L28 Frankenstein build questions

[DPG]

I have been searching like crazy but have not found anything about this possibility. I am building an F54 block, using an L24 Crank and L24 Rods, but I want to do 89mm pistons. The math works out on an engine calculator using an L28 piston height of 38.1mm (or slightly shorter), but I just want to be sure I am not missing anything. Any tech info I should be aware of that would make this not possible? Maybe the simple physics doesn't work for some reason? Any help would be great guys, thanks in advance!

[ttodhunter]

Soo, a destroked L28. One of the problems I see in the setup is that Nissan factory 89mm pistons don't come in 38.1mm pin height(that I know of). So, unless you were going custom forged, you would need to re-use 86mm's. By my calculations, this would give you slightly less than 2.6L with a 8.25CR using a P head.

 

Are you doing this for a better rod/stroke ratio? What is your goal for the build?

[DPG]

You're correct, they will be custom pistons. I am doing it for a motor that revs much faster. I'm not looking for an exceptional rev limit, just 7500, but I want the motor to spin as fast as possible. From my calculations the engine would be a 2.75L and have a compression of about 10.9. I would do a pin height of 38mm instead of 38.1. Plus it would be cool since I can't find anyone that has done this before

Edited April 26, 2012 by DPG

[DPG]

And the head is an E31 with 45/36 valves and a custom cam from Isky that is still being specced out. Nismo .6mm head gasket.

Edited April 26, 2012 by DPG

[Leon]

Are you doing this for a better rod/stroke ratio? What is your goal for the build?

Please say no. Building an engine for the sake of r/s ratio is like choosing your wife based on the proportions of her toes.

 

Many have fantasized about his kind of build, and the conclusion is always that there is no good performance reason behind it. If you're building it for the sake of building it, have at it. But don't expect it to perform better than a fine-tuned L28.

[DPG]

Please say no. Building an engine for the sake of r/s ratio is like choosing your wife based on the proportions of her toes.

 

Many have fantasized about his kind of build, and the conclusion is always that there is no good performance reason behind it. If you're building it for the sake of building it, have at it. But don't expect it to perform better than a fine-tuned L28.

 

You're right, I don't have any expectations for it to perform better, I really want the characteristics of what this motor will have compared to an L28crank/rod combo stroke build. I'm not looking for crazy power. I know I'm losing power compared to equal money I could spend, but this is what I want I just want to make sure there won't be any problems from doing this.

[Leon]

You're right, I don't have any expectations for it to perform better, I really want the characteristics of what this motor will have compared to an L28crank/rod combo stroke build. I'm not looking for crazy power. I know I'm losing power compared to equal money I could spend, but this is what I want I just want to make sure there won't be any problems from doing this.

In all honesty, and this is the stuff discussed in other threads, the characteristics of the engine will not be noticeably different from a well-done L28. Again, I'm not telling you what to do or what you're doing is wrong.

 

All a destroked engine achieves is having a slightly higher rev limit. The L28, with a lightweight flywheel and clutch combo will respond very quickly to inputs and rev plenty high.

 

You speak of the characteristics of this engine compared to an L28 but you don't mention what those characteristics are. What are those characteristics that you're trying to achieve?

[roger280zx]

What leads you to beleive there will be problems? Do you know the history of these engines? By that I mean that Nissan put (what would soon be recognized as) an L28 crank in an L24 block to create an L26. What makes you think going the other direction will create problems? You already know the pistons are the hard part... what is the hold up. DO IT

[DPG]

In all honesty, and this is the stuff discussed in other threads, the characteristics of the engine will not be noticeably different from a well-done L28. Again, I'm not telling you what to do or what you're doing is wrong.

 

All a destroked engine achieves is having a slightly higher rev limit. The L28, with a lightweight flywheel and clutch combo will respond very quickly to inputs and rev plenty high.

 

You speak of the characteristics of this engine compared to an L28 but you don't mention what those characteristics are. What are those characteristics that you're trying to achieve?

 

Essentially a lighter more responsive motor that revs higher at a greater speed. I know that the difference will not be major, but it will be enough to make me smile. Everything I have read about the difference in L24 and L28 cranks, other than stroke, has been their rev speed. I am lightening everything I can, through the drivetrain as well to get this rev speed. It may be a slight failure but it should be interesting.

[DPG]

What leads you to beleive there will be problems? Do you know the history of these engines? By that I mean that Nissan put (what would soon be recognized as) an L28 crank in an L24 block to create an L26. What makes you think going the other direction will create problems? You already know the pistons are the hard part... what is the hold up. DO IT

 

I'm right there with you, this is just my first L motor build, I just wanted to make sure I guess. Ask the people that have done it for years and all. I appreciate the push

[Leon]

Everything I have read about the difference in L24 and L28 cranks, other than stroke, has been their rev speed.

There are no discernible differences here. This is the problem with anecdotal evidence, the people that post this don't fully understand the situation. The reason people think L28s rev slower or lower is because of the cam.

 

Put a hotter cam in and rev it to 8000rpm. Forged pistons are needed for ventures above ~7200rpm.

 

I am lightening everything I can, through the drivetrain as well to get this rev speed. It may be a slight failure but it should be interesting.

If you want to go that far, the L28 rotating assembly can be lightened and balanced just as well. You'll have the response you want with more power and torque.

 

This is the point, the difference in how it "feels" is minimal if not completely negligible.

 

The only difference between the two engines would be that you'd have a conversation piece where you get to say that you built an engine using X crank, Y rods, and Z pistons. That'll about be the only difference, and if you're happy with that then build it. In the spirit of Hybrid Z, build whatever you want and whatever makes you happy.

 

However, let's be logical about this and not ignore facts. An L28 can easily give you the "feel" that you're after, likely with less expense, less time, and better performance. You can find plenty of threads with high-revving, fast-response time L28s.

[DPG]

There are no discernible differences here. This is the problem with anecdotal evidence, the people that post this don't fully understand the situation. The reason people think L28s rev slower or lower is because of the cam.

 

Put a hotter cam in and rev it to 8000rpm. Forged pistons are needed for ventures above ~7200rpm.

 

 

If you want to go that far, the L28 rotating assembly can be lightened and balanced just as well. You'll have the response you want with more power and torque.

 

This is the point, the difference in how it "feels" is minimal if not completely negligible.

 

The only difference between the two engines would be that you'd have a conversation piece where you get to say that you built an engine using X crank, Y rods, and Z pistons. That'll about be the only difference, and if you're happy with that then build it. In the spirit of Hybrid Z, build whatever you want and whatever makes you happy.

 

However, let's be logical about this and not ignore facts. An L28 can easily give you the "feel" that you're after, likely with less expense, less time, and better performance. You can find plenty of threads with high-revving, fast-response time L28s.

 

I appreciate all of this information. I will have to rethink everything and decide.

[Leon]

Here are a couple of threads to wade through, if not just for the videos:

 

http://forums.hybridz.org/index.php/topic/87781-400hp-na-32l-how-is-this-happening/

 

http://forums.hybridz.org/index.php/topic/90037-japanese-na-l6-400hp-how-they-do-it-pictures-ive-found-etc-not-56k-safe/

[Gollum]

Since when is stroke the determining factor of revability? Nascar motors rev faster and easier than my L28E...

 

Brian Blake (1fastZ) made a 3 liter L motor that revs and revs down about 5 times faster than any L motor with the stock flywheel I've seen. It was almost like modified honda B series fast, maybe even faster.

 

Lightweight slugs combined with a lightweight flywheel + clutch setup will do more than any stroke modification. Get the crank well balanced and 9,000rpm can be in your future, even 10,000 honestly.

 

You can also lookup MONZTER's 240Z build up. It's a 2.4 liter that made probably around 200whp and revs like a mo-fo.

 

Personally, if you're trying for the ultimate "rev build'' you should be using the longest rod you can get to combine with the shortest pin height. I'd say 70% of your time and energy should be going into the pistons. Every gram is worth something. The lighter you make the slugs the less stress on the rods and the lighter THEY can be in turn. The less the reciprocating mass the more you can play with the crank. Then wrap it all up with a 10-12# flywheel and you'll have something that's nearly impossible to clutchless downshift.

 

And all that said, I personally don't see the point other than "just because" which is always the right reason. I just have to ask, have you actually ever driven just a basic L24 or L28 with a VERY Lightweight flywheel?

[NewZed]

The yellow and red paint is at a lower RPM on the 280Z tachometer than on the 240Z tachometer. Therefore....

[Leon]

Since when is stroke the determining factor of revability? Nascar motors rev faster and easier than my L28E...

 

Brian Blake (1fastZ) made a 3 liter L motor that revs and revs down about 5 times faster than any L motor with the stock flywheel I've seen. It was almost like modified honda B series fast, maybe even faster.

 

Lightweight slugs combined with a lightweight flywheel + clutch setup will do more than any stroke modification. Get the crank well balanced and 9,000rpm can be in your future, even 10,000 honestly.

 

You can also lookup MONZTER's 240Z build up. It's a 2.4 liter that made probably around 200whp and revs like a mo-fo.

 

Personally, if you're trying for the ultimate "rev build'' you should be using the longest rod you can get to combine with the shortest pin height. I'd say 70% of your time and energy should be going into the pistons. Every gram is worth something. The lighter you make the slugs the less stress on the rods and the lighter THEY can be in turn. The less the reciprocating mass the more you can play with the crank. Then wrap it all up with a 10-12# flywheel and you'll have something that's nearly impossible to clutchless downshift.

 

And all that said, I personally don't see the point other than "just because" which is always the right reason. I just have to ask, have you actually ever driven just a basic L24 or L28 with a VERY Lightweight flywheel?

Exactly! It has very little to do with r/s ratios and strokes. It's about the weight of your reciprocating parts. The rev limit definitely has something to do with stroke length, r/s ratio has a relatively minor effect.

 

The yellow and red paint is at a lower RPM on the 280Z tachometer than on the 240Z tachometer. Therefore....

The prevailing logic...

[Gollum]

The yellow and red paint is at a lower RPM on the 280Z tachometer than on the 240Z tachometer. Therefore....

 

Quote of the month!

 

That strange colored paint never seemed to stop me though. That was the best thing about driving a B16A CRX with the stock tach, watching the needle BURY itself into the red and then bounce off the needle stop, and know that you STILL have RPM to go!

[DPG]

Since when is stroke the determining factor of revability? Nascar motors rev faster and easier than my L28E...

 

Brian Blake (1fastZ) made a 3 liter L motor that revs and revs down about 5 times faster than any L motor with the stock flywheel I've seen. It was almost like modified honda B series fast, maybe even faster.

 

Lightweight slugs combined with a lightweight flywheel + clutch setup will do more than any stroke modification. Get the crank well balanced and 9,000rpm can be in your future, even 10,000 honestly.

 

You can also lookup MONZTER's 240Z build up. It's a 2.4 liter that made probably around 200whp and revs like a mo-fo.

 

Personally, if you're trying for the ultimate "rev build'' you should be using the longest rod you can get to combine with the shortest pin height. I'd say 70% of your time and energy should be going into the pistons. Every gram is worth something. The lighter you make the slugs the less stress on the rods and the lighter THEY can be in turn. The less the reciprocating mass the more you can play with the crank. Then wrap it all up with a 10-12# flywheel and you'll have something that's nearly impossible to clutchless downshift.

 

And all that said, I personally don't see the point other than "just because" which is always the right reason. I just have to ask, have you actually ever driven just a basic L24 or L28 with a VERY Lightweight flywheel?

 

I have driven a couple 240's with a lightweight flywheel and it does make a difference. My experience is limited so I can only go off of what I read on forums and research. It is hard when everyone says they know the best. I appreciate the information and will definitely take it into consideration.

[Leon]

We are not purporting that we know best. We are providing you with facts supported by empirical evidence. Others like to go on so-called "theory," and use it to make all sorts of proclamations. In other words, bench racing. Look at the evidence and judge for yourself.

[DPG]

We are not purporting that we know best. We are providing you with facts supported by empirical evidence. Others like to go on so-called "theory," and use it to make all sorts of proclamations. In other words, bench racing. Look at the evidence and judge for yourself.

 

I understand. People throw out many things, some that they portray as evidence sometimes that can make it hard. What you are telling me is straight forward and I thank you for that.