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 Post subject: Diesel oddities. ..
PostPosted: November 7, 2014, 6:52 pm 
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Joined: April 12, 2010, 5:40 pm
Posts: 2080
Location: san francisco bay area
Here's an odd question for you guys. ..
Does anyone have a service manual for the Nissan SD22 (USDM) with the vacuum driven throttle that was used in the 720?
I'm interested in 1) how they controlled the injection pump and, 2) what correlated rack position to airflow?
And what were they doing with a throttle plate on a diesel?
Did they have a venturi in front of the TP so they could create a ported vacuum signal and then use that signal to drive the rack position?
Hmmmm.......
The only problem I have with the current use of industrial small diesel engines in prototypes is the big puff of smoke when you crack the throttle so. ... I was wondering if I could tweak this to get rid of the heavy cloud at launch and still run a rich mix at hwy speeds.

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 Post subject: Re: Diesel oddities. ..
PostPosted: November 7, 2014, 8:03 pm 
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You answered your own question....

I think it would be easier to eliminate the puff with this design, though I'm not sure why you want to run richer at speed to maximize power.

I don't have a manual, but I'm sure you can down load one.

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 Post subject: Re: Diesel oddities. ..
PostPosted: November 8, 2014, 6:08 am 
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Joined: August 19, 2014, 5:17 pm
Posts: 685
Location: England
Quite a few stationary and old school truck diesels run a throttle butterly . They act as a cheap engine governor for fixed speed running and also reduce the overall noise from the inlet . Open the throttle and the rack in the pump is pulled back by a spring to give max fuel , close the throttle ( vacuum ) and the diaphram will pull the rack back to the fixed speed. With these engines its very hard to stall them because as the engine revs drop so does the vacuum and that in turn opens the pump which resists stall. The only way you are going to reduce the smoke on snap throttle response is to suppress the vacuum signal because as soon as you dump the vacuum you are on max fuel. Some road going early diesels ( merc and Bmc ) ran a throttle butterfly in the inlet to get vacuum for brakes, these used ordinary injector pumps . I know all this shite because I am old. :)

Bob

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 Post subject: Re: Diesel oddities. ..
PostPosted: November 17, 2014, 10:47 pm 
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Joined: June 20, 2010, 6:14 pm
Posts: 94
Location: San Benito TX
I believe that my 1970 Mercedes 220D had a butterfly in the intake.


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