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Update on B23 Stroker Engine

Deck Height

Well, that's how you learn.

I copied Dave Barton's specs, essentially, because A) he seemed to have everything worked out and B) his numbers were easily accessible and presented in a manner that seemed friendly and advisatory.

Maybe I should have built for more squish. I didn't know then and I'm learning now.

I have heard the rationale (a la B23ET) that it's better to go with more static compression and less boost. At this point, since the pistons are being made, my only options are to shave the head or block to make a smaller combustion chamber if I decide to go with a higher CR. Just as a what-if, I guess shaving the block would be a better move since it would give more squish and more CR? If I then wanted to drop the CR back down, I could have a little removed from the pistons at the machine shop, too, right?

Stealth FI, I appreciate your comments even if it does seem that I'm disappointing you by not having fully understood your copious previous efforts to bring the merits of tight squish to the fore. In other words, there was just too much information there to comprehend all at once. You say I can do whatever I want; it's my engine. What would you do in my place at this point? Since you've gone this far, just let me know what your straightforward recommendation would be knowing the dimensions that are built into my engine at this point. Again, I'd appreciate it. And, as you'll conclude your recommendation, I can take it or leave it, but I'd really like to know what it is.

The engine's not set in stone at this point. As I see it, it'll have lots of displacement (2600+ cc), should make better torque down low due to longer stroke, should be fine to rev to 6000 rpm, and should be fairly bulletproof considering the beefiness of the crank and the sound sonic check I had done. It seems like if I'd understood squish better, I might have opted for zero clearance between top of piston and top of deck. I also might have decided to run a slightly higher compression ratio. In fact, the settings that I have now involve a lower piston-to-deck distance than Ross Pistons recommended. I think that with the 30/1000's overbore, I'll have slightly better flow out of the valves than a stocker, too.

In any event, I'll dyno the car before and after the new engine goes in so we can make some comparisons.

Thanks, everyone, for your input. It gets a bit contentious at times, but I still have the opportunity to build this engine for its optimum power, so I definitely welcome your comments.
 
okay...

I will try to put together something of an assessment/evaluation/recommendation.

That will take a few days; I am in the middle of a coupla things.

I will do this from the perspective of just looking at what is there. I am not going to do it from a derisive or judgemental viewpoint: that would be a waste of both our times; but more along the lines of looking at things, and trying to explain what I see that causes me concern, and why.

A lot about your motor is set in stone because you have already spent the money on things. I am not going to try to play Monday morning quarterback; that would also be pointless and useless.

We'll see how it goes.
 
what I see...

for comparisons...

engine.......................B23FT...................B230FT.............AQ151.................RD26+

stroke........................80mm....................80mm...............86mm..................90mm
................................3.149in..................3.149in.............3.385in.................3.543in
[radius]......................1.5745in................1.5745in...........1.6925in................1.7715in

rod length...................145mm...................152mm.............152mm.................155.575mm
[CtoC]........................5.708in...................5.984in............5.984in.................6.125in

comp height................46.4mm..................39.7mm............36.7mm................30.55mm
[WP CLto crown]..........1.825in...................1.562in.............1.444in................1.203in

rod stroke ratio.............1.81:1....................1.9:1................1.76:1.................1.72:1


for reference, a chevy 350 has a rod stroke ratio of 1.63:1 [5.7in rod/3.48in stroke]


As I stated, I would approach this from a viewpoint of what is there; and what I see as concerns. Others may not view my concerns as important; no problemo.

I have three concerns primarily:

...the very shortened compression height; requiring a narrowed ring belt; reduced ring land width between the rings and above the top ring; and the raising of the ring pack so much closer to the crown.

...the lack of squish clearance being within the effective squish zone.

...the over-emphasis of rod stroke ratio at the expense of the compression height.

To explain briefly:

the reduced ring belt width and the raising of the ring pack way up the side of the ring land portion of the piston will increase the operating temp range of the top ring considerably; very likely doubling the temps that the top ring will forced to deal with. The narrowness of the ring lands between the rings and between the top ring and the crown is a potential weakness: less material for rigidity and heat absorption.

the squish clearance, or lack thereof, has been mentioned priorly. That can be addressed either via a resufacing of the block deck, or by using a HG that has a thinner compressed thickness. Ans as stated, a dummy assembly is advisable before that choice is made.

the over-emphasis of rod stroke ratio...a description that will probably earn me vitriolic disapprobation...led to the first area of concerns.

*****

Rod stroke ratio, and whether or not it is important, valid, helpful, or worthy of consideration when configuring a boost motor's internal geometries is a subject that has been and will continue to be debated and argued for the forseeable future, IMO.

In this discussion, I am going to refrain from getting into that debate. The choice of rod length and stroke, and the resulting compression height has been made.

*****

The reduced comp height is where any problems might occur; as I see it.

And yes, I am aware that such a tight comp height is not uncommon nowadays. But I think that that is more common in NA motors.

A boost motor makes lots of heat. Raising the ring pack exposes the rings to more heat. Perhaps there is a way to address the situation, to reduce any negative effects of higher ring op temps.

I would suggest retrofitting of oil squirters to add in piston cooling. That is not necessarily an easy mod; but in the interest of helping the pistons handle the heat that they are going to see, I think it would be beneficial.
 
RedDragon said:
That I will, MJ.

I also put two sets of functional louvers above where the turbo is and deleted the passenger's side high beam to make an air intake for the engine compartment and cone filter.

I've only driven the car once since then, but when I pulled over and kept my electric puller fan running, serious hot air was escaping from the louvers.
Click to expand...

I was thinking something along the same lines. Underhood heat is so high on a turbo that it would seem like a win win situation if one could deal find a way to vent heat out of the engine bay. My only question or concern with putting a vent or louver where you put it is rain. Not while you're driving or course. Does it leak back into engine bay?
 
Two threads

Well, there are now two threads going here.

With respect to the louvers and venting of the heat from the hood ... I'm not worried about rain's getting into the engine compartment. I mean, it's an engine. So what if it gets wet? It gets water sprayed up from the road all the time. Some water might drip onto a hot turbo housing or exhaust manifold, but I don't think anything is going to crack.

With respect to the shortened compression height and diminished compression ratio ... Thanks for your comments, Thomas. They are well considered and when it's time to rebuild the "RD26+" engine, I may go with a higher compression ratio, but if the pistons are still sound at that time (3 years? 5 years? more?), then I probably won't change them, but if the pistons do seem to take too much of a beating, then I'll go with a shorter rod and more compression height.

At this point, I think I'll run what I brung. If I don't like my low-end power, I can work out a solution in the future. Before I had considered doing a stroker engine, I had already modded the car to handle big boost: 3" exhaust, bigger turbo, Evans racing coolant, browntop injectors, rising rate fuel pressure regulator and NPR intercooler. With that in mind, when it was time to design this engine, I opted for the lower static compression, higher boost method since many of the components were already in place. Future plans for the engine, regardless, are a stand-alone computer management system, mainly to control spark advance, giving more at the low revs and cutting it back at high revs/high boost.

In any event, it's all fun and it's enjoyable learning about how to engineer an engine. If for some reason, I am not enamored of this build, I will change it down the road.

For what it's worth, Eric at ipd and I talked on the phone about this project before I got started on it and he told me he had gone with the higher CR, lower boost plan on his own car. He's making 360 ponies, so obviously he's doing something right, maybe due in large part to the wicked head he's running. I'll dyno my engine before and after the RD26+ goes in and we'll see how mine turned out in comparison. I think the numbers might be beneficial to all.
 
Pistons? Pistons?

Still waiting for pistons. I check for the UPS truck every 5 minutes to no avail. This project is almost done. Gotta go ... I think I hear a truck.
 
Adult signature required

Ugggg, I wasn't home when the pistons came to my house. I'm having them redirected to my work, so they should be in my greasy hands by Monday. Getting close ...
 
Pistons?

Still no pistons. Hopefully today. Hmmm, 12 days for shipping from California to Colorado? Maybe the UPS driver used them for his delivery truck?
 
Mars has pistons, needs women

The pistons are here. Heads by Paul is mocking up the block. I think I'm going to zero-deck the block for more compression and more quench. That's the plan, Stan. I shall keep y'all posted.
 
I am fond of more compression and more attention paid to management for my boosted motor. Of course I always run racegas. 100 octane minimum.
Your engine should be a hoot.
JL.
 
Head gasket

I've gotten some info back from the machine shop and I made a decision about what to do with the compression.

Since my Cutting Edge head gasket is 50 thousandths thick and since you need 40 to 45 thousandths to get into the good squish range, there simply is no way to run this gasket and have a good quench engine.

Unless ...

... you have the pistons sticking up out of the top of the block and into the open space that the head gasket occupies (negative decking or positive decking?).

Anyway, that would work as long as I always ran a head gasket that was 50 thou thick. What happens when I need to rebuild and I can't find another Cutting Edge? Hmmm. I'd be screwed then.

I think what I'm going to do now is simply run a thinner head gasket. It essentially increases my compression, puts me in the quench area (depending on thickness) and lets me repeat the build when I need to repeat it.

As I keep saying, I'll keep you posted.
 
RedDragon said:
Since my Cutting Edge head gasket is 50 thousandths thick and since you need 40 to 45 thousandths to get into the good squish range, there simply is no way to run this gasket and have a good quench engine.
Click to expand...

Are you sure it's 50 thousandths compressed or uncompressed? Peter Linssen told me the CE gasket is .040" compressed.
Dave B.
 
Ring packs

There has been some discussion about the rings being too highon the pistons. I don't think this is any concern. Most "modern" engines are using VERY high ring packs on hypereutectic pistons and NO knock sensors. Even when boosted by a turbo or Roots blower the pistons (rather ring-lands) are supprisingly durable. When they fail, it is almost always due to pre-ignition (knock). Since most every Volvo has a good and functional knock sensor, AND more importantly the engine in question is using good quality FORGED pistons, the ring lands and pack height are a non-issue for durability, and a huge improvement in performance and emissions.
 
Still need head gasket

Well, I had the machine shop mock up the block and they told me the pistons are 10 to 15 thousandths down the hole. So, an ideal head gasket would be 30 thousandths thick, giving me a 40 to 45 thousandths quench height.

Does anyone know of a 30 thousandths compressed thickness head gasket? My mechanic is trying to track one down.

TIA
 
http://www.headgasket.com/

Not sure if you want to try a copper gasket or not. But its an idea. They come in a variety of thicknesses.

You might be able to get creative and put a rubber o-ring around all the water passages. No leaking problems then.
 
You could have the block decked so that you can use a standard headgasket. You may have to use an adjustable timing gear to realign your cam (Dale's --245gti-- cam gear comes to mind).

RT
 
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