I'm perfectly chilled thank you. I color this a healthy debate, I just don't think you have clue one what killed the rings in my motor, and I do, I drive it, & I work on it. Yes I do know what my head flows, and yes I do know my cam specs. I've never been exposed to a bunch of kids saying "oh, your rod ratio sucks, you won't make power", but if I were I'd tell em they're full of it too. R/S ratio IS worth thinking about as it effects allot more than just longevity which clearly most of us are willing to sacrifice at least in measure. Your stroke length and therefore rod ratio effect cylinder filling and optimal head ports as well as longevity. Think about the vacuum created as a piston moves downward on the intake stroke and then explain to me how stroking a motor is not going to change cylinder filling and optimal head porting. The optimal R/S ratio is 1.75 BTW, and no too high is not good either, but that's not the topic of this conversation.

 

I don't think there is anyway to overstress R/S ratio, anymore than there is any other critical aspect of engine design. The term "work" is relative. Yes a low R/S ratio can "work", it's the how long and at what peak RPM that is open for debate.

You could have a happy medium. Bore and stroke a motor, but it'll cost a fortune and be less reliable than a motor that's been bored to the maximum IMO. I'd rather sleeve a B18C1 and go with 84mm slugs as my route to more power. If money grew on a tree in my backyard I wouldn't mind trying to stroke that bored out GSR motor, but I'd also be prepared to re-build it more often after I did, or I'd lower the rev limit.

 

i thought b 16 deck hight was shorter. it gets its rs ratio from shorter crank throws.

 

B16 piston to deck height is .02"
B18C1 & C5 piston to deck height is .03"

 

they didnt destroke to increase power they destroked to stay within class rules.

 

yes, they destroke it to stay within the rule but with the better R/S ratio, it can produce better power band and also last longer in race. i have seen so many time the 2.0 B18 broke down in 10 laps in 95 JTCC(hattori's car).

 

"R/S ratio IS worth thinking about as it effects allot more than just longevity which clearly most of us are willing to sacrifice at least in measure. Your stroke length and therefore rod ratio effect cylinder filling and optimal head ports as well as longevity. Think about the vacuum created as a piston moves downward on the intake stroke and then explain to me how stroking a motor is not going to change cylinder filling and optimal head porting."

Wait, lets think this through. What you say is correct. BUT, if you are going to stroke your motor, you are most likely going to match the head flow and the cams. So you have just washed away your argument, save the longevity aspect, which I agree on. BTW, what does your head flow? I would like some comparisons. Thanks!

 

First you say this:

Then you say this:

First you state R/S doesn't matter in any practical sense then you agree with me it needs to be considered when you're matching your head & cams to the bottom end. Now **I'M** washing away **MY** argument?!? Methinks thou art confused sir.

 

The best thread ever!

 

I lightly polished & cleaned up my GSR head last time I had it off, it has not been ported. A stock GSR head flows roughly 153CFM @ .5" lift w/ 10" @ 66 degrees. The Crower 63403 cams are 12.04 mm lift & 267 @ 1mm dur on the intake cam & 11.84 mm lift w/ 257 @ 1mm duration on the exhaust side. The more important number is ABDC of course and it's 46 degrees. The cams longer intake duration is costing me a bit of compression, which I've minimized by advancing the intake cam. My next move is to bump compression to 11.7:1ish with JDM ITR slugs and high compression valves. I'm looking for just over 200WHP before porting and tuning.

 

Yes it is an interesting debate, but I'd like some more experienced engine builders to weigh in and less people with theories that think the laws of physics will take a powder just for them. It's all well and good to debate the importance of rod to stroke ratios and engine geometry, but some people that have only marginal experience with engine building, cite full race car buildups that have little relevence in the daily driver arena. When you want your car to run well and run everyday for years without rebuilding you have to follow rules you can get away with bending when you're building a car to do 10 passes on the 1320 between re-builds.

 

That is such a true statement. Man you really know your stuff. Keep it coming. I feel like I'm at home getting schooled...

 

The main point in this arguement that I wanted to prove is RS ratio isn't that big of a factor in making power, but if you want a 150K plus engine worry about the rod ratio. I think that a stroked engine with a 1.4-1.5 RS ratio can see 100K with a moderate driver.

The guys that destroked the H22A porbably were looking for an engine that could sustain high RPM for long periods with less vibrations. This would make the engine more durable in that situatrion, but in street strip conditions I doubt that it will be a big benifical factor unless you only use 1st gear every where you go.

AS for the piston ring wear situation. IT isn't R?S ratio, or oilchanges it is the engine abuse. An engine not designed to see 9K frequently will make more heat at the temp in the cylinders (since it is not designed to remove it properly). So more heat in the cylinder with rings that weren't designed for that heat wear and break down quicker. ITs all about the heat fells!


[Modified by Bontke, 10:31 PM 10/15/2002]

 

I for one do indeed use first gear everywhere I go, at least to start out, it makes take-offs better.

Uhhh...don't you think an engine with more side loading of the pistons will make more heat than an engine with less side loading of the pistons at the same RPM? Like say for one with a lower R/S ratio for instance?


[Modified by TimoneX, 10:00 PM 10/15/2002]

 

Since I am an experienced engine builder and believe I'm correct here, but at the same time also know that I am not the only informed person on this topic, I will cite an article posted by Michael Delaney at team-integra.net.

TimoneX- Michael, aka Tuan and I have been around and around on this subject too (we both run the engine tuning forums on another board), and similiarly we haven't yet come to a good middle ground on r/s ratio importance. You should see how long the threads get with us on rod ratio importance.

Basically, my assertion stems from the beaten to death concept of r/s ratio. While its a new concept for the import crowd and specifically the online posters, its nothing new for people coming from a domestic engine background like myself. I know its something to consider, especially if one has the resources and concern for absolute package optimization, but what I don't like hearing is the all-too common long *** thread about how all important this single and honestly small aspect of engine design has become. What worries me is the focus on r/s ratio and the lack of attention paid to other, equally important aspects of performance buildups. And frankly, what control you have over r/s ratio is extremely limited for the average street enthusiast, so I personally recommend focusing on those things we do have a great deal of control over. That's what I mean by overstating its importance.

spoon_ek9- The math is a bit long, but there's a good online calculator for getting maximum piston speed as well as plotting piston movement relative to crank rotation. Click here.

Doctor CorteZ- You are correct, the B16 gets its higher r/s ratio from a very short stroke, not a particularly tall deck height. The B18C has a .35" taller deck , but the stroke is .386" taller. The B16 is as oversquare a 4 cylinder as Honda makes.

There's much more to be said here, but I think this has gotten long winded enough.


[Modified by texan, 12:36 AM 10/16/2002]

 

I've probably read some of the very debates you're referring to, he's more correct BTW.

For the most part I agree, it is beaten to death, perhaps too much so. Just the same I think this mentality that rod to stroke ratio is meaningless is silly and dangerous. You can usually find at least one newbie popping up during each in depth debate making some unsupported and brain-dead assertion that R/S ratio doesn't mean anything. I would never suggest focusing on R/S ratio at the expense of anything else, particularly since as you said it is only marginally controllable on your average "weekend hot rod". This particular thread is about this very thing however, changing R/S ratio as a means to gaining more power on a daily driven Honda hot rod. It's simply not the most optimal way to gain more power.

 

"Basically, my assertion stems from the beaten to death concept of r/s ratio. While its a new concept for the import crowd and specifically the online posters, its nothing new for people coming from a domestic engine background like myself. I know its something to consider, especially if one has the resources and concern for absolute package optimization, but what I don't like hearing is the all-too common long *** thread about how all important this single and honestly small aspect of engine design has become. What worries me is the focus on r/s ratio and the lack of attention paid to other, equally important aspects of performance buildups. And frankly, what control you have over r/s ratio is extremely limited for the average street enthusiast, so I personally recommend focusing on those things we do have a great deal of control over. That's what I mean by overstating its importance."

Thats what I have been trying to say. Thanks!

 

Yes our bro is certainly well spoken, I'll give him that.

 

"Leave r/s alone"


There is no doubt that Honda put out r/s ratios between 1.75:1 & 1.49:1, all have different output curves and are well suited for the average street enthusiast. But, some like to think the BIG. For the non-average enthusiast and high powered applications, the difference in output between r/s ratios can mean a lot.

There is a "breathing" limit to our cylinder heads, and where slower piston speed is needed. Sounds silly, right? ....

Lets take for an example a high piston speed r/s ratio of 1.40:1. Produces great torque at lower revs due to the piston speed and the "sucking effect" it has on the ports. But at high rpm, the piston speed is too fast for the valve timing events. The valve remains open for too short of a time. Ambient air can only move a certain speed without loosing its density.

There is always the possibility of increasing lift, but you'll eventually come to a limit in your valvetrain. The piston is moving too fast, that valve will have to open & close for a short period of time and yet supply enough air for the fast increasing cyl volume.

With the proper fuel, Dense air in the cylinder produces power.
Lets take for instance: Pumping a syringe in a container of water.
Let the water found in the cylinder be air.
And the bubbles found in the cylinder be "a density loss" no air.
If you move the piston too fast, you'll get bubbles in the syringe's cylinder.
If you move it slowly, you'll get a more complete fill and no density loss (no bubbles).
In this case, there is a limit to how fast water can get sucked in. Move it too fast and you will get less of it. Slower piston speed does a better job in filling in the cylinder. With that said..
There is a limit to how fast ambient air can get sucked in between the port and valve.


The above plot is fake. 1.45:1 rod/stroke.
Long stroke, and with the high piston speed & short valve timing events, air can no longer fill in. Note the lumpy early torque, which IMO is bad for FWD.

With the proper fuel, dense air produces power. At high revolutions piston is moving too fast and wants to move air fast, but it cant.. the valve opens & closes along with the high piston speed, and dense air can no longer get in the cylinder. it's is running out of air, because it's out-running air.


The plot above is also fake. 1.80:1 rod/stroke. The benifits of going with an ideal rod/stroke of 1.75:1 or higher, will decrease the side loading on cylinders, and the bearing load is more distributed throughout the surface instead of wearing at one point. Also, at high revolutions, the valve opening and slower piston speed is enough for the air to fill in the cylinder without losing its density. Keeps on producing instead of losing


[Modified by Quick 200k Mile Motor, 8:24 PM 10/17/2002]


[Modified by Quick 200k Mile Motor, 12:00 PM 10/26/2002]

 

I personally think that Texan is full of.... just kidding. In all honesty, I've gone both ways (being professional about this) on this subject and now lean towards full tilt what Texan is saying. I've read the thread in full, and have just a few things to add to the mixing pot of ideas being presented.

I'm a very very devoted 3rd Generation Honda Prelude guru! I've owned 3 now; 1988S, 1988Si4ws and 1989Si4ws Turbo. As some of you, or many of you depending on how diversified you are with Honda's may know, the 1988 - 1991 Preludes utilize 5 diff. engines; B20A (88-91 JDM), B20A3 (88-90 Carb US), B20A4 (88-91Au PGMFI), B20A5 (88-89 US/88-91Au PGMFI), and the B21A1 (90-91 US PGMFI). ALL 5 engines utilize the same specs mentioned from Texan on page 2 about R/S ratio and Angle of attack on the cyl. wall from the 95mm stroke and 141.? Rod. ALL of these engines are typically seen, in the 3G world, at no problems till around 140K miles where you start to see smoke. Typically, this smoke however, due to "Non popular beliefe" (gathered from no one mentioning this), is 90% of the time cuased from failing Valve Guide Seals; piston rings typically last till 180K!!!

The use of 3G's was more for a sporty look when Honda got into them, but quickly realized they stumbled onto something HUGE in 1988. More 3G Preludes were sold than any other generation Prelude manufactured world wide. The introduction of 4ws made them also very popular, as did the addition of ALB in the 90's to these beauties. Problem back then was, the engines of the day weren't 200hp factory #'s across the board, and even this was a European fixation amongst manufactures overseas. Time went on, and Honda decided to up the Engine displacement and power output with the intro of the 4G's, and even later to the 5G's with both later gen's utilizing VTEC.

We all know this story very well, so I'll jump to the point. 3G Preludes are freaking old to most people, and the only guys driving them these days "on average" are teens to early 20's people. Most of these guy's/gal's get one as thier first car. Our engines aren't BAD, they just have 8 - 12 more years on them than yours do. Time will cause everything to deteriorate given enough of it. Our internals wear out (as will yours on average in a few years), and thus we seek JDM B20A's as they are dirt cheap. The Import sceen is in now, obviously, and this has created the need for power.... my fellow 3G Friends have no support from the aftermarket world.

From the Cyber point of view, I've got constaint Emails daily from people telling me that they want more out of our engines and can't cause someone told them their R/S ratio was **** poor. In actuality, our engines hold up fairly well to the 6750 redline and have done so for many more years than yours have been around. How has this extra sidewall loading on the cyl walls damaged our guide seals? If you can explain that, then I'm sure Corkey Bell himself would applaude you as you can't. 1.49 isn't as good at 1.75 or even the 2.1 + that F1 uses (though that's on a totally diff. plane). But trying to say that an older B20A(?) engine at 1.49:1 can't do anything with high hp. due to this silly r/s number is nuts.

I own a 1989 Si4ws Turbo'd B20A Prelude and love it to pieces. I'm an Automotive Tech, and have held every bolt, nut, and screw manufactured for these 1988 - 1991 Preludes in my bare hands; and built a good 5 - 6 fully functional 3G Engines (one for a boosted application of more than 10psi). From a stock current run of an 88 Si, you'll see 101 on a dyno. Turbo bolted on, no added fuel pump, no IC, 5.5 psi, and you have about 178whp. take that same engine and run it for 2+ years at shifting ranges well above 6K rpm's. This engine was just taken apart, and aside from normal wear (being very serious, especially from the bottom end), the only problem was an accesive build up of carbon in the combustion chamber. I'd like to blame this on a poor ignition system myself, but who knows.

Point is, B20A's are older indeed. The R/S number obviously, from a standpoint of knowing NOTHING about it (say you were a GM Tech (Ford's have already been discussed)) ... it's not that pretty. But once you dig in and begin to understand that though it's bad numerically, it's NOT what's killing the engines! It's Age more than anything. Even a JDM engine with only 30 - 40K miles on it still has time on its side. My point is, try not to judge an engine or it's performance capabilities by it's figures (many have gotton into a lot of trouble doing this with women in the past). Kinda like saying, don't judge a book by it's cover.... you may just get suprised.

BTW Making sure your vlave train can handle your induced RPM's is CRUCIL! Valve Float and or Coil Bind will take an engine faster than side wall loading and piston speeds inside a combustion chamber.

Ps. Why hasn't anyone mentioned Pinning the Block as an option to help out with this side wall loading topic? I've had this done with every block thus far and have been very impressed with each engine built.

Dustin
http://dustin_palmer.tripod.com/home.html


[Modified by B20A5T, 3:38 AM 10/18/2002]

 

I had 2 gen 3 ludes(both '88) right in a row. Great cars without a doubt, you'll get no argument from me. The only thing I would stress is the relatively low redline on those engines. Perhaps the force on the sidewalls increases dramatically with RPMs. It wouldn't be difficult to imagine more piston & crank speed creating more vibration and significantly more stress on the cylinder walls. I know my 2nd lude burned some oil at 200k ish, though less than my G3 teg is now at 83k miles. I did not modify the Prelude at all however, and the teg is substantially different than stock. I'm not sure that any conclusions can be drawn about R/S ratio from any of this. I'm fairly confident in assuming that the increased redline and increased intake charge on my G3 teg contributed to the early failure of my piston rings. Obviously I couldn't see exactly what was happening inside my engine during this time, but how many stock B18C1 engines require new rings by 77k miles? I'd guess not many, and please noone bother telling me about improper break-in and lack of oil. It simply never happens with my engines. I certainly don't baby them when I drive, but I never never skimp on babying them on maintanence days. Would it still need new rings if I had a more "optimal" R/S ratio? I don't know, I can only speculate. Perhaps I'll know more when I get it all apart.

 

Low RPM redline because the head/intake/exhaust won't flow good enough at a higher RPM. And side was stress from a low RS ratio won't split the block apart.

Would you say a straight 4 has less sidewall stress than a flat 4? I am trying to imagine this stress. It doesn't seem likely that the piston would rub one side harder that the other, the force of combustion is placed on the piston forcing it down....not to one side, right? So how would changing the RS ratio effect pistion side loading?

 

The force of combustion is placed on the piston down and then through the rod at an angle towards the crankshaft. Becasue the rod is pushed at an angle, it pushes right back at an angle, drving the piston into the cylinder wall.

 

Good to see some actual valid points on rod ratio, something hard to find.

First, I want to touch on a topic brought about by Bontke , about how the engine wear, particularly on the cylinder walls is not effected by oil change interval, or side loading. Appropriate oil drain interval is imperative for any engine, as once an oils viscosity index improvers are deteriorated then of course the viscosity of the oil rapidly decreases there after. When this takes place cylinder wall scarring starts to surface due to the fact that the heat generated by all the moving parts of the motor is able to impact the integrity of the oil sooner and at a faster rate due to the decrease of the amount of entropy increase necessary to trigger the activation energy of the molecules protecting the cylinder wall deterioration. No, I’m not a chemist. But I recommend http://www.bobistheoilguy.com

Another thing that was said was about the reason for the designing of the H22A destroker kit and motors of the like. I agree with the fact of side loading and the benefits to be placed on the motor by the decrease in it. But as far as race engine design goes, for full blown racing motors, utilizing the longer rod allows for more repetition of the same effect (driving force of the wheels) and power production due to the ability to design the cam with the piston speed in mind and design the piston speed with the cam in mind.

Also, in the European touring league that the H22A destroker Accords are raced in, engine displacement is limited to two liters in the class they compete.

B20AST , what are the projected limits as far as boost goes (that you have actually seen hold) on the old B20 and B21 stock bottom ends?

Oh yea, Bontke , as far as the flat four end side loading goes, the natural force of gravity can be deminished by crank rotation, crank harmonics, and combustion direction.

Quick 200k Mile Motor , thanks for telling me about the thread, one thing that you touched on was the reason for the rod ratios as they are from the factory. One thing I want to add to this is that typical engine design about deck height and rod length. From the factory, as well in many, most engine designers are out to create a light and compact engine package that is easier to fit in compact engine bays as chassis design, ergonomics, visibility requirements, and new impact regulations hinder space availability. As well as the aspect of designing a motor that the typical driver can utilize as you mentioned.

And yes, this topic is beaten to death, but even though the majority of us think this topic is beaten to death, most of us still enjoy to discuss it, as it is still one of the broader available “technical” discussions around.

 

Here is like dinner on the subject...

For a street car, without a doubt, 100% in my opinion the best stroke and bore for a motor that is WIDELY available would be:

87.2 MM CRANK Stroke. (GSR)
85 MM Bore

And it will rev to 10,000 RPM, and peak about 9k with JUN 3's. Power will hold good to 9500, shift at 9500, and have a totally flat looking HP curve.

+ Since the car is going to make about 245 WHP and 150 Torque, your not going to have too many traction issues.

Note Erick's Racing has this setup, well, very close to it.

Notice how much easier it is to drive this 150 lb of torque, flat Hp curve motor is..

Take the large motors out now.

99 MM stroke is common I see ALL the time, and Dyno...101 MM stroke Crank common...Which i dyno... 95 MM stroke crank...

And they all have 1 thing in common. Massive wheel spin, from the HP coming on too fast and too steep.

You have only 1 major benifit to the stroker motor: COMPRESSION. Compression makes HP for sure. Lots of it. HOWEVER, even with a deck plate, and superior R/S ratio, the stroker motor still can't breath well, like a GSR motor, and will peak WAY lower than the GSR motor.

So, you get a peak of around 8200 or so with the stroker, with deck plate. YOu get a peak of around 9k with the GSR motor. Thats 800 RPM, or in Hp terms you usually get around 15-20 WHP every 1000 RPMS.

So since you can't peak as high as the GSR motor, your going to have to make more power by compression. So you get slightly more HP PEAK, but still less AVERAGE HP than I have seen with a GSR crank. because the damn stroker graph is so steep. Its going up very fast.

Thats hard to drive. And you need special gearing for that.

So, in conclusion, the stroker is way more expensive, and of course, way more unreliable, and it will peak lower even with a better R/S. So you have higher compression to make up for that. But you still have lower average HP in my opinion.

I base this opinion from Dynoing Ericks Racing's Car, and many, many Stroker motors that run very fast too with superior HP.

The stroker motor had 20 more WHP, but less average HP in the zone. And it ran almost 1/2 second slower than Erick's car, near the same weight.

I am not against stroker's completely, I just think they take alot more skill to drive, and alot more research on the car to hook up right.

My experiences, not to be taken as facts, just observations from years of being right in the middle of it all.

Thanks guys.

Jeff