(ENGINE) Ultimate Streetable 12a
04-12-06, 12:06 PM
#1
(ENGINE) Ultimate Streetable 12a
Hey Guys,
I've finally hammered out the definitive list of everything to be done in order to build what I consider the "perfect" streetable 12a. I wanted to share with you guys and get some feedback to find out if there's anything at all that I've missed. I think I've covered all the basics to get an engine that will last a *damn* long time, put up with lots of high revvs, and if I ever see the need to use forced induction in the future, it's future-proof.
I'm still debating whether to stay "street port" all the way around, or to do a half-bridge, where the secondaries are bridged but the primaries are street ported.
I've got a guy here in Canada who can not only resurface the irons down to 0.0005" but also re-nitride-coat them, so I'm hoping to get some serious longevity out of this.
In any case, here's the list, throw out to me what I've missed!
83-85 Rebuild Kit “C”
93-95 Corner Seal Springs
High-Flow E-Shaft Oil Jets
Rotor Bearing
3-window main bearings
S4 Water Pump
Pilot Bearing and Seal
Hardened Stationary Gear (front)
Hardened Stationary Gear (rear)
80psi Oil Pressure Bypass
High Pressure Oil Pump
OMP 2-stroke oil Adapter
“Front of Engine” Assembly
Side Housing Resurfacing
Side Housing Nitriding
Intake Street Porting
Exhaust Street Porting
Rotor Housing JHB Treatment
Race Clearancing of Rotors
Balancing of Rotating Assembly
83-85 Lightweight Steel Flywheel
Street/Strip HD Disc
Street/Strip HD Pressure Plate
I've attached the *.doc file which also lists where I'm getting these things and what the prices are. It also details the 'front of engine assembly' which I'll be getting from Mazdatrix, since I figure it's a good idea to replace it.
Jon
I've finally hammered out the definitive list of everything to be done in order to build what I consider the "perfect" streetable 12a. I wanted to share with you guys and get some feedback to find out if there's anything at all that I've missed. I think I've covered all the basics to get an engine that will last a *damn* long time, put up with lots of high revvs, and if I ever see the need to use forced induction in the future, it's future-proof.
I'm still debating whether to stay "street port" all the way around, or to do a half-bridge, where the secondaries are bridged but the primaries are street ported.
I've got a guy here in Canada who can not only resurface the irons down to 0.0005" but also re-nitride-coat them, so I'm hoping to get some serious longevity out of this.
In any case, here's the list, throw out to me what I've missed!
83-85 Rebuild Kit “C”
93-95 Corner Seal Springs
High-Flow E-Shaft Oil Jets
Rotor Bearing
3-window main bearings
S4 Water Pump
Pilot Bearing and Seal
Hardened Stationary Gear (front)
Hardened Stationary Gear (rear)
80psi Oil Pressure Bypass
High Pressure Oil Pump
OMP 2-stroke oil Adapter
“Front of Engine” Assembly
Side Housing Resurfacing
Side Housing Nitriding
Intake Street Porting
Exhaust Street Porting
Rotor Housing JHB Treatment
Race Clearancing of Rotors
Balancing of Rotating Assembly
83-85 Lightweight Steel Flywheel
Street/Strip HD Disc
Street/Strip HD Pressure Plate
I've attached the *.doc file which also lists where I'm getting these things and what the prices are. It also details the 'front of engine assembly' which I'll be getting from Mazdatrix, since I figure it's a good idea to replace it.
Jon
04-12-06, 12:12 PM
#3
I wanted to add that "streetable" doesn't mean I won't be doing *tons* of autocross with it, and possibly some track racing, I don't know yet.
But I didn't want to go full bridgey because this is my summer driver, so I wanted to go compromise. Just like my suspension (RB and KYB) I wanted performance, but not to the point where it wasn't streetable.
My basic outlook on the entire project is "If I were a Mazda engineer, building this car for myself instead of for the Mazda bean counters and the gov't (for emissions), what would I do to it?"
Jon
Edit: Nitriding internals, look up "brent clement" here on the forum. PM him.
The price I put in the *.doc file is approx, I got a specific quote from brent, but I don't know what his standard quote for that work is. I just guesstimated
But I didn't want to go full bridgey because this is my summer driver, so I wanted to go compromise. Just like my suspension (RB and KYB) I wanted performance, but not to the point where it wasn't streetable.
My basic outlook on the entire project is "If I were a Mazda engineer, building this car for myself instead of for the Mazda bean counters and the gov't (for emissions), what would I do to it?"
Jon
Edit: Nitriding internals, look up "brent clement" here on the forum. PM him.
The price I put in the *.doc file is approx, I got a specific quote from brent, but I don't know what his standard quote for that work is. I just guesstimated
04-12-06, 01:31 PM
#4
How about a short bridgeport on all 4 intake ports??
https://www.rx7club.com/showthread.p...t=bridge+short
Originally Posted by mazdized
All right I think it is time I put my 2 cents in here. My motor put out 220 at the wheel with 135 Ib running dual mufflers street exhaust and Holley 700 CFM. It peaked at 9,300 rpm. The porting was actaully not that aggrasive. I had the bridge port on the top portion so it actually has less over lap and later open timing compare to ones that are cut all the way down along the side of the main port. It closed relitively early, pretty close to stock turbo timing. The result is GREAT response and 22 mpg on high way below 75 mph. Supplement: The power came in about 5,700rpm and then gets a rush at about 8,300 rpm from the bridge ports. 9.2 comp. rotor ran 13.2 et @ 106 mph. 9.7 comp rotor ran 13.2 et. @ 112 mph.
The idle was lumpy and it would sit there and rock back and forth about 1200 rpm. When in gear it would run smooth as long as there is light load on it, lets say gradually accelerating or in fifth gear maintaining 65 mph. it would run smooth. But nuetral throttle or initial off throttle it would bark just like a 2 stroke dirt bike. The bridge port was only about 1 1/4 inch long but it was extended into the water O ring groove so it is like a cam with a lot of lift but relatively short duration. The power peaked at 9,300 and torque was around 6,700, it went to 11,200 rpm on that dyno run so at 9,300 that is all it had. How often it went over 8.500rpm? very often is the only way i can answer you, I usually shift at 9,500 when I am on it. The only problem I had was after about 2 years of street driving the silicone to seal the housing where the water O ring was cut started to leak. It will not over heat and may be loose a cup of water every week but it was wetting the plugs when you let the motor sit over night and making it difficult to start cold. 22 mpg was with a 85 GSL-SE 5speed with 0.711 fifth gear. With the heavier early rotors you will see signs of over reving but with 89 and up rotors if you stay low 9k rpm range it will be ok.
The idle was lumpy and it would sit there and rock back and forth about 1200 rpm. When in gear it would run smooth as long as there is light load on it, lets say gradually accelerating or in fifth gear maintaining 65 mph. it would run smooth. But nuetral throttle or initial off throttle it would bark just like a 2 stroke dirt bike. The bridge port was only about 1 1/4 inch long but it was extended into the water O ring groove so it is like a cam with a lot of lift but relatively short duration. The power peaked at 9,300 and torque was around 6,700, it went to 11,200 rpm on that dyno run so at 9,300 that is all it had. How often it went over 8.500rpm? very often is the only way i can answer you, I usually shift at 9,500 when I am on it. The only problem I had was after about 2 years of street driving the silicone to seal the housing where the water O ring was cut started to leak. It will not over heat and may be loose a cup of water every week but it was wetting the plugs when you let the motor sit over night and making it difficult to start cold. 22 mpg was with a 85 GSL-SE 5speed with 0.711 fifth gear. With the heavier early rotors you will see signs of over reving but with 89 and up rotors if you stay low 9k rpm range it will be ok.
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04-12-06, 02:45 PM
#8
Carbed all the way. IF I ever turbo in the future, I may go FI for the tunability, but for now I like things simple and mechanical. I deal with computers on a daily basis, so I have good reason to keep them the heck out of my car.
This amazing engine will be accompanied by an Rx7Carl/Sterling carburetor, ported intake, and an ISCracing.net airbox with K&N. This beast will be fed by a Mallory Comp70, regulated to proper pressure by a Holley 1-4psi FPR.
The carb/intake/airbox/fuel setup is already on the car (or will be as soon as I get it back from Carl. I was running the carb last year, but sent it back for a refresher and the intake/airbox/powdercoating) . Yes, it will need to be re-jetted for the new engine, but the improvement over stock was so great that I couldn't resist getting it first.
Jon
This amazing engine will be accompanied by an Rx7Carl/Sterling carburetor, ported intake, and an ISCracing.net airbox with K&N. This beast will be fed by a Mallory Comp70, regulated to proper pressure by a Holley 1-4psi FPR.
The carb/intake/airbox/fuel setup is already on the car (or will be as soon as I get it back from Carl. I was running the carb last year, but sent it back for a refresher and the intake/airbox/powdercoating) . Yes, it will need to be re-jetted for the new engine, but the improvement over stock was so great that I couldn't resist getting it first.
Jon
04-12-06, 06:42 PM
#10
Yeah... It's about a year away from actually being built, but I made the list now so that I could figure out what I was up against, and get some feedback from people as to what else I could do for this killer engine.
I think I'm going to be running a full advance timing of 24L/16T since I've seen that suggested many places. I'll be leaving the mechanical advance in place, but haven't decided on whether or not I'm leaving the vac advance on yet.
The ignition system accompanying this engine is an FC coil with TT box for the leading, and stock trailing. The leading will be running BR8EIX Iridium plugs, like the FC guys do. (yet again, all mods I've already done to the car). I have an FD alt already giving power, and an e-fan. Soon to switch to FMOC, to keep oil cool. I'll be running after market gauges for water temp, oil temp and oil pressure.
RB exhaust from front to back will be added (it's on the *.doc file already).
Jon
I think I'm going to be running a full advance timing of 24L/16T since I've seen that suggested many places. I'll be leaving the mechanical advance in place, but haven't decided on whether or not I'm leaving the vac advance on yet.
The ignition system accompanying this engine is an FC coil with TT box for the leading, and stock trailing. The leading will be running BR8EIX Iridium plugs, like the FC guys do. (yet again, all mods I've already done to the car). I have an FD alt already giving power, and an e-fan. Soon to switch to FMOC, to keep oil cool. I'll be running after market gauges for water temp, oil temp and oil pressure.
RB exhaust from front to back will be added (it's on the *.doc file already).
Jon
04-13-06, 11:08 AM
#15
I would strongly reccomend autocrossing your car. So you can get a membership @ http://www.mazdamotorsports.com , and buy parts directly from mazda AT COST.
That'll get the motor built much quicker.
That'll get the motor built much quicker.
04-13-06, 02:45 PM
#19
Originally Posted by peejay
I considered my P-port to be streetable.
Originally Posted by peejay
Deeply consider EFI no matter what porting path you take.
I'm also not *that* concerned about gas mileage and super-precise electronic tunability. Concerned enough not to full bridge or P-Port, but not concerned enough to stay stock or pay for an EFI system
And with ports as small as a half-bridge or street, you can tune it well enough with carb. Especially Sterling's carbs I just.... don't want computers in my car unless I have to
Jon
04-13-06, 03:23 PM
#22
Originally Posted by Alex-7
A sterling carb will fuel a bridge port?
Didn't know that.
You'll be using new Mazda seals for everything?
I like this project.
Didn't know that.
You'll be using new Mazda seals for everything?
I like this project.
But street port and *half* bridge the Sterling should do just fine. It will definitely need some TLC to tune it (but anybody who wants full power out of their car will do that anyway).
Yeah, new mazda seals all around.
Actually that brings up a good point... I saw a debate a long time ago on nopistons in the engine building section about solid corner seals vs. stock corner seals.
Anybody have opinions? They were saying that the soild ones were prone to cracking and wore the housings down too fast because of the shape of the groove in them, and suggested to use stock, even perhaps without the rubber insert.
Thanks for the tip wacky. It's a cheap alternative for sure, always good to note. I put the $75 one up there because this is sort-of a "no holds barred" streetable 12a rebuild wishlist. In my build I'll probably just do that.
Jon
04-13-06, 05:07 PM
#23
Old [Sch|F]ool
Originally Posted by vipernicus42
That's what I love about this forum, you guys are my kind of crazy!
The only nonstreetable part about it was that carburetion plus long, tubular intake runners plus a small plenum did not mix. Driveability was crap until the intake manifold heated up, which took about twice as long as the coolant. And if the ambient temps were under 60 degrees, getting it started was nearly impossible, there was an incredible amount of surface area, nice cold sheetmetal, for the fuel to condense on. It would flood and not get enough fuel at the same time
As I mentioned before, EFI was strongly considered, but I decided I'd rather run a carb if I'm not doing forced induction or anything bigger than a half bridge. (...) I'm also not *that* concerned about gas mileage and super-precise electronic tunability. Concerned enough not to full bridge or P-Port, but not concerned enough to stay stock or pay for an EFI system
I could understand it if you were doing the work in stages and wanted to spread the expenses out over time.
A MS computer can be had, completely assembled and tested, for $250. Compare that to a performance carb. You will need a new fuel pump anyway, and since you are building a new engine, use a GSL-SE center side housing so you can do the injectors easily. Actually, -SE injectors and fuel rail would finish the job nicely as well...
I'm just sayin'.
I just.... don't want computers in my car unless I have to
04-13-06, 05:25 PM
#24
Originally Posted by peejay
You're considering paying a bunch of money for stuff you don't really need, then you're going to cheap out on one of the most important things you can have, which is the fuel system?
I could understand it if you were doing the work in stages and wanted to spread the expenses out over time.
I could understand it if you were doing the work in stages and wanted to spread the expenses out over time.
Originally Posted by peejay
A MS computer can be had, completely assembled and tested, for $250. Compare that to a performance carb. You will need a new fuel pump anyway, and since you are building a new engine, use a GSL-SE center side housing so you can do the injectors easily. Actually, -SE injectors and fuel rail would finish the job nicely as well...
I'm just sayin'.
How do you like your vacuum-tube radio?
I'm just sayin'.
How do you like your vacuum-tube radio?
I've already replaced the fuel pump, and 70gph/6psi is more than enough for a street or half-bridge. The Sterling is quite tunable, and should offer enough fuel delivery for what I'm doing, and stay quite streetable in the process. I won't speak of price difference, but needless to say I didn't spend as much as a 'brand new' carb. Yeah the MS Comp can be had for $250, but there are all the other things I'd have to buy to complete the system, since I'm sure I can't just buy the MS computer, slap in an -SE intermediate and go. Plus the learning curve of going from carb to FI and the laptop that I'd invariably make myself buy for tuning
And I'd have to replace my fuel pump and FPR again!
But I see where you're coming from. Don't worry, I'm taking notes and may some day switch to EFI, but not today.
I may not have a vacuum-tube radio, but I do have a vacuum-tube amplifier for my stereo. Makes my vinals sound that much better
(and you should see my collection of mp3s.... god I walk both sides of the technology fence too often
)Jon
04-13-06, 06:23 PM
#25
Old [Sch|F]ool
Didn't realize you already had most of the fuel system goodies.
In that case, eh why not.
I assume you have the Holley/Carter pump. Be careful, it's not 70gph/6psi. It's 70 (well, 72) gph at *zero* PSI, and it's internally regulated to 6psi. It should still be more than plenty for *any* gasoline fueled non turbo rotary.
In that case, eh why not.
I assume you have the Holley/Carter pump. Be careful, it's not 70gph/6psi. It's 70 (well, 72) gph at *zero* PSI, and it's internally regulated to 6psi. It should still be more than plenty for *any* gasoline fueled non turbo rotary.
