rx7_ragtop

Stock is more like 110 to the wheels. I put 130 with my mods, 155 for a S4 is pretty awesome!

Brad

jon88se

the rest of the A/F band looks fine so I bet that 18:1 was partial throttle. Nice numbers...good power and the peace of mind of a healthy motor. The lack of torque data seems like a dyno fault, not anything to do with your car at all!! Do you have cats in your car?? no cats and a mid pipe is worth a nice gain on the NA..similar to a header install and simply improves the efficiency of the rest of the system. If you plan to tune a lot with the AFC, get a decent EGT gauge...

SPDST3R

Hmmm... ok now what is an EGT gauge?

RX7_ZRO

I love reading threads like this. I'm probably one of the few people who bother to read all the posts even though I'm not sure what about half of the numbers and abbreviations are for. LOL@myself

jon88se

EGT, exhaust gas temps...a good indicator of your air fuel ratio. Although the SAFC has an output for O2 sensor voltage, the stock O2 sensor is slow and not nearly as accurate as the one used in your dyno test. Together with an EGT gauge you'll have a better idea of how your engine is running and if your settings are safe. A fuel pump and injectors are only going to slow your NA down unless you swap in a turbo

BogusFile

Now all you need is a 300 shot of nitrous.

Manolis_D

iTrader: (2)

YOU NEED MORE FUEL!

ok, now that I have that out of the way...

Take a look at your dyno sheet and notice that you have two 'graphs' on it... the top one is horsepower (duh), and the bottom is Air: fuel ratio (AFR). Maximum power for your motor will be pretty much between 12.5:1 and 13:1. If you look at your graph, you'll see that before 60-65 mph you're running pretty LEAN (this means the # is HIGHER). You're running about 14:1 until like 47 mph. While on an NA this is probably not dangerous (it shouldn't detonate), it will make LESS TORQUE. If you ADD fuel with the S-AFC until that # is like 12.5 or 13, then you will have more torque. That should take about 8-10% more fuel I think (just to get you started). Then, at 47 MPH, you go WAY lean -- almost 15:1. You can see that the HP curve has a big flat spot here -- your engine is losing a good bit of power just because of that lean spot! O2 sensors also have a bit of 'lag', which you can also see on the graph (the 15:1 registers slightly after the flat spot on the HP curve). Between 45 and 52 mph I'd say that you need to add between 13% and 15% more fuel to get to max power. Then add another 5-7% more fuel between 52 and 60 mph, and an other 3-5% fuel between 60 and 67 mph. If you do that, I'll bet that your car will pick up a LOT more low end - midrange torque, and it'lll become not only faster but much more fun to drive!

Try that and let us know how it goes! If you have any more questions or any questions on what I just said, please let me know!

Have fun
Manolis Dimotakis

SPDST3R

I have been waiting for someone to post this kind of explanation. Thanks man!!! But of course, the S-AFC can only be set thorugh RPM ranges. So how do I do this if my dyno sheet is only showing MPH?

Manolis_D

iTrader: (2)

NP I went through a lot of learning too, and it really pissed me off that I could never find that kind of explanation

Anyway... Do you remember what gear the car was dynoed in? If so, that would be useful! If not, I'll try to figure that out for you. Yours is an S4, so they stopped at 7000 rpm, right?

Lemme try to figure this out. let me know what gear you were in if you can remember!

SPDST3R

edit... oh well u got it figured out

Manolis_D

iTrader: (2)

OK, looking at that again, i'm guessing you were in 3rd gear, soo.....

I don't know exactly what the rpm ranges on the S-AFC are, but these are the ones you need to adjust (assuming the dyno was done properly, and the accelerator was 'floored' at 40 mph or so):

3300 (or 3000) - 3750: try adding 8-10% more

<this is the big one> 3750 - 4250: 13-15% more

4250 - 5000: 5-7% more

5000-5500: 3-5% more

Above 5500 the AFR looks to be dead on -- nice work

The important thing is that you get the 3750-4250 rpm range down to ~13:1. I don't know what the ranges on the S-AFC are, but if you can't do just that range, then I'd say it's probably worth making everything around that a bit too rich to compensate. Basically you are looking for the smoothest curve that hovers right below 13:1, and that should get you some smooth power. Once you get the car down into that range, try tweaking it a bit here and there to see if adding a little bit (a few percent) of fuel helps or hinders, and fine-tune that power curve

Manolis_D

iTrader: (2)

whoops, missed that
you sure it was 4th? Redline in 3rd is about 85 mph, which is why i assumed 3rd. If it was in 4th, then.... <i'll post this ina second...>

SPDST3R

the RPM rang increment on the S-AFC is 500.

SPDST3R

no, you're right, it has to be on 3rd because redline on my 4th gear is around 120MPH. Now you also taught me how to read RPM against MPH. This is so cool

Manolis_D

iTrader: (2)

OK, so then you'll probably want to do this:

3000 - 3500: 8-10% more

3500 - 4500: 13-15% more

4500 - 5000: 5-7% more

5000-5500: 3-5% more


That'll probably get it a little bit rich right at 4500 or so (55mph on the graph), but it's a lot better than running lean!

Like I said, I'm pretty damned sure that run was in 3rd gear, because redline in 3rd is ~85 miles per hour. If that was in 4th gear then he would have only revved it to 4500 or 5000 rpm... highly unlikely Of course, that's assuming the mph reading is right (which it should be)

Evil Aviator

Some dynos have different modes for print-outs. See if you can get the rpm's instead of speed next time. I find it hard to believe that a dyno can't give a torque reading, lol. Ask someone else who works there.

Anyway, you can convert the mph to rpm with:

RPM = (Speed mph * Rear Axle Ratio * Transmission Gear Ratio * 1056) / Rear Tire Circumference in inches

Also, you can pencil-in your own torque curve with:

Torque lbs-ft = (Horsepower * 5252) / RPM

BTW, since you have access to a dyno, why not tune for power instead of some AFR Holy Grail?

SPDST3R

What do you mean by this? BTW, thanks for the conversion formula.

Manolis_D

iTrader: (2)

He means basically what I said... Get everything close to what it 'should' be, and then make it richer / leaner until you hit the absolute maximum power level for each RPM 'range' (you want the most horsepower at any given point basically).

Wankel7

How can he add more... I didn't see any fuel mods?

James

SPDST3R

bump for that question ^

pp13bnos

iTrader: (1)

Different cars will make different hp at the same a/f ratio. Mine made peak hp all the way across the board at 14.25-1 a/f ratio. (I spent 4hrs with a wide band on a dyno doing this.) Something else that is also important is the place of the wide band sensor. If it was'nt stuck in pretty close to the engine, chances are it is'nt very accurate. It need to be placed in your 02 censor bung preferably.

I would try leaning it out from 55-65 mph a bit. Probably 5% or less. From 65 and up I would lean it out around 15-18%

Go for a test run, and tell me what feels faster. When you richen it up(Like Manolis says), or when you leaned it out. I got money on leaning it out. CJ

pp13bnos

iTrader: (1)

BTW. Lean it out in small increments...like 3-4% at a time. I realy look forward to your comments. CJ

SPDST3R

i'll probably stay with 13:1 to 13.5:1 for now. I don't want to overstress it without a guage. Now, I guess this is the time where you need an EGT right?

pp13bnos

iTrader: (1)

No, a egt will tell you exaust gas tempature. 1850f, is what you need to see under full throttle in the top on 3rd or 4th gear. If you have ever looked at buying a egt unit, you'll notice a decent one will cost you more than a dyno session. CJ

I spent $120 for a "dual sweep" gauge, and $60 per probe. BTW, you need two, to do it right. One for the front rotor, and one for the rear.

Evil Aviator

Exactly. I recommend trying richer first, and then see what Mr. Dyno says. Oh, and be sure to write down all your changes so you don't forget.

It all comes down to focus. Is your goal to gain more power, or to maintain a magical AFR that some internet geek told you is good? I know of one particular "tuner" who has blown up a customer's engine 4 times trying to chase an AFR, so I recommend tuning for power instead, LOL. Also, as far as credibility goes, I would trust the dyno a whole lot more than some of the responses you have gotten in this thread.

Isn't there an S-AFC involved here, or am I misreading the posts?
http://66.216.67.51/product.asp?0=208&1=245&3=251