blackrotary23

we had a 91 n/a ran on a dyno today. it has a custom fabbed intake which is all one piece and half the size of the original stock intake. advanced the timing, no emissions, new fuel pump. the car runs good seeing that there is no management system on it to adjust timing, air/fuel, and so on. i was estimating around 225hp but instead, the dyno read 125.8. how do you lose horsepower from 147 stock hp? this thing will smoke pretty much anything we come across, and yet, the horsepower reads less than a honda civic. i think the people at the shop didnt set up the dyno properly because it is exactly 100 hp less than from what i predicted. let me know what you think the problem might be.

misterstyx69

iTrader: (142)

you estimated Way to HIGH.(sorry,not tryin to jack ya.)
there is no way in hell that a N/a would do 225 hp without significfant modification..and that is BIG Bucks..
look into "Beefy N/A" thread (search) you will see some good Tips for Building up the N/A.
OH..look also at Posts by KAHREN..he built a close to 200 HP N/A.

walken

iTrader: (6)

you'd make more horsepower with the stock intake and emissions setup if you don't want to run a standalone. for now you should get a s-afc and tune it.

need RX7

iTrader: (4)

3 reasons:
a) Factory power ratings are always a bit high (y'know, horsepower sells cars, etc...)
b) They are rated at the flywheel (before drivetrain losses)
c) ~20 wears of wear, etc takes a toll

and a "custom fabbed intake which is all one piece and half the size of the original stock intake." doesn't sound like it's doing the power level any favors.

Any car you throw on the dyno will read much lower than the factory rating, old or new. I saw a show on TV one time where they dyno'd a brand new Mustang GT, which was rated at 300hp I believe, and they got ~260hp out of it. Peak dyno numbers don't mean much anyway, unless you're after bragging rights.

Black Knight RX7 FC3S

iTrader: (7)

all car manufactures mesure HP at the flywheel. They dont account for drive train loss which ranges from 15%-30%. When you go dyno, it does measure the power that is transmitted through the drivetrain and put onto the ground.
And 225 hp haha, you need to spend Huge amounts of money to get that on a n/a
128hp is about 150hp at the crank, so your engine is pretty much as powerful as a new fc.

TYou are going to have to do major porting or a very huge street port to get to atleast 180-190hp, and a standalone.

1SWEET7

iTrader: (1)

I wish Mazda would have under rated the horsepower on the RX7's like some of the muscle cars in the 70's that would have been sweet.

K-Tune

iTrader: (26)

learn to estimate better :]

unless that intake was made with a flowbench, i doubt it is adding any horsepower.

KompressorLOgic

iTrader: (6)

lol what do you have for exhaust? engine porting? lets see some pics of this "intake"

solareon

iTrader: (1)

well if the emissions removal on that car deactivated both the 5th and 6th ports and the vdi then you are losing quite a bit there. Also if its the stock ecu it gets hella rich uptop

Squeeb

iTrader: (4)

S5's 5th/6th port actuators don't engage off back pressure from the exhaust, that's S4's your thinking about

need RX7

iTrader: (4)

But if the emissions removal included removal of the air pump, that would cause the 6pi and VDI to stop working on an S5.

jinxed4dub

iTrader: (7)

What kind of intake are we talking about here, a cold air intake, or an actuall intake manifold? If it is an intake manifold what is it made out of as far as thinkness? do you have heat sheilding? I hope your not hoping to make big numbers with just a CAI?

ParadoxToday

Its like havinga Civic SI w/ vtec engine... without the VTEC lol

fstbckgt

iTrader: (1)

they didn't really underrate them in the 70s, they just gave the hp and tq readings at an rpm level far below what the engine could rev to

gkarmadi

iTrader: (20)

Even a T2 isn't gonna make that power without quite a bit of modifications.

SoloII///M

iTrader: (13)

You need to find some faster cars to race.

Julian

iTrader: (14)

There was NO muscle car of the 60's or 70's that was Underrated far from it they reported a gross HP that did not even account for the paristic losses due to water pumps, oil pumps, exhaust sytems etc.

Just ask yourself why a 425 Hp corvette of the past was not as quick or able to acheive the top speed of a 400 Hp C4 ZR1.

Mazda does not skimp on intake design, they were one of the first companies and ist production car companies to incorportae dynamic intake charging using the shock waves inside the manifold to pressureize the intake at certain rpms. Runner length and volumn are very important shorter does not make for a bigger HP curve.

SoloII///M

iTrader: (13)

Tires and aerodynamics, primarily, but also gearing.

wrankin

With stock internals (rotors, porting), an NA S5 will top out around 175rwhp. This is what the road-race guys are getting, and that's with an open exhaust, good (stock) intake, aftermarket ECU and a lot of tuning.

As mentioned earlier, if the car was running with the 5/6-ports and VDI disabled (and closed), then that's probably half your top-end power right there. When you say that you "replaced the intake" are you talking about before or after the throttle body? What did you do with the AFM? If you replaced the UIM, then all bets are off.

Where did you get your 225rwhp figure?

-b

wozzoom

The VDI intake on the S5 NA is worth about 10-12 PEAK RWHP on the dyno. You deleted it and lost that.

MaczPayne

iTrader: (5)

The problem is you not understanding how horsepower ratings work.

1SWEET7

iTrader: (1)

(Excerpt from http://forums.motortrend.com/70/5020...nes/index.html)

Many muscle car fans know that the power rating of many classic muscle car engines were deliberately underrated. It was usually done for two reasons... 1) to lower insurance costs and 2) so the car could be in a more favorable class in NHRA drag racing.
Here is a chart from a muscle car magazine from the 1980s. Written by Roger Huntington, who wrote articles and road tests for many car mags, including Motor Trend.

Here is the chart from the magazine:

Make/---------------Adv.------Adv.------Actual
Engine size---------HP--------Torque----HP

Buick 455 Stage 1---360@5000--510@2800--420@5400
Camaro Z-28 302-----290@5800--290@4200--310@6200
Chevelle 396 L-78---375@5600--415@3600--400@5600
Corvette 427 L-88---430@5200--450@4400--480@6400
Mopar 340-----------275@5000--340@3200--320@5600
Mopar 440-4 bbl-----375@4600--480@3200--410@5400
Mopar 440-6 bbl-----390@4700--490@3200--430@5600
Mopar 426-Hemi------425@5000--490@4000--470@6000
Mustang Boss 302----290@5800--290@4300--310@6200
Ford 351 Cleveland--300@5400--380@3400--340@5600
Mustang Boss 351----330@5400--370@4000--360@6000
Mustang 428---------335@5200--440@3400--410@5600
Mustang Boss 429----375@5200--450@3400--420@5600
Olds 455 W-30-------370@5300--500@3600--440@5600
Olds 350 W-31-------325@5400--360@3600--350@5800
Pontiac Ram Air 400-366@5100--445@3600--410@5600

These figures of actual hp do make sense. I mean, no muscle car fan believes that the Ford 428 was making the same hp as the 390!

However, some engine's ratings were not underrated. Here are some which was correctly-rated:

Make/engine-----------Adv./Actual hp--------------------

Buick GS 400----------340@5000
Camaro Z-28 350-------360@6000
Corvette 427 Tripower-435@5800
Chevelle SS 454 LS-6--450@5600
Ford 427 Dual Quad----425@6000
Fairlane 390 GT-------335@4800
Olds 4-4-2 400--------350@4800
Plymouth/Dodge 383----335@5000
Pontiac GTO 400-------350@5000

Read more: http://forums.motortrend.com/70/5020...#ixzz0aRIf12VE

blackrotary23

http://www.youtube.com/watch?v=g8DPmJrq9wA

here is the link for the youtube video we made. it took a long time to build this damn thing, and i am just trying to get as much horse as possible out of it. does anyone know where i can find a wiring diagram for an SAFC? i need to know where what wire goes where, i bought one used and it didnt come with instructions. i need to tie it into a 91 n/a. thanks!

RW-7

iTrader: (56)

Looks to me like you are losing a bit with that intake. First off your intake runners are mot equal length, and second it looks way to short for a stock port motor, and also it looks like you have all ports open at all times. There is a reason Mazda spent many many hours on designing an intake mani for the rotary, IT Works and it is very efficiant at what it does. The stock mani only flows to the primany ports at semi-throttle. That is all the engine needs, The runners are lengthened to be very efficiant at both low and higher rpm range. The Dynamic chamber is a work of art in itself the way it manipulates the airflow. Not to mention the 5th and 6th ports, and VDI (Variable dynamic Intake) wich uses pulses of intake air to charge the air flow.
My advice, put your stock intake back on, with the emmisions and do another dyno pull. I would be very interested to see how much your numbers INCREASE.
Good luck!

RotaryRocket88

iTrader: (7)

That video also shows an S4 manifold that was removed, so this is apparently an S4 engine in an S5 car (who knows why). Properly set up an S5 VDI manifold and more power is easily within reach.