Question about stroker...

[stockfornow]

Hey, I got couple of questions. How much of bore should be done to the engine in order to make it a 2.3L is it 86mm .040 considering the stock ones are 85mm. Or am I missing something, if I do, can someone teach me how this works, the calculations? And another question if I get the switchable 2-4 wheel drive trannsmission, would I get better gas mileage on a FWD? Thanks for all your help. I'm really getting now into this cars now, I want to be able to build mine for the next summer. Thanks, again to anybody.

 

[donmagicjuan]

Now that I'm finished stuffing my face with a pencil in hand, I'll post up my calculations. The link in this post is to a scanned written document, so I apologize if it's a little hard to read. You'll need a basic understanding of vector math and relative motion analysis to keep up, but nothing is too ridiculously advanced.

The max piston speed occurs when the piston is 90 degrees from top or bottom dead center, so everything is based on that. Keep in mind that this is only a kinematic approach that does not take into account the stresses involved in the various components. Such an analysis would require calculations involving max acceleration of the pistons, knowledge of individual component masses and dimensions, as well as estimates of peak cylinder pressure values and locations, yada yada yada. The bottom line is that such a complicated analysis would be slightly beyond the scope of the question asked. Since we're limiting the discussion to the wearing of the piston rings and cylinder walls, this approach should suffice.

The end result is that equivalent RPM for a 2.0L engine is roughly 1.1364 times greater than a given engine speed for a stroker engine (in terms of max piston speed only). You'll notice that this coefficient conveniently corresponds to the ratio of the two crankshaft radii (50/44). This is not a coincidence. In fact, any two engines can be related in this manner when only the crankshaft lengths are known. But, for those of you that require proof, have a blast: http://www.putfile.com/pic.php?img=3366902 (it might be easier to see by right-clicking and saving it first, then opening with a program that allows you to zoom in).

 

[spyderturbo007]

You'll need a basic understanding of vector math and relative motion analysis to keep up, but nothing is too ridiculously advanced.

Wow, I haven't been exposed to that since I finished my Physics minor in 2000.

Nice to see that again, I've always had a weird love for Physics. It's amazing that I still understand all of that after being away from it for almost 6 years.

 

[MyBeatGSX]

Thanks for doing all that math and explaining. So the difference doesn't appear huge on paper, but the problem is that we don't have anything to compare it to. 1.1364 sounds like nothing, but apparently its enough that people don't like reving these things past stock. I'm on my way out the door so I didn't look at your calculations in detail, but at any point in there did you calculate actual piston speed in ft/sec? That's something we could easily compare engine to engine. I'm thinking of comparing different engines, ones with known good piston speeds (F20) and ones with known horrible piston speeds (QR25). These can easily be looked up online without needing to calculate more.

 

[Splitpi]

And off the topic question, is this a good deal:
http://www.importevolution.com/prod...=3629&osCsid=14fcab357b7d5d3a1a2a3509f6b94ad4

not a knock off or anything?
Any help would be really appreciated. (Sorry for a long post)

Yes its a great deal. I met with Ryan from Import Evolution to help me with a boost leak problem. While there, he showed me that setup. Everything is included in the kit and and the Aeromotive does follow boost. You cannot go wrong.

 

[donmagicjuan]

Tyler,

I did one calculation of actual piston speed for a 2.0 @ 3500 RPM, which turned out to be 16.1 m/s, or about 52.9 ft/s. Calculating the max piston speed for both at 7200 RPM yields the following:

2.0: 108.8 ft/s

2.3: 123.7 ft/s

Keep in mind that cylinder wall wear will also be affected by the slightly more extreme rod angles in the 2.3. Everyone has pretty much alluded to this already with the talk of egg-shaped cylinder bores. I haven't done any calculations to account for this factor, because the math would have been rather involved. Also note that there are other factors to consider when determining a lower end's safe RPM limit. Comparing two engines using max piston speed alone is a pretty loose approximation. Of greater importance would perhaps be plots of piston position, velocity, and acceleration with respect to time. Maybe someday when I'm getting paid to do that kind of math I'll actually get around to it.

Take your time. The last thing we need is to upset the family balance at home. It would be great to see what you come up with though. Since you're wife's awfully sharp, don't feel embarassed if she comes up with the answer first!

Oddly, my wife falls asleep whenever I start talking engines to her. She prefers to get her kicks out of making soda bottle bombs with the various reactor plant chemicals. I guess you'll do anything to entertain yourself when you're underway. When she loses a finger, I'll be the one laughing, though!

 

[fourreGsixty3]

Wow Don I think I understood about...3 words in your explination, the picture was great Im saving it to my pc so Ill have it to refer back to in the future if I ever come across something like this again.

Dustin

 

[MyBeatGSX]

Don if you don't mind me asking, what do you do? Some kind of engineer or chemist I'm guessing.

 

[donmagicjuan]

Hah, that's a pretty good guess. I was a nuclear reactor operator in the Navy for a while, but now I'm in the process of getting my Mechanical Engineering degree (surprise). After I'm done, I'll be off to flight school to become a pilot, provided I pass the flight physical.

 

[fourreGsixty3]

Wow going from a fast DSM to a jet, , just drop a jet engine into a DSM, there is a Y2K Eclipse on streetfire with a jet engine in the rear, it shoots 20ft flames. Sorry for pulling it off topic a bit.

Dustin

 

[donmagicjuan]

- Yeah, those kind of contraptions just scream "Darwin Award" to me.

 

[donmagicjuan]

For anyone that cares, I was fooling around with the mathematical function of piston velocity vs. crank angle today and noticed an error in my initial assumptions for my calculations. I made the assumption that max piston speed occurs at 90 degrees before either top or bottom dead center, or when the crankshaft is horizontal, which is incorrect. Actual max speed occurs at a slight angle above horizontal on both sides of the rotation. This angle is equal to the inverse tangent of (crank radius / rod length). This makes sense then that rod ratio does have an influence on the max piston speed for a given crankshaft radius.

I've included a drawing to help you visualize these points: http://www.putfile.com/pic.php?img=3389607

With this correction taken into account, the new coefficient to relate the 2.0L engine to the 2.3L stroker becomes 1.1494. Not much, I know, but I hate being wrong. This changes my max speed calculations for 7200 RPM to the following values:

2.0: 113.4 ft/s

2.3: 130.4 ft/s

You'll notice that the graph of piston velocity vs. crank angle is an asymetrical sine wave with peak values slightly after 0 degrees and slightly before 180 degrees. These are the points which correspond to the moments when the rod makes a right angle with the crank throw, as shown in the diagram.

If anyone feels up to the task of checking my math on the velocity function, please let me know if you find any errors.

 

[stockfornow]

As fourreGsixty3 said, I shouldn't have bought it off ebay, since today I took it to the machine shop (a friend of mine works there), and he just said the same thing, but he checked it, and said that it would be good, that I got really really lucky. Well, it was a huge risk, but I quess I got away with it.

For andymoraitis, yes I want torque. It will be a daily driver, but nex summer it will see a track couple times a month. As I understand now, I won't raise my rev limiter, and drive it on the street under 6K, and only when racing take it to 7.5K not past that though, and go with Comp 200's. As for the turbo, I have a T3/T4 .57 trim sitting next to my bed with exhaust manifold, and a GM MAF and MAF T.

Splitpi thanks for that reply.

Thanks a lot to you Don, and for your calculations.

So, then what about the up to 12 degrees of timing? What do I do with timing? And somewhere I have seen a fast way of breaking the engine in, like beating on it to make rings seal in its first miles, but if it's true do I do it with boost or without it?

 

[donmagicjuan]

Here's a webpage that describes the "beat on it" break-in method: http://www.mototuneusa.com/break_in_secrets.htm

A good plan usually involves moderate boost levels of about 15 psi for the first few hundred miles, after which it should be able to handle whatever you plan on throwing at it. As for the timing, I don't have any experience tuning a stroker engine, so I'll have to let Andy or someone else field that one. To alter the ignition timing you will need either a replacement EPROM chip with custom maps, DSMlink, ECU+, or something similar.

Best of luck!

 

[andymoraitis]

For stroker, A/F's in the 11:1-11.5:1 range works well and timing can be kept low since flame front speed doesn't need to be as fast as a 2.0 due to the motor's VE. Around 8-12 degrees on pump is more than enough. I may actually tune my down to 10 and see if I can spare the clutch a bit more since 12 degrees at 28psi creates slippage.

 

[fourreGsixty3]

If anyone feels up to the task of checking my math on the velocity function, please let me know if you find any errors.

Yeah Ok, Don Ill get right on that...not. I think Ill save the rest of my life trying to figure out how to even start your calculations, and just trust you. Also when doing the motoman break in method do it with boost, boost helps seal the rings better, I would say 14-15psi will suffice.

I may actually tune my down to 10 and see if I can spare the clutch a bit more since 12 degrees at 28psi creates slippage

In my mind this is a good thing means your making good power, I think its time to upgrade that PP to a 2900 Andy. Sure the 2900 is a little over kill for you, but you cant complain with 2100 clutch pressure, and more TQ clamping force then a 2600.

Dustin

 

[andymoraitis]

True dat. I'm surprised the 2100 held out this well. The great thing is it won't slip at 25 so I guess I can be thankful. Dropping the timing to raise the boost is a bit of a tradeoff though. I'm taking some torque away so that I can have more top end. It's a bit of a bandaid, but it's worth it in case I take this thing to the track and want to run 30 psi. Hell I may even go to 8 degrees.

When I change the clutch, eventually, it'll get a 2900 for sure.

 

[fourreGsixty3]

If Jack M. can use one for his 600+hp beast, then its fine for all use DD guys not pushing half that. Oh yeah and what do you think about running 14-15psi for the motoman break it, I know you did this break it, would you personally recommend more, or less?

Dustin

 

[andymoraitis]

I ran 15psi for the first 30 miles, changed the oil and then yanked on it immediately after that. It's in those first 30 miles of acceleration and deceleration pulls that the rings will do most of their seating so it's perfectly safe to turn it up after that to encourage the process to continue.

2500 miles later, my compression has finally stabilized. It stuck at 170-170-170-170 for a while, but after the change to synthetic it's peaked at 175-175-175-180. I can live with that considering that I have Comp 200's.

 

[MyBeatGSX]

Andy, where did you get your stroker from or was it custom build? I'm in the process of putting together a completely new (read: way higher budget) setup for my car next year, and I'm debating the 2.3 or a 2.0. Either one will need head work correct? Either to flow more for the 2.3 or to rev higher for the 2.0. I was worried about tuning with a 2.3 because not many people around here are running them, but then you told me about the chip thing so I might just go that route and save a lot of hastle.

How's the engine harshness without balance shafts? I've drove the new SE-R's with the very long stroke QR25 WITH balance shafts and the thing felt like it was going to fall apart at 5,000rpm (limiter is at like 6,200). I don't want a motor that feels like that, smooth is nice.

 

[andymoraitis]

Tyler,

I bought my parts from SBR and had them installed a local shop (Arcola Machine). It's a cut 4G64 crank with .040 over Wiseco's and Manley H-Beam rods at 8.8:1. I did have the crank magnafluxed to ensure it's integrity and it's held up beautifully so far. With the exception of the Comp 200's, the valvetrain is completely stock and I rev to a max of 7000-7200.

Tuning is a bit different, but what's great is that you can run low timing on forged internals to get away with big boost on pump. Since you have an FMIC, you won't struggle like I do with a larger sidemount. The chip tuning solution is great for laying a baseline and you can keep the AFC to tweak it a bit.

With your combo, the only thing I'm not sure about is if the EVO III will hold big boost to redline (around 24-26 psi). I know Shape runs his at high boost on a 2.0 and can't run more than 24 to red with a 272/264 combo so a bigger turbo will likely be necessary to meet the volumetric demands of the stroker. My 50 trim will hold big boost and that's about as small as I'd go for one of these motors. Aside of increased vibration at idle, I have no additional vibrations and the motor revs smoothly throughout the RPM range.

 

[MyBeatGSX]

I'm gona use that Evo III as a large ash tray next year. Its going, the (most likely defective) injectors are going, the SAFC is going, if there's any part on the car that looks dirty or that I personally just don't like, its gone. I'm fed up with driving this hacked up pos that runs right once in a blue moon when a unicorn is running along behind me and I have a lepricuan holding a 4 leaf clover and a rabbits foot sitting in the passenger seat.
I thought I was doing stuff the right way the first time, but apparently the car wants more money spent on it. This spring it gets a new built long block, new turbo setup, new fuel system (pump is questionable, so is regulator), and some real engine management. And if its not driving how I want I'm selling it or burning it at the end of the summer and going back to Hondas.

 

[andymoraitis]

Wow! Tell us how you really feel.

 

[MyBeatGSX]

Yes, I confess. That's the sad reality. This car just shows no love back, I give and I give and I give and the thing won't give me an inch in return. Ever time I go to the dyno its just one disappointment after another, and the track, forget it. I went once and I won't go again, I really would burn the thing if it turned another mid-high 14 in the low 90's.

 

[andymoraitis]

Yup, I can understand that. I went 12.50's on less parts than what you have now. It's either driving or tuning, but I'm betting it's more in the tune than anything else. Those AFC's really aren't optimal (yes I know you know that), but before you give up, try a chipped ECU and head back to the dyno one more time. I promise you'll see improvement if you have no boost leaks and strong compression.

 

[stockfornow]

So would I still have to get an Eprom ECU or would MAF Translator blow thru setup would be fine? I don't have an SAFC. And what should I do for the head, without really spending too much on it? And how would I be able to tune my timing down to 12 degrees with the chip only or is there another way? Thanks, again.