it is a 102mm stroke

 

yea...102mm

 

run a 2 ring piston & get some special rods made that utilize a smaller piston pin & are longer, that way you can shove the pin further up.

piston speed is going to limit you with the stroke your talking about........actually it's your wallet that will limit you!

 

I would never run a 2 ring piston on anything unless it is strictly a race motor...and smaller pins are a bad idea in my book as they are a power limitation and for weight reasons (wall thickness)...

as for the limitation I would describe it as acceleration and not velocity that will kill the motor...different rod ratios can have the same mean piston speed but different accelerations...if working out localized velocities you may as well look at the acceleration instead.

 

Im still blowing off the dust on my old engine dynamics books and such...I actually had a John Lingenfelter "How to build Chevy V8's" book that has probably the most useful information in it of all.

Im still just playing with the specs for fun.......really....I havent even decided if this is going to be a straight out race mule or a test bed to see if I can make something reliably larger to just have pure displacement to play with.

Im glad you guys jump on board though, those are things I havent thought about.

In reality....the 108mm crank might be the answer, but that'd be custom and I'd have to cough up a TON of cash to do this, then sell off 4, maybe 3 cranks.....


Still working. Im more concerned about the rod ratio, piston speed, cylinder wall thickness and piston skirt issues, but Im talking with a motor builder that specializes in entirely different types of engines, and he seems optimistic.

 

do you think this guy is planning on getting 100k out of his motor? he is building a race motor whether he knows it or not.
[QUOTE=homemade wrx;4536687]smaller pins are a bad idea in my book as they are a power limitation and for weight reasons (wall thickness)...maybe in your experience, but in my experience with race engines that have won 18 Manufactorer championships on a world class level in imsa,cart & irl; it's an option that shouldnt be over looked. i am not asking to run a 0.500 slug of steel.

true, but once you get this extensive into engine modifications, it just opens up multitudes of means for destroying an engine.

i havent measure how much room there is between the valve cover & hood, but if this guy is really serious, get a head spacer, sleeve it & run a decent rod length...besides the revs of 8k5 are going to kill the piston with the stroke that he is talking about, hence my first comment, this guy isnt looking to get 100k out of his motor & believe it or not, he is making a race engine.

better yet, have dart make him a decent block meant to take the power with what ever deck height he chooses.

2 piston rings are not as bad as your implying.....maybe the pistons & rings that you have worked with are...which would make your statement valid.

 

yes, if he wants a 10k mile motor before needing a rebuilt I wouldn't see a problem with two rings...just he needs to know what he's getting into...I've never seen 2 ring motors live a long life...or more than 3 races. They weren't motors that I've built but I just know the builder or team running them...I've never built a 2 ring of my own so speak purely secondhand here.

For pins, well I've just run through this nightmare looking at estimated in cylinder pressures for my current build. between pauter, JE and I we are all thinking the pin is going to be my weakest link at only .905 OD...ID is what is being adjusted as I've crammed my compression height without sacrifing top ring land or going to a smaller pin diameter...but I'm most likely looking to make twice the power he is.

for the accelerations, he can find places on line that calculate it all out just to keep him self from going to far past what is a known safe area as everyone knows F=mA...I'm saying if making a pure race motor and everything is to be optimized (doubt it because of R&D and needed knowledge base) you look at the g's the internals are seeing as that is what causes piston fatigue, pin fatigue, rod stretch, rod bolt stretch, etc...which all can lead to failures

I agree he should cut the **** and get a taller deck via spacer or custom block. Makes life simple and deck height is the biggest problem we have with making subie motors...for 4G6x's its bore
we all have our own problems

out of curiosity, what motors/teams have you worked with/designed?

 

i was in the conversation, now you two SPEDs are speaking in tongues. lol.

 

sorry steve...

 

its ok...ill just start with my medical shenanigans

 

If you order custom pistons, you can move the wrist pin upward, therefore giving you room for more stroke and/or longer rods. The taller deck 4G64 will help this cause. Here are a few notes assuming a 87.5mm bore, zero deck clearance and a 4G64 deck height of 9.252" (per Brian Crower's website).

106mm stroke
5.906" Rod (standard 4G63)
Rod to Stroke Ratio = 1.415
Max Velocity @ 7500RPM = 8634.9 feet per minute (143.9 fps)
Max Velocity @ 8500RPM = 9786.2 feet per minute (163.1 fps)
Piston Compression Height = 1.259"
Piston Dish Volume required for 9.0:1 Compression Ratio: -24.2cc (w/ .051” MLS gasket). This should be achievable.

106mm stroke
6.151" Rod
Rod to Stroke Ratio = 1.474
Max Velocity @ 7500RPM = 8604.9 feet per minute (143.4 fps)
Max Velocity @ 8500RPM = 9752.2 feet per minute (162.5 fps)
Piston Compression Height = 1.014"
Piston Dish Volume required for 9.0:1 Compression Ratio: -24.2cc (w/ .051” MLS gasket). This might be difficult to achieve.

As mentioned in a post above, velocity is only one part of the equation…acceleration and side loading is very important. Regarding pin diameter, a 22mm or 21mm pin will be fine with the proper wall thickness.

 

Sean, awesome! Thanks for the input, as with everyone.

Side loading and piston speeds...problem. But...now I have to think of ways AROUND these problems. The pin Im not worried about....take a piece of forged metal the right diameter, heat treat the hell out of it and drill a 1/4" hole...

Im kidding.

Its been on the side burner, but Im glad non of the hater pirates jumped on this thread. It renewed my faith in the board and Im happy there is a lot of constructive and technical information to support the idea.

Now, anyone got 30 grand to make this motor and a few spares? No?

Nevermind.

 

Your current build? Care to fill us in? Im curious...

 

ill be the first to tell you hes keeping it very quiet. Its not for an Evo either.

 

yeah...I'm not talking to anyone about the design yet until my paperwork is done as I've had two subie shortblock companies trying to pump info out of me...the piston is quite nice if I say so. 100% custom and the rods only share big end diameter in commmon with factory...simply put, someone in the subie community has to try and catch AMS

I do have two 4g6x motors that I want to do though...oh well, I'll just move onto the 4b11.

I'll post up my motor results in off-topic (subie) if news doesn't get it here before I do. I know how the nasioc- evom back and forth talking goes