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Street Build ~600whp Steet/Strip Auto 1g

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Street9s

Proven Member
64
15
Apr 26, 2017
Pasco, Washington
Greetings from Eastern WA. Recently purchased my first DSM. I've known about the potential of these cars for a while now and finally got my hands on an early '92 with the 6/4 bolt combo.


DSM lookin good.jpg






I bought it with a lot of mods done to it by Boostdriven. Scalia pistons, scatt rods on the bottom end with 8.5 CR, and a Supertech combo in the head, Early BC 272 cams with some PNP work done to it. Turbo was an HX-40 with the BEP .55 housing. It also came with ECM link already on speed density. I've recently installed some FIC 2150cc injectors to allow the fuel system to flow more. Pump setup is two Walboro 255s in tank. I'm pretty excited for this build.

DSM dyno 407.jpg




The car dynoed 407 AWHP @ 25psi and 14* of timing with two 225cc meth nozzles. A figure that I was somewhat satisfied with. As I attempted to up the boost I ran into some issues which appeared to be excessive crankcase pressure. As soon as I got home I performed a boost leak test and discovered it was a injector seal leaking.
My goals are to have a car capable of 9's on the strip, and still be streetable.


DSM e85.jpg





Just yesterday I was doing datalogs and starting to push the motor a bit. E85 recently went in the tank and I was making around 36psi @ 19* of timing up top. Personally, like to take two logs for consistency. On the second 3rd gear pull I experienced something similar to a coupler popping off. Turned out to be the turbo.





DSM Turbo rekt.jpg




I believe the cause of this was too much backpressure from the small BEP housing. I've already ordered another HX-40 with upgraded bits which is supposedly capable of around 90 lb/min. I'll be hitting the dyno once the street tune is done to see what it can make.


Ideas and criticism are always welcome. If it can make me more power or you have something I need to be learned on, please let me know.
 
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I am not sure its back pressure as excessive back pressure is due to the housing being to small to flow more than XX amount of gas for a given pressure. If you keep raising the pressure the flow does not increase proportionally to the pressure as it normally does and cause the pressure to raise even more as you are actually choking the flow of the exhaust. Since it's to small to flow through it will cause the pressure to raise before the housing exit which is right where the tips of the turbine are. That choked flow causes the turbines rate of acceleration to slow down or rather not speed up proportionally to RPM

This turbine map from Garrett illustrates that....if you keep raising the pressure it does not increase flow after a certain point:

asdfasdfnsg.jpg


To me this looks like a bearing failure or a worn out bearing that wore down enough to allow the tips of the turbine to hit the housing wall as the turbine blades are bent back.

Hard to say from a pic tho so its just a thought.
 
It could very well be. I was told the turbo had around 20k miles on it, I just find it weird that a diesel turbo would fail so soon like that. Not so bad though, hoping the new turbo flows a lot better up top and I won't have to push it so hard to make good power.
 
It could very well be. I was told the turbo had around 20k miles on it, I just find it weird that a diesel turbo would fail so soon like that. Not so bad though, hoping the new turbo flows a lot better up top and I won't have to push it so hard to make good power.

Hate to be that guy, but people are sketchy sometimes or just throw a number out there without knowing.

Ive been burned a few times on stuff like that. Check my build log and jump to page 6 where i install my brakes i bought a member here...what a fcuking gong show.

People lie lie lie especially when $$ is involved.
 
You're absolutely right. Honestly I was planning on upgrading anyway. I'm going to rebuild this one to have a spare as well. I trust this guy a lot, really knows his stuff. I'm just glad it wasn't a 2000$ turbo and I had the money to just up and buy another.
 
HX40 isn't going to flow 90lbs/min. Hate to give you the news. Is it a GENUINE Holset (is there a Holset tag on it) or was it a Chinese knockoff of one. You had ONE exducer blade break and it ate up the rest of the exducer. When I used to break HX-40's on a .55 housing, I was shearing off the exducer, three times. Finally went to a .70 T3 housing and it likes it much better.
 
Yes it is genuine, and the one coming soon is also genuine. New one will have the 67mm compressor wheel, and the 12 blade turbine on a .82 housing. Talking with a turbo builder, he said that it is 90lb/min capable. At what boost I do not know. Either way it's relatively cheap and it's going to flow a LOT better than the stock with the .55. One blade breaking and going flying through the turbo when it's at ~110k rpm and causing that damage does not surprise me. I was thinking that was normal. is it not?
 
Yes it is genuine, and the one coming soon is also genuine. New one will have the 67mm compressor wheel, and the 12 blade turbine on a .82 housing. Talking with a turbo builder, he said that it is 90lb/min capable. At what boost I do not know. Either way it's relatively cheap and it's going to flow a LOT better than the stock with the .55. One blade breaking and going flying through the turbo when it's at ~110k rpm and causing that damage does not surprise me. I was thinking that was normal. is it not?


Take the old one apart. You wont really know what happened until you look inside....or at least get a better idea of what happened.


HX40 isn't going to flow 90lbs/min. Hate to give you the news. Is it a GENUINE Holset (is there a Holset tag on it) or was it a Chinese knockoff of one. You had ONE exducer blade break and it ate up the rest of the exducer. When I used to break HX-40's on a .55 housing, I was shearing off the exducer, three times. Finally went to a .70 T3 housing and it likes it much better.

So maybe it was to much back pressure? If it was maybe it was EGT's that killed it then? EGT's do shoot way up when the PR gets to high.
 
Yes I have a feeling the excessive heat and back pressure did it all. I have a "showcase" piece at home that has a perfect inducer and a bent shaft and bits of an exducer left to look at and remind me.
I haven't had problems on the bigger housing.....cross fingers!!!!
When you get over 70lbs/min on the Holset, show us the figures. That will be a feat.
 
I did take it apart, but couldn't get to the journals for lack of snap ring pliers. But the shaft was bent, had heat marks, and there was a good bit of oil residue in there.
When you get over 70lbs/min on the Holset, show us the figures. That will be a feat.
We'll see what happens, and I'll be sure to post logs!
 
Pretty sure turbolab stuffs a 67mm into the hx40
 
Nice car. I run an auto with the turbolab 67mm Holset setup at 42psi. Very streetable and good power band . Need to run a log to see the flow output but it's way up there. The car easily has mid of not low 9 power. If only headgaskets would cooperate.
 
I am not sure its back pressure as excessive back pressure is due to the housing being to small to flow more than XX amount of gas for a given pressure. If you keep raising the pressure the flow does not increase proportionally to the pressure as it normally does and cause the pressure to raise even more as you are actually choking the flow of the exhaust. Since it's to small to flow through it will cause the pressure to raise before the housing exit which is right where the tips of the turbine are. That choked flow causes the turbines rate of acceleration to slow down or rather not speed up proportionally to RPM

This turbine map from Garrett illustrates that....if you keep raising the pressure it does not increase flow after a certain point:

View attachment 332434

Don't want to be a dick, but no. That chart is CORRECTED gas flow. I'd suggest looking at how corrected gas flow is calculated to get an idea. Yes, the gas flow is choked at pr > 2.0, but all that is indicating is that the flow has hit sonic velocity, and cannot increase. However, the mas flow can still increase due to increases in upstream density. Almost all turbo chargers operate with the nozzle choked.

It's likely that this turbine failed due to it being a cheapie china part. You really have to push it hard to do that to a genuine holset turbine.
 
Don't want to be a dick, but no. That chart is CORRECTED gas flow. I'd suggest looking at how corrected gas flow is calculated to get an idea. Yes, the gas flow is choked at pr > 2.0, but all that is indicating is that the flow has hit sonic velocity, and cannot increase. However, the mas flow can still increase due to increases in upstream density. Almost all turbo chargers operate with the nozzle choked.

It's likely that this turbine failed due to it being a cheapie china part. You really have to push it hard to do that to a genuine holset turbine.

Good point. :)

I was trying to show that it likely wasn't excessive back pressure as that will just decrease the rate of acceleration of the turbo as the PR can still keep going up but the exhaust mass flow rate slows down (due to it hitting sonic flow as you stated). My point was excessive back pressure hurts performance and wouldn't do that to the blades of the turbine. Plus its a Holset as you stated and they are supposedly tough as nails.

My money is on blown journal bearing as I have a T25 that looks just like this but its just speculation until we get more pics.
 
No the mass flow does not slow down, the mass flow increases with the upstream pressure. Choke flow is grossly understood by most people. There is really no limit to what you can 'blow' through an orifice, but there is a finite limit to what you can suck though an orifice. It's really the high temperatures, along with shock waves that are created by the sonic condition that causes the issue.
 
No the mass flow does not slow down, the mass flow increases with the upstream pressure. Choke flow is grossly understood by most people. There is really no limit to what you can 'blow' through an orifice, but there is a finite limit to what you can suck though an orifice. It's really the high temperatures, along with shock waves that are created by the sonic condition that causes the issue.

Not what I meant to say...actually I did right that wrong. Should be "the rate at which the mass flow rate is increasing slows down"....shiit that sounds funny too. Ummm....the slope of the mass flow rate to relative to PR decreases?

What I am trying to say is the mass flow rate is still increasing but the rate at which it is increasing slows down. I think were saying the same thing I'm just butchering the wording. :)
 
It's likely that this turbine failed due to it being a cheapie china part. You really have to push it hard to do that to a genuine holset turbine.

The turbo had a lot of miles. I'm pretty sure that the housing couldn't support the airflow. That's a lot of velocity for the turbine, and I believe it caused it to come into contact with the housing. I'll never know for sure. Probably due to the turbo being tired for the most part.
 
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