Stroked WRX vs. Tubro 2.5 R

[MB38]

Ah, hell. I just re-read my post a little bit more carefully and realized that I wasn't being clear at all. I apologize. Nismon's description is the best one on this page.

With regards to boring out, however, I still have seen it done for the sake of high boost. They usually don't bore it out more than 1-2mm in diameter (speaking on the vehicles that I've seen) and usually couple it with a thicker head gasket as well. This, when coupled with a full stroker kit (usually custom-made at this level), allows for enormous boost and power. With this part, however, I've stepped way beyond what would be necessary to add another .4 or .5 liters to a boxer engine.

[LjasonL]

Originally Posted by Nismon

OK, where do i start..
Stroking an engine can be done 2 ways, a new crank with a longer throw or offset grinding the crank journal to achieve the same effect.
In this way the piston travels further down the bore and therefore has more swept volume and hence you achieve more capacity.
This has nothing to do with how much space there is in which the intake charge has to be compressed or even its volume. the capacity being equal to the bore radius x pi x stroke x no of cylinders.
Compression ratio is calculated by chamber capacity (clearance volume) divided by cylinder capacity(swept volume).
Clearance volume is a combination of chaber cc, piston dish cc or crown(+ or -),head gasket thickness and deck height.
If you had only shorter rods, all you would be doing would be lowering comp and piston would travel same distance, further down but not as high up.
At no time is there a specific aim to lower the compression, the pistons you chose will be the main defining factor in the compression ratio-the rod and piston at TDC should be at deck height give or take 0.5mm or 20thou, this combined with the head gasket thickness, combustion chamber cc, piston dish or crown will give you comp.
If you leavethe piston design same and chamber same big increase capacity, you also increase the comp and there is more swept vs same clearance volume.
In regard to boring to acheive greater boost levels, the more meat you take off the bore and therefore the weaker the engine becomes as you reduce wall thickness and increase chance of cracking the bore and heat control.Most heavily boosted engine will try to maintain close to stock bore size due to this specifically, or at least within very safe tolerance.Lowering the compression helps with big boost a lot but once again you can achieve this with only a new set of pistons and not increase bore , stroke or even capacity at all.
Hopefully i have cleared this up. thanks.

I had to read that a few times to take it all in. Nice

Another thing to consider when stroking is the rod and piston speed. A longer stroke means the piston is going to have to move further for each revolution, therefore moving faster. So the pistons in a regular 2.0 WRX at 7000 RPM would me moving much slower than the pistons in a WRX stroked to 2.4 at 7000 RPM. Also the angle of the rods to the crank. What's that called again? Rod angle? Anyways a longer stroke means the rod is going to go to a greater angle in a revolution, so it has more stress put on it.

[DVS LT1]

Originally Posted by Marc-OS
Stroked = new pistons, rods, and possibly crankshaft, which create a shorter stroke (hence the name "stroked"), and shorter stroke means more displacement.

Originally Posted by Nismon

Both you guys are on drugs.go to your local library and read up on it before you go talking about what you dont understand.

I read that myself and was like WTF??? - is he joking? Nevermind, I found this topic and thought, "what's this, people are actually stroking little four cylinders, to what? - 2.2 litres??" It never occured to me that guys were doing this with WRX motors. I don't blame the fellow who goofed on the stroker wisdom because its really not part of your mainstream culture - at least it seems that most people are bent on full engine swaps and/or squeezing as much boost into the thing as possible.
You tell me - would it be a better HP:$ ratio to stroke a WRX motor OR to jack up the boost? Which service is more readily available??

For us olde school V8 guys, its all about bore x stroke. My biggest decision in the next year or two will be whether to stroke my engine to 383 cubic inches/6.3 litres or to bore it out even more and stroke it to 396 cubic inches/6.5 litres. I could bolt on 130 RWHP with a 6 psi blower, or I could make 450+ total RWHP building a stroker motor. It would cost me almost the same for either option.

There is nothing wrong with boosting a motor - it can make them very, very fast (10's and 9's for sure) - but sooner or later you will need more engine to make the car go quicker. You don't see sub-8 second dragsters running anything less that 600+ cubic inch big blocks.

You can always make a larger engine displace faster,

but you can't make a smaller engine displace more than what its block is capable of.

[LjasonL]

Originally Posted by DVS LT1

There is nothing wrong with boosting a motor - it can make them very, very fast (10's and 9's for sure) - but sooner or later you will need more engine to make the car go quicker.

Alternatively you could say "There is nothing wrong with large displacement - it can make them very, very fast (9's and 10's for sure) - but sooner or later you will need boost to make the car go quicker"

i.e.:

The "No replacement for displacement" line of thinking - If you run the same amount of boost on 2 motors, the one with more displacement will make more power. Such as 20 psi on a 2.0 liter WRX vs 20 psi on a 5.7 liter vette. Therefore, displacement is king.

The "No replacement for boost" line of thinking - If you have 2 motors of equal displacement, the one with more boost will make more power. Such as 10 psi on a 5.7 liter vetter vs 20 psi on a 5.7 liter Vette. Therefore, boost is king.

No point really, just something to think about.

[DVS LT1]

Well, no there is a point here - I can clearly understand what you're saying, and anyone can put forth a strong case for an argument given you accept certain premises - what I was trying to put into perspective ultimately was max acceleration. The maximum possible acceleration a car can achieve given any particular motor.

Look at it this way - Take a 2.0L 4 cylinder motor. We can bore it over and stroke it to achieve the maximum possible displacement that the block is capable of (who cares if it cracks, this is for one hypothetical run). Now, we can boost it to 25psi, 35?psi?, whatever the maximum possible boost would be without blowing up the engine before the end of this record breaking run. OK. Its not fast ENOUGH! Well, lets spray those forged 4340 internals a 250HP shot of Nitro - and when thats not fast enough we'll just run the fucker on top fuel.

So, we now have a monster 2.8L fire breathing motor that ran a high 7 second 1/4 mile at over 160 MPH. Not bad. Can we make the engine any faster??? NO - but we can strip that WRX chassis down even more or plant this motor in as light a car as possible so long as it doesn't get airborne and not finish the race. But thats IT! This contraption will not be capable of going any faster - unless..... a larger displacement motor is used! :

And there you have it. You can argue all you want that a bigger motor/bigger car is going to weigh more and equal everything out blah, blah, you know nothing, blah..... Take this imaginary 2.8L rocket engine and put wheels on itself for all I care!, make it remote controlled, and run it down the track just as a bare engine(again assuming it can stay on the ground and complete the run) - it won't make a shred of difference, because that 660 cubic inch, big block V8 in that other dragster (thats actually being driven by a person and running the exact same mods as the crazy 2.8L) is going to put out SOOOOOOO much more horespower that regardless of the weight disparity its still going to pull off a 4 second 1/4 mile at 240+ MPH.

Bottom line: take a V8 and a 4-banger

you can boost them both,

you can spray them both,

you can over bore & stroke them both,






when all is said and done, you'll be lucky if the displacement of the 4-banger ends up being half of what the displacement of the V8 was when it was stock.





I know this scenario was extreme, but that was the point I was making. You can strive to make your car as fast as possible with boost, fuel, less weight, etc.... but sooner or later you will reach the limit of your engines displacement - and you simply won't be able to displace what you've got any faster.

It is at this point where the "no replacement for displacement" logic really becomes apparent and appreciated.

[Nismon]

OK, no replacement for displacement?
well if we remove your biased interpretation of more cubes equals more power and more cubes equals faster and just take it for what it is, we find that there is a replacement and we see this everyday when you look at people with turbos(boost over cubes) people with gas/fuels ( chemicals over displacement) and people who use k&n/extractors/ cams / headwork(efficiency over displacement) alll these options usually are easier and produce better result than just cubes alone especiallly like you said when you can physically go no larger with the engine you have, you have to look at other options or get a new motor.
When you look at top fuel cars, have a look at the cubic capacity ot the top ten, you will NOT find that they are all at max capacity and that the higher capacity is the fastest overall.-this even severly disproves you theory as you believe a 622 cube car will always beat a 588 cube car as this is not the case.
If you had any idea about it , at this stage of racing chassis and clutch and aerodynamics play a huge role and overcome power to be the main deciding factor.

[DVS LT1]

Originally Posted by Nismon

...we find that there is a replacement and we see this everyday when you look at people with turbos(boost over cubes) people with gas/fuels ( chemicals over displacement) and people who use k&n/extractors/ cams / headwork(efficiency over displacement) alll these options usually are easier and produce better result than just cubes alone especiallly like you said when you can physically go no larger with the engine you have, you have to look at other options or get a new motor........When you look at top fuel cars, have a look at the cubic capacity ot the top ten, you will NOT find that they are all at max capacity and that the higher capacity is the fastest overall.-this even severly disproves you theory as you believe a 622 cube car will always beat a 588 cube car as this is not the case.
If you had any idea about it , at this stage of racing chassis and clutch and aerodynamics play a huge role and overcome power to be the main deciding factor.

#1) Most people will find a substitute for displacement in everyday driving situations, I wasn't even touching that. Plus, you most likely bought the car based on an number of factors - so if it came with a turbo, raise the boost. If it didn't, slap one on. You're stuck with what you bought.

#2) My real point about the fastest cars on earth was that you will not see a small cid four or six cylinder engine running in the top ten, let alone the top classes! Obviously aerodynamics, weight, and as you so astutely pointed out, clutches, play their part - Is a bigger engine with a broken wheel going to run as fast as a slightly smaller engine with four fully functional wheels?



And I have some idea about the significance of chassis rigidity buddy - It would be nice though if I could just drop a stroker motor and gears into my car and not have to worry about my frame twisting like a pretzel, or having too much power to put down to the pavement.

[Nismon]

My point is that what the hell do top fuel engines have that is relative to everyday life and the cars we drive?
Not much and therefore there will always be a replacement/ alternative/
substitute for displacement.
second , if we live in the fantasy world where you strap engine to themselves and shoot them down a track, then power to weight will become a vital ingredient, a cast iron V8 will need to generate twice the power of a 4 cyl that is half the weight-this comes down to HP per Litre and efficiency.
third, if you were to slap in the biggest mutha engine you could find to make you car as fast as you can, the guy who has that std engine modded will wave good bye on the first corner as you spear off into the bushes cos it refuses to turn with 500kg of motor over the front wheels.

[DVS LT1]

Hey bud, you really should read my posts more thoroughly - because when you do, key phrases appear that clearly state:

"there is nothing wrong with boosting a motor" (I love Grand National's, no replacement for displacement but a damn good substitute under most circumstances!")

"sooner or later you will need more engine to make the car go quicker" (for most ordinary citizens - NEVER. For the real speed freak - its inevitable!)

"the maximum possible acceleration a car can achieve given any particular motor" (did this sound like I was talking about handling?)

"I know this scenario was extreme, but that was the point I was making" (I even said I wasn't talking about the kid who wants his I4 to have a little "zip" when he boots to the store for some milk!)

"Most people will find a substitute for displacement in everyday driving situations, I wasn't even touching that" (sounds familiar)

"you will not see a small cid four or six cylinder engine running in the top ten, let alone the top classes" (Why not? think about it - if you forget why I started talking about this, don't think of grocery boy just re-read the third point)

"you can't make a smaller engine displace more than what its block is capable of...(and eventually)...you simply won't be able to displace what you've got any faster" ( What now - is that it? What's the solution?????????????????????????????????????????? ?????????????????????????????????????????????? (hint, last point might help)

"It is at this point where the "no replacement for displacement" logic really becomes apparent and appreciated" (again, if you're really chasin speed then you know this IS the key - if you think an 11 second run is the end-all and be-all...well then, go get em boy! Besides, its not like its possible for anyone to go faster than that anyhow. Ah ignorance is bliss)

You know, I like talking to people about cars man - and I've had fun yappin about this(can you tell?). To each his own, I didn't start these posts to convert any of you guys to the newest in 1950's small-block pushrod technology! I was merely attempting to illustrate how the "no replacement for displacement" theory is in fact the key solution in certain applications.

And by the way, if I had the energy I would LOVE to debate with you the horsepower/litre argument, but the truth is us F-body guys hear it all the time from the 4.6L Mustang GT crew. Whatever will help them feel better about their cars I guess! Lets you and I save that one for later. Adios.

[ben_ak]

Interesting disscussion guys. Back to the original subject for a moment. My boss has a 1998 2.5rs (1998 Models have DOHC, not SOHC) that we put a Forced Air Technology Stage II turbo kit in. He is running 12psi with 8.5:1 pistons and a valve job. No trans problems with a clutch approx. 30% stronger than stock (he runs the car in SCCA Solo II). This car hauls the mail but runs out of gears pretty quick. He ran a 13.9 with 8psi just messing around on a test & tune night. No runs with boost turned up yet. By the way, if anybody is in Alaska and is interested, the car is for sale - $19,000

[boogergrom]

my replacement for displacement would have to be the mazda rotory, in australia there are guys running low 7s in their 1.3 litre turbocharged rotory engines, they also weigh less than a big block chev, on 12 pounds of boost with the right mods they put out around 6-800 rear wheel horsepower...

[LjasonL]

Rotaries complete one combustion cycle for every rotation, rather than every other rotation like a conventional piston engine. So it's not really fair to compare them displacement wise. It would be more accurate to say the 13b is a 2.6 liter.

And Chevy's 5.7 liter LS1 actually weighs less then Mazda's "1.3" liter twin turbo.

[naylor]

definatly gonna be cheaper to do the WRX, turbo kits for the 2.5RS start at like 3 grand, unless i have been lookin in the wrong places, plus your gonna need a new intake and exhaust manifold and other shit which is gonna add up.

[LjasonL]

Originally Posted by naylor

definatly gonna be cheaper to do the WRX, turbo kits for the 2.5RS start at like 3 grand, unless i have been lookin in the wrong places, plus your gonna need a new intake and exhaust manifold and other shit which is gonna add up.

With $3000 you could not only turbo it but slap in some lower comp pistons, a standalone ECU, intake, complete exhaust, and still have some left over to tune with.