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When should my car hit full boost?

joh21m

By joh21m,
in Engines & Forced Induction

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joh21m Collaborator

joh21m

Posted
Posted

Hi All,

I was looking at my dyno graph the other day and i noticed that it only hit max boost (13psi) at about 4300rpm. Any ideas y its so late??? I still have the stock turbo on my rb20, i thought it would of hit full boost earlier then that???

Anybody know y it is coming on so late or is this normal???

Thanks,

Joh

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paulr33 Grand Master

paulr33

Posted
Posted

is it completely stock? you can make it come on boost earlier by letting the engine breath more. boost is a resistance to air. let it breathe more and it will make more power and should come on early. a nice big dump pipe followed by a 3" front pipe'd exhaust with a big cat should make it come on a little earlier

joh21m Collaborator

joh21m

Posted
  • Author
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what are u using for boost control - EBC or bleed valve or other ?

gfb bleed valve.

so its failrly normal then??? the car runs fine and is quick, im just wondering if its normal to come on that late coz wen i read other posts about the hks, garrett turbos they say full boost at like 3500rpm...

TurboX Mentor

TurboX

Posted
Posted

Have you got the wastegate actuator pressure input directly routed from the intake manifold? If not its probably dumping bypassed gas too early and opening before the manifold sees full boost. Doing this made quite a difference to my GTS4 RB20DET in response.

joh21m Collaborator

joh21m

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  • Author
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Have you got the wastegate actuator pressure input directly routed from the intake manifold? If not its probably dumping bypassed gas too early and opening before the manifold sees full boost. Doing this made quite a difference to my GTS4 RB20DET in response.

by pressure input do mean the pipe that the bleed valve goes inbetween? not 100% sure wat you mean by this...

joh21m Collaborator

joh21m

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In my opinion I reckon its a little late if you are still using the standard RB20 turbo. Even in dead standard condition Im sure it should be seeing 13 psi before 4,000rpm.

I have a T3/TO4e on an RB20 and 16 psi is seen at 4,000rpm.

yeh thats wat i mean, bigger turbos then mine are spooling up faster so i was a bit confused...

Cubes Grand Master

Cubes

Posted
Posted

I used to have 1bar by 3500rpm under general driving conditions on the road, on the dyno or up a hill in a high gear it would make 1bar slightly under 3000rpm.

EDIT: hehe used to.. :)

Now the bastard small arsed turbo boosts too early and creates surge under ~1700rpm with 9psi.

It can make 12psi by around 1600rpm in a high gear but nasty pop noises and bucking occurs.

There's no replacement for displacement. :)

paulr33 Grand Master

paulr33

Posted
Posted

what a nuts setup you have. full boost by 1600 is awesome :zap:

ive been for a drive in the xr6 turbo mark 2 and its pretty much the same

in stock config boost by 2200ish, no lag at all just good power all the way through. go the rb30det

Cubes Grand Master

Cubes

Posted
Posted

lol yer its the rb30det.

If you have ever driven a Late Model Nissan Patrol 3.0TDI it has the same power range feel as that but obviously much more gutsy everywhere.

4400-4950rpm peak power actually is not fun as the gears are too short and you don't get to wind them out. :)

Its awesome around town, easy pulls harder off the line than v8 commodores by simply letting the clutch out and accelerating. Wheel spin is a problem at the moment as it comes on so hard so low in the rev range.

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