NissanDiesel Forums

What is the redline on these motors? And what rpm would it be pulling at 75? i've found myself at the speed for quite awhile and I know it's not good but at what rpm is the motor running?

It's really a pain in the ass that these trucks don't come with a tach, or an easy way to install one, gassers have it easy when it comes to that

oak4000 wrote:. . . these trucks don't come with a tach, or an easy way to install one . . .

Is $65 cheap enough for a diesel tach? Looks pretty darned easy to install, too.

oak4000 wrote:what is the redline on these motors? and what rpm would it be pulling at 75? i've found myself at the speed for quite awhile and i know it's not good but at what rpm is the motor running, SNIP

HP - Torque Chart

Assuming a 2WD truck with 185/75x14 tires, 60mph is 2500 rpm while 80mph close to 4,000 rpm.

RPM-SPEED Chart

Max torque is over the 1900-2400 rpm span. Diesels' "maximun continuous rpm" is typically no more than max torque rpm and sometimes a little less.

The 720 diesel trucks were imported to North Amerisa in response to the gasoline shortages, public demand for fuel economy, and geared for the national speed limit of 55mph. Such is not the world today but that does not change the truck so ... just stay over in the truck lanes. Your MPG and oil consumption will be best at these lower speeds.

Sure, you could buy/build Roger's box and roll your own tach. In fact, Carimbo, this is what you've been asking about for the last year: a way to use the OEM Maxima gasser analog tach -- only not using the EGR pickup. Though, thinking about it, I bet the EGR tach pickup could be used anyway I'd want to 'scope the EGR tach sensor signal to see what it looks like, but I don't see any reason it couldn't be used.

Gotta love 555s!

But for bolt-on simplicity, the TinyTach is hard to beat. No fabrication.

Al: TWICE on this thread I have clicked on "quote" with result being "edit" which results in a loss of the post I'm replying to.

Also, I find the "URL" button no longer functions. All that happens is a reset to the edit screen. Makes me manualy enter the http and title text.

-Philip (I'm using IE 7.0 now)
+++++++++++++

To: "moose60"

In the process of editing a post of my own, I accidentally deleted your recent post to "I want a tachometer." Please accept my apology to you. It was not intentional


Electronic RPM counters all need a pulse generator of some sort. The problem to address is: how to trigger the tachometer on an ignitionless engine.

The Tiny-Tach solution is an externally powered piezo clamp located on an injecter line of your choice. On Nissan's marine applications, a mechanical signal generator is mounted to the injection pump drive gear.

asavage wrote:Sure, you could buy/build Roger's box and roll your own tach. In fact, Carimbo, this is what you've been asking about for the last year: a way to use the OEM Maxima gasser analog tach -- only not using the EGR pickup.

Sorry, wasn't following. What is Roger's box? Now that I've got the whole dash out could be a good time to route a few extra wires there for a later tach addition.

Carimbo wrote:

asavage wrote:Sure, you could buy/build Roger's box . . .

Sorry, wasn't following. What is Roger's box?

Philip's having some (M$ browser, I suspect) trouble and wiped Moose60's post, but the essence is that Moose60 posted a link to a do-it-yourself (and kit form) add-a-tach to VW diesel. Dredged from my browser's History file:

http://www.4crawler.com/Diesel/CheapTri ... ndex.shtml

Philip-
It's no problem, just a little confusing. Good luck.

I ran across this on a diesel motorbike enthusiast site http://www.dieselbike.net/phpBB-2.0.21/ ... c.php?t=67 where they are discussing tachs.

How about using a cheap cycle computer - available for under a tenner.

Set it to read in KMH and the wheel circumference to 1667 mm and it should display engine speed x100 rpm - so 36 kph = 3600 rpm.

Use a small strong magnet close to the centre of the flywheel to keep the 'pass by speed' slow enough for the sensor to pick up. A blob of epoxy should hold it in place.

Regards
Dave
(Bodgit & Scarper Engineering inc)

The site is mainly British. These things should be $20ish based on my experience.

I calculate that a wheel circumference of 10.59 inches will be pretty accurate if you get one that likes US measures, but I think they all will do both. I was mostly curious about the math used to get the desired wheel circumference.
I used (circumference in inches) X RPM (1000 cause it's easy)=distance traveled in one minute in inches. Divide by 12 to get feet, divide by 5280 to get distance traveled in miles. Because the thing will read in units per hour and we want units per minute (rpm) I multiplied by 60 at this point to get 10.026 MPH, which a driver could read as 10 X 100 RPM.

If I convert 10.59" to MM I only get 254mm though... which doesn't seem to match up with the 1667 mm figure. Even accounting for the fact that he is working in KPH I don't get it.

Help?

I've got a couple gasser tachs from the jy. Thinking it shouldn't be a problem to convert. The guy at Cheap Tricks responded with a short, "I'm not familiar with that tach," when I asked to buy his custom parts kit. So I was looking for anyone who can scope the gasser input and "Chilis84isdying" from the MSN board sends me this, supposedly from the SD25 720:


Anyone have any comment? Have we been going the long way around?

Still, if anyone can scope that gasser input signal it might be cheaper to make the adapter myself than buy Nissan. I'm off to the dealership to investigate!

Your scan page IS for the SD25 720 trucks (1984+). I have yet to -see- a 1984+ truck with diesel (neither had tachometer) but then ... I've only seen 2 personally.

The SD22 720 never had an optional tachmeter.

There are a many harnass differences comparing the SD25 vs SD22. There must be a "reluctor" (my term) but ... the FSM gives no specific clue.

philip wrote:The SD22 720 never had an optional tachmeter.

That's what I always thought. Now I can verify it. But from the way everyone has lamented the lack of a tach and entertained every other scheme, I was quite certain that was the case with all diesel 720s. I am surprised to find that it was in fact an option on the later 720s with the SD25.

In all practicality it doesn't make any difference because, 1.) the tach, which does have a different part number than the Z tach, is $217 (the gas one is $229). Moot, because it is not available anywhere, at all. 2.) The sensor (pn 25068) is about $60. Rush to your dealer now, because there is one somewhere in the US. 3.) I can't imagine finding a 720 w/ SD25 in a junkyard, so I'm back where I started.

For motorheads, I did get a breakdown of where the sensor fit. Looks like it reads the cam gear, which I suppose has an inset on it. If anyone has one of these trucks, you have a jewel of high interest!



So I still need for someone to scope a Z gasser. Maybe I'll experiment with my Sentra.

Knucklehead wrote:

philip wrote: I am surprised to find that it was in fact an option on the later 720s with the SD25.

I've had this photo for almost 2yrs ... I didn't know what THESE bases could be for!

Knucklehead wrote:I am surprised to find that it was in fact an option on the later 720s with the SD25.

I've had this photo for almost 2yrs ... I didn't know what THESE bases could be for! You get one base machined and an extra for ... ?

http://www.autometer.com/search_results.aspx?q=diesel

hope this might help