I looked at some 2g N/A dynos, then I look at the numbers people are talking about for the rx-8, and it gets my brain goin.... How do they make SO MUCH power from the N/A renesis?

 

1) Reworked side-port exhaust ports - keeps the combustion charge a lot longer "inside" the engine which increases torque and decrease emissions.

2) Higher redline - it's supposed to be set at 9kRPM, which is esily 1,000RPM higher than your NA.



-Ted

 

It comes stock with NOS

 

stock and NOS should never be in the same sentance

 

Doesnt it also use PP porting for the intake?

 

It has six port intake ports (like the normally aspirated 86-92 models), however the exhaust ports are also in the steel plate (same as the intake). It is called peripheral ported by definition, not the peripheral type porting we are used to, having both intake and exhaust in the rotor housings.

 

I agree. However, if every gas station everywere had a fill-up pump for NOS, I'd disagree, but since there is little chance of that, I'm going to stick with good'ol 87octane or alkahol fuel.

 

It has all "side ports" (as described above) but no "peripheral ports" (as incorrectly indicated above). All Mazda rotaries produced so far have had side intake ports and peripheral exhaust ports.

It makes more power because using all side ports gives much better control over port timing (a feature that was exploited to make more power), and it revs really high.

-Max

 

NOS = New Old Stock - musclecar restoration term - basically dealer stock that's been sitting on shelves unused for the past 30+ years - VERY expensive stuff but the only way to properly restore a car.

Oh, unless you mean a certain band of nitrous-oxide kit...

 

renesis engine has more compression.. 10.0 to 1, earlier N/A had 9.4 to 1 and 9.7 to 1. a totally different engine. from intake to exhaust. the auxilary ports are much larger then the earlier N/A engines too. hmm a nice renesis engine with a gangster street port on some 250 nitrous hp shot should make some decent power...

 

The Renesis engine makes more horsepower simply because it can maintain torque at such high rpms. A 91 N/A had 140 lb-ft at 4000 rpm and 160 hp at 7000 rpm. If that engine could maintain 140 lb-ft of torque up to 8500 rpm, then it would have nearly 230 horsepower (at 8500 rpm). As any street/bridge-porter will tell you.

 

Judge Ito is right, it's the extra compression that makes the difference in this case !

I hear that it is over 10:1?

The simple facts are that If you do a good street port with a tuned intake and exhaust it will make MORE power than the renisis engine, and this is with 9.7:1 rotors !

It may not pass emissions like the later engine but it WILL MAKE MORE POWER, You gotta remember when WE do a good street port the exhaust is over double the size of the stock port and the Intake is massive as well, add to this that you have the benifit of OVERLAP and It easily makes more power than the RENISIS with lower compression.

If the parts are not interchangable which I am told they are not, the first modifications I will be doing to this engine is to put in peripheral exhaust, cause any amount of gas recurculation as the RENISIS claims to do is BAD FOR ENGINE POWER.

Compression and tunned intake/exhaust for high rpm torque is how this engine makes it's power, nothing special about it...with a bit of work it would make a top n/a power plant.

 

just curious, I think I saw a picture somewhere and it looked like it had individual throttle bodies.

 

[QUOTE]Originally posted by RICE RACING
[B]Judge Ito is right, it's the extra compression that makes the difference in this case !

I hear that it is over 10:1?

The simple facts are that If you do a good street port with a tuned intake and exhaust it will make MORE power than the renisis engine, and this is with 9.7:1 rotors !

It may not pass emissions like the later engine but it WILL MAKE MORE POWER, You gotta remember when WE do a good street port the exhaust is over double the size of the stock port and the Intake is massive as well, add to this that you have the benifit of OVERLAP and It easily makes more power than the RENISIS with lower compression.

RiceRacing,

Can you please explain why port overlap increases power? I have heard this before but do not understand.

Thanks!

Anthony

 

From my understanding, on piston engines, overlap is when the intake and exhaust valves are both open. When the exhaust valves are open the exhaust flows out, so if the intake valve was open, then the velocity of the air going outward would help suck in air from the intake.

As for if it works on the rotory, I'm not sure.

 

Works exactly the same!

Except rotaries have an advantage - the intake and exhaust ports aren't right next to each other, they're at opposite ends of the chamber during the overlap period. The chamber almost by definition has to fill with intake air before it can start blowing out the exhaust.

Meanwhile on 99% of boingers, the intake valve is right next to the exhaust valve, so it's easier for the intake air to blow right out the exhaust (or vice-versa) bypassing the chamber altogether.

That 1% that do not apply are T-head engines, which are possibly the worst engine design possible

 

It is a "dynamic" charging system that needs both ports to be open to function, it is a complex interaction of waves that happen when the ports open for both intake and exhaust. The basic effects of both are that the pulses generated travel up and down the intake and exhaust manifold, also they transfer across both ports so that at certain tuned ranges the pulses action, or to more more correct the final reverberation or reflection of the pulse carries with it increased charge, to this it allows the existing wasted charge in the clearance volume to be expeled out the exhaust. This is the reason why with overlap VE% can be over 100% in the upper rpm ranges, it can even be over 100% in the lower ranges provided correct gas speed and runner lengths, I can show you many cases of this with Peripheral ports tunned for low speed VE and they do work.

This was done MANY years ago with the NSU RO80, I was lucky enough to drive one of these cars for my self and they did have alot more power in the mid range than the R100 10A ever did....They just are not as friendly with emissions, not to the extent of massive blow by or any of the other crap you read about from so called experts! It is just that BP's and PP's require a richer mixture to run at light loads and low revs, this is why they find it harder to pass emissions.

An engine with overlap and tunned induction and exhaust for specific engine mechanical limit (rpm limit) will ALWAYS make more power than the engine with near 0 overlap, add to this that the engine with overlap has a wider torque range as well, (Lots of turbo guys will tell you this) and if you just are after performance and not so interested in passing an emissions test then run as much overlap as you can fit, the ONLY time you will get caught out is with more overlap the engine is more sensitive to back pressure in the exhaust or pressure differential between the intake and exhaust in turbo applications.