Build thread for L20B/L20DE, LZKA20/24E, something...

[KC Phirus]

We run ITM pistons in a couple different high compression motors.... Got an L20B(basically) running ITM pistons at 11.5:1 compression and 8000RPMs, but it runs on 113 VP gas ONLY. The 113 really helps keep temps down in the combustion chamber. Yes the octane rating is overkill, but the main reason is that 113 has better cooling characteristics than 110 to keep those pistons cool.

If you have any doubts about 113's cooling effect, spill some on your hand.

 

11.5:1

8000 rpm

L20

Where is the thread on this

[HRH]

Good to know you've been running ITM with success. I've had them before, never had an issue, but I'm also not running 113. Just 92 at the pump.

 

I just remembered something I forgot, regarding when I switched the fuel lines. Think I may have created my failure with the injector going lean. Even slightly lean would have been a problem. That was when I returned the fuel lines to their "correct" position regarding feed and return. I used the return spout on the tank as the feed initially since it was larger than the bottom tube. 5/16" vs. 1/4" Then it necked up to the Subaru pump.

 

Anyway, could only run to 3/4 tank before she'd starve. Switched it back in an effort to get the system correct, but it didn't seem to like it, probably the pump had a more difficult time supplying with the small inlet from the tank.

 

Short of it is, it broke, likely due to detonation or heat, and since I plan on redoing the fuel tank and lines with 5/16" for return and feed, that problem shall be remedied. Going to re-bung the tank too.

 

Think I've decided on what to do for the next motor. L20BET. Have a turbo I have to dig out and check, my Datsun guru has a turbo manifold for an L he's not using. I'll still be able to use my new kick-ass manifold he made for me, provided it clears the turbo manifold. And I'm thinking I can use L28 turbo pistons and bore the current block another .5mm to 86 mm and that should be good for standard bore on the 280zx pistons. Haven't figured out rods or efi management yet, but I'll get around to it. Pin height is the same for 280zx pistons, so I'm thinking I can pop them right in with 20b rods and they'll work, right? Or is there a flaw to that logic?

[datzenmike]

Matt, I get 10.98 compression with the info supplied. To be clear that's 0.030inch cut off the head?

 

Yes any L piston will have the same pin height so you need to use the L20B rod with it. Unfortunately you will loose the 6" long rods with this.

 

 

280zx flattops with the same shaved head will give you almost 11.1 compression. You can use any compression with a turbo but cylinder temperature management becomes critical, difficult, expensive. Using an unshaved head will allow a 10.24 compression on your turbo. Grinding some shrouding away around the valves could probably drop that below 10....

[HRH]

Hmm, maybe I did something wrong. Thought when I did it it was 11.5 or something. I was using one on the web. But yes, .030 off the head, .020" oversize pistons (.50mm), did you calculate that in?

 

Yeah, I was wondering about the 280zx pistons, I wonder if I could use an L16 rod or something to drop it down the bore and lower the cr? I would prefer something in the 8.5:1 range, or possible mid 9, but 10 is awfully high.

[datzenmike]

The next shortest rod is the L13 and the difference would be getting close to doubling the combustion chamber.

 

Get regular dished zx pistons. 0.030" head shave on open chamber head is 8.6... better???

[HRH]

Well the problem with that is I want a turbo piston or some other forged piston that can handle the stress of boost without breaking down. If I'm going to go turbo, I'm going to run a bit seeing as I want to break 200 hp with the motor. I suppose I could deck the block to an L16 height? ;) The next cheapest pistons are in the $600 range, so if I can't make something work with a different rod/crank combo, then I'll probably either pony up for good pistons or go the NA 2.4 KADE route.

 

What about a Z22 crank with L16 rods with 280zx flattops? Think that would work?

[HRH]

I see you browsing tons o fun! :D

[banzai510(hainz)]

ring gap wrong

[HRH]

Nope, gap was dead on, measured it myself per the Datsun bible recommended specs, plus this motor has 12,000 miles on it or so.

[datzenmike]

What about a Z22 crank with L16 rods with 280zx flattops? Think that would work?

 

Piston stops over 1cm or 10mm short of the top deck. That's over 60cc of volume added to the combustion chamber, forget.

 

What's wrong with the turbo 280zx pistons? They have a dish that gives 8.6 compression? I don't think the factory used forged pistons because of the cold start up noise. They are still good for 6-8 PSI boost. Forged pistons you will need more cylinder clearance for expansion. They'll work.

[datsunrides]

Well the problem with that is I want a turbo piston or some other forged piston that can handle the stress of boost without breaking down. If I'm going to go turbo, I'm going to run a bit seeing as I want to break 200 hp with the motor. I suppose I could deck the block to an L16 height? ;) The next cheapest pistons are in the $600 range, so if I can't make something work with a different rod/crank combo, then I'll probably either pony up for good pistons or go the NA 2.4 KADE route.

 

What about a Z22 crank with L16 rods with 280zx flattops? Think that would work?

 

This was a few years back, but Rebello racing sold me some custom JE forged pistons/rings for my turbo U20 for $400 or so that included pins and rings. They probably already have a design on file for what you want to do.

 

Mark

[HRH]

So I posed this thought to my Datsun guru, he's not sure: Has anyone tried running SR20DET pistons in an L block? Standard bore is 86mm, which is fine considering I'm at 85.5 right now with the .020" overbore. I have no idea what the pin height is.

[Laecaon]

Try this:

 

http://www.sr20-forum.com/turbo/31223-sr20det-piston-size.html

 

Pic explains the numbers

 

numbers at bottom of first page

[HRH]

Interesting. 1.25 pin height. The same pin height as the Z20 long rod combo I have now. According to wiseco, dish is -12cc. So that means.......I might be able to use SR20 pistons in my L20B? Question is if they would work well considering SR is alum block, whereas L is iron. Don't know if that would matter or not, don't think it would.

 

Appears wiseco offers flattops too with a cr of 11:1. The top -12:1 based on a 45 cc head is 9.1-9.25. How freakin' funny is that? U67/60 head is roughly 46-47 ccs, and I milled .030 off. So about the same, which would be FING perfect.

 

Even better, if someone has an overseas SR20 and they're building it right, they're putting in new pistons and rings anyway, which means I might have a perfectly usable set of standard bore 86mm SR20 pistons for dirt cheap. Going to have to call a buddy who plays with that stuff. Swweeeeett! This might work!

 

http://www.nolimitmotorsport.com/wiseco/apps-Nissan.html

[KC Phirus]

Don't you want lower compression for a turbo?

all fords, mitsus etc turbo engines I've worked on were real low.

Except for diesels like my benz which is like 9:1

[datzenmike]

Nothing wrong with high compression with a turbo. But you have to manage the pre ignition and extra heat. A low compression motor is just easier for less.

[KC Phirus]

Nothing wrong with high compression with a turbo. But you have to manage the pre ignition and extra heat. A low compression motor is just easier for less.

 

Heat seems to be the only killer of an L motor. Surely at some point it becomes absurd and you've made an L20 that's getting good power but has become more complicated than a more modern engine and still have less power. I'd do it anyways, just because I have one to work with.

[ggzilla]

+1

 

The latest Porsche 911 Turbo 2011 has 9.8:1. The temperature is controlled by highly efficient intercoolers and careful tuning. The middling-high 9.8:1 allows for good performance even before the boost kicks in.

 

No production turbo car has low compression. During the 70s and 80s most non-turbo cars were around 8.5:1. Turbos were pretty much the same.

 

The first Porsche 911 Turbo had 8.0:1 with NO intercooler.

 

The Porsche 959 supercar had 8.3:1. Still around the same as non-turbo engines.

 

On the other hand, a truly low compression engine (like 6:1) allows for maximum boost, shifting performance to max at the expense of turbo-lag and low-speed power. If max HP is all you're after, definitely go low-compression.

[HRH]

Anyone know the wrist pin diameter for an L20B piston? I'm still researching the idea of using SR20 pistons, which would put me around high 8 or low 9s for compression, which would be ideal. I'm all for high compression, but with 9.8:1, I probably won't have the cool technology to effectively manage my motor in a boosted application. Hence, why I'm going with a safer lower number, and may not even run an intercooler.

[Laecaon]

I thought Datsun wristpin diameter was all 21mm.

[I'm BLUE]

HRH ,,, somewhat off subject ,,, but not really ,,, pertaining to compression ratio ,, my 82 280zx Flat-Top Piston engine and 5spd- Zx transmission (Thanks MicroMachinery !) ,,,transplanted to a 73 240z 3.54 gears ,,, 9:1 compression ratio ,,, Almost perfect !!! I love it ,,, it's a nice middle ground to get a touch of umph ,,, for a daily driver that when occasionally passing cars ,, or going up hills ,,, is just ideal for me

 

I had lower mid 8's compression ratio before with dished pistons ,,, in the same l28e engine ,,, with high compresion in each cylinder ( healthy non oil burners in each engine ) ,,, world of difference to bump up to 9:1 ,,, for whatever reason ,,, definetly could tell between the two ! ,,,

 

Biggest Point ,,, I typically run premium ,,, carb/injector cleaners ,,, etc ,,, I also run Chevron only when I can ,,, but with the 9:1 ,,, I can run regular just fine all day long ( winter blend ) ,,, summer blend gas I go to premium ,,, typically

 

Back on topic

[LenRobertson]

From 1979 200SX FSM - "Pin diameter mm(in)...20.993 to 20.998 (0.8265 to 0.8267)".

 

I recall something about the need to O-ring the block and/or special head gasket if you try to run much CR/boost on an L engine. I have no idea what the numbers are before you need to worry about the stock head gasket, but it worth researching. What other make engines can run for CR doesn't matter if the L head gasket is a limiting factor.

 

I had this page Bookmarked: http://web.archive.org/web/20031006102627/home.att.net/~jason510/turbo.htm This may be really dated info, but maybe something of interest anyway.

 

Len

[datzenmike]

Interesting. 1.25 pin height. The same pin height as the Z20 long rod combo I have now. According to wiseco, dish is -12cc. So that means.......I might be able to use SR20 pistons in my L20B? Question is if they would work well considering SR is alum block, whereas L is iron. Don't know if that would matter or not, don't think it would.

 

Appears wiseco offers flattops too with a cr of 11:1. The top -12:1 based on a 45 cc head is 9.1-9.25. How freakin' funny is that? U67/60 head is roughly 46-47 ccs, and I milled .030 off. So about the same, which would be FING perfect.

 

Even better, if someone has an overseas SR20 and they're building it right, they're putting in new pistons and rings anyway, which means I might have a perfectly usable set of standard bore 86mm SR20 pistons for dirt cheap. Going to have to call a buddy who plays with that stuff. Swweeeeett! This might work!

 

http://www.nolimitmo...pps-Nissan.html

 

Matt shaving your open chamber head 0.030" has made it a hair smaller than a peanut. Anyway 86mm bore SR20 pistons with 12cc dish, your compression would be 9.11 but with a fresh non-milled open chamber head it would be 8.47, so you have choices.

 

 

Anyone know the wrist pin diameter for an L20B piston? I'm still researching the idea of using SR20 pistons, which would put me around high 8 or low 9s for compression, which would be ideal. I'm all for high compression, but with 9.8:1, I probably won't have the cool technology to effectively manage my motor in a boosted application. Hence, why I'm going with a safer lower number, and may not even run an intercooler.

 

Wrist pins are 21mm as stated. Use SR20 wrist pins and have the Z20E rods sized to fit them. Don't forget they are press fit.

[LenRobertson]

About half way down this page http://www.datsport.com/racer-brown.html in the "Piston-to-valve clearance" section is a bit of info on O-ringing. And near the bottom of the same page is Datsun turbocharging info.

 

Len

[HRH]

Haha, came to the same conclusion Mike! Have to talk to the machinist, but I'm pretty sure I can get away with 1 mm overbore of the rod end, as ONLY the LZ20 rods will work with this hair-brained idea I have. And where the heck am I going to find an unmilled L20 head? Don't think I've ever seen any left alone, not at this age.

 

Next is finding a set of stock pistons from an SR20DET, need to probably check the 240 forums. My guy doesn't have any at the moment, but I think I might know someone else who does. Might be able to buy some on ebay too.