Rick 12v CTD

I've never had this before but I just rebuilt the motor and did some things to it (see sig)

Now the truck runs good, except that the injectors don't like a lot of timing (wrong spray angle, when money allows I'll be buying the more expensive bosch 7 hole nozzles with 148* spray angle)

Now, for the problems I am seeing:

1) above 20 psi of boost my gauge likes to start to bounce around. The more boost, the more it bounces. What causes that? I've never had a boost gauge do that before.

2) Also, I can get the turbo to hit 20ish psi by 1500rpm but the turbo starts to bark itself and won't build any more boost until it's closer to 1800rpm. That makes no sense to me at all. I'd think it would just surge if it was pushing too much air, which it's never done. I can understand the not building boost if it doesn't wanna spool, I get that because it used to just build a certain boost for that given rpm (when the rpm was lower) before and it'd just smoke and not spool. I get that, but now it does somethign similar, but it also barks and makes a whoooshing sound under throttle and load at these lower rpms. It's almost like it wants to spool hard at 1500 and just stops building boost and starts to bark instead. And all this is under load, where the rpm doesn't suddenly drop off.

I had this turbo on my motor prior and didn't have either of these issues. And I'm at a total loss for why either are occuring


As an aside, my max boost with the valet closed is somewhere between 35-40psi with a light haze. With the valet open it's like 50ish psi and very smokey. Valet closed it's actually quite a clean burning machine and has lots of power and runs really cool. Great for towing and work. It's nice for daily driving too, unless I floor it I might only see a light puff of smoke, if at all. When I floor it, the smoke isn't too bad at all if the valet is closed. Less smoke with this setup and the valet closed than before with the he351 and old DDP4 injectors (stock fuel screw) except that this setup does haze more at idle. It looks like my afc mods have paid off Then I just turn my ball valve for my afc and BAM! it's a toy/play truck with tons of power (and tons of smoke lol)

I think the truck would do exceedingly well with the bosch 7 hole nozzles with 148* spray angle, and a 64mm turbo or something like the 3788r garrett.

Any suggestions or comments on the 2 problems/questions I have though would be a big big help.

dieselJon

Is the cam timed correctly?

What are your EGT's?

Rick 12v CTD

egts are 1300 at the tail end of a WOT run with the valet open. Full fuel. 50+psi.
egts are good.

And the cam was just put on the gear where the keyway slides on to it, that can only go on one way.

Apart from that, yes when I reinstalled the cam in the block I lined up with the proper tooth on the crank gear.

I did not get a dial indicator out and time it perfectly to 98* centreline like hamilton cams suggests. I just got the shop to pull the gear off the old cam, and install it on the new cam. then I reassembled the motor and timed everything accordingly.

dieselJon

What has changed other than the rebuild? Just the cam or injectors too? What about the IP?

If the injectors were changed also, then do a test of cracking an injector open listening for changes in the engine.

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Rick 12v CTD

I can try that. unfortunately when I rebuilt it, I changed just about everything else attached to the motor.

New IP, used my old stock injector bodies and had these 7x14 tips put on and reset the pop pressures to stock 245 bar. Used a second gen lift pump with regulator and 3/8" hoses along with the fuel filter off the same second gen motor. even the vac/steering pump is off the second gen motor. And yup, changed the cam too.

If I crack the injectors one at a time and it changes at all, what does that indicate?

I also noticed #1 return was leaking, and so is the return of the regulator. I'll get those buttoned up.

valve lash is set at .010" intake and .018" exhaust currently.

I've never even heard anyone ever have the problem I have with a barking turbo under load at a constant or rising rpm.

dB Zac

if you go to Hamilton's website, he has a vary in depth write up on the importance of cam indexing and he says that even from the factory, the cam/gear relationship can be different from engine to engine

Rick 12v CTD

I have indeed read it. I just honestly don't know how to do it, which is the main reason why I didn't do it. I even read that hamilton cams sells offset keys to index the cam properly.

Maybe I should give hamilton cams a call and see if they can help me. If I can sort this out and if this turbo will light properly at 1500rpm like it seems like it wants to, I'm going bigger, because considering my WOT black cloud with the valet open, I could use more air.

I'm kinda hoping someone will come out of the woodwork and say they had a similar problem and point me in the right direction, and say "oh it's the injectors" or it's the cams centreline" or something, ya know.

JQmile

My bet is that the turbo is surging. It's basically lighting too quickly, before the engine is ready to accept the amount of air it is trying to produce. Once it starts to surge, it will never really recover, unless you lift off the throttle and roll back into it.

dieselJon

When you crack the injectors, you are waiting to hear an engine note change. If it doesn't change when you crack the injectors, then that injector/cylinder has a problem.

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dB Zac

at a peak boost of 20 lbs?
My guess is timing or flat lobe. Its not breathing the way it should.

I would call Hamilton, they say deg the cam is vital

Rick 12v CTD

I'm wondering if it has anything to do with the injectors. I've heard that sometimes the different spray angle can just make weird, lousy running issues. and will make problems for lighting the turbo. idk...

I'd be surprised if it was surging, but I suppose it's possible. this turbo never did surge before the cam and turbo/manifold blankets, idk why it would after. And it's just your run of the mill s362/65. and yeah, it seems weird that it would surge at 20psi.

I'll crack each injector line tomorrow and see what happens with that. It's dark now and I don't feel like messing around in the cold and dark.

Thanks for the input so far though guys.

92smokin blacky

mine will flutter if I keep my turbo at anything over 25 lbs of boost. If I put it to the floor and give it everything its got up to 50 and don't back out then it doesn't do it. I'm not exactly sure why it does this. I thought I heard once a possible boost leak but have never really looked into it cuz it still runs awesome and hasn't given me problems

1992gen1_fan

Is there excessive play in the turbo? Also is it possible the tturbo could be out of balance or something?

Rick 12v CTD

I think it might be the turbo. I don't see how it would be out of balance though, since I didn't do anything to it.

I'll be pulling the intake off today and having a look at the play in the wheel.

jimbo486

What size turbine housing on the s300?