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Nissan diesel engines, and the people who love them
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Post Number:#1  PostPosted: Tue Mar 25, 2008 3:26 pm 
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Car companies 30 years ago used vacuum gauges with different faces as fuel economy minders. I was thinking about how effective one would be on my driving habits and if itll help me drive in a way thats more efficent. Much like Philip and the EGT gauge in his p/u.

Been wanting to fill the 3rd hole in that fancy gauge cluster on my dash with something, and a vacuum gauge is cheap, and I might save a buck in the long run.

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 Post subject: Vacuum gage
Post Number:#2  PostPosted: Thu Mar 27, 2008 9:08 pm 
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I was just thinking of doing the same for an '85 Olds with 307 engine that was given to me recently. It has a 4-speed automatic and I want to see what kind of mileage I can get out of it, even though it's carbed, not fuel injected.
BTW, I wonder if a vacuum gage would work on an EFI vehicle too?
Ray Mac


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Post Number:#3  PostPosted: Fri Mar 28, 2008 2:56 am 
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vac gauge works as you can see the throttle angle V load.

carby and old diesels work fuel ratio from load.

electronic engines dont,but it will still help as it will show that you standing on the throttle and its already loaded.

IE during warm up and cold air temps the efi system may double inject waisting fuel also O2 sencor has a ratio target to allow catalist to work-unless you trick this you not going to change much-an AFR meter will be better and is easy to install.

best way is a trip computor or a data download from the ALD/OBD.

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Post Number:#4  PostPosted: Fri Apr 04, 2008 11:31 pm 
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Get a boosty gauge then add a turbo. :-D

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Post Number:#5  PostPosted: Sat Jun 21, 2008 7:55 pm 
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davehoos--For a while I was not able to access this site (through my own ignorance), so I did not respond to your post right away.
On my Oldsmobile, it's a Thermoquad carb, system is called CCC, apparently a computerised feedback setup that's supposed to be fairly economical, though not as good as fuel injection.
I'm temporarily stuck on the car though. It failed to pass smog inspection because of high NO levels and I'm now trying to figure out the best way to clean it out. I suspect carbon buildup, it was driven only 1500 miles in the last 3 years , mostly without proper warmup.
Ray Mac


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Post Number:#6  PostPosted: Sun Jun 22, 2008 12:09 am 
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High NOx can be running too hot or too lean, too.

If your Olds has the C3 or C4 system, it is indeed old. I think about 1986 or '87 was the last year for that?

I have a tuning tool setup for the Quadrajet C4 as used on an '86 Olds 307, in a ziplock bag here, including a breakout harness I built to connect the dwell meter so that I wouldn't have to pierce the main harness wire to adjust the metering jet cycling frequency.

If your CO and HC are "too good" on your test, you might try adjusting that, to improve your NOx score. Or just replace the cat (I think that used a 3-way cat in those years, but I'm not certain).


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Post Number:#7  PostPosted: Sun Jun 22, 2008 1:27 am 
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Location: Karuah Valley,NSW Australia
the short answer is i dont know.i like to here what you find.

we dont have real emision testing here in australia.we are interested in HC in late model cars the show engine tune condition and CO in pre cataliser 1986 types.

IF the CO is correct-then isnt the mixture correct??

most of my cars show factory rich if car has no EGR valve .
this has been set in the factory design to allow for egr volume entering the engine and then the EGR is deleted for local sales.Ive had problems with datsun L20B/CA20S EGR.these get cloged and upset the carby mixtures setting before it gets going on the main jet proper and fuel use increases,but HC is normal..other types of cars dont make any difference.

high NO indicates hot burn-lean mixture.
could it mean that the exhaust is blocked with carbon??

the old type systems-does it have air injection into the cat--the first bit of the cat needs a rick mixture then you pump air into the cat for the oxidisation bit to hide the HC.

I have a simple [EGO]mixture tester[3 light volt meter] to test O2 sencor operation.that ive found worth every cent,$19- 10+ yrs ago.with engine tune drama it behaves eratic .

i was looking at a 10 light unit recently for $120 and a bought a $75 digital kit that has been too hard for me to make-buy a pre made tested kit.

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Last edited by davehoos on Mon Jun 23, 2008 4:02 am, edited 1 time in total.

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Post Number:#8  PostPosted: Sun Jun 22, 2008 6:51 pm 
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> I will say, regarding my NO levels that it passed at 25 mph and 1254
> RPM, but failed at 15 mph and 1287 RPM. Why, I don't know. HC and CO
> readings are fine.

> Pushing open the EGR valve by hand at idle makes the engine stumble
> but does not stall it, so that may be part of the problem, but I think the
> high combustion temp is mainly being caused by carbon buildup. Seafoam
> maybe will help?

> My Olds is a 1985, the last RWD Delta 88. The 307 continued to be used
> in Cutlasses for several more years.

> My mistake, the carb is an electric Q-Jet, not a TQ, certainly not EFI

Ray, because you get good numbers at the 25 MPH test, but not at the 15 MPH test, there are a couple of things that come to mind.

Spark advance occurs more at the low throttle range: perhaps it's over-advanced (or over-advancing: wrong vacuum diaphragm). Or the TCS (transmission controlled spark advance) system is inactive. I can't recall if your Delta 88 had TCS or not, but when it works it's supposed to kill the vacuum advance until the 200-R4 is in high gear.

More likely, the EGR flow is impeded. This is the dreaded (and common) intake manifold EGR passage plug-up. You can't really just pull the carb and run reamers or wires down the ports, it doesn't work. You have to pull the intake and clean the ports in the heads. And it's heavy (unless you have the cast-aluminum intake, but I don't think the 307 got one (?)).

=============

Years ago, one of my friend Doug's THREE 1986 Buick Estate Wagons was exhibiting very low power and a HUGE stumble off-idle. It had good power up to about 30 MPH, then tapered off and had major problems getting up hills.

The problem was a melted-down & plugged catalytic converter. The high exhaust pressure from the plugged cat was overwhelming the EGR valve and as soon as you tipped in to the EGR port on the carb's throttle body, and a vacuum signal was sent to the EGR valve to open, WHAM . . . a huge squirt of exhaust would go in the intake, and the car would fall on its face. One learned not to dwell in that part of the throttle's range!

The cat had been installed a year before by a muffler shop, to get the Wagon to pass Oregon emissions testing (which it did). It was a dinky, too-small cat. We successfully got the muffler shop to warranty the cat: problem solved.

============

On the SeaFoam: lots of people swear by it, but I've never gotten SeaFoam to make much difference. Mopar included a can of some intake/combustion aerosol cleaner with a kit they provide to fix a common problem where some Mopar V8s with plastic intake manifolds experience a backfire and crack the intake -- on the bottom, so you get phantom oil consumption because the intake sucks the oil from the lifter galley.

Because all that lube oil burning carbons up the piston crowns, valves, and combustion chamber, Mopar's fix kit includes the cleaner. It smells exactly like aerosol paint stripper!

I've heard good things (in the Onan forum of SmokStak.com), that Onan's aerosol Combustion Chamber & Carburetor Cleaner ("C4") works well for carboned-up Onan gensets. I bought four cans of the stuff last year but haven't had a chance to try it out on anything.

Link to Cummins/Onan blurb:
Onan wrote:
4/C Combustion Chamber and Carburetor Cleaner
#326-5278 Our Price: $6.00

Removes power-robbing buildup of carbon, gum, and varnish. Regular use can extend intervals between combustion chamber carbon maintenance cleanings. 12-oz aerosol can provides carbon removal for one genset.


I paid more than $6 per can, because I was buying Onan parts from some other place and just happened to see that they sold the 4/C stuff too.


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Post Number:#9  PostPosted: Mon Jun 23, 2008 3:45 am 
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question ?
the test is done on a rolling road?
and at different speeds?or simple tune up/dyno type test.

the only test like this ive done is the operator followed instructions on a display to speed UP or Down and the computor did the rest.it was for an engineers test on an import car using a bag test.measured using the the room average per KM not the exhaust pipe emision.

I would expect the egr to stall the engine if the passage was good.

around hear the passage normally clogs up with a crystal like substance that expands and cracks the alloy housings.since ethanol blend has been released cloged pipes with soot is common.

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Post Number:#10  PostPosted: Thu Jun 26, 2008 6:40 pm 
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Looks like I can at lest for the moment access this thread again after many failed attempts ( I followed Al's advice to do it).
California emissions testing ( also known as smog testing) is required every 2 years for older vehicles and on the sale of the vehicle. It is done on a dynomometer.
I hate to think a clogged converter might be the problem, which is why I thought of trying a cleaner first. And, since manually opening the EGR valve at idle does not stall the engine entirely, that may be an indication that trying to get rid of carbon might work.
The intake is aluminum.

Ray Mac.


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Post Number:#11  PostPosted: Thu Jun 26, 2008 6:44 pm 
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The carbon you need remove is within the exhaust passage between the exhaust valve port and the EGR valve; it can't be done effectively without removing the intake manifold.


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Post Number:#12  PostPosted: Thu Jun 26, 2008 6:52 pm 
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OK, thanks Al.
Ray Mac


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Post Number:#13  PostPosted: Mon Jul 20, 2009 11:27 am 
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Thought I would try and take this thread somewhat back on topic, rather than start a new one. But I am going to pose a slightly different question, than the OP.

I found this site:

http://www.fordf150.net/howto/diagnoseengine.php

Which has an excellent write up on using a vacuum gauge for diagnostics purposes. The only problem is it was written for gas engines, not diesels.

Has any one ever seen, or have a similar list for diesel engines?

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Post Number:#14  PostPosted: Tue Jul 21, 2009 10:11 pm 
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Diesel engines don't use vacuum to any degree. Vacuum as a one-test-does-all is peculiar to gas engines.

Right off I don't think of any single _easy_ measurement available for diesel that covers the territory.

Rufus

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