Just to add my two bobs worth...
Years ago (about ten) I went down the path of turbo charging L series
engines. I did it pretty much by trial and error (lots), keeping in mind
the last ten years in turbo charging development has been huge.
Without going through all the failures, I ended up with the following combo:
a) L20 Block bored, honed, O Ringed and Decked 4mm O/S.
b) Group A Skyline pistons and rings (don't ask me what model, don't
remember, but Datrally told me they were pressure cast not forged.
These pistons gave me a 5mm lower pin height and therefore lower compression
approx 6.5:1)
c) Nismo head gasket (from Datrally cost $$$)
d) Factory bearings (Datrally said good for at least 300hp)
e) Crank linished (I'm yet to see a stuft Lseries crank)
f) Modified Bosch L Jetronic mechanical fuel injection (off an early
model Volvo !!, I had small injector mounting blocks tig welded to a single
Weber inlet manifold)
g) IHI RHB6 Turbo on a shitty old cast iron manifold and 2.5" exhaust
(Second hand don't know specs of trim and comp wheel etc)
h) 'Turbo grind' cam (Just got called Datrally, who knows what they gave
me!)
i) Re-Curved electronic dizzy
j) Mazda RX2 Crossflow radiator and front mount oil cooler.
This engine was NOT intercooled (Yes it should have been).
At 17psi in produced 165Kw at the wheels (should still have dyno sheet
somewhere, dunno what that is in horsepower at the Flywheel) To give you an
idea of 'on road performance' this engine with 5spd and 3.7 diff in a 1600,
would light the tyres coming out of a slow 2nd gear corner.
The exhaust manifold glowed bright red when running on the Dyno and I
suspect turbo charger was two small and working to hard and becoming
restrictive at these boost levels.
I am confident that with a custom stainless manifold, TO3 turbo(or similar),
good Intercooler and EFI this engine would be literally a ball tearer and
25psi wouldn't be out of the question.
BUT
What I'm currently doing is exactly what the question was initially
about...putting an SR20DET into the 1600. I ultimately sold the old turbo
engine and went back to a twin Weber n/a engine after heaps of reliability
problems and the 'all or nothing' characteristics of the turbo engine
(super low compression / high boost).
This time around I had the choice of the factory developed, tried and tested
SR20DET. No doubt when it's up and running it will run like a charm, start
in an instant, provide smooth linear power and be reliable and drivable day
in and out.
I suppose what I'm trying to say is, that if you wanted to prove a point
about how much power you could get out of the L20, you could. It will make
stacks of power and the L Series is strong and will handle it (just like the
FJ20).
If you want smooth, reliable and drivable power the only answer is the SR20.
Feel free to email me with any questions,
Cam.
----- Original Message -----
From: "Tom Richardson" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, February 25, 2001 12:06 AM
Subject: RE: L20B TURBO v SR20DET
> Warning: long
>
> Denzil,
>
> I recently had a debate with a V8 knucklehead (and 2V fan) over the 2 vpc
vs
> 4 vpc subject in an engine with forced induction. I don't claim that this
> is correct but it makes sense to me :)
>
> Assume you have two completely identical engines, one with 4 vpc and one
> with 2vpc. This is obviously not a realistic comparison given that the
4vpc
> cylinder head would undoubtedly feature twin camshafts and a superior
> design, but bear with me
>
> With a 4 vpc engine, there is a distinct disadvantage at low rpm. Because
> the gross opening into the cylinder is larger, the velocity of the air
> through the ports is lower and the result is poor cylinder filling and
> consquently poor low rpm torque. This one of Bernoulli's thereoms. If
you
> don't believe me, some manufacturers (Toyota) overcame this problem on
early
> 4 vpc heads by artificially restricting the flow of the intake air at low
> rpm with a butterfly valve, hence increasing air velocity.
>
> If you replaced the 4vpc cylinder head with a 2 vpc cylinder head, the
gross
> opening into the cylinder is smaller, hence air velocity is higher. This
> results in better cylinder filling at low rpm, and strong low rpm torque.
> At higher rpm, the superior flow characteristics of the 4 vpc head will
> result in much improved cylinder filling hence better torque (and since
this
> happens at high rpm, better power)
>
> Looking ok for 2 vpc designs so far, one point to each corner
>
> However when a turbocharger (assume identical turbochargers for both
> designs) is added into the equation, the lower restriction placed on the
> inlet air by the better flowing 4 vpc head will result in improved
> turbocharger efficiency, and this means lower air temperatures, hence
higher
> density, hence increased pressure (boost) This is the ideal gas law,
PV=nRT
>
> So the 4vpc motor will outperform the 2 vpc motor at low rpm and high rpm
> (due to the same effect- higher compressor efficiency) provided that both
> turbos are producing boost.
>
> This isn't to say that its impossible to build a 350hp turbocharged L20b-
it
> has been done!
>
> I think revability would be better with the SR20DET because of the
> improvements in metallurgy since 1968, but that's not to say it's hard to
> build an L20b capable of reving to 8000rpm+. One thing you could do to
> improve revability would be to fit longer rods (ie Z20E) This results in
> smaller frictional forces in the bores, so less hindrance to high rpm.
>
> The counterflow head would be a disadvantage, but there are plenty of big
> power outputs from these designs around.
>
> I should think that if you are aiming for 300+ hp at the flywheel, this
> means you will either be running crazy revs or crazy boost (or both!),
talk
> to a local machine shop about shotpeening nitriding etc for the power
you're
> aiming for. Forged pistons would be a must.
>
> Remember that a full house (ie race) N/A L20b will pull 210hp+, so 300hp
is
> a reasonable target (IMHO)
>
> Also, there is a Z18 here in a 510 circuit racer which pulls 327hp with
> stock rods, crankshaft, and valves. It uses 125lb valve springs and a
> George Fury spec camshaft, extensive cylinder head and intake manifold
work
> with a Garret T04 on a custom manifold pushing 17psi. This is essentially
> the same design as the L series blocks but with a (rather poor) crossflow
> head - and this is with a 180cc capacity and 8mm stroke disadvantage!
> Nissan L blocks are TOUGH. Let us know how you go with your project!
>
> - Tom
>
> PS It'll be fun to tell the losers that you've just got a L20b ;)
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Denzil Palmer
> Sent: Saturday, 24 February 2001 7:48 PM
> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: L20B TURBO v SR20DET
>
>
> Looking at options for my next project, a turbo engine is a must to beat
the
> local boys in their WRX's etc. The Hot 4's 2001 yearbook has the NIS-016
510
> that does 11.4 @ 120 mph with the SR20DET, and it looks pretty innocuous
(ie
> totally stock except for the wheels and stance) from the outside. It has
260
> rwhp at 18psi, which indicates 335 engine hp assuming 22% drivetrain loss.
> Diff is a billet axle 3.9:1 R200 LSD with 225/50-15 tyres.
>
> The question is, given a similar size turbo would the L20B engine be able
to
> produce as much power as the SR20DET? Take it that the L20B would be
> injected, with after-market computer, intercooled, mandrel exhaust and
built
> to the required standard. The fact that the modern engine would be cheaper
> isn't the point. The idea is to keep the traditional L-series engine but
> with a modern induction system.
>
> Breathing (ie 2 valve vs. 4 valve) wouldn't be an issue would it, as the
> turbo force-feeds the cylinders anyway. What about rev-ability and maximum
> attainable revs, is the L20B too long a stroke and too slow to rev? Is the
> non-crossflow head a disadvantage?
>
> If the 300+hp L20 B turbo idea is feasible, then what needs to be done
> w.r.t. engine internals? If anyone has already done this your thoughts
would
> be invaluable.
>
> Thanks
>
> Denzil Palmer
> Queenstown
> New Zealand
>
>
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