[jlm]

this is copied from the racing forum, where it started, but is now more appropriate here:

"spent all day yesterday with my car on the Helix Minisport Mustang dyno. was able to bring the system back to stock (exhaust and intake) for a baseline test with the exception of the chip. (We tried replacing the ECU with another stock unit, but security code issues prevented it from running at all.)

we then compared to stock (142.6hp), one change at time:

Rogue filter with (143.6) and without metal shield (144.1hp); and with special Helix air flow ducting (147.7hp)
stock exhaust, Rogue exhaust (150.1hp), Supertrapp (142.7hp)(8 discs).

pains were taken to be objective; intercooler temps were measured and runs were made when the intercooler temps were at 130 degrees. (we also made a few runs with cooler and hotter temps to see the effects)

the short answer is: reduce any maufacturers claims by at least 50% if not 75-90%. there is no way we saw anything like even 2 digit gains after hooking up the combined best performers of the bunch. (Rogue intake, Helix intake ducting, and Rogue exhaust; 150.1hp)

our HP measurements were Brake Horsepower at the wheels and varied from an averaged minimum (stock) of 142.6 to 150.1 fully modded as tested.

converting those readings back to flywheel HP, you would have 164 hp and 173 hp. (In the ball park of the factory values!)

Keep in mind that the value of the readings is for the relative values, not for any absolute power claims.

my conclusion is that the only way to get a big increase at this point is to put in a cam and a blower pulley. it may then be possible to get something like the 200hp claims.

it was especially illuminating to see how tiny the exhaust mod increases were.
a cooler intercooler (100 degrees= +2hp, 160 degrees=-2hp)

my track results actually showed the rogue intake and exhaust to run fater than the Rogue intake and Supertrapp, although track conditions were a week apart!


__________________
john

[911ETR]

Just wondering but what is the calculation for converting wheel horse power back into flywheel horse power?

How do you translate the power loss from the trany into numbers?

Sounds like a set of Volk racing rims at 13-14 pounds would make quite of difference over a exhaust but then again on a brake dyno it would show a loss.

Is there any real true way to get accurate power reading? How about a Gtech-pro?

[CSDan]

911ETR,
You do not gain more HP from putting lighter wheels on the car. The difference between WHP and BHP is the power lost through the drivetrain.
Dont rember the conversion formula though, sorry.
....and a g-tech would be the worst way to test power increases-
Daniel

[911ETR]

CSDan,

Quote:

You do not gain more HP from putting lighter wheels on the car.

Why not?, lighter wheels = more useable horsepower @ the wheels. The heaver the mass (wheels) are to turn the slower the throttle response and less useable power.

The real problem is that most dyno's are brake horse power driven which means it measures the time/force to stop the spinning mass. With Lighter wheels you actually reduce the spinning mass and therefore do not have an accurate way to measure horse power at the wheels.

Thats why you really need to understand the formula for the transaxle power loss. Having lighter wheels will change that formula resulting in a different true horsepower reading at the wheels.

Am I smoking crack?

[friedduck]

No you're right. Most dynos are inertial. They measure how much time it takes (rate of acceleration) to spin up a drum with a large mass.

By reducing sprung weight on your car, you in effect, allow it to spin this up faster, which the dyno interprets as higher horsepower.

I know that Eddie Current makes a brake dyno, which can measure HP at a steady-state by applying a brake force to the drum (i.e. you can measure HP while running at a particular RPM.)

Now the crux of it is this. If your car, in real life, really does accelerate faster, who cares if it's *real* horsepower or not. Same effect, no? I actually think that a lot of folks would be better off putting their $$ into wheels instead of intakes. Not only would it accelerate faster, but also handle better (not as much weight to track over bumps.)

And if someone has the opportunity, I would *love* to see what the real-world difference is in terms of #s by just switching wheels. Anyone done this?

Jeff

[friedduck]

Oh, a couple of more points related to the earlier discussion.

Firstly, you would never see a loss on a brake dyno due to wheels. But you also wouldn't see an increase, as it's not measuring a change in acceleration but rather resistance to a force (the brake.)

Secondly, I think you need to split the discussion into two parts. Dynos measuring measuring engine output are great for tuning engines. Add an intake, or change a parameter on an ECU, and watch the corresponding output increase. Great. Chassis (right term?) dynos measuring acceleration, though, are a more accurate impression of what you're going to feel on the road.

In fact, the idea of using a G-tech, while maybe not as accurate, seems to me to be a good way of quantifying the real-world impact of changes. Personally I don't care if it's wheels or engine. If I drop a half-second to 60, I'm happy

Jeff

[911ETR]

Thats where my bang for the buck lies first.

With some 14 pound per wheel Volk SE37k's I imagine that you should feel a very noticeable difference.

The stock rims weigh 27 and the Stock BBS weighs 26 pounds per.

[911ETR]

CsDan,

Quote:

....and a g-tech would be the worst way to test power increases

Have you ever tried the Gtech pro or competition?

I have always heard good reviews, what makes you say it's the worst way to test?

[jlm]

if you check out the Englishtown post in the racing forum, you will find that my modded car (14lbs per wheel lighter than stock, chip, exhaust) was not quicker in the 1/4 than a stocker (we both had intake mods, the stocker had 17" wheels with runflats, stock exhaust.) We even used the same driver. 15.3 and 92mph, both cars almost the same.

I was expecting substantial improvements from the wheels and chip, but it didn'e turn out that way. Now I'm on a crusade to cut through the BS and find out what really works.

[Andy@Ross-Tech.com]

Okay, there definitely is adaptation (for lots of things, most notably fuel trim). This can cause strange things to happen, but who knows how much of an impact it has on the Siemens system in the Mini. The only way to know for sure is to do a baseline, do a dyno immediately after the mod, then ado another dyno in a day, a week, a month, whatever.

As far as dyno's, the most popular type out there is an inertia dyno, like a DynoJet. This measures power by measuing the acceleration of rollers of known mass. At any point in time, the rollers are spinning at a known speed and the kinetic energy can be calculated from that speed and the mass of the rollers. When the roller speed is higher, the new kinetic energy is calculated. The change in kinetic energy over time is power. Torque is calculated from power and RPM (RPM is either recorded by inductive pickups on the plug wires, or is calculated based on gearing and roller speed).

Helix has a Mustang load dyno. This is able to apply energy to the rollers to counteract the energy being imposed by the car. Picture a big electric motor attached to the roller. By knowing the amount of electricity you are supplying to the motor, and the efficiency of the motor, you can figure of the power being applied by the car. This is pretty cool, since you can pick a specific RPM, and hold it while measuring power.

[911ETR]

JLM,

How is that possible? Something is wrong. I have seen instances not on Mini but others that they replace a exhaust thinking it will give them more but actually takes away HP.

I would bet that the rims are a sure bet but what ever Chip and Exhaust you used to be suspect. What Chip and Exhaust?

How about the weight of the drivers? Do you also have a Sub or anything of weight in the car.

Also I have noticed that break in period is a huge factor.
I have always gotten more HP out of the motor by beating the crap out of the car after about 500 miles. Yes it is true you can take life away later on from the car but I do it anyway.

My car comes in 2 weeks and the volks are ready. My brother has a stockie S. I will compare and see. I think I am going to buy the new gtech competition. Even if its not accurate, going from one car to the other should show a credable deference.

[CSDan]

Quote:

Originally posted by 911ETR
CsDan,



Have you ever tried the Gtech pro or competition?

I have always heard good reviews, what makes you say it's the worst way to test?

Yes-and a Dyno is a much better way then the g-tech--I am not saying that its bad in general--I meant(sorry for the broad statement) if you want an accurate reading of you HP a cyno is your best bet--g-tech is a good cheap alternative--but I have never seen them as accurate as a dyno.

And what I said earlier about lighter wheels making more HP--I thought you meant form the motor(dont laugh--I know people who have actually thought that) not at the wheels. the car will certianly feel quicker on light weight wheels and will brake much better too. Turn in response will be quicker as well. Ill stop ramling as you probably know all this already.

Daniel

[911ETR]

CSDan,

First

Second, You are right, a dyno is way more accurate but very spendy every run. I just want to know I am getting something out of my mods without sacrificing the cash for my next mod.




Question, Should there be a newbie performance section then a test to graduate to the real Tunning Forum?

[jlm]

all the data is in the racing forum post, but:
chip: Evotech from Mini Madness
exhaust: Rogue, Supertrapp and stock (all dynoed, first two at the strip)
intake: rogue and stock (rogue testa the the strip)
wheels: Oz superleggera 16 and Toyos (34lbs each)
sunroof: that must be the culprit!
the car has been well broken in; by that I mean it has seen all of its rev range since 500 miles in a sensible way plus 14 runs at the dragstrip and about 20 runs on the Helix dyno, plus normal zipping around.

[macncheese]

Brian Garfield did a stock wheel versus Enkei RP-01 comparison a few months back. Search the archives.

[DEye]

[quote=
And if someone has the opportunity, I would *love* to see what the real-world difference is in terms of #s by just switching wheels. Anyone done this?
[/QUOTE]

I haven't done it yet, but plan to, i have a Cooper with the 16" (195-55/16) runflats and a set of 15" Rota Slipstream's with Falken tires 205-50/15.

With almost 1" difference in height and 8 lbs in weight reduction give me a slightly better ratio at the wheel and less weight...

It certainly feels different when i swap wheels, but i plan to dyno it in the spring after i get it chipped....