Why does my boost drop ?

[B-Man]

Yep - SK you got it spot on ! That's what I reckon too !

[nv033]

did u try a 16psi run and see what the results on that was?? maybe then overlap it with ur current map...then see whether the 4psi extra boost is worth the extra stress on the motor because it may just be generating heat and posibbly 2-3 kw per psi..i think the guys are on the right track here....good work!! thats huge power for a 2835

[B-Man]

We are of the understanding that that the wastegate spring is 18 PSI - cause thats the minimum boost we could get out out of it when the 3040 was on.

Now if the WG spring is rated at 18 PSI - why is it dropping to 16 PSI ? Spring might be worn.

The converse of this is - If it is a 16 PSI spring - why were we getting a minimum of 18 PSI on the 3040 (and the 2835) from 4000 RPM to 5500 RPM then the drop off ?

I reckon this is wastegate related......

Its now a $$ versus HP gain decision on whether to go chasing it down.

[B-Man]

OK - I didn't get a copy of the test run with WG closed - but this is what the Power curve looked like (you can see what I mean bu the experly applied MS paint job I did on the graph)

With the Wastegate and EBC working 100% on the 20 PSI run, I would have expected a curve like this

Am I dreaming ???

[Sydneykid]

I would be having a loook at that lean out spot around 5,600 rpm.

[nv033]

We are of the understanding that that the wastegate spring is 18 PSI - cause thats the minimum boost we could get out out of it when the 3040 was on.

 

Now if the WG spring is rated at 18 PSI - why is it dropping to 16 PSI ? Spring might be worn.

 

The converse of this is - If it is a 16 PSI spring - why were we getting a minimum of 18 PSI on the 3040 (and the 2835) from 4000 RPM to 5500 RPM then the drop off ?

 

I reckon this is wastegate related......

 

Its now a $$ versus HP gain decision on whether to go chasing it down.

correct me if im misstaken? u put this turbo on...then send 20+ psi through it??? OR does the tuner gradually raise up the boost pressure when they tune for it???

whats the boost reading when the e-boost is switched off???? wouldn't this tell u exactly wether the spring is worn or not rather then going off ur last turbo????

how can u justify thats its a 16psi spring when tryng to send 20+ psi through it???

can u give more info into this matter?

[B-Man]

I'm not trying to justify anything - The wasegate was bought pre-loved and we didn't know what sort of spring was in it.

With the 3040 minumum boost (ie e-boost turned off) was 18 PSI same as the the 2835 (18 PSI) but as you can see from the graphs, boost goes down to 16 PSI as revs increase. I'd prefer for it to stay at 18 or 20 PSI that's what I am sayaing.

All I am stating is the facts - and looking for answers.

[nv033]

all i wanted to know is does it behave in the same manner if u lower the boost (that is when eboost is switched of does it go up to 18psi then dropp to 16psi as well?....from the graph u posted it was initailly 20psi then drops to 16psi......if it is compressor limited generally where the boost drops off too ive noticed it to be most efficent...eg Buster's car... most efficient was 19psi....we squeezed 20+psi...it made a diff of 10kw max and with big spikes in the lower end, likewise with my car...what boost the turbo is rated to be efficient at is not always the case cause if ur making the power ur suppose to on it there no point screwing up the boost.......we were in the same boat as u now...

its not a $$$ for HP gain

it is when ur gonna send more boost through the turbo and eventually blow it

and having to buy a new turbo it will be a $$$ vs HP gain

Anywayz at 17-18psi im pretty confident that 2835 uve got will push out 275-285rwkw).....y bother squeezing anymore boost into it , isnt that the ultimate...low boost, big HP, less strain on ur motor, longer life if u want an answer i think thats it

otherwise get a bigger turbo...but as u go bigger Lag is the enemy as u should know with the 30/40.....how doe sthis turbo compare???

[DoughBoy]

Hey why not screw the wastegate in a bit and try it without the EBC connected, just running one line from the plenum to the bottom fitting on the gate. That way you can eliminated the wastegate from creeping open due to the EBC.. or see if it's the wastegate at fault.

Those Trust R gates are rebuildable, can always open it up to see if the diagphram is torn or catching on the side.

It's a fallacy that HKS turbos only start to make power at 18psi. If that were the case all their compressor lineup would have massive exducer diameters, and would be pretty laggy due to the increased inertia.

Having that massive spike on your "ideal" graph would just smoke the tyres. I bet it would be faster + more driveable without the EBC spiking the boost at lower RPMS, although at higher road speeds you might want that mid range spike.

If you really are after a combination that gives boost early, yet delivers more power up top your best bet is a set of small twins, like GT-SS or 2530. Merli's ~320awkw on GT-SS's would fit your criterea perfectly.

[2rismo]

Where was the boost reading taken from for the dyno input? Inlet manifold?

Adrian

[Freebaggin]

If you really are after a combination that gives boost early, yet delivers more power up top your best bet is a set of small twins, like GT-SS or 2530. Merli's ~320awkw on GT-SS's would fit your criterea perfectly.

Turn it up BoughBoy, as if he's gonna stuff around with setting up twins. Show us Merli's dyno to prove that his mid range is good.

[B-Man]

Where was the boost reading taken from for the dyno input? Inlet manifold?

Adrian

Yes that's right

Umm but before the intercooler

On the pipe from the turbo to the cooler !

I think - well that is where the E-boost is plumbed in

I'll check where they tapped in the Dyno boost input

[grepin]

Grepin - dude, can you post your graph ? I wouldn't mind seeing the difference between internally gated and externally gated 2835s

 

No worries here it is..

[Cubes]

Thats a nice linear power curve grepin.

Coincidence, both 287rwkw.. lol

[B-Man]

Yeah - nice smooth curve - unlike mine which is a bit all over the place.

Oh BTW - DB Don't forget that I have a big FO bar and plate intercooler to ensure that the so called 'hot air' is sufficiently cooled before it goes in the engine

Not taking ANYTHING away from Grepin - But I would have thought that a Externally wastegated, top mount 2835 would have performed a little bit better then a an internally gated low mount.

Thanks for posting Grepin - you have damn good power and nice curve.

Don't get me wrong - my car is still damn fast - It scares me more than the 3040 - cause on the street it is soo much more zippy.

Cheers fellas