Dowl Pinning!@!!!!!
#1
standard combustion
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Dowl Pinning!@!!!!!
HOW is it done?! I really need to do this to my next engine block to avoid cracking the rear endplate I did today. So someone must know how. What are some other measures to prevent this type of cracking to the rear plate besides abstaining from from high boost.
#2
BDC Motorsports
It's done by machining out the housings to accept several more dowel pins. The idea is to keep the housings (particularly the rotor housings on the combustion side) from being forced away from the end plates. I honestly think that it comes more from spikes in the combustion chamber caused by severe engine knock over anything else (and hence may be a bandaid if that's the only reason why these things stretch and move), but I could be wrong about that.
B
B
#3
Banned. I got OWNED!!!
too much timing or too lean! i believe you have a small turbo , so its definatly got to do with your tuneup! what kind of gas were you running and with how much boost?
#4
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The crack is at the dowl by the oil filter, I know its cracked there since nothing else is the source of the oil leak. This is at 14-15psi, 92octane, no detonation or knock has occurred. S4 turbo.
Its not running lean, if anything is too rich across the board. I've been meaning to get some smaller main jets and maybe 1-2different air bleed jet sizes larger to lean it out a little more at higher rpm.
Would using shrinkwrap (like from Hayes rotary) on the tension bolts possibly reduce the stress on the dowls by transfering some of the load on the dowls to the tension bolts in the block? As there is a gap between the tension bolts and the holes in the engine. With less gap the flex should be less, correct?
I just don't want to hear that I can't run 14psi once in a while without the fear of cracking the rear dowl by the oil filter because its too weak to support combustion pressures that high in a 12a block.
Its not running lean, if anything is too rich across the board. I've been meaning to get some smaller main jets and maybe 1-2different air bleed jet sizes larger to lean it out a little more at higher rpm.
Would using shrinkwrap (like from Hayes rotary) on the tension bolts possibly reduce the stress on the dowls by transfering some of the load on the dowls to the tension bolts in the block? As there is a gap between the tension bolts and the holes in the engine. With less gap the flex should be less, correct?
I just don't want to hear that I can't run 14psi once in a while without the fear of cracking the rear dowl by the oil filter because its too weak to support combustion pressures that high in a 12a block.
#6
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you are running 14-15psi with a S4 turbo, your HP levels are no where near high enough to begin to stress the plates, it has to be either Detonation, or Pre Ignition that has caused the plate to crack
#7
Rotary Freak
iTrader: (1)
the shrink-wrap thing will do nothing to reduce stress on
the dowel pins. I am about to try to pin a motor,
i have enough old housings to do a few test tries before taking
a chance on good ones
I don't think its that big a deal, and not worth what
a couple rotary shops charge that i know of.
matt
the dowel pins. I am about to try to pin a motor,
i have enough old housings to do a few test tries before taking
a chance on good ones
I don't think its that big a deal, and not worth what
a couple rotary shops charge that i know of.
matt
Originally posted by WackyRotary
Would using shrinkwrap (like from Hayes rotary) on the tension bolts possibly reduce the stress on the dowls by transfering some of the load on the dowls to the tension bolts in the block? As there is a gap between the tension bolts and the holes in the engine. With less gap the flex should be less, correct?
Would using shrinkwrap (like from Hayes rotary) on the tension bolts possibly reduce the stress on the dowls by transfering some of the load on the dowls to the tension bolts in the block? As there is a gap between the tension bolts and the holes in the engine. With less gap the flex should be less, correct?
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#8
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you are running 14-15psi with a S4 turbo, your HP levels are no where near high enough to begin to stress the plates, it has to be either Detonation, or Pre Ignition that has caused the plate to crack
Remember also this is not a S4 block, its a S4 turbo fitted to a 12a, so i assume 12a blocks have less strength in the dowl area. There is no leak into the combustion chamber, it runs great(no oil/coolant loss), its just the rear dowl area has the leak right between the "MAZDA 12A" on the rotor housing and the rear endplate right above the temp sensor were its leaking oil.
So either even a very light amount of detonation caused too much stress on the dowl and cracked, or the o-ring failed, or the endplate was warped and sprung a leak there?
#9
Re: Dowl Pinning!@!!!!!
Originally posted by WackyRotary
HOW is it done?! I really need to do this to my next engine block to avoid cracking the rear endplate I did today. So someone must know how. What are some other measures to prevent this type of cracking to the rear plate besides abstaining from from high boost.
HOW is it done?! I really need to do this to my next engine block to avoid cracking the rear endplate I did today. So someone must know how. What are some other measures to prevent this type of cracking to the rear plate besides abstaining from from high boost.
Probably detonation, though you didn't hear it. Even if it did not detonate, per se, at the verge of detonation the cylinder pressures will more than double. One or two degrees of timing can make all the difference, even if you are not lean. I would recommend that you pull the motor apart and thoroughly inspect it for other signs of detonation-related damage -- stationary/internal gears, bearings, etc.
#10
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Man that looks A LOT more severe then what I probably got, I'm sure oil was gushing out of that! OR did the crack spread while untensioning the tension bolts it I suppose?
Either way, I guess i need to re-think the max boost and dial the timing better and ignition improvements to retard timing since I have only a locked distrubuter now.
But from the looks of that, it had to of detonated at a pretty high boost level, Right?
Thats a S4 endplate also, right?
Either way, I guess i need to re-think the max boost and dial the timing better and ignition improvements to retard timing since I have only a locked distrubuter now.
But from the looks of that, it had to of detonated at a pretty high boost level, Right?
Thats a S4 endplate also, right?
#11
Originally posted by WackyRotary
I could not hear any detonation(yes I know what it sounds like). I have the timing set near stock 12a settings. IF is retarded any from this, it would start backfiring like crazy going past 5psi, then I bumped it up little by little till it smoothed out with higher boost and kept it there, I'm sure the timing gets more and more critical as boost is increased. I was going to set it with a timing light when I got access to one, but it was probably had more retard then it needed to be.
Remember also this is not a S4 block, its a S4 turbo fitted to a 12a, so i assume 12a blocks have less strength in the dowl area. There is no leak into the combustion chamber, it runs great(no oil/coolant loss), its just the rear dowl area has the leak right between the "MAZDA 12A" on the rotor housing and the rear endplate right above the temp sensor were its leaking oil.
So either even a very light amount of detonation caused too much stress on the dowl and cracked, or the o-ring failed, or the endplate was warped and sprung a leak there?
I could not hear any detonation(yes I know what it sounds like). I have the timing set near stock 12a settings. IF is retarded any from this, it would start backfiring like crazy going past 5psi, then I bumped it up little by little till it smoothed out with higher boost and kept it there, I'm sure the timing gets more and more critical as boost is increased. I was going to set it with a timing light when I got access to one, but it was probably had more retard then it needed to be.
Remember also this is not a S4 block, its a S4 turbo fitted to a 12a, so i assume 12a blocks have less strength in the dowl area. There is no leak into the combustion chamber, it runs great(no oil/coolant loss), its just the rear dowl area has the leak right between the "MAZDA 12A" on the rotor housing and the rear endplate right above the temp sensor were its leaking oil.
So either even a very light amount of detonation caused too much stress on the dowl and cracked, or the o-ring failed, or the endplate was warped and sprung a leak there?
crispeed
87 RX-7 TII
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un-tubbed
#13
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Originally posted by WackyRotary
Stock yes, locked to max advance.
Stock yes, locked to max advance.
i would have thought you would have wanted it locked on about 5 degrees before TDC (leading)
#14
On all my blow-thru set-ups I would pull the springs and lock the timing at full advance for boosted conditions which would normaly be in the 12-15 deg on the leading and 0-5 deg for the trailing.
crispeed
87 RX-7 TII
9.204@150.47mph
2600lbs
un-tubbed
crispeed
87 RX-7 TII
9.204@150.47mph
2600lbs
un-tubbed
#16
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On all my blow-thru set-ups I would pull the springs and lock the timing at full advance for boosted conditions which would normaly be in the 12-15 deg on the leading and 0-5 deg for the trailing.
Crispeed, what boost level were you running and what engine setup were you running it on? I really would feel disappointed that a 12a n/a has to be below 14psi or fear the rear dowl cracking again. I want a ceiling of 14-15psi since that is what I built the engine for with the setup.
Help me guys!@! What other measures besides dowling the hell out of it to strengthen it or other way to reduce stress on the rear dowl. I don't want to have that happen again, and I still want to run 14psi on occation for timed runs. Normally I will only go up to 8-10psi max from now on. And if I don't get a good answer, I guess I'll have to keep it low for engine longevity/rebuild costs.
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You could sandwich a 6mm aluminium plate between the black and sump. And hold it in place with larger sump bolts, simply machine out the holes and rethread them, and then u kill 2 birds with 1 stone you also get a sump baffle as well.
#18
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You could sandwich a 6mm aluminium plate between the black and sump. And hold it in place with larger sump bolts, simply machine out the holes and rethread them, and then u kill 2 birds with 1 stone you also get a sump baffle as well.
So this is basically a thick plate with some baffle holes for the oil. So you have special holes drilled into the iron plates to bolt it rigidly to the block along with all the oil pan holes?
Anyone else ever heard of this?
#19
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What a/f you running??? mid 11's with 12 degrees total advance some heat range 9 plugs and a ignition amp should have you running great.
Maybe your just running soooo rich that your ignition cant combust it all, that can be just as bad as running lean sometimes
STEPHEN
Maybe your just running soooo rich that your ignition cant combust it all, that can be just as bad as running lean sometimes
STEPHEN
#20
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What a/f you running??? mid 11's with 12 degrees total advance some heat range 9 plugs and a ignition amp should have you running great.
I am using TII/FD NGK's with the heat range of 9 for both L and T. I do agree I should use a ignition amp/multi spark unit. It however was running great the way it was. Very fast and very smooth power across the board with no simptoms of detonation.
#22
OK Here is my 2 Cents.....I have a 12a and I have cracked both the front and rear housings. In fact when I cracked the rear housing not only did it crack a LARGE chunk of the casting was missing I could easily feel the dowl pin from the outside of the motor (that was some real oil gushing) That was at stock timing at 7 lbs yes 7!!! Beacuse I had CHEAP gas in the car. (My turbo is quite large though & I have a Jerico which I believe puts a huge torque strain on the motor)
I have been racing/driving rotaries for 17yrs now and Ive found the ONLY way to insure that you do not have harmful detonation is to use a quality high octane fuel (period) If you want to have a race car choose any two of the following:Cheap, Fast, Reliable. My motor is pinned I made 516hp at 24lbs on 118FNL I have made 100's of passes and driven the car on the street and burned 5-55 gallon drums (so far) and have had not a single problem (except for breaking rear end parts constantly) (PS its getting back-halfed right now) Ill let you all know how it runs when I do! So the moral is use good gas!
I have been racing/driving rotaries for 17yrs now and Ive found the ONLY way to insure that you do not have harmful detonation is to use a quality high octane fuel (period) If you want to have a race car choose any two of the following:Cheap, Fast, Reliable. My motor is pinned I made 516hp at 24lbs on 118FNL I have made 100's of passes and driven the car on the street and burned 5-55 gallon drums (so far) and have had not a single problem (except for breaking rear end parts constantly) (PS its getting back-halfed right now) Ill let you all know how it runs when I do! So the moral is use good gas!
#23
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Or cheaper yet, buy a Aquamist system!
You can run pump gas with H20 injection and get all the benefits of running race gas.
Since I have installed mine, I have not had a hint of detonation.
You can run pump gas with H20 injection and get all the benefits of running race gas.
Since I have installed mine, I have not had a hint of detonation.
#24
Senior Member
Is there anybody who has any pics of a fully dowelled side housing? I am gonna build a streetported 20B for a customer in Norway so i got to have some info/ideas.
#25
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I'd like to see some visuals too. I'm sure there is no trade secret in this since its only for making the engine more durable to withstand higher boost levels.
POST THEM IF YOU GOT 'EM! PLEASE!
POST THEM IF YOU GOT 'EM! PLEASE!