Alex052493

I have a na 1991 mazda rx7 and i'm going to rebuild the engine with new studs and t2 oil pan for later turbo upgrade. But I'm in the loop between getting a aggressive street port or just got for a bridgeport? this is not my daily but i would be driving it more frequently after the build. Would a bridgeport decrease the lifespan of the engine? if so by how much?
Secondly I know everyone always says never daily a bridgeport because it has poor drivability. What makes that porting give such poor driveability??
Lastly what would my hp be at if i do a aggressive streetport vs bridgeport? i have rb header and 3" straight pipe and a good fuel pump just missing changing injectors.

OG BBF

To be straight with you, your askin the wrong questions. You should have a power figure in mind, an end goal then you can do the mods required to achieve that.

In a nutshell Bridgeport is bad as a daily driven engine because....
A) It's so loud
B) High idle and lumpy low end acceleration due to the larger ports and virtually no engine vaccume
C) Fuel economy well let's just say you should run a hose from your fuel tank to inside the drivers area, that way you can fill up on the go! Jokes aside fuel economy is diabolical.

Engine wear comes into correlation with the above as bridgeports tend to run a lil hotter putting more stress on the engine. As I mentioned before give us a rough idea of what your goal is and people can best advise what's best for you. I can tell you first hand driving a Bridgeport daily is fun for the first month, after that and a few traffic jams later you'll hate your life 👍🏼

A large street port can get circa 500horses with supporting mods at a stretch, so you can kinda get an idea of what you need. Figures aside a bridge ported engine just sounds so arousing 🎉

Akaviri

iTrader: (1)

Do you mean you plan to rebuild the NA engine, swap a turbo engine, or turbocharge your NA engine?

If you intend to keep it NA, I would just street port it. You'd have a more usable power band and tolerable fuel economy. A bridge port is better left to a track car, where the engine is constantly screaming through gears at high RPM.

The vert is a heavier FC because of reinforcements to the chassis. Couple that with the already underwhelming torque/power of the NA 13B, and I think a turbocharger is the best bang for your buck compared to any porting. (If that wasn't already your plan)

Alex052493

I'm actually looking to get 200-210hp right now after the rebuild with porting for later to add standalone and turbo (my long term goal i'm happy with 400hp) but thats later on.
I honestly love that rough idle but everyone says it lumps to much at low rpms. right now the shop is giving me a free porting job and i could choose street or bridge for free

Alex052493

Akaviri, I would like to do a 6 port turbo, i dont plan on swapping for a turbo 2 so yes turbo charge my NA. The whole point of porting is because the shop is throwing in a free porting job for me of my choice since I'm doing the rebuilt there and also throwing in studs and turbo 2 oil pan. If not i wouldnt waste my money on a expensive porting job and i'll save it for the turbo upgrade

Aaron Cake

iTrader: (1)

On an NA engine, I don't recommend EITHER, especially if you plan to turbocharge later.

A reasonable street port that keeps the functionality of the aux port system and VDI, that does not put air velocity down low in the pooper.

Do the supporting mods: header, good exhaust, free up the air box. Make sure the car is in good tune generally.

Then go standalone. That will be your biggest power increase because a good tune makes a world of difference. And sets the stage for a turbo upgrade later.

OG BBF

most def street port. Bridge would be overkill and a terrible mismatch for those figures.

capn

Unless the engine is planed to LIVE at 8,500rpm then there won't be a lot of benefit to do either.

My only recommendation would be to clean up the castings and maybe port match the intake ports. Leave the port timing alone.

Alex052493

I've actually never heard anyone say to get neither lol so now I'm curious as to why in more detail. i do have headers and exhaust, i have a stock air intake and obviously stock ecu, I might be a rookie for this question but can one tune a NA with a standalone? i thought that was mainly for turbo. only reason i'm porting like i said before is because he's showing it in on the deal. so i shouldn't port the engine even if its a freebie??

lastphaseofthis

iTrader: (8)

you need to skip this guy, he doesn't know what hes doing. any one who recommends a bridgeport doesn't know what they are doing. if you NEED a bridgeport you can't be told by anyone else you don't... you know you need it and you know why you need it. to meet rules of a racing class.
he's showing it in on the deal? you me throwing in it. ?

Alex052493

He told me i can do whatever porting job i want that he'll throw that in for free when i do my rebuild with him.

clokker

iTrader: (2)

You can tune anything with a standalone ECU, it's just not generally considered cost-effective for a "normal" NA build.
The biggest advantage is that a standalone generally requires a much better sensor package (like AFM vs. MAF or the TPS), so input and resolution is much better and the resulting tune is much more precise.
It's a lot of work and money for not much return in the case of a NA.

lastphaseofthis

iTrader: (8)

i feel like when a standalone ecu, a lightstreet port or even stock port. on an custom upper intake manifold with s4 lower 6 port.. and all the little things to get the power there
I can turn an s4 or s5 motor, into the power of an rx8 engine. and it will be smooth from idle and no throttle. you can keep cruise control, and the thing will love a long life.

Aaron Cake

iTrader: (1)

Free porting? It takes me a solid working day, so a bit over 8 hours, to street port an engine to a quality I consider acceptable for a daily driver. Bridgeports add a few hours to that time due to the all the careful hole drilling, Dremel work with a tiny bit, housing notching (if you're not nothing, the bridgeports are too small). And then there's the cleanup of all that grit which admittedly a shop might be able to do faster if they have a hot tank or something. Point is, what builder is going to give away a whole day's labour? And the cost of consumables (a lot of duct tape to protect things, grinding bits).

Going further, if I was building engines for money, I'd even say "No free warranty on ported engines" because I know who gets their hand on these engines. No way would I absorb the cost of someone sticking a "aggressive" street ported block into a stock TII then coming to me complaining it blew up (conveniently not knowing that it was running 18 PSI with a FCD and no other mods).

Anyway, here's the explanation for saying no porting. But note I was only referring to an "aggressive" street port.

Most of the aggressive street ports for the 6 port irons massively hog out the aux ports to close a lot later. From the factory, the aux ports already have the closing timing close to a factory peripheral port. That is a lot of duration, cutting into the compression stroke. Designed to work with the DEI manifold. Hogging them out shifts the power band up. In many cases the fact these ports are now huge means the aux port valves can no longer work. So now you have a set of huge ports open all the time, making the midrange even worse than leaving the aux ports open on a stock port.

If you do want to port the engine, a conservative port template like the Mazdatrix 6 port template is the way go . Most of the work there is done on the primary ports, bringing then up to turbo closing times. The secondaries are opened a few degrees sooner, and the aux ports are given just a little more duration. It all works with the stock intake manifolds with little to no power band shifting if the aux ports are kept functional. About a 10 - 15% gain on stock ECU with supporting mods.

The 6 port irons already have PLENTY of port for a turbo setup if you really want to go that direction. Since turbocharging the engine usually means removing the aux port sleeves (not always, look at my Cosmo) then you actually want LESS port area and duration. But you kind of have to deal with what you have because it's not quite easy to add material to the irons with the engine assembled.

Turbo wise, depending on power goals, you can essentially set the torque curve through boost control (yes, this is a crude way of saying it, but for the sake of an easy discussion). Midrange a bit lacking due to big port area? Dial in more boost at that point in the map. Lots of sins are corrected with forced induction.

Bridgeports? Bridgeports are like the nastiest of race cams in piston engines. 100% overlap. Requires replacing everything attached to the engine (manifolds, management). If your builder even suggested this I seriously question their logic.

As for the standalone, you can standalone the hell out of ANYTHING. It won't be low before my snow blower is running a Megasquirt. What the standalone gets you is control far beyond Mazda's rather crude late 70s tune. There is a lot of power and response to be picked up in the midrange and high end by leaning the engine out, moving the split to zero at WOT and high RPMs, adding a bit of timing. In the idle to midrange, sequential injection allows adjustment of the injection timing to promote much better fuel distribution. With a good tune, and that is the key, you will make more power, run smoother and use less fuel "even" with an NA setup. I've only tuned a few NAs but 6 port 13Bs with basic porting, basic mods and a standalone in my experience are approaching wheel HP on the dyno. That's mainly tuning fuel and adding a bit of timing. The additional benefits meaning you can lose the 30 year old wiring and sensors, make the engine easier to work on, eliminate the redundant systems like the ASV and cold start thermowax, control things like fans, etc. Just whether the cost v. benefit of that works for you. And whether you can or have access to someone who can make all that happen with tuning.

Sideways7

iTrader: (7)

I had an NA a number of years back. It had a CAI, full exhaust, and a mild-moderate street port. It was quite quick and I never dyno'd it, but I would say it was close to your power goals. With a standalone, it will almost certainly get you there.

Now, I have a bridgeported turbo. Its amazingly quick, but there's definitely some trade-offs in the mileage and driveability areas. I think its worth living with that for the benefits, but I also drive it at most on weekends, and it sees track time. Bridges on a turbo also have added benefits in spooling the turbo, whereas in an NA it is purely for peak power at the expense of pretty much all else. The only way I could recommend a NA bridgeport, would be for when you need as much power as possible for racing and you can't turbocharge it due to the racing class.

Alex052493

I know the owner which is how i'm getting that hook up, It is one of the most respectable shops down here so its rep speaks for itself. I do have a question about the megasquirt, i recently start seeing more and more about megasquirt but what exactly is it? Is this like a adaptronic or power fc? Whats the difference and are they on the same price range?

jjwalker

On an NA, leave the intake ports alone, they flow enough already.

When I had engine rebuilt at RP, they did an experiment (which made it free!). They cut out the NA exhaust diffuser with a plasma cutter and hogged out my exhaust port. As far as intake, they just smoothed it out and barely touched it. They dyno'd it and got 200rwhp. I still had a cat at that time some my guess would be 210rwhp with the stock mammoth dynosaur cat removed. So, 210~ish on rwhp side.

They told me if I didn't want to go turbo, they could tune it with a standalone and make the car 250'ish in the HP range.

I got lucky, I signed an agreement that they where experimenting on my engine, and wheren't liable if bad things happened. It turned out good and it was free, and they where so impressed with the results, it had a 12,000 mile or 1 year warranty.

With that said, if your engine builder is agreeing to port your engine for free, it's because it's an experiment, he just isn't telling you. RP right off the bat as my budget dwindled ask me if they could do the experiment and throw it on the dyno. Buying new rotor housing and irons wiped out my budget for a street port, so Chris asked me if they could do an experiment, and I said okay.

Alex052493

Like i said previously, i know the owner of the shop, its not the mechanics its the OWNER hence the deal. Its not a experiment i still have to pay for the rebuild just not for porting. They've been doing this for years now with not one single bad review or customer. Agreed free **** like porting sounds sketchy but its not sketchy when its the owner of the shop giving you the deal, the mechanics still will get paid whatever they get paid, its just the owner takinf the loss if theirs any, but for me he doesnt care

Dak

I just wanted to add the Pineapple Racing template I used on my irons left the aux ports virtually untouched. It sounds like it is similar to the Mazdatrix one. Most all the work was enlarging the primaries and opening the secondaries sooner. Thus leaving the Aux port system operable if you so choose. I too would recommend ditching the exhaust diffusers. If you need new rotor housings this is easy just use turbo ones. Also I too would say don't go bridge if your going to be running the stock ecu for the foreseeable future. A street port like mine or jj's or the Mazdatrix you can get away with. They are also of the type Aaron seemed to recommend.

I would go spend a lot of time reading here: Naturally Aspirated Performance Forum - RX7Club.com

ACR_RX-7

iTrader: (1)

I also saw you mentioned going with a T2 oil pan. Why? They are identical to the NA pans.

The front covers are the parts that are different.

You should really consider what Aaron and JJ have said. They have first hand experience and JJ's engine mirrors your initial goals.

If anything, go with the Mazdatrix template and get supporting mods.



The Megasquirt is similar to the Adaptronic and PowerFC in capability, but there are several flavors to the MS.

You have the DIY kits you can buy and assemble yourself, saving money but at the expense of your own time.

The MegaSquirt 1 is capable of running a rotary in batch fire with minimal outputs and a 12x12 fuel table.

MS2 is a much faster version of the MS1 with more features and inputs/outputs

The MS3 has 16x16 tables for much better resolution, is much faster, and with the Expansion board, can handle 8 cyl sequential injection and ignition.

You can buy all of these assembled through DiyAutoTune.com


You can go all the way up to the MS3Pro, which is a fully assembled MS3 with the Expansion board in a nice Plastic case and a AmpSeal harness.

scathcart

Do you have a dyno sheet?
I don't see an exhaust ported, stock intake, stock ecu, stock cat engine making nearly 50% more power than stock.

jjwalker

Yeah, 5 years ago...

Why does it seem unreasonable?

scathcart

Because that's the same power level the RX-8 makes wth better intake, higher compression, better ports, higher redline....
It's only 20 hp down on the turbocharged FD engine...
It's also 30-40 hp higher than any oher FC N/A dyno with similar mods.

Sideways7

iTrader: (7)

I forgot that my NA engine had Turbo housings with the coolant passages plugged. I was told it was easier than trying to cut out the diffusers in the NA housings. Just be aware that it makes the car even louder.

Dak

Personally if a person needs new rotor housings( though the o.p. didn't say if he did) I really see no reason to even bother with n/a ones. Plugging the coolant passages on the turbo ones is way easier than grinding out those diffusers. From what I hear they are pretty tough. You can't really do any porting with the diffusers in the way either.