My l18 turbo blow through 620 finally running!!!!

[jwerty1]

doing a blow through setup on my l18 and i'm trying to get everything worked out.  Can I just add an inline fuel pump with rising fuel pressure regulator in addition to the stock pump, or just take out the oe pump?  Also anyone run return lines themselves?  Any advice will be greatly appreciated.  I'm a ratsun fool, and I've been searching different things for a while and never find the right answers. Thank you

[620Turbo4X4]

How about some Picts?

 

Might as well get rid of the OE pump. You need a fuel pump that is capable of producing 3-4 psi above your maximum boost pressure, and yes, you do need a rising rate fuel pressure regulator or the boost pressure will prevent the carb from filling with fuel.

 

I can tell you from experience that carbs and turbos don't work well together. You would be much better off going with fuel injection. Personally I prefer the Electromotive injection systems. If you keep your eye on eBay you can find old TEC 2 systems for around $200-$300. With the latest PROM upgrade, these are very powerful, and versatile laptop programmable systems. Cut the center cylinders from a injected 280Z intake manifold, weld back together, and there you go.

 

Just my 2 cents….

[jwerty1]

ok, well out with that previous fuel pump idea.  I will be deleting my oe pump and running an inline fuel pump and regulating it down to where I need it.  I have read up on the FI systems, but I wanna try this route for fun.  I enjoy having this lil ol carbed truck.  Where should I get the turbo oil feed from? Is there a plug on one of the main oil galleys and can put a fitting on?

[620Turbo4X4]

The easiest way to get oil to the turbo is use a T fitting at the low oil pressure switch and use 3/16" steel brake line and run it around the back side of the head. I'm sure they may be other ways of doing it, but this seems to the most common I've seen.

 

What carb are you going to use? You'll want to be sure it doesn't have vacuum secondaries and build a sealed carb box to put it in. Plus also have a intercooler. The pressurized air from a turbo is typically in the 300-400 degree range and will boil the fuel in a float bowl in seconds.

 

I still strongly advise against turbocharging a carburetor engine. Your ol' carbed truck will never be the same with a turbo. Turbos had a bad reputation when they were first introduced because of being carbureted. Either draw through or blow through, they both have their huge list of problems which usually leads to fire and or catastrophic failure.

[jwerty1]

I have a weber 32/36 that im using, it is mechanical secondaries.  I have a plenum hat for the top of it, and am copper spraying the gaskets for the carb.  Intercooler is on the way, manifold is basically done, just need to go over it and double check for leaks and then prep it and ceramic coat it.  I know that it won't ever be the same, but its not my daily and my wife said I could do it finally.  I've been wanting a lil turbo truck for a long time now.  I have a wideband af gauge that I'm going to monitor like a hawk and see what I can do.  It's possible I might try to figure out a fuel injected setup sometime, but I really wanna try the turbo carb first. 

[datzenmike]

I wouldn't copper spray anything. If the carb is enclosed, the pressure outside will equal the pressure inside. If just blowing the air down the throat it's only 9PSI or so. The gaskets will handle that. Once 'glued' together you'll have an absolute bitch of a time taking the carb apart for fixes, tuning changes or repairs.

[paradime]

You can find "boost referenced" fuel pumps that will keep your fuel feeding into the bowl, but that won't help you get fuel through the venturi at 5psi of boost.  Blow through is a can of warms that ant guna catch you any fish. Draw throw is the way to go?

[620Turbo4X4]

I know what you mean about wanting a turbo Datsun.. My second vehicle ever owned was a '76 L20b turbo 620 pick-up. Thing sounded awesome!! Mine had a draw through with a '79 Mustang Holley/Weber carb, T-3 turbo, O-ringed head, and stainless valves. Lots of fun to drive, Burned rubber all the way through 2nd, and chirped 3rd… but, I was always having to work on it or do something to it.

 

Unfortunately the cast pistons ended up being my weak link and when my water injection jet plugged, broke all the piston skirts, and ended up taking out the turbo too. (melted the turbine wheel)

 

I wouldn't use the copper spray on your gaskets. Bitch to remove, and I think the stuff dissolves in fuel anyways. Your going to have a hard time sealing all the leaks unless the carb is contained in a box. The worst will be the fuel leaking from the throttle shafts, dripping down on the exhaust, it will also leak where the choke shaft goes though top plate.

 

Draw throughs are a lot easier to build and tune… but you can't intercool them.

 

You also need some way of retarding the timing as boost increases. My '76 had a MSD Boost Timing Master.

[jwerty1]

Ok, so I've read a lot, and seen about putting the carb in a box, and just putting a plenum on it.  Plenum is the way I was planning on going.  However, Im not a fan of fuel leaks onto the exhaust.  Wondering if there is anything detailed about sealing up a weber 32/36.  Also, any ideas on a starting jet size for the secondary?  My exhaust manifold is basically done.  Oil feed and return should be done this week, as well as coolant lines.  Exhaust is very close to done.  Found a spot to mount the intercooler, just need to wait on my silicone couplers to show up to start on that.  Anyway to do the timing safely without the boost master?  I have the stock dizzy with pertronix kit and coil.

[datzenmike]

Another problem with draw through is the high vacuum created between the turbo and the throttle plate when closed at speed. The vacuum can and will suck oil through the turbo seal, unless dealt with.

 

As mentioned, a draw through can't be inter cooled and that increases the risk of heat induced detonation at the same boost as a blow through. All things equal a draw through will need more boost retard and make less power.

 

It IS way easier to make though.

[paradime]

Well said Mike, Is Keith Law's car blow, or draw? He would be a great resource. I know Julian's attempt was draw through. He used the T25 off my SR.

[datzenmike]

It's blow through. Has a neat little box for a weber carb. The venturis and throttle bores have been ground down to let more air through, has a red warning light if oil pressure drops below 60? PSI, fuel pump follows the boost, huge GM air conditioner evaporator for an oil cooler, inter cooler, alcohol water injection, 10.5 to one compression, air fuel ration meter, exhaust temp gauge, forged pistons and probably forgot some. (It's an L20B but wouldn't surprise me if it had some extras in it)

 

Keith's philosophy is heat kills power and motors, so deal with it and reduce it before rather than deal with the problems it causes later.

[jwerty1]

I'm doing a blow through, not a draw through.  Anyhoo, I read that whole 22 page thread on 510 realm about that setup, lots of good info.  Any thoughts on the secondary jet to start off with, or just when I'm ready fire it up and see what I'm getting a/f wise?  Also, that thread went into some detail about timing and getting the msb 6 btm to retard the advance.  However, I was wondering if there was anything else possible to keep the timing safe.  I am going to put on an oil cooler, the intercooler is in place and I got a bigger alum radiator to keep the coolant cool.  I have a pertronix kit in my dizzy and the pertronix coil, set to factory timing specs as of now.  Should I stick to the factory timing or do something else when I get it running?  BTW finished the exhaust up tonight, as far as making it.  I'm going to port match the exhaust mani some more, and then I'm going to ceramic coat that, turbo, o2 housing and downpipe.  Just so you all know.  I have a 74 620 with an l18 and I got a 14b turbo off an eclipse.  I have most the bits and pieces to the rest of the install, wanted to finish the exhaust first.  Then most likely I'll do the intake this week.  I have a carb hat from lc engineering they sell for a remote air filter kit on the weber.  I have an oe replacement fuel pump for fi cars, bpa turbo rrfpr, no name bov, innovate motorsports wideband kit, no name boost gauge, no name boost controller, fuel pressure gauge, no name intercooler, should be getting my sandwich adapter for my oil filter this week, the list goes on.  I'm quite excited about this build, I can barely sleep.  Ever since my wife said, sure, you can turbo you're truck.  Finished up the exhaust with a short section of 2.5" nismo titan exhaust cut up, then finished the rest off with 3" oe cummins pipe I took off my buddies truck when he installed his 5" exhaust. The tailpipe is actually the downpipe off that truck and it looks pretty cool.  I'll have to figure out how to post pics so I can let you all in on this build.  Also a bit about me, I'm a master Nissan mech for a living(I get to work on gtr's!) And I have loved lil 2wd trucks for a long time, owned several Toyotas and figured 2 years ago I outta buy a Nissan/Datsun. Found this orange one on craigslist with 58K original on it from the original owners grandson and had to have it.  It is also important for you all to know that I love lil trucks, but cant stand them being bagged and dragging.  I want mine to perform.  Sorry to ramble on, but its all I'm thinking about lately.  Important questions being:  What jet to start with?  Any and all timing info?  Other than a hat on the weber, what else should I do? 

[datzenmike]

Carbs mix air and fuel using a venturi to suck the fuel in. They are fairly even across the board... meaning the a/f ratio is about the same at low speed as at high speeds. A turbo will push more air, the venturi will cause more vacuum and more fuel will be drawn in. Generally a turbo won't cause a carb to run leaner however... performance wise, richer is better. Even stock carbs are designed to run richer when wide open that at cruise.    

[paradime]

Man I've been in your shoes and envy that thrill of excitement when formulating your build. Obviously I've underestimated your skill level with my draw through comment. It appears you have dealt with those afore mentioned worms and are well on your way to success. I attempted a blow through L20 back in the 80s with a friend, but without all the new fuel pressure stabilization, AF monitoring, timing, and boost control technologies, and no internet it was more than we could handle. We had a disco potato with no intercooler and a mechanical waste gate pushing about 5-7 psi. I recall our biggest issue was that once we hit boost the fuel was getting pushed back down the venturi leaning out the mixture. We tried bigger secondary and to maintain even fuel pressure but with the weber's vacuum fed main it was impossible without a secondary pump. I'm sure this has been figured out by now, but using old school timing and AF mixture tests proved inadequate, and unfortunately, we toasted his motor trying to figure that on out on our own. 

 

As for our starting point for the jets, we began with the same jetting the motor was running on N/A. We quickly had to switch to larger primaries though, because of all the added paraphernalia on the intake. For the mains it will be a process of trial and error. I tell you though, we must have tried every combination know to man trying to blindly dial that thing in. With all the instrumentation you'll have though, you'll get much better insight as to what the motor's doing in real time. Mark my words though, you'll get sick of pulling those hoses while adjusting, so if you can, be conscious with your intake design and make effort to make things are as accessible as possible. In the long run, every little improvement will pay huge dividends in the future.

 

Best of luck man.

[jwerty1]

This is all pretty cool to me.  I've owned several older carb'd trucks, but never really knew how it all worked.  They all ran fine so I only ever messed with setting up the timing and idle speed.  This truck on the other hand..... shortly after I bought it, it started making a knocking noise at idle.  Thought it was a bearing.  Tore out the motor and found it was loose flywheel bolts.  Tore everything down, only to find all bearings etc were good.  Put it back together and it wouldn't start.  (I rebuilt the stock carb when the motor was out, my first experience with that)  However, the stock carb never ran well when I had it anyhow.  So I ordered the weber and it started right up.  But my oil light was coming on.  Didnt think too much of it as it had always flickered sometimes, figured a loose wire or something.  Then I got to thinking, I should put a gauge on that to see the oil pressure.  0 PSI! Luckily I didn't drive it, just a couple starts in my garage.  Put an oil pump on and here I am 2 years later finally getting to what I really wanted to do.  This is fun, but I wish I was a mechanic 20 years ago when you had to have all this knowledge.  I know how to work a scan tool really well.  This old thing, not so much.  No remarks on base timing yet? don't really want to put up the pennies for the boost master right now as I'm not going for insane power at the edge of detonation. 

[jwerty1]

O man, this build is frustrating.... So I have ordered 2 oil feed fittings for my turbo, and neither fit.  Every single fitting I have laying around, nope.  Autozone, pepboys, etc, nope.  Why are threaded fittings so dam difficult.  Then the an fittings, o my.  my oil drain kit and oil feed kit came with an 10 and an 4.  Seems like nothing fits those right either.  Any good suggestions out there for oil drain fitting?  The kit I got has an 10 fitting that I am to drill out a hole for in the oil pan, but with the fitting I have it seems like it will leak.  I was thinking of just welding something to the oil pan to accept the drain line.  O yeah, then I start figuring out my fuel lines, since I can't get anywhere with the oil feed.  So my tank has a 1/4" line sucking fuel out.  Is that enough to feed an electric fuel pump?  Do I need to redo the feed from the tank to 3/8?  Cant wait to get this truck running, but it seems like everywhere I turn is a dead end.

[jwerty1]

any answers out there?

[620Turbo4X4]

any answers out there?

If you posted photos with descriptions of the problems your having you might get some answers...

 

Open yourself up a photo bucket account and post some photos.

 

As far as your timing question… Mine ran about 15-18 degrees initial advance, with the boost timing master set between 1.5-2.0 degrees retard per/lb. boost.

 

You don't need the whole MSD ignition system to use the B.T.M…. My truck used a stock '78 magnetic pickup dist W/ the BTM wired in series to a stock 78 electronic ignition module... Used a MSD blaster coil for a hotter spark. and a .020 plug gap on some cold B8ES plugs to avoid distributor cap crossfire.

 

You'll want some way of reducing the timing as boost increases no mater what power level your attempting to achieve. Trying to set the timing so it doesn't detonate under boost will only make the timing to far retarded under normal driving, which will be terrible for power, fuel economy, and send a massive amount of heat out the exhaust to the turbine wheel, possibly melting it… and or your exhaust valves.

 

For for fuel line question… The stock line should be adequate if your mounting the electric pump in the stock location under the bed.. High pressure electric pumps typically don't suck fuel too well, and also don't recover well when the inlet in the tank becomes uncovered from a hard launch with low fuel level.. (Older vehicles don't have the baffling inside the tank to prevent this)… When I get to the fuel system in my truck I'm going to use two pumps and a surge tank (low pres. for tank, and high pres. for injectors) for the fuel system.

[paradime]

I don't want to be harsh, but I have to be honest here. If jwerty's L18 isn't totally built for the task, this is a doomed project from the start. Learning to work on a Dat truck by building a blow threw setup is like learning to rock climb on Mt Everest. Nothing about retrofitting a turbo onto an L motor is going to be easy, but if you're seeing simple issues with fittings and fuel lines as "dead ends" I'm going to question whether you're ready for a project of this complexity. I'm all for biting off more than you can chew if you have nothing to loose, but IF this project goes South Jwerty's wife is never going to let him work on his truck again. 

 

Again I'm not trying to be a buzz kill, I just want to make sure we're actually helping him.

[jwerty1]

hey man, well maybe I was being a lil overdramatic, they weren't dead ends, more of a dammit I gotta get this fitting too, so I still can't do the oil feed tonight.  By the way, got the fuel setup taken care of, just need to hook it to the carb when that's installed.  O yeah, and its dialed in to 3.5 psi, and the rrfpr works as designed, as I put pressure to it and the fuel pressure rose accordingly.  It is a complex project, but im not new to working on stuff.  I've just never taken on a project like this yet. 

[jwerty1]

Wired up the fuel pump tonight with a relay.  Also wired up a fuse block that gets power with ignition on, off of a 68 roadster.  Should make it a lot easier to add my gauges and so forth, rather than tapping into the existing fuse block.  The fuse block is all tube fuses to keep the original look too.  Of course the gauges and turbo won't do much for the original look however.  Silicone hoses and oil feed fitting should be here this week and hell, I'll be close to starting this bad boy up.  So, is there anything out there for retarding the timing under boost that is more cost effective than buying a boost timing master?  Thanks for the help guys.

[620Turbo4X4]

I think Jacobs made something similar back in the day too. Good luck finding one. I surprised msd still makes the btm… Most everyone turbocharging an engine within the past 20 years goes with EFI. Tuning an engine properly can be done in days, (or even hours on a dyno,) rather than months spent fiddling with a carb and distributor system that never works right. Been there, done that…

 

There is a used btm on ebay for $50 and another ending in a few hours for $75. Wouldn't bother with anything new. Like paradime says, unless your engine is built for the task, don't expect it to last...

[jwerty1]

so its running!  very lean at first so I drilled out the jets.  Runs great now, afr's are dam near perfect.  Now to get the bugs worked out when and if there are any and setup my water injection. Thanks for the help!

[jwerty1]

So I found the stock motor mounts were allowing the turbo to hit the frame rail.  Did a bit of research and ordered up some flexane 94 and made my own mounts.  Let me say, they are harsh, but this truck is harsh anyhow, so not much of a difference there. Definently makes the motor stay put now though.  Still running good.  I have boost set at about 8psi with plans for maybe 12 with water injection.