Turbos

[DT]

Does anyone one this site have a pretty good knowledge of turbos?



As a few of you know, I installed a 6BD1 Isuzu Diesel in my chevy truck. (5. 8 liter straight six, direct injected, inline pump, chrome liners, etc. )



When I got the engine, I fabricated a turbo setup using a T04E10 Garrett Turbocharger with an A/R of intake- . 50, exhaust- 1. 0.

You guys probably aren't as familiar with Garretts as with holsets, but I assume that the last part of the model number (10) stands for the size (cm) of the exhaust housing. Am I correct or does this stand for the size of the intake housing? The factory spec'd turbo for this engine is a T04E12.

My max boost right now is about 12 lbs. I can reach 1200* pre turbo real easy. I can get to 10 lbs real quick.

I want to get 20+ pounds of boost.



So my question is, in getting a T04E12 turbo, would I just be getting a bigger exhaust turbine (therefore helping to lower my egt's), and should I step up to something like a T04E14? (If there is such a model. )



Also, does anyone know if a holset is the same bolt pattern on the manifold as a garrett? How much does a new HX-35 cost? Non wastegated?



Thanks a bunch for any and all help.



BTW- I also am using a custom intercooler, with 2" pipe to and from, (I know that's too small) and 3" straightpipe exhaust.

 

[Diesel Freak]

I noticed that you said that the engine has Chrome liners. does this mean that it has an aluminum block, or are the bores plated with the "nikasil" lining?



If you are only putting 12 PSI to the engine, is it possible to go higher without hurting anything?



Turbonetics specializes in Garret Turbos, and can build you almost any T04 turbo you want.



I wish the CTD came with a Garret at times.

 

[DT]

Diesel freak-

no, this engine has a cast iron block and head... the liners are chrome dry liners...



The main reason I am only putting 12 psi is because of egt's, although the turbo does start to seem to hit the "surge limit" around 12 and starts to fall off...



I should be able to put just as much boost as the cummins... I have 17. 5:1 compression ratio, stellite valve seats, replaceable valve guides, etc.



Thanks for the link to Turbonetics...

 

[Diesel Freak]

if you were to push it to 20 psi at Governed RPM and still have the turbo in the compressor map, your EGT should drop.

 

[DT]

I think it's getting off the compressor map at around 12, it just gets there and then kind of starts to drop. . of course that could be my involuntary reaction of my foot as I see my EGT's climb.

I would really have to push it to probably around 1700* to get 20 lbs if it's even possible... I still only get 12 lbs at about 1450*...

Even if it is possible, I am looking to get more boost without the threat of melted pistons, pitted valves, cracked heads, etc.



Thanks for the suggestions, keep em coming...



On edit- I just plugged the numbers in at http://www.turbofast.com.au/javacalc.html

and it is possible to get twenty pounds on a T04e compressor with a trim of 60... I don't know if I want to try it, though, that would really be pushing it...

 

[Diesel Freak]

does your current turbo have a wastgate?

 

[GSchlegel]

Just a thought, are you fighting too hard to push the air through the 2" pipes to and from your intercooler?



Gene

 

[DT]

diesel freak- no, my current turbo does not have a wastegate.



Gene- You know, I have thought about that, and it definitely is alimiting factor (someday I want to replumb to 3", wasn't thinking when I did it in 2") but I think even with two inch, with a turbo to compress the air, I should be able to get at least 20 lbs with the right turbo... (if people like you with 3"(right?) are getting 30 lbs or more. )(in some cases lots more) Naturally aspirated would be a different story...





Thanks for all your suggestions...



BTW- here are some pictures of the engine and turbo-

http://www.picturetrail.com/turbokid



(I know the turbokid part seems kind of hypocritcal. )

 

[Diesel Freak]

Have you checked the drive pressure you have at 12 psi of boost? I think your turbo may benefit greatly with a larger compressor wheel/housing to move more air rather than a different turbine housing. But that is just a suggestion.

 

[Lil' Dog]

If you are getting high EGT you should try to measure the intake manifold temperature if you can. . I should be in the range of 120° - 140°F if the intercooler is helping at all. . If thats the case then as already suggested, test the drive pressure of the turbo with a gauge on your pyro fitting. If it is much higher than your boost, the housing is the right way to go.



From what you have stated, I think a little lag from a larger exhaust housing may pay off with lower EGT's if the compressor can keep up.



BTW The picture server was having probs this morn, didn't get to see your install. .



J-eh

 

[DT]

Diesel Freak- That's a good idea... I was actually thinking about that, I was wondering if a t04e12 turbo came with a bigger compressor wheel or not... I've never really thought about checking the drive presssure, thanks for suggesting it! So if I get say, 20 lbs of drive pressure, I should be able to have a compressor housing to push 20 lbs? How would you reccomend hooking a boost line to measure the pressure without melting the line to the guage?

With a bigger compressor wheel, I should be able to lower my egt's because I'm getting more air through there, right?



Right now my compressor side is about the same as my turbine side, I've noticed on the cummins, the exhaust side is much smaller than the intake side... (More air, quicker. )



Lil' Dog- That's a good suggestion to measure the temperature of the intake manifold... After a recent hard pull, I got out and felt the pipe coming out of the turbo, the drivers side of the intercooler, middle of the intercooler, passengers side, then the intake manifold, and it got progressively cooler as I went, so I think it is helping somewhat at least...

Do you have any suggestions on not melting my boost line?

The picturetrail server was not working? It usually does. Hopefully it's working now...





Thanks a bunch for all your suggestions, they have helped a lot.

Keep 'em coming, if you haven't ran out of ideas.

 

[RustyJC]

Just to understand what the system is doing, I'd get a turbocharger discharge pressure and temperature right at the compressor outlet when the air manifold pressure is 12 PSIG. This way, you could quantify what the pressure drop is through your 2" piping and intercooler and determine if it is or is not a problem. Drive pressure (i. e. , exhaust pressure at the turbo inlet) at this same condition would help as well.



Rusty

 

[DT]

RustyJC - Actually, my line is already at the discharge of the turbo, it is actually on the only 90* elbow in my system, and it is lined up with my turbo outlet, so my guage might be reading a little high

I have actually thought of putting a line on the other side, after my intercooler and piping, to see how much they decrease my pressure.

I guess I do need to find a temperature probe for my intake... what's a good one that reads that low?

Thanks for the suggestions...

Would you recommend a copper line to the boost guage to measure drive pressure? (So the plastic one doesn't melt. )

#ad

 

[Diesel Freak]

DT, move your boost pressure line to the intake manifold! Do not be supprised to find that you may be losing 4 to 6 PSI of boost from your current intake system from flow restrictions.



When checking drive pressure all you should need is 2 feet of copper tubing before you tie into your existing poly line. This should be adequate for the short time it takes to check turbine drive pressure at full boost.



On my truck I have a K type TC in the intake horn that I can plug into a digital multi meter. On the dyno I saw no more than 91F for intake temp at over 30 psi of boost, but keep in mind that this is on a CTD on a very short run... temps would be higher when towing.



What is the governed RPM for your engine?



I am going to go out on a limb and say that your current exhaust housing is large enough, but the turbo can not push enough air into the engine at governed RPM to keep things cool. Once you find out what drive pressure is, and the actual boost pressure the engine sees at the intake, then you will have a starting point to spec your turbo for.



For things to work really good, shoot for not much more than 1100F EGT pre turbo at governed RPM and full load, and try and keep drive pressure lower that intake manifold pressure.

 

[DT]

Diesel Freak- I thought (sometimes I do) about moving the boost line to the manifold... at the time it was just easier to put it where it is... I'll have to move it...

The governed RPM of my engine is 3200.

I think you are correct on what you have to say about the exhaust housing being big enough... from what I have heard in this post I agree with you...

I turned my fuel down a tad tonight as an experiment... It takes longer now to get up to max boost, and my egt's are a tiny bit lower(50*), and they don't climb quite as fast... or maybe it's just me. .



But anyway, I agree with your "limb" statement, I think that with a larger compressor housing and wheel, I should be able to see more boost with at the very least no increase in egt's and hopefully a decrease in them... am I correct?

I think I'll rig something up tomorrow hopefully to check my drive pressure...



Thanks for all your suggestions, guys, they have been very helpful.



Any more?

 

[DT]

Ok, guys, I just checked my drive pressure, and it reads almost exactly the same as my boost pressure (measured pre- intercooler).

So, in other words, it is more than my boost pressure post intercooler so I have room for improvement, right?

If I increase my compressor size, I will also increase the amount of boost pressure, and therefore the amount of drive pressure, right?

Also, I noticed, when I was at full drive pressure, and I let off the throttle quickly, the pressure dropped abruptly 3-4 lbs... is this normal?



Thanks for any suggestions/comments...

 

[Diesel Freak]

I think your best bet would be to call Turbonetics, and tell them what you have and where you want to go with your existing turbo/engine

 

[drees1]

Turbo sizing

Turbo sizing is both an art and a science.



First, you must determine the objectives. Where do you want the performance? Top end, racing? Midrange crusing and towing? Fuel economy crusing?



Start with the desired rpm range, and estimate the maximum amount of power you want there. It needs to be realistic. Crusing rpm, and a reserve of boost is a good point to use for general purposes. For example, in moderate towing, my Cummins will run 10 psi boost, at 70mph at 1900 rpm. But my match would be for 20 - 25 psi at same rpm to allow for more power on demand.



For this power level, you will need to predict approximately, the boost required, and the mass flow (lbs per hr) of inlet air it will take. This is the hard part, but can be estimated based on experience, or calculated by someone familar with engine design. You can also model your conditions after other diesels with similar HP and displacement as you are looking for in yours.



Next get turbo compressor maps from the turbo vendors. These maps plot pressure ratio (boost) vs. inlet air mass flow and have eliptical circles called efficiency islands on them. The goal, no matter what your "objective" is to match one of those maps so that your design point is in the center of the highest efficiency island. When you operate efficiently, you generate best boost with least heat and the exhaust pressure will be less than the inlet pressure making the turbo actually contrubute to better fuel economy. Also. by operating in the best island of efficiency you have the most lattitude to move on the map, which means good performance at other points of operation. Different turbos have very different maps, so you will have many choices. Some have skinny islands which have very high efficiency and must be matched closely. Others are more broad and will allow some mis match with still decent performance. Pick your turbo frame size and compressor housing based on plotting your pressure ratio and mass flow in the maps. This is the science part.



Install it and test. Now you can use different exhaust housings to trim it better up or down. A larger housing will raise the rpm that boost builds and reduce EGTs. Smaller, the opposite effect. Be sure to use an exhaust housing that matches the manifold if divided or not divided at the housing entry. Usually, an exhaust housing that is in the middle of the range offered is a good starting point.



Thats pretty much it. If you get your predicted mass flow and boost right your turbo match will do well at your operaing point(s) you selected. One or 2 exhaust housings should trim it to perfection.



I think the aftermarket turbo companies would be glad to help you size up your situation and supply maps. Also fuel injection shops that rebuild turbos can get maps too.



Good Luck, you have a fun project, and a good base engine to work with.



Doug Rees

 

[DT]

Doug- Thanks for typing that much and for all the good pointers on turbo's... How does mass flow relate to the Volumetric efficiency of an engine?

You've given me some great insights into the sizing of a turbo...

Thanks once again, I'll have to get some compressor maps...

 

[TxDieselKid]

Good post doung, thanks for posting all that.



Andrew