is my compressor too small?

NMB2

NMB2

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Mar 1, 2012
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Ok, now that I have gathered a bit more information on my setup/conditions and have a decent amount of miles on this engine (5,000) I feel its time to tie up the "loose ends". I have currently been focused on body work/interior and the truck isn't in my possession for the next 2 weeks so I figure this is a good time to figure some engine technical things out.

Engine:
6.9 International IDI diesel (7liter actual displacement)

Custom turbo setup, cam, fuel system... everything. I have taken this engine into a completely gray area, there is no other engine to compare my results issues to.

I thought when building it I had a good enough idea on turbo maps, and some of the diesel sites I posted on said everything looked good, but I'm almost convinced at this point my turbocharger is too small. I wanted to wait to get back pressure readings and as much info as I could before presenting it here.

the turbocharger is a BWS300 - 62/74/14 T-3 twin scroll. Stock cast 7blade ETT and "tractor" cover.

My "issue" is that it will not clean up smoke under WOT. WOT on fuel only I see 30psi boost, and it smokes like a freight train. If I meter it with the right foot, 25psi is the "breaking point" @ 25psi I have no smoke.... 25psi is roughly just over 1/2 throttle. Mash it and it jumps up to 30 and smokes like a freight train. User water/methanol injection I can get 35psi with a 40% mix.

At 30psi boost, I have about 37-38psi back pressure, @ 35psi boost the back pressure spikes up, but I never hold into it long enough to see it go over 45psi, although it jumps up quick enough that it gets there fast.

As for fuel levels.... I have a 150cc injection pump. Only other comparison I have is a buddies built up IDI which is 7.3 liter, he has same injectors, and same turbo with a 90cc injection pump. He see's 20psi boost and its completely clean. His engine is 21.1:1 CR, mine is roughly 18.5:1

Here is a video to show the amount of smoke I see under WOT, 30-35psi:

20psi boosted launch
[ame="http://www.youtube.com/watch?v=kA9bTciAt_M&hd=1"]http://www.youtube.com/watch?v=kA9bTciAt_M&hd=1[/ame]

I used these two links to try and "map" my compressor a few months back when choosing turbos:

Compressor map reading for dummies. - HondaSwap Forums

Compressor Flow Map Calculator

Using those two links I came up with these:

This map is for 30psi... green line is 3000rpm, yellow is 3200rpm.
s362mapped2.jpg


This map is 35psi, colors are the same.
S362mapped.jpg


I was put under the understanding that the 30psi map was perfect, and the 35 was "OK". Did I do something wrong? Have I been taught wrong? It would seem to me that my compressor is much too small for what I'm doing. I am considering upgrading to the Bullseye Billet 6blade race wheel, but am worried that that $450 will be wasted if its still not large enough.

one other thing that just crossed my mind.

When I used that spreadsheet to map out the compressor map, I entered 80% VE, as that is what is the accepted VE of one of these engines. I have thought about it before, that boost increases your VE, but never really messed with the calc. I just changed VE from 80% to 95% and 100% to see the differences @ 30psi and its pretty dramatic, and throws me way off the map past 25psi. Is this the problem with my maps?

I posted this up on theturboforums, but I wanted to hear from turbo educated diesel guys as well.

Thanks in advance for the help.
 
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I am no expert for sure, but I agree that with turbocharging VE will jump up dramatically and that could be some of the issue.
 
well i see two things.. your not "that" over fueled, egt will tell more of the story. and second that turbo should be good for an easy 450hp and i am impressed even more if you are even close to that.. looks like you have a pretty good runner, drive it and watch those egts.. i heard long ago those idi's dont like going over 1100 pre turbo.
 
DEZLFREK said:
well i see two things.. your not "that" over fueled, egt will tell more of the story. and second that turbo should be good for an easy 450hp and i am impressed even more if you are even close to that.. looks like you have a pretty good runner, drive it and watch those egts.. i heard long ago those idi's dont like going over 1100 pre turbo.
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As for EGT's, truck will hit 1200 pretty easy, but basically hits the wall @ 1200*.

Bill @ bullseye told me this was due to an efficient/large turbine and exhaust housing....he said it offsets all the raw fuel in a sense.

As for the turbo being good for 450hp, that is what I was understanding as well when I picked it up.... I paid $100 for it new so I'm in good shape anyways........ however, I only made 300rwhp/615rwtq when I dynoed. Coast down revealed 29% drag... so about 380hp/790tq at the flywheel....

These are great numbers for an IDI, however, doesn't seem right. "built up" IDI's and stockers alike are usually in the 2.4-2.7rwhp/cc range.... My truck was only @ 2rwhp/cc.... and I was only able to hit 27-28psi on the dyno. Bill tells me that with a better wheel, I can increase the air flow without increasing boost... this sounds like what I need.

I'm just trying to figure out if there was something I was missing, and just some general insight. Thanks for the response.
 
i would agree the billit comp wheel will not hurt you in any way and for the 450 upgrade your only into it for the 550 and i think you are golden..
remember most leaner combos are more efficient so hp per cc will usually go down with higher cc's unless your running cubic $$$ in a comp puller..
are you running a ic?
also did you do piston squirters?
 
DEZLFREK said:
i would agree the billit comp wheel will not hurt you in any way and for the 450 upgrade your only into it for the 550 and i think you are golden..
remember most leaner combos are more efficient so hp per cc will usually go down with higher cc's unless your running cubic $$$ in a comp puller..
are you running a ic?
also did you do piston squirters?
Click to expand...


these engines have piston squirters stock.

Yes intercooled as well...

IMG_4244.jpg


I have been reading a lot of articles on volumetric efficiency, and my first mistake was assuming VE had anything to do with engine efficiency, or burning the fuel.

That being said, it sounds like my cam profile, along with boosting the engine more certainly bumps the VE from the stock 80% range.

Just a WAG, I remapped it from 80% to 95% VE and it makes the map look like how the engine feels in real life.

I'm looking for probably another 15lb/min. Bill @ bullseye told me the billet 62 has a peak flow equivalent to the stock S364... but I can't find an S364 map.

I almost feel like I'm over thinking it, but I don't want to spend $450 on something that isn't enough.....
 
its never enough bro.. LOL
and it looks good. if it were me i would do the billit 62 wheel..
 
thanks. Truck is going to the body shop tomorrow to get pretty. I'll have it back in two weeks.

In the mean time I'll call Bullseye and see if he can give me real numbers on that billet wheel before I pull the trigger.

I'll keep you guys updated. Thanks for the help, and any other insight others might have.
 
Just got off the phone with Bill and thought I'd jump on here to share what he determined.

Basically, my turbine side is too large for the fuel I'm pushing. This is allowing me to have low EGT's, but its giving me "false" or "lazy" boost. The compressor isn't actually reaching the RPM shown on the comp map, due to the turbine running slow.

He also guessed my other symptoms of smoke @ low load highway cruising, ect.

I also told him I'm moving to Colorado in a few months, he recommended the bullseye 62/65/12 or 62/68/12 for being a tow rig. He said this fill fix my problems.

So, my charger will go up for sale, he told me my specific exhaust housing and turbine wheel by themselves are worth $1000, so hopefully I can try to get half of this new charger paid for!

Thanks for the help and insight here, I'll let you guys know the results when I finally get the truck back from body shop, and a new charger, and back on the rollers!
 
Smoke is kind of a poor indicator of turbo performance. Smoke also depends on the fuel injection characteristics. You might be able to clean up some of the smoke by injecting the fuel sooner, it's not all about the air.

It's good to hear that Bullseye is working with you to solve the problem. Let us know how it goes when you get the new wheel on.
 
wildman6bt said:
A 6.9 can handle boost holy sh!t! LOL awesome! Good lookin setup man
Click to expand...

I know right!

I have a lot of time and research into this engine trying to make a diamond out of it. I know its not a heavy hitter like the CTD's and newer CR stuff but if I can get it to the 400/800 wheel marks, that's nothing to bat an eye at, and its awesome for an IDI.

White Knight said:
Smoke is kind of a poor indicator of turbo performance. Smoke also depends on the fuel injection characteristics. You might be able to clean up some of the smoke by injecting the fuel sooner, it's not all about the air.

I have a timing meter, and a lot of time on playing with injection timing and on the rollers. IDI's generally run 8.5* BTDC and "hopped up" IDI's bump timing to 10*BTDC. My engine runs the most power/least smoke @ 6* BTDC.

It's good to hear that Bullseye is working with you to solve the problem. Let us know how it goes when you get the new wheel on.
Click to expand...

Bill was convinced, and just emailed me back after I sent pics to confirm that the turbine is my issue. He knows a whole lot more about these chargers than I do, and the issues he was describing this turbine to cause, are the issues I see... so hopefully I can pickup some power off of the table.

My one concern was that it would not change anything, and he said he was 100% positive I would not feel disappointed in the turbo swap... so I guess I'm going to jump into with both feet!
 
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Wow you IDI guys inject the fuel late. 12 valve Cummins come stock timed at 14* BTDC, and the hoped up guys set the static injection to start at 35*+ BTDC.

Bill knows a lot more than me too so he's the one to listen too.
 
The IDI guys inject late to keep the cylinder pressure down so they don't blow up their antique motors.....

Seriously, have you tried 14-15* of timing? I wonder how well it would run?
 
I used to run some of them before I got a dodge, 15 lbs. of boost and no intercooler pulling a heavy trailer will trash a motor in around 25,000 miles. The old 6.9 did run good though. I used to have several motors and would just throw rings and gaskets in them. Some of them were so wore out you could see almost the whole ring beside the piston. Aw, the good old days.

Good to see someone keeping the old idi motors going, those trucks had the best bucket seats and drove great unlike all the fwd dodges I've owned.
 
White Knight said:
Wow you IDI guys inject the fuel late. 12 valve Cummins come stock timed at 14* BTDC, and the hoped up guys set the static injection to start at 35*+ BTDC.

Bill knows a lot more than me too so he's the one to listen too.
Click to expand...

The injection events are timed differently, so its not apples to apples on the numbers... I thought like you did too until I was corrected by my injection shop who educated me a little bit on it.

Big Blue24 said:
The IDI guys inject late to keep the cylinder pressure down so they don't blow up their antique motors.....

Seriously, have you tried 14-15* of timing? I wonder how well it would run?
Click to expand...

It wouldn't run. Read above post.

I did get to thinking though... When I was tuning the engine early on I ran it @ 8.4* for awhile. @ 8.4* I had zero smoke at idle, and it got rid of the low load smoke....(currently I smoke at idle and have smoke @ lower loads) however, it made the turbo extremely sluggish, and the EGT's/smoke insane.... I wonder if with the new charger... 8* is going to be the ticket.

6* is just where it runs best currently.
 
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Had a good conversation with Chris @ engineered diesel this morning. He pretty much agreed with what Bill @ bullseye had to say about dropping turbine sizes down.

I also told him about when I advance timing how it smoked like a freight train, wouldn't spool... ect... and he said it all sounded right for having a turbine too large.

I'm going to be getting a new charger from E.D. and this current charger is up for sale.
 
So, one thing I learned today is that I measured my turbine wheel wrong. I thought you measured larger DIA.

So, my charger is really 62/65/14.

Did a little testing against my buddies truck. I never noticed how laggy my turbo was below about 1900rpm - 2000rpm, its a dog. Buddies with less fuel fires this turbo off around 1400. This must be his extra displacement, and higher compression.

Once I hit 1900rpms... I waste him though.

Got to thinking about the injection timing again... 30psi really is enough air to support much more power than I have, and I looked at other cases of poor timing. It seems that even on the other platforms, when running too narrow of timing no matter how much boost, it hazes smoke due to a poor burn.


The 68mm wheel is 10blade vs 11. This means that with the 3mm larger discharge port, and 1 less blade, that wheel should flow more, and spool faster due to the extra surface area, coupled with 12cm housing... I should get the proper amount of drive pressure against it, and be able to spool it with the engine timed properly.

So, I am thinking of going to a 62/68/12

Like I said previously, when I advanced the timing, the engine ran much better... just wouldn't spool the turbo very well....

Does it sound like I have a better understanding of whats going on now?

The one thing I can't understand though... how does the later timing help me spool the turbo better?
 
NMB2 said:
The one thing I can't understand though... how does the later timing help me spool the turbo better?
Click to expand...

Think about what you're doing by reducing the BTDC timing. Starting the burn later gives it less time in the cylinder before the exhaust valve opens. This means more combustion energy is exiting the cylinder and making its way to the turbine - quicker spool. :ft:

Inversely, this is why advancing the timing is usually accompanied by a reduction in EGT; you are capturing more of the burn in the cylinder.
 
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