Turbocharger information

[Big Blue dsl]

Hi all,

i am in the process of building a new engine for the ol' blue general and in the midst of my planning i am stumped... i want to build an 18:1 engine. i want a turbo, i have a "599" block from the diesel depot and now the only issue to adress is the turbo. what would the best turbo be for the application, i will not tow and if i do it will be very light,comparatvely to the travel trailers that others tow i have an intercooler the size of one from a cummins truck, but here is where the dillema arises, will the gm-8 have a quick spool up,and deliver enough boost in street driving to match the fuel of a 300 hp pump,by my way of thinking,the turbo will spool up according to the fuel i give it. or is a better option a mitsubishi turbo like brittanic's, or then again would i be better off with a custom setup built to what i want to do with the motor,i would like to hear any opinons on this subject and what others have found that works.

sorry for the long post
chris brien

[rjschoolcraft]

Well, the Project Truck uses a GM-8 Turbo and the big Penninsular pump. It seems to work well.

[GMCfourX4]

The best response from a turbo on a 6.5 that I've ever seen was on a truck that had the ceramic crossover, and he had header-wrapped the crossover and the downpipe.... It was intercooled, and worked extremely well. I intend to do the same to my truck. I also think the Heath boost control builds boost much faster than the computer/vacuum wastegate control (mine always seemed to be at ~75% duty cycle max...). Both my truck and the other truck I was referring to had GM-8 turbos...

-Chris

[patrick m.]

talk to britanic about your turbo desires. the GM8 has a small turbine housing much like the gm4, it will spool up very quickly, however, it will quickly become a bottle neck at higher rpms.
i installed a much larger turbo, and it spools up much later, but i didnt loose much (if any) low speed power. i gained a tremendous amount of power at cruise speed.
If you have to buy a turbo (i dont know if you have the "8"). peninsular sells a nice turbo for the 6.5. JK sells one too they arent that much $700-$900 i think.

[Uncle Wally]

Turbos? This is always a good subject!

The smaller the impeller, the quicker you get boost pulling away from the stop light. If your gona drive around town, this might be your best setup. When I was looking into turbo's earlier this year, I found a few in the 510 range for a rebuild. Reasonable as far as I'm concerned.

The larger the impeller, the longer it takes to spool up, and the slower the response from the stop light. In JK's word's: the bigger turbo will lack a little on the bottom end, but once ya get her up in the rpm's, it'll blow by the other's and never look back.

There are a couple things you can do to decrease the amount time for spool up. This all has to do with thermal efficiency of the engine. If you are doing a whole motor, I would use the thermal barrier coatings available and coat pistons, cylinder heads combustion chambers, exhaust valves (not the seating surface though), exhaust ports and exhaust manifolds. Then get JK's mandrel bent ceramic coated crossover pipe. To finish things up, insulate the exhaust side of the turbo housing and the downpipe.

For myself, I went with the 250 HP turbo from Peninsular Diesel. It has a much larger impeller without the wastegate. I then purchased a chip (mine is electronic) from JK that eliminates the boost signal so there are no SES light or code issues. I have not gone inside the engine yet, but I did do the exhaust manifolds and the ceramic crossover. The results were unbelievable! Needless to say, I would do it all over again if I had to replace the turbo. It was kinda expensive, but worth it. I got a new truck! All in all, the turbo was 750, the chip 350, exhaust manifold coating 125, stainless ARP exhaust bolts 150 and my time. It also required fabbing up a something different for the oil return line as the stock one would no longer bolt up. A stock replacement turbo was in the 510 range without shipping.

Feel free if you have any questions, if I can't answer em, there are a ton of people on here that can!
Good Luck!

Waldo

[patrick m.]

Uncle Wally, what is your max boost level?
is that 250 hp model a "holset"?

[Kennedy]

Wally,

I too would be curious as to the Peninsular "flavor of the month" turbo brand???

How much boost can you make?

Glad I studded my heads as I hit 21 easily, and 25 loaded! :eek:

[Uncle Wally]

I'm not sure. I'll have to check as to the brand name. I remeber garrett for some reason. I'll let ya know next week when I get back from work.

Boost levels. >15. I estimate 18-20 max unloaded. It's even more loaded. I got nervous with boost and EGT levels on the one full throttle run I made with a fully loaded horse trailer. Engine internals are stock for now and I haven't gotten to the intercooler yet.

John: What do you suggest for make making one of these live with all that extra boost? 18:1 pistons, head studs and quality head gaskets? Has anyone ever tried 'o ringing' the block on one of these? Or do they not make a compatible head gasket for use with o-rings? I'm sure once I get the trans done, it won't be long until I find the next weekest link in the package!

Waldo

[Uncle Wally]

John,

I finally got the information off the tag on my turbo.

Borg Warner
173379
S2E
F2803
971

I'm not sure what all that will tell you.

Waldo

[Spindrift]

What impact, if any, will an insulated crossover and downpipe have on a "relatively" stock 6.5TD?

[patrick m.]

with the big Garrett i have, im going to insulate my crossover pipe to "quicken" spool-up.
With all the talk about the great improvement new injectors provide,,,,think i'll do both at once.

[Uncle Wally]

Theoretically - turbo efficiency has a lot to do with the thermodynamic efficiency of the engine.

Meaning - you want as much of the kenetic energy of the exhaust gas exerted on the turbo. Kenetic energy is directly proportional to temp.

Sooo

If you build the engine to loose as little exhaust temp as possible, you have more to work the turbo. To do that, you need to build everything to keep the heat in the exhaust gas. Hence, you hear all about ceramic or temp resistant coatings used on pistons, valve heads, exhaust ports, exhaust manifolds, crossover pipes etc.

This will allow the turbo to spool up faster.

I installed a considerably larger turbo on my truck (without wastegate), with ceramic coated exhaust manifolds and JK's crossover pipe. And then wrapped the crossover and downpipe. It comes off the line a touch slower than with the stock turbo (which doesn't really matter much), but it goes like gangbusters after that. And I haven't even touch the combustion chambers yet! I still have some left on the table should I rebuild the engine. It makes a diff, albight, a small one.

Waldo

[gmctd]

In the GM-X series turbos, the turbine and wastegate have been sized for driveability, meaning quick spool-up off-idle.

The inherent problem with this is that the turbine becomes too restrictive at higher rpm, where greater exhaust volume and velocity are available, needing larger area for proper flow.

Wrapping the cross-over would increase the effect of this restriction, where exhaust back-pressure increases to higher levels than boost, resulting in lower power.

Power begins to fall off at around 12psi, unwrapped, but the available power is immediate - driveability is how GM expresses it.

[ 01-26-2004, 09:04 AM: Message edited by: gmctd ]

[grape]

not to mention the wastegate valve itself is under an inch in diameter. This is what is used for your exhaust system once full boost has been achieved. So you have exhaust going through a 2 and something inch exducer on the t3 series turbos along with the dinky wastegate. OF COURSE THEY DON'T RUN ON THE TOP. GET A TURBO DESIGNED IN THIS CENTURY, WITH A WASTEGATE. Modern external gates are available in the 1.5-2" range...to keep the exhaust housing small yet still flow enough on the top. Not using a wastegate is 30 year old technology.....but whatever. Information on modern turbo technology is out there but nobody cares to look. Not to mention it is absurd to have to make over 20 pounds for 300 horsepower's worth of fuel. A simple 62-1 compressor map moves enough air at 14 pounds to make 350 horsepower.

[gmctd]

If flow velocity thru a fixed area (the small outlet diameter of a centrifugal compressor such as the GM-8, or the Holset, or Schwitzer) increases above the speed of sound, the only way to further increase flow rate is to increase pressure. Without increasing area - pie are squared.

Right?

[MJEasly]

Here (http://www.turbofast.com.au/TFmatch.html) is a link to a turbo selection calculator. Have fun...

BTW, I have not been able to locate a compressor map for the GM8. A map will be able to tell you about how much boost to run before efficiency begins to drop.

[grape]

That's a real cool calculator.....even gives a baseline start on the exhaust a/r. Big surprize the banks is a 1.0 and they say to start with an .82

[britannic]

Originally posted by grape:
That's a real cool calculator.....even gives a baseline start on the exhaust a/r. Big surprize the banks is a 1.0 and they say to start with an .82 What boost, max rpm and engine size figures did you use? I plugged in 16psi, 6200cc (for my 6.2L), 3600rpm max and got 1.06 A/R. On my 6.2L with the Banks hybrid T04B, I was seeing over 17psi under WOT on heavy grades in 1:1 gear ratio with 4.56 diffs.

[Dieselboy]

Brittanic: It looks like you clicked "yes" for intercooler.

[britannic]

You're right, that's what it was!