Rotrex vs Turbo (AVO) for Track use (transient response, IATs, heat management, etc)
 

As the title says I would like hear about your experiences exclusively for track use, and supporting data of any sort would be highly appreciated. And yes, I searched but couldn't find anything other than the subjective opinion(s).

FYI, I plan to use OEM DIT oil cooler that comes with Forester(yes, I know) and Koyo radiator regardless of the FI application to help eliminate the heat issues (even before the FI route to be exact).

I have owned turbo cars in the past and even though I liked the rush/kick of the turbo for the street use, I was happier with NA cars when it comes to heat management, linear power delivery and reliability for longer spirited driving and track use.

Below are the information I gathered so far on both FI application:

Turbo advantages:

• Makes more power at the given boost level (more efficient)
• More low and midrange torque
• Less noise meaning less need for muffler/resonator on the exhaust
• Upgradeability, ability to unleash more power down the road
• Avo kit looks very appealing and simple and has the stock-like appearance ( but at the end it's a turbo)

Turbo disadvantages:

• A bit more complex project since it generates more heat which requires more heat insulation to prevent heat soak issues (wraps, turbo blankets, hi-temp coating ..etc)
• Possible lag and unpredictable power delivery (may not be the case for smaller turbo setups)
• Transient response is somewhat delayed even with smaller turbos
• More prone to back pressure so it possibly requires a larger exhaust setup

Rotrex advantages:

• More like a "turn-key solution" because of the simplicity and reliability
• Boost builds up as the engine speeds increases so less load on the low RPM levels to the engine (which ultimately affects the reliability), it makes the most power on top end so only when you need it.
• Less heat due to its design (some people claim that they can touch the intake after dyno pulls)
• Linear and predictable power delivery that feels like a higher displacement engine under the hood, better transient response
• KW claims the stock exhaust and header car made 270whp on dynojet which is more than adequate for me

Rotrex disadvantages:

• Lacking the advantages of the turbo ( see above) and
• Possible belt issues (I think it's addressed on the newer kits though)

I am not really worried about the dyno numbers since after owning Corvettes and bikes everything feels pretty slow anyways ;)

I wanted to switch to a lighter platform after owning high HP cars mainly because I felt the weight is the single most important thing when it comes to track use. That being said, I also think the car is lacking a little bit of power and if Subaru offered a ~250-270 whp BRZ from factory I would get that in a heart beat instead (even if the cost would be 6-7k higher than what it is now). Hopefully, one of the FI applications will address this and I will be able to get the power levels I plan and get rid of the notorious torque/rpm dip in the process :thumbsup:

:popcorn:

I'm also interested in comparing specifically the Rotrex system to a turbo, since it similar in some ways and I'll be doing track days with 20-30 minute stints. I'm not sure how long it'll stay on topic before it grenades into another generic TC vs SC thread. Good luck.

Hopefully it'll say on topic, I did my best to emphasize the track use :)

Please people lets keep this on topic. I'm also genuinely interested in a more direct comparison for track work.

I know @CSG Mike has driven both at the track, but not sure about anybody else.

I also don't think we can speak for the reliability of any of the systems at this point, most 86 have less than 30k miles and probably not nearly as much track miles. A big plus for the Rotrex IMO is the turn key solution - install, tune, and your ready to go. I haven't heard any install issues, like I've heard with pretty much every other kit on the market. That in itself is impressive.

Also to note, I've researched quite a bit and it seems a lot of track guys use Rotrex units and speak highly of the reliability. Seems like some pistons + minor engine work + c30-94 + miata seems a good recipe for relable 300whp. While the turbo track guys also like to say turbos are "just as reliable", every one I've seen speak up (online at least) has had at least some sort of problems at the track. More moving parts, heat, etc. is obviously going to present more challenges, but I would love to hear more direct experiences with turbo 86's at the track.

I was waiting for the KW kit when I had my NC3 Miata but it took forever for some reason (people say it's been more than 18 months when it was first announced) so basically I wanted to get a BRZ because it seems like there a lot more FI alternatives as well as the other aftermarket support and the back seat of course :) NA and NB Miata owners seem to be liking their KW for track use.

I believe I'm one of the more qualified individuals to answer this question. I have, however, NOT had any seat time on track with the Kraftwerks kit. They are not willing to allow me to drive their car for me to get impressions.

However, @Zach3794 has stepped up to the plate, and I'll be doing some logging in his car at the next Winmax 86 CUP event.

Give me a list of specific questions, and I'll answer them to the best of my ability. The more specific your question, the better I can answer.

For the record, CSG is a dealer for both rotrex kits, as well as the AVO turbo kit, among other FI options.

Thanks, it would be great if you can compare your results to the JR kit assuming you already took some data with JR powered car. (IATs Oil temps etc). Also have you ever had a chance to track a car with an Avo turbo kit?

Thanks again

I have.

Oil temps will universally be higher on a turbo car that has an oil cooled turbo. You'll need a cooler that can keep up. Under hood temps will be higher with the turbo car, even with a vented hood.

IAT will vary, but assuming a similar level of boost the Turbo car (with base AVO turbo) will have a higher IAT as well. With similar boost, the AVO car will have a small AUC advantage, but that AUC advantage is not sustainable. At heat-soak equilibrium conditions, the JR kit will make similar AUC.

With a turbo car you add power with a bigger turbo (diminished transient response), or more boost (higher IAT); your cats are probably deleted to begin with. With a SC car, you can add power with more boost (higher IAT), or increasing VE (deleting cats, same boost).

Do you have specific questions?

Thanks,
Since the car will be in the power band under curve area or the "umph" feel is not that important for me (to each his own).

Did the the rotrex car you drove at the track have the OEM header and exhaust? I wonder if the OEM catback will provide adequate flow since I'd much rather keep the OEM catback for sound and cost purposes and I am definitely not worried about 3-5 whp that I can gain with that. I will most likely change the OF/FP combo only.

Thanks again

I am a huge turbo fan. With that said my opinion for extended track use, I would recommend the supercharger. If for nothing more then the linear power band and consistent power production. You can make a turbo set up work well at the track, but I feel you will have a considerable amount spent on heat shielding, air ducting and such.

Yes the JR kit cars have both OEM cats, and have a 100% OEM exhaust system. If you get a custom tune with a non-catted header and non-catted front pipe, I'd expect to see a large HP increase. With E85/race gas, even more.

I really appreciate it. :cheers:
Do you recall what kind of power it was making with the full OEM exhaust? And your oil temps between sessions? IIRC, in one of your earlier posts you mentioned that the JR car you drove didn't have the oil cooler, do you have updated results or before and after results to see the effects of the oil cooler and /or radiator?

:)

I couldn't get the oil much past 230F or so on track with the oil cooler, and this is at a fairly quick pace.

We were at 245whp from a 172whp baseline with JUST the kit on and no oil cooler, and no other modifications. The 245whp wasn't a hero run. Rather, it was fully heat soaked, and what you'd see in a real world condition. The car does make more power with an oil cooler, since the tune will compensate for the lower oil temperatures.