or studs break you will learn more... all good...

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R338OY Veteran

R338OY

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you will learn alot and feel good when you finish and if you stuff up or studs break you will learn more... all good...

Don't break the studs. If you're that unlucky you'll have to get the stud drilled out (as was done to mine) and there aren't many thread-drillers in Sydney. If you need a contact for someone to drill a broken stud i have a number you can call.

A fresh manifold gave me a massive improvement to building boost.

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