L20bet Turbo Project

[slodat]

I picked up a really nice turbo manifold a few months ago. I am now starting to put together the pieces to turbocharge my L20b. It was built by the previous owner with turbocharging in mind. It has ~8.5 compression ratio and the oil drain was plumbed into the oil pan. After talking to a couple people who have had turbo L motors, I have decided to limit boost on this engine to 5# because I have cast pistons.

 

Thus far, I have the manifold, a small Nissan T3 turbo with no shaft play. I'm not sure of the specs just yet, but will figure out how to decode the numbers. The turbo came with a new Blitz BOV. I also have some quality oil fittings. -4AN for the feed and -10AN for the drain. The downpipe that came with the turbo is cast iron, very very heavy and interferes with the steering box. So, plan is to fabricate a new downpipe that eliminates the internal wastegate and use an external wastegate. The manifold doesn't have a wastegate flange so, I was thinking I would buy this T3-T3 adapter with a 38mm wastegate flange in between and run an external wastegate with a .4bar spring. I have an intercooler coming that I think will work.

 

I have programmable fuel and spark via MegaSquirt II with EDIS, so I will be able to tune the combination. I also have a LC-1/XD-16 for the wideband.

 

I only have a MIG welder, so the plan is to use mild steel for the plumbing.

 

My fuel system - Walbro 255lph in tank fuel pump (240sx stand) with the 240 sx internal sump to prevent pump starvation. It's installed just the same it was in the 240sx tank. -6AN fittings silver soldered to the pump outlet and return line. -6 hose to the fuel rail, an Aeromotive FPR and -6 return.

 

I do not plan to race the car at all. I am not concerned about "getting addicted to boost" and upping the boost to the point I destroy the engine. I think 5# on this engine would make me really happy. If this setup works out well, I will save for and have a engine built for higher boost.

 

I am open to all opinoins, suggestions, etc on this project. I have done some research, but want any input you guys may have.

[Icehouse]

So, plan is to fabricate a new downpipe that eliminates the internal wastegate and use an external wastegate. The manifold doesn't have a wastegate flange so, I was thinking I would buy this T3-T3 adapter with a 38mm wastegate flange in between and run an external wastegate with a .4bar spring. I have an intercooler coming that I think will work.

 

I have programmable fuel and spark via MegaSquirt II with EDIS, so I will be able to tune the combination. I also have a LC-1/XD-16 for the wideband.

 

I do not plan to race the car at all. I am not concerned about "getting addicted to boost" and upping the boost to the point I destroy the engine. I think 5# on this engine would make me really happy. If this setup works out well, I will save for and have a engine built for higher boost.

 

I am open to all opinoins, suggestions, etc on this project. I have done some research, but want any input you guys may have.

 

 

I don't think you need to add a external waist gate, if your turbo is off a production line car the internal waist gate should be fine. All you need to do is redrill the waist gate "stick" farther away from the vacuum diaphragm. I'd say about 1/4" or maybe a little less, if the boost is bellow #5 you can add washers to shim up vacuum diaphragm closer to the waist gate to turn up the boost. Most people don't know this and spend there money on those cheap "boost controllers" when all they really need to do is drill a whole :D If for some reason the boost spicks then you should think about a external waist gate. If you use a intercooler I don't see why the engine couldn't handle 1/2 a bar like all nissan turbo cars run..... well that I know of. The none turbo SR's can handle 20psi on stock internals and they are 9.5-1 compression, or maybe 10-1 anyways I'm just looking out for your interest, I know you will get addicted to the boost :D O I almost for got, are you going to run a knock censor?

 

 

P.S. You said you wanted opinions :D

[slodat]

I don't think you need to add a external waist gate, if your turbo is off a production line car the internal waist gate should be fine. All you need to do is redrill the waist gate "stick" farther away from the vacuum diaphragm. I'd say about 1/4" or maybe a little less, if the boost is bellow #5 you can add washers to shim up vacuum diaphragm closer to the waist gate to turn up the boost. Most people don't know this and spend there money on those cheap "boost controllers" when all they really need to do is drill a whole :D If for some reason the boost spicks then you should think about a external waist gate.

 

You are correct, I don't need to run an external wastegate. What I am avoiding is the extremely heavy cast iron downpipe/wastegate setup. I also don't have room to run it, even if I want to. So, I fabricate my own downpipe and use an aftermarket wastegate, and I get the clearance and a big jump in reliability.

 

If you use a intercooler I don't see why the engine couldn't handle 1/2 a bar like all nissan turbo cars run..... well that I know of. The none turbo SR's can handle 20psi on stock internals and they are 9.5-1 compression, or maybe 10-1 anyways I'm just looking out for your interest, I know you will get addicted to the boost :D O

 

After talking to someone who has turbocharged a few L20b's with cast pistons, I am going to stick with 5#. The reason is the cast piston ring lands fail under higher boost. I don't want to grenade this engine. I'll build an engine that can handle the higher pressure down the road. This is to get the setup installed and running well and to enjoy it :)

 

I almost for got, are you going to run a knock censor?

 

Yes, I think I will run a knock sensor. As I said above the 5# boost is a cast piston issue.

 

Thanks for the input. More! More!

[Icehouse]

 

So is the waist gate to close to the steering box? I remember the steering box being in the way when I put the ca18et in my brothers car and even more in the way for my SR.

[Bulletside]

You may know this but make sure and use thick flanges on your fabbed downpipe, since your keeping the boost low 3/8" should work fine but alot of the better downpipes use 1/2" flanges, but then again they're going for 20-30 lbs. of boost. Sounds like your doing it right by setting it up nice and safe, enjoy it for a while, then fatten up the fuel map and take out a little timing at the top you should be able to crank it up a few more lbs. Can't wait to see how this progresses!

[sjeff64]

I am turbo stupid but I am building a turbo motor anyway. my question is this, I have to build a new exhaust housing for mine because it points the wrong direction IF I am running an aftermarket BOV do I really need to plumb for factory waste gate?(like the pic above)

Jeff

[Icehouse]

Jeff the BOV is on the intake side Waist Gate is on the exhaust side. I don't really know how to explain it but you need a waist gate wether it be external or internal. You should try and use the factory one in my opinion. You should start a project thread on your turbo project. Some pics and we could help you out :D

[sjeff64]

ok I dont have a problem welding a port for it in was just wondering(remember turbo stupid)

[slodat]

Bulletside, you are correct on the flange. I am making the downpipe out of a 1/2" mild steel CNC cut T3 exhaust flange. The wastegate port will be drilled out to plumb in a 38mm Tial external wastegate. I plan to run a .4bar (5psi) spring in the wastegate to get it running on boost. Once the bugs are ironed out, I'll sort out methanol injection and boost control above 5#. I've been told by others that I can probably reliably go 7-9#. I'll wait to do so until I've got it running well.

[datzenmike]

Remember this, ignorant is just not knowing something, but you can learn. Stupid is not being able to learn. Lets just say you may not know a few things, but are willing to learn. lol

 

A turbo without a wastegate is an insanely dangerous positive feedback system. The more gas and air you put in, the more exhaust out, the faster the turbo spins, which rams even more gas and air in which makes more exhaust, more turbo spin, more gas and air, exhaust, spin, BOOM! The wastegate tailors the boost to a preset limit and any excess exhaust is by passed the turbo and dumped out the exhaust pipe.

 

If an engine under boost should suddenly have it's throttle slammed shut, say between gear changes, the turbo which is still spinning at 100,000 RPMs will keep pushing air against a closed door and suddenly slow down or stall. The BOV's job is to sense this excess pressure and dump it, allowing the turbo to 'free wheel' or keep spinning so that when the throttle is jammed open there is do delay or turbo lag as is 'spools up'. The BOV lets out a loud hissing sound when it vents excess air but I believe Keith Law in Vancouver, dumps his into the exhaust pipe of his 510. It's just quieter and doesn't give away that you have a turbo.

[slodat]

I've been thinking of plumbing the BOV outlet to the exhaust for the same reason. I think my car will make for a very good sleeper - even with the turbo.

[nismopu]

i dont see the l20's pistons being any weaker than ones used in the l28's and most other nissan engines. Heck the l28's handle well above 400hp on stock cast pistons and the VG's are right about the same. Remember its not the amount of boost your shoving in but the VOLUME of air. Being an engineer yourself I am sure you know the difference. 5psi out of a super 60 nissan t3 is quite a bit of air for your standard L-series but still leaves for some more to be desired. If you could post some pics of the turbo I could probly help you identify it, theres usually some pretty common characteristics with the nissan t3's. Especially if it has a 7 bolt DP instead of the standard 5 bolt. peace.

[Icehouse]

Wow Mike, you are the last one I expected to see answer this one :D

 

 

Nissan usually pipes the BOV back into the intake before the turbo. I have never heard of the BOV going into the exhaust, wouldn't that make the engine pop due to the air temp difference? Kinda like an exhaust leak.

[slodat]

You are right Iceman on the BOV.

 

Nismopu - I was basing my conservative boost numbers on something I was told from a friend I listen to about these things. After talking to him some more, it sounds like I may be able to go 7# on the existing engine. I don't think I will go above that until I build an engine for the boost. I just scored a set of FREE forged JE pistons! So, I have a start on the engine parts.

 

 

 

[datzenmike]

Wow Mike, you are the last one I expected to see answer this one :D

 

 

Nissan usually pipes the BOV back into the intake before the turbo. I have never heard of the BOV going into the exhaust, wouldn't that make the engine pop due to the air temp difference? Kinda like an exhaust leak.

 

Piping it in front of the turbo would be much much more efficient at keeping the turbo spooled up as it would be a closed loop. The air coming into the turbo would already be moving pretty fast

 

On a carb engine the exhaust would be quite rich on deceleration and there might be some popping as the extra air ignited the gas.

 

I have a BOV from a Mercedes diesel and it dumped into the exhaust manifold.

[slodat]

Looks like my turbo is probably from a Z31.

[datzenmike]

Wow Mike, you are the last one I expected to see answer this one :D

 

Don't be fooled, my knowledge is more erudite than actual.

 

The Chrysler 2.2 turbo runs around 7 lbs and the later ones with senser control will go 9 lbs for a timed 10-15 seconds befor the computer reduces it. I think the L is over engeneered and would handle 5-7 lbs all day, with short blips to 9 lbs. As long as there is time to shed the heat produced from this.

Either way an oil cooler is esential on a turbo motor plus an idle 'cool down' after hard use, around town should be fine.

[Bleach]

On the L28 turbo, the pistons may be the same casting but the rings sure aren't. For whatever reason, the turbo rings can handle more pressure. Also, the L28 turbo has dished pistons for lower compression. That makes a big difference on how much boost they can handle.

 

Boosting an NA engine is quite different than boosting a factory turbo engine.

Keep the boost low unless you have really good aftermarket management. Carbs would be considered the lowest form of fuel management.

 

The L28 Turbo has been known to put down "up to" 350hp to the wheels on factory internals but not with factory management. And at that, they are running a static compression of 7.4:1

People have also put the factory Nissan turbo parts onto the NA engine with 8.8:1 compression but they do not usually run more than 10psi. You get more output from that 10psi though due to the higher compression.

 

Head design will also make a big difference. All the L28 turbo applications are usually assumed a P90 head with closed chambers. Open chamber is even worse for misfire due to its design. (not considering compression in this case)

[nismopu]

well considering I have blown up a few boosted engines myself I will agree with you to some extent. The ring lands are what actually support the rings themselves so it wont matter what kind of rings you have if these dont hold up. Tons of guys have boosted there n/a l-6's and made about the same power number. I truely belive that the stock l-20 bottom end even in flat top form can handle 300hp easy, with proper tuning of course.

 

Yes, it looks you have a z31 turbo and I dont know too many people who sell 7 bolt flanges for those things but theyre out there. peace.

[slodat]

I linked to a 7 bolt flange above. Blaast Performance flange is $40 shipped. My engine has dished pistons and the PO built it intending upon turbocharging it.

 

Any info on an oil cooler?

[datzenmike]

slodat,

Are you going to run a draw through set up with the stock L20B dished pistons, and will you switch to a peanut head? The stock compression is 8.4 but a peanut will raise this to about 8.8-8.9 which might be a good idea. As Bleach says it would give the turboed engine more snap lower down and better misfire control. Keith's L20B is around 10.5 to really help perk up the bottom end and get that turbo spinning sooner. Of course it's super modified for this but for a 5-7 lbs boost an 8.8 compression isn't totally out of bounds. You would have to run higher octane anyway so you might as well consider it, besides, you can always switch back.

Now I have to say you should really get a high volume oil pump, and oil cooler.

[slodat]

Who said anything about draw through? :) I have fully programmable engine management (as mentioned in first post on this thread). I am not sure of the compression ratio of my engine. I have asked the PO and am hoping for a response. I have a turbo oil pump with adjuster from Wolf Creek Racing on the way and I am figuring out the oil cooler.

[slodat]

Compression ratio is 8.8

[Bleach]

Summit racing sells an L-series oil filter adaptor for the block. From there you can run an external oil filter and cooler.

 

Or, the Nissan units are found only on the turbo L28 (1981-83) that also came stock with an automatic. 5-speed turbo has no oil cooler. My engine has a 5-speed AND a Nissan oil cooler. :D

[nismopu]

the turbo auto matics are pretty hard to find now a days but i was lucky enough about 5 years ago to score one in a j-yard. My new favorite oil cooler i score from j yards is the BMW 325e or i cars and also the big 80's jaguar XJ's had a sweet little unit thats very easy to remove. peace.

 

BTW a high flow oil pump to use besides the turbo l28 one is one from a stock ka24e, theyre the exact same but I am not positive about the same psi.