Those serious about turbocharging should read this!

Discuss (and cuss) the Nissan LD-series OHC Six diesel engine, popularly available in the US in 1981-83 Datsun/Nissan Maxima Sedans & Wagons.

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ChrisQ
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Those serious about turbocharging should read this!

#1

Post by ChrisQ »

I remember we had a thread on here about turbocharging,and some were afraid to do it, because of leaning out and melting the pistons.

You need to read this and pay very close attention to the section on anaroids!
here is the link
http://www.bomzhan.com/2007/09/07/turbo ... and-facts/


Then you will know why you can add that turbo and turn up the boost!

ChrisQ
2 1982 maximas. One is a nice driver.
other is for converting jeep camanche pickup to diesel!
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asavage
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#2

Post by asavage »

While I enjoy a good read on turbocharging as much as the next person, I almost always seem to find these little annoying problems with most technical writing, and for some reason feel compelled to try to correct disinformation.

"Myth- The engine will run a much lower engine temperature if it is Intercooled.
Fact- A diesel engine compresses the cylinder air charge to approx. 500PSI. This is done as the air needs to be red hot . . .
"

Air . . . red hot? No. We are not ionizing air in a diesel.

"Boost pressures used in turbo charging are relatively low and don’t generate much heat if any."

BS. Depending upon the boost level, Charge Air Temperature (CAT) rise (before and after a turbo) can be as much as . . . well, I can't get Google to give me a "good" reference, but I recall that 15 PSI boost can run the CAT up over 100°F over ambient.. That is not an insignificant temperature delta.

If the intake CAT is 100°F higher, so will be the EGT (within, say, 10%). Higher EGTs are Not Good, BTW.

What else?

"Myth- Particular companies don’t increase the engine output too much, when turbo charging, so as to keep long engine life."

He then goes on to say that his older turbo additions run lots of kms, and maybe they run cleaner with a turbo. This doesn't have anything to do with the "Myth". We know that OEMs keep the boost (and torque) to a certain level when more is available, and the reason we know this is because of the flourishing aftermarket for controller chip upgrades/updates (Bully Dog comes to mind first). Those chips alter boost parameters and timing from the OEM map to give more power. There is always a downside, whether increased pollutant emissions, torque delivery above the drivetrain's end-of-life rating, bumping EGT redline higher, etc.

I would rate Mr. Leimroth's "Fact" section on this topic as specious.

"Myth- You must fit a Fuel pump aneroid (fuel compensator) when you fit a turbo as it will run better and give you more power."

The points he makes are:
a) Adding an IP boost compensator (aneroid) is expensive,
b) An aneroid is an emission control device!
c) An aneroid can be misused.

Where to begin?!
Without a boost compensation device, your choices for fuelling when adding a turbo to an NA diesel are:

1) Do no fuel system changes. The existing fueling level is maintained, power does not increase a great deal, EGT goes lower, particulate matter (PM: soot: black smoke) level is the same or lower. More air is available to oxidize (burn) the same fuel as before. Sometimes this gives better power, even though more fuel is not there to burn than before.

2) Increase fueling level, usually but allowing the IP to inject more fuel at its maximum rack setting (Inline style) or control sleeve setting (VE-style). Maximum power is increased because there is more fuel available and more air available -- when boost is up. EGT will go higher when more power is being generated; EGT may go down during other driving conditions. PM is almost always increased because most people cannot resist pushing the accel further than is wise under all conditions: the engine will not always have enough air (enough boost up) to oxidize the additional fuel that the "turned up" IP is providing, esp. at low RPM.

A boost compensation device (aneroid) can sense if boost is up, and allow more fuel to be injected (when demanded by the driver) only if there is enough air available -- boost -- to burn the fuel. That's all an aneroid does.

Having said that -- some VE-style IPs have an altitude compensation aneroid built into the governor cover on top (Nissan, Volvo, Toyota, etc.), and some Inline IPs have an external fuel limiter altitude compensation aneroid (Nissan, MB). This is a kind of automatically-adjusting smokescrew which limits maximum fueling in high-altitude conditions where the air is less dense and therefore contains less oxidizer. This aneroid does the same thing as on a turbocharged engine, except it is not plumbed to read boost pressure (actually, it isn't designed for boost-level pressures). Confused yet?

This is a good place to stop for now. But bear in mind that it is unwise to look at one person's writings and assume that her viewpoint is 100% congruent with our consensus reality.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.
glenlloyd
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#3

Post by glenlloyd »

I found the article somewhat perplexing and...well...fuzzy. That part about the aneroid was rather poor, and I think its credibility went down the porcelain fixture with the reference about it being a polution control device.

Since he's installed "thousands of turbos" it would be interesting to know exactly how many of those are still running.

steve a
97 Jetta TDI, 86 VW Golf D
89 VW Fox diesel, 92 MB 300SD W140

gir - won't the sploding hurt?
zim - silence!
ChrisQ
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#4

Post by ChrisQ »

Sheessh i thought that the article was a riot!!

ChrisQ
2 1982 maximas. One is a nice driver.
other is for converting jeep camanche pickup to diesel!
ChrisQ
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Location: centralia washington

#5

Post by ChrisQ »

Sheessh i thought that the article was a riot!!

ChrisQ
2 1982 maximas. One is a nice driver.
other is for converting jeep camanche pickup to diesel!
davehoos
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#6

Post by davehoos »

we have several good diesel service centers around this area and several turbo installers that i trust.hunter valley-northern NSW.

there are many owners that travel to the area in southern NSW that this author has his buisness and use several companies including the one named based in this area.i see the service stickers regularly.including local 4X4 owners clubs.

i had another paragraph but decided to self sencor.

in that part of OZ intercoolers are not needed on most Patrol/Landcruiser/Hilux vehicles.the type of use they will get in this area is a lot different to western NSW.The conversions often get a oil heat exchanger or full flow oil cooler and that about it.large water cooled turbos are popular.
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philip
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#7

Post by philip »

asavage wrote:While I enjoy a good read on turbocharging as much as the next person, I almost always seem to find these little annoying problems with most technical writing, and for some reason feel compelled to try to correct disinformation.
hahaha. Me too.

But all that smoke on 1/4 mile drags is fun to watch.
-Philip
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My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"
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philip
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#8

Post by philip »

glenlloyd wrote:Since he's installed "thousands of turbos" it would be interesting to know exactly how many of those are still running.

steve a
Diesel owners blow up whatever they'll pay for fun. Leimroth makes money while sounding experienced.

"Tech Sheet ‘Turbo Myths and Facts’ by Andrew Leimroth (Andrew Leimroth of Berrima Diesel Service is one of “The Diesel Experts” see http://www.thedieselexperts.com and has personally fitted on average 2 or 3 turbos a week for the past 10 years. That’s thousands of tubos. Berrima Diesel Service are Australia’s Leading Diesel Service Centre..."

Figuring 2 turbo installs per week, times 48 week a year, for 10 years. Ok, estimate him for 1,000 installs. So "thousands" must include other mechanics at Berrima installing or mailing? Hahhaha :wink:
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"
davehoos
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#9

Post by davehoos »

aneroid these are rare on older australian diesels.the westward hyway crossing the local mountian range on the east coast is a massive 670 meters above sea level with most of OZ being level ground.air temps south of the sydney/adelaide line are moderate.

most commonly converted diesels have VE pumps.

its rare for aftermarket turbo to fit boost compensators.this is done on the basis that you lift off the throttle when the smoke comes out and its expensive to do properly.most drivers are taught to squeeze the throttle and wait till the engine catches up.

until now there was no emision require ments except visual smoke.until recently road side testing was unusual.there is no testing for emisions in australia other than if you are a naughty boy and get defected.it is then your problem to clear the defect.

I was suprised to read the artical.
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Knucklehead
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#10

Post by Knucklehead »

Aside from the exessively brief answers the guy is correct, but I have one point of contention and one point of clarification:

1) Custom manifolds - Very little about fitting a turbo is common sense, and very much of it is counterintuitive. There is no room for Rationalism in this game, it's all about building it and collecting data. As Hume said, there is no way Adam could have known just by looking at water that it could drown him. Show me the data because I've been looking for it and haven't seen it yet. At least not at boost levels under 30 lbs. The best setup I have seen is the one Bacho used with a stock manifold.

2) Intercooling temperatures - This is the bad technical writing that Al referred to. Having an intercooler won't make a noticeable difference in how your engine temperature gauge runs, but I don't know anyone who claims that is what an intercooler is supposed to do anyway. All it does is condense the air charge so that the turbo can pack more air in. More air/fuel means more power which requires greater cooling capacity. What's the question?

Some of those numbers Al was looking for - 15 lbs boost will raise the charge temperature from 80°F to 200° minimum; that is with a turbo of 100% efficiency, which doesn't exist. 70% efficiency will get you up to 250°. The addition of an intercooler of 70% efficiency will drop that to about 130°, which on a theoretical SD22 will increase bhp from 93 to 110, certainly not insignificant. In naturally aspirated trim we (SD22) will get about 1 hp increase for every 10° drop in ambient temperature.
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#11

Post by davehoos »

but I don't know anyone who claims that is what an intercooler is supposed to do anyway. All it does is condense the air charge so that the turbo can pack more air in. More air/fuel means more power which requires greater cooling capacity
the common claim here is that the intercooler[all types] is about reliability[piston temp] not increasing the density of air charge or horse power.some depend on oil cooling of internal parts and water for external parts.

having a discusion about compression ratio the other day with an engine tuner,he hit me with terminoligy squish and quench and a few others.
at certian times during the combustion portions of the mixture will not burn,some will not burn at all and flows into the exhauste.discusions about increases of compression always reverted back to engine destruction.

most of the conversion i see are one offs.in the 80-90's fit yourself kits was common.now kits have to be certified /aproved these kits have disappeared and being replaced wit bolt on spare parts.

PS unrelated.a news item over this week that fuel volitility levels in NSW are to be modified to bring it inline with fuel used in smog areas around the world.
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philip
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#12

Post by philip »

Knucklehead wrote: 2) Intercooling temperatures - This is the bad technical writing that Al referred to. Having an intercooler won't make a noticeable difference in how your engine temperature gauge runs, but I don't know anyone who claims that is what an intercooler is supposed to do anyway. All it does is condense the air charge so that the turbo can pack more air in. More air/fuel means more power which requires greater cooling capacity. What's the question?

Some of those numbers Al was looking for - 15 lbs boost will raise the charge temperature from 80°F to 200° minimum; that is with a turbo of 100% efficiency, which doesn't exist. 70% efficiency will get you up to 250°. The addition of an intercooler of 70% efficiency will drop that to about 130°, which on a theoretical SD22 will increase bhp from 93 to 110, certainly not insignificant. In naturally aspirated trim we (SD22) will get about 1 hp increase for every 10° drop in ambient temperature.
"It is better to be thought a fool, than to open your mouth and remove all doubt". I'll take this chance.

Let us say the following, assuming natural atmosphere:

1. A VE type injection pump. :wink:
2. During engine operation, the RPM limits at maximum torque. (dyno roller)
3. Ambient air temperature: 60 degrees F.
4. No aneroid. (and per DaveHoos, no "boost compensator")

Now ... let's change -only- ... pressurized air charge ... from natural atmosphere to 15 psi. :wink:

What should be the reaction? RPM rises? RPM remains? RPM drops? Pyrometer expectations?
Last edited by philip 13 years ago, edited 1 time in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"
davehoos
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#13

Post by davehoos »

aneroid-
i call this an altitude compensator,its normally vented to atmosphere[ive seen some vented to the air cleaner].so turbo woulld have no effect.pressureising this with boost pressure would probably have no effect unless you can adjust the pump to think its at high altitude at rest.

at sea level do they add or delete fuel :?:
a gas engine needs to add fuel.

boost compensator [over simplified]
reduces the throttle travel when there is lower boost levels.a moving stop contact moves against the fulcrum point.this does not stop maximum fuel but changes the curve.

fuel quality lever.
my RD28 has a lever on the side of the top cover.it is an adjustment for fuel quality that acts inside as a boost compensator but is fixed.there is instruction to manually lift the lever for starting in crap weather conditions.


During engine operation, the RPM limits at maximum torque. (dyno roller)
most of the dyno i used you can set load or speed.
if its load the RPM will rise,the idea is that you find the new rpm speed that maximum is now at.
if its speed then the output number go up [hopefully].

if its one of those machines that give horse power then its anyone guess. :) tourque X RPM.

piro expectation. horse power increases only come from increased heat.i hope that the heat is transfered out the back.with a tubo you need hot gasses to turn the turbo but after that you dont want heat unless you burning urea for a cataliser.

i saw an article about landrover 90 in UK.these had a small NA diesel with a factory turbo option.the NA was hopless at towing but it was found that the turbo needed an intercooler for relability.factory inter cooler was next to the radiator about 12 inch wide[aprox].after market intercooler was the size of the radiator area.
road test showed that with the larger intercooler that air temps on a run towing a caravan was the same as no intercooler not towing.in fact that air temps reached ambient in some conditions.
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#14

Post by davehoos »

air density is not an issue.
the air is hot because it being squeazed back into a smaller area.
the hotter you get the more boost you need.more boost more heat.

turbo was originally call altitude compensators.a term common used in australia when i was a kid as turbo was a dirty name.due to relability and insurance costs.this term goes back to the superchargers on aircraft and manualy adjusting boost for altitude.
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philip
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#15

Post by philip »

davehoos wrote:SNIP- aneroid -SNIP-

boost compensator [over simplified]
Now ... what was my question?

(theorize)
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"
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