Headers

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

Moderators: plenzen, glenlloyd, goglio704, Nissan_Ranger

Post Reply
windsock
Posts: 144
Joined: 15 years ago

Headers

#1

Post by windsock »

G'day all,

Has anyone played around with a decent set of headers on these engines? I realise there is the turbo option for breathing and power but I have persued the KISS design principle pedantically with the build of this land rover and I see retro-fitting a turbo as adding a layer of complexity. Necessary or otherwise.

I see headers as a far simpler option but I have yet to find any anecdotal evidence to indicate the kind of power increases I might expect.

I am just wondering whether anyone has either built headers or bought some to install and found tangible results.

Note: I already have a very clean and custom exhaust system from the factory manifold. I had a system bent up out of 2.5inch with an extended 2-1 collector built for the cast manifold. So, if I was to build either a set of headers or turbo it, I can easily adapt into a good free flowing exhaust system. I can feel the difference this bigger diameter and free-flow collector has had.

Cheers,

Phil
Good roads lead to bad fishing.
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#2

Post by rlaggren »

Might see if the link in the first post works for you. I just checked it and all I got is a blank screen; however, their homepage search brings up the exact same link to the article so I'm thinking my browser in screwing the pooch somehow. The article is a pretty good run down on the theory of gasser extraction.

http://nissandiesel.dyndns.org/viewtopi ... ht=exhaust

What I got from the article is that extraction does make a difference and the most critical item is the length of the pipe just aft the collector. The LD28 maxima came with a "resonator" about 18" behind the collector which _may_ have acted as a "big open space" which terminated the length of the tuned exhaust. Ie. the resonator created in effect an open pipe at that point which is one of the most important ways to control the tuning. IAC I'm running with a straight pipe there now and id doesn't seem to have affected the noise level much so I'm thinking the resonator was there for some other reason...

Cheer.


Rufus
82 Maxima wagon
windsock
Posts: 144
Joined: 15 years ago

#3

Post by windsock »

Hey thanks Rufus,

I re-read that the other day and indeed, it has some good info in it. I have sort of figured that I need to get a bit more technical than I have and actually learn some new stuff so I am getting to grips with a lot of interweb info. Seems to be agreeance on the tuning of that length of pipe after the collector as you say. Seems also to be some contradictory stuff out there so I have to put a BS filter in and maybe learn some stuff to be able to figure it out.

A distinct shortage of info on diesels and inline sixes. Some of the old chevy sixes in the interweb has some interesting stuff. Again, a case of [BS filter on] ?? [/BS filter on].

I can kinda see what I'd like to build within the confines of the space I have and it may include an option of a section whereby I can add or subtract 'length' to the aforementioned section to see what difference it all makes.

Has anyone 'mapped' the angles of the LD camshaft? Maybe I need to get the spare head out onto the bench with a protractor :shock:

Cheers,

Phil
Good roads lead to bad fishing.
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#4

Post by rlaggren »

> protractor...

When I was building engines (just hobby stuff), I got a 10" disk called a "degree wheel" - it was a full 360D protractor that you bolted onto the front of the crank to make it easier to see where you were, sorta speak.

Rufus
82 Maxima wagon
User avatar
Dslsmoke
Posts: 33
Joined: 18 years ago
Location: Hialeah Fla.

Headers

#5

Post by Dslsmoke »

Very interesting subject!!!!

Let me throw a bone your way, there is (was) a big following with the Z gasser engines of the time L24, L28, Perhaps looking into their doings might give some insite :?: :?: :?: :?:
windsock
Posts: 144
Joined: 15 years ago

#6

Post by windsock »

rlaggren wrote:> protractor...

When I was building engines (just hobby stuff), I got a 10" disk called a "degree wheel" - it was a full 360D protractor that you bolted onto the front of the crank to make it easier to see where you were, sorta speak.

Rufus
Hi Rufus, yes, I too have seen degree wheels in use but have yet to have that geometric 'confusion' myself... I found and downloaded a degree wheel 'picture' in jpeg form so will maybe print it out and glue to some sheet alloy I have here for a DIY effort.

Seems like I need to locate Bottom Dead Centre of the exhaust stroke start and map it from there. This should be interesting given the IDI nature of these heads. I am not going to be able to locate the piston position the usual way.

Thankfully, I have a spare engine on the engine stand so I can take the sump off and locate bdc based on actual piston position from the bottom up. :wink:

Hey Dslsmoke, I figured you were pointing me to the Hybridz site. Checked that but not a lot on offer other than the usual LD crank requests and discussions. I'll keep googling around and see what I can find though.

Cheers guys, this is going to be a slow project with work the way it is at the moment - still part time. :roll:

Phil
Good roads lead to bad fishing.
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#7

Post by rlaggren »

> work...

That's the way of it. Lotsa work = no time. Lotsa time = no cash
82 Maxima wagon
windsock
Posts: 144
Joined: 15 years ago

#8

Post by windsock »

OK, finally got around to putting the degree wheel to the cam of a spare engine today. No surprises really.

Started at TDC on compression stroke on cylinder 1; set exhaust and inlet clearances to those required for a hot engine as set in the manual, i.e. 0.25 & 0.30mm. Had difficulty getting the dial guage in at a good angle to the valve so I did multiple runs at a strange angle to be certain I had a better than approximate reading after it all (so, caveat emptor).

By my reckoning:

Exhaust opens = 115 deg ATDC
Exhaust closes = 15 deg ATDC
Inlet opens = 355 deg ATDC
Inlet closes = 240 deg ATDC

Exhaust duration = 260 deg
Inlet duration 245 deg
Overlap = 20 deg.

Still cannot find a definitive formula for an inline 6 cylinder diesel for primary and secondary pipe lengths so am going to order a book i have seen several references to:

Smith, P.H. & Morrison , J.C. (1972). Scientific Design of Exhaust & Intake Systems (Engineering and Performance). 3rd Edition. Bentley Publishing. ISBN-10 0837603099.

A bit dated but then so is our engine :lol: so it should do just fine I think... any other suggested readings gladly considered...

If the aforementioned reading settles my curiosity and I can fit the recommended lengths of primary and secondary tube into the space I have, a couple of pay checks from now I should have the material needed to start tacking tube together... it'll be either a tuned header or a turbo manifold :wink:
Good roads lead to bad fishing.
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#9

Post by rlaggren »

Might consider looking up the author and trying a message regarding his opinion whether his book is applicable to diesels. If you find him it might elicit some interesting info. Ditto any other books/authors which don't explicitly cover diesels.

Cheers, Rufus
82 Maxima wagon
windsock
Posts: 144
Joined: 15 years ago

#10

Post by windsock »

Hi Rufus,

Thanks :idea: , I hadn't thought of trying to find/contact the author directly, smart idea. At least one of them, Dr John Morrison was at a University at one stage so it may well still be a publicly accessible email.

I have thought long about the potential difference between the otto and diesel cycles as far as exhaust and intake durations and headers. The only difference between them is the ignition part (as far as I can interpret), and each of the exhaust and intake cycles could still benefit from free breathing in my limited knowledge and comprehension of the topic. I am not a physicist nor am I a mechanic so I could be thinking awry here.

Anyway, back to thinking... :wink:
Good roads lead to bad fishing.
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#11

Post by rlaggren »

When you put it that way, it kinda makes sense. I wonder if there is a break over point, either rpm or overlap or some combination where tuning the exhaust pipes really starts to make a difference?

As I recall the momentum of the exhaust gasses is what makes tuning work. More speed or more mass (of the exhaust gas) would mean more extraction.

If I had to speculate on possible differences: There might be differences in mass (of diesel exhaust) and in the flame front velocity for diesel (which could effect the speed of the exhaust gas).

But you know, most of the numbers come from cut 'n try, not theory. The whole exhaust system "science" seems to be mostly about trying it to see if it works. IOW, a lot of work.

I wonder if you might find info on sites about tractor pulls? One of the few places I can think of where they might do real testing on diesel mods. Assuming, that is, there are classes where the motor has to be naturally aspirated.

Cheers, Rufus
82 Maxima wagon
DMS
Posts: 117
Joined: 17 years ago
Location: Prunedale Ca. 93907
Contact:

#12

Post by DMS »

windsock wrote:OK, finally got around to putting the degree wheel to the cam of a spare engine today. No surprises really.

Started at TDC on compression stroke on cylinder 1; set exhaust and inlet clearances to those required for a hot engine as set in the manual, i.e. 0.25 & 0.30mm. Had difficulty getting the dial guage in at a good angle to the valve so I did multiple runs at a strange angle to be certain I had a better than approximate reading after it all (so, caveat emptor).

By my reckoning:

Exhaust opens = 115 deg ATDC
Exhaust closes = 15 deg ATDC
Inlet opens = 355 deg ATDC
Inlet closes = 240 deg ATDC

Exhaust duration = 260 deg
Inlet duration 245 deg
Overlap = 20 deg.

Still cannot find a definitive formula for an inline 6 cylinder diesel for primary and secondary pipe lengths so am going to order a book i have seen several references to:

Smith, P.H. & Morrison , J.C. (1972). Scientific Design of Exhaust & Intake Systems (Engineering and Performance). 3rd Edition. Bentley Publishing. ISBN-10 0837603099.

A bit dated but then so is our engine :lol: so it should do just fine I think... any other suggested readings gladly considered...

If the aforementioned reading settles my curiosity and I can fit the recommended lengths of primary and secondary tube into the space I have, a couple of pay checks from now I should have the material needed to start tacking tube together... it'll be either a tuned header or a turbo manifold :wink:

I believe Rufus is right about the "cut 'n try" method for the most part.

I think you will find Diesel inline 6's to be different than gassers as far as exhaust systems go. Diesel is quite a different beast in the exhaust flow area. Your on a good track making your own cam card. That will significantly help you. At least with the lower RPM range of the diesel you can focus your efforts on a smaller RPM range when building your exhaust. That is to say that your not trying to keep it drivable for all 7-8K rpms that the gas variant has.

You may not want to focus on inline 6 exhaust so much as get a basic understanding of exhaust systems. Make you own conclusions. Read up on different dragster and race car exhaust system designs. They fine tune everything its insane.

Your next step may be flow testing the diesel head and determining you volumetric efficiency... which I have yet to figure out for the LD... If you figure out how to get VE for the LD28 please post back... VE would help determine header tube size and much more(and more so for forced induction goers).
Ray
Cmdr. Ron
Posts: 23
Joined: 13 years ago
Location: Middleburg, Fla., U.S. of A.

#13

Post by Cmdr. Ron »

GREETINGS!

Did you fellas ever get any data on Diesel Volumetric Efficiency?
While you were specifically after 6 cyl LD data, any that can be applied or adapted to other diesels would help us all heaps. Earthlings are typically resistant to changes - it's a comfort zone thing. Improvement to something they don't grasp already is way beyond them. Such is the case of Diesel improvements - especially non-factory stuff.
I saw a thread wherein a man built an SD22 Turbo Exhaust Manifold using Black Iron Pipe (typically referred to as "BIP"). His was far too short for N-Asp.
I figgered to use approximate length for a gasser with primary pipe the same as exhaust port (1.5"), since such data is not readily available for diesels & I haven't learned how to calculate it, yet.
As it happens, I have a similar prototype to do for my Fiat Spider 2.0L.
Any input from the more learned is appreciated.
Thanks
'82 DATSUN 720 SD22, '77 Fiat 124 Spider, '81 Toyota HiLux, '64 Chevy Corvair Monza
The Blessing of Abraham is mine!
rlaggren
Posts: 541
Joined: 17 years ago
Location: San Francisco

#14

Post by rlaggren »

I recall there's a bunch of info on the L28 Datsun 240 and up because people love to turbo the car. Google around a few hours for turbo and 240 or something. I found detailed curves and analysis for that engine and I suspect at the low end the LD28 is very similar. At least a place to start and make a short list of turbos (probably small to favor the low end) and controls you need. Anything like this has got to be viewed as a noble experiment which means there will be some cut and try. One fellow here has put together a pretty good install in a Z car so there's some info there.

IMHO the easiest way to turbo the LD28 might be with a J-pipe. Search this site. You use the existing manifold with minimal mods and need to fabricate (or buy as our member did) a J-pipe to fit your car; then fab the exhaust from the turbo back to where ever, again to fit your car. That gets you basic boost and may be all you need. If you want fuel, you need an IP with an aneroid on top to start fabbing your controls; I don't know of anybody that's done that here but have heard there are some out there. From what I've read, this engine will except a mild turbo with good results; anything beyond "mild" doesn't have good reports at this time.

Rufus
82 Maxima wagon
Post Reply

Who is online

Users browsing this forum: Ahrefs [Bot] and 3 guests