Rotor Convert

Hey all,

Today I took the Alfa to get dynoed as Bruce has done so much work to it for the big trip to Philip Island. We wanted to get it all sorted seeing as we have made it into a bit of a monster!!

So the lil Alfa makes 88.8kw at the wheels.....which is interesting as my racing number is 888 now dats kinda spooky. At 90kph it makes 162nm of torque.....average power between 60-140kph is 70.7 kw. Don't know what it was before unfortunately.....but to me now it's way more powerful.

So went back to get the car and the guy that did the dyno begged me to put the 8 on there. You see they have put a modified renesis into an RX7 but didn't have a baseline for a stock Renesis to match it off. So I agreed.

My results are interesting:

Max------------------------------------------------------------Mazda Australia figures
Torque @ 88kph = 209NM-------------------------------------------211 NM
Powa @ 122kph 6,000 rpm = 112.9kw------------------------8,500 rpm = 177kw

The tacho is on the conservative side, car read 6,500 rpm when the box read 6,000 rpm. I am told that Mazda's are notorious for doing this..another engine saving device...

The guy who did the dyno wanted my results to overlay on the results of the RX7 renesis. Interestingly that engine had 144kw at the same rev range as my 112.9kw He said all I need is a different exhaust and that will make a huge difference. All the mechanics at this workshop commented on how quiet the car was.... compared to the brap brap brap from the RX7's and a lovely little RX2 my car seemed to be so homogenised...even on the dyno it was quite...the loudest thing were the rollers!!!

However all that aside they are going to email me the mapping of the modded engine to show me what's possible after my warranty expires..... even Bruce, who is not fond of rotors, started talking about changes....his eyes lit up and he seemed to go to a faraway place which was good as I was already there planning for the next incarnation of this car! I think he thinks if he follows my wavelength and agrees with me now that we are married I will let him drive the 8 more.... He is so not got a hope!

Oh yeah, also the dyno guy told me that the click when we start the car and stop it is something to do with the fuel pump I think, it's set for Japan so if the car gets frozen in the winter the snap/click noise is the fuel pump working....it's supposed to break the ice...apparently if you put your finger in there it would cut it off....I thanked him for that advice and then asked him to point out the fuel pump so I could make certain to avoid it.....not that I would touch it or be in a position to pull it apart ever....but it's helpful advice for those who might! (I think he said fuel pump but I could be wrong)!!

takahashi

What sort of intake and exhaust system is that RX-7 Renesis has?

It would be nice to know.

Since it is in a different car, the manifold can open to any angle and it may be the key.... I was reading Japanese mag last 2 months and waiting something happening over there.

144kW is certainly nice. 112.9kW is not bad for a stocka.

Rotor Convert

Thanks Taka. I will get some more info on the RX7. They are just starting to get people who want the Renesis in older cars.....

Would like more powa though.....LOL....but will have to make do with more noise for now.

Brettus

iTrader: (2)

don't get why they only took it to 6500 - do you have an auto RC ?
You should be in the 120s @ 8500 .
140kw is about all most of us can get with a few mods .

Rotor Convert

AUTO?????Noooooooooooo don't say that....no me got a manual........

I think that's just what they do...??? Not really sure why......

Anyway Bruce calculated that I would be in the right range of kw if they had taken it up to 8,500.....maybe it was the worried look on my face....was a lot of smoke but Bruce told me that was the tyres on the rollers.....it was my first dyno experience.....and I let someone else other than family drive the car.....I am so sad! I need to get a life!! LOL

Rotor Convert

Yes I agree Missy....dyno is not everything.

My car was really a sacrificial lamb as they didn't have a baseline to go from for the modified 7. So I got my car dynoed for free and they got their baseline...

Also got a hefty discount off the Alfa dyno as I asked for a better deal....it;s amazing what an assertive female can get away with these days!!

Brettus

iTrader: (2)

That has has been the case from the beginning of time

Was not being critical RC - just curious as to why they didn't give it full revs .
I understand how you would feel with your car on the dyno - somehow you get that feeling that something is about to explode as your engine gets closer to the redline.

Just checked mine at 6500 - pretty much identical to yours so the dyno guy is right on .

Revolver

Great illustration of why those who short change ain't getting the best out of this car. Thanks for the info Julia and glad to hear you survived your first dyno experience unscathed.

Methinks a catback is on your Chrissy wishlist...

Rotor Convert

No worries Brettus, my sarcastic british sense of humour comes out too much! I know you weren't having a go. Sorry.

There was so much smoke I was quite concerned....it was so noisy and I was worried the car might jump off the bloody machine...Bruce told me they would tie the car down but when they didn't I was a bit concerned.....it skipped around a bit on the rollers....

Glad to hear that my results correlate! That's made my day.

Interestingly when it came off the dyno all the warning lights were on!!!! Slippy and ABS!! I think he got a bit of a scare......poor Maxie! I am really sad I treat this car like my child.....

Thanks Brettus for your comments though.....

Rotor Convert

Thanks! Yes you should see my list on the .com.au site..seeing as Santa asked I have put in my list!

dbb

I disagree.

on my 2003 (old) rx8, I took the car up into the Adelaide Hills to a spot I know, and from a standing start at a give way sign, drove the car shifting on the beep to a speed limit sign a few hundred metres down the road. I did this a few times and worked out my average speed as I was passing the sign.

After I had the cat-back added, I was hitting that sign at about 8kph faster.

Also, when I have been driving with other stock rx8s through the hills, I used to consistently pull away from them out of corners.

It might not be much of an improvement , but it is there.

The dyno graphs on Hymee's exhaust (not the one I installed, btw), also show a measureable improvement.

dbb

From reading other threads, not all exhausts provide improvement ... the OEM model is pretty good.

My butt-dyno and observations indicate an improvement with the one I had. Others have seen the same. Others still have seen no improvement or even retrograde performance.

rexi

Sorry dbb, but a cat back exhaust on an Rx8 will give you a max of 3-4 hp at the wheels.Definitely will not be felt and would not pull away from stock Rx8s. The stock cat back exhaust is already very good.
However, start adding a high flow 200 cell 3" cat along with the cat back and then you may notice a performance improvement as the stock cat is quite restrictive.

Regards
Rexi

Revolver

Whoops, didn't mean to start something.

My reference to a catback was not for more power but for more sound (given Julia's comments about how quiet her Maxie was ).

FWIW, I agree there's only marginal gains to be made with catbacks but the feelgood factor is worth it IMHO. The improvement in exhaust note makes the whole acceleration process a richer experience, whether you're going quicker than stock or not.

Grizzly8

Not only do you get better note and a few extra kw with a cat back but it allows cooler running freeing up saving weight and reducing heat output , especially noticeable when your ride is locked in the garage .

Also if you get the REVI air ram intake together with the DIY air ram duct WITH AN AFTERMARKET METAL CAT

Michael

auzoom

Julia, I dont mean to slag off these guys as I have never met them and I canonly take your comments as I read them but:

1. The Brap Sound.
The pre renesis rotaries had a peripheral exhaust port which the exhaust port would overlap with the area of the rotor housing where combustion was happening, so you get exhaust gasses entering the intake cycle.
The renesis is side ported so you cant get that overlap, hence a renesis cant brap. I would be interested how they got their car to do it.

2. Not Tieing down.
Any shop that doesn't tie a vehicle down when they dyno is risking the safety of their employees as well as your car and I would NEVER go back there. Also, if you dont tie a vehicle down it is most likely going to rock (as you mentioned it did) and as such you will get bad readings. Teh fact you were getting smoke from your tyres is to me SCAREY!

3. RPM difference
If the car was rocking then I would dare say that you have found one culprit, but the RPM on the dyno is based on the RPM of the rollers on the dyno and the rolling radius of the OEM tyres. Worn or non oem tyres will affect that.

4. Catback
All you are doing is opening up the very last point of the exhaust. It sounds great and honest tests have shown a few Kw gains but thats it. A few people feel the throttle is a bit more responsive but thats also subjective. Also as Rexi said, the Cat is your next point of restrictions, after that it should be the headers. But if you go that far you really need to retune the ecu and good luck with that.

I will step down from the soap box now

Andrew

auzoom

lol, he is loud and proud! I wanted to know what a non-metal cat would be?

Grizzly8

GEEz YOUR MY.................... HERO .............. kall your all class

Michael