DCRB

here's the deal, i just installed a 16g that i put together on my hatch. it consists of a small 16g center section and turbine wheel, evo3 compressor wheel and cover, and an ebay 7cm turbine housing (has 0.70 ar stamped on the outside). spool is decent, a lot smoother yet slightly slower response than the 14b i had on there.

i noticed that when i get on it the wastegate opens and closes rapidly as rpms rise. car doesn't pulse and according to my gauge boost doesn't fluctuate (using an old school mechanical vdo gauge from a turbo saab).

I have already checked to make sure the gate arm isn't hitting anything or binding up, and it is slightly preloaded. I am using a ball and spring boost controller, which was not changed or adjusted at all when i swapped turbo's. My wg boost source comes from about 3"s off the turbo from the factory DSM "J" pipe, and my boost gauge gets it's reading from a nipple on the back of the intake manifold. I'm using the same waste gate actuator that i was on my 14b as well

anything else i should check? i haven't been able to get on it too much as the 16g moves enough air that i'm hitting 12.0:1 afr, plus it's been really wet out lately. getting a re tune next week but want everything sorted out first.

Thanks in advance for any suggestions or advice

p.s. this set up is on a d16a6/z6 combo with a d15b cam, skunk2 intake manifold, dsm 450's, tuned on crome gold, with a civic std exhaust manifold with an adapter plate to the dsm flange. currently has a 2.5" intake, 2.5" turbo back and a 2" external dump tube. plugs are new and gaped to 0.026", bkr7e's. cap and rotor are new, wires and filter are newer, and i'm running 92 octane from chevron, if it all matters... Thanks again!

Muckman

iTrader: (2)

So let me make sure I got this right - Got new turbo, boosts fine but wastegate SOUNDS like its cycling rapidly but there are no adverse affects?

It sounds fine to me if there is no boost fluctuation. Of course you are only using a boost gauge and not logging MAP. MAP would show a small fluctuation if there was any.

I would say try it without the MBC and see if it it does the same. Otherwise I wouldn't worry about it too much. The wastegate is probably more audible now because its bypassing more exhaust to keep the larger turbo at the same boost pressure. Get your AFRs cleaned up and enjoy.

SPOOLINmatt

sounds like typical boost controller issue to me

TheShodan

iTrader: (14)

I'm with Muck on this. Sounds rather normal.




@Wantboost, considering the size of the actuator for the 14b for its amount of air flow, you're right, this could be a possibility.

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wantboost

iTrader: (2)

it could simply be a matter of the wastegate having to move rapidly to control boost...

Schister66

I think this is a symptom of running a tiny internal wastegate. My STi has this same issue around 19-20psi...the gate starts to flutter and you can actually hear it inside the car, but if you watch the boost gauge, nothing happens...it stays stable (apart from the boost taper in the upper RPMs)

wantboost

iTrader: (2)

yea the problem is the small flapper causes the wastegate actuator to open rapidly to level off boost pressure then it shuts rapidly to keep it from dropping. it does this so fast you won't see a change in boost pressure but you will hear the wastegate hard at work

same thing happened with our automatic diesel trucks. under boost, when the trans shifts, the wastegate would flutter a bit every time it changed gears as the rpm/airflow demand of the motor rapidly changed. it was especially noticeable at full boost and even more so after we tuned it (added more fuel) and raised the boost pressure

external wastegates do this every so often and you'll hear a chatter coming out of the dumptube (open dump)

It's perfectly normal. now if the chatter continues and the boost fluctuates then you might have an issue

you said you built this turbo yourself.... did you balance the cartridge after assembly? I would check the turbo for shaft play as sometimes wastegate chatter can be confused with the compressor wheel (or turbine wheel but it is normally the compressor.side due to the high thrust loads) very rapidly and lightly hitting the housing.

DCRB

thanks for the responses! so far no i have not had it balanced, the reason behind that is mhi turbos are component balanced from the factory, and the only non mhi part on the turbo is the turbine housing. the compressor wheel and cover i bought from a guy that upgraded his e316g to a 20g compressor wheel. none the less i am going to keep an eye out for shaft play, and if it develops i will repair and send it out.

i will try running to mbc to see if that changes anything, i'm only tuned for 9lbs and the wastegate has a 7lb spring in it, if that makes a difference

wantboost

iTrader: (2)

I know that MHI stuff (the genuine parts) are component balanced to 0 or as close as they can get it but when swapping wheels and such the components as a whole can be out of balance

DCRB

ok i have an update. i was finally able to get a brake from the rain and get a few pulls in, looks like my boost level does drop when the wastegate opens. it's almost like the wastegate is bypassing too much exhaust from the turbo? it does start to stable out at higher revs, and doesn't fluctuate as much if i step on it from a low rpm in say 4th or 5th.

Here's a video, sorry it's crappy but i was by myself