Compressor Efficiency Problem

[Killerbee]

Just to stir up some fun!

Johnny is given a choice of modifications to make to his induction system. Each involves the reduction in restriction/pressure loss. The vehicle in question is a MAP sensor governed variable geometry turbocharged LLY Duramax. In each case, intake plenum pressure is governed to the same 34 psia of MAP. Assume sea level.

Option A involves reducing the losses upstream of the compressor. The improvement is a 2 psi reduction in losses. It involves a redesigned intake box and plumbing. The cost is $400

Option B involves reducing the losses downstream of the compressor discharge. The improvement is also a 2 psi reduction. It involves an optimized CAC, new boost tubes, and improved intake riser, at a cost of $1600

Questions:

1. Which option should Johnny go with, and why?

2. Which option has the best performance improvement, and why?

 

[LarryJewell]

My vote goes to Option A, but Option B is holding some interest as well, Care to elaborate some more?

 

[Killerbee]

It is an Induction 201 course problem, modified a bit for our application. I thought it good to share with the performance oriented crowd.

No guessing Larry. Need rationalle.

 

[McRat]

Not sure PSIG or PSIA so I'll assume PSIA.

2PSI improvement pre turbo is 2/15 or 13%.
2PSI improvement post turbo is 2/34 or 6%.

HOWEVER...

If you are losing 2 PSI on a modern engine pre turbo, you've got something screwed up. Low hanging fruit. GM, Ford, and Dodge have targetted the easy HP like air cleaner restriction.

 

[Killerbee]

Just to be clear, the 2 psi improvement, is a reduction in losses, not an improvement in boost output. Boost output at the plenum will always be the same, per the histogram, approx 34 psia, which is 20 psig if near sea level.

The hint is in the thread title.

BTW Pat, 2 psi pre-compressor doesn't begin to approximate the LLY losses. Before today, if anyone had told me that, I would have said they were crazy. I had to by a 3rd magnehelic for the collection, because my old one only went to 50 inches water column.

 

[McRat]

The engine doesn't seem to give a shit then. Put a stock LiLLY on a dyno. Do a few pulls. Remove the air cleaner and try again. Unless the filter is dirty, you won't see more than 1% HP.

 

[Turbotug]

I see you've made some headway since yesterday?

Even worse than you thought?

Just a guess, but are you using vane position to approximate %.

50+ in. Shouldn't that help with pre-compressor evap cooling too?

 

[Killerbee]

I agree with you 100% Pat. It's not in the air cleaner.

 

[Killerbee]

Even worse than you thought?

considerably

 

[JOHNBOY]

As to plan B

How are you going to inprove loss down stream. My LB7 CAC showed so little pressure loss that I in all honesty. If you gained 2psi at the intake neck the pressure would be higher there than at the compressor outlet. That would be a neat trick.

I have done a fair bit of testing the stock CAC setup for both pressure loose and charge tempature. I was honestly suprised how well the stock CAC performed. With a Stock turbo I feel the stock CAC is just fine.

To me on a LLY I would look at a better intake neck setup as it is not as smooth flowing as the LB7.

 

[Killerbee]

I agree the LB7 has little room for improvement downstream. The LLY is a concession. compliments of GM, from the LB7. There is a fair bit of restriction in the downsized boost tubes, and related transitions. Especially when IAT climbs upon fan engagement. Just assume there is a 2 psi potential. I am also a fan of the stock Behr.

So what is your assessment Johnboy? A or B? Rationalle?

 

[LBZ]

That is exactly what Dodge has done with all those BD Aluminum Inlet's you see for sale.

They obviously thought the same.

Question is, why don't they or anybody else supply one for a Dmax?
Is there really not that much of a gain to justify the cost?
Why would they have stopped with the Dodge??

Just curious!!

 

[Killerbee]

1. Which option should Johnny go with, and why?

2. Which option has the best performance improvement, and why?

Topic questions. There is a point to all of this.

Where are the theory geeks? :hug: This is big time performance stuff.
I am not a performance wrencher, but this goes to much of a 2 year effort to unravel some mysteries about induction heat issues.

 

[Turbotug]

If they provide the same result in the end I'll take A and drop the other $1200 on new shocks for my Rhino.

It seems to me that if the induction was improved it would benefit the turbine side of the turbo (system) as well. If the compressor is able to take larger "gulps" of air then you could command less vane angle (? LB7 guy) to achieve the same desired boost. Less vane should allow lower drive pressures and EGT. Also slowing the compressor wheel down some not beating up and heating up the intake charge. Win WIn.


:dontknow:

 

[Mike]

Just to stir up some fun!

Johnny is given a choice of modifications to make to his induction system. Each involves the reduction in pressure (head) loss. The vehicle in question is a MAP sensor governed variable geometry turbocharged LLY Duramax. In each case, intake plenum pressure is governed to the same 34 psia of MAP. Assume sea level.

Option A involves reducing the losses upstream of the compressor. The improvement is a 2 psi reduction in losses. It involves a redesigned intake box and plumbing. The cost is $400

Option B involves reducing the losses downstream of the compressor discharge. The improvement is also a 2 psi reduction. It involves an optimized CAC, new boost tubes, and improved intake riser, at a cost of $1600

Questions:

1. Which option should Johnny go with, and why?

2. Which option has the best performance improvement, and why?

We are limiting the boost to 20 psi if baro is 14.0 right? 34 psia - 14 psi ( Around sea level atmospheric pressure = 20 psi read from normal gauge.

I have to say A if the intake from the compressor back to the filter is redesigned. I have to say at 20 pounds of boost turbulence caused from the bottle neck at the intake riser wouldn't be a big deal. I say A because the charger is being caused to spin faster { higher turbine speeds and back pressure } to allow a larger and larger pressure drop to occur. Because of the restriction, this pressure drop is the only way to allow a further amount of air into the inducer of the charger.

But, with added volume comes weight. This will also effect the turbine side back pressure. So unless option B reduces the temperature of the charged air considerably. 34psia is 34psia depending on where you are taking the pressure readings?

 

[sweetdiesel]

That is exactly what Dodge has done with all those BD Aluminum Inlet's you see for sale.

They obviously thought the same.

Question is, why don't they or anybody else supply one for a Dmax?
Is there really not that much of a gain to justify the cost?
Why would they have stopped with the Dodge??

Just curious!!

we could have a 6" riser and it still wouldnt help this is why i dont see the bennifits of bigger inter cooler pipes,BUT ive been wrong before

picture a milkshake you have a 1/2" staw or 12.7mm now the end of this straw is squished down to a 1/4" 6.35mm does it really matter that we had a 1/2" to begin with?

 

[LarryJewell]

So more air in + quicker air out = a happy turbo?????, ie; larger diameter, better flowing intake and larger exit pipe, better outfow?????


This isn't a guess..., I think its fact.............

 

[sweetdiesel]

So more air in + quicker air out = a happy turbo?????, ie; larger diameter, better flowing intake and larger exit pipe, better outfow?????


This isn't a guess..., I think its fact.............

Larry
i like the better out flow,its the inflow reduced at the lil manifold that bothers me

kinda like when you get the stawberry stuck in the straw

 

[LarryJewell]

needs to be big on both sides, maybe then the smoke would turn grey instead of black

 

[JOHNBOY]

I agree the LB7 has little room for improvement downstream. The LLY is a concession. compliments of GM, from the LB7. There is a fair bit of restriction in the downsized boost tubes, and related transitions. Especially when IAT climbs upon fan engagement. Just assume there is a 2 psi potential. I am also a fan of the stock Behr.

So what is your assessment Johnboy? A or B? Rationalle?

I would go "A" first. Before attempting "B" I would check somethings. One issue I do know of with the stock intercooler is Behr had some issues with sealing them up. BIGBLOCKBILL was the first one I know with this problem. His truck ran well but always dynoed low and his boost readings where alway low. What he found was his intercooler had a leak. I have seeen two other LLYs with this same issue. I have never seen it on an LB7. I have yet to pressure test a LBZ yet. If the intercooler checks OK I would look into a LB7 CAC outlet tube and a more open smooth flowing intake manifold neck.

Mike (New_2_LB7) bring up a good point about air temps. With a stock turbo the Behr does a fine job keeping the temps in check. I really doubt you would gain much if any by going to either a Banks intercooler (stock intercooler core with different tanks IMHO) or the Spearco/PPE. I would love to try adding a water to air intercooler after the stock CAC for giggles! I think that would be and interesting dyno session!.

Back to "A". I would try to seal the intake off to the rest of the engine bay. That way you could help limit heat coming in thru the filter. I would use as smooth and flowing of turbo inlet tube I could that was made of plastic. (For and LB7 the K&N FIPK kit is very nice.) I would wrap it with some form of insulation. This is all done to limit radianant(sp?) heat.

And OT observation from a LB7 guy about the stock LLY LBZ turbos. While VVT is neat I still not sure I like it. The control over your boost is great but it is very easy to just make boost and not power with. Also one another thing is IMHO the lack of a wastegate really hurt things IMHO. To try and prevent overspeed the turbine housing is pretty loose. This doesnt help spool up. The vanes do make up for alot of this but the VVT still just doesnt spool like I wish it would. Like my stock LB7 would. Yet another thing I have seen is the fact the the VVT does not carry the powerband out like and LB7 turbo. What I mean is peak power is around 2800rpm with both chargers. But at 4000 rpm the LB7 is making a fair bit more power. I beleive this is because of the wastegate. Another interesting dyno test would be to have a external gate mounted on one of the up pipes. I think this could really free up some HP after 3000rpm by helping lower drive pressures. There comes a point where no matter what you do with the vanes that the turbine wheel is simply spinning so fast that it is in a sense closed. This is when drive pressure really starts to climb. An external gate would really help that. I would not be suprised to see an external gate cause two other helpful things. First I would not be suprised at all to see the air charge temps drop. Second I would guess that if the gate was not sized to large you would see at drop in "Gaged Boost" after 3000rpm but would see power go up. You would have less pressure but be moving more air volume. Everybody likes to think that tubo is free power because it has no direct connection to the crank. Well nothing is free!:rofl: The turbine side of the turbo is large cork in the over all flow of air. Managing the BP would help free up some power IMHO.