dowelled pics
07-20-02, 07:55 AM
#1
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dowelled pics
Anyone has any pics of a dowelled motor or can they explain how it can be done cause i am thinking about doing it to my motor soon .
07-23-02, 06:10 PM
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There are multiple ways I've heard of doing this...
One, use of 12A dowel pins added to the existing 2 positions.  The 12A dowels are a little shorter, so the holes didn't need to be drilled straight through.
Two, use of very short pieces added in multiple positions.
Three, use of 13B dowels which end up looking like the stock dowel pins.
The reason for dowelling is to prevent the engine from twisting.  Twisting of the housing produces tremendous stress at the two, stock dowel points in the upper left and lower right (looking from the back of the engine).  Added dowels are located around the existing tension bolt holes.  Most of the tension bolt holes have coolant flowing through them, so these dowels need to be sealed from leaking coolant.
I've seen as many as 10 added dowel positions - most of them are added in the ignition/combustion and exhaust "cycles" of the rotor housing.
-Ted
One, use of 12A dowel pins added to the existing 2 positions.  The 12A dowels are a little shorter, so the holes didn't need to be drilled straight through.
Two, use of very short pieces added in multiple positions.
Three, use of 13B dowels which end up looking like the stock dowel pins.
The reason for dowelling is to prevent the engine from twisting.  Twisting of the housing produces tremendous stress at the two, stock dowel points in the upper left and lower right (looking from the back of the engine).  Added dowels are located around the existing tension bolt holes.  Most of the tension bolt holes have coolant flowing through them, so these dowels need to be sealed from leaking coolant.
I've seen as many as 10 added dowel positions - most of them are added in the ignition/combustion and exhaust "cycles" of the rotor housing.
-Ted
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07-24-02, 01:14 AM
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It seems strange that guys who have problems "twisting" and resultants - cracking end plates generally happens on hybrid set ups making 320-370HP.....
Lets face it, engine dont twist, no matter how many magazine articles that try to tell you this, Housings WALK sideways on the combustion side, they dont twist, on some housings (i think mazdatrix webpage has some) there are chatter type marks where the rotor housing (on the combustion side) has expanded/shifter outwards. Now some people believe this to be "twisting" but it certainly isn't. Some people believe that you need to add extra dowels, others do not. Some people say you need extra dowels to run over X psi - which is a crock of cr@p, as PSI has nothing to do with how much HP you are putting out. i think we should get Crispeed and RICE Racing in here to add there comments.
Cheers
Shane
Lets face it, engine dont twist, no matter how many magazine articles that try to tell you this, Housings WALK sideways on the combustion side, they dont twist, on some housings (i think mazdatrix webpage has some) there are chatter type marks where the rotor housing (on the combustion side) has expanded/shifter outwards. Now some people believe this to be "twisting" but it certainly isn't. Some people believe that you need to add extra dowels, others do not. Some people say you need extra dowels to run over X psi - which is a crock of cr@p, as PSI has nothing to do with how much HP you are putting out. i think we should get Crispeed and RICE Racing in here to add there comments.
Cheers
Shane
07-24-02, 04:48 AM
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I think Crispeed says 650RWHP, I think Peter (RICE RACING) say Dont need them.
Either way their aint many people on this forum who are pushing numbers high enough to warrant the possible need for them
Either way their aint many people on this forum who are pushing numbers high enough to warrant the possible need for them
07-24-02, 07:10 AM
#12
https://www.rx7club.com/forum/showth...ighlight=dowel heres a decent thread about it, w/ pictures that MIGHT help you understand.
07-24-02, 07:29 AM
#13
Banned. I got OWNED!!!
It is not required, from an Engineering point of view there is no need to undertake any such modification.
An engine that operates correctly i.e. does not have any abnormal pressure spikes at 1000bhp level in a 13B will result in a face mean load against the rotor housing of around 3 tonnes which is well within the limits of the rotor housing and the two steel locating dowles, and as a circular housing it is iherently one of the strongest engineering shapes in its resistance to deformation.
I repeat the only thing that will **** your engine is if your rotor crashes into your rotor housing (too high rpm/laod/or lack of clearance) or if you have detonation which increases the loads the engine sees by a factor of 4 to 5 times !!!
Which will break anything !
An engine that operates correctly i.e. does not have any abnormal pressure spikes at 1000bhp level in a 13B will result in a face mean load against the rotor housing of around 3 tonnes which is well within the limits of the rotor housing and the two steel locating dowles, and as a circular housing it is iherently one of the strongest engineering shapes in its resistance to deformation.
I repeat the only thing that will **** your engine is if your rotor crashes into your rotor housing (too high rpm/laod/or lack of clearance) or if you have detonation which increases the loads the engine sees by a factor of 4 to 5 times !!!
Which will break anything !
07-25-02, 08:34 PM
#14
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Originally posted by HWO
Lets face it, engine dont twist, no matter how many magazine articles that try to tell you this,
Lets face it, engine dont twist, no matter how many magazine articles that try to tell you this,
You might want to inspect some engines that have broken the dowel holes.  The cracks are consistent with a twisting force against the dowels.  This has been confirmed with Paul Ko with a mechanical engineer degree.
Housings WALK sideways on the combustion side, they dont twist, on some housings (i think mazdatrix webpage has some) there are chatter type marks where the rotor housing (on the combustion side) has expanded/shifter outwards.
Now some people believe this to be "twisting" but it certainly isn't. Some people believe that you need to add extra dowels, others do not. Some people say you need extra dowels to run over X psi - which is a crock of cr@p, as PSI has nothing to do with how much HP you are putting out. i think we should get Crispeed and RICE Racing in here to add there comments.
"Wear" marks on the rotor housing show that at extreme situations, the rotor housing actually "bow" outwards like a balloon.  How to do prevent this?  Not something we could figure out at the time...
Whether you point the finger at detonation or extreme boost/power, it still come down to almost the same effects - higher/elevated combustion pressures.  Sure, detonation is a sharper rise in pressure, but if an engine can stay together under detonation, it can surely stay together under higher boost/power.  Thus, steps taken to keep the engine together under detonation can be directly applied to higher boost/power levels for a rotary engine.
Dowelling was never a "requirement".  It's a safety mod - plain and simple.  The same thing can be said for boost/EGT gauges, knock displays, "race" fuel, intercoolers, larger wastegates...not required, but it's nice to be safe...
-Ted
07-25-02, 10:37 PM
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I would assume that a frount mounted engine (like in a FB) would have a lot more "twisting" forces on it than the rear mounted FD's? Whenever I see a pic of a 1st gen launching or picking up a wheel I just imagine how much force there has to be on that engine wanting to turn inside the engine bay. Think that could have anything to do with "twisting of the engine"?
07-26-02, 12:20 AM
#16
Originally posted by setzep
I would assume that a frount mounted engine (like in a FB) would have a lot more "twisting" forces on it than the rear mounted FD's? Whenever I see a pic of a 1st gen launching or picking up a wheel I just imagine how much force there has to be on that engine wanting to turn inside the engine bay. Think that could have anything to do with "twisting of the engine"?
I would assume that a frount mounted engine (like in a FB) would have a lot more "twisting" forces on it than the rear mounted FD's? Whenever I see a pic of a 1st gen launching or picking up a wheel I just imagine how much force there has to be on that engine wanting to turn inside the engine bay. Think that could have anything to do with "twisting of the engine"?
07-26-02, 12:51 AM
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Originally posted by setzep
I would assume that a frount mounted engine (like in a FB) would have a lot more "twisting" forces on it than the rear mounted FD's? Whenever I see a pic of a 1st gen launching or picking up a wheel I just imagine how much force there has to be on that engine wanting to turn inside the engine bay. Think that could have anything to do with "twisting of the engine"?
I would assume that a frount mounted engine (like in a FB) would have a lot more "twisting" forces on it than the rear mounted FD's? Whenever I see a pic of a 1st gen launching or picking up a wheel I just imagine how much force there has to be on that engine wanting to turn inside the engine bay. Think that could have anything to do with "twisting of the engine"?
07-26-02, 01:36 AM
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Ted - If others can build 700HP+ motors without cracking plates then why cant you?? if you are the 'great expert' that you claim to be and SOME people on this forum think you are.
Again, Why is it that about 95% of the people i hear about who crack end plates are running hybrid turbos and are only making 300-360ish HP at the flywheel? Is it that, that amount of HP has some kinda mystical stress factor that isn't seen again until 650+rwhp is seen, something like a Hayley's Comet type phenomenom. Or is it due to their intake air temps being too high because they are trying to force more air in than their factory exhuast housing/turbines can handle leading to large amounts of exhuast gas getting thru to the intake stroke meaning the cycle pre ignites putting imense pressure onto the top locatin dowel cracking the plate area around it?
What is harder and a more precise fit - the locating dowels or the engine thru bolts? Hmm i wonder which one allows the rotor housing to shift a bit and which one doesn't??? Thru bolts aren't an exact tolerenace with the rotor housings so they could allow a bit of 'slop' which would allow the top dowel to get enough pressure to crack.
Also, of all the people Who have cracked Plates ON THIS FORUM what kinda HP were they making at the time? Also how many people on THIS FORUM are making over 400Hp at the flywheel and have never cracked a plate? The numbers just dont add up for it to be a "twsiting" force. So it is starting to sound like this 300-350HP MUST be some mystic phenomenan mustn't it.
Again, Why is it that about 95% of the people i hear about who crack end plates are running hybrid turbos and are only making 300-360ish HP at the flywheel? Is it that, that amount of HP has some kinda mystical stress factor that isn't seen again until 650+rwhp is seen, something like a Hayley's Comet type phenomenom. Or is it due to their intake air temps being too high because they are trying to force more air in than their factory exhuast housing/turbines can handle leading to large amounts of exhuast gas getting thru to the intake stroke meaning the cycle pre ignites putting imense pressure onto the top locatin dowel cracking the plate area around it?
What is harder and a more precise fit - the locating dowels or the engine thru bolts? Hmm i wonder which one allows the rotor housing to shift a bit and which one doesn't??? Thru bolts aren't an exact tolerenace with the rotor housings so they could allow a bit of 'slop' which would allow the top dowel to get enough pressure to crack.
Also, of all the people Who have cracked Plates ON THIS FORUM what kinda HP were they making at the time? Also how many people on THIS FORUM are making over 400Hp at the flywheel and have never cracked a plate? The numbers just dont add up for it to be a "twsiting" force. So it is starting to sound like this 300-350HP MUST be some mystic phenomenan mustn't it.
07-26-02, 02:14 AM
#19
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I really doubt the cracking is from twisting forces... looking at it logically, if it were from twisting due to a torque reaction from the transmission mounting vs. the engine mounts (the alleged reason why FDs have the engine mounts on the rear end housing), then the dowel would break the housing UPWARDS.
But that's not what happens. The dowel breaks the housing downwards, as if the vaguely 8-shaped rotor housing were trying to expand into an O shape, pulling the dowel downwards and cracking the end plate.
Yeah, detonation causes it. Yeah, we have really shitty fuel up here (sometimes pump "gasoline" is so leaned out with alcohol and MTBE and other oxygenates that many carbed cars won't run at all unless the choke is held out!), and yeah, rotary tuners are much harder to come by. Yeah, the earlier engines are weaker than the later ones.
Some people have good luck, fine good for them, I bet they use good fuel too!
But that's not what happens. The dowel breaks the housing downwards, as if the vaguely 8-shaped rotor housing were trying to expand into an O shape, pulling the dowel downwards and cracking the end plate.
Yeah, detonation causes it. Yeah, we have really shitty fuel up here (sometimes pump "gasoline" is so leaned out with alcohol and MTBE and other oxygenates that many carbed cars won't run at all unless the choke is held out!), and yeah, rotary tuners are much harder to come by. Yeah, the earlier engines are weaker than the later ones.
Some people have good luck, fine good for them, I bet they use good fuel too!
