Half Bridge Questions

[PGiljevic]

Peripheral Ports are actually the WORST you can choose, they are the narrowest in power range and most effected by exhaust recirculation, are the loudest, and most effective at converting fuel energy into MOSTLY NOISE and HEAT .................... and a very small portion into power :Hammer

[Laeeq]

interesting...very interesting reading all this.  I always thought the street ported motor (if tuned and ported right) was more then enough for a good 450bhp on a road going car.  :yes

some good info provided by Rice here. Thanks:Thumbsup!

[Grant Monkhouse]

Peripheral Ports are actually the WORST you can choose, they are the narrowest in power range and most effected by exhaust recirculation, are the loudest, and most effective at converting fuel energy into MOSTLY NOISE and HEAT .................... and a very small portion into power :Hammer

Yes I agree but come on, the noise, the eargasm of noise!!!

Most people don\'t go to watch drag racing because the cars are fast, it\'s the v8 noise. I have seen an electric drag car run around the 8 second mark. Really fast and impressive engineering skills but it sounded like dog mess!

If racing went to electric no one would watch it u less they played car sounds over the tannoy!

Personally I can\'t call myself a rotary enthusiast until I have owned a PP turbo motor and a 20B!

[PGiljevic]

And BS to your statement haha :Thumbs-up, on my dyno plots from street to half bridge, I picked an extra 500 rpm of powerband going to half bridge, but as I know you hate dynos, I also picked up an extra 5 mph on my terminal speed on the quarter. But also you like rolling times as well, 60mph to 120mph in 6.5 seconds from 7.5

yes correct on bridge porting eating more fuel and being louder and not for everyone for the street. No one is disputing that point, but on the power point, bigger better shape ports let more air in, more air more fuel equals more power

A street port looses allot of mid range power over a stock port, so a bridge may help you out there :Thumbsup!

Make no mistake what I am talking about here is that ANY level of porting is inferior in a street application when using an exhaust system. And I can show you many a race car that makes the same power on stock ports as it will on all variants of "race porting" but with none of the negatives (and this is with OPEN PIPE exiting out back of the front wheel!).

Its a big fallacy that porting helps, it in many many cases does nothing except make the engine far more intolerant to various settings like exhaust, turbine, and ign timing. And it totally ruins any legitimate street car claims, which is not some peoples concern but its worth stating as a fact.

As I said I\'ll happily put up one of my stock std 13B-REW\'s against any car pound for pound in boost and weight and equipped with a Mazda gearbox hand out a lesson in why porting is a mistake on these engines. :Thumbsup!

[PGiljevic]

Yes I agree but come on, the noise, the eargasm of noise!!!

Most people don\'t go to watch drag racing because the cars are fast, it\'s the v8 noise. I have seen an electric drag car run around the 8 second mark. Really fast and impressive engineering skills but it sounded like dog mess!

If racing went to electric no one would watch it u less they played car sounds over the tannoy!

Personally I can\'t call myself a rotary enthusiast until I have owned a PP turbo motor and a 20B!

Don\'t get me wrong I probably love the noise more than anyone here :WaveBye

Just saying from lots of testing and my many gray hairs and hundreds of thousands of dollars spent you can do lots with what to others is not very much special :Thumbsup! and for the street is actually much more suitable :burnout

[Grant Monkhouse]

Boost schmoost?? A strange statement coming from you rice that is now testing at the 1.7 bar level? Hehe.

Hope you don\'t think I\'m questioning your knowledge as I am not, just asking the questions that everyone wants to.

Surely on a BP where the power is produced higher up will producemore HP then a standard port at the same rpms? Let\'s say 9,500 rpm? Would the standard port be able to keep the power at that level?

If I was racing or even street driving where my revs never went below 5,500 rpm would a bridged motor not be better? As you say the standard port is producing more power at point x. But what if my power band needs to be above that and to 10,000 rpm?

Impiety certain PAC performance aren\'t using standard ports??

[BlitzBoy]

As I said I\'ll happily put up one of my stock std 13B-REW\'s against any car pound for pound in boost and weight and equipped with a Mazda gearbox hand out a lesson in why porting is a mistake on these engines. :Thumbsup!

shame u dont live here, quite happy to take you on a track challenge :Giggle

[PGiljevic]

I take absolutely no offense to anyone doubting what I am saying or expressing a view point or their own experience, its a free world and we all love our rotaries.

I am just sharing what I have found over the years running all types of engines personally and through my many end users across the world and locally in all fields of rotary engine endeavor.

You gotta look at the whole package to see what is fast and what is slow in the real world.

If any of you blokes are on Torrent? (sounds like I know about the internets LOL)!!! then down load HOT VERSION vol 107 and take a look at the cars tested in that video to see what I mean about the effect of packages.

[PGiljevic]

I too used to be caught up in the porting mania :Hammer

Once you learn to harness the real function of a turbocharger you quickly then realize how totally irrelevant porting is and ironically you can use the superior charge filling at low speed and mid range speeds of the stock std ports to make an engine power curve that some 20B runners would be envious of :god ............... then your talking about levels of power that really cant be used anymore in a road going RX7 as well, so the never ending mind f7ck of what porting type to use is even more or a redundant concept.

IF however you are stuck at an arbitrary limit and care not for NOISE level or running any type of normal road going car then porting done well can yield some nice top end gains, at the expense of low speed and mid range power (not a problem for a race car with dog box and 6 speeds).

[PGiljevic]

shame u dont live here, quite happy to take you on a track challenge :Giggle

That\'s a pretty good time for 60mph to 120mph of 6.5 seconds.

I check my old air port strip run and it was 7.09 seconds as a comparison. I since am running more power and will be going back out to test it again.

[PGiljevic]

If I was racing or even street driving where my revs never went below 5,500 rpm would a bridged motor not be better? As you say the standard port is producing more power at point x. But what if my power band needs to be above that and to 10,000 rpm?

If you want an engine to run to 10,000rpm stock ports will struggle to achieve that. Using a very large turbine though they can work to almost 9000rpm *believe it or not*.

I run stock standard ports to 8500rpm. And through sophisticated and advanced computer analysis you need to rev them this high (once a power band is recorded) to make most use of the std gearbox ratios to derive maximum average acceleration pulling form 1st to top of 4th gear (140mph). Now if you go use a "street port" you need to rev even higher, but then you still fall down too far on a gear change into the lack of power zone through the modified port timing, so even though the boost is equal you are making less power. The same effect happens on a bridge and its even more exagerated on a PP. You also have the odd side effect in cars with short gearing and say a 6 speed (or even 5 speed) that you are changing gears too often and thus are loosing net drive effect (always an issue in single clutch applications (non DSG twin input shaft boxes which are only found in modern cars)........ so its real easy to go slower rather than faster despite having a dyno sheet that says you should be Don Mega :King

[re japi]

This topic has amazing info. But im a bit curious... How about N/A engines, which is better for rallycross race car, PP or big bridge port? Cause mid range torque is guite important. Your opinions...?

Thanks.

[PGiljevic]

This topic has amazing info. But im a bit curious... How about N/A engines, which is better for rallycross race car, PP or big bridge port? Cause mid range torque is guite important. Your opinions...?

Thanks.

If you are not noise limited then a Peripheral Port is best, to make it work in your application you need to run the right tuned length exhaust and intake manifold set up (length) if running carburetor it needs to have correct sized venturi (40mm) in a 48IDA works really well. or if fuel injected similar principles apply. You need the right air speed to keep the fuel well mixed with the air that the engine is injesting or otherwise it will only work over a narrow range when the air speed is sufficient :yes

A bridge is much easier to get to work as is a combination port (side bridge with peripheral of small nature.)

All of this advise goes out the window if you are running a restrictive exhaust system, all of the porting principles suffer badly, best to worst in this order.

Stock port
Street port
Secondary bridge
Full bridge
Semi Peripheral (combination port)
Full "J" Bridge
Peripheral Port

It is very easy to have a stock or very mildly enhanced stock port totally dominate ANY of the more extreme porting types when running a restrictive exhaust (read ANY exhaust that is legal be it street or drive by race track noise test!) this is doubly as bad when talking Natural Engines V Turbo charged.

Back in the day when we street raced every weekend and night the best combo\'s were of the milder principles (small secondary bridges) still with ear splitting exhaust ! but someone could still beat you with a good street port :burnout I can share many a story on this :WaveBye

If you have absolutely no exhaust restrictions or noise limits to abide by like at the LEMANS 24Hr or a F1 Grand Prix (or a Drug/Drag track) then Peripheral works, Most drive by noise limits imposed at circuit track day events consign Peripheral to the shelf and milder bridge can be made to work better at the higher exhaust pressure levels these types of exhaust impose on the engine. The amount of power loss is directly proportional to the exhaust manifold pressure and PP and its variants suffer absoluetely the worst in this instance and stock ports suffer the least. Type of port you pick in this day and age of homosexuals and green peace dictates what porting style you can exploit to most advantage.

If you want some more information on Peripheral I can show you a type I developed to work in a stadium truck (off road racing indoors!) run in N/A form with effective power band between 5k and 8k rpm.

[Grant Monkhouse]

Could port timing be increased on a stock port engine by chamfering/scalloping the sides of the rotor? To give earlier inlet opening and closing allowing more air in on stock ports?

[Grant Monkhouse]

In turn allowing for more air to be forced in? Gaining more power over all of the range?