Drop in turbo boost - how do i cure it ?

[donpulsar]

Right then, one for anyone who's technically minded about turbos. My spec for the turbo side is : Tubular Manifold, GT2871R, standard 0.65 bar actuator, 3" Janspeed Turbo Elbow + 3" Janspeed Exhaust system w/ 1 silencer. Boost controlled by GReddy Profec B (and yep, these have no atmospheric pressure control on them)

I had my Pulsar setup at Nobles Motorsport in Chesterfield and it was running 1.6 bar of boost. (It peaks at 1.6 then slowly drops, was told it was how the boost controller worked.) I then drag raced at York a couple of weekends after, and was running 1.45 bar boost, even tho' i had not touched my Profec. After steadily experimenting i got the boost upto 1.6 bar, but only by winding the Profec right up to what should've been 2.0 bar.

Now, I am aware that atmospheric pressure etc can effect boost levels etc, but can anyone please suggest ways to either a) compensate for the atmospheric pressure changes or b) suggest ways to increase the boost using the Profec with something else ?

For a) i was considering some description of setup like the Renault 5 GT Turbo has, i.e a twin port actuator setup and for b) either a bleed valve in the actuator line, a pipe with holes in or do i need a stronger actuator or a different boost controller ?

Any ideas welcome!

Cheers,

donpulsar

 

[youngsyp]

I don't understand why the Profec won't hold boost at its set target boost level ?!

By not holding consistant boost levels I'd think the unit was faulty or, you have a small leak somewhere. Does it have an extenal boost sensor at all ?

Of course, you're actuator could be the culprit. How old is it ?

 

[Rishi]

This will probably be down to duty..

Try this:

Road Driving:
Go out in the car, ease up in to 4th gear and just put your foot down.. See if you get your 1.6bar...

Drag Racing:
When you drag race i think its to do with the lesser load under that kind of accelleration - not sure - but you will not get the 1.6bar as setup on the RR or normal road mapping.. To achieve this you will need to add in a lot more duty to the boost controller to get this in a drag environment. Note that if you pile on the duty and then go back to road use you will find that your car will overboost...


Rishi

 

[donpulsar]

Cheers for the input so far guys

My actuator is just the standard 0.65 bar one, came off my original turbo. Had wondered about swapping for a stiffer/newer one.

Seeing as the Profec has a Mild -> Sharp adjustment nob, I'll have a go with that....once the Quaife gearbox has been installed!

Cheers again,

donpulsar

PS Any more ideas - keep 'em coming !

 

[DannyGTI-R]

I had the same problem with my acvr it would hit 1.5 bar at 4.5 rpm but could not hold it and then slowly dropped to 1.2 through time I realised it was the actuator as my boost controller was flat out. I have now changed the actuator for a uprated one and the car is so different, it comes on boost so much more agressively and holds 1.6 bar all the time and my duty cycle is alot lower.
Crap job though, manifold off but what job isnt on these cars.