TO EVERYONE that is making or has made a stroker.

[nando]

It all depends on the rod ratio... if the rod ratio is correct for the stroke of the motor... then there is no reason why the rods should have any issues... and any motor that is modified is going 2 have a shorter life span, especially if ur trying 2 squeeze more power out of the motor.

of course.. but E rods are only 130mm, there is no reason why you would want to use them for a stroker (especially with an 84mm crank!). either way you end up with a ratio below 1.6, plus they are heavy.

[Sean]

My SuperEta pistons are for sale. Who wants em?

;)

[JJGBMW323]

Ight Stupid question. I have seta crank rods and pistons. I will be using seta crank and pistons. Do i use the I or E rods?

Use the 325i head and 325i rods.
Use 524 td crank - 81mm.
Use forged MM pistons bore to 85 mm.
You know have a 2.8 liter stroker.

If you use the 325i head, the s50 crank and s50 rods,
the s50 crank is 86mm and you can bore it to 85 or 86 mm,
for a 3.0 stroker.

[Sean]

Use the 325i head and 325i rods.
Use 524 td crank - 81mm.
Use forged MM pistons bore to 85 mm.
You know have a 2.8 liter stroker.

If you use the 325i head, the s50 crank and s50 rods,
the s50 crank is 86mm and you can bore it to 85 or 86 mm,
for a 3.0 stroker.

I thought the S50 crank was 89.6mm?

Or, is that the S52 crank?

[nando]

Use the 325i head and 325i rods.
Use 524 td crank - 81mm.
Use forged MM pistons bore to 85 mm.
You know have a 2.8 liter stroker.

If you use the 325i head, the s50 crank and s50 rods,
the s50 crank is 86mm and you can bore it to 85 or 86 mm,
for a 3.0 stroker.

MM pistons are 86mm only

I don't think the TD crank is really neccesary for an N/A stroker, but would be great for a turbo. I'd also suggest 328i rods rather than the heavy M20b25 rods.

[Sean]

MM pistons are 86mm only

I don't think the TD crank is really neccesary for an N/A stroker, but would be great for a turbo. I'd also suggest 328i rods rather than the heavy M20b25 rods.

Or even S50 rods, even lighter than m52b28 rods, and the same length

[Madhatter]

shorter rods dont rev as high? 130mm rods in my 323i with a 6600rpm factory rev limit would tend to suggest otherwise.

Problem with the 3L motor is with the longer stroke you increase the piston speed at tdc. If you plan to rev the motor to exceedingly high rpms you are going to have to replace the factory forged items with something stronger and make sure you have a good set of rod bolts holding it together.

The problem exists because you can only reduce the piston compression height so far before you sacrifice piston strength. If you ran a 135mm rod a piston with a comp height of 28.8mm is just on the limit of what you want to reduce it to (and a lot of machinists wont produce a piston with a height much less). To run longer rods you would have to sacrifice metal on the crown and lands, thats not a good idea.

You guys are treating this like its all a blanket statement, rod ratio's arent quite that simple and they are only a guide figure, case in point bmw develop quite a few engines with less than ideal rod ratio's, yet they last the distance (why, because it isnt that simple). To investigate the inner workings of your motor package there are a lot more things to take into consideration. Things like how timing is effected, how efficient the engine is going to be at different degrees of the crank, piston speed at bdc and tdc, effects on pressure waves, cam timing and lift, etc. Ive got like 7 pages worth just on calculations relating to the 3L im building and i havent even touched a bolt yet.

You cant start talking about things like rod ratios in simple terms, it just isnt a figure that can be used like that.

if you want a new set of rods, brian crower will make you a new forged set to suit for about $10-$15 more (per rod) than the cost to replace the standard factory rods from one of the many parts places.

[rwh11385]

fuck all this noise Sean. put a m20b25 in. done.

[rwh11385]

Lets be honest - why would I bother? I'd lose so much money if I did. If I get into some money trouble, this car will be the last to go - it has too much time, and energy invested in it. Not to mention, I'd love to have it still when I HAVE a career and a house and a nice job - then I can pour even more into it. Even though, by then, I'd like to have an E30 M3 to play with.

Engineers. ha. Always love numbers.... but...

sunk costs must be ignored when decisions are made. the money you put into the car does not reflect on the best choice to be made in a dilemna (i.e. repair vs. replacement of your car) Besides, cars are risky and also a depreciating asset... not an investment.

the best option is to not put money into the car in the first place ;)

[madjurgen]

the only noise in here is you heeter, the rest of us are trying to have an intelligent conversation about strokers, you obviously dont agree, so why post?

On topic, Id be very interested in seeing exactly what types of calculations youre going through Madhatter in planning your 3L

[Madhatter]

when its not a freezing -2.3c (or about 27'F for you americans) ill go down to the workshop and find my little black book :D

Main thing i was working on last time was the cam specifics to help offset the lower piston speeds at bdc and when it accellerates from bdc. Need to match cam timings to get it to stay closed a little longer so it can build up cylinder pressure before opening. Because of the shorter rod (and the effects it has), you want to get the exhaust side of things flowing as best as you can, polish the exhaust ports, match the manifolds and get a good exhaust system and headers behind it. Not going to equate to massive gains, but its going to make a noticeible difference (besides which ive got an ITB setup im running and im going to dyno the engine NA before going turbo, so i want to see what i can squeeze out of it).

[rwh11385]

Ask yourself this question, are you honestly going to keep this engine/car for 100k longer. Frankly since your still in school there is always a chance that once you get a real job/income, you might move on to bigger and better things. 100k is alot of miles. Just something to keep in mind.

1300 sounds like alot for pistons, and a stroker is only going to make so much power. If you have to rebuild the motor again at 100k, then so be it I say. Thats at least 5+ years down the road, and thats if you put 20k a year on the car.

I'm not the only one with intelligent economics other don't seem to comprehend very well.

Everyone here besides Fielding and I seem to be one-sighted... I mean, a college kid building up a stroker with a S52 crank because he doesn't think a 2.7i would last long enough, and this all started with a budget stroker build... ha. People allow thinking to get out of hand quickly. I know i did.

But screw it.

[rwh11385]

Anytime you go with a stroker, you have shorter rods and a longer stroke.

MM has optimized the M20 stroker by using stronger rods and lighter pistons. They have an interest in people buying their kit. It doesn't mean that the 2.7 budget stroker is a bad engine, just not as good as theirs. The MM website says as much. It admits the 2.7 stroker is the best way to go on a budget. It comes down to a question of cost vs benefit and what you are willing to live with. Personally, for a street driven 15-20 year old car, I think the 2.7 supereta stroker is a good way to go. Not the best, but still good.

Sean was worried about engine life with the classic 2.7i and now he is going for longer stroke? I'm sorry, makes no sense.

Yes. 2.7i is the route, if not stock m20b25.

[rwh11385]

http://www.r3vlimited.com/board/showthread.php?t=65077&highlight=rod+ratio

Madhatter's calculations on rod ratios from before.

[madjurgen]

I mean, a college kid building up a stroker with a S52 crank because he doesn't think a 2.7i would last long enough, and this all started with a budget stroker build... ha.

When you put it that way, it is kinda funny. When he started talking about custom rods I assumed it was no longer a budget build.

At least you admit that your attitude now is a bit different (hypocritical) compared to what it use to be. Its funny reading posts from a while ago when you were busy planning your own stroker.

I was inquiring about calculations for the stuff other than r/s, like TDC/BDC piston speeds and cam timing issues.