So I've been building my hybrid turbo, removing emissions installing ecu, etc. It's been a long process but I finally got it all put back together. I got it all running but the turbo won't spool past 4 psi. I'm thinking it could be one of three things. First, I scarred the dynamic bearing, second the afrs go into the 9's as I installed bigger injectors but I haven't tuned it yet, third is that the compressor wheel originally went on a bigger shaft so it fits secure but not as tight as the stock compressor on the shaft. Would any of these give me the problem I'm having? If not then is there anything else that would?

 

the compressor wheel originally went on a bigger shaft so it fits secure but not as tight as the stock compressor on the shaft.

 

the compressor wheel originally went on a bigger shaft so it fits secure but not as tight as the stock compressor on the shaft.

 

the compressor wheel originally went on a bigger shaft so it fits secure but not as tight as the stock compressor on the shaft.

 

You're all wrong. It was that the compressor wheel originally went on a bigger shaft

 

excellent logical deduction sir

 

wat

 

Mixtures in the 9s will stop it from boosting.

 

boost or exhaust leak

 

I'm seeing things

 

Yeah but my experience is more because it will hardly run at WOT this rich. This is probably as low as the sensor will display so who know what the A/F really is. If it revs clean at WOT at this A/F boost will not be limited to this extent. If there is major break up and the car falls on it face trying to rev then maybe.

 

I'm still working out a lot of kinks, but I do believe it was afr's. I've got them into the low 11's now and it will spool to 6.5 psi which is where the wastegate opens...at least until I turn up the boost controller. On the same subject, what should my target afr's be under boost? I'm aiming for the high 11's

 

How would an exhaust leak stop it from boosting? Unless it was before the turbo, wouldn't that just create less back-pressure and wouldn't that in turn help the turbo to spool faster?

 

An exhaust leak post turbo wont stop it from spooling that's for sure.

 

Heat drives the turbo, the pressure difference. You want to run in the cruise cells leaner mixtures and hotter. Then you slowly richen the AFR as you build boost and that hot mixture wants to detonate. Max power and torque are in the 12.5 AFR region, but you will probably need to richen it up more if you plan on boosting higher PSI.

my rule of thumb is cruise cells for purely cruising is 14.7-15.3 AFR (only a small amount of low load cells will be at this AFR), the cells around this are 14.0, I richen to 13.0 AFR smoothly at 0PSI, then I ramp it slowly to low 11's to 15-17PSI (at elevation, 14-15 sea level). I run 10's above that and dump fuel to control a runaway boost problem.

Have slight retarded timing to help with spool in the spool region of the map, tune AFR's at steady state and if it leans a little on throttle acceleration its good for spool with a slightly leaner/hotter mixture.


Make sure to have a low pressure drop (as big as you can fit) air filter. Helps with spool.

 

Okay, damn. I thought I had everything worked out. Now when my turbo spools it has a light whine to it. It sounds like a low pitched whistle. Maybe like a dremel. It's not very loud either. It's about as loud as the regular turbo spool.

 

Anyone?

 

the compressor wheel originally went on a bigger shaft so it fits secure but not as tight as the stock compressor on the shaft.

 

but it spools. How would it spool if the shaft was spinning in the compressor wheel?

 

It can slip and still spin or it can start slipping when more force is put on it or a combination of both.

For a quick check take the turbo inlet duct off and put a mark of toe nail polish/whiteout across the compressor wheel and onto the compressor nut.

Go drive it hard and re-check that the paint lines still match up.

It is not an unknown phenomenon to have the compressor wheel slip on the shaft and that is on turbo parts that are supposed to be assembled together.

 

How would I fix this problem?... Do I have to get an entire new compressor wheel or is there some alternative? It is a fairly tight fit after all.

 

Tight like you need to warm it with a propane torch to slip it on?

 

no, I mean that it isn't loose on the shaft. It slides on and off easily but it's not like the compressor wheel can move laterally on the shaft like side to side or anything

 

well it's not the compressor wheel. I marked the wheel and the shaft, drove it hard, and when I got done the marks were still lined up. It still howls though. It's like a distant police siren. Could it be an exhaust leak maybe?

 

Good news on the compressor wheel anyways.

I haven't had an exhaust leak sound like anything other than a helicopter on my car.

I have toasted bearings in turbos and it whined really well.

I have heard a damaged exhaust wheel or compressor wheel can do the same.

You probably checked the side to side shaft play when you checked your compressor paint marks though and it must have checked out.

Oh, I have had boost leaks make a compressor whine pretty good- did you do a boost leak check yet?