mitchfried

Anyone have the dyno results for the hp and torque increase for a resonated hi-flo cat ONLY, such as the srmotorsports? Most of the dyno results I've seen include other mods such as intakes and pulleys at the same time.

titaniumgrey

Probably less that a catback exhaust ... thats my guess

Jaguar_MBA

Racing Beat reports the following:

3. Mufflers – muffler & connecting pipe - 2-3 HP.
4. Removing the muffler from the car (engine) – about 4 HP.
5. Remove catalytic converter and resonator from the engine completely, and replacing with "cat" replacement tube – max benefit 8 HP – regardless of what muffler is used (or even no muffler).

"The muffler "off" will yield about 4 HP, with a very loud exhaust note. With it "off" the car, the noise is unbelievable! We find 2-3 HP peak RPM maximum improvement from our exhaust, or any competitive system that we have tested. So someone can see from these numbers, it is quite difficult to get a lot more HP from this engine. The max potential with a header and race exhaust would be around 10HP."

From this web page ~3/10 of the way down:
http://www.racingbeat.com/FRmazda4.htm

My guess is that a high flow cat will maybe give you 4 HP......

mitchfried

How about torque???

futureownr4sure

well, it doesn't matter at all...

Fanman

That is incorrect. It will yield more hp. A few people using the Canzoomer unit were getting about 5 WHP using the CZ unit. The cat backs are giving us about 3 hp.

NRVOUS

Hi Guys,

I had my car dynoed today with a Hi-Flow cat set up or as you guys in the US call it a Midpipe with complete new High-flow cat. Last week the Car oringinally recorded 123.5KW at the rear wheels, today with the midsection replaced with a new high-low cat on the same dyno we recorded 127.7KW
please note this is with the standard exhaust system and our Aussie RX8's (177KW) are down on power compared to the US(184KW) due to our poor grade of fuel.
I will dyno the car again once I have my 7kg titanium amuse cat back system on, thats if AMUSE ever decides to sell it to me!

So there you have it 4-5KW gain just from a high-flow cat upgrade which cost no more the $250AU!

RXE16T

123.5kw stock last week and now 127.7kw with hi flow cat this week.
Somewhat doubtful of this gain from just a cat replacement.

The only true way to measure is consecutive runs or close to consecutive runs to lessen the chance of other factors playing a role (eg. ambient temperature, engine temperature, dyno setup, etc).

NRVOUS

nojooc,
Doubt all you want dood, but dont forget 4-5KW will not give you a kick in the pants however the dyno graph clearly showed a gain none the less and yes consecutive Power runs where performed and the ambient temps where similar for both days. Remember ROTARIES hate back pressure, so any increase in exhaust flow will improve breathing!
I will try an scan the dyno graph so you can see where there is notable change, slight as it is there is still an improvement which is similar to your catback exhaust system. Have you seen the size of the cats on these RX8, they are bloody restricitve!

RXE16T

Have a read of Jaguar_MBA's post 6 spots up.
He's directly quoting Racing Beat's Jim Mederer.

If a large professionally operation like RB have only managed a 8hp (6kw) gain with no cats, resonator and muffler through their testing, I wouldn't be the only one doubtful of a 4kw gain.

I'm not saying you lost power or didn't gain any power, I'm just stating that a 4-5kw gain may be a little optimistic considering how highly tuned the Renesis is.

But that's not going to stop me or the thousands of other 8 owners replacing their cat anyway (yes, I've seen how restrictive it is).

I'm not hating, so don't take it as such, I'm voicing my opinion.

NRVOUS

Nojooc,

No offense taken ,I dont get excited over figures, however if a comparable improvement can be documented with only a a complete high-flo midpipe replacement this is a low cost improvement. We are talking splittling hairs when it comes to a few KW's in gain. However cat back exhausts offer a similar gain with the esthetics and sound to please ones soul!
I've heard the racing beat exhaust on Z88M car and it sounds great,and your absolutely right in saying the RENESIS is a highly tuned beast.

Here is the Dyno Graph, this is one of the most respected dyno's in sydney which generally shows a lower figure to others, although the tuner is well respected for his abilities in tuning aftermarket managment systems like Autronic, MOTEC.... etc.

Fanman

Not hating nojooc, but 4-5 (not kw) hp from a hi-flow cat is pretty acceptable. If they are getting about 8 hp from a midpipe & exhaust, I would say a good 5-6 hp of that is through the removal of the cat. You have to understand that the way an exhaust (or any aftermarket part) works is that the increases are not cumulative. If an aftermarket exhaust usually gives 3 hp, and a midpipe gives 6-7 hp that does not mean that together they will give 9-10 hp....instead you are getting the 8 hp that Racing Beat got It may very well be that because backpressure is already reduced from the hi-flow cat that you are only getting about 2 hp from the cat back unit. The cat back unit is said to be about 3 hp, so that would be about 5 (or 6 hp) from a midpipe, a good hi-flow cat unit flows almost as well as a midpipe so 4-5 hp does not seem out of the ordinary. NRVOUS' claims of 5-6 hp seem totally legit (especially with a dyno slip). The RX8 is very highly tuned. A 5-6 hp gain is not a big amount for a car. I have seen some cars put out 10-15 hp (NA) or more (turboed/SC'ed cars) with the removal
of the cat.

NRVOUS

Fanman, the reason i did this is that this particular tuner is investigsting real time ecu mapping & tuning so they needed a base curve for a standard RX8, since I am racing in the East Coast Targa www.eastcoasttarga.com.au I am considereing the mild gains from exaust mods and of course to unleash that awsome scream of the RENESIS at full throttle.
I will document further changes, when the cat-back system goes on, as I have some fellow RX8 owners with more aggressive mods with piggy back ecu's..etc. who are dissappointed with their cost vs gains compared to a stock RX8.

rotarenvy

nrvous, what type of cat was it? I was considering a cat replacment but there are some claimed highflow units that realy are worse than std.

RXE16T

......and then?


My doubt in such a gain was a result of NRVOUS's first post where he stated : "Last week the Car oringinally recorded 123.5KW at the rear wheels, today with the midsection replaced with a new high-low cat on the same dyno we recorded 127.7KW"

I was doubting the accuracy of the gain since there are a miriad of factors that could have changed over that week that possibly may have affected it.

No love lost for me, just wanted to highlight the deficiency in the testing procedure, that's all.

NRVOUS

This particular cat has stainless mesh surrounding the honeycomb, if any SYDNEY siders are interested in the upgrade contact Mike at Tuffy Toned Mufflers Waterloo.
The sound is definitely louder at full throttle!


No love lost for me, just wanted to highlight the deficiency in the testing procedure, that's all. Nojooc initial run with standard cat was done at 4.30PM and Hi-flo cat was a few days after at 4.10PM with similar ambient temps and conditions. I understand where your coming from regarding same day testing, I guess we'll leave that to the experts like racing beat.
Forget I even mentioned a 4kw gain, just have a look at the dyno sheet. I believe that a certain workshop was quoting an 18KW gain from their exhaust system on a particular dyno, now thats what you call highlighting deficiency!

foxman

Keep us posted on your progress it sounds very interesting. Based on what I have read, the hp gains, sound and performance of the car is enhanced by the high flow cat and for the money, it is the first true performance enhancement I am doing.