Reinforcing 13b engine block
10-11-12, 03:21 PM
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Reinforcing 13b engine block
I am in the process of building a S5 13b with a T66 with a goal of 400-450 whp. My main concern right now is getting a good tune on it and not breaking the dowel land area. I plan on running water/meth injection, egt, and someway to monitor knock and when building the engine I blocked off the oil passage that goes through the upper dowel pin with freeze plugs in both the front and rear irons. I have been doing a lot of research lately and have seen that dowel land cracking is a big controversy, sooo my question is has anyone tried reinforcing the block from the outside? My thinking was to possibly use some square tubing/angle to build a brace to connect the bolts in the tranny to the engine mount up to the bolts for the a/c compressor/powersteering bracket (with that bracket removed). Would this help or is this a stupid idea? lol
Thanks, Joe
Thanks, Joe
10-11-12, 10:34 PM
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Where did you get the idea to block off the oil passage? You need the oil through there to feed the front main bearing and OMP. If the car has not run I would not even try and start it. When it is disassembled if you are concerned about the engine twisting you should get extra pins machined in the housings.
EB Turbo
EB Turbo
10-12-12, 08:05 AM
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I got the idea from a thread by Judge Ito. I have drilled and tapped the oil passage that comes out of the front iron and ran a AN hose to the rear iron. The engine runs fine and makes good oil pressure and my omp still works.
10-12-12, 08:36 AM
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I didn't get extra pins machined in the housings because I don't have access to equipment that will meet that tight of tolerances and I didn't get a stud kit beacuse it was out of the budget. I am confused as to what actually causes dowel lands to break, I have read that it is from the rotor housing trying to push its way away from the iron from some kind of force. I am just wondering if reinforcing the block from the outside would keep it from flexing
10-12-12, 10:50 AM
#6
the oil bypass is more to reduce the need for an oil diaper. when you crack a rear iron you foul the track and that is no good.
with just the bypass you still can cause major damage inside the engine when/if it twists to the point of pinching seals and destroying a rotor/housing.
with just the bypass you still can cause major damage inside the engine when/if it twists to the point of pinching seals and destroying a rotor/housing.
10-12-12, 11:43 AM
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I'm not sure If I know what you mean by " foul the track", Are you meaning oil contamination? it seems as though from reading various instances of dowel land cracks the internal engine seals are fine, it just cracks causing an extreme oil leak and oil pressure drop. I placed freeze plugs just in front of the dowel pin in the front iron (oil can still exit out of the top for the turbo oil feed) and just behind the dowel in the rear iron (oil can still enter into the lower part of the rear iron and make its way up and through the oil filter). This should stop the oil leak/pressure drop from a cracked rear/front iron but the iron will still be weaker once cracked
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10-12-12, 11:49 AM
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I don't really wanna have to pull the engine back out for more pins/studs as I have just about got the engine broken in. Not to mention that from reading it seems as though dowel pin cracking has happened to engines with the added pins/studs as well. I'm just wondering if it would be beneficial to add some type of bracing to the engine as an added "insurance" since it wouldn't be too hard to fab/weld up some type of bracing for the engine.
10-12-12, 12:22 PM
#9
i can assure you the rear iron isn't the only thing that will break... the oil loop line won't save you a blown motor. if you only wind up with a broken iron then count yourself lucky.
unfortunately there's not many ways to reinforce the engine from the outside.
unfortunately there's not many ways to reinforce the engine from the outside.
Last edited by RotaryEvolution; 10-12-12 at 12:25 PM.
10-12-12, 12:55 PM
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Yeah, I didn't mean to make it sound like that is the only thing that does break. Just saying thats its weird how there have been instances where the engine will break a thick dowel casting but yet the internal seals which are thinner are fine and the engine can still run?
Flaco, yeah I agree that is another thing I was worried about. A major crack that goes beneath the freeze plug
It seems as though there isn't much consensus on why these cracks happen or what to do the prevent them
Flaco, yeah I agree that is another thing I was worried about. A major crack that goes beneath the freeze plug
It seems as though there isn't much consensus on why these cracks happen or what to do the prevent them
10-12-12, 04:44 PM
#12
because after the engine twists it returns to it's original formation, except the iron oil galley has been compromised.
i've even seen engines with cast aluminum pans crack a rear iron and destroy the rear rotor. this is 1/2" thick cast aluminum reinforcement at the deck of the motor..
when the rear rotor housing loses it's orientation far enough the rotor will contact the housing and at the very least pinch the seals.
i've even seen engines with cast aluminum pans crack a rear iron and destroy the rear rotor. this is 1/2" thick cast aluminum reinforcement at the deck of the motor..
when the rear rotor housing loses it's orientation far enough the rotor will contact the housing and at the very least pinch the seals.
10-12-12, 05:34 PM
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Because the Cast iron is a much harder more brittle metal than aluminum? I guess im going to ask the question... what causes the engine to flex/twist?
Detonation/High combustion pressure? Why wouldn't this cause a 2mm seal to break/lift before it would cause a housing to twist an entire engine and break a much thicker piece of cast iron?
I'm not questioning your experience on the matter, just trying to figure it out what really is going on when this happens to these engines
Detonation/High combustion pressure? Why wouldn't this cause a 2mm seal to break/lift before it would cause a housing to twist an entire engine and break a much thicker piece of cast iron?
I'm not questioning your experience on the matter, just trying to figure it out what really is going on when this happens to these engines
10-12-12, 07:30 PM
#14
it has alot to do with peak pressures in the engine and when the detonation occurs, you will notice more that large single turbos result in more broken irons and smaller stock sized turbos result in more broken apex seals.
if the engine is pinned for example it may be able to hold off the twisting but the rotors will cave in or the apex seals will blow.
if you place a rotor at TDC in the chamber against the plugs and picture the top chamber firing out of time you can envision the top of the rotor housing being forced downward which is how the irons tend to always crack. the rotor is not going to want to move in the reverse direction so the pressure applied to the trochoid face of the rotor housing attempts to twist the engine out of place.
if the engine is pinned for example it may be able to hold off the twisting but the rotors will cave in or the apex seals will blow.
if you place a rotor at TDC in the chamber against the plugs and picture the top chamber firing out of time you can envision the top of the rotor housing being forced downward which is how the irons tend to always crack. the rotor is not going to want to move in the reverse direction so the pressure applied to the trochoid face of the rotor housing attempts to twist the engine out of place.
Last edited by RotaryEvolution; 10-12-12 at 07:34 PM.
10-12-12, 07:49 PM
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because after the engine twists it returns to it's original formation, except the iron oil galley has been compromised.
i've even seen engines with cast aluminum pans crack a rear iron and destroy the rear rotor. this is 1/2" thick cast aluminum reinforcement at the deck of the motor..
when the rear rotor housing loses it's orientation far enough the rotor will contact the housing and at the very least pinch the seals.
i've even seen engines with cast aluminum pans crack a rear iron and destroy the rear rotor. this is 1/2" thick cast aluminum reinforcement at the deck of the motor..
when the rear rotor housing loses it's orientation far enough the rotor will contact the housing and at the very least pinch the seals.
10-13-12, 08:13 AM
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It does seems as though from what I have been reading that the big single turbo engines are more prone the cracking plates. Is this from the higher air flow or just more horsepower demand in general?
From your example I definitely can see how preignition/knock in the trailing area at TDC could cause this, another thing I find weird though is how the bottom dowel never cracks? I guess because knock never happens in that area of the engine? I would think that if the whole engine twists stress would be applied on that dowel as well?
From your example I definitely can see how preignition/knock in the trailing area at TDC could cause this, another thing I find weird though is how the bottom dowel never cracks? I guess because knock never happens in that area of the engine? I would think that if the whole engine twists stress would be applied on that dowel as well?
10-13-12, 08:41 AM
#19
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If it was engine torque twisting the engine, it would be breaking the dowel land upward.
Either way, the "fix" is to install additional dowels at the source of the force, near the spark plugs.
That, and don't detonate and never misfire under boost. Misfiring not only makes for funky shock loads on the stat gears, but it changes how many exhaust residuals are in the chamber the next time that rotor face comes around. You get more air, and the same amount of fuel, so it's just like having more boost and running lean.
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