20B Cosmo - the twin turbo issue
12-08-03, 07:52 PM
#26
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Originally posted by RotorMotor
ok but if everything is tuning (and port configuration) why wouldnt mazda go for efficiancy... how is there so much power to be had simply by tuning the ECU.... surely mazda knew this..... well maybe not (maz-duh)
PS about using the 13b-rew housings... if i sent my 20b to pineapple or something for a rebuild/port would they port my 20b housings to 13b-rew spec. or is it better to replace the housings? (this is in the distant future as my 20b is still in the front clip, nad i have to fix everything in my donor car's engine compartment from an engine fire before i can move forward)
ok but if everything is tuning (and port configuration) why wouldnt mazda go for efficiancy... how is there so much power to be had simply by tuning the ECU.... surely mazda knew this..... well maybe not (maz-duh)
PS about using the 13b-rew housings... if i sent my 20b to pineapple or something for a rebuild/port would they port my 20b housings to 13b-rew spec. or is it better to replace the housings? (this is in the distant future as my 20b is still in the front clip, nad i have to fix everything in my donor car's engine compartment from an engine fire before i can move forward)
A second answer is, I think, the market for which the Cosmo was developed. At one time, there was an industry-wide limit of 280 hp in Japan, so going for 500 hp was pointless.
I've been told that there is a difference in the casting around the exhaust ports between the 20B and 13B-rew housings. As a result, you're ahead to just go to the 13B-rew style.
Since I don't do my own engine work, don't take my word for it. Talk to the folks at Pineapple.
12-09-03, 04:48 AM
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i definatly will give them a call. about having a 280 HP cap in japan... if they could just tune a rotary better why wouldnt they just use a 13b and juice it up? pettits cars w/ 550HP pass emitions dont they..... im not meaning to argue, i just dont understand maz-duh's approach
12-09-03, 07:30 AM
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Originally posted by RotorMotor
i definatly will give them a call. about having a 280 HP cap in japan... if they could just tune a rotary better why wouldnt they just use a 13b and juice it up? pettits cars w/ 550HP pass emitions dont they..... im not meaning to argue, i just dont understand maz-duh's approach
i definatly will give them a call. about having a 280 HP cap in japan... if they could just tune a rotary better why wouldnt they just use a 13b and juice it up? pettits cars w/ 550HP pass emitions dont they..... im not meaning to argue, i just dont understand maz-duh's approach
As a result, there was a period where all of the hot cars, for example, the Nissan Skyline, were advertised at 280 hp. When tested by car magazines, many of them were found to have more, sometimes much more, but the gentlemen's agreement on *advertised* horsepower was kept.
Somewhere in the last few years, that seems to have fallen by the wayside. Everyone knew that the "280" was bogus, and, IMHO, the need to compete with German and American high-performance cars pushed the Japanese into advertising real numbers.
As for Pettit's car passing emissions, I wouldn't bet on it. (I went to www.pettitracing.com. The Banzai link brought up a page which extols the car, but does not mention emissions.) I'm not saying that it couldn't. High-flow cats and careful tweaking of the EMC could produce a map that would pass emissions.
That's how Peter Farrell got his first 20B through Maryland emissions. (It helped that the technician at one, specific testing site was a Mazda enthusiast.
) The cat burned out on the way back to the shop from the testing site. Then, the real maps--the ones that would be rich enough to prevent pre-detonation--were restored.So, to summarize, Mazda's approach was dictated by marketing, cultural and legal pressures as much as by engineering concerns.
A recent example: Based on what I have read, it seems that the RX8s were detuned to generate slightly MORE emissions in order to keep the cats hot during cruising. This decision allowed Mazda to meet the 7-year requirement for emissions equipment longevity. As a result, the mileage and horsepower of the new car have been compromised negatively and generated a fair amount of bad publicity. Those drawbacks were accepted based on management's need to get the car to market AND meet regulatory requirements.
If that sounds a bit bizarre, read "Alice in Wonderland", and it will all begin to make sense.
12-09-03, 10:01 AM
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when an oem tunes a production car they have a bunch of other things on the list before power.
1. emissions
2. fuel economy
3. it cant blow up if you put the wrong fuel into it
4. its gotta be perfectly drivable by anyone
5. durability
so the oem tuning is a compromise they have a lot of other things to worry about before power, if you forget emissions, and tune it to only run on high octane fuel, and dont care how long it lasts you can get more power than mazda. mazda does know how to get power btw, they had a 450hp na 3 rotor in the 80's
i got a chance to ride in an stock ecu 20b truck last night, and its butter smooth. since both engines are stock we're gonig to dyno battle the only real difference is that mine has an aftermarket ecu in it
mike
1. emissions
2. fuel economy
3. it cant blow up if you put the wrong fuel into it
4. its gotta be perfectly drivable by anyone
5. durability
so the oem tuning is a compromise they have a lot of other things to worry about before power, if you forget emissions, and tune it to only run on high octane fuel, and dont care how long it lasts you can get more power than mazda. mazda does know how to get power btw, they had a 450hp na 3 rotor in the 80's
i got a chance to ride in an stock ecu 20b truck last night, and its butter smooth. since both engines are stock we're gonig to dyno battle the only real difference is that mine has an aftermarket ecu in it
mike
12-09-03, 10:02 AM
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oops
12-09-03, 10:43 AM
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Originally posted by j9fd3s
<snip>...and tune it to only run on high octane fuel, <snip>
<snip>...and tune it to only run on high octane fuel, <snip>
12-09-03, 12:46 PM
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Originally posted by RotorMotor
i dont know how pettit does it... either there is something we dont know, or theyre really just that good at tuning properly? however, if there is all this extra power available through proper tuning why would mazda decide to go with a 20b for the cosmo? wouldnt they rather properly tune a 13b, or a 1 rotor for that matter??? 550/3= 183HP!!! im sure mazda would have loved to throw a well tuned 7B turbo in a miata or something... it would be light as ****, and haul major ***!! something doesnt add up because mazda would not let all this "free" HP go that easily...especially with the 7 as they were trying to cut weight and production costs!!!
if its possible to crank 180HP out of a single rotor w/ a small turbo, the piston engine would have a lot of explaining to do!!!! this would be the ticket to rotary immortality..... think about what a single rotor would weigh
-heath
i dont know how pettit does it... either there is something we dont know, or theyre really just that good at tuning properly? however, if there is all this extra power available through proper tuning why would mazda decide to go with a 20b for the cosmo? wouldnt they rather properly tune a 13b, or a 1 rotor for that matter??? 550/3= 183HP!!! im sure mazda would have loved to throw a well tuned 7B turbo in a miata or something... it would be light as ****, and haul major ***!! something doesnt add up because mazda would not let all this "free" HP go that easily...especially with the 7 as they were trying to cut weight and production costs!!!
if its possible to crank 180HP out of a single rotor w/ a small turbo, the piston engine would have a lot of explaining to do!!!! this would be the ticket to rotary immortality..... think about what a single rotor would weigh
-heath
What they were looking for was an engine with plenty of torque to handle pushing a 1600kg car through an auto trans with some shred of performance. A highly tuned 13B wouldn't cut it for torque or reliability.
12-09-03, 06:58 PM
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beautiful!!!! im completely caught up... thanks everyone for all the detailed info... its kinda starting to make sense now.
BTW mike, let us all know the results of the dyno battle (im assuming hte truck is running a 5speed?). butter smooth is exactly what i thought the first time i drove an FD! i was used to glug glug glug, and shaking from my mustang gt that got stolen..... best thing that ever happend to me . the first time i ever drove a rotary, those were the exact words that went through my head... ahhhhh rotary..... long live the rotary
PS i rented X2 the x-men movie lastnight.... there getaway car was an rx-8.... i smiled
BTW mike, let us all know the results of the dyno battle (im assuming hte truck is running a 5speed?). butter smooth is exactly what i thought the first time i drove an FD! i was used to glug glug glug, and shaking from my mustang gt that got stolen..... best thing that ever happend to me
. the first time i ever drove a rotary, those were the exact words that went through my head... ahhhhh rotary..... long live the rotary PS i rented X2 the x-men movie lastnight.... there getaway car was an rx-8.... i smiled
12-09-03, 07:10 PM
#34
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the truck is a 5 speed, we're gonna dyno it with the afr chart and i'll match it with mine, and see whats up
12-19-03, 07:02 AM
#35
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Thread Starter
Originally posted by rotaspec
Mazda used 13Bs in most of the Cosmo's, only about 25% of the JC Cosmos had the 20B.
What they were looking for was an engine with plenty of torque to handle pushing a 1600kg car through an auto trans with some shred of performance. A highly tuned 13B wouldn't cut it for torque or reliability.
Mazda used 13Bs in most of the Cosmo's, only about 25% of the JC Cosmos had the 20B.
What they were looking for was an engine with plenty of torque to handle pushing a 1600kg car through an auto trans with some shred of performance. A highly tuned 13B wouldn't cut it for torque or reliability.
Mazda sold about 4916 (13B) + 3937 (20B) = 8853. Meaning 45% were the 20B option
The Cosmo was designed from the MX-03 concept car in 1985 which featured the 1st 3-rotor engine they did. This was to show the world that Mazda was a world class player & give the triple rotor technology a car to be showcased in.
12-23-03, 10:14 AM
#36
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Originally posted by Attila the Fun
1) 13B-rew housings - bigger exhuast ports equals more hp at higher rpm.
2) The previously mentioned turbo upgrade.
3) Porting the motor. (The chief mechanic for Kudzu Racing mentioned that he had once "thrown together" a turbo-20B for an enduro race. He mentioned that he did a "mild port", which he defined as less than a street port. The motor produced a reliable 550 hp., he said.)
180 hp per rotor isn't that far-fetched. Farrell was getting 600 hp from his 13B-rew drag car (700 with nitrous).
IIRC, there was a single rotor-powered motorcycle. It wasn't all that impressive from what I've read. FWIW, when Rick Potter and I visited Cam, at Pettit, in 2001, he was working on a 1-rotor motor. I don't know the outcome of the project, though.
1) 13B-rew housings - bigger exhuast ports equals more hp at higher rpm.
2) The previously mentioned turbo upgrade.
3) Porting the motor. (The chief mechanic for Kudzu Racing mentioned that he had once "thrown together" a turbo-20B for an enduro race. He mentioned that he did a "mild port", which he defined as less than a street port. The motor produced a reliable 550 hp., he said.)
180 hp per rotor isn't that far-fetched. Farrell was getting 600 hp from his 13B-rew drag car (700 with nitrous).
IIRC, there was a single rotor-powered motorcycle. It wasn't all that impressive from what I've read. FWIW, when Rick Potter and I visited Cam, at Pettit, in 2001, he was working on a 1-rotor motor. I don't know the outcome of the project, though.
01-10-04, 01:51 AM
#38
I have a dumb question...
I am looking at a factory exhaust manifold from a 20B. Which turbo spools up first?
Common sense says the smaller turbo does but common sense also says the (bigger) turbo with no flapper across the turbine entry does. Help!
Also, from what I can gather the second turbo (whichever one it is) comes in at around 3500rpm, Correct?
I am looking at a factory exhaust manifold from a 20B. Which turbo spools up first?
Common sense says the smaller turbo does but common sense also says the (bigger) turbo with no flapper across the turbine entry does. Help!
Also, from what I can gather the second turbo (whichever one it is) comes in at around 3500rpm, Correct?
01-10-04, 04:42 PM
#40
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it works off the front turbo until 3200-3500rpms (ive only been in 1 sequential 20b car and you cant really tell it comes on) and then it opens up the rear turbo to the rear rotor
01-10-04, 05:06 PM
#41
an idea to simplify the twins.
could a guy not remove all the junk that makes the twins
sequential and put a reed valve between the outlets
of the two turbos so that the first turbo doesn't loose
boost through the 2nd turbo, spinning it backwards?
this way the first turbo would start to make boost and
once exhaust flow gets the 2nd turbo up to speed its
flow would just be added to the 1st turbo through
the one way reed valve?
I maybe should have started a new thread for this
but this way only those following this thread will be privy
to this great idea
lol
matt
could a guy not remove all the junk that makes the twins
sequential and put a reed valve between the outlets
of the two turbos so that the first turbo doesn't loose
boost through the 2nd turbo, spinning it backwards?
this way the first turbo would start to make boost and
once exhaust flow gets the 2nd turbo up to speed its
flow would just be added to the 1st turbo through
the one way reed valve?
I maybe should have started a new thread for this
but this way only those following this thread will be privy
to this great idea
lolmatt
01-10-04, 10:43 PM
#43
well i dont think i have ever heard of anyone putting in
a reed valve to keep boost from going from the 1st
back through the 2nd one.
thats part of the problem with going non-seq the 2nd
turbo can be spun backwards from boost blowing back
through it before it has a chance to get up to speed, and
this is from what i understand very very hard on the
2nd turbo, causing shafts to snap etc.
matt
a reed valve to keep boost from going from the 1st
back through the 2nd one.
thats part of the problem with going non-seq the 2nd
turbo can be spun backwards from boost blowing back
through it before it has a chance to get up to speed, and
this is from what i understand very very hard on the
2nd turbo, causing shafts to snap etc.
matt
01-11-04, 01:36 AM
#44
Senior Member
Thread Starter
Originally posted by PDF
I have a dumb question...
I am looking at a factory exhaust manifold from a 20B. Which turbo spools up first?
Common sense says the smaller turbo does but common sense also says the (bigger) turbo with no flapper across the turbine entry does. Help!
Also, from what I can gather the second turbo (whichever one it is) comes in at around 3500rpm, Correct?
I have a dumb question...
I am looking at a factory exhaust manifold from a 20B. Which turbo spools up first?
Common sense says the smaller turbo does but common sense also says the (bigger) turbo with no flapper across the turbine entry does. Help!
Also, from what I can gather the second turbo (whichever one it is) comes in at around 3500rpm, Correct?
REgards
01-11-04, 01:36 AM
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really??? the setups are basically the same with the FD turbos right? i cant remember anyone mentioning this before.
PS how is progress coming on your car/engine??? did you ever work out the bugs w/ the ecu & turbos? i talked to pettit and they are making like 14psi on the stock turbos. they confirmed that they didnt do anything drastic to them... i think they are running non-seq.
anyway, im buying a subframe in a week so my fun will begin soon there after....... im getting scared!!! heath
PS how is progress coming on your car/engine??? did you ever work out the bugs w/ the ecu & turbos? i talked to pettit and they are making like 14psi on the stock turbos. they confirmed that they didnt do anything drastic to them... i think they are running non-seq.
anyway, im buying a subframe in a week so my fun will begin soon there after....... im getting scared!!!
heath
01-11-04, 01:53 AM
#46
rotormotor> if it was me that you were asking about.
I have been busy lately no time to work on any of the
car projects.
I have been running back and forth to the hospital for
a couple weeks now, nothing is wrong, unless you
consider having kids a problem a prospect i am still a
little unsure about.
matt
I have been busy lately no time to work on any of the
car projects.
I have been running back and forth to the hospital for
a couple weeks now, nothing is wrong, unless you
consider having kids a problem
a prospect i am still alittle unsure about.
matt
01-11-04, 05:46 AM
#47
Originally posted by DMRH
The larger front turbo is the primary one. The secondary turbo at the rear comes online at 3500rpm (4000rpm=FD RX-7)
REgards
The larger front turbo is the primary one. The secondary turbo at the rear comes online at 3500rpm (4000rpm=FD RX-7)
REgards
01-11-04, 11:16 AM
#48
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Originally posted by now
well i dont think i have ever heard of anyone putting in
a reed valve to keep boost from going from the 1st
back through the 2nd one.
thats part of the problem with going non-seq the 2nd
turbo can be spun backwards from boost blowing back
through it before it has a chance to get up to speed, and
this is from what i understand very very hard on the
2nd turbo, causing shafts to snap etc.
matt
well i dont think i have ever heard of anyone putting in
a reed valve to keep boost from going from the 1st
back through the 2nd one.
thats part of the problem with going non-seq the 2nd
turbo can be spun backwards from boost blowing back
through it before it has a chance to get up to speed, and
this is from what i understand very very hard on the
2nd turbo, causing shafts to snap etc.
matt
congrats on the kid, matt
01-11-04, 03:53 PM
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Originally posted by now
rotormotor> if it was me that you were asking about.
I have been busy lately no time to work on any of the
car projects.
I have been running back and forth to the hospital for
a couple weeks now, nothing is wrong, unless you
consider having kids a problem a prospect i am still a
little unsure about.
matt
rotormotor> if it was me that you were asking about.
I have been busy lately no time to work on any of the
car projects.
I have been running back and forth to the hospital for
a couple weeks now, nothing is wrong, unless you
consider having kids a problem
a prospect i am still alittle unsure about.
matt
Congratulations! best of luck to you in that department! so am i hearing twins???
Last edited by RotorMotor; 01-11-04 at 03:58 PM.