Danny 171

Hey guys! So I have an 87 S4 TII but bought an S4 N/A 13b to drop in since we're gonna road race it but I'm just wondering what kind of power you can get out of it without breaking the bank (too much). We're unrestricted so it's just a HP/weight ratio they go by. It seems for about $2000 you can get a TII to near 300hp, what could you get out of an N/A for similar? What could a big streetport get? What would bridgeport require? Other than fuel and cooling, would it need to be balanced and clearanced? How is that done

diabolical1

iTrader: (3)

it would probably help more if you stated what year/Series engine you bought.

Danny 171

Sorry, turbo is S4 and Haven't looked too much at the N/A but 90% sure S4

Aaron Cake

iTrader: (1)

For an S4 NA, in realistic daily driving form, 180-190HP at the wheels. That's with a mild street port, and a well tuned standalone.

Your NA upgrades to add 40HP consist of:

-Header
-Cat removal
-High flow "catback"
-Cone filter in cold air box
-Reasonable street port
-Well tuned standalone

You can make crazy NA power if you wish, but as the power goes up, the streetability goes down.

400HP is possible if you want to wear ear plugs and rev to 10,000 RPM. Most people would not consider that car drivable on the street.

j9fd3s

iTrader: (3)

S4 NA stock port, with stock intake, whatever ECU and exhaust you want will do 154 rwhp, +/-1hp. S5 intakes add about 10-12hp.

a street port adds about 10-15hp. highest i've ever seen on stock FC intakes is 180rwhp.

jjwalker

Stock advertised power levels, lol

I got 200hp on the engine dyno after a street port and rebuild, so really j9fd3s is correct, 180hp to the rear wheels is about all your going to get.

Aaron Cake is also correct, 400hp is possible but you are going to spend a butt load of money and you won't be able to drive the car on the street. Part of that large amount of money is going toward hearing aids.

Danny 171

The car is going to be for track only so streetability is not a concern. I know a bridgeport makes it's power a lot higher in the rev range than a streetport so what is necessary to build an engine to withstand the higher rpm's? Racecar tech doesn't always get a ton of hits so I figured I'd ask in the second-gen forum first

diabolical1

iTrader: (3)

carbons
lightening with full balance
rotor clearancing
oil mods
appropriate intake (tuning recommended, though not necessary)
exhaust (again, tuning recommended, but not necessary)
scatter shield/ballistic blanket
ignition fortification
engine management

that would represent a pretty all-out setup that doesn't involve custom machining (adding a bearing, direct oil line, etc.). of course you can build something less and still make decent power. people have done it.

driftxsequence

iTrader: (8)

if youre going to be road racing stay with the NA for reliability sake in my opinion. Either do a large streetport or a bridgeport and the key is to have an aftermarket intake. The long stock intake chokes top end power thus why you see many cars capped at around 180-190HP. Most aftermarket intakes are to accept carbs but ITB's can be bolted on to some, and injectors can be added. David Chang has a S5 NA with aftermarket intake, cheeseport bridge and made 215WHP on a megasquirt.

j9fd3s

iTrader: (3)

we bumped the oil pressure, and then just ran the junkyard engine up to 9400rpm. after a season of that, engine is tired, but its not broken.

wouldn't hurt to run the oil baffle plate, and then make sure the rotor tip to side housing clearance is on the big side.

BLUE TII

iTrader: (9)

The car is going to be for track only so streetability is not a concern. I know a bridgeport makes it's power a lot higher in the rev range than a streetport so what is necessary to build an engine to withstand the higher rpm's? Racecar tech doesn't always get a ton of hits so I figured I'd ask in the second-gen forum first

Overlap from Bridge or Peripheral port makes more power everywhere.

Race engines with said porting make more power on the high RPMs because one makes more horsepower by revving the engine higher (HP is a calculation of work done over time). Therefore, NA race engine tuning is all about gaining/maintaining power in the high RPMs and changing gearing to suit.

Why I am saying this is if you are on a budget you can skip all the machine work, expensive seals and custom rear end gearing and a trans that can shift at high rpm needed for a high power/high rev NA engine by still going with the high overlap porting (bridge or peripheral port) and keep the port closing timing conservative for a lower redline.

You will get more power under the curve (torque) than a streetport, but because of the large overlap you do still need a suitable short runner intake and very loud exhaust- luckily these are not too expensive.

A bridge or semi-p-port can use a cheap Holley (4150) style short runner manifolds and an injectorless 4 barrel throttlebody with big injectors (1,000-2,000cc) in the stock primary injector location.

If you have the 4 port turbo side/intermediate housings that originally came in the TII chassis you want to use those as a base instead of the NA 6 port housings as the ports flow more,

For the most torque a low rev full P-port would be a viable cheap option as well if you are a bit of a fabricator. Again, 4 port side housings are best to use even filled in as the 6 port housing will wear your side seals faster.

You say you want to roadrace the car.

The class you choose will dictate what motor and what you can do to it.

If its NASA you can do what you want, but evaluate different builds to see what nets you the least points per/ performance gain.

j9fd3s

iTrader: (3)

this. in the irony department every sanctioning body has rules, and every race track has sound requirements so the 2/3 Peripheral port cars i know of are street cars, mine being the exception.

in the non irony department my PP with mufflers and a quiet air cleaner is actually the same DB on the track as my friends stock port FC ITS car, i also make peak power at a lower RPM than he does (thanks to the air cleaner, its too small), and not only do i make more power than he does by about 25hp, but i get better mileage as well.

so in reality, PP is just better, side ports are "Franz: Which is flab! cYah! And stretch it into a flab-rope ladder, so you can climb back down into the sewer you crawled out of! "

Danny 171

We're looking into running NASA ST3 which just uses an adjusted weight/hp ratio. We need to hit 9.0/1 so for example 2300lbs/255hp=9.02

I'm not sure what a stripped and caged FC would weigh but the lighter the better. Also means we need less power to meet our goal. Either way, it seems we'd need in the ballpark of 250hp (give or take 20hp) so that seems quite drastic for N/A unless we did a bridgeport or PP. I basically have both a tii and n/a engine now so i could use the 4 port irons no problem. Would it be better just to go for PP? I understand the process but I've heard people run into problems with the intake as the air can act funny or not as you'd expect but obviously that's just what I've read before. Also with that, I'd love to run the car at a higher rpm to make use of some of that power, but nothing insane as I can't justify a crazy amount of money at this point.

BLUE TII

iTrader: (9)

So Nasa uses peak hp #s instead of area under the curve calculation?

Well then, you definitely want a (relatively) low rev motor with lots of torque.

This doesn't rule out your NA rotary build, but remember just rebuilding the TII back to stock would kick most built NA rotaries *** all around the track.

If I remember right from my glance at NASA rules cutting the firewall and putting the engine in the middle of the car is absurdly low points. How race car do you want to get?

j9fd3s

iTrader: (3)

yes that is correct. so ideally you want to hit your peak HP at the bottom of the rev range (5k rpm?) and then that stays flat all the way up until you shift. in practice this is a bit hard, as the torque needs to drop off really fast to do it. its easy to trim 2-5hp off the top. or you can run an intake restrictor, contrary to popular belief they don't affect power until it is the limit in flow, and then it does

Danny 171

The problem is we're required to keep the trans tunnel and floor pan unmodified

BLUE TII

iTrader: (9)

The problem is we're required to keep the trans tunnel and floor pan unmodified

Ah, got it- NASA ST3 "Production Car" rules.

5)
Modification and/or relocation of components of the firewall with engine
relocation ten (10) inches or less (ie. no mid or rear engine conversion) is permitted,
but is significantly limited by the requirement to retain the unmodified transmission
tunnel and floor pan.

So, you can dry sump, lower your engine and move it back and if something hits the firewall you can modify the firewall, but the trans tunnel and floor pan are sacred.

That will get you about 8" to the max 10" engine set-back with the rotary max I guess.

j9fd3s

Quote:
Originally Posted by BLUE TII View Post
So Nasa uses peak hp #s instead of area under the curve calculation?

yes that is correct. so ideally you want to hit your peak HP at the bottom of the rev range (5k rpm?) and then that stays flat all the way up until you shift. in practice this is a bit hard, as the torque needs to drop off really fast to do it. its easy to trim 2-5hp off the top. or you can run an intake restrictor, contrary to popular belief they don't affect power until it is the limit in flow, and then it does

I didn't see any weight break for NA rotary versus single turbo rotary, am I missing something?

Rotary weight break includes 1 turbo?

Engine:
Rotary with a maximum of two rotors and one turbocharger turbine = +0.3

Small compressor upgrade on stock S5 turbo you should be able to get about 250hp from 3,000rpm to 8,000rpm with 350ftlb @ 3,000rpm on race gas if you get 20psi boost ~ 3,000rpm and bleed it off fast in the high rpms with a large external wastegate and some boost control.

That would be a grunty 250hp compared to a maxed out low end and then flow limited top end NA rotary 250hp that would have linear power gain from ~70hp @ 3,000rpm to 250hp @ 5,250rpm and then maintain 250hp to 8,000rpm.

j9fd3s

iTrader: (3)

in PT/TT you can do points OR a dyno reclass. with the dyno reclass you send them the points sheet and they tell you how much HP you can make, and minimum weight. so if you opt for that you could pretty much do anything, and then they will give you the weight/hp numbers.

its a big mystery where they come up with the reclass numbers, but it works ok.

it seems a bit weird, but it works well. its not like the SCCA where you need to find a cylinder head that's been out of production for 47 years, or have the correct interior A pillar trim or something

we ran the numbers for the FC in TT/PT once and its a bit weird as you're either like 2900lbs/300hp or 2300lbs/200hp or something, neither of which is really the happy spot

Danny 171

I think I'm leaning towards running turbo. Based on what you've all said it seems to make the most sense with a hp/weight class. Thanks for all your input! I'm slowly trying to learn more and more about modifying a rotary

BLUE TII

iTrader: (9)

There is a steep learning curve with the turbo stuff though. Especially when you are doing something weird like building a rotary for torque.

You could get racing with an NA and play with a turbo set-up on the side and put it in when its sorted.

in PT/TT you can do points OR a dyno reclass. with the dyno reclass you send them the points sheet and they tell you how much HP you can make, and minimum weight. so if you opt for that you could pretty much do anything, and then they will give you the weight/hp numbers.

I guess ST3 is power to weight only class.
You can choose "Production Car" for the rule set or "Non-production Car" and get assessed for "Modification Factor".

The power to weight is adjusted by factors (- actual weight or + actual weight) to class the car in ST3, ST2 or ST1.

The “Adjusted Weight/Power Ratio” for each vehicle will be calculated based on a simple
competition weight to peak chassis dynamometer (Dyno) horsepower ratio (Wt./Hp), followed
by the adjustment of the resulting ratio by adding to, or subtracting from it, based on the list of
“Modification Factors” below. Competition weight is defined as the minimum weight of the
vehicle, with driver, any time that it competes in a qualifying session or race. Note: peak chassis
dynamometer horsepower and dynamometer testing procedures are defined in Section
8
.

7.4.2 Modification Factors
The “Modification Factor” listed after each item below is added or subtracted from the actual
measured Wt/Hp ratio to determine the “Adjusted Wt./Hp Ratio” that determines vehicle legality
in each ST class.

Engine:
Rotary with a maximum of two rotors and one turbocharger turbine = +0.3
Naturally aspirated (non-rotary) engine with displacement 1.9L or less = +0.3

Rotary engines with up to 1 turbo and engines under 1.9 liters got a break to the power to weight multiplier as I mentioned. Presumably because on traditional set ups both lack torque/ area under the curve power.

ST3 seems to suit the FC well as non OEM aero is assessed a weight penalty and the FC has a low Cd and low and F/R neutral lift with the factory Aero kit.

If you choose a compressor wheel that maxes at your desired CFM/HP output on a rotary and boost the **** out of it you will subvert the dominant paradigm and make much more torque than hp on a rotary.

Example 1-
Stripped FC weighs 2250lbs / (penalty from lighter than mean vehicle weight -0.3)= 1731lbs assessed weight X (handicap weight from torqueless rotary +0.3)= 2250lbs assessed (and actual) weight. Allowed HP at class max 9:1 = 250hp.

Example 2-
Full interior street FC weighs 2650lbs / (penalty for lighter than mean vehicle weight -0.2)= 2208lbs assessed weight X (handicap weight from torqueless rotary +0.3)= 2870lbs assesed weight. Allowed HP at class max 9:1 = 316hp.

Danny 171

We're going to get it as light as possible but even then and with the learning curve, it still seems turbo would be the best route for ST3 without spending a bunch to get power out of an N/A

Danny 171

How restrictive is the S4 TII intake? Would it be a better idea to go to an S5 intake or something aftermarket/custom fabbed

BLUE TII

iTrader: (9)

Either S4 TII or S5 TII intake should be great for making a bunch of power down low like you want on a stock or street port.

If you bridge/semi p-port you would want a short intake manifold. That kind of overlap really spools a turbo, so you would have to go crazy with a couple big external wastegates to avoid overspeeding the little turbo.

Danny 171

Can you go bridge or semi p-port on a stock turbo? I know those things are tiny and ineffecient

celbii

iTrader: (2)

My N/A makes 185WHP, Which I feel is about as much as it will do without dumping alot more money in it and still keeping it street-able. relevant info:

Details
-GTUs Model (only 100 in 1990)
-148,xxx miles on chassis
-Less than 2,500 miles on fresh 6-port streetport by Kevin Landers of Rotary Resurrection, built Oct 2012, dyno-tuned by Chris Ott at Rotary Performance in Garland TX, to a very stout 185whp.

Engine
-3rd gen housings
-Full 6-port streetport
-Atkins 2mm apex seals
-Stock air pump actuating auxilary ports
-Atkins 1-piece machined auxilary port inserts
-All gaskets & o-rings replaced
-OMP operational
-All silicone vac lines
-Exhaust diffusers removed
-Stock TB, solenoids, etc and all functional
-Removed AC and PS
-Mazda Competition motor mounts
-Cork Sport SS oil lines
-Aluminum thermostat neck

Exhaust
-Racing Beat header, uncollected, Jet Hot coated
-Header lightly port matched to exhaust ports
-Full, uncollected RB exhaust with presilencers
-No cats

Suspension
-4.3 ratio rear end LSD

Trans
-Smooth, no grinds
-Short shifter
-Fresh bushings 2010
-Center Force Dual Friction clutch (awesome)
-Stainless clutch lines
-Suspension Technologies mounts
-Racing Beat steel flywheel (awesome)

Electronics
-Apexi SAFC in glove box – dyno tuned by Rotary Performance
-Mallory HyFire 6 CDI ignition box
-Custom engine power and grounding kit
-New Odyssey Mini Gel Cell in stock location
-MSD Super Conductor plug wires
-Aftermarket Gauges:
--Autometer oil press
--Autometer water temp
--PLX wideband