Legality of crank swaps
- Thread starter Z3_GoCar
- Start date
Andy Bettencourt
Super Moderator
This is a great question...
It is a good question.
I guess the easiest way to explain my opinion would be that if you swapped in the shorter crank, and what you ended up with was exactly the same thing as what you'd have in the car if you swapped in a 2.5L engine complete, and all you're doing is looking for a cheaper way to do it, then I'd say it's compliant. But if doing so would give you a performance advantage over a similarly-prepped 2.5L engine (e.g., the 2.8L engine has a better head/manifold/t-body), then you're likely contrary to the regs.
Just to be clear, above you said "rods and crankshaft" are free. Did you mean "rods and pistons"? Crank can be an alternate part but must be identical dimensions. Honestly, I'd like to clarify the intent of that rule, as I think it's a World Challenge holdover...but it's safest to keep IIDSYCTYC in mind.
GA
I guess the easiest way to explain my opinion would be that if you swapped in the shorter crank, and what you ended up with was exactly the same thing as what you'd have in the car if you swapped in a 2.5L engine complete, and all you're doing is looking for a cheaper way to do it, then I'd say it's compliant. But if doing so would give you a performance advantage over a similarly-prepped 2.5L engine (e.g., the 2.8L engine has a better head/manifold/t-body), then you're likely contrary to the regs.
Just to be clear, above you said "rods and crankshaft" are free. Did you mean "rods and pistons"? Crank can be an alternate part but must be identical dimensions. Honestly, I'd like to clarify the intent of that rule, as I think it's a World Challenge holdover...but it's safest to keep IIDSYCTYC in mind.
GA
I agree, and not because I don't think it's clear form the standpoint of the intent of the class (and tGA sumarized that well).
it's a great question because, going back to the first principle of the displacement to weight theory, why does it matter? if the ruesultant motor has 2500cc, then according to the concept, it should be wighted and run accordingly.
I support the "cost caontainment" or enforcement ability of running stock parts from the USDM etc... but the ruleset is, effectively, an excersize in identifying the best stock bottom end and head/intake/TB combination as offered in a car for sale in the US. displacement/weight only works if the other variables are removed. it can look close to right, but we all know better.
under the general pretenses of the class, I think that parts bin motors should be ok. I think that non USDM motors should be OK. and am apparently at odds with the CRB and many others.
I agree that it's easier and cheaper to have stock long blocks with the allowed modifications, as well as other implications of marketing and rule making import, but it simply doesn't add up from the engineering view.
Z3_GoCar
New member
So, this is the applicable section:
2. The crankshaft shall be a stock OEM part or
2. The crankshaft shall be a stock OEM part or
an aftermarket part
as long as it is of identical dimensions and material as the OEM
part for the specific engine. The crankshaft may be
part for the specific engine. The crankshaft may be
balanced.
The
maximum weight reduction allowance for balancing of the
crankshaft is 0.5 lbs. The
maximum weight reduction allowance
for the balancing of the reciprocating assembly is 15 grams.
Alternate connecting rods are permitted
Alternate connecting rods are permitted
, but must be ferrous
unless OEM supplied.
Part of the exercise is to get a better oe intake manifold, part is to keep the weight down. Dimensionally, my 84mm crank is the same as the 75mm crank except for the stoke. My rods are shorter than the 75mm crank, so I could also swap those out for a matching set. Also, head's the same casting.
Oh, one more twist. Does the intake manifold match the head or the crank? See I could use a newer generation 75mm crankshaft, but my head matches the older generation intake manifold.
unless OEM supplied.
Part of the exercise is to get a better oe intake manifold, part is to keep the weight down. Dimensionally, my 84mm crank is the same as the 75mm crank except for the stoke. My rods are shorter than the 75mm crank, so I could also swap those out for a matching set. Also, head's the same casting.
Oh, one more twist. Does the intake manifold match the head or the crank? See I could use a newer generation 75mm crankshaft, but my head matches the older generation intake manifold.
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James, you can't build a Frankenstein engine; you can only mimic the specs of an existing engine. If everything matches the specs of the BMW 2.5L engine (with STU allowances) then you're good. Otherwise, you're not. - GA
Z3_GoCar
New member
What you don't know Greg is that even oe and untouched it's a Frankenstein
BMW believes in evolutionary design changes, so multiple generations share common parts.
Matt93SE
New member
Here's my take on it...
In other words, you can not take a 2.5L crank and put it in a 3L block & head UNLESS BMW made a 2.5L engine using that specific combination of parts.
I'm glad this thread came up, since the non-USDM request has been denied, I'm trying to find another decent engine to put in the car. The only other "small" RWD engine Nissan has is the VQ25 from the Infiniti G25. 2.5L V6.
It's a baby-brother of the VQ35 in the G35 and 350Z.
The problem is Nissan only sells it as a long block (minus manifolds and lots of sensors), and it's around $8k. I haven't seen any on the used market yet for a junkyard donor.
Some of the Maxima guys have been Frankensteining these VQ engines for years using a 3.5L block and a 3.0L crank to come up with a short-stroke 2.3L engine that revs to 8,000,000,000rpm before throwing rods.
IF we can parts-bin an engine together using OEM parts, I could conceivably build a 'decent' engine doing that...
But the way I read the rules, that's not allowed.
In other words, you can not take a 2.5L crank and put it in a 3L block & head UNLESS BMW made a 2.5L engine using that specific combination of parts.
I'm glad this thread came up, since the non-USDM request has been denied, I'm trying to find another decent engine to put in the car. The only other "small" RWD engine Nissan has is the VQ25 from the Infiniti G25. 2.5L V6.
It's a baby-brother of the VQ35 in the G35 and 350Z.
The problem is Nissan only sells it as a long block (minus manifolds and lots of sensors), and it's around $8k. I haven't seen any on the used market yet for a junkyard donor.
Some of the Maxima guys have been Frankensteining these VQ engines for years using a 3.5L block and a 3.0L crank to come up with a short-stroke 2.3L engine that revs to 8,000,000,000rpm before throwing rods.
IF we can parts-bin an engine together using OEM parts, I could conceivably build a 'decent' engine doing that...
But the way I read the rules, that's not allowed.
What you don't know Greg is that even oe and untouched it's a Frankenstein
You know those engines better than I. If you can justify it to a protesting competitor, scrutineer, and subsequent appeals court, then that's all you need...but if someone says "hey, that's an intake from a 2.8 and a t-body from a 3.2, and a head from a 2.8 and a block from a 2.5, and that combo never came from any factory-delivered BMW" well...I'll buy the beer to watch the tech shed fun... 
GA
Nope. We've discussed the idea of allowing Frankensteins, and putting in some very-general class restrictions like t-body size, displacement, cam lifts etc and let people go to town. But right now I don't think it's something we're willing to tackle philosophically, and I personally don't think it's something the CRB would be will to entertain either. Let's let the dust settle for a while and see what shakes out, then we can discuss other options. - GA
Z3_GoCar
New member
GA
Well, here's proof they're Frankenstein's from the factory. I looked up the crankshaft part number, and here's the cars that share the same part number for this crankshaft:
Part 11211705848 (CRANKSHAFT W. BEARING SHELLS) was found on the following vehicles:
E34: Details on E34
E34 525i Sedan
E34 525i Touring
E36: Details on E36
E36 323i Convertible
E36 323i Coupe
E36 325i Sedan
E36 325i Convertible
E36 325is Coupe
E39: Details on E39
E39 525i Touring
E39 525i Sedan
E46: Details on E46
E46 323Ci Convertible
E46 323Ci Coupe
E46 323i Touring
E46 323i Sedan
E46 325Ci Coupe
E46 325Ci Convertible
E46 325i Touring
E46 325i Sedan
E46 325xi Touring
E46 325xi Sedan
E60: Details on E60
E60 525i Sedan
E83: Details on E83
E83 X3 2.5i SUV
E85: Details on E85
E85 Z4 2.5i Roadster
Z3: Details on Z3
Z3 Z3 2.5 Roadster
Z3 Z3 2.5i Roadster
Matt93SE
New member
Can I just keep kicking the JDM hornet's nest and see if they give in? that's the cheapest option to make 200whp in a <3L Nissan.
JoshS
New member
James, you can't do it, period. These aren't frankenstein motors. A frankenstein motor is a motor that's been built from combinations of parts that were never available together.
All of the engines that the 2.5L crank was in were 2.5L engines (go figure). So you can't put one in 2.8L block. What you *can* do is to use any BMW 2.5L engine you want to (and, you can piece one together using parts from your 2.8, but the result has to be identical to something that came stock in some US BMW).
So the question to ask is, which 2.5L do you want to build? I'd recommend an M54, but it would certainly be easier to build an M50 given what you've got in the car now, since you can keep your current head and intake manifold.
Mrsideways
New member
I've been trying to get this approved to put a Acura TSX rotating assembly in an S2000 block. So far it's a no go. The engine swap to the TSX motor or better yet a RDX motor is a lot of work and a lot of $$$$ custom made parts.
Last I checked, you are on the side of all USDM, why would you suggest that frankensteins be allowed and be against JDM swaps???
UNRELATED to Ian's post: second COA ruling in 6/11 Fastrack supports my (many) previous statements about ST being too confusing for the old guard / disinterested in tech. the IT in ST allowance causes too much confusion. I would agree that it should not, but people understand what they want to (see history of religious wars). the fact that the protested items were not at least documented in as raced condition is shameful. CoT should have points on his license.
Agree; I found it quite interesting (I'd not heard of it prior to Fastrack publication and have no other knowledge of it).
However, my take on what little info is offered is that the guy brought a World Challenge car to a National event assuming it was automatically approved for STU competition (as it was in 2010). We know, though, that all WC cars must be individual requested, weighted, and approved for use in STU. So what I think happened is that when he got protested, he took a different tack and said, "OK, so let's call it an ITR car". The SOMs said OK, he's good. But the protester realized (later, I guess) that the car was ineligible for ITR, so he appealed.
The Court of Appeals agreed that the car was ineligible for ITR. However, they noted the car had a 3L engine, which is STU-eligible. They overturned the SOMs and said (correctly) that the car was eligible for the open STU rules. In the end, depending on level of mods the car *may* actually be non-compliant to the STU rules but it was never inspected to that end; since they did not have the info needed to determine that, and the car on its face was eligible, the Court of Appeals overturned the Stewards and the protestee's finishing position stands.
IMO, based on what info it had, they ruled correctly. I would not be surprised to see another equipment protest in the near future...or maybe the protestee will send us VTS and request a specific WC allowance.
But yes, Chip, I agree that all these various allowances can be confusing. However, in this example I'd not blame the IT allowance; I think the ITR allowance was trying to be used as a loophole... - GA
JoshS
New member
We're all speculating here, but ... I doubt the car was an ex-WC car, since it apparently didn't have driveshaft straps.
And the fact that an '04 IS300 isn't listed in ITR is correct, but it's really an oversight, the years should have been extended to include the '03-'05 (and really should disallow the '01, since it never came with a manual transmission.)
In other words, what the owner should have tried is, "Okay, let's call it an '02, not an '04, and it's prepped to the ITR rules." That might have worked.
And the fact that an '04 IS300 isn't listed in ITR is correct, but it's really an oversight, the years should have been extended to include the '03-'05 (and really should disallow the '01, since it never came with a manual transmission.)
In other words, what the owner should have tried is, "Okay, let's call it an '02, not an '04, and it's prepped to the ITR rules." That might have worked.
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Mrsideways
New member
Because where does it stop in terms of JDM, GDM, Forumla one Motors etc etc. Frankenstiens are still policeable, whats your compression, whats your bore and stroke... Done. Or just allow any crank with that stroke, piston speeds are so mad your not going to be able to turn it up more with a stronger crank so it won't matter. I think I'd be ok with JDM swaps on a Case by Case basis. But the first thing that came to mind was an RB26 into a 240sx or a 3rotor in a Miata, Or the EURO E36 M3 3.0L in some sort of tiny light BMW. Or and this would be neat but a focus RS in a Fiesta. What's to stop one of these things from being undercover till the day before the runoffs and showing up as a "you forgot about this idea" 400whp monster.
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