TOPIC: Nissan 1400 LDV Change from standard carb to 36 weber DCD

Thank you Greg.......

Yo, Martin. For RVS, here on the front page, click the fuel savers tab. Ron put RVS in that section.

Wow, that's one way to adapt the Weber to this manifold! I used an aluminum adapter on the Subie, a 2 piece one came with my Weber. I instead used another one, a 1 piece style. My adapter added about 1/2" height under the carb, increasing the plenum volume under the carb. Looks like you took a block of aluminum, and bored the 2 holes, and the stud holes, then welded/epoxied it in place. The stock one had the PCV valve on outboard side of the plenum, I don't see the PCV in the modded setup?. That's ONE way to do a PCV mod!
I've never even considered anything like this, a big no-no smog wise here! But allowable for you guys. Correct me if I'm wrong. But wow that was a lot of work to get the Weber on this intake! I guess I just take ready availability of cool parts for granted, and I have Summit Racing right here in town too! (Spoiled) SA is a LONG way from anyplace, parts are scarce, so you guys have to take matters into your own hands a lot, I'm thinking...

I expect a serious power increase to this cool little truck now. The increased plenum volume under the carb should boost mid range and top end power. With a stock carb, it could hurt off idle response, as velocity of incoming air/fuel charge will slow some. BUT- the Weber is a wonderful carb, ultra tuneable, and has a very sensitive idle circuit. Jetting will likely need sorting out. I'd have a look at the exhaust system to be sure there are no restrictions, 'cause the induction side is gonna open up and say AAHH!! This little Beastie will certainly be well-fed!

Of course results on your careful Peach Test aren't Real World, but this gives an idea of the potential.
Might consider the tire press. trick, if the tires and steering are OK, hey it's a Freebie! ANY-thing to reduce parasitic losses, within reason, IMHO.

Ystervark, you are a Trooper!

keep goin...!

Tracy G

One cool thing about not having strict emissions laws in this case will be not having to worry about melted/blocked/restricted catalytic converters and the associated sensors on the exhaust side, not to mention the computer issues you could run into...

Tracy.

Do you think the Larger Plenum will have a detrimental effect on the performance and fuel economy? Also why are you saying big NO NO smog wise.

I am planning on teeing the PCV valve into the breather hose coming from the Tappet cover. That hose goes to the underside of the air filter.....Is there any reason why I should consider putting the PCV Valve back where it came out? My reasoning regarding the PCV Valve is on the point of entry below the throttle plate it will cause an increase in pressure and as I understand it we need lower pressure in order for the fuel to vaporize easier.........Or am I missing something here????????

So is it better to get real world results or more scientific results regarding fuel economy. I mean what result is there if you have to hope the owner of the vehicle drives carefully in order to save fuel. I am a bit confused regarding this??????????????

Thanks Tracy and Greg for the great input. I do appreciate it .........

Greg..

I had a look at the RVS and it looks like an amazing product. Very pricey for me though. But will consider it for future reference. $ 80 works out at about R 1165.00 that is excluding Shipping and taxes. But with savings of 7% on fuel it comes to about 5.5 months worth of driving at 2000km per month to make up That kind of money.......

Kind regards

Martin

it is a fantastic product.
I feel your pain on the exchange rate...the REAL question is whether the return on investment duration is worth it to you...if gas goes up in price, that shortens it, as does the improved fuel efficiency. 7% is a bit conservative as I recall...6 months might be a bit long...

Hi Martin. The increased plenum volume probably will only increase power in midrange
RPM and up. Since you are using a Weber, the idle circuit is very responsive, so you can probably tune it to a sharp point, IF you can get jets. Unless you or someone else you talk to knows Webers thoroughly, expect a learning/tuning period to get it right. It's not hard, if you have the info, and a jetting kit, or access to jets. The Weber has replaceable jets for idle, and main jets for primary and secondary, and may also have air correction jets too. Myself, I'm pretty picky on carb's. I have always done a proper rebuild/cleaning/soak in Carb Dip, rinsing, blowing out, and replacing soft parts w/ a rebuild kit. And checking adjustments to spec as I go, I don't like to be "out in the woods" w/. a carb, so I'm careful. Just my way of it. I wonder if there is a Weber dealer/Importer for SA? I'd bet there might be. And if you are already on top of all this, call me Captain Obvious!

As to the Orange/Peach test results VS. real-world, well thats self-evident. the Testing is to establish a data baseline. And usually gets the highest economy results possible. I explain to people that it's purpose it to show what's POSSIBLE to do with a car. Real world in traffic, etc. can virtually never give the same results. But the Test numbers can be shared with the Owner/Driver to let them know the potential rewards for careful driving. We can do vehicle mods to
infinity, but the Driver has to do the Driving, and results will vary. Just look at the years of controversies about advertised Mileage numbers for new cars vs. Driver claims, it never ends. But- we Gadgetmen get to talk about Power and Emissions improvements as well!! Lucky us! (Thanks Ron!)

On the PCV- ya see, here we have to go for Smog Checks annually, and part of that is a visual tampering inspection. But for you, no problem, I was merely alluding to that. Since on this engine the PCV valve itself IS the man. vac. source, you can just leave it in place and cap it. Or remove it and install a suitable threaded plug. Then as you said ( I think) take the hose that was on the PCV valve and tee it in to the breather hose between the valve cover and air filter. And you can put the PCV valve as a one way valve inline between crankcase and breather hose. All that would do is guard against a bad backfire out the carb going to the crankcase. But proper precautions against backfire can negate doing that. As long as the accelerator pump is OK, and ignition timing is OK and there aren't ignition misfires causing unburned fuel mixture, It ought to be OK. The PCV valve itself may cause restriction in the re-routed setup, you don't have manifold vac. positively venting the crankcase anymore, just crankcase pressure. If you use a chrome open element air cleaner like mine w/ the Weber, it should have a plastic nipple underneath on one corner to attach the breather hose. At high RPM's, there may be slight pressure drop across the nipple opening inside the air filter, helping to draw in the increased crankcase gas volume at high RPM's. Then after it's all together, if you can, re-check the re-route mod to see if any oil migrates into the hoses (or water vapor condensate). This may take time to manifest, if it does. And there are solutions to that here in the Index.

Carbureted engine setups, esp. conversions like this, can require more thought towards details, where w/ Injected, you basically work with what already is.

RVS- there is another similar product called XADO, from Ukraine/Russia, I think its widely sold in Europe. I used it before I tried RVS. It might be more available or cheaper in SA. I found mine on Ebay.

Tracy G

Greg.

Thank you for the heads up on the RVS. It seems like an amazing product.

Tracy.

Thank you for the input. You see that is why I do the orange test the way I did. If the driver of the vehicle complain we all know it will be driver error/over use of power that influences the fuel economy.

Now I understand you Americans with all your Rules Ha Ha Ha. This is Africa here we the people make the rules and the conversions the way we like it............

So everything is almost done. I still need to fit the air cleaner/filter. I am happy with the power increase we got on the 32 36 Weber.

The groove looks ok. I think it could have been better.........

I also increased spark gap from about .75mm to 1.2mm and I cut a part of the L shape steel away to improove spark...

I did a second orange test with the weber carb ungrooved. I will do a third test with the weber carb on after the groove. Then I will compile the results here.......

Seeing this carb is a progressive carb. Should I groove the secondary stage/port as well?

I think the general rule is to leave it alone unless there is enough metal to do so. Tracy or Ron would be the experts on that...
I wonder if anyone has researched or experimented with the timing of the point where/when the secondary opens, other than the manufacturer? (Follow my thinking here?)That may be an indicator of whether a groove there as well will be beneficial to our purposes...
Those look like thick throttle plates; have you considered shaping them in addition to grooving?

Hi Martin, looks about done. Your Groove is a bit choppy, and it looks like it broke thru to the epoxy back fill. But that's what back fill is for. It can be difficult w/ carb's the small bores mean the angles are tight. Plus the Groove is short in length this means extra care is needed to maintain the angles. The radius of a bore like this is changing with easc chop cut. But- you got a really deep groove relative to bore size. You say your happy w/ the power increase, and that's good!

Was rejetting necessary?
a Weber should give increased power on it's own. I found that my new one needed a few steps leaner overall.

And I really like how you treated the plugs, cutting the center electrode back will un-shroud the spark kernel, and will lead to better flame front propagation. Another tip is: for something old like this w/ no computer or much electronics, IF new plugs are needed, try to get Non- Resistor ones. That reduces resistance in the ignition Secondary side, as long as some radio noise is tolerable.

Secondary side, Ron says and I'd tend to agree, leave it alone. Though, in this case, esp. w/ epoxy back fill, breakthrough is no concern. You could try it however, and see. Throttle plate shaping, for this carb, like mine, would be dicey. Small margin for error, with small plates, and a big groove as well.

I'll await your results eagerly!

Tracy G