PUSEHR

I'm Aiming to build a 200rwhp N/A FC, I'm more concerned with road courses than I am the drag strip. I here about people doing large raceports and bridgeports, but all they do is 1/4 races. I was wondering how these would hold up in a longer road race. So a couple questions.

1)Is it possible to get 200whp out of a moderate streetport?(I'm sure the answer is yes) OR would it be easier to go with a small bridgeport?

2)What else is needed with a bridgeport? I've read that you can use stock seals/internals and it will work fine. Will I have to buy bigger injectors? Also I'm guessing the stock ecu will go crazy with the added fuel and air, so I was wondering if a piggyback or standalone was NEEDED(I know that a standalone would be best)

3)Finally, this would be my daily driver, luckily I dont have to travel far daily. What kind of gas mileage could I expect? I've heard its bad gas milage but is it l15mpg bad or 5mpg bad?

Thanks

Rotortuner

I will address your 1st question. someone else can add and answere the other questions.
1)Is it possible to get 200whp out of a moderate streetport?(I'm sure the answer is yes) OR would it be easier to go with a small bridgeport?

No its not really possible to get that much pwr out of moderate street port. The max HP that has been obtained from huge race street ports from what i have heard has been about 215 mabe 220. But these engine have everything and usually will run a large carb like a IDA or holley since they out flow the crappy stock EFI. That is FWHP also. So i think for you to get the pwr your looking for, your going to have to go with a bridge port. There are a lot of road racers in GT3 and other SCCA road racing that all use either a bridge port or pp. They are pretty competetive also and hold up to road racing conditions. Once again they all use 48 IDA carbs or larger. Hope this helps.

CJG

HWO

well set up bridge port or a Peripheral Port will yeild the best results

peejay

You can get maybe 260-275hp (flywheel, not wheel horsepower BS) from a highly tuned, high strung, short life streert port.

Do a search in the FC section, Dave Lemon posted some "interesting" things about the street ported FC engine for their E/Production car. It sounds like a grenade motor to me.

Gotta side with HWO if your rules allow for bridge/peripheral. Torque curve nearly flat and higher up than a side port engine so you don't need to use super high revs in order to make the power you need.

RETed

"Short life street port"? [sic] Overrevved?&nbsp What does it mean?


-Ted

peejay

You're saying that engine life is not related to the average RPM it sees?

RETed

No, I was just wondering if it was the street port that failed?


-Ted

Hamza734

My engine builder's (Bruce Turrentine) street ported N/A's dyno at around 220 at the flywheel. Assuming a 15% drivetrain loss, that gives around 190 at the wheels.


For simplicity and ease of install, a carburreator would be best. Most people run carbs on bridgeports. The Racing Beat Holley carb setup runs around 800 bucks.


A Bridgeport will get horrendous mileage at low RPM. It'll also have no little or no low and mid-range power. And it'll be loud, *very* loud. And it'll also have a lumpy idle... (see where I'm going with this?). For your application, a good street-port would be the best bet. I have an S5 turbo with a street-ported engine and it's reliable, has excellent power, and idles like a champ. For anything less then an a pure race car, a street port is best.

Ted, when's the website gonna be back?

Hamza734

You must have never driven a bridgeport The torque curve is most definetly NOT flat on a bridge or peripheral ported motor. Both BP & PP's have a huge amount of intake and exhaust overlap (~150 degrees for a BP). This gives excellent breathing capacity (which is why their so powerful) at the expense of low RPM efficiency (which is why they have no power at low RPM).

peejay

Hmm that must be why NSU's peripheral port engines made peak power at 5500, and that was more power than Mazda's 10As made at 7000 (or for that matter, their 12As made at 6000).

Hamza734

Your comparing apple & oranges. NSU's engines and Mazda's engines had different displacements, geometries etc. Mazda did an enormous amount of work on development on the rotary after they got the liscense to develop from Mr. Wankel.

Besides, the fact that the NSU P-Port peaked at 5500 proves nothing. What did it make at 4000? 3000? Most likely, very little. This is entirely due to the huge overlap inherent in Peripheral Port motors.

peejay

The NSU 2-rotor was the same displacement as a 10A.

Not all peripheral or even bridge port engines have to be enormous giganto-port engines...

Hamza734

Not all peripheral or even bridge port engines have to be enormous giganto-port engines... [/B][/QUOTE]

Then why go with a bridge or P-port? After all, a bridge-port is nothing more then a giant street port that has a little "bridge" for the corner and apex seals to ride in. Any time you port towards the periphery of the housing, you introduce additional overlap. Once you port as far as a bridgeport, there's a massive amount of overlap. That's why bridgeports and P-ports have no low-end and no efficiency.

mazdized

A bridge port with stock FI and piggy back stuff I would think is hard to do. A carbbed bridge would be good HP and reliable until the bridge crack or silicone won't hold the water any more, however having an exhaust system quiet enough for the street the HP will have to drop for a b- port motor. My set up was quiet and reliable with Holley carb. it peaked at 220 rwhp @ 9,300 rpm. I built a ported 87 six port motor with resonable used housings, full exhust, under pulley, and stock 87 injection it got 163 rwhp with 100 mi. on the motor. There are many ways to do NA but it is important to make sure your combo will work after all. I would stick to good old ported motor and a Holley or IDA, after all they have been around for more than 30 years. Oh the torque thing.... Nomatter what you do NA seems always have about the same touqe about 140-150 lb. but how flat and how long the curve is ianother thing. In my RX3 which is a very light car with most of the weight in front it would spin the tires any where between 5500-7000rpm in second gear with the gas pedal and it would fish tail in third with a fast shift on cold days. That is with 9 lb. fly wheel and 3.9 read end. Compared to a stock motor the torue is about the same but the curve is all moved up in the rpm range. under 4000rpm not a whole lot goes on with a bridge but when it hits 5700rpm it feels like a 60hp shot of nitrious that came on and at 8600 or so another 20 shot came on. With almost no elevation change I can easily see 20mpg with my bridge port while cruising @ 70 mph or so. Bridge may have lost some peak torque compare to a stock motor but it makes up so much with the extended curve it will still lay way more rubber than a street port or stock motor. Bottom line I have no drivability issues with the bridge port motors that I have ran on the street, but the lumppy idle and very difficult to drive in bumper to bumper traffic took the fun out of it for a daily driver.

mazdized

A bridge port with stock FI and piggy back stuff I would think is hard to do. A carbbed bridge would be good HP and reliable until the bridge crack or silicone won't hold the water any more, however having an exhaust system quiet enough for the street the HP will have to drop for a b- port motor. My set up was quiet and reliable with Holley carb. it peaked at 220 rwhp @ 9,300 rpm. I built a ported 87 six port motor with resonable used housings, full exhust, under pulley, and stock 87 injection it got 163 rwhp with 100 mi. on the motor. There are many ways to do NA but it is important to make sure your combo will work after all. I would stick to good old ported motor and a Holley or IDA, after all they have been around for more than 30 years. Oh the torque thing.... Nomatter what you do NA seems always have about the same touqe about 140-150 lb. but how flat and how long the curve is ianother thing. In my RX3 which is a very light car with most of the weight in front it would spin the tires any where between 5500-7000rpm in second gear with the gas pedal and it would fish tail in third with a fast shift on cold days. That is with 9 lb. fly wheel and 3.9 read end. Compared to a stock motor the torue is about the same but the curve is all moved up in the rpm range. under 4000rpm not a whole lot goes on with a bridge but when it hits 5700rpm it feels like a 60hp shot of nitrious that came on and at 8600 or so another 20 shot came on. With almost no elevation change I can easily see 20mpg with my bridge port while cruising @ 70 mph or so. Bridge may have lost some peak torque compare to a stock motor but it makes up so much with the extended curve it will still lay way more rubber than a street port or stock motor. Bottom line I have no drivability issues with the bridge port motors that I have ran on the street, but the lumppy idle and very difficult to drive in bumper to bumper traffic took the fun out of it for a daily driver.

Hamza734

Mazdized,

I'm looking at building a streetable 6-port bridgie with programmable EFI (Microtech). Care to share info about your quiet exhaust that still makes power? I was under the impression that a quiet exhaust would choke the s*** out of bridgeport. Send me a PM if you don't want anyone else to know

BLUE TII

iTrader: (9)

"Short life street port"? [sic] Overrevved? What does it mean?

It was a 6 port siamesed into a monster 4 port (aux ports and 2ndary port ground into one big port) for E-prod as that class only allow for mods to stock ports and no internal engine mods. Since it was making peak torque above 10,000rpm Dave was worried the stock, unmodified internals would cause reliability issues at those high rpms for extended periods.

Edit- E-prod allows for "limited" internal modifications. Dave says he did this,

VERY lightened rotors (STARTING with lightest ones)
side cut rotors
ceramic apex seals
hardened gears
competition rotor bearings
3-window rear bearing
93 style front bearing
oil shooters in the eccentric modified
oil passages "flowed"
oil pump massaged
3 lb flywheel (yes, three)
lightened counter weights
5 1/2" double disc clutch
MSD 7AL's
Mallory coils
VERY balanced assembly
competition thrust bearings
2 oil coolers
HUGE radiator
52 mm IDA carb
very short manifold
it liked a VERY long exhaust
smallest eccentric pulley
largest water pump pulley and alternator pulley
restrictor in water hose

+ other stuff?

BLUE TII

iTrader: (9)

For quieting bridgies down for street duty I have always heard that one should use many straight through mufflers of large diameter.

True duals w/ twin presilencers, twin straight through mufflers before the axle and then twin mufflers at the rear of the car.

This makes sense to me as I know the huge diffenence in noise levels between running a presilencer or not...

RETed

Okay, I've always had a problem with this statement, and people have always argued that *overlap* was the main point that increased this breathing - I disagree.

My argument?&nbsp Overlap is advantageous with a piston engine with crossflow heads.&nbsp If you understand the concept of overlap in a piston engine with crossflow heads, then you'd understand that the exhaust needs to flow opposite of the intake vector.&nbsp This is not true on a rotary engine, so it can't be that overlap helps engine breathing???&nbsp If the concept of overlap is applied to a rotary engine, the exiting exhaust gases create a vacuum and suck the intake charge into the engine but induce the intake charge to flow DOWNWARD toward the exhaust port, which is not the direction you want them to go with the spinning rotor.&nbsp What this implies is that the intake charge needs to change direction to start flowing in the proper direction for the whole combustion process to start working properly - so overlap is counterproductive to the engine combustion cycle.&nbsp I've always thought the huge (intake) port area created the power and not the overlap itself.

Looking forward to a lively discussion on this matter...


-Ted

Hamza734

Ted,

A very interesting argument... and I agree that a piston engine with cross-flow heads best takes advantage of intake exhaust overlap. However, I disagree with the main point.

Intake and exhaust overlap increases breathing capacity (READ: ultimate power) on every four sroke engine. The increased vaccum caused by the exhaust port remaining open longer causes more intake charge to be sucked in. Regardless of the port configuration, the pressure differential (the high pressure of the intake, the low pressure of the exhaust) causes more intake charge to enter during the intake stroke.

The downside is that an engine has to be turning at a certain RPM to take advantage of this effect. If the engine is too slow, the vaccum effect works too well- the intake charge gets sucked right out the exhaust! Once you reach a certain speed, the actual amount of time (not overlap) that both the exhaust and intake are open is too small for the intake charge to be pulled out the exhaust. At or above this speed, the engine can take advantage of its breathing capacity. Empirical evidence backs this up: BP's and PP's guzzle fuel at all RPM's yet only make power at high revs.

The most extreme example of this effect is a Peripheral Port. Here, the opening and closing of ports is determined by the apex seal, not the leading edge of the rotor, giving MASSIVE overlap. That's why these engines come alive over 5000RPM and can be revved to around 10K. The breathing capacity of these engines is so huge that they make great power even when matched with a small carb (Weber 48 IDA).

On a seperate note, when's the damn website coming back?

RETed

I still don't think it's the overlap that's causing all that extra power at the top end.&nbsp I still think the larger ports are more the reason.&nbsp Pumping dynamics in the intake/exhaust are largely negated at higher RPM's, right?&nbsp The intake charge and exhaust gases pulses start flowing so fast, that everything turns into a continuous motion of gases - does this make sense?&nbsp A similar situation is when we talk about sequential versus batch firing of fuel injectors at low versus high RPM's.

Yes, overlap is a factor, but I think it's not much of a factor as some people claim to be so.&nbsp I've heard strong arguments for overlap engines, but I haven't across an undisputable argument for it being the primary factor for big power engines.&nbsp The dynamics of getting the intake charge to get sucked into the engine induced by the exiting exhaust gas pulse and then not having to flow downward but across into the combustion chamber is pretty damn complex.&nbsp I would think we would need a supercomputer to compute all the variables for such an event!

We're working on establishing a new domain name (fc3spro.com, no hypen), and once that's done I'll have most of the info back up with 48 hours!&nbsp Be patient - it'll be revived soon!



-Ted

j9fd3s

iTrader: (3)

well a pp motor breathes better because the air doesnt have to turn going into the motor, that right there is a big advantage.

the nsu motors do have very similar geometry to a 10a, you can use modified mazda seals in them. they dont idle all that well though

mike

Rx7carl

Interesting. I heard he DNF'd at the runoffs, wonder if it was engine failure.

Hamza734

Pumping dynamics are in play at all engine speeds. As you correctly pointed out, the effects are reduced at higher RPM's. However, each rotor turns at 1/3 engine speed. Consequently, even at 9000 RPM's the rotor is only turning at 3K. At these speeds, pumping dynamics are still critical....

Computing the absolute dynamics of the intake charge vs the exhaust WOULD be damn near impossible. However, one can still quantitavely say overlap matters. Why? Because the driving force to suck in the intake charge is vacuum. The longer the exhaust stroke continues into the intake stroke, the greater the vacuum. Given ports of equal size, the one with the greater vacuum (the one with the most overlap) will suck in the most intake charge. It'll also be the most efficient, as pumping losses will be less.

In a sense the point is moot for rotaries. Since all but the mildest porting increases overlap it'll be impossible to consider whether overlap is responsible or port size. I would argue both, with port size being a bit more important.

Cheers,

Hakan

Hamza734

I would say that has more to do with the manner of driving then the porting. All highly tuned race engines are hand grenades by nature. Plus, I'd be willing to bet the house that a car with a 3lb flywheel will be overrevved more then a few times.