I'm wondering if i can use the stock piston. if it worth it. I need to rebuild the bottom half and was hoping to use the stock bore and piston as I just replaced those this summer. Later i would like to get cylinder works 94MM kit

friend of mine has it set pretty much that way and i think it runs great.

I didnt know Hotrods made a +4 stroker crank. I thought they just made a +5 mill.

its +5. and you can't run it with the stock piston unless you have a spacer plate and re-degreed cams

Im pretty sure they are not selling the +5 anymore, for now on its there new +4 short rod. no spacer and no special piston needed.

you look to be right, however hot rods website could be WAY more helpful
http://www.hotrodsproducts.com/index.cfm?f...p;productid=628

what? thats doodoo! I hate when companies do that thinking they are helping people out!. ugh!

This is the reply i got back this morning from them.

Mike, the 4259 is a +4mm stroker that can use a stock piston or any other piston of your choice. We changed the crank pin location and also the rod length to allow for the use of the stock piston. We changed this crank to accomadate the use of it with our big bore kit that we offer from Cylinder Works.

Just be careful when buying a hot rod stroker kit for the z400 for a while. A lot of places still have plenty of +5 available and you may get one of those instead of the +4, so be sure to tell whoever you order it from in the checkout notes that you want it to be the upgraded +4 stroker and not the old one.

KB Motorsports 270-774-1982

Hotrods Part # 4159 for the +5mm stroker.

Hotrods Part # 4259 for the +4mm stroker.

Just make sure you know what you're ordering... and make sure the company you're getting it from knows what you want, and that they ship the right one.

So whats are new static & dynamic compression with a 12:1 piston stroked to +4mm? I can see some issues in the future.

hmm well now that i don't need any of that other mumbo jumbo stroker pistons i could use that nice 50% off hotrods.... I'll have to do some reading

or you can give me that 50% off :)

this does open the door to a cheap stroker. i wouldnt even use a stock stroke crank if i ever had to rebuild a stocker.

hmm..$175 for a stoker..might be worth it

One of the problems on this +4mm build will be rod angle. It's a shorter rod with a 2mm offset crankpin. The LTZ already has a short rod to begin with, too. This won't be a really high rev engine combo, if you want engine durability. The front of cylinders develop more issues when rods get shorter. Rod angle can be a very big deal.

I'm not saying this Hotrods +4mm will be a bad thing - haven't even seen one. Just basing my comments on past experience.

I don't have time right now to write a long post about this, but research rod-to-stroke ratio and you'll find out why shortening your rod length is a very bad idea. The worse rod to stroke ratio you have the less your engine will rev, the worse your exhaust port flows (and Z's don't have a greatly designed exhaust port anyway), the less power you'll make, and so on. I'd get the +5 long rod crank over the short rod ANY day. I wouldn't put in a short rod stroker if someone gave it to me and offered to put it in.

? so what would the ratio be with a +4 and a +5?

Don't tell me that guys.
I'm a few days from ordering the +4 mil.
I'm going to run a 94mm cylinder though, so what is my option for running the +5? Spacer plate with BB piston?

Stroker piston..only need a spacer plate if you are running the normal piston. If you run the spacer you need to degree your cams.

well to clear up my above comment friend is running the plus 5 stock bore.

dont sweat it...do it! there are quite a few members running falicon cranks....they are shorter rods....heck der2z had a 11 mil stroke....means the rod was roughly 5.5mm shorter....i doubt 2mm in your case is going to change it drastically.

I ordered it today.
I asked one of the tech guys on the Hot Rods side about them and he said they've sold quite a few for people in my application. Who are running a 94mm bore and need/want to stroke it.
I would've gotten the +5 mil and the stroker piston for a 92 mile cylinder, but can't get a 92 mil. Unless I get my old stocker cut.... Nah!
Anyway, back to point. I asked him if they had any issues with it. They went through multiple rods and crank designs before they came out with it. It wasn't a night time project.
So after discussing the ins and outs of it, and what they have seen/heard from them.. about 20 minutes later... I ordered the crank.

great keep us updated! I'll be ordering mine over the winter maybe in jan.

Lets see, according to my calculations (which may be way off anyhow!),

W/ the +5 stroke, w/ a stroke of 67.6mm, this would give you a rod to stroke ratio of about 1.583

w/ the +4 stroke, w/ a stroke of 66.6mm, this would give you a rod to stroke ratio of about 1.577

Here I have used Normalz's measurement of the stock rod to be ~107mm, from his response in another thread. I believe the title of this thread was simply stock rod length or something like that.
And also figured the "short" rod of the +4mm stroker to be ~105mm.

I am by no means an expert on the subject, or even know much of anything about the effects of the ratio, and am kinda hoping to hear someone chime in here more about it because I am highly interested, but I wouldn't think that this difference of 0.006 in ratio wouldn't amount to much if any, noticeable difference. However, by all means, point it out if I have made a mistake in the math, which is very possible.

from what I have heard/read, ideally you want to be at 1.5+ on the rod ratio

IMO the +4 crank will be fine if youre not running a 10krpm limiter lol

Correct - the +5mm stroker crank used a 2.5mm offset crankpin and the stock rod length of 107.00mm (center to center). Good estimation of the +4mm setup, man. That's gotta be what it is, with a 105mm rod. This engine runs a SHORT rod...

As far as piston speed goes, like mentioned in the above post, I can barely stay under 5k feet per minute with a +5mm stroker crank running a Yoshi R&D (Mitsubishi) 11k CDI. It's under the threshold of 5k FPM, but just barely.

As well as changing Piston Speed numbers on the new configuration, it'll change the Piston Acceleration numbers, too, due to the rod going shorter now. That's a problem on some Falicon cranks, and I know for sure that you have to make RPM changes to your setup in order to run the Falicon +7.8mm stroke setup. Those Piston Acceleration numbers are through the roof when you're running anything near a stock rev limit.

That little bit wont amount to anything. think about the extremely small change in angle with removing a measly 2mm...

with my +5mm my rev limit is at 10.5k....and with this cam change i'm doing right now, i plan on raising it some. i'm not scared to run it to 11k rpm. everyone told me my 383 stroker in my street car would not rev past 6k..Ha...thats why i was bouncing off the limiter at 7800rpm...and its seen 8k quite a few times...and yes i had quite a few people call me a liar...until they went for a ride. and i must add i went to the dyno and they asked what to pull it to....i told them the rev limit...they said whats the rev limit? i said 7800....they laughed. so did i...lol...after they made the first pull...it made peak power at 6800 rpm and only lost 11hp from 6800 rpm till rev limit. that debunked there belief in the stroker myth...that a stroker cant be revved high. I have an idea why that theory came about. Most people use a cam that was designed for a 350 in their bigger motor...well its starving for more air because its bigger. so it needs a cam and set of heads to support the increased flow. most people would not provide the motor what it needed, so it ran out of steam earlier than the equally built 350. keep this in mind for your +4mm bbs motor.

In keeping under the 5,000 ft/min mean piston speed, my calc. shows that with the +4 stroke, it should be good up to about 11.44k rpm.

However, If I am doing this correctly, at this rpm, you are creating a maximum piston acceleration of 206,532 ft/sec^2.

Normalz, I know you have said that you try and stay under the 5k fpm mark for mean piston speed, what, on these engines, do you try and keep the piston acceleration below?

5k FPM for Piston Speed, man...



Piston Accel depends on ring thickness - no motorcycle-type piston ring made can withstand a Piston Accel number of 206k ft/sec^2, so the revs have to come WAY down. What you bring it down to will depends on how thick your rings are, and what that particular thickness can withstand.

Yes, sorry, that is what I meant piston speed not accel., that was simply a typo there, I have corrected it.

I have read in one handbook that they suggest between 100k - 150k ft/sec^2, so I knew that the revs had to come way down, I was just looking for your opinion on the matter though. I was just throwing some numbers around b/c I am trying to figure this stuff out for myself, and possibly helping others out that are looking into this new setup.

That is a good thing to know though, and I hadn't yet thought of ring thicknesses... Perhaps that is something to look to the ring manufacture to in the design of the engine as well?

I just quickly ran the numbers again, and Wow, now I see what you mean on the difference that it makes on the piston acceleration!

I ran the numbers, assuming that the rings could withstand a max. of 100k ft/s^2 piston acceleration (only based on what I read from handbook), and thus w/ this +4 setup, the limiting rev would thus only be 7.9k rpm's. Wow, big difference this stroker would make then when it comes to piston accel!

What do you think?

what is the difference?

Is that right? 7900rpm?

Hmmmm..... in MX I don't normally rev it real high anyway, but that number seems low compared to what I've been reading.
It should be good to ~8700rpm. If not more.. not saying you could run that all day long.. but for bursts.
It should be fine.
You could run 7500rpm all day long and not see an issue.

Just ran the numbers through my formula and came up with a max RPM of right around 11,000RPM.
That right? That fits in with what I was told... As long as you don't have a monster rev limit it should be plenty safe.

That's going off of piston speed staying below 5k FPM.

Yes, a little over 11k rpm, is correct, however, only when looking at piston speed. However, piston acceleration also needs to be looked at. If you read above, I also figured above 11k for piston speed, but to keep the piston accel. in check, it is actually going to have to be much lower. Piston speed and piston acceleration are much different things. The acceleration is affected by both the length of the stroke, and also the length of the rod. Piston speed only takes into accout stroke length.

i hold her wide open if it goes all well. will do it again bigger and better

so how much faster is the piston accel on a +4 over a +5 crank. I wouldnt think that 1mm would change it THAT drastically to where a stock limiter would be too high?

Hmmm, interesting! To answer your question, for the setup with +4 stroke, short rod, and at the stock rev limit of 9250 RPM, the Max. piston acceleration is 134,988 ft/s^2.

However, at stock rev limit, the +5 stroke, w/ stock rod length is higher at 136,795 ft/s^2. That is surprising to me, I thought it would have been the other way around before I actually calculated it for both setups. Maybe I am doing something wrong after all? haha

As far as calculating the max rpm both setups could handle according to max piston accel., as Normalz said before, the max accel that the rings could handle is dependent on the ring thickness, therefore I was just guessing what was probably a very conservative figure of 100k ft/s^2 max. I really don't know enough about what the maximum should be on these engines to suggest what RPM they should run max. To compare the two above, I have solved the equation in reverse for the Acceleration instead of RPM.

I'm starting to confuse myself, haha.

I did some calculations, and the stock rod/stroke ratio for a Z is better than I guessed it to be, which explains why they run so good with a badly designed exhaust port. Ideal rod/stroke ratio for an engine is about 1.70 to 1.75.

--------------------------------------------------------------Stroke --------------Rod length---------Rod-to-stroke Ratio
Stock stroke:-------------------------------------------62.6 mm------------------107mm---------------------1.71
Hot Rods 4mm short rod:---------------------------66.6 mm------------------105mm----------------------1.57
Hot Rods 5mm long rod: ---------------------------67.6 mm------------------107mm---------------------1.58
Falicon 7.8mm short rod:----------------------------70.4 mm-------------------103.1 mm-----------------1.46
11mm short rod (since someone mentioned it)-73.6 mm-----------------101.5 mm---------------1.38


The lower the r/s ratio, the less time the piston is at TDC. Thats is why you want a bad r/s ratio for a nitrous motor, somewhere in the 1.4's. Since nitrous is fast burning, you don't want the piston sitting 'idle' at TDC too long while the nitrous is burning or you'll melt your motor down.

As you can see, the difference in ideal rod/stroke ratio's for 2 completely different motors is very small, so saying 'a small amount won't make a difference' is a false statement.

http://www.eatel.net/~stentorian/wristpinplacement.swf

Been doing a ton of reading for the past couple hours trying to freshen my brain on this.... it's been a while since school.

Thinner rings have a higher "flutter speed".
Can't find a formula for the life of me that can measure a ring and come up with a flutter speed...
By going from what the manual says, my 4.3 in my truck would grenade at 7,000rpm.. but it raps 8,500 repeatedly.
Not the best for the motor but it's still together.

Going by the thinner rings being good for atleast 150k if not more, the rings wouldn't flutter until around the 9,000 - 9,500rpm mark.
I think so long as you dont try rapping 11k rpm with it, and you have a decent piston, with decent rings it will be fine.
I wouldn't use a wiseco because of their tolerance level.
CP uses thinner rings, which would be better for high rpm situations.

Plus, the whole point of stroking is to use more mid range rpm, because you gained torque... you won't have to over rev as much

based on these numbers it seems like the +4 would be ok. right?

what do you guys think. I plan on buy this big bore kit and the +4mm http://cgi.ebay.com/ebaymotors/SUZUKI-JE-L...sQ5fAccessories

To sum it all up, yes, this combination would probably be fine.

^^^^^^^^^ I agree.

That kit isn't bad, but double check your piston fit in the cylinder. I got that same deal last year, and had to replace the piston after 5-7 hours of run time.

Matt, you're on the ball with your Piston Accel calcs. I'll PM you some threshold data for ring thichness vs. accel max.

Bottom line - thick rings can't handle high Piston Accel numbers. Once you get your rings as thin as they'll go for the design of the piston, and your accel numbers are still above the threshold for that particular thickness, you have to make changes. The only thing left to change at that point is to chop the max RPM (rev limit) down until you meet the mark.

You're on it, dude...

On a side note, the safest rev limit to set on a Falicon +7.8mm stroker is something like 8250 RPM. I've got the exact number somewhere in a notebook, but it's right there. Can you rev it higher? Yep. Will it live very long? No way...

so I should early shift with my mods? I have the dyna non programmable. should i go back to the stock cdi?

What mods? The ones in your sig? Nothing in there suggests that you should be shifting early for anything.

I think you are overlooking the stickers that make horsepower