T28 Hiflow Boost problem

[adam 32]

you got a dump pipe?

[macka]

Nope standard cast dump

gettin tuned tonight :-)

[turbomad]

Hey macka that's a good result and saves you heaps of $$$ not having to go external, even with the stock turbo and a Profec b I have to turn the balance knob all the way over to sharp as well as selecting the overboost setting on the back just to stop the boost from continually rising with rpm's, so you've done well.

[macka]

hehe boost problem is back

ill worry about it tomorrow looks like i will have to cancel the dyno tune :)

something funny is going on i havent done anything...

[Guest KILLER-T]

Hey macka im in the same boat as you after my rebuild i have creaping boost i was told by one person that it could be that when the engine was put together that the ex cam could be retarded what ever that means does anyone know if that could cause boost to rise. anyway i hope that its just the wastgate actuator that is stuffed i got a new one today and i will fit it on the weekend. I will let you know how i get on

[macka]

post a mssg here or if u find out during the day u could give me a ring too thanks AQ

hope i sort something out im booked at psi @ 8pm fri night

[2rismo]

IMHO, it sounds like your wastegate is too small and the quick fix approach that you have taken, whilst being inventive, cheap and innitially effective has only lasted a while due to additional stress on the factory wastegate and actuator arm/spring.

If your turbo has been hi-flowed/different wheels installed then it is pushing out more air etc. If the additional pressure/volume is too much for the standard wastegate to get rid of, your boost will rise as if the wastegate were partially closed. Remember, the wastegate is there to get rid of additional boost pressure.

** Imagine you have a 10mm Nylon garden hose. You have always pumped water (air) @ 5psi through this hose (turbo) as that's all the nozzle (wastegate) on the end will allow. The water supply (exhaust gas) however is making much more than 5psi pressure. If you hi-flow the hose to 12mm, you would expect additional water (air) to flow through at a higher pressure but if you still have a nozzle (wastegate) allowing only 5psi there HAS to be an increase in pressure on the water side (inlet side) of the equation. **

Basically you have increased the amount of air that is flowing through to your motor. The wastegate that regulates the AMOUNT of air delivered to the motor is being forced to work too hard with too much air being forced out it before it gets a chance to reach the motor with the unfortunate side-affect that some of this air does. This is where your increasing boost is coming from as you get up in the rev range. I would suggest that it will get gradually worse as time goes on and the additional stress takes it's toll on the turbo components.

The addition of a helper spring will help to the extent of allowing the wastegate to open sufficiently to allow this excess air to be released from the system but will obviously only work as far as the standard wastegate can go. Ultimately, get an external wastegate.

Sorry for the vague and incomprehensible analogy. It's all i could come up with @ 4:31am...

Cheers.

[macka]

Isnt a helper spring going to hold it closed not keep it open?

Ppl use a helper spring when they are losing boost i thought

[Jay95R33]

In some cases part of highflowing a turbo is to increase the size of the wastegate port so it can sustain the higher volume of air being passed through it, thus holding boost preasures down.

I'd say this was either not done, or it was done but the increase in flow has exceeded the capabilities of even the modified wastegate.

Basicaly - big bumer......

[Guest KILLER-T]

I put a new actuator on my car today and it fixed my creeping boost problem i think all the oil and crap in it must of done something to the diaphram :confused:

[macka]

Details please of the actuator adam.

How many pound actuator how much where from cheers :-)

So yours was doing the same as mine hey... mine starts at 10psi then rises to 14 by 7000rpm

[Guest KILLER-T]

Well my car has that turbo of a s4 rx7 so i went to rotomotion and picked one up for $30 the min boost i can run is .85bar like it was before with no creeping

[macka]

Did you pull both actuator springs to feel the difference?

I gotta try something its driving me crazy, hey Brett (PSI) told me i need a new Fuel pump as well he didnt tune my car went on friday and put on dyno, so still have a few things to sort out.

whens yours getting tinkered with?

[Guest KILLER-T]

Im going out to see jeff from C-red tonight we are doing a deal for some Sard 550 injectors once they are in i will get the tune up i dont think it will need alot just change the fuel map a bit.I was thinking last week that it all should be ready for the drags by the end of this week but it looks like it will be more like 3 weeks away but it will be worth the wait:uh-huh:

[adam 32]

macka: is your fuel pump tired/dead

or just not keeping up with the fuelling task required??

cos i know replacing the fuel filter and getting biger fuel lines can make a difference here....

[macka]

Adam32

well thats just the thing i dont know?

I guess the dyno says its leaning up top but isnt that what a safc is for to enrichen or lean it out? He just looked at dyno and said need new fuel pump?

I should hope i dont have to change my whole fuel lines that sounds very costly!

mm fuel filter maybe but i think im clutching..

KillerT u bastard i want those injectors :uh-huh:

what about my other questions?

[adam 32]

yeh theres lots of other solutions to leaning out up-top....

and that was at 10psi!!!!

[Guest KILLER-T]

I think Hendo is playing it safe with your car Macka it would be a shame to lean it out and pop a piston.Did brett do a few runs on the dyno because you can see if its your fuel pump or not. If it is your a/f mix will get leaner with each run well mine did anyway:confused: and as for the new actuator they felt about the same i think my old ones diaphram had a hole in it or something :eek:

[macka]

I like them big up top not lean :-)

yeah he did 5 runs but its expected to lean out it has to at 1 stage so u enrichen the mixture but he seemed pretty sure about the pump even tho i couldnt see it..

I might have to try another actuator

[gtstii]

Guys, I've had the same problem, running the std turbo but with full exhaust, r34 gtt stock intercooler and slightly more boost.

I find that boost creeps up when stretching gears above around 4500 rpm. Please read my thread.

http://www.skylinesaustralia.com/forums/sh...&threadid=20562

any suggetions as to what is causing it? could it be my split pipe dump pipe? (the wastegate pipe is around 35mm internal diameter)

things to consider:

It doesn't seem to do it as much when the stock boost solenoid is hooked up?

It became noticeable when I fit the dump pipe.

It became worse when i fit the r34 gtt intercooler (more flow up top?)

My turbo is standard

only want to run around 11psi