anewconvert

iTrader: (1)

did you see any improvement over the stock tune? Or was it just done for the sake of doing something different?


BC

rotarygod

iTrader: (1)

I mostly did it for the hell of it. I had the ecu and my friend had the car. We did notice that I could get it to idle smoother than the stock ecu did at the time. It has since been reflashed and is much better. I did learn that on that car, with only fuel control you don't gain anything useful. The stock ecu actually fights you. I never got a check engine light though. The stock ecu still controlled the drive by wire and the ignition. I just took the fuel injectors out of the picture. Anytime I tried to change the fuel mixture, the stock ecu would try to compensate by altering the timing. It was pretty frustrating. Fuel only ecu mods are pretty worthless on that car. If I had timing control at the time, it would have been much better. Of course I probably would have gotten a check engine light then too. For the most part it worked much as the Interceptor X does on that car. It was an experiment just for the sake of trying it to learn about what it will do. I do that alot on cars.

anewconvert

iTrader: (1)

I remember reading in a thread over at rx8club (under this same screen name) but couldnt remember if you got anything out of it. I knid of figured that the stock ECU would play games with you. Every year that passes car computers get more and more controling of the vehicle. The MS3 is a prime example. With the direct injectiong an torque management its going to be a hell of a bitch to get to function properly.


btw its awesome that someone else is on at 3:30 in the morning.


BC

rotarygod

iTrader: (1)

It's an hour earlier here. I'll be gone by 3:30! I moderate the 8 forum and watch it at night for spam. They always come out at night!

NZConvertible

This is most definably wrong. I have a dash-mounted digital injector duty cycle display reading off the front primary injector, and the DC goes above 40% both before and after the secondaries come on. Above the transition all four injectors are fired at the same pulsewidth.

Aaron Cake

iTrader: (1)

HP = (Torque*RPM) / 5252

The more torque an engine makes the more HP it makes.

Torque is not something that disappears at 3000 RPM and then it's horsepower from then on. An engine is built to maximize torque at all points to maximize the power it produces. Any time you make more torque, you make more HP and end up with a faster car. Cars that have very low amounts of low end torque (ie. S2000) yet make high horsepower figures are slow and a pain to drive.

This is really basic stuff that anyone modifying engines needs to know.

That's what I'm assuming. I can't speak for others but I bridged the aux ports only because I had originally planned to make them valve actuated. I gave up on that after reading about a few others that tried the same thing and received very poor results.

If I was to do it again I would continue the bridge down to a proper half-bridge. Though I am happy with the result of the aux bridge.

The long and sort of it is that it doesn't seem to help. From what I've read by those who have tried aux bridges with actuators, most would never do so again. Apparently the "maintain the low end while increasing the high end" does not work because the stock intake tuning interferes too much.

What people also forget is that you still get exhaust overlap even if the port is closed. This happens through the eyebrow port. Probably a lot less with the actuator in place then not, but it still happens. To what effect I don't know because I've never done it.

rotarygod

iTrader: (1)

I wonder how I'm confused on that one? I saw that piece of info years ago. Check to see if the primaries fall off at that point as the secondaries come online at all to help with the transition point. Does the duty cycle remain constant on them and the secondaries just add to them then? I really always understood it as the primaries falling off at least somewhat initially when the secondaries came on. Could it be that the primaries only fall off as much as necessary to arive at the same duty cycle as the secondaries? Obviously if they are firing and remain constant when the secondaries kick in, the secondaries wouldn't have the same duty cycle so it would sem they have to go down somewhat.

iceblue

No, I can manipulate TQ all over the place I can give you 500000ftlbs of tq on your rx7. You wont be any faster then the guy with 200 at all. First gear might be a little quick but you won’t be going any where in a hurry. HP is the determination of speed plain and simple TQ is worthless. Tq alows you to have the force to move something but the something does not move without HP. TQ does absolutly and compleatly nothing by itself at all reguardless of how much you have.

Yes on
Horsepower = (Torque X RPM) / 5252

Torque = (Horsepower X 5252) / RPM

RPM = (Horsepower X 5252) / Torque

TQ is always grater below 5252rpm and HP is always grater above 5252

Learn more from paul yaw here
http://www.yawpower.com/tqvshp.html

iceblue

Are you sure about that? Are you realy sure? Would you bet your life on this statement?

Your accounts aproved now I just did them.

sonorous7

wow this thread has been really informative, thanks guys!

After reading rotarygod's post about exhaust velocity, it all makes sense now. Not to hijack but I'm little worried about the setup that came on my car (s4 n/a) when I bought it. It's very mild compared to what you all are talking about, basically stock really (stock ports, stock intake, stock exhaust manifold but I have the 2.5" Bonez superflo system with highflow cat and Apexi Dual N1's). I know the catback's a little big (2.5-2.75-3.3"). Do you think it's causing the power loss you guys are talking about due to low velocity or is it okay b/c I still have the stock manifold and 2.5" cat?

Roen

iTrader: (2)

right you can maniuplate wtq with gearing and what not, but an engine will only produce a certain amount of flywheel tq given a set redline, a set port and a set max hp. The point I was trying to make before is that given two engines with similar hp outputs, you'd go for the one with more tq, because that indicates more power under the curve. I'm also of the opinion that tq is a function of hp, as opposed to the other way around and we all know power does work, not force.

rotarygod

iTrader: (1)

sonorous7: I personally like a 2.5" pipe after the header collector. If you have a stock exhaust manifold, you only have a 2" out if it anyways. That's all it is. Your pipes just get larger and larger from there on out. Get a header on it with a 2.5" exhaust and you'll be good to go. At the very least start with the header but you'll probably find that those mufflers don't work so well with it. It'll be loud! It is OK to taper an exhaust larger as the pipe gets farther back. This does add some tuning benefit as "theoretically" (that's the key word) it is widening the powerband at the expense of ultimate peak power. I'd personally rather just keep it simple and keep a constant area pipe on the car. When you get into pipe expansions, there is a lot of trial and error to get it to do exactly what you want it to do as the location of the taper and the rate of expansion really changes things. It's not to say your exhaust is crap and will necessarily hold you back though so don't think I am saying that.

At one point my old 2nd gen had a header on it that I had cut apart to see what did and didn't work. I first had a 2.5" pipe at the collector and from there on out the back. After the Y-pipe the area can increase BTW and having a Y-pipe does not hurt your flow at all as some have claimed. Anyways it made good power like this. I then modified the header so it had a 3" collector and exhaust out the back. It fell on it's face. I did start to get some power back near redline but everywhere below this sucked. That's where I drive! I changed it back to the 2.5" pipe and got all of my power back. It's not to say that ultimately the 3" pipe didn't make more peak power. From a usable standpoint for a street car, it didn't on mine. Maybe a bridgeport or peripheral port would though as the more overlap you get into on an engine, the more critical a proper exhaust system eally is. There are certain systems that work fine on stock or streetports that would fall flat on their face on bridge and peripheral port engines. They are much more sensitive. Of course I'd almost certainly have seen a gain with the 3" if I were to raise the redline but my gearing isn't set up for that so the 2.5" is perfect for the street. Bigger isn't always better. On that car I have also tried true duals, stock exhaust manifold with "downpipes", short primary systems, long primary systems, 2.5" collectors, and 3" collectors. I had a lot of fun experimenting on that car. I have also tried all of these setups on both stock and streetported engines as at one time I had 2 RX-7's at once. It's neat to actually see firsthand how a change affects things.

Roen

iTrader: (2)

Rotarygod, you ever try a 2.75" pipe or anything in between 2.5" or 3"?

rotarygod

iTrader: (1)

Nope that I didn't. The results would obviously be somewhere in between them though! I had measured the smallest point in the exhaust system on my car and found it to be a 2.5" (when I had a 2.5" collector) so that's what I went with. You need to be careful to check what you are using. I have a Bonez cat lying around that has a 2.5" inlet and outlet. It was welded from the inside of the flanges though so it's smallest points were actually 2.25". I ground them out and tack welded the flanges on the outside just to be safe.

My overall favorite system on both stock and streetports is the long primary with the pipes collecting near the back of the car to a 2.5" collector. It had a very nice wide powerband. This was easy to do on my 1st gen. If you wanted to do it on a 2nd gen, you would need to use a muffler on one side only though.

iceblue

Still does not make it faster in any way. Read pauls article I have other if you wish them as well. The TQ is always grater below 5252 and always less above 5252. Look at some high hp 13bs and you will see the tq curve just starts to go flat around 5252 and the HP will rocket up. If the stronger curve in the TQ made any difference you wouldn’t see the hp still rising in a peak manor while the tq stays flat.

Roen

iTrader: (2)

so you're telling me that a car with 160 tq @ 5000 rpm and 200 hp @ 8000 rpm is just as fast as a car with 170 tq @ 5000 rpm and 200 hp @ 8000 rpm? Remember, you can read tq as how power is delivered, or change in power so it's not really worthless as you say it is. tq is worthless without hp, that's a fact illustrated by the lever arm example. hp isn't as worthless, as you'll still have an idea of how fast you'll move. But if you're comparing similar things with both tq and hp ratings working together, tq is not as worthless as some may think.

I'll leave you with a formula from Paul Yaw's page to contemplate.

TORQUE AT THE REAR WHEELS = (ENGINE TORQUE X TRANSMISSION GEAR RATIO X RING AND PINION RATIO)

ACCELERATIVE THRUST = (TORQUE AT THE REAR WHEELS / TIRE RADIUS IN FT.)

RATE OF ACCELERATION = (ACCELERATIVE THRUST / TOTAL VEHICLE WEIGHT.)

If all factors are the same except for engine tq, engine tq is the determining factor for acceleration.

sonorous7

Thanks for the advice ; the part about the tapering is interesting. I keep reading different things though. For instance, I've read that I won't gain anything from a header since I have stock ports and the stock intake system? Also, after some more researching, should the big muffler matter if the piping before it is 2.75"? Hopefully I'm only losing a little low-mid power. It seems that if the stock manifold's only 2" then nothing after it should even matter but I guess that's not how it works.. thanks again

84stock

iTrader: (5)

Yep, every pretty girl has a fat friend and an ugly friend. Too bad your buddy and his pretty grilfriend bought you soooo many drinks before introducing you to her friends. Next time bring some change for the little machine in the bathroom before going home.........PS, what's worse, a painful **** or a bad memory.........LOL

rotarygod

iTrader: (1)

A header is most definitely a power improvement over the stock exhaust manifold. It's extremely noticable. Someone here dyno'd a car with a stock manifold and a header and picked up a little over 10 hp with one. That's at full throttle though. The bad thing about a dyno is that it does not tell you how power is affected through every other load range. A header really helps with part throttle levels. Don't judge potential by a full throttle dyno run. They are good tuning devices and are good to get bragging rights with but unless you use one at multiple throttle levels (like a good tuner would), the info you get is pretty limited. Remember that a header helps scavenge. It helps pull gasses along. The slower the gas flow is, the more important this becomes. A stock manifold does a terrible job of this.

The short "primaries" of the stock manifold are somewhere around 2" or so long before dumping into the open common area. This length just so happens to tune up near the 7000 rpm mark or near it and this is evidence by the fact that the stock engine makes peak power at 6500 rpms. This also explains why a full throttle run with a header only yields so much more power. The stock manifold is tuned near there! There are other ways to tune to a certain rpm. It's not to say that a 2" primary is always going to tune an engine to this spot and you can't tune higher. It doesn't work like that.

Tuning benefits come from pressure wave lengths. Waves have troughs and valleys and there are multiple troughs and valleys since there are multiple waves in the system at any one time. An engine that has a runner that tunes to a certain rpm at X length also tunes at the harmonics of those lengths which corresponds to different rpms. It's possible to have a longer that 2" pipe tune to a higher rpm. It just so happens one of the waves falls at the right point with this length in the stock manifold. It starts to get a bit confusing (if I haven't already lost you) and sounds contradictory. You need to realize that with each reflection farther out (1st order is the first wave, 2nd order is the second wave, etc...), the effect gets lower and lower. Each wave bounces back and forth over the entire length of the system multiple times, not just once. There are lots of waves to time to get a benefit from.

iceblue

Read down further you stopped short to make your point sound valid. All you did was determine the speed of the vehicle you forgot time. Time is the most important factor in going somewhere again hp not tq.

If I give you 300hp and me 600hp and you 600ftlbs and me 300ftlbs I will be exactly double the speed of you with the same gear ratio that will output the same amount of tq leverage to the wheels. Your tq curve is much stronger but is exactly half the speed of mine. TQ is irrelevant in the determination factor of speed/time understand that.

Roen

iTrader: (2)

Before you start spouting examples that we're already aware of, i feel that i need to state my point of view. Tq without Hp is worthless. Hp without Tq still gives some sort of semblance of an idea how fast you'll go. However, without Tq figures and a set gear ratio, you have no idea how that Hp is being delivered. Hp, Tq and Gear Ratios combined give you an exact picture on how the car moves.

We're not talking about different hp's, we're talking about the same hp with 2 different tq's. We've already covered tq vs. hp.

My point is, for all else being equal, gear ratios, hp, redline, tq peak, hp peak, you pick the engine that makes more tq. You realize, with equal hp and a higher tq, (160 ft-lbs @ 5000 rpm vs. 170 ft. lbs @ 5000 rpm) at the crossover point (5252 rpm), the car with 170 tq has more power all the way until the 160 ft-lbs engine makes max hp. Given that we're talking about NA cars with relatively flat torque curves, there's no doubt in my mind that because of the higher tq figure, the 170 ft-lbs engine makes more hp in the powerband than the 160 ft-lbs engine. Time conditions are both cars start from rest, or from a roll at equal speed. I don't really see how time matters as the cars have the same hp peak. Because tq is a function of hp, it's not irrelevant since it's based on the figure that you stress so much.

If you've taken calculus, you can do a simple partial derivative of tq on hp. you can find the relationship that way. Variables that have a relationship cannot be irrelevant, since one can explain the other.

iceblue

If you ran a steeper gear to achive more tq and same hp output you would be quicker not faster. This is because you lowerd the ENTIRE band and peaked the HP up and tightend the time between gears not because you increased tq.

TQ by itself does nothing by adding more TQ you still didnt do anything. What you did achive is the ability to pull more weight but not faster.

iceblue

...............

Roen

iTrader: (2)

If you can't see how having more tq means having more hp over a range of rpm's, then i have no idea what I can say to you. If I have the same hp peak, and a tq peak at 5252 of x and y, where x is a little bit bigger than y, which car produces more power at tq peak? Both cars are NA, implying flat tq curves, so which car produces more power over the curve? Both cars are geared the same. You honestly think both cars will accelerate the same?

iceblue

Here