Is this normal for a turbo

[Gianni]

This is my first turbo I have owned. I'm loving it
But my mate reckons it's not at it's full potential and something's nqr.

I'm hitting a little bit of boost just after 4k and full boost just after 6k. If I rev it Out of gear I get no boosting and no boving. But only a little bit of boost if I rev it really hard.

I know straight up that it should be boosting if I just rev it. My mate reckons my motor should be running boost alot sooner.

I guess it's almost like alot of lag. The vacc on the throttle body at idle reads at about 20-30 at times. Is that normal. Because I was thinking maybe there is so much vacc that it's pulling the bov open a little so it takes alot longer to reach some boost to jam it shut. if I'm not reaching a decent amount of boost till around 5 that's alot of time runnin off just vacc. And apparently I should e hitting boost Pretty much instantly with a td05

 

[JETGSR]

turbos rely on gas flow from the exhaust to spin the turbine which spins the compressor and produces boost.

when you free rev the engine is certianly creating gass flow but not enf force to spin the compressor fast enf to produce boost.

when you load the engine (ie drive it) there is effectivly more gas flow because more power is generated by the engine to make the car move forward.

So to make car go you need HP - HP = load apon the engine creating more gas flow
more gas flow (with a bit of push behind it) will spin the exhaust wheel harded which inturn will spin the compressor wheel faster hence making boost.

eg: on a hard free rev I can make 10psi of boost but if I progressivly increase RPM it wont make boost or very little.
but under load when more exhaust gas is generated through the quest for HP (to make the car move forward) the turbo will produce boost
which inturn creates more HP and the cycle contunes (there are wastegate in the cycle to limit the amount of boost - also physical limitations of engine and turbo that restrict the unlimited power figure )

the LAG that people talk about is really the compromise between how much HP you want to make and when you want to use it!
rule of thumb : the more efficent your engine cumbustion system is the sooner you will make good power in the rev range. but the physical real world comes to upset the game when you bolt that monster turbo on and expect it to spool at 2000 rpm .

Physics is a bitch!
generally a small turbo will spool early where a large turbo will spool later, although with little tricks and tuning tips and a bit of NOS you can get the biggest of turbos to spool nice and early, it just comes down to $$$ and smarts.

with regards to your LAG - you just might have a boost leak with that BOV or somewhere else but 5k is a little late for a little TD05
that turbo might need checking out too, if the compressor is damaged or worn that will make the system inefficent!

that physics thing working again!

start at the basics, that BOV should not be open at Idle. it should start to open on a light blip of the throttle (decel)
next check for leaks in your pipe work.

I hope this was a confusing for you as it was me ..

JetGSR

 

[DOUGMO]

I would think you should be full boost around 3000-3300rpm something is not right

where is you BOV line connected to? it should be on the back of the inlet manifold from memory?

free reving in neutral might see a little positive boost but not much

 

[Gianni]

Oh. My mates s15 boosts heaps just revving it. Mine just sounds like my NA used to. Like no spool. Um the bov runs into the front of the inlet mani. There is a spot on te back but that's blocked off

 

[khubner1]

you describe exactly the saem thing the cought me out when i first bolted on the turbo (but i could hear it spooling) you should certainly be seeing boost alot sooner. it may seem silly but are you at WOT accelerating or just gradualy upping it. i myself see full bost by 3.5 - 4 k (massive intercooler and piping have introduced some lag) by going WOT i gota getr onto 347-dis about what wastegate is on my turbo cause i'm seeing alot more boost than i should.

 

[evo-gsr]

Na not normal...Somethings fucked....?

 

[dafurn]

Also might be worth checking that your wastage actuator is holding the wastgate shut tight as tight. I used some washers under where the actuator mounts to the compressor cover to space it out and tighten the wastage flapper.

 

[JETGSR]

yes that would be the next thing - check the arm on the wastgate actuator and the (flappy bit!)
make sure it s fully closed

there should be (if you remove the arm from the pin on the flapper) about 1/2 a hole difference from the arm hole for the pin and the pin on the flapper.

it should be holding the flapper closed!

also internally the in turbo wastegate channel for the flapper I've seen bad cracking and deforming of that area which wont allow the flapper to seal.

this is at the worst end of the fault finding senareo


good luck

 

[Gianni]

Yeah. I've heard it could be wastegate. When I first picked it up i found the arm not attached to the pin. So I re attached it. I'll inspect it again.

When I last played with it the pin only moved back and forth a little bit with no effort. From here I'll try to unbolt the wastegate and put a washer behind. I'll see if that helps at all too

Oh and k. When testing the boost I'm talking full throttle to see how quick it boosts

 

[Gianni]

Whoops. Forgot I already started a thread on this issue. Ha ha ha

Alright. I've spaced out the acctuator and it is boosting and running heaps better. Well most of the time. Sometimes it doesn't feel right. Like advised above the waist gate wasnt closing properly. Now boost is kicking in heaps sooner and alot more.

But still only at about 5. At idle I get no boost and the bov is doing nothing.

 

[EVOCPE]

Post up engine pics of it installed, also post up pics of the turbo, vacuum lines, cooler piping

 

[EVOCPE]

Also, did u change the spark plugs?? if so to what ones??

Spark leads ok??

No vacuum leaks or loose cooler pipe clamps??

Cooler hasnt go any cracks??

 

[Gianni]

Nothing I can see. I'll take sone pics tomorrow I started another thread and someone thought blocked cat. I'll look inti that too

 

[milkandoj]

Try the washers under the actuator as mentioned, if not maybe the exhaust housing may be cracked around the internal waste gate port so its leaking bad so really slow spool.
Still id think a 16g even if its leaking would be on full boost before 6000 lol.

 

[Gianni]

Yeah did the washers. Made huge difference. But isn't still 100%

 

[Dean]

Nothing I can see. I'll take sone pics tomorrow I started another thread and someone thought blocked cat. I'll look inti that too

Test for boost leaks by doing a boost leak test instead of just seeing, blocked cat and an exhaust leak is def another possibility.

 

[LWNSLW]

You are driving it right?

 

[Gianni]

Yes. I'm driving it

 

[EVOCPE]

Are you driving it with your foot FLAT on the accelorator pedal?? or easing it slowly?

 

[Gianni]

Driving it when flat out. The gage reads boost. Like 1 or 2 psi when casually driving. Bit like I said. At idle going flat out I get nothing. No bov. Full throttle rev and needle doesn't move till about 6g