MazdaManiac

iTrader: (3)

Though, the discrepancy can screw with your driving. It tends to trick me into shifting too early - adding a processing layer for intrepreting what the tach really means is a distraction.
Also, when chasing a particular tuning issue that you have located on a datalog, it can be an annoying time trying to hit that load point while behind the wheel.

Hymee

iTrader: (1)

Good points I guess. If you are tuning and using a real time scan tool with logging, you could use the RPM gauge on the scan tool, as it is using the "real" RPM signal.

Cheers,
Hymee.

MazdaManiac

iTrader: (3)

Yeah, but that is not under my nose. I'd have to look at the monitor (though that is not too far off in my setting - but it still isn't part of my normal line of vision when driving.
Plus, scan tool lag is significant when observing RPM in real time.
I'll occasionally use the RPM output of the E-01 instead (since it is essentially analog), but that is even further outside my visual line.
The tach is where it is for a reason.
Additionally, the RPM reported over the CAN bus has a fair amount of "scatter", though that can be normalized out. However, that makes it not a true source of RPM, either.
The most stable source of RPM is one that is actually mechanically (electrically) derived from the ignition signals - the one your EMS provides.

Skiptomylue

no, it didnt offened, it was a legit question i asked though, but i dont offend Easly.. i can get mad quick once in a while.. dont know why.. just happends, red hair i suppose,
i guess i shouldnt worry to much about the tach misread then as im not into the whole "tuning" thing yet, so, its all the same guff to me!

Richard Paul

iTrader: (5)

That's 8500 in 6th gear, right? Unblown, maybe off a cliff.

paulmasoner

iTrader: (1)

I havent been following this thread, nor have i come close to testing top speed in my car. But i would guess he's not too far off. I have pushed mine to 145 on a slight incline with plenty of room to go. Based on average RPM change per 10mph change(i know its not linear relationship) i estimated my car would top out just over 160

BoosTED

iTrader: (2)

He has the stage 3 Mazsport Turbo...

GReddy Oil Pan
- GReddy Oil Catch Tank
- GReddy SP2 Catback Exhaust
- HKS BOV SSVQ
- HKS Ignition System
- HKS Oilcap
- Mazsport Turbo Kit Type III
- Mephistogrey ECU Cover
- Mephistogrey Fuse Box Cover
- Mephistogrey Battery Cover
- NOLOGY HotWires
- RE-Amemiya Oil Cooler
- R-Magic Hi-Flow Cat
- SUN Hyper Voltage System MR
- SUN Hyper Ground System

epitrochoid

no way you can get over 150 on a level road without boost

paulmasoner

iTrader: (1)

i know wind resistance and friction are killers over 140mph.. but i think as long as you dont have headwind i could hit 150. like i said, i hit 145 on a very slight uphill grade. granted it took me forever to get from 130-135 up to 145. but i would think on a level road, no headwind, and enough room, you could do more than 150

Keef

ya, I've tried several times to top out... I noticed that since I've changed my tires too 245/40/18, having that extra weight/tread doesn't allow me to ever really pass 145 unless I'm going downhill (although I haven't tried that)...

edit: I'm NA

BoosTED

iTrader: (2)

That is just wrong to have that listed in your Garage...

Cody Red

i've been at 155 completely stock. I was on the way to install my RB race exhaust and sr highflow cat But I wonder how fast, and what top speed there'd be with a Mazsport turbo.

-Cody

silverwolf

+1 for bad listing in sig.
bandwagon:
4 years
silver
YOU!!

lookingglass

This is a quote from RP a few pages back.

I have a question about this formula if someone can answer. This is supposed to tell you what wheel hp you need to achieve a given speed. To me, it seems like you would want to compute the wheel torque needed and not wheel horsepower since torque is your limiting factor.

As I understand it, torque is what governs your rate of acceleration and also your highest possible speed and horsepower is basically an expression of torque and rpms, or, how rapidly you can apply torque to your wheels.

So my question is. How would this formula work for a vehicle that has an engine with relatively low hp but very high torque?

Also, I'm intruiged by the math behind it, if someone could point me to a breakdown of that formula that would be terrific as well.

Cheers,
-Chuck

Richard Paul

iTrader: (5)

Torque is pressure it doesn't give you over what time or speed. thus:

HP=tq x rpm over 5252

That gives you both force over a period of time.
The use of the word "torque" is abused, people say it's a "torquer" or has alor of tq. The are related, locked together, can't have one without the other.
If I gave you tq to the wheels what would give you the distance over time to convert to MP-hour. You need distance and time.
You can go the mile with a lot less HP but how long did it take?

If your tq is at low rpm you must convert it to hp at the wheels with gearing.
Note that this year at Bonniville some huge desiel went over 300 mph. Now I don't know the numbers but you can bet it turned slow compared to gas engines. It converted it's tq to speed by running a very high gear, close to 1:1 or ? you get the idea.

We do the same thing in our car by providing lower gears before getting to high gear. This gives us more Tq at lower speeds so we can accelerate. Whatever the tq is coming out the flywheel muliply it by the gear ratio and that, less losses is the tq at the wheels.

I'm not the best teacher, so you have to think a little more then you would have to with someone who comunicates better. Really, if I could do that I'd go teach at some university and enjoy looking at coeds all day. Girls take engineering these days, they didn't back when I was in school.

BTW, the 146,600 is a constant worked out so you don't have to go through all the equations nessasary to find air resistance. The same goes for the CD, but it is more valuable yet, as you can't find the resistance of a given shape just using math. Having said that I know someone will show me a program that will give you a close guess. If they have those things I've never worked with it. I guess I can ask my son who is an engineer at Boeing. I just might do that, it would be nice to know.

lookingglass

Richard,

Thanks for the reply. If I had been thinking more clearly it would have occurred to me that if you had a hypothetical engine in the rx-8 for example, that developed 150hp and 500ft/lbs of torque at the flywheel the equation assumes that it would be geared to achieve the speed specified and hence would have a much higher hp at the wheels than at the flywheel, making the equation accurate.

I think I just stuck on a fragment of info I saw once where torque was expressed as G's of acceleration and I couldn't figure out how a low hp high torque engine was going to develop high enough hp to make the math work while obviously possessing the twisting force necessary to drive the vehicle to a desired speed. :D

Cheers,
-Chuck

Btw, just to add my 2 cents, your shifter has been awesome.