Theoretical long rod turbo L-series, L26ET?

[Drax240z]

I'm tossing around the idea of building myself a new engine for my Z, and trying something a little different. I have tons of L series parts available, basically everything from every model of engine.

 

So the rod/stroke ratio isn't terribly good in most L series, not since the L24 anyway. Since rod/stroke ratio greatly influences detonation resistance this should be a good area to design a turbo engine around.

 

What I have in mind is a L24 crank, L24 rods, F54 block, turbo pistons, N42 head, setup. This will put me right around 8.0:1 CR, or slightly higher with a surface plane done. (Let's say 8.25:1 for arguments sake) And the rod/stroke will be 1.80. Displacement however is reduced to 2569cc on a standard bore.

 

Let's use my current engine to compare with. Stock 82 turbo engine, slight head surface, around 7.5:1CR, 2753cc displacement, 1.65 rod/stroke.

 

So the question is: What engine is going to have more off boost response? The 7.5:1CR 2753cc or the 8.25:1CR 2569cc? My thoughts are that they would be quite similar in this respect. (all other things being equal)

 

I would expect the 1.80 engine to rev more smoothly, have more resistance to detonation, get better off boost fuel economy, and in the end be able to run more boost safely. Thoughts?

 

Generally I don't expect reducing displacement to be a performance enhancer... just feeling out your collective thougthts on the matter. Who knows, someone here may have allready tried this out!

[JMortensen]

A friend of mine built a motor just like that but I believe he used a P90. Compression was VERY low like 7:1, but he was able to run 20 something lbs boost (had a GIGANTIC Rotomaster??? turbo) and had no intercooler. He loved it. I met him about 6 months after he took the car off the road, and a couple years later he just parted it out and got rid of it, so I never saw it run, but he said it was the best L engine he had, and he's owned 20 something Z's. He was convinced that rod ratio was really important, especially on a turbo motor, and I guess he didn't mind the insane lag that it had.

[Kennysgreen280zt]

I hadnt been thinking of building a motor like that, but I had thought about the rod to stroke ratio thing. My idea would be to run the 144 L24 rods on a L28 crank. The Z31 turbo pistons use the same size wrist pin but with a 10-12mm higher wrist pin (I think I dont have an extra L28 turbo piston to compair) The bore on the Z31t is 88mm, which would give you both a better rod to stroke ratio and a little displacement.

 

Ill get my Z31 piston out later and measure it. HTH

 

~Kenny

[Cody 82 ZXT]

Lockjaw runs a L-28 crank with 240 rods, custom pistons and he said it reved like crazy.

[evildky]

I wandered about the same set up, I have an a coupla motors laying around and thought about how I missed the reviness and bottom end of the 2.4 but like the big end of the 2.8ET, and noticed that the RB26DETT uses the same stroke as the 2.4 crank, and the same bore as the 2.8 and I am thinking the rod length was the same as the 2.4 as well, of course compression could be aywhere you wanted it with flat tops, dished or custom pistons and the head of your choice, be it turbo or N/A the lighter mass seemed to be a good idea I just could not justify loosing displacement, I'd love to see someone make a monster hybrid L26 and get a dyno sheet to see where the power is and isn't

[spotfitz]

This is just like a discussion I was having with a friend of mine.

Make a long story short. His argument was the typical statement with the V8's "there is no replacement for displacement". Our first discussion was based on displacement alone. That went nowhere quick, ofcourse. Our next step added the turbo into the equation. My statement to him was, with better rod/stroke ratio with everything else equal, motor "a" could produce more usable power then motor "b", due to the possibility of higher boost levels. He would always go back to the "no replacement" statement. But where does the turbo actually surpass the lower displacement "disadvantage"? Neither of us could answer specifics, but he didn't see a lower displacement motor ever surpassing a higher displacement motor, no matter what turbo/super charger you put on it. Ofcourse, if you start adding rod/stroke, compression ratio, intake/exhaust valve sizings, port sizings.....without a turbo..... you have a whole other discussion, but we'll save that for another day. Maybe...

[Doug71zt]

Hey Richard - A friend of mine has the bottom end built (for 3 years now) but not installed. His project is on hold for other reasons. He used Dodge 2.2 forged turbo pistons and 240 rods and crank in a F54 with a P90 head. With the overbore, it comes out to a 2.6 liter. It wasn't an expensive build, FWIW. It was his opinion that the RB26 was the best optimization that Nissan came up with, so why not emulate it. He is planning on twisting it to 8K. I myself like the 3.0 liter route, which I am currently building. Redline will be 7 or 7.5K for mine, depending on how much money I put into a dampner. But, then again, my next upgrade will be an RB30 with RB26 head and a single turbo. I guess you can tell what side of the fence I'm on in this issue.

I'm interested in seeing the results - a dyno chart, seat of the pants, etc. I've been at my buddy for 3 years to put his car back together in order to see how it works out. He has a custom 321SS manifold with external WG, GT3040R turbo, custom intake similar to James' with a 70mm TB. All this stuff is just sitting there, waiting. You will laugh at this, his 240 has a Dodge Cummins IC rammed in the nose, Required a little trimming of the framework forward of the rad saddle and deletion of the hood hinges. It just looks nasty in there. My local group of Z guys has a machinist, tool and die guy, millwright, mechanical engineer and aircraft engineer.

 

Sorry - a little OT.

 

Doug

[Cody 82 ZXT]

Richard, Ask your friend " If there's no replacement for displacement then how can a 2.8 N/A go from 15's or 16's in the 1/4 to 12's with the addition of a turbo?" Anyway tell him to come by and I'll show him his no replacement theory is flawed.

[zolorin]

The turbo is the displacement enhancer without actually having the needed displacement so L30 with 15 lbs of boost is approximatelly equal to the V8 with 6.0 litres of displacement (should I say chevy 350) and if you are running a 30 lbs of boost then you have 9 litres of displacement. So just use those guidelines for the no replacement for displacement theory

Turbo is the displacement modifier

[Drax240z]

Or as Reg Reimer had on both his 1 lap of america cars... "Technology is the only replacement for displacement"

 

I of course do have other options available to me, a 2.9, 3.0, 3.1L depending... I could build a higher compression 2.8L and go with that too. In all these other cases the rod/stroke ratio isn't as favorable though... I suppose this arguement is a bit academic until I (or someone else) builds it and tries it. I would think the long rod engine I speak of would be quite a good combo for a high revver all out hp NA engine, at the sacrifice of torque. (which doesn't really appeal to me)

 

I might just build it on a whim to try it out. I was hoping that someone else had travelled down this path and could shed some insight though. Interesting that the dimentions are so similar to the RB however.

[yo2001]

On 4G63, the wristpins are offset by 1mm toward exhaust side which suppose to suspend the pistons up in TDC longer to reduce detonation/knock.

 

I think the peak power is regulated by the intake and headflow so without changing all those components, I would think revving higher wouldn't be much gain.

[Cody 82 ZXT]

"Technology is the only replacement for displacement"

 

I like that!!

 

I think the peak power is regulated by the intake and headflow

 

I nice short runnner intake would really help wake this thing up on the top end. Torque would sure be down in the lower RPM's If this was a dedicated track car I think it would make a good combination.

 

I think one of the real issues with not trying this engine is that none of us want to lower our displacement. There's just something to be said about having a stroker engine. A stroker with turbo just sounds good to me.

[JMortensen]

How about "cubic bucks beats cubic inches"

[ToplessZ]

doug did anything have to be done to those dodge 2.2 pistons to fit. were they forged from the factory or custom? what year 2.2?

[Doug71zt]

Jared - They were Direct Connection/Mopar Performance pistons, I will try to find some specs for them - Can't remember if they are 87 or 88mm bore. They were reasonable - much less than my custom Ross pistons. I don't know if MP makes them anymore as a lot of D/C stuff is out of production.

 

I'll have a lookie.

 

Doug

[ToplessZ]

good keep us posted. Id like to hear more ideas. Always good to see more options. I just may try and do this for the heck of it since I already have the parts

[DAW]

Mine's the car with the "virtual 454" badge on the fender.

 

Drax, if you're looking for something unique in your Nissan L6 build, forget the F54 block. "Short block" takes on a whole new meaning with the L18, L24/26/28 engines as they are vertically challenged if any significant amount of stroke is used because you end up with a lousy rod/stroke or impossibly low compression ht. piston requirements.

 

So what's the unique approach? Explore the LD28 block. Look at the history and evolution of the L18. Nissan stroked the L18 from a "L28" stroke to 86mm (just a bit more than the LD28 stroke of 83mm). In order to do this, they were forced to increase the L20B block ht by something like 19.7mm more than the L18. That is exactly what they did to the L28 block in order to preserve some reasonable rod/stroke for the 83mm stroke LD28 engine, they increased the ht of the block by the same amount. You have all the room in the world with the LD28 block to build some great rod/stroke combinations.

 

Adaptation of the block has some challenges but they are really fairly minor. I've written about this hybridization of the LD28 engine to high performance gasoline-fueled use several times on this site over the past 3 years or so. Search it out. If that doesn't pan out, then I'll lay it out again if you're interested. There are many approaches for a wide range of budgets. In my opinion, this is the most undersung, least-explored territory of L6 engine building and the most logical Nissan-engineered solution of going from a 79mm stroke to an 83mm stroke in the L6, DAW

[Kennysgreen280zt]

DAW, have you looked into how much of an over bore the LD motor will take?

 

Ive mildly been hunting for a LD block to play with, the last one I saw was left at the junkyard after I pulled the crank. I remember reading the posts about turing the LD motor to gas, but it was after that block was LONG gone. Oh well, sure another one will show up someday.....

[Drax240z]

An interesting notion DAW, I will look into that!

[Guest bastaad525]

20psi of boost with no intercooler... just from a better rod/stroke ratio and 7:1 CR??? SIGN ME UP!!

 

 

Seriously... does the rod/stroke make THAT much difference in avoiding detonation? I wish someone had told me that earlier when I was putting this motor back together... would have had no problems swapping in L24 rods/crank... the darn things are pretty plentiful since everyone wants L28's.