Any rotrex mx5s lurking in here?

speed · Postby **speed** » Wed Sep 23, 2015 6:27 pm

Wow, thanks for sharing.
Is nothing like I was expecting. Guess I was expecting more of a whine, yet yours is much easier on the ears.
So so stealthy

mx5002 · Postby **mx5002** » Thu Sep 24, 2015 12:36 pm

That's the beauty of a centrifugal charger. Very little noise.

trader · Postby **trader** » Thu Sep 24, 2015 2:27 pm

Hi Speed
can't do a sound clip at the moment as in US. incidentally have only seen one NA (in Billings). just sounds like a stock NA although abit louder under load. I'm happy with power and safety using current ECU (don't go over 5000 around town anyway. You're right about legality - in Canberra you only do a roadworthy at purchase no annual checks but have to run the gauntlet of roadside checks. If you are pinged then you have a week to present car with engineers cert and emissions approval. So I have kept it looking standard as possible including stock exhaust.

speed · Postby **speed** » Thu Sep 24, 2015 6:52 pm

Thanks Trader,
My PD SC is way louder.
Will try and get a video this weekend as a comparison

These new laws suck. In the old days I could have done it all properly with a blue slip. Now we have to fork out another grand for engineering!

speed · Postby **speed** » Mon Sep 28, 2015 7:54 pm

Apologies for the bouncy video, will eventually get a go pro.

Really enjoying the improvement in performance though

https://vimeo.com/140636247

Jaxom_2 · Postby **Jaxom_2** » Sun Oct 18, 2015 1:16 pm

I had one of the DIY kits from Bullet on my NB8C, made 123rwkw with a 30-80 and a Kraftwerks style 32mm choke in the inlet, TDR style inter-cooler etc tracked, it and the air temp at the throttle body never went above 50degC.
I had trouble with the kit, wrong drive pulley supplied, no rear support bracket, first Rotrex lasted 12 months, the next from them lasted two months, still waiting for a call from them, over 2 1/2 now. Gave up in disgust after a month, the person I had been dealing with Greg Markham had left and the new person didn't read emails..
I then went the turbo route, factory IHI, happy with it but wanted more, so I'm now running a china charger 2560 on a Flying Miata manifold dump pipe and inter-cooler kit. Big smiles with 175.6rwkw, unfortunately getting rid of the extra heat is now a problem at the track.
So I am going to sell off the 2 turbo kits and get a Kraftwerks DIY with a 30-80 from Miata Roadster, I have Injector Dynamics 725cc injectors, Adaptronic ECU and an over the top of the radiator style inter-cooler set up I used with the first rotrex so I don't need all the extras.
I liked the way the car drove with the rotrex, I have a built motor now so I can play around with restrictors to get 200rwkw.

A bit long winded I guess, but if I had gone Kraftwerks in the first instance I would not have wasted so much money and it would still (probably) be reliable today.
The built motor is not included in the wastage, it's necessary.

jp928 · Postby **jp928** » Tue Feb 23, 2016 6:57 pm

Mate of mine with a 94 NA8 has a rotrex on it, as of ~4 yrs ago. 10psi boost, 138wkw. He must have been one of the early users, as they had lots of issues getting it all fitted and working - was NOT plug and play at all! Once going though, he has had zero issues over 10k kms now.

jp

3gress · Postby **3gress** » Tue Feb 23, 2016 9:56 pm

I recently received parts of the new trackdog kit. Although similar to the kraftweks kit the mount and brackets have been redesigned to limit flexing and belt alignment issues. Gary or William at Trackdog are awesome to deal with, parts are well made and came within a week of paying for them.
Have to pull my thumb out and get the car together.

mx5002 · Postby **mx5002** » Wed Feb 24, 2016 5:32 pm

I have been following their development of the new kits.. not sure if the kit for the nb8b is finished yet. Since i payed this ice bought/building a fresh hi comp n/a engine. However in time i think i could fit one to it with some e85 and lesser cams

3gress · Postby **3gress** » Thu Feb 25, 2016 1:31 am

Parts of the kits are available now for all of the covered models. William mentioned it was only sourcing new sets of injectors to match their powercard tunes in the plug and play complete kits that is delaying official release.
I have been further modifying my high comp na engine to install in the 89 mx5 when minor rust/resto work is completed on the shell. I don't quite know how i found myself on a forced induction tangent however the future is looking promising.

I've found a few rotrex/jenvey combinations helping duratech and zetec mills to produce decent power so the throttle bodies will stay. I'm chasing a nissan gtir intake plenum to modify for the jenveys, my excuse is i don't have an mx5 bp intake hanging around as the motor was powering my astina before i swapped to the mx5 platform.

speed · Postby **speed** » Fri Mar 11, 2016 8:27 am

These rotrex kits don't seem to make much power per dollar. Turbo seems to be the better way to go IMO ;)

hks_kansei · Postby **hks_kansei** » Fri Mar 11, 2016 9:05 am

I think the main bit with the Rotrex stuff is convenience over outright power.

My understanding is that many of the kits come ready to roll, including ECU stuff (or at least something to stop a rod coming out of the block)

If you're using your own management it would likely be simpler to tune than turbo as the boost is all linear and RPM related, rather than load related like a turbo.

In saying that, the only stuff i've tuned has been things with a single cylinder and a carb, which frankly takes a lot of the complexity out of the equation

3gress · Postby **3gress** » Sun Mar 13, 2016 5:15 am

hks_kansei wrote: the boost is all linear and RPM related, rather than load related like a turbo.

This is the general attraction for me. Other excuses being that I've built up a turbo block in the past, managed a self tune with itbs, it was a natural maniacal mechanical step to the other forced induction. The rotrex kit offerings have evolved enough now to have worked out the bugs and yet another kit is in the works from jackson racing with promising built engine awesomness. 300hp achievable on any rotrex platform when the pnp mindset is dismissed. There's a market for turnkey installs for sure, i'd reason a similar comprehensive turbo kit, new off the shelf with similar output would be comparitave in price to rotrex kitchen sink kits.
The mechanical relation between boost and rpm helps with tuning, better street manners too. Casual street cruising off boost is easy by managing rpm, with top end that is there when called on. Less heat issues, easy packaging, discreet. Not the most pragmatic or economically sound path but then...well you know.

jp928 · Postby **jp928** » Sun Mar 13, 2016 5:34 pm

The mate with the MA8 rotrex and I also have a jointly built/owned Lotus 7 copy with a 96 NA8 drivetrain with a turbo - went this way instead of rotrex because of lack of local support in Melb for the Rotrex set up. See http://www.almac.co.nz/index.htm. Its noticeable that the turbo engine boost comes in earlier (Avo GT2560, 8psi, 2.5" dump and exhaust, large FMIC), and is VERY linear all the way to ign cut at 7200rpm - Microtech ecu in piggy back mode. We put this down to very simple short exhaust (two right angle bends) and muffler.
The Rotrex delivers 10psi through a FMIC, and has a XEDE ecu in piggy back. I would expect the Rotrex net power to be down against a turbo of similar boost because the belt dríven blowers take power off the crank, where the turbos dont - you just have to let them breathe, minimize the exhaust back pressure.
No internal changes in either engine. Both were dyno'ed on Dyno Dynamics machines, but different ones.

The Rotrex showed 59rwkw @ 4000rpm @ 3.5psi; peaked at 139rwkw @ 7250 @ 10.4psi . peak torque 225Nm @ 6250.
Boost is linear from 0.4psi @ 1700rpm to 10.4 @7250.

The Turbo showed 93rwkw @ 4000rpm @ 6.2psi; peaked at 162rwkw @ 7200 @ 8psi. Peak Torque 239Nm @ 5300-6100.
Boost starts showing on chart at 5.4psi @ 3100rpm, gets to 8psi at 5400, and stays there to the end. This gives a very flat torque curve, after a steep climb to 203Nm at 3400, and 216Nm at 7000. While the figures may be on the high side for the turbo, the shape of the curves is unlikely to be wrong, and the flat torque curve is borne out by the flexibility on the road. Cruising we get under 9 L/100km.

jp

3gress · Postby **3gress** » Mon Mar 14, 2016 12:11 pm

Thanks for the info and comparison jp.
The theory of using a larger sized rotrex unit and implementing some form of boost control, by wastegate or such, has some compelling evidence across the webs. Emilio of 949 once commented on the possible use of a wastegate for deviate. At the least it makes for some engaging research.
Thoughts on concept?