Diving a 300HP Turbo'ed RX-8 (Australian)
 

Hi all,

A few weeks ago I was priveledged to drive the MazFix turbo'd RX-8 beloning to MazFix here in Brisbane, Australia.

I only got about 10 - 15 minutes of it, and I was not privy to check out the quality of the componentry used. (I believe a new engine mount had to be manufactured for this install, and I am not sure how well this was achieved - in terms of repeatability etc for a "production" component.)

The intercooler installation looked very neat, and even looks like the Hymee grille kit will still work to protect it from stone damage!

First impressions... Idles very smooth, like stock. Even sounded like stock, as it had the stock exhaust. (Not for long, a Hymee has been purchased to test for the "stage 2" upgrade ;) )

Clutch was very light, thanks to a MazFix mod and an upgraded pressure plate. Very easy to drive.

Driving along in the lower gears (1st and 2nd)... Since the revs rise quickly in these gears, it gets to 3,500 - 4,000 RPM quickly, and then the boost comes on strong. Turbo whistle is not too loud (about right IMHO), and there is no pop-off valve, just a sweetish sort of "overboost" fluttery whistle noise on the overrun.

1st gear goes pretty quick to redline. 2nd as well. Hard to test much past that legally on the streets. The extra punch from the boost was quite noticable, and the car was quite trackable. I'm sure Archie would not have invited me to drive it if it wasn't pretty close to 100%

I didn't try to peel the tyres of it, as it wasn't my car. The boost does drop off in the higher RPMs, down to about 5PSI I was told. I felt that I could feel this in the acelleration characteristics of the car. Don't get me wrong, it was fast. you could just sense things dropping off up top, but still more power than stock, no problem.

Lag. Definately. If you are driving along in a high gear at low RPM (i.e. 3200), you need to open the throttle and wait for the boost to build.

If you want to drive around at high RPM all the time, then there is no lag.

Comparison to a twin screw (I have lots of experience driving them in rotors ;) ) ...

The Twin-screw definatley gives instant boost, with no lag. This means you get torque on tap, and makes the car very much different to drive, as the throttle response is right there when you ask for it. I did not get that "grunt/torque" feeling from the turbo. But once she spooled up - sure, there was plenty of power. I feel I made the right choice with the screw for what I wanted to achieve. I just hope to get it on the engine dyno soon, and some more combo's tested.

I hope this is treated as an honest opinion. Sure, I have made a big investement in the development of my twin screw kit, but I trust no one can say that any of the above was biased.

Cheers,
Hymee.

Thanks for the review.

What kind of rpm would you need to be driving around with to avoid lag?

Are you aware if this is a one-off or is it being developed for sale as a kit? If so, are you aware of a ballpark price?

I appreciate I could ask these questions of MazFix direct but since you've been talking with them and others reading this may have similar questions, it might be just as easy for you to respond, if able.

Otherwise, is Archie interested in posting more info and photos here?

So from what i read Hymee is saying that the turbo kicks in at 3500- 4000rpm ?

Isnt that late ? would prefer a turbo to kick in much earlier at 1500- 2000 rpm :ylsuper:

Daniel

That's how I read it Dan and I agree with your sentiments. Perhaps not as low as 1,500 but I'd certainly like more torque from 2,000-2,500 up. This would greatly enhance the driveability of the car in day to day urban conditions.

Avoiding the drop off up high would also be nice but hey, you can't have everything :mdrmed: ...or can you? :suspect: Anyone?

Hymee,
How about the top end for the SC? All the way to redline? Torque curve still close flat?

3000-4500 isnt to bad when the rx8 redlines at 9k, just an quick update i will have new video footage and time slips from dave this week, so hopefully ill be able to post them befor weeks end, his kit comes on boost from 2500k all the way to redline.

mirkop, you are off topic....might be wise to post all info regarding that kit in a new thread.

Just a thought.....;)

Nice review Hymee! Its nice to hear a turbo opinion/experience from someone developing a supercharger.

So it has pretty bad lag (4krpm) and then lets up at high rpm (6-7+rpm) thats a pretty narrow power band.

^^-- yup

That's what I was getting at. Sounds like it would make a better track application (assuming reliability) than a street car (unless of course you're happy to live with that kind of torque curve).

Good review, Hymee

So it looks like potential buyers will have a real choice depending on the power curve characteristics they are seeking. That has to be a great thing, as different people have different needs.

BTW, I take it that the power below 3200 rpm is now worse than stock??

It all sounds a bit like the power characteristics of the 6 MPS.

I'd rather let people come to their own conclusions as to the "powerband" rather that say something that could be derogatory to Archies efforts.

I have tried to put my experiences into a pratical, objective manner, rather than make a sweping statement.

I'd like to say something else. NB - This is a general comment about turbos, not specifically about Arch's product.) A turbo doesn't only make boost with RPM. Sure, it is a function of RPM, but it is more a fucntion of exhauts flow/pressure. So imaging you are at 4000 RPM on a light or almost closed throttle. How much exhaust "energy" do you think there is? Some, but not lots. When you open the throttle, the engine will start doing some more work, and then the gas will start to flow, and the turbo will spool up, and then you get more power and more exhaust energy and more boost. If however, for example, you were sitting on an engine dyno, and the brake was holding the engine at 4000 RPM and you had it floored, then the turbo would be making as much boost as it can for that turbine speed. Let the foot of the break, and there won't be any lag, as the turbo has inertia and is already spinning as fast as it needs to for the exhaust flow , and just has to build as the flow builds.

No - I'm not tubro adverse. In fact we are probably testing some more with the falcon on saturday.

Cheers,
Hymee.

Thanks timbo. Appreciate your comment.

I didn't say it was worse below 3200. I don't really see any reason why it would be much different. It is not like a V8 (or any other piston) where we have dropped a different head/cam package into her, and safricied the bottom end for the top. I'd say there was no less power, in my experience, when there was no boost available. Hehehe - I like how I put that last bit. There is ALWAYS boost available in my screw!!!

Cheers,
Hymee.

:o: oops I mean "no worse than stock", not "now.." :o:

Hymee, do you know if Archie has any pre- and post-instal dyno slips he'd be prepared to share with us?

I think he has "public" figures, as I am pretty sure he ran it up at one of his public dyno days recently.

I'm sure if you give Brock a call he will be able to tell you.

Cheers,
Hymee.

I attach two dyno sheets for the Mazfix turbo, as run on a customer's car -- MLC -- who is a member of the .com.au site (for some reason, attachments aren't working there just now :( )

Just adding a pic of MLC's car, as thanks for the info he provided

Nice wheels! :Drooling_

Those figures look awesome. Well done Mazfix. It will be good to see this car in the flesh at the next RX8 meet.

skc

MLC, nice car.....and good on ya for putting the turbo in. Like Skc said, it would be good to see ya at the next cruise.

Cheers
rx88er

rx88er,

I forgot to mention I waved to you when I was driving Archies car! You were heading north from a set of lights on Logan Rd, and I was heading south...

Cheers,
Hymee.