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Author Topic: theoretical limit for crankshaft welding and grinding.  (Read 3289 times)

DasPoop

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theoretical limit for crankshaft welding and grinding.
« on: November 25, 2013, 12:40:37 AM »

Ok, I have a dilema. SCCA and all there "awesomeness" ditched there current rules and is implimenting much revised rules for 2014. that being said I got the go ahead and a small budget to test the waters on a loophole I talked with my regional steward about. Little more info.
Class is limited to 1600cc 4 valve NA Auto or Bike based doesnt matter Edit: Its actually 2.5L at 9:1 and a 32mm SIR. at 1450lbs
Class also have a provision for turbocharging and used to be 670cc No restrictor. After the 2012 runoffs which was dominated by a turbo car they imposed a 32mm inlet restrictor.
This year they have the same 670cc with 32mm inlet restrictor. I have managed to talk to my regional people and they agreed to allow me a 2 Valve 670cc engine with no restrictor.

That being said I have the notion of taking a suzuki(geo) G10 3 cyl and de stroking.

I have modeled the engine in engine analyzer pro and have some promising results.
How much can you de stroke a crank with welding and offset grinding even if I have to redrill oil passage holes. the rest of the bottom end can be scrounged cheaply. Miata rods at 133mm long and vitara pistons.

I am aware there are small Kei car engines avaliable in other markets but these(and parts) are hard to come by and the sheer number of geos avaliable in this country ensure plenty of blocks and heads to saw up and utilize.



« Last Edit: December 08, 2013, 02:14:26 PM by DasPoop »
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92CXyD

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #1 on: November 25, 2013, 01:33:05 AM »

Curious info.

Offset grinding weld help a little, wonder if there is a Suzuki bike crank would fit in the G10 block.  :noel:

DasPoop

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #2 on: November 25, 2013, 01:59:13 AM »

Curious info.

Offset grinding weld help a little, wonder if there is a Suzuki bike crank would fit in the G10 block.  :noel:

biggest problem is its 3 cyl with 120deg offsets. real hardcore suzuki tuners toss d series cranks in there 4 cyl "G" series motors.

Russ to get an idea I need to take a crank with a 3" stroke and make it a 2" stroke  :-\ 

you work at a foundry if  provide a crank cast it/forge it?? with mega large rod journals so as to allow for massive material removal. I am calling a local crank grinder tomorrow to get an idea on cost for the first unit. If I can get a usable unit to test the first engine I will have to go ahead to make a true forged de stroked crank.

I have also looked at cranks from other small 3 cyl engines in the 65mm stroke range but there bores are so small that I doubt the spacing would be even close.
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92CXyD

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #3 on: November 25, 2013, 02:06:03 AM »

Curious info.

Offset grinding weld help a little, wonder if there is a Suzuki bike crank would fit in the G10 block.  :noel:

biggest problem is its 3 cyl with 120deg offsets. real hardcore suzuki tuners toss d series cranks in there 4 cyl "G" series motors.

Russ to get an idea I need to take a crank with a 3" stroke and make it a 2" stroke  :-\ 

you work at a foundry if  provide a crank cast it/forge it?? with mega large rod journals so as to allow for massive material removal. I am calling a local crank grinder tomorrow to get an idea on cost for the first unit. If I can get a usable unit to test the first engine I will have to go ahead to make a true forged de stroked crank.

I have also looked at cranks from other small 3 cyl engines in the 65mm stroke range but there bores are so small that I doubt the spacing would be even close.

The foundry I work at pours stainless, brass, bronze, and aluminum in sand molds.  We have no forging capability.

There is a couple of forges near you. Do not know what the names of them, but I have heard mention of them.  :noel:

What about the Subaru Justy 3-cyl?

DasPoop

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #4 on: November 25, 2013, 02:26:23 AM »



What about the Subaru Justy 3-cyl?


also looked at this route as apparently they designed the engine around the suzuki g10 but its a 1.2L. and has a much different front cover with balance shafts and all kinds of other BS. The crank snout doesnt exactly bother me as I can run a dry sump setup with a small 3 stage pump but I am hoping to avoid really reinventing the wheel. that being said the first engine is going to be a bit rough anyhow. this is proof of concept once the first one runs then I am in good shape. My analyzer which I hope to be acurate(it better be its several hundred for the software) says 200+hp/L is not out of the question even with dinky 30mm/28mm valves. I imagine the heads are going to be reworked to the point of machining out the port with little regards to passages/galleys I encounter and fitting/welding tubes to facilitate much better valve to port angles.
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DasPoop

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #5 on: December 06, 2013, 01:56:14 PM »

Got a quote to destroke the crank 800$ was cheaper than I was expecting so expect a Build thread :)
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92CXyD

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #6 on: December 06, 2013, 04:42:45 PM »

What about one of those short stroke v-6 crank like the 1.8 mazda out of USDM MX-3?

Same bore as a d15/D16 w/ 69.6mm stroke  :noel:




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Re: theoretical limit for crankshaft welding and grinding.
« Reply #7 on: December 06, 2013, 05:49:27 PM »

You'll be around a 50mm stroke for a 75mm piston, which puts piston accel & speed very close to a D16 at 9k. That's about the max you'd want to run the vitara pistons. As far as offset grinding/welding, I'm not sure if removing & rewelding 1/3 of the journal is feasible. I wish I could find the magazine article that showed a b16 stroker buildup where the stroked it close to 1.8L, that would have been quite a bit of added material but still half as much as your goal.




Since you plan on using some Mazda parts, why not use half a 13B? :P
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DasPoop

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #8 on: December 07, 2013, 07:34:04 PM »

I found that they now sell cheap H beam d15 rods which will allow the vitara pistons and a just shy of 2" stroke will put me roughly zero deck height may have to skim the tops of the pistons .015 or something to make up for the 134.5<- wtf length d15 rods but its either that or do you think honing 1mm out of the id of the vitara pin bore is a problem? I would need new wrist pins but taking .5mm a side shouldnt disrupt the circlip too much I imagine. Otherwise I am on the lookout for some 26mm compression height 75mm pistons with a 20mm wrist pin lol.

Even still at 11k rpm with my obnoxious 2.6ish R/S ratio at 11k rpm my piston speed is only 3700ft/min
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Re: theoretical limit for crankshaft welding and grinding.
« Reply #9 on: December 08, 2013, 01:45:40 AM »

I've seen crazy R/S motors where the benefits of a long rod were cancelled out by the extra weight.

As far as enlarging the wrist pin area, just keep the new bore parallel to the old. Any competent machinist could ream them out to exactly what you need, as well as increase the circlip depth. The next size up c-clip will work, but you'd be better off using sprial-locks if possible.
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DasPoop

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #10 on: December 08, 2013, 05:10:10 AM »

I've seen crazy R/S motors where the benefits of a long rod were cancelled out by the extra weight.

As far as enlarging the wrist pin area, just keep the new bore parallel to the old. Any competent machinist could ream them out to exactly what you need, as well as increase the circlip depth. The next size up c-clip will work, but you'd be better off using sprial-locks if possible.

I can do the machine work I just need to see where the ping pack lands if I am going to need to run oil support rails or not. I need the rod just to come back to zero deck height. Plus Idk why but the package just works.
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Random Hero

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Re: theoretical limit for crankshaft welding and grinding.
« Reply #11 on: March 18, 2014, 08:38:44 PM »

do you think the top end has any chance of living if reved to 11k in a road race? Hmmmm. what will you do to keep the roughly 110psi of oil pressure you will need to zing that high for that long? Just idea's as i've ran into these issues.
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