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914World.com _ 914World Garage _ Short-stroke / big-bore
Posted by: Prospectfarms Mar 23 2012, 12:19 PM
Saw a video of a 1911cc motor running and it sounded pretty good. It was carbureted and sounded "cammed." Makes me wonder what 96mm jugs do for a otherwise stock 1.7 engine.
Nothing wrong with 1.7 liters, but I really liked a 1835'ish cc type 1 put in a Beetle a few years ago. Torquey and very quick but reliable.
What happens if I increase piston diameter on this short stroke engine? (I'll cross the MPS bridge when I get there.) 96mm by 66mm sounds weird, I'm trying to imagine how it would feel. Maybe even not worth doing? Don't think the valve seats were ever replaced on this engine so I'll have to send the heads out regardless.
Ideally, I would increase stroke and displacement, but changing the cam, rods and crankshaft + everything else sounds like more than I'm willing to spend.
Posted by: vsg914 Mar 23 2012, 12:51 PM
Theres a lot of them out there. 1911 cc. Great upgrade to a 1.7.
Posted by: Prospectfarms Mar 23 2012, 01:56 PM
Theres a lot of them out there. 1911 cc. Great upgrade to a 1.7.
Thanks Curt, I speculate 66 x 96 feels like the 1.7 but your going faster. Compared to my experience with stroked motors of this displacement range where you get power earlier?
I loved Ham's suggestion I read a while back of building a 78 x 90(stock cyl.) 1985cc, but that is more work and $ than I'm looking for.
Posted by: rdauenhauer Mar 23 2012, 02:45 PM
Very nice motor. less "lazy" than stock 2.0L but with equivalent pwr.
I mean lazy in that the stroke of the 2.0 provides torque w/o reving it, the 1.9 needs to be spun 
Posted by: 02loftsmoor Mar 23 2012, 03:15 PM
That's what I've been checking on, big bore kit for my 1.7. keeping the stock FI and putting in a FI torquey cam. any thoughts?
Posted by: 914_teener Mar 23 2012, 05:35 PM
That's what I've been checking on, big bore kit for my 1.7. keeping the stock FI and putting in a FI torquey cam. any thoughts?
That is my plan but:
I am not convinced to keep the stock D-jet. I have run out of spare parts.
Since the D-jet is hardmapped to the VE curve it will need to be adjusted. So my first plan is to install a wide band AFM to make sure I can adjust the MPS and get good at it if I keep the stock injection, or go with the M-squirt straight away.
Watching a few thread on this board until I make the decision.
Posted by: pete-stevers Mar 23 2012, 08:19 PM
this is my build plan for the future as well...but will be running a cis rabbit sys on mine...but would love to hear what the "Jake Miester" has to say about a build up of this sort and his thoughts for what components should be matched for optimum longevity or performance
Posted by: Black22 Mar 23 2012, 08:53 PM
I just built a 1911 from a 1.8L. Going to keep the L-jet too. Rebuild is complete and I have yet to install it and break it in. Super excited! It should be back in the car in about a month. I only get 1 day a week to work on it and am waiting on two more parts for other areas of the engine bay.
Posted by: Jake Raby Mar 23 2012, 09:16 PM
We've only built a few of these... The combo can be really fun, but its really easy to over cam them and I'd always keep a high speed port profile with this combo.
I have made 177HP with one of these combos as a race engine in the past..
Posted by: Prospectfarms Mar 24 2012, 12:07 AM
Useful information. Thanks very much. Now we have to come up with a catchy name for it. "Big bore" is oversell. "Ricer," nah, that's taken. Maybe, "The Combo?"
177 HP???? That must have been a high-revving beast. Neat.
Posted by: Prospectfarms Mar 24 2012, 12:12 AM
I'd always keep a high speed port profile with this combo.
AKA, smallish, or stock, (1.7) valves?
Posted by: messix Mar 24 2012, 01:19 AM
I'd always keep a high speed port profile with this combo.
AKA, smallish, or stock, (1.7) valves?
valves are not the concern, it would be the port volume.
the short stroke will have a slower piston speed compared to a longer stroke, this have an effect to where the intake pulse into the combustion chamber wont be as strong there by you would need a smaller port volume to encourage a higher velocity through the head. the valve can still be larger than stock to allow less restiction from the port to the combustion chamber.
Posted by: Bleyseng Mar 24 2012, 04:15 AM
That's what I've been checking on, big bore kit for my 1.7. keeping the stock FI and putting in a FI torquey cam. any thoughts?
That is my plan but:
I am not convinced to keep the stock D-jet. I have run out of spare parts.
Since the D-jet is hardmapped to the VE curve it will need to be adjusted. So my first plan is to install a wide band AFM to make sure I can adjust the MPS and get good at it if I keep the stock injection, or go with the M-squirt straight away.
Watching a few thread on this board until I make the decision.
Pretty easy to do just install a Raby cam like a 9550.
Posted by: 02loftsmoor Mar 24 2012, 09:30 AM
What's your thoughts on a cam profile with stock FI. And a big bore kit
Wes
We've only built a few of these... The combo can be really fun, but its really easy to over cam them and I'd always keep a high speed port profile with this combo.
I have made 177HP with one of these combos as a race engine in the past..
Posted by: Prospectfarms Mar 24 2012, 11:30 AM
What's your thoughts on a cam profile with stock FI. And a big bore kit
Wes
We've only built a few of these... The combo can be really fun, but its really easy to over cam them and I'd always keep a high speed port profile with this combo.
I have made 177HP with one of these combos as a race engine in the past..
Search (+1911 +cam) and you'll get all the info you want. #9550, or similar. "Massive Type!V" used to sell a "kit." and I believe still stocks the correct cam. Ask him directly.
Posted by: 749142 Mar 24 2012, 02:15 PM
great engine... very reliable and fairly powerful. i prefer the 1911's over the 2056's.
Posted by: 02loftsmoor Mar 24 2012, 03:35 PM
why is that, smoother, easy revs ???
Posted by: Al Meredith Mar 24 2012, 07:35 PM
I have both a 2056 and a 1911. The 2056 has much more torque. My 1911 has 1.8L heads and a raby cam (all the parts come from Jake). I think if you go to www.aircooledtechnology.com Jake has a dyno chart for both engines. You can compare for yourself.
Posted by: Black22 Mar 24 2012, 08:28 PM
I've got a stock cam and 2.0L heads. I wonder if that's on the chart?
Posted by: rdauenhauer Mar 24 2012, 09:53 PM
That was the recipe I used.. stock cam, 2.0L heads, induction & exhaust
It Rocked!
Of course I had a little help from Geoff dialing in the MPS using his LM1.
Posted by: Prospectfarms Mar 24 2012, 10:13 PM
I have both a 2056 and a 1911. The 2056 has much more torque. My 1911 has 1.8L heads and a raby cam (all the parts come from Jake). I think if you go to www.aircooledtechnology.com Jake has a dyno chart for both engines. You can compare for yourself.
That's interesting, seat-of-pants feedback. Thanks.
Posted by: rick 918-S Mar 25 2012, 06:53 AM
Very nice motor. less "lazy" than stock 2.0L but with equivalent pwr.
I mean lazy in that the stroke of the 2.0 provides torque w/o reving it, the 1.9 needs to be spun
According to a conversation I had with a BMW engine building guru (a guy like Jake for BMW enignes) the connecting rod ratio for the 1.7, in this case would be 1.9092 equal an engine that has a 9000 rpm potencial. That is if all other parts will take the abuse.
We had an engine combo that ran long Audi rods and Type IV pistons. It moved the ratio from 1.6875 to 1.7000= 7000 rpms. That changed the harmonics and stoped the engine from jerking the rod on the down stroke and breaking it off just below the wrist pin. In a 2002 that was really a nice little screamer.
It's my understanding that Jakes cams are broad based and smooth over the entire range which would make for a very nice improvement.
Posted by: Prospectfarms Mar 25 2012, 07:40 AM
Nine. That would be something...
Posted by: Jake Raby Mar 25 2012, 08:04 AM
I have turned one of those 1911s with the stock rod ratio 9,000 RPM..
Posted by: Dr Evil Mar 25 2012, 08:06 AM
I always loved this idea Its more fun to drive a slo car fast 
Posted by: Prospectfarms Mar 25 2012, 08:14 AM
I always loved this idea
Its more fun to drive a slo car fast Bingo.
Posted by: Prospectfarms Mar 25 2012, 08:17 AM
I have turned one of those 1911s with the stock rod ratio 9,000 RPM..
Modified springs and hardware on top? I'm getting hot and bothered about this.
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