Turbine Doc
Just Another Diesel Guy
I got rid of my IC and have not regretted doing it
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Turbos & intercooling
- Thread starter Turbine Doc
- Start date
buddy
Active Member
Water injection would be better than intercooling
ak diesel driver
6.5 driver
I have a hard time getting excited about wmi with the cold winters here. My uncle used to say " we don't have summer just 3 months of tough sledding" 
buddy
Active Member
If its always cold why do you need an intercooler
ak diesel driver
6.5 driver
I tried to think of some witty reply but couldn't
docdray
Oompa Loompa
consider putting cost of intercooler toward a $750 turbo like Tdoc says, less iat's and backpressure=not as much stress on engine. was I right in that the ATT can flow about twice the cfm's as the gm-x at lower psi??
ak diesel driver
6.5 driver
already have intercooler
Turbine Doc
Just Another Diesel Guy
If you aren't running high boost, this is one area where Bill H and I disagree, WMI has finite supply, if you are going to spend a lot of time 10 psi or better boosting,(towing) ATA or WTA IC has unlimited cooling, yes you do lose some performance with an IC, but you aren't having to refill a resevoir from constant spray on your WMI tank.
That said as I have said in other posts, as tech changes so does my thinking, with ATT not really getting high IAT's, for those times you do get high IAT territory, WMI as required would be the ticket.
Turbine Doc
Just Another Diesel Guy
If not installed sell it, that is what I plan on doing with mine eventually
Turbine Doc
Just Another Diesel Guy
Here is something I sent to Unit-453 when he asked if Dmax IC was viable for the 6.5 he had a buddy wanting to sell his and wanted to give us 6.5 guys a shot at it, I told him viable not the easiest of installs, and also sent the following observations:
As it turns out the IDI precombustion chamber likes some heat, 150F or so IAT is perfect for 6.5 best econ, cold dense air is best for power, what I found with my ATT install is that without the IC I actuallly accelerate quicker.
Here is my theory, IC is a pressure vessel, that has to be filled and the filling process ever slightly slows flow of air to the engine, now dealing with high compression you can overcome this lag, but neither the GM-8 nor the ATT are high comp turbos, max out about 18 psi/
GM-8 is sized cfm wise to support about 200 hp at best compressor efficiency, you can get more but you are driving the piss out of the turbo, which has many negatives such as high IAT, above 10-11 psi with GM-8 turbo (oem) the temp of hot air almost is a straight line up 200+ and PCM defuels on high IAT.
ATT sized for about 600 hp going on rule of thumb 150 cfm for every 100 Hp, just not enough fuel in DS4IP to get there, so what we wind up with on ATT is due to its better compressing ability what used to take 6 psi boost to grunt the 6.5, the ATT grunts same with 3 psi boost,
I can run 100 mph now with just 10 psi boost, before with GM-8 it took almost 15 psi boost to do that, and harder you drive the turbo higher the back pressure in turbo outlet, like 45+ psi on the turbine for 15psi out of the compressor, so GM-8 conceptually is spinning backwards.
ATT same condition 18-22 psi backpressure for 10 psi, max IAT Iv'e seen thus far has been 198 on 95 ish ambient day me running 100+mph for test, I think if going for performance WMI might be the ticket as you would only spray when getting on it, controlled by a temp over pressure controller where both conditions have to be met before squirting of water begins.
Unit thought I might want to share these opinions, some of them are in the repalcement turbo thread, but follwing his advice have also posted here.
As it turns out the IDI precombustion chamber likes some heat, 150F or so IAT is perfect for 6.5 best econ, cold dense air is best for power, what I found with my ATT install is that without the IC I actuallly accelerate quicker.
Here is my theory, IC is a pressure vessel, that has to be filled and the filling process ever slightly slows flow of air to the engine, now dealing with high compression you can overcome this lag, but neither the GM-8 nor the ATT are high comp turbos, max out about 18 psi/
GM-8 is sized cfm wise to support about 200 hp at best compressor efficiency, you can get more but you are driving the piss out of the turbo, which has many negatives such as high IAT, above 10-11 psi with GM-8 turbo (oem) the temp of hot air almost is a straight line up 200+ and PCM defuels on high IAT.
ATT sized for about 600 hp going on rule of thumb 150 cfm for every 100 Hp, just not enough fuel in DS4IP to get there, so what we wind up with on ATT is due to its better compressing ability what used to take 6 psi boost to grunt the 6.5, the ATT grunts same with 3 psi boost,
I can run 100 mph now with just 10 psi boost, before with GM-8 it took almost 15 psi boost to do that, and harder you drive the turbo higher the back pressure in turbo outlet, like 45+ psi on the turbine for 15psi out of the compressor, so GM-8 conceptually is spinning backwards.
ATT same condition 18-22 psi backpressure for 10 psi, max IAT Iv'e seen thus far has been 198 on 95 ish ambient day me running 100+mph for test, I think if going for performance WMI might be the ticket as you would only spray when getting on it, controlled by a temp over pressure controller where both conditions have to be met before squirting of water begins.
Unit thought I might want to share these opinions, some of them are in the repalcement turbo thread, but follwing his advice have also posted here.
buddy
Active Member
I dont think with a fixed volume (intake and cylinder size) that you can have more CFM with less PSI since they are related. However the advantage on ATT is the no wastegate, lower backpressure makes the diesel more efficient at lower boost. As well as a more efficient blade pitch or turbine system in general, than our Borg-Warner OEM turbos.
NVW
Well-Known Member
Think of a water hose being choked off. The exh. back pressure is the choke, reduce the restriction and flow increases and psi goes down. Leo
buddy
Active Member
But the exhaust port is closed when the intake port is open right and vice versa? So the cyclinder would be the choking that doesnt change, which is why we go for higher displacement
I'm sure that youre right though, there has to be some greater flow into the cylinder allowed with the lower backpressure
I'm sure that youre right though, there has to be some greater flow into the cylinder allowed with the lower backpressure
NVW
Well-Known Member
But the exhaust port is closed when the intake port is open right and vice versa? So the cyclinder would be the choking that doesnt change, which is why we go for higher displacement
I'm sure that youre right though, there has to be some greater flow into the cylinder allowed with the lower backpressure
I don't know, seemed logical to me.:smile5:
Leo
Matt Bachand
Depends on the 6.5
Intake may be a fixed size, but engine demand/draw for air is a changing variable,
In order to make PSI you need to compress air.
The more CFM you put out, the faster your ability to compress air.
If the engine is drawing the extreme amount of air out of the turbo/intake, your PSI is limited by the CFM@PSI output of the turbo.
Just like any other compresser they are listed at CFM@xPSI.
If you put out 100 CFM @ 4psi (example)
Or if you can put out
200CFM @ 4psi.
In a WOT situation underload, you are maxing the turbo out. So if a perfect turbo for 6.5 puts out 200 CFM at 15psi, where as the stock one ran 100CFM at 15psi, the pressure of the intake will remain the same at 15psi, but the amount of air that is passing through will be doubled.
I need to read this outside of the small reply window to see if this makes sense
I'm just babbling away...But nonetheless, i complete think it is possible to have different CFM@PSI in the intake.
On edit i didnt' answer the different psi/cfm question or even come close, or any other question, but you got me thinking here and I'm going to leave this alone now.
A better example may be a shop vac on blow, can put out more air cfm than an air hose set to 30psi, due to the amount of CFM that can pass through it.
buddy
Active Member
I really think the added efficiency and power come from it being much easier to push the piston back up in the cylinder because of less backpressure, therefore the combustion in the other chambers is able to push the piston back down faster and so on. At least thats my theory
Turbine Doc
Just Another Diesel Guy
You can argue the theory but see if this makes sense, one of those cigarette lighter compressors says 250 psi, yes it can make 250 psi so long as you are filling a coffee can, now try to fill the tire, at 1/4 cfm, takes about 30 minutes with cooldown in between, now a shop compressor only rated for 150 psi, but doing is a 9 cfm, which fills faster say 2 minutes or less depending on size of the tire.
So here you have GM-X pumping it's heart out to fill the engine and it will do it given the time but working it's butt off to do it if you go beyond the demand it was designed for (195 crank hp), then you have the ATT working like shop compressor lazing along to make the same flow of air yet will never make the psi of the GM-X but providing the cfm required to make the power,
Read websites like Banks & others, also several books that confirm it's all air-flow, see multi stage turbo sets, compound turbos, or twin turbo sets they aren't upping the psi, they are upping cfm getting more air to the engine, once you have more air then you can add more fuel, change the timing to optomize the burn, change trans shift point to hold the power longer, etc.
You really want as big a turbo as your most flow demand will ever be, trade off is, when do you have sufficient drive energy to get it spinning. Get too big a turbo and bottom end suffers until you get turbo spooled up. That could drive one into looking at a supercharger, which has parasitic load issues(can be managed) and more complex than a turbo that has to be sized for the application but is free energy (waste gas) put back to use. Some engines use both turbo and superchargers, going again after the cfm and not the psi.
At some point both turbos and superchargers driven hard enough, need post compression cooling and there is some flow loss when you do that unless using something like WMI which is good but has finite supply and if spraying consantly from high boost demand requires resupply.
Going back to the portable air compressor analogy small compressor into a reciever once reciever is depleted compressor is playing catch up to refill it and you have to back off consumption of air until reciever is fill or you will never catch up.
GM-X is small compressor when compared to ATT, both will fill a stock reciever, (6.5 engine at power in this case), up the power demand though GM-X starts to fall off or has to drive so hard you need an IC to manage the struggle to keep up ie high IAT.
At some point it becomes almost chicken vs. egg argument, but all ICE's thrive on airflow, whether it be high cfm low psi, or high psi low cfm, remember back to basic physics when P goes up V goes down, and V up P down, like the garden hose put a nozzle on it you get a jet of water and small puddle, take off the nozzle and you get a big puddle fast. Yet both are creating a puddle just one does it faster than the other. Put on a bigger pump bigger nozzle bigger puddle but still not as big as the puddle same big pump no nozzle.
There is a lot of P over V math out there and compressor maps abound, you could debate over days; with ATT you have a dual scroll (not quite compound) that takes advantage V over P physics inside the turbo by way vanes and housing are shaped to have a turbo that makes more flow, but sacrifices some boost on bottom end the GM-X does, but GM-X lags behind the ATT at upper end as ATT does not "hit the compressability wall the GM-8 does on high end when pusing beyond design envelope of GM turbo. Evidence of the need Heath racer with 2 GM-X turbos making 153 mph, if a high psi turbo could flow the air, I think it would be on it.
That is as best I can splain it, some good books that if you read them and comprehend them my hat is off to you, as they tend to be written by engineers for engineers and sometimes you still can't get zactly what you are looking for in information.
Even though I have a lot of been there done that behind me most time it's about as clear to me as Mississippi mud.
Hopefully some of that rambling made some sense to you. Gotta go to work now. chat with ya'll later
So here you have GM-X pumping it's heart out to fill the engine and it will do it given the time but working it's butt off to do it if you go beyond the demand it was designed for (195 crank hp), then you have the ATT working like shop compressor lazing along to make the same flow of air yet will never make the psi of the GM-X but providing the cfm required to make the power,
Read websites like Banks & others, also several books that confirm it's all air-flow, see multi stage turbo sets, compound turbos, or twin turbo sets they aren't upping the psi, they are upping cfm getting more air to the engine, once you have more air then you can add more fuel, change the timing to optomize the burn, change trans shift point to hold the power longer, etc.
You really want as big a turbo as your most flow demand will ever be, trade off is, when do you have sufficient drive energy to get it spinning. Get too big a turbo and bottom end suffers until you get turbo spooled up. That could drive one into looking at a supercharger, which has parasitic load issues(can be managed) and more complex than a turbo that has to be sized for the application but is free energy (waste gas) put back to use. Some engines use both turbo and superchargers, going again after the cfm and not the psi.
At some point both turbos and superchargers driven hard enough, need post compression cooling and there is some flow loss when you do that unless using something like WMI which is good but has finite supply and if spraying consantly from high boost demand requires resupply.
Going back to the portable air compressor analogy small compressor into a reciever once reciever is depleted compressor is playing catch up to refill it and you have to back off consumption of air until reciever is fill or you will never catch up.
GM-X is small compressor when compared to ATT, both will fill a stock reciever, (6.5 engine at power in this case), up the power demand though GM-X starts to fall off or has to drive so hard you need an IC to manage the struggle to keep up ie high IAT.
At some point it becomes almost chicken vs. egg argument, but all ICE's thrive on airflow, whether it be high cfm low psi, or high psi low cfm, remember back to basic physics when P goes up V goes down, and V up P down, like the garden hose put a nozzle on it you get a jet of water and small puddle, take off the nozzle and you get a big puddle fast. Yet both are creating a puddle just one does it faster than the other. Put on a bigger pump bigger nozzle bigger puddle but still not as big as the puddle same big pump no nozzle.
There is a lot of P over V math out there and compressor maps abound, you could debate over days; with ATT you have a dual scroll (not quite compound) that takes advantage V over P physics inside the turbo by way vanes and housing are shaped to have a turbo that makes more flow, but sacrifices some boost on bottom end the GM-X does, but GM-X lags behind the ATT at upper end as ATT does not "hit the compressability wall the GM-8 does on high end when pusing beyond design envelope of GM turbo. Evidence of the need Heath racer with 2 GM-X turbos making 153 mph, if a high psi turbo could flow the air, I think it would be on it.
That is as best I can splain it, some good books that if you read them and comprehend them my hat is off to you, as they tend to be written by engineers for engineers and sometimes you still can't get zactly what you are looking for in information.
Even though I have a lot of been there done that behind me most time it's about as clear to me as Mississippi mud.
Hopefully some of that rambling made some sense to you. Gotta go to work now. chat with ya'll later
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Turbine Doc
Just Another Diesel Guy
On edit that looks like a coming out of the closet statement, or a Gieco commercial saying I just switched insurance
the provent thread http://dieseltowingresource.com/showthread.php?t=7964 was turning into a turbo & IC theory discussion so I moved those threads here.
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JMJNet
Recruit
This is a great info because putting an intercooler is not trivial and expensive.
It looks like with ATT, it won't need any intercooler because of its efficiency.
Hence, it is saving a lot of money.
Great job!!!
It looks like with ATT, it won't need any intercooler because of its efficiency.
Hence, it is saving a lot of money.
Great job!!!
ak diesel driver
6.5 driver
[
In a WOT situation underload, you are maxing the turbo out. So if a perfect turbo for 6.5 puts out 200 CFM at 15psi, where as the stock one ran 100CFM at 15psi, the pressure of the intake will remain the same at 15psi, but the amount of air that is passing through will be doubled.
A better example may be a shop vac on blow, can put out more air cfm than an air hose set to 30psi, due to the amount of CFM that can pass through it.[/QUOTE]
I don't think I agree with that statement and it looks to me like you didn't either when you reread it. IMO as long as the opening or duct size is fixed the only way to increase cfm is to increase pressure. I think buddy is on to something with his back pressure idea. I know TD has taqlked about back pressure but either I read it to fast or he didn't carry the thought out all the way.
In a WOT situation underload, you are maxing the turbo out. So if a perfect turbo for 6.5 puts out 200 CFM at 15psi, where as the stock one ran 100CFM at 15psi, the pressure of the intake will remain the same at 15psi, but the amount of air that is passing through will be doubled.
A better example may be a shop vac on blow, can put out more air cfm than an air hose set to 30psi, due to the amount of CFM that can pass through it.[/QUOTE]
I don't think I agree with that statement and it looks to me like you didn't either when you reread it. IMO as long as the opening or duct size is fixed the only way to increase cfm is to increase pressure. I think buddy is on to something with his back pressure idea. I know TD has taqlked about back pressure but either I read it to fast or he didn't carry the thought out all the way.