BookEditar

i was wondering what sort of turbo setups most autocrossers in SM2 run. id want a setup that would accomplish 3 things: very little lag (this would be with a street ported motor and open exhaust), decent top end power, but i would only be running up to around 18 psi, and help with reliability of the overall engine (more free flowing, less heat generated). what setup would be ideal? im thinking ball bearing... but also, what setup would accomplish these things on a relatively low budget?

actionhank

I dont auto cross, but I would think that the BNR stage 2 or 3s would fit that bill nicely. Anyone else agree or disagree?

the_glass_man

iTrader: (2)

That limits your options to a few turbos.
The stock Hitachi's are good for 340-380 rwhp with great spoolup.
The 99 spec turbos spool up even quicker and can provide a little more power throughout the entire RPM range. They can be found for $1,500-$2,500
350-380 rwhp
You can also look into M2 dual ball bearing upgraded twins. Quick spool up, power numbers aren't really solid at this point.
Cost $3,200
BNR upgraded stock twins.
Spool unkown, cost $1,000-$2,200
340-420 rwhp
Single wise, you would have to make a compromise with power for spool up/boost threashold.
Look into an XS T04E kit has quick spool up and is cost effective. Fairly complete kit as well for around $2,600-$2,900
370-410 rwhp
A GT35/40 (GT35R) kit.
A dual bb with quick spool up and good top end power.
Kits range from $2,800-$4,000
400-450 rwhp
A'PEXi RX6 kit.
A BB designed turbo from IHI, but not water cooled. Turbo can't be rebuilt in the states and wastegate has been prone to failure.
Newer kits retain airpump if wanted/needed.
$3,000-$3,500
340-390 rwhp

Numbers are just estimates, and you will need all the other mods, etc...
Oh, and welcome to the dark side.

BookEditar

thanks for the info glassman. and i havent joined the darkside quite yet. still weighing my options... im either going to get an FD or keep the VR4, but either way, im planning on building a pretty hardcore autocross/roadracing car.

advantages of FD:
proven performance
cheaper to mod (to get to the level of performance that i want)
probably my favorite japanese car available in the US

advantages of VR4:
more unique (when it comes to building one for the purposes of roadracing/autox)
would still be able to burn people on the street
my second favorite japanese car available in the US

ahhh decisions, decisions. im like 80% on getting the rx7 now. the deciding factor is just the fact that a few of my good friends have VR4s and if i get an FD, ill still be able to drive both. but for now, im still planning on getting a last summer of racing the VR4 in, but hopefully ill be in the rotary crowd by next fall or spring.

another question about the FD...

about how much money would it take to make the engine much more resistant to overheating? im thinking along the lines of better oilcooler, radiator, etc. non-performance mods (per se).

crazysuprakid

The cars acutally fairly cheap to mod if you do it yourself.
Assume
400 for radiator
150 for ast
don't know much about oil coolers but maybe you could get them off of a parted out r1...

the_glass_man

iTrader: (2)

Start off with an R1 or R2 with dual oil coolers.
Delete or upgrade AST. $30-$60
Upgrade Radiator/ Koyo $340
DP with Jethot Coating $300
Fan mod $cheap
This makes for a pretty healthy track car.
You could also try using Evans coolant, and if you want to go even further upgrade to a vented hood and the 99 Spec front bumper.
Also using a good oil like Mobil will help keep temps in check.
I've also yanked out all the crap you don't need, A/C, PS, Airpump, etc...
To help keep heat out of the engine bay.

Kahren

iTrader: (13)

any single is still far slower spoolup then the twins, donno about the modded twins...

i dont see howa gt35/40 is a quick spoolup
its NOT

the_glass_man

iTrader: (2)

Full boost by 3,000-3,500 RPM is pretty quick, show me another turbo that will spool just as fast and make 400+ rwhp on a stock engine.

Kahren

iTrader: (13)

shwo me a gt25/40 dyno sheet that spools at 3-3.5k

vosko

iTrader: (4)

my T78 spools pretty damn fast.... ask kahren

the_glass_man

iTrader: (2)

GT25/40?
Dyno sheets don't really display most of the information about spool-up. They show that amount of boost you will get by planting your foot and revving through the tach.
They however fail to show how quickly boost will rise if you are already at a set RPM.
So many other things come into play as for as spool, lag, boost threashold, etc...
Porting, Exhaust, Timing, all play an important role.

the_glass_man

iTrader: (2)

So fast, I don't think the car would still be in one piece by the end of an Auto-X course.

Kahren

iTrader: (13)

vokos car has good low end very drivable, no need to downshift to pass people at highway speeds. still not twins but i think very good fora t78

oh and umm its a beast!

redrotorR1

BookEditar, auto-x worthy and road racing worthy are two entirely different scenarios. For auto-x, the overheating problems are not as much a worry even with a stock setup. Road racing will absolutely require that your cooling system is up to snuff. In terms of turbos, here are my pros & cons list between single vs. twin:

SINGLE PROS
More boost
Linear power delivery
Lots of top end
Free up a lot under the hood .... lower engine bay temps

SINGLE CONS
More expensive
Longer boost lag
Some fab work necessary/Will (eventually) require to do a lot of catchup mods (bigger injectors, fuel pump, etc.)

TWINS PROS
Quick spooling/short boost lag
Sequential setup .... good for applying power at early apexes
Less expensive/straight bolt-on

TWINS CONS
Less boost
Still cluttered under hood .... twins run HOT --> higher engine bay temps
Sequential transition can get you in trouble

Ok, that being said, I have auto-xed both single and twin turbo RX-7's .... it's hard to compare. Both have their pluses and minuses. I found the single turbo lag to be almost intolerable ... but the linear power delivery is awesome. On the flip side, I love my twins' quick spool delivery but it's peakiness requires a bit more finesse. Keep in mind that, in auto-x, you will rarely get out of second gear and you will rarely be at WOT for longer than a couple seconds on course. Time trialing/road racing .. I enjoy the low end response of the twins, but a single would do much better in the straights and some of the narrower esses. And with overheating being more of an issue in track events, anything you can do to lower engine bay temps is a good thing. But in the end, it's mostly about the driver anyhow ... so do your homework, find out all the info that you need to know, and pick whichever application YOU want. Good luck.

Coulthard Fan

I'm going to run a full season of SCCA autox in the SM2 class this year with the 99 spec turbos. The throttle response with these turbos is just awesome so I'm hoping that they will help mask my shoddy cone-dodging skills.

For the track though, a single turbo is the way to go. On another note, I've never seen a VR4 at the track.

red 7

spoolin up and full boost by 3-3.5K who runs around a autoX at this rpm?

BookEditar

what single did you use? full boost by 3.5k doesnt sound intolerable to me... are most upgraded TT sets (not rebuilt) sequential or true linearly running twins? i think a single would be the way to go for me, but i would definitely like to find a quick spooling one. the gt35/40 sounds nice.

coulthard fan... you dont happen to be scottish do you?

enuttage

I'll jump in here.

As RRR1 knows, I'm running an RX6 regularly at autoX events, and the spool up is *almost* identical to stock twins. You're pretty much full in by 3200.

I'm also running the '99 spec bumper, Fluidyne, CWR dual oil coolers, and a GReddy SMIC. And I too, am running with a street port.

I'm extremely pleased with the autoX potential the car has, and its maintained streetability.

RRR1's Type RZs are seamless out on the course (we've swapped runs once and will do so again). He points out some great pluses/minuses of both setups. I tend to disagree with him just a tiny bit on the intolerable lag part, and personally I really did think the turbo transition on his car was just about flawless (but I haven't driven his car but once, so obviously he knows the tricky middle ground between turbos). For the most part though, power is not necessarily the issue. Grip and driver are huge. Regardless, he's got very good advice above.

If you've got the money to spend (read: squander ), I suggest you go single, IF you're also going to be using the car as a street setup. It's hard to beat the extra power. If it'll be autox only, I suggest getting some seat time with some willing volunteers just to see what things feel like with each setup.

Without the Fluidyne, I had a few overheating problems running courses last summer, but since the rad switch, I'm almost never seeing over 90 or 91C, which is *plenty* cool enough. We'll see how hot things get this summer. Running NPG+ also, so I don't know how that'll affect things.

Good luck with whatever you choose to get setup with.

-E

redrotorR1

I ran in enuttage's A'pexi RX6 turbo'd FD. I make no bones about it, that car is FAST. Boost kicked on right about 3300-3500rpm. It's a fun ride ... definitely different than driving mine with the twins. As far as the twins go, I don't know of many other aftermarket twins for the FD. Maybe the HKS twin kit ... but otherwise, stick with either the stock turbine assembly or the 99-spec RB or 99-spec RS/RZ turbo assemblies. The BNR and M2 BB turbos are rebuilt and cored-out stock turbos and, from my impressions, are really built for high boost applications. Again, I bring up the point about WOT on course. The sequential setup is an FD thing and only available on the Mazda turbo assemblies (actually Hitachi). I don't know what you're asking about the linear running twins ... perhaps you mean non-sequential? In that case, you have the same issue as a single turbo ... longer boost lag. The BNR and M2 BB turbos usually run non-sequential.

I personally don't think the GT35/40 combo is worth the money ... at least not for auto-x/road racing purposes. Pulls really hard, but you won't get that many opportunities to use that power on course. If I had to choose, I'd opt for the T04 package because it's been used extensively, has been well proven to work, and is the best priced (I'm all about getting stuff on the cheap these days). The A'pexi RX6 turbo is very impressive and shows tons of promise, but the price and non-rebuildability makes me shy away from it. Although, they were practically giving them away about a year ago. It all depends on what you want out of the car.

TailHappy

I'm also going to be autocrossing in SM2 with an RX6. I spent last year in AP with the stock singles. I was thoroughly suprised at how much better my car pulls out of low RPM 2nd gear corners with the RX6 than it did with the twins. Granted, I also had the engine replaced at the same time I got the turbo, so maybe that is more of the culprit. But I think one thing people aren't taking into account, is that even though you may not be showing full boost at 3000 rpm (but it IS there by 3200), the single is MUCH less restrictive and allows the engine to make more power naturally.

If autocrossing is the goal, I personally think you're wasting your money and probably even hurting yourself trying to get any more power than the RX6 will make. I spent quite a bit of time spinning like a top while trying to get used to the new power. In fact, I would seriously doubt that I ever even get the oportunity to floor it anymore. The RX6 will spin sticky tires in 2nd gear by 4000rpm if your're turning at all, and 1st gear is all but useless. In retrospect, I think money spent on suspension bits would give you bigger time gains.

The final thing to keep in mind is that the RX-7 can be very competitive in the superstock class. There's very few cars that can even compete in SS, and most people find it very hard to leave their car stock, anyway. Personally, autocrossing is only something I do for fun, so I modded my car the way I wanted it for the street and track. But if a competitive autocross car is your goal, you should definitely consider the stock class.

Good luck and have a blast!

BookEditar

very competitive in SS? no way, the z06 wipes the floor with rx7s in SS. im planning on being in SM2 because im not going to have any cats and i want to run higher boost.

Kahren

iTrader: (13)

dotn comare full boost, instead compary how much power which turbo will make at certain rpm. i for example liek to take 3k rpm as the low end part of teh turbo where a stock FD will make about 115 hp the rx6 and to4e about 100 hp and the gt3540 and t78 will make about 75 hp.

the twins are without a doubt the best for autox
if u cant use the power thats a diffrent issue

if u want a competitive autox car stay with the twins
if u want a good street car and shine on teh track get a small single like rx6 or t04e

all out power get gt354 or t78

ive seen a bunch of tynoes with diffrent setups and these are my conclusions and are very accurate in my opinion.

enuttage

Check again, my friend...

I'm not saying your RX6 source was making more hp at 3K, but I am

http://www.ladylivewire.com/enuttage/Dyno.jpg

Right around 125 at the rear wheels right at 3K. So *if* stock turbos are making 115 at that level, then you might want to reconsider your above evaluation.

-E

Kahren

iTrader: (13)

hmm what other mods do u have and what was the correction on that run ?

turbojeff

iTrader: (30)

Many courses have me dropping below 3500rpm. It isn't always feasable to shift down in the middle of a corner and shift back up. Low end grunt is critical for auto-xing.

Spool up time WON'T be shown on any dynos. You'll have the car at full throttle boost will climb with revs (of course depending on turbo size). What you need to do is actually data log the throttle position and boost vs time. Show us that the single will spool faster than stock twins. Of course try and make it a fair comparision. If your using a single car with no cats then use a twin car with no cats.

Above all else if you start putting on single turbos then you'll notice that your running in either Prepared or Mod classes. These classes are really for only pure race cars.

Don't worry about doing all the mods you can until you can beat every MR2, Neon, Miata, etc in your club. Until then it is all drivers skill

A National champ driver was only .5 sec off me in a CSP Miata at my last event. I had Top Time and his last run was rained out... I regularly get beat by guys like that.

Jeff