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.

Did you get another dyno run after adding the oil cooler or it was a different car? I wonder how it does with OEM exhaust without the heat soak issues

Directly related to the setup being discussed do you have thoughts and/or data on the Forestor DIT oil cooler (Cusco style essentially) vs. Other air cooled like Perrin or JR?

I am NA now and am looking to address cooling this year with a Koyo rad and forestor oil cooler I have an AT also that gets cooled via the rad as well. May or may not end up with a seperate tranny cooler as there isnt much data yet. I may go SC in a few years and would like to not buy something twice.

Sent from my LT30at using Tapatalk

Hard data? No. Anecdotal evidence? Yes. Thoughts? Yes.

Quite simply, the Forester oil cooler will not be enough. It's one of the first items swapped out for an oil-air cooler on WRX/STIs that are driven hard.

Thoughts on the Robispec oil-water cooler / radiator combo?

i really want this radiator but i've heard some bad things about her.

Like she is too big? What else?

Like if you make a date with her to do a little under the hood work she doesn't show up for sometimes months...

It works?

We went a different route with our car, but the main thing is to keep the car cool. Nobody knows the limit of the Robispec cooler because it's never been pushed hard enough. :shrug:

I was lucky and recieved mine very FAST, but have heard and read a few horror stories of 5+ months after paid full....

how do you like it?

this is what i'm considering going with

The fitment was TIGHT, needed to hack a little here and there, but the end result is just incredible.

There is nothing I can throw at it to make it get hot... Back to back to back pulls, back to back to back 1/4 runs, I haven't tracked it in a road course, yes, but I've done about everything but... 5 back to back to back dyno pulls, 35 in 3 hours, nothing gets it uncomfortable.

Robi never pushed it?!

He never made enough power to really push it. He also ran E85, which has some insane cooling properties...

Interested to hear more from folks who've tracked these cars with FI.

What kit setups, what supporting mods (particularly cooling), what power levels?

So far the CSG Rotrex car seems to be good on track running the base tune. Any turbo kits proven to be reliable as well?

The AVO kit looks solid for a good price but i'd like to see some real world examples. The Ptuning kit looks interesting as well due to the low mount turbo set up. Imperious Rex's Greddy turbo car seems to run well too.

Any verdict between front/top mounted turbos versus low mounted ones?

I'd really like a 'set it and forget it' type solution...something that's reasonably easy to set up and won't blow up in my face assuming routine maintenance.

Wasn't I there when we were trying to fit the damn thing and the fitment was over an inch off? We had to pull the radiator hoses really hard to slip it on lol.

From what I have casually observed on these boards as far as turbo's go...

@ImperiousRex regularly tracks his greddy kit. I would ask him questions about his experience. I also think @CSG Mike has had lots of seat time in this car.

The avo kit is being tracked hard on the AVO car in Japan and also a shop car in the UK (the name evades me).

No one has been pushing the ptuning kit on track, to my knowledge (which may change since I am installing one on my car). The only track footage released by ptuning is AutoX.

Element tuning is tracking a FA20club kit hard on track (or was, until an unrelated engine fire stopped them).

Team VCMC is tracking the full blown turbo kit still as far as I know.

My Greddy kit has seen nearly 15 track events since installation at the end of last Sept (including several podiums at GTA/SLB and RTA). The kit is pretty reliable and so far I haven't had any engine issues (except for DI seal failure shortly after the install but there were several signs pointing to their imminent failure before the turbo even went on).

The main issue with the kit is managing heat soak since the turbo is front mounted and the engine intake piping is surrounded by the turbo and the exhaust manifold. @CSG Mike had been complaining that on track my car felt like it was like stock S2k power and there was no way it was making the numbers that were achieved on the Evasive dyno and I personally felt like the car was making quite a bit of power on the street. So we had the car tested at multiple dynos to verify and we had some interesting results. I'll post on my member journal regarding the numbers soon. But let's just say neither of us was wrong...

Regarding the Robispec cooler though, it's been up to the task for the most part. The coolant temps typically level out at about 190 (since it is water cooling the oil) and oil temps on the street range from about 180-205 depending on whether or not I'm running WOT. On track oil temps reach 220-230 and coolant temps get up to about 210-215 but they stay pretty stable at those levels. I did have a fan fuse blow out though and had to replace the stock radiator fans when they melted from not running and being in close proximity to the turbo manifold. So I used the opportunity to upgrade to Spal fans with a @Carolina Dyno shroud. After fixing the fuse and upgrading the fans, the car has been pretty stable.

My biggest lesson with tracking the car with FI though is that you need to be religious with the routine checks and maintenance. There are many things that can build up over time and a failure at any one point could chain reaction into other issues.

That was V. 1, which I ended up returning.

I kept V. 2.

Thanks for mentioning it as I had completely forgotten.

I have a vivid memory of myself following a stock BRZ down the main straight at Laguna Seca and we were both accelerating at the same rate through the gears and I couldn't get any closer. At the time I had a non-intercooled innovate kit and it was lap 5 or so.

wow, that bad huh?

On the flip side, my brother and I have always been within 1/10th of a second of each other. @ImperiousRex has been there with the two of us....we're nearly identical. Since installing the Innovate (intercooled), I am aprox 5-10mph faster at the end of straights now than he is (even towards the end of a 20min session).

There may be heat soak still, but I'm definitely faster on the straights now. It's not a huge difference, and it doesn't seem like I pull that much harder, but it's definitely more than it was before.

Intercooler!

Even that will heat soak...

i think it would be good to qualify some of the above statements to more accurately reflect the differences between Rotrex vs Turbo


Turbo advantages:
- Makes more power at the given boost level (more efficient)
** actually this is not true...because the rotrex's high rpm capabilities, it can run compressors with the same efficiencies as turbos. however, at the same boost levels and same piping and intercooler configurations the rotrex should make more power because the charge air temps should be lower. the Rotrex has a maximum operating oil temp of 180F, so compared to the exhaust side of the turbocharger there should be less heat bleeding over to the compressor side. with the rotrex there will be a few hp used to turn the blower, so the question is if the power lost in turning the blower greater or less than the power gained from having cooler charge temps.

-More low and midrange torque
** this depends on the size of the compressor housing. the power on a smaller turbocharger may come much more dramatically at lower rpms, but may also run out of air on the top. but generally speaking the power of a supercharger will come in much more linearly than a supercharger.


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)
** yeah...turbos run hot hot hot...protecting and managing against the additional heat is paramount
- Possible lag and unpredictable power delivery (may not be the case for smaller turbo setups)
-Transient response is somewhat delayed even with smaller turbos
** yes..the sc responds instantly

Rotrex disadvantages:

- Lacking the advantages of the turbo ( see above)
- Possible belt issues (I think it's addressed on the newer kits though)
** this is more a possible kit developer related issue and not inherent to the Rotrex itself. on the KW kit, the sc belt drive is independent from the engine accesory belt, so even in the case of breakage, you can still drive the vehicle.

The UK car is that belonging to Fensport Performance:

http://www.fensport.co.uk/FensportCars/GT86_Race.aspx

Thanks for the explanations. I guess I am leaning towards to KW kit but can you please tell me whether or not I can use the SUBARU oem oil cooler with a smaller nut (the one behind the idler pulley)? The bracket size is my only concern with your kit, other than that it looks very good. I know you guys will soon offer an oil cooler kit as well but I would like to use the OEM cooler for OEMish look, simplicity and cost.