dowel or studing?
11-16-07, 02:23 AM
#27
Rotary Enthusiast
Can you guess which one I was referring to regarding the dowelling and studding? I'm not trying to detract from the other of course.
David, ask him about it next time you talk to him. He has your rotating assembly doesn't he? He was able to answer some of my questions regarding engine flex that no one has clearly answered because they simply don't understand what is happening.
All I'm saying is that you don't need a stud kit to make the power. It's kind of like ceramic apex seals; you don't need them to make the power but if you want the best and perhaps a bit more room for error or bigger safety margin, then by all means, go for the goods.
What happened to this engine from flexing and what brokenn parts did he have to replace?
I have and it won't and so have many others over the years.
Perhaps you should listen to some of your own advice.
David, ask him about it next time you talk to him. He has your rotating assembly doesn't he? He was able to answer some of my questions regarding engine flex that no one has clearly answered because they simply don't understand what is happening.
All I'm saying is that you don't need a stud kit to make the power. It's kind of like ceramic apex seals; you don't need them to make the power but if you want the best and perhaps a bit more room for error or bigger safety margin, then by all means, go for the goods.
What happened to this engine from flexing and what brokenn parts did he have to replace?
I have and it won't and so have many others over the years.
Perhaps you should listen to some of your own advice.
When the engine got dyno it worked fine untill the last pull when they pushed the boost up to 18 psi on the GT42R turbo. They dynoed about 580rwhp at 6500 rpm and then suddenly there was a loud metal noise and they let of the gas and the engine died instant.
They then tried to start it up again but it was hard to crank. So they figured something had broken. Not knowing what it was. So when he took the engine apart he got a nice suprise. First of all the stock tension bolts where abit hard to get out since they wernt straight anymore, same with the stock dowels. And when he opend the engine he got a nice look at the damage internaly. First there where large grooves in the rotor 2 back rotor houses from something and the apex seals where jammed down in the rotor from something. Then there where realy bad scratches on the side walls from the sideseals that had poped out of it's track. The eccentric shaft had some nasty scratches on it after something, and the main rotor barings on the back to 2 rotors where gone. Both back rotors where damaged as well in the apex grooves and side seal grooves.
So what he neded to replace was the following. Back housing, small midle housing, large middle housing, 2 rotor housings, 2 rotors and the eccentric shaft. And all the stock dowel pins and bought a 12.7mm stud kit.And he also changed all the bearings in the engine.
The front rotor did not have any dmg, except for some uneven wear mark on corner seals and apex seals. I would have replaced the front iron and the front rotor housing as well tho. But it did cost him alot of money. And it's not a funny experience.
The rebuilt the engine and dynoed it again. And now the engine has been running for a year or so without any problems. So this is why im saying this. Do not go high hp on a 20b without studs.
JT
11-16-07, 03:01 AM
#28
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I agree 100%. My first 20b broke the top dowel hole on the fat centre plate. Thankfully this was before they went obsolete & I was able to get another one! Since then every 20b (even my NA ones!) get a stud kit. There have been no more issues with broken motors since.
11-16-07, 09:55 AM
#31
if your setup is designed to spin/rev past 8k, I'm sure it would. You'll also need to do the center iron `oil mod` that David shared with us.
might wanna do something about the heat around those spark plugs too (since you're talking high revs [heat]).
11-16-07, 10:03 AM
#32
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Looking to put this in a mid engined "kit car" made for a LS1. Want to redline around 9,000rpm. OK, so that's a new one, are there any other mods for heat around the plugs besides the water jacket mod?
11-16-07, 10:44 AM
#33
There are quite a few - most of them are held secret by the engine builders and researchers who discovered 'em long ago.
for example - there is a huge waterpump mod that the top gurus hang on to... ever seen a water pump reaction from an air bubble / pocket hitting it?
i dont think there are too many people who share that type of information so I'd say scout the interweb or run your own coolent lines,pump(electric) etc. but you still have issues with getting the heat out of the rear iron (he gets real hot on high hp engines when hammering on the engine).
for example - there is a huge waterpump mod that the top gurus hang on to... ever seen a water pump reaction from an air bubble / pocket hitting it?
i dont think there are too many people who share that type of information so I'd say scout the interweb or run your own coolent lines,pump(electric) etc. but you still have issues with getting the heat out of the rear iron (he gets real hot on high hp engines when hammering on the engine).
11-17-07, 02:00 AM
#35
Would oversized studs have helped?
Perhaps, given their close proximity to the dowells, but you are also removing material from the housings themselves, making them less rigid, even if only minimally. Also, there is no stud running through the dowells and what happens is that the aluminum rotor housing "bulges" out right in that area due to the flame front and rotor traveling in opposite directions and the shape of the rotor housing compounds the problem. The result is that the outward force directed onto the dowell from the bulging aluminum rotor housing is transfered to the area surrounding the dowell in the iron. End result, cracked housing at the dowell.
I'd be interested to know if the crack in the iron was on the center rotor or front rotor side.
When the engine got dyno it worked fine untill the last pull when they pushed the boost up to 18 psi on the GT42R turbo. They dynoed about 580rwhp at 6500 rpm and then suddenly there was a loud metal noise and they let of the gas and the engine died instant.
First there where large grooves in the rotor 2 back rotor houses from something and the apex seals where jammed down in the rotor from something. Then there where realy bad scratches on the side walls from the sideseals that had poped out of it's track. The eccentric shaft had some nasty scratches on it after something, and the main rotor barings on the back to 2 rotors where gone. Both back rotors where damaged as well in the apex grooves and side seal grooves.
So what he neded to replace was the following. Back housing, small midle housing, large middle housing, 2 rotor housings, 2 rotors and the eccentric shaft. And all the stock dowel pins and bought a 12.7mm stud kit.And he also changed all the bearings in the engine.
The rebuilt the engine and dynoed it again. And now the engine has been running for a year or so without any problems. So this is why I'm saying this. Do not go high hp on a 20b without studs.
First there where large grooves in the rotor 2 back rotor houses from something and the apex seals where jammed down in the rotor from something. Then there where realy bad scratches on the side walls from the sideseals that had poped out of it's track. The eccentric shaft had some nasty scratches on it after something, and the main rotor barings on the back to 2 rotors where gone. Both back rotors where damaged as well in the apex grooves and side seal grooves.
So what he neded to replace was the following. Back housing, small midle housing, large middle housing, 2 rotor housings, 2 rotors and the eccentric shaft. And all the stock dowel pins and bought a 12.7mm stud kit.And he also changed all the bearings in the engine.
The rebuilt the engine and dynoed it again. And now the engine has been running for a year or so without any problems. So this is why I'm saying this. Do not go high hp on a 20b without studs.
It sounds to me like there was much more bad shat going on with that engine than what you think, probably none of which oversized studs would have helped.
Are you sure the tension bolts were more than just finger tight?
Until there is empirical proof or I see for myself, stud kits are just the latest bandwagon to jump on from people selling another product so we can all blow more money. All I've seen so far is a bunch of "he said, she said" crap in the peanut galleries, all of which most of us are all to willing to accept as fact. Granted, I'm not at the track week in week out surrounded by mega hp rotary gurus, but I do know and talk to a few.
That said, I know when/if I ever rebuild my 20b again, I'll be using oversized studs.
I still don't see it as necessary for the majority of applications but if you've got the mullah and are willing to spend a bit more on possible rebuilds and willing to deal with issues of getting a new housing machined correctly, then by all means.The (thick) center housing oil feed mod is a better and more economical mod, but I don't need to tell you that
A FFR GTM maybe?
That is SO what I want to do.
Actually, my dream of a p-port all aluminum n/a 4 rotor in one of those makes me feel warm and fuzzy all over. Of course I'd have to paint it orange and green with some white dashes to have my own version of the 787B.
11-17-07, 03:12 AM
#36
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That is a detonation/pre-ignition issue, not a twisting issue.
Would oversized studs have helped?
Perhaps, given their close proximity to the dowells, but you are also removing material from the housings themselves, making them less rigid, even if only minimally. Also, there is no stud running through the dowells and what happens is that the aluminum rotor housing "bulges" out right in that area due to the flame front and rotor traveling in opposite directions and the shape of the rotor housing compounds the problem. The result is that the outward force directed onto the dowell from the bulging aluminum rotor housing is transfered to the area surrounding the dowell in the iron. End result, cracked housing at the dowell.
I'd be interested to know if the crack in the iron was on the center rotor or front rotor side.
Would oversized studs have helped?
Perhaps, given their close proximity to the dowells, but you are also removing material from the housings themselves, making them less rigid, even if only minimally. Also, there is no stud running through the dowells and what happens is that the aluminum rotor housing "bulges" out right in that area due to the flame front and rotor traveling in opposite directions and the shape of the rotor housing compounds the problem. The result is that the outward force directed onto the dowell from the bulging aluminum rotor housing is transfered to the area surrounding the dowell in the iron. End result, cracked housing at the dowell.
I'd be interested to know if the crack in the iron was on the center rotor or front rotor side.
Do you know how much material is actually removed?? Sweet *** all!! But the studs that you put in there have minimal clearance, making the whole engine rigid. It was sitting on a 12mm think alloy plate, which I thought was enough to keep the entire block from moving. BLAH! I dont need studs - I have a 12mm thick engine plate YEA RIGHT!! At the time of studding, it also got solid dowels top & bottom & the "oil feed mod".
I seriously doubt it was a detonation / pre ignition issue as when the motor went back together it done a whole season of drag racing on the same tune!!
I have gone back to a 13b for this season & the first thing it got was a stud kit! Not so important for a 13b but I would list it as ESSENTIAL for a 20b!
