Build 2 motors? L18 & (L) z20e

Engine, Transmission and related drivetrain.
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gumby510
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Location: Appleton wisconsin

Build 2 motors? L18 & (L) z20e

Post by gumby510 »

Ok, datzenmike has me thinking.

I have my z20e motor on the way, which has the desirable 6in rods.

Now im thinking of doing 2 motor builds now.

Build my current L18 and use the forged 87mm pistons I have.
And
Do the z20e with a a87 peanut head and some 87 or 88 mm flat top pistons.

So my question is using the same head, cam, solex 40mm (36mm venturi) twin side drafts, header, exhaust (2.25in)and compression ratio (10:1cr for comparison.)

L18 -1854cc
Vs
LZ20e-2045cc

1. How would these motors compare to each other in terms of hp/tq and "enjoyment" of the driving experience. This is not a track car.

2. Is it as simple as the Lz20e will have 10% more hp and tq over the L18 along with having a lower power band.?

3.Is using my twin solex 40mm side drafts going to choke or limit the performance of the z20?

4. Between the 2 is/would there be a night and day difference? Or would it be more of a subtle difference.

I know you guys are probably tired of my questions by this point but here I am.

Thanks
71 PL510
92 rhd 180sx
01 s2000 aka skidmark
03 wrx winter car
datzenmike
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Re: Build 2 motors? L18 & (L) z20e

Post by datzenmike »

What's the pin height on both pistons? You will want about 38.2mm for the L18 and 31.75mm for the Z20E engine. Taller than these and the piston will hit the under side of the head.


A Z20 block with 87mm flattops and a closed chamber head will produce an 11:1 compression. A bit much for a 'non track' car. I get 10.3 for L18 flattop 87mm pistons, A87 closed chamber head. Both are a bit much for me but you might like it.

All things equal..... the larger displacement engine will always make more power and torque. Torque is that great feeling of being crushed back into your seat as the car accelerates forward.

Generally a larger displacement engine has a stroke increase. A longer stroke lowers the safe rev range. A shorter stroke engine can safely rev higher.

2/ Whatever the L18 makes the L20B would be still 'about' 10% more. They don't have the exact same compression but close.

3/ Don't know. It's possible that reverse is true and they are too large for the L18??? I don't know.

4/ I think +10% -ish would be just noticeable. The L20B would 'come on' sooner at lower RPMs. I replaced my 521'sL16 with a car L20B and it was a little over geared to notice first and second but 3rd would pull harder and 4th didn't need a down shift to pass as much. Course this would be a 25% increase.

I would go with the largest displacement you can manage.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
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bertvorgon
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Re: Build 2 motors? L18 & (L) z20e

Post by bertvorgon »

I am with Mike on this one. Putting the fact that I am turbocharged aside, I lived going directly from my 1800 at the time, to my 2 L.

Before boost, I really noticed the increase in that wonderful bottom end torque, over my 1800.

At the time I used the same intake manifold, cam, and my Un-modified at the time, stock 32/36 Weber.

Anytime you can honestly seat of the pants feel a difference...it is better.

Remember...HORSEPOWER is how fast you hit the wall, TORQUE is how far you take the wall with you....!
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer
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gumby510
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Joined: 18 Sep 2011 10:59
Location: Appleton wisconsin

Re: Build 2 motors? L18 & (L) z20e

Post by gumby510 »

datzenmike wrote: 25 Feb 2021 18:18 What's the pin height on both pistons? You will want about 38.2mm for the L18 and 31.75mm for the Z20E engine. Taller than these and the piston will hit the under side of the head.


A Z20 block with 87mm flattops and a closed chamber head will produce an 11:1 compression. A bit much for a 'non track' car. I get 10.3 for L18 flattop 87mm pistons, A87 closed chamber head. Both are a bit much for me but you might like it.

All things equal..... the larger displacement engine will always make more power and torque. Torque is that great feeling of being crushed back into your seat as the car accelerates forward.

Generally a larger displacement engine has a stroke increase. A longer stroke lowers the safe rev range. A shorter stroke engine can safely rev higher.

2/ Whatever the L18 makes the L20B would be still 'about' 10% more. They don't have the exact same compression but close.

3/ Don't know. It's possible that reverse is true and they are too large for the L18??? I don't know.

4/ I think +10% -ish would be just noticeable. The L20B would 'come on' sooner at lower RPMs. I replaced my 521'sL16 with a car L20B and it was a little over geared to notice first and second but 3rd would pull harder and 4th didn't need a down shift to pass as much. Course this would be a 25% increase.

I would go with the largest displacement you can manage.
Datzenmike

I would be looking to run 10-10.3:1cr on both motors

The pistons I currently have are 87mm with a 38.1mm pin height. For the z20 I would have to buy the correct 31.75mm or use l20b/z22 145.9mm rods and a 38mm pin piston, but that would get rid of the long rod advantage and increased rpm id like to run.

When it comes to the "feeling" I really am torn. I have my s2000 which revs for days but has no tq but with a 4.77 final drive its a fun car. With my rhd sr20 180sx, 2.0L wrx and when I had my geared manual is300 I get to experience the joy of driving cars with matching hp and torque.

With the twin solex 40mm i can always put a smaller venturi in for the l18 if the current setup is too large.

Bert,

I agree, and that is what I was looking to hear. I wanted to know is the difference between the 2 was really noticeable or just a little.
71 PL510
92 rhd 180sx
01 s2000 aka skidmark
03 wrx winter car
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