4JB1T Different gears, different boost?

[moo]

Installed my boost guage last night as i plan to start winding up the turbo soon.

From what i've read on this forum, i came to the understanding that the average stock MU runs 10psi on the 4JB1T.

After installation, i've driven it a few times and i am experiencing the following results;

7psi 1st, 2nd, 3rd and up to 8psi in 4th and 5th.
comes on boost at 1500rpm and is at full boost just before 2000rpm

Has anyone else had the same results, or is something wrong with my Mu?

Cheers

- Michael

[holden]

I can get max boost in all my gears but its reving real high at that point. But Im not 100% sure my boost gauge is reading right. As I put my Manual Boost Controller in the vise to turn it up till it cant trun no more (allmost blocked up). But its only reading 16psi and the Manual Boost Controller should adjust from 1 psi to 30 psi ?

kane

[moo]

Thanks for the reply.

I have got a Turbosmart manual boost controller (not installed). My question to you is, when you upped your boost, did you do it yourself? or take it to a diesel mechanic or dyno tune it?

I'd prefer to do it myself if i knew how, due to the quote of $330 - $400 from the last place i called JUST TO TUNE IT!!

Cheers

- Michael

[holden]

Sept 26, 2008 14:18:40 GMT 11 moo said:

Thanks for the reply.

I have got a Turbosmart manual boost controller (not installed). My question to you is, when you upped your boost, did you do it yourself? or take it to a diesel mechanic or dyno tune it?

I'd prefer to do it myself if i knew how, due to the quote of $330 - $400 from the last place i called JUST TO TUNE IT!!

Cheers

- Michael

yeah I done it meself really easy to do. 14psi would be a good start if you have no mods.

[geeves]

You have to adjust the overboost valve on the inlet manifold to get past 16psi but the standard turbo wont go much over 17 anyway with the wastegate disabled. Anything over 12psi requires pump tweaks to get a benift.
First make sure your aircleaner is clean and you have no exhaust damage. Then disconect the pipe from the turbo to wastegate and block the turbo end. You should see about 14 - 17psi at full throttle above 2000rpm. Dont drive like this too far. Things that can affect this are . Guage not accurate,or cold start mechanism jammed. Your boost controller fits in the line between the turbo and wastegate and normaly is just a pressure bleed tricking the wastegate into thinking there is less boost than there realy is

[holden]

Sept 26, 2008 14:46:47 GMT 11 geeves said:

You have to adjust the overboost valve on the inlet manifold to get past 16psi but the standard turbo wont go much over 17 anyway with the wastegate disabled. Anything over 12psi requires pump tweaks to get a benift.
First make sure your aircleaner is clean and you have no exhaust damage. Then disconect the pipe from the turbo to wastegate and block the turbo end. You should see about 14 - 17psi at full throttle above 2000rpm. Dont drive like this too far. Things that can affect this are . Guage not accurate,or cold start mechanism jammed. Your boost controller fits in the line between the turbo and wastegate and normaly is just a pressure bleed tricking the wastegate into thinking there is less boost than there realy is

(You have to adjust the overboost valve on the inlet manifold to get past 16psi but the standard turbo wont go much over 17 anyway with the wastegate disabled.)

Where abouts is this overboost valve on the inlet manifold and how do you adjust it

(Anything over 12psi requires pump tweaks to get a benift.)

Is this a good idear with a standed exhaust (engine over heating). And where abouts is this screw to adjust fuel pump???

[Jimmu]

Mine pushed over 20+ pounds easily in every gear without doing anything to the over boost valve. Maybe the valve was blocked or broken??

It could be you need a bigger exhaust to push these figures easily.

I have since removed the valve.

Jimmy

[geeves]

If you look at the inlet manifold you will see a valve with a 16mm hose attached which goes to either the air cleaner or to the inlet before the turbo depending on the model. This is the overboost valve.

[moo]

I installed my manual boost controller last night. As soon as it was in, with boost turned all the way down, my guage instantly read 15psi through every gear, fuel was adjusted until it felt right and i've left it like that. It pulls like a 15 year old boy now ;D.

any ideas as to why it would jump so high? faulty controller?

Another question that comes to mind is in regards to the brass tee in place between the turbo compressor outlet and the wastegate actuator. What is it? does it block easily?

Cheers

- Michael

[geeves]

Within limits more boost doesnt hurt an engine so if it goes good why worry. Only risk is when you wind up the fuel you also increase exhaust temps if you run it hard for more than a few minuites at a time. This can cause broken turbos and crack heads although head cracking on the 4jb1 is almost unheard of. Only way to tell if your EGT is too high is with a pyrometer but these are very expensive.
The brass T doesnt sound original I have seen a brass bleed valve used as a boost controller although it is a fit and forget method I.E set it then leave it This might be what you have.

[Jimmu]

Take a photo. The brass T sounds like a boost controller/ bleed valve. But as you as asking what it is I assume it is not the controller you have installed. Where is your controller installed if not between the compressor housing and the waste gate actuator???

Jimmy

[moo]

Hi Jimmu,

No the brass Tee was there before any modifications that i have completed.

From the turbo compressor outlet to the wastegate actuator, inline with the hose is as follows - Boost guage feed, Unidentified brass Tee, then my Manual boost controller.

I'll endeavour to get a photo in the daylight tomorrow.

Cheers.

- Michael

[holden]

Just put a 2.5" free flow exhaust and running allmost 20 psi of boost from 16 psi and havent played with the over boost valve. must be broken

kane

[tealz]

What brand boost controller are you running? Try to adjust it so its almost wide open, if it still dosn't drop the boost pressure un hook it and run it like it was before (hose from compressor housing to waste gate). If it still dosn't drop the waste gate isn't opening fully. If you find that the gate is open fully it means that the wastegate can't flow enough exhaust gas. The boost should drop for you if you put it back to standard. If it does it means the controller is not working as it should.

[geeves]

surely the more boost the merrier.