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BionicBalls
Joined: 05 Jan 2009
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Location: Charlotte, NC
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fiat22turbo
Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR
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 Posted: Wed Feb 29, 2012 6:58 pm Post subject: |
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The Neon/Stratus/PT Cruiser 2.0/2.4L motrs came in SOHC and DOHC versions. Both are 16-valve heads and share bore spacing with the earlier 2.2/2.5L motors.
The bore spacing is similar to the 924's 2.0L, but the head bolts locations are completely wrong.
The Ford CVH engines (early Escorts) have a similar bore spacing as well. Not sure about the mounting holes locations.
Either way, even if the holes magically lined up, the oil and coolant ports likely won't.
For the amount of work involved, an Audi AAN conversion starts looking better and better, IMHO 
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose) |
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flosho
Joined: 01 Jul 2004
Posts: 3155
Location: Eau Claire, Wisconsin
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| Posted: Thu Mar 01, 2012 3:10 am Post subject: |
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Group buy in custom billet machined heads? 
I'm in. How many do we need to keep the cost under $2500?
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Mar 01, 2012 4:07 am Post subject: |
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| flosho wrote: | Group buy in custom billet machined heads?
I'm in. How many do we need to keep the cost under $2500? |
Heh, that would be a deal, considering a full-on big valve head with port job, hard-faced cam, and new lifters approaches $2K for parts and labor!
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erstwhile owner of just about every 924 variant ever made |
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tyfighter123
Joined: 19 Jan 2010
Posts: 551
Location: Colorado
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| Posted: Thu Mar 01, 2012 4:15 am Post subject: |
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Im in as well! lol it would be great to have an option like that.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car) |
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flosho
Joined: 01 Jul 2004
Posts: 3155
Location: Eau Claire, Wisconsin
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| Posted: Thu Mar 01, 2012 8:06 am Post subject: |
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| ideola wrote: | | flosho wrote: | Group buy in custom billet machined heads?
I'm in. How many do we need to keep the cost under $2500? |
Heh, that would be a deal, considering a full-on big valve head with port job, hard-faced cam, and new lifters approaches $2K for parts and labor! |
Yeah but I am talking $2500 for just the bare cylinder head. If it was a custom design you could probably adapt it to a more popular cam/valve train setup, so that the rest of the parts weren't as much.
I was reading a build thread once that a guy/shop made a billet 4g63 block. Maybe he is the one to contact about this problem. He is in Europe.
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Mar 01, 2012 8:14 am Post subject: |
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Thread drift 
Don't want to discourage the 16v head discussion, as it is fascinating...but would like to keep this thread focused on the stroker configuration...
...now, where did I put those piston catalogs??? Need to see about finding some more combinations with better potential quench...
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erstwhile owner of just about every 924 variant ever made |
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Martijnus
Joined: 29 Dec 2006
Posts: 2019
Location: Netherlands
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| Posted: Fri Mar 02, 2012 4:08 am Post subject: |
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| fiat22turbo wrote: | The Neon/Stratus/PT Cruiser 2.0/2.4L motrs came in SOHC and DOHC versions. Both are 16-valve heads and share bore spacing with the earlier 2.2/2.5L motors.
The bore spacing is similar to the 924's 2.0L, but the head bolts locations are completely wrong.
The Ford CVH engines (early Escorts) have a similar bore spacing as well. Not sure about the mounting holes locations.
Either way, even if the holes magically lined up, the oil and coolant ports likely won't.
For the amount of work involved, an Audi AAN conversion starts looking better and better, IMHO |
I'm still wandering off  but the problem with bolts/coolant holes can easily be solved. Cylinder spacing is the most important thing.
I've thought some more about the stroker plans and personally I wouldn't want to go beyond 2mm grinding. That means (in theory) a stroke enhancement of 4mm.
There could be alternatives. I've mentioned it before and the bigend is the thing to pick the rod on. Pistons can accomodate for any loss in length (but will influence the angle..)
I've checked Haynes today and the pistons are allowed to have 14gram difference in between, the conrods can have a whopping 100+ grams.
That's quite a bit and if you're able to reduce this differential, I think the crank needs less margin.
The reason I checked haynes was because I weighed my brand new Mahle 931 pistons and they were very close. The difference between the lightest and the heaviest was 1.3 gram
but they're heavy (541gr). And doesn't matter for this whole thread.
So if you can reduce the whole weight of the piston/rod combo and keep the weight in between as small as possible, I think the crankshaft can lose some flesh. How much exactly is a matter of testing... but the margins are getting f-ing tight.
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)
924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment  |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Fri Mar 02, 2012 4:52 am Post subject: |
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| Martijnus wrote: | | I've thought some more about the stroker plans and personally I wouldn't want to go beyond 2mm grinding. That means (in theory) a stroke enhancement of 4mm. |
A correction:
If you remove 2mm of material from the rod journal, you still only get 2mm of stroke because the centerline of the journal only moves 1mm. Of course, to calculate stroke, you need to double the amount that the centerline moves, but that puts you right back to the 2mm figure you removed from the journal. Neat, eh!?
The maximum amount of additional stroke for this configuration is with the rod that has the 45mm journal, i.e. stock big end is 51.6mm, new big end is 45mm, difference is 6.6mm. That is the maximum amount of additional stroke you can get (well, sort of, you can get a helluva lot more if you want to weld and regrind, but that's what we're trying to avoid). For reference, the weld-&-regrind stroker I developed using the Crower rods and Diamond pistons has an additional 6.35mm of stroke.
When I asked my guy about the amount of material being removed from the journal, he said it was no big deal, he was not worried at all about going that small. Bear in mind, this is the stock journal size on the stock application for a late model 4-cylinder engine with both high compression NA and turbo-charged applications. So there is nothing inherently wrong with a 45mm journal.
It's pretty much consensus view that the 924 crank and rods are way beefier than they probably need to be. So unless my crank guy comes back after inspecting the crank and identifies something in the manufacture of it that warrants concern, I don't believe there is any reason to be worried about going down to 45mm journals.
| Martijnus wrote: | | There could be alternatives. I've mentioned it before and the bigend is the thing to pick the rod on. |
A clarification:
It's not just the big end bore. It's a combination of:
- big end width that is close enough to stock; and
- big end bore that is equal or less than stock
Big end width MUST be within fractions of a mm to accommodate the required crank centering. Big end bore MUST be <= 51.6mm. Those are the two most critical dimensions.
The center-to-center length, as you indicate, is not so important because it can be paired with a piston of correct compression height to achieve the desired CR and block clearance (although, that's another challenge I'll come back to in a moment).
The key issue is finding a rod with the right thickness and big end bore. I have looked through literally dozens of catalogs and hundreds (if not thousands) of rod dimensions. The two rod options I've identified are the ONLY ones I could find that met both the width and bore requirements (one having a slightly larger width, the other a slightly smaller width).
There are plenty of rods that are close on the bore, but every single one of them are WAY too narrow to be used because of the crank-centering design. I can't stress this enough. I'm not saying there aren't other rods out there that I haven't discovered, but I have searched every catalog I can get my hands on and have found exactly TWO rods that will work for this approach.
(Incidentally, the 944 rod is very close, but the big end bore is too big and would require UP-sizing the journal, so that was right out.)
| Martijnus wrote: | | Pistons can accomodate for any loss in length (but will influence the angle..) |
This is true, but custom pistons cannot be had for less than $700 a set. Of course, there's no reason custom pistons couldn't be used with these rods.
The trick to finding the lowest cost solution is to find a piston with the correct compression height that will work with a 150mm length rod, and also has the correct bore as well as the correct pin diameter. Again, I've scoured hundreds (if not thousands) of piston dimensions. I have a candidate list of about 2 dozen off-the-shelf pistons right now that will work to achieve compression ratios varying from 7:1 all the way to 12:1 (and higher, if desired).
One nice thing about purchasing off-the-shelf aftermarket rods and pistons is that they will almost certainly be balanced to better tolerances than OEM units...including our own.
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tyfighter123
Joined: 19 Jan 2010
Posts: 551
Location: Colorado
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| Posted: Fri Mar 02, 2012 5:20 am Post subject: |
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Dan, what is the cost of the off the shelf rods? Why not use the collective talents here to make our own design that will work with off the shelf pistons and have it manufactured? If costs were about equal wouldn't that be the best option?
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car) |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Fri Mar 02, 2012 5:31 am Post subject: |
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| tyfighter123 wrote: | | Dan, what is the cost of the off the shelf rods? Why not use the collective talents here to make our own design that will work with off the shelf pistons and have it manufactured? If costs were about equal wouldn't that be the best option? |
Custom rods are a minimum of $800-$900, and when I inquired before, Crower was the only shop I could find that would do them in one-off jobber batches. Many of the rod manufacturers won't do custom rods at all, and most that do require minimum buy in (i.e. Oliver, Pauter, etc. And these guys want like $1200 per set too!!!).
Off-the-shelf rods are ~$350 (this is directional only at this point, not a quote!!!); stroking the crank is $200-$250; add $170-$200 to nitride (if it's even necessary).
You're still at a lower cost than custom rods, with the added benefit of having A) a longer rod; B) a longer stroke; C) a higher static compression ratio (all else being equal); and D) no waiting (custom rods take 8-10 weeks to make).
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ideola
Joined: 01 Oct 2004
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Location: Spring Lake MI
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| Posted: Fri Mar 02, 2012 5:34 am Post subject: |
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Actually...
| Quote: | | Why not use the collective talents here to make our own design that will work with off the shelf pistons and have it manufactured? |
...I've already done this. My custom Crower long rods, which I'm currently running in the 941, are exactly that. 150mm center-to-center. They could be spec'd with 21mm or 22mm wrist pins to be used with any of the off the shelf pistons I've identified. So I already have that option available, albeit at a higher cost and without it being a stroker setup.
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tyfighter123
Joined: 19 Jan 2010
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Location: Colorado
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| Posted: Fri Mar 02, 2012 5:49 am Post subject: |
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| Quote: | | ...I've already done this. My custom Crower long rods, which I'm currently running in the 941, are exactly that. 150mm center-to-center. They could be spec'd with 21mm or 22mm wrist pins to be used with any of the off the shelf pistons I've identified. So I already have that option available, albeit at a higher cost and without it being a stroker setup. |
Very true, what I meant was if we could use the custom Crower rod design that you already have and have them copied into a CAD file (unless you already have that) and then manufactured at a cheaper cost (as Gegge mentioned in his feeler post it) it may be a great option, if it can be done for around the $350 that off the shelf rods would cost. If not then finding one already in production is the best way to go. Either way I'm excited to see what you come up with and would like to help in anyway I can.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car) |
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tyfighter123
Joined: 19 Jan 2010
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Location: Colorado
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| Posted: Fri Mar 02, 2012 5:55 am Post subject: |
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Also as you mentioned before with the custom pistons already identified and able to work with your custom crowers the cost has already gone down a lot. Now if we can get rods made to our specs, avoid the crank work and come in under the cost of crowers and have a stroker we are still money ahead and have a better engine.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car) |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Fri Mar 02, 2012 7:07 am Post subject: |
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| tyfighter123 wrote: | | avoid the crank work ...and have a stroker |
Just to clarify, there is NO WAY to increase stroke without modifying the crank. The long rod does not make it a stroker (but has it's own benefits). The increase in stroke can only come by modifying the crank, i.e., specifically by moving the rod journal further out.
On my original strokers, this was accomplished by welding additional material onto the journal, and then offset grinding it to the original big end dimensions. In this case, the offset grind literally moved the journal all the way to the end of the crank shoulders, as far as it could be moved, thereby increasing the total stroke. (What we later learned was that the stock rods interfered in the crankcase, so we had to get custom Crower rods made up with lower profile shoulders to avoid this interference. Our original intent was to use stock rods...).
For the package I'm proposing here, the rod journal itself is not actually being moved, but the reduction in its diameter effectively moves the centerline of the journal, which is the important point to grasp. In so doing, the stroke is increased by the same amount as the material removed from the journal, as explained a few posts up, even though the journal itself is not actually "moved". Voilą. Cheap stroker.
Now for some details on long vs. short rod theory.- INTAKE STROKE: A longer rod will "suck" harder from 90° to BDC; to understand the importance of this, a shorter rod will require a better cylinder head than with a longer rod to produce same peak HP. And we all know how great our cylinder heads are, right?!
- COMPRESSION STROKE: With a longer rod, the piston travels from BDC to 90° BTDC faster than short rod, which produces higher CR, all else being equal. The piston spends more time at TDC, which provides more efficient combustion at high RPM, meaning MOAR POWER!
- POWER STROKE: With a longer rod, the piston will be further down in bore for any given rod-crank pin angle, meaning less force is exerted on the crank pin than a shorter rod. Smaller crank pins can be used (proposed setup reduces crank pin from stock 24mm to 22mm or 21mm), meaning less weight in the reciprocating mass.
- EXHAUST STROKE: With a longer rod, the piston will force more exhaust out because it spends more time from BDC to 90° BTDC; if exhaust port is poor, a longer rod will help peak power...and again, we all know how fantastic our heads are, right?!
- OTHER BENEFITS: A longer rod will have less rod angularity throughout the throw, meaning less side loading of the piston-to-cylinder wall interface, resulting in less wear, less noise, and less friction (i.e. MOAR POWER!!!). A longer rod also amplifies the benefits of increasing the stroke, most notably the increase in torque from higher displacement, and the increase in power from higher CR.
The sources I studied indicated that an increase of 2.5%-5% is required to achieve noticeable difference. Increasing our stock 144mm to the proposed 150mm is just over 4% increase. Perfect!
After feeling the long rod + high compression setup in the 941, I am convinced that all of these benefits accrue to a noticeable change in the responsiveness of the car. It hasn't been dynoed yet, so I am making no claims as to power increase; but the car just revs and feels more responsive than any of my other cars. (The 937 overtakes it at the top end, no doubt due to the intercooler).
So here's my current lineup:
-- 941 has long rod but no stroker.
-- Club Sport has stroker but normal rod.
-- SONIC will get long rod AND stroker. With high compression pistons.
The only drawback I could see to the longer rods is that they can sometimes produce more detonation-prone conditions, primarily due to the increase in both static and dynamic CR. Consequently, I will probably dial the CR back to ~10.7:1 on SONIC. The pistons I've identified will not have an ideal quench area because they're not purpose built for the deck height we have, so detonation will be a definite issue to watch for; CBass had 11:1 on his NA (using NA head with S2 931 pistons) and was getting ping with 94 octane, so I'm going to dial back just a bit from 11:1, and hope that the aftermarket piston dish and combustion chamber in the 931 head provide better detonation resistance than his setup. Since the NA head is a snap to remove, my fall back plan will be to go with a thicker Cometic gasket if 10.7:1 is too pingy.
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