Cant get boost above 15psi and the turbos pitch doesn't change much once 15psi is hit. I've had it hit 15psi at 3500 and stay through 5000rpm. EBC is turned up to 100%, got the biggest spring in the waste gate, t-bolt clamps all around...... turbo was a custom unit built with a goal of 900hp. Looks like its tapped out at around 600hp @ 4500rpms. could probably get up to 750hp at 6000rpms but I dont want to sent the turbo into orbit

Motor and setup specs in boosted roll call but for short :383cu fully built 8.4:1 comp, trickflow heads. dual walbro -6an feed 60lb motrons blah blah.

I am trying to figure out a guesstimate on the power its making. at 15psi boost the fuel pressure to the 60lb motrons is 60psi. At 4500 rpms they are seeing 60% duty cycle. Given the formula: injector size x duty cycle / bsfc x 8 = hp (i know its used to pick a size of injector) adjusting injector flow rate to fuel pressure puts them at 80lb/hr @60psi thus 80 x 60% / .65 x 8 = 590hp. Granted at that rpm my AFR is 13.0:1 ! Is my math correct? I'm just trying to get a ballpark number here.

I'm going to have to go back to the turbo shop and get something bigger I just wanted to let them know just how much I could squeeze out out this unit so they can get me what I need to get more power.



Here are pictures of scans with datamaster and and logworks log. I'm working on the leaning out above 4000rpms. going to go 2bar soon hopefully.
http://content.glidesociety.com/imag...5-ba4e0c5b6f84

http://content.glidesociety.com/imag...b-622a9e5e7cf2

What size turbo is it? Maxing out at 3500 seems soon. Is it a T70? Also is it T4 flanged?

Any pics of your setup?

Also i believe that 60#s are good for around 700RWHP on a boosted car and about 900 on a N/A car.

By using a online calculator i got around 750HP is 58#injector at 80% DC

Jay

maxing out around 4500....

T-76 t4 flange .96 a/r exh. 4" exhaust out the back. I'll have to dig up pics after work.

For one thing i think the T4 flange is killin ya. Everyone told me go T6 on my 383...I did and what a pain to do the hotside! lol

Are you still on a 1 bar map and just using the PE to control the fuel after the maf maxes?

Or is this a SD car?

Jay

Hmm, I can't look at the logs at work, but a 76 even with a t4 flange I wouldn't think would be quite out of steam... little different motor but my t70 is making that, and its a lot smaller.

Don't know how much more you will get out of the 60#s either... I know I'm running them about 90% on 60psi.

I do know someone who needs a t4 t76

I'm a little confused.


Have you dynoed the setup? Why do you think you need something more than a T76? Because you haven't seen more than 15psi at 4500?

I'm sure I'm missing something.

-Scott.

Its a 1bar with maf tune right now. I can max the maf out at 3500rpms! still trying to get the AFR in the 12's above 4000rpms. I would think the T4 could handle more than this....

Though 15psi is only a measure of resistance to airflow on any given motor.

The 15psi I see could be 25psi on someone elses motor....

I have not had a chance to dyno yet. Still working on getting fuel in higher RPMS that and a dyno is 100+ miles from me .

Maybe not something more than a t76... maybe a better one or something bigger. The reason I think its out of steam is that with the EBC set to 24% through 100% 15psi is the max I can get. the EBC set to 20% = 13psi, 18% = 12psi etc etc. I've even disable the EBC and tossed in the strongest wastegate spring I could get in the wastegate, cranked down on the adjustment nut and 15psi is all I could get. I guess I could block off the wastegate all together and see if I could get some more out of it but that would probably just break something.

Also, and this is hard to explain, but the whine that the turbo make just seems to hit a note and stay there. Even as rpms (and the air the motor consumes) increase the whine stays the same.


Jsetzer,

How much power are you making with the 60's at 90%? I have been keeping my on the 79# high Z's that I will probably need eventually.

I'm hoping that I can have this turbo upgraded. The center section is ceramic ball bearing so maybe just better and/or bigger wheels on either side.



As for pictures of my setup, here are a couple with a few shots of the motor.

http://content.glidesociety.com/imag...f-65808bc3566d
http://content.glidesociety.com/imag...8-cdada6207c27
http://content.glidesociety.com/imag...b-e7656daf4f2d
http://content.glidesociety.com/imag...6-12d380e874d6
http://content.glidesociety.com/imag...7-1bb058139b86

The T4 T76 is not max'd out. It will make 20+ psi on a 383. I once had an overboost incident where I blew both headgaskets so bad that the motor hydraulic-locked, and that was with ARP bolts, Fel-pro gaskets, and AFR heads. That turbo will support over 950 hp on a 383.

Just because your electrobox can't seem to get it there doesn't mean the turbo is max'd out. I generally don't like electronic boost controllers because people for the most part don't understand how they work and get into situations like yours.

Why not fab up a block-off plate where the wastegate goes. Have a couple of head gaskets on hand if you try to do this.

If the turbo was really maxed out, then you should be loosing boost in the upper RPM. Turbos max out when their #/min of air can't be maintained. And when that happens the back pressure(boost) created by the engine will go down.

It seems more likely that you may be hitting some kind of backpressure limit and getting the wastegate to open early. Do you have one of those boost conrtollers that actually holds the gate shut until you want to open it? If not then you can try an experiment, put the boost line to the top of the wastegate to hold it closed and then head out to the highway and watch the boost. Your engine should be able to handle 20psi at 3500 rpm if you do the fueling correctly. Just watch the boost when you get on it and if it goes over the 15psi amount then you know you need something else to hold the wastegate closed.

Also check for leaks in your pre-turbo parts. I've had leaks before and it will limit your boost to a set amount until you get it fixed(even with a wastegate block off plate installed).

I don't know what my power level is for sure - I did 560 to the tire on a dyno day but only got 3 pulls and only turned the **** up once. I'm running more boost now then I was but I know realistically what this little turbo is capable of. I would say 625-650 is the absolute max I can get out of my fuel or turbo right now.

I guess its a good thing it all runs out of mustard about the same point.

I've got an O-ringed copper head gasket setup.... would probably blow a piston before the head gasket

Well, after trying my best to get more out of it I am still hitting this wall. This is with the EBC and with the wastegate only. I think I have some substandard parts in this turbo somewhere. Probably P-trim exh wheel? After searching forums for a while it seems that a Ptrim t-76 craps out right around 700hp which also seems to be what similar motors to mine are hitting at this boost level...

My latest log file shows peak boost at 4350rpm @ 15.48psi. Drops to 14.9psi at 4700rpms under full throttle and you can see the drop increase as rpms rise. So boost is dropping with RPM increase. I cant get above 5000rpms because I'm having trouble getting the PCM to add fuel up there but there isn't much point going above 5000rpms if the turbo is running out of breath. I wish I was closer to a dyno so I find out how much power this turbo is putting out.

MN_vette,

I couldn't find any exhaust leaks with it idling.... kinda hard to test under full throttle though so that is still a possibility. MY EBC is a greddy profec. I have not tried the boost line like you suggested though I have tried the biggest spring & max adjustment on the wastegate with the EBC disconnected (which is a turbonetics racegate btw) with no change in results

The EGT never goes above 950F even at 13:1AFR @ 15psi @ 4500rpms and the intake temp at 15psi is only 15 degrees higher than outside temp. I'm no expert but wouldn't that give a hint that the backpressure is nominal and the turbo should have some life left? My post turbo exhaust (partially seen in a picture posted above) is 4" with a dynomax bullet that dumps before the axle... thats about as free flow as you can get....

The turbo is easy enough to remove and the turbo shop is only 15miles away so I'm yanking the turbo to find out if theres something up with it.

Picture of the log works file from my last run:

http://content.glidesociety.com/imag...a-7f957d65bccc

There is an easier way of testing for leaks in a system. You need to go to home depot/lowes and pick up a sewer pipe connector that will fit over your turbo downpipe attachment. Then get a matching PVC cap that will seal the other side of the sewer pipe connector. Drill and tap an air hose fitting into this cap. When you seal it to the downpipe side of your turbo and hook it up to your air compressor you should be able to see where the air is leaking out.

The air should seal everywhere. You may get some air leaks around the piston rings but you can ignore that. If for some reason you stopped the engine at a point where both the intake and exhaust valves are open then you may need to rotate the engine a bit to get them to seal. A little soapy water on some of the joints will help you see exactly where the air is comming out.

You can also do this with the intake side of your setup to check for leaks there too.

Just got back from the turbo shop. The exhaust wheel is a P trim. Upgrade to F1 wheel and rebuild cost is too much $$ so I will probably stick this turbo on the GTO and get a better one for the firebird